RESUMO
To compare growth patterns and strength of weight- and non-weight-bearing bones longitudinally. Irrespective of sex and ethnicity, metacarpal growth was similar to that of the non-weight-bearing radius but differed from that of the weight-bearing tibia. Weight- and non-weight-bearing bones have different growth and strength patterns. INTRODUCTION: Functional loading modulates bone size and strength. METHODS: To compare growth patterns and strength of weight- and non-weight-bearing bones longitudinally, we performed manual radiogrammetry of the second metacarpal on hand-wrist radiographs and measured peripheral quantitative computed tomography images of the radius (65%) and tibia (38% and 65%), annually on 372 black and 152 white South African participants (ages 12-20 years). We aligned participants by age from peak metacarpal length velocity. We assessed bone width (BW, mm); cortical thickness (CT, mm); medullary width (MW, mm); stress-strain index (SSI, mm3); and muscle cross-sectional area (MCSA, mm2). RESULTS: From 12 to 20 years, the associations between metacarpal measures (BW, CT and SSI) and MCSA at the radius (males R2 = 0.33-0.45; females R2 = 0.12-0.20) were stronger than the tibia (males R2 = 0.01-0.11; females R2 = 0.007-0.04). In all groups, radial BW, CT and MW accrual rates were similar to those of the metacarpal, except in white females who had lower radial CT (0.04 mm/year) and greater radial MW (0.06 mm/year) accrual. In all groups, except for CT in white males, tibial BW and CT accrual rates were greater than at the metacarpal. Tibial MW (0.29-0.35 mm/year) increased significantly relative to metacarpal MW (- 0.07 to 0.06 mm/year) in males only. In all groups, except white females, SSI increased in each bone. CONCLUSION: Irrespective of sex and ethnicity, metacarpal growth was similar to that of the non-weight-bearing radius but differed from that of the weight-bearing tibia. The local and systemic factors influencing site-specific differences require further investigation. Graphical abstract.
Assuntos
Ossos Metacarpais/crescimento & desenvolvimento , Rádio (Anatomia)/crescimento & desenvolvimento , Tíbia/crescimento & desenvolvimento , Suporte de Carga/fisiologia , Adolescente , Envelhecimento/etnologia , Envelhecimento/fisiologia , Antropometria/métodos , População Negra/estatística & dados numéricos , Criança , Feminino , Humanos , Estudos Longitudinais , Masculino , Ossos Metacarpais/anatomia & histologia , Ossos Metacarpais/diagnóstico por imagem , Ossos Metacarpais/fisiologia , Radiografia , Rádio (Anatomia)/anatomia & histologia , Rádio (Anatomia)/diagnóstico por imagem , Rádio (Anatomia)/fisiologia , Caracteres Sexuais , Estresse Mecânico , Tíbia/anatomia & histologia , Tíbia/diagnóstico por imagem , Tíbia/fisiologia , Tomografia Computadorizada por Raios X/métodos , Adulto JovemRESUMO
This prospective study assessed whether metacarpal indices predict fracture risk in children and adolescents. Radiogrammetry was performed at the second metacarpal midshaft on annual hand-wrist radiographs of 359 South African (SA) children aged 10-17 years. Bone length, bone width, and medullary width were measured, and the following proxies for bone strength calculated: metacarpal index (MCI), bone mineral density (BMD), section modulus (SM), stress-strain index (SSI), and slenderness index (SLI). Height and weight were measured annually. Self-reported physical activity (PA) and fracture history were obtained at ages 15 years (for the preceding 12 months) and 17 years, respectively. At 17 years, 82 (23%) participants (black, 16%; white, 42%; p < 0.001) reported a previous fracture. None of the bone measures or indices were associated with fracture in black participants. In white females, after adjusting for PA, a 1 standard deviation (SD) greater SLI doubled the fracture risk [odds ratio (OR) 2.08; 95% confidence interval (CI) 1.08, 3.98]. In white males, a 1 SD greater BMD was associated with a 2.62-fold increase in fracture risk (OR 3.62; 95% CI 1.22, 10.75), whilst a 1 SD greater SM (OR 2.29; 95% CI 1.07, 4.89) and SSI (OR 2.23; 95% CI 1.11, 4.47) were associated with a more than twofold increase in fracture risk, after height, and PA adjustment. No single index consistently predicted fracture across the four groups possibly due to ethnic and sex differences in bone geometry, muscle mass, and skeletal loading. Metacarpal radiogrammetry did not reliably predict fracture in SA children.
Assuntos
Densidade Óssea/fisiologia , Fraturas Ósseas/metabolismo , Ossos Metacarpais/crescimento & desenvolvimento , Caracteres Sexuais , Absorciometria de Fóton/métodos , Adolescente , População Negra , Criança , Feminino , Humanos , Masculino , Estudos ProspectivosRESUMO
We found a positive relationship between bone density in Nigerian children with and without rickets and that of their mothers. After treatment, children with rickets had greater bone density than children without rickets, indicating that children genetically programmed to have greater bone density may have a higher risk of rickets. INTRODUCTION: To determine the relationship between bone density in children with and without rickets and that of their mothers METHODS: Using an unmatched case-control design, forearm areal bone mineral density (aBMD) was measured in 52 and 135 Nigerian children with and without rickets and their mothers, respectively. We performed multivariate linear regression analyses to assess the relationship between maternal and child aBMD Z-scores. RESULTS: Forearm aBMD Z-scores in children were associated with maternal aBMD Z-scores at metaphyseal (effect estimate 0.23; 95% CI 0.08 to 0.37) and diaphyseal (effect estimate 0.16; 0.01 to 0.30) sites, after adjustment for rickets in the child, child's age and sex, height-for-age Z-score, and weight-for-age Z-score. In the adjusted model, rickets was inversely associated with child's aBMD Z-score at the diaphyseal site only (- 0.45, - 0.65 to - 0.24). The positive relationship between maternal and child aBMD Z-scores was marginally greater in children with rickets (slope 0.56, r = 0.47) than without rickets (slope 0.19, r = 0.20) at the diaphyseal site only (P = 0.06 for interaction) but not at the metaphyseal site (slopes 0.35 and 0.30, respectively, P = 0.48). After treatment with calcium for 6 months, metaphyseal aBMD Z-scores were greater in children with treated rickets (effect estimate 0.26; 95% CI 0.02 to 0.49) than in those without rickets. CONCLUSION: In Nigerian children with and without rickets, forearm aBMD Z-scores were positively associated with maternal aBMD Z-scores. Active rickets in the child marginally modified the relationship at the diaphyseal site only. After treatment, children with rickets had greater metaphyseal aBMD Z-scores than children without rickets.
Assuntos
Densidade Óssea/genética , Raquitismo/genética , Absorciometria de Fóton , Adulto , Antropometria/métodos , Densidade Óssea/fisiologia , Cálcio/uso terapêutico , Estudos de Casos e Controles , Criança , Fenômenos Fisiológicos da Nutrição Infantil/fisiologia , Pré-Escolar , Diáfises/fisiopatologia , Feminino , Humanos , Lactente , Masculino , Mães , Rádio (Anatomia)/fisiologia , Rádio (Anatomia)/fisiopatologia , Raquitismo/tratamento farmacológico , Raquitismo/fisiopatologia , Ulna/fisiologia , Ulna/fisiopatologiaRESUMO
BACKGROUND: Early postnatal rapid 'catch-up' weight gain has been consistently associated with subsequent higher obesity risk and earlier pubertal development. In many low- and middle-income countries, infancy catch-up weight gain is transient and often followed by growth faltering. We explored the hypothesis that even transient catch-up weight gain during infancy is associated with later obesity risk and earlier puberty. METHODS: A total of 2352 (1151 male, 1201 female) black South African children in the birth to twenty prospective birth cohort study (Johannesburg-Soweto) underwent serial measurements of body size and composition from birth to 18 years of age. At the age of 18 years, whole-body fat mass and fat-free mass were determined using dual-energy X-ray absorptiometry. Pubertal development was assessed by the research team between ages 9 and 10 years, and it was recorded annually from the age of 11 years using a validated self-assessment protocol. RESULTS: Catch-up weight gain from birth to the age of 1 year, despite being followed by growth faltering between ages 1 and 2 years, was associated with greater mid-upper arm circumference (P=0.04) and skinfold thickness (P=0.048) at 8 years of age, and with higher weight (P<0.001) and body mass index (P=0.001) at 18 years of age after adjustment for sex, age, smoking during pregnancy, birth order, gestational age, formula-milk feeding and household socio-economic status. Infancy catch-up weight gain was also associated with younger age at menarche in girls (P<0.001). This association persisted after adjustment for smoking during pregnancy, birth order, gestational age, formula-milk feeding and household socio-economic status (P=0.005). CONCLUSION: Transient catch-up weight gain from birth to the age of 1 year among children born in a low-income area of South Africa was associated with earlier menarche and greater adiposity in early adulthood. This observation suggests that modifiable determinants of rapid infancy weight gain may be targeted in order to prevent later obesity and consequences of earlier puberty in girls.
Assuntos
Adiposidade , Peso ao Nascer , Menarca , Aumento de Peso , Absorciometria de Fóton , Adiposidade/fisiologia , Adolescente , Fatores Etários , Peso ao Nascer/fisiologia , Índice de Massa Corporal , Criança , Pré-Escolar , Feminino , Humanos , Lactente , Masculino , Menarca/fisiologia , Estudos Prospectivos , Fatores de Risco , Dobras Cutâneas , África do Sul/epidemiologia , Aumento de Peso/fisiologiaRESUMO
UNLABELLED: The associations of fracture prevalence and bone mass in adolescents with maternal fracture history and bone mass have not been investigated previously in South Africa. Maternal bone mass has a significant inverse association with their adolescents' fracture rates and bone mass across all ethnic groups. INTRODUCTION: Differences in fracture rates and bone mass between families and individuals of different ethnic origins may be due to differing lifestyles and/or genetic backgrounds. This study aimed to assess associations of fracture prevalence and bone mass in adolescents with maternal fracture history and bone mass, and sibling fracture history. METHODS: Data from 1,389 adolescent-biological mother pairs from the Birth to Twenty longitudinal study were obtained. Questionnaires were completed on adolescent fractures until 17/18 years of age and on sibling fractures. Biological mothers completed questionnaires on their own fractures prior to the age of 18 years. Anthropometric and bone mass data on adolescent-biological mother pairs were collected. RESULTS: An adolescent's risk of lifetime fracture decreased with increasing maternal lumbar spine (LS) bone mineral content (BMC; 24 % reduction in fracture risk for every unit increase in maternal LS BMC Z-score) and increased if they were white, male, or had a sibling with a history of fracture. Adolescent height, weight, male gender, maternal bone area and BMC, and white ethnicity were positive predictors of adolescent bone mass. White adolescents and their mothers had a higher fracture prevalence (adolescents 42 %, mothers 31 %) compared to the black (adolescents 20 %, mothers 6 %) and mixed ancestry (adolescents 20 %, mothers 16 %) groups. CONCLUSION: Maternal bone mass has a significant inverse association with their adolescent off-springs' fracture risk and bone mass. Furthermore, there is a strong familial component in fracture patterns among South African adolescents and their siblings.
Assuntos
Densidade Óssea/genética , Fraturas Ósseas/genética , Adolescente , Adulto , Antropometria/métodos , População Negra/estatística & dados numéricos , Peso Corporal/fisiologia , Estudos de Coortes , Feminino , Fraturas Ósseas/etnologia , Humanos , Recém-Nascido , Estudos Longitudinais , Vértebras Lombares/fisiologia , Masculino , Pessoa de Meia-Idade , Mães/estatística & dados numéricos , Puberdade/etnologia , Puberdade/fisiologia , África do Sul/epidemiologia , População Branca/estatística & dados numéricosRESUMO
OBJECTIVES: To compare growth velocity of two African child cohorts and examine the relationship between postnatal growth velocity in infancy/early childhood and the risk of overweight/stunting in early adolescence. METHODS: The study used data from two child cohorts from urban (Birth to Twenty Cohort, South Africa) and rural (Lungwena Child Survival Study, Malawi) African settings. Mixed effect modelling was used to derive growth and peak growth velocities. T-tests were used to compare growth parameters and velocities between the two cohorts. Linear and logistic regression models were used to determine the relationship between growth velocity and early adolescent (ages 9-11 years) body mass index and odds of being overweight. RESULTS: Children in the BH cohort were significantly taller and heavier than those in the Lungwena cohort, and exhibited faster weight and height growth velocity especially in the first year of life (P < 0.05). No significant association was shown between baseline weight (αw ) and overweight in early adolescence (OR = 1.25, CI = 0.67, 2.34). The weight growth velocity parameter ßw was highly associated with odds of being overweight. Association between overweight in adolescence and weight velocity was stronger in infancy than in early childhood (OR at 3 months = 4.80, CI = 2.49, 9.26; OR at 5 years = 2.39, CI = 1.65, 3.47). CONCLUSION: High weight and height growth velocity in infancy, independent of size at birth, is highly associated with overweight in early adolescence. However, the long term effects of rapid growth in infancy may be dependent on a particular population's socio-economic status and level of urbanization.
Assuntos
Estatura , Peso Corporal , Sobrepeso/epidemiologia , Adolescente , Índice de Massa Corporal , Criança , Pré-Escolar , Estudos de Coortes , Feminino , Humanos , Lactente , Recém-Nascido , Masculino , Sobrepeso/etiologia , Gravidez , Análise de Regressão , Risco , População Rural , Classe Social , África do Sul/epidemiologia , População UrbanaRESUMO
UNLABELLED: This is the first report examining vitamin D status and bone mass in African women with HIV infection using dual-energy X-ray absorptiometry (DXA) with an appropriate HIV-negative control group. Unlike previous publications, it demonstrates no difference in bone mineral density (BMD) or vitamin D status in HIV-positive patients, at different disease stages, vs. HIV-negative subjects. INTRODUCTION: Low bone mass and poor vitamin D status have been reported among HIV-positive patients; suggesting HIV or its treatment may increase the risk of osteoporosis, a particular concern for women in countries with high HIV prevalence such as South Africa. We describe bone mass and vitamin D status in urban premenopausal South African women, who were HIV positive but not on antiretroviral therapy (ARV). METHODS: This study is a cross-sectional measurement of BMD and body composition by DXA and vitamin D status by serum 25-hydroxyvitamin D (25(OH)D) concentration. Subjects were recruited into three groups: HIV negative (n = 98) and HIV positive with preserved CD4 cell count (non-ARV; n = 74) or low CD4 cell counts prior to ARV initiation (pre-ARV; n = 75). RESULTS: The mean (standard deviation (SD)) age of women was 32.1 (7.2) years. Mean CD4 (SD) counts (×10(6)/l) were 412 (91) and 161 (69) in non-ARV and pre-ARV groups (p < 0.0001). Pre-ARV women were significantly lighter and had lower mean BMI than the other two groups (p < 0.002). The pre-ARV group also had significantly less fat and lean mass compared with non-ARV and HIV-negative subjects (p ≤ 0.05). After full adjustment, there were no significant differences in BMD at any site (p > 0.05) between the groups, nor was vitamin D status significantly different between groups (p > 0.05); the mean (SD) cohort 25(OH)D being 60 (18) nmol/l. CONCLUSION: Contrary to previous studies, these HIV-positive women did not have lower BMD or 25(OH)D concentrations than HIV-negative controls, despite the pre-ARV group being lighter with lower BMI.
Assuntos
Composição Corporal/fisiologia , Densidade Óssea/fisiologia , Infecções por HIV/fisiopatologia , Vitamina D/análogos & derivados , Absorciometria de Fóton , Adulto , Antropometria/métodos , Fármacos Anti-HIV/uso terapêutico , Contagem de Linfócito CD4 , Estudos Transversais , Feminino , Colo do Fêmur/fisiopatologia , Infecções por HIV/sangue , Infecções por HIV/tratamento farmacológico , Infecções por HIV/imunologia , Articulação do Quadril/fisiopatologia , Humanos , Vértebras Lombares/fisiopatologia , Pré-Menopausa/fisiologia , Saúde da População Urbana/estatística & dados numéricos , Vitamina D/sangue , Adulto JovemRESUMO
Genetic factors are thought to maintain bone mass in socioeconomically disadvantaged black South Africans. We compared bone mass between environmentally disadvantaged black and advantaged white children and their parents, after determining the most appropriate method by which to correct bone mineral content (BMC) for size. We collected data from 419 healthy black and white children of mean age 10.6 years (range 10.0-10.9), 406 biological mothers, and 100 biological fathers. Whole-body, femoral neck, lumbar spine, and mid- and distal one-third of radius bone area (BA) and BMC were measured by dual-energy X-ray absorptiometry. Power coefficients (PCs) were calculated from the linear-regression analyses of ln(BMC) on ln(BA) and used to correct site-specific BMC for bone size differences. Heritability (½h(2), %) by maternal and paternal descent was estimated by regressing children's Z scores on parents' Z scores. Correcting BMC for height, weight, and BA(PC) accounted for the greatest variance of BMC at all skeletal sites. In so doing, BMC in blacks was up to 2.6 times greater at the femoral neck and lumbar spine. Maternal and paternal heritability was estimated to be ~30% in both black and white subjects. These results may in part explain the lower prevalence of fragility fractures at the hip in black South African children when compared to whites. Heritability was comparable between environmentally disadvantaged black and advantaged white South African children and similar to that reported for Caucasians in other parts of the world.
Assuntos
Densidade Óssea , Osso e Ossos/patologia , Puberdade Precoce/patologia , Absorciometria de Fóton , Antropometria , População Negra , Osso e Ossos/diagnóstico por imagem , Criança , Estudos de Coortes , Feminino , Colo do Fêmur , Humanos , Vértebras Lombares/patologia , Masculino , África do Sul , População BrancaRESUMO
UNLABELLED: Fracture rates were compared in children of different ethnic backgrounds from Johannesburg, South Africa. More white children fracture than black and mixed ancestry children. Reasons for this may be due to greater sports participation by whites and genetic protective factors in blacks. This has to be further investigated. INTRODUCTION: Fracture rates in childhood are as high as those in the elderly. Recent research has been undertaken to understand the reasons for this, but there is little information available on ethnic differences in childhood fracture rates. METHODS: Using the birth to twenty longitudinal cohort of children, we retrospectively obtained information on fractures and their sites from birth to 14.9 years of age on 2031 participants. The ethnic breakdown of the children was black (B) 78%, white (W) 9%, mixed ancestry (MA) 10.5% and Indian (I) 1.5%. RESULTS: Four hundred and forty-one (22%) children had sustained a fracture one or more times during their lifetime (males 27.5% and females 16.3%; p < 0.001). The percentage of children fracturing differed between the ethnic groups (W 41.5%, B 19%, MA 21%, I 30%; p < 0.001). Of the 441 children reporting fractures, 89(20%) sustained multiple fractures. The most common site of fracture was the upper limb (57%). CONCLUSION: More white children fracture than black and mixed ancestry children. This is the first study to show ethnic differences in fracture rates among children. The reasons for these differences have to be further elucidated. Greater sports participation by whites and genetic protective factors in blacks may be contributing factors.
Assuntos
Etnicidade , Fraturas Ósseas/epidemiologia , População Urbana , Adolescente , Adulto , População Negra , Criança , Pré-Escolar , Estudos de Coortes , Feminino , Fraturas Ósseas/etnologia , Humanos , Incidência , Lactente , Recém-Nascido , Masculino , Traumatismo Múltiplo/epidemiologia , África do Sul/epidemiologia , População Branca , Adulto JovemRESUMO
This study reports on ethnic differences in bone mass before and after adjusting for differences in body size and bone area (BA). Lumbar spine (LSBMC), proximal femur (PFBMC) and femoral neck (FNBMC) bone mineral contents were measured in black ('black'; n = 263) and white ('white'; n = 73) children from Johannesburg and children of mixed ancestral origin ('mixed'; n = 64) from Cape Town, South Africa. Geometric estimates and the power coefficient from the regression analyses of BMC on BA were calculated. After adjusting for age, weight, and height, LSBMC in girls and FNBMC in girls and boys were greatest in mixed, followed by black and then white, groups. Mixed boys and girls also had greater PFBMC than their black and white peers, but only in the boys was PFBMC greater in the black than the white groups. When including BA in the adjustment, differences remained at the FN in boys and girls, and the LS and PF in girls, but disappeared at the PF in mixed and black boys. The difference in LSBMC between mixed and black boys became significant after adjustment for age, weight, height, and BA. Geometric estimates at the femoral neck were greater in the mixed group. Power coefficients were greater in the white group, suggesting differences in shape or bone distribution. In conclusion, this study suggests that, in addition to differences in BMC, differences in bone strength and geometry are present which might confer advantages to the bone of mixed-ancestry children.
Assuntos
População Negra/etnologia , Densidade Óssea/fisiologia , Colo do Fêmur/fisiologia , Fêmur/fisiologia , Vértebras Lombares/fisiologia , População Branca/etnologia , Absorciometria de Fóton , Composição Corporal , Tamanho Corporal , Criança , Feminino , Humanos , Masculino , Caracteres Sexuais , África do SulRESUMO
BACKGROUND: Vitamin D deficiency (VDD) in pregnant women has been associated with adverse pregnancy and neonatal outcomes. 25-hydroxyvitamin D (25(OH)D) levels are affected by numerous factors, including vitamin D intake, skin pigmentation, latitude and season of the year; they therefore vary by race and country. Vitamin D status in pregnant women and their offspring in South Africa (SA) is not well established. OBJECTIVES: To assess vitamin D status by measuring serum 25(OH)D in pregnant black SA women and their offspring in Johannesburg (latitude 26°S) and to assess whether vitamin D status is affected by maternal HIV infection. METHODS: We prospectively enrolled pregnant women and their healthy neonates, and measured 25(OH)D in maternal and cord blood at delivery. Pregnant women were stratified by their HIV status. Predictors of maternal and neonatal VDD (levels <30 nmol/L) were assessed using multiple logistic regression analysis. RESULTS: A total of 291 pregnant women and their healthy neonates were enrolled over a 21-month period. Mean (standard deviation) maternal and cord blood 25(OH)D levels were 57.0 (29.7) and 41.9 (21.0) nmol/L and the prevalence of VDD was 15.9% and 32.8%, respectively. On average, concentrations of 25(OH)D in cord blood were ~80% of those in the mother. There was no association between cord 25(OH)D and gestational age, but levels were associated with birth weight (p<0.001). There were no differences in maternal or cord blood 25(OH)D levels between those HIV-infected or uninfected. The predictor of VDD in mothers was giving birth in winter (odds ratio (OR) 2.87, 95% confidence interval (CI) 1.47 - 5.61), and in neonates the predictors were maternal age (OR 16.5, 95% CI 1.82 - 149), being born in winter (OR 3.68, 95% CI 2.05 - 6.61), being born by caesarean section (OR 4.92, 95% CI 1.56 - 15.57) and being of low birth weight (OR 1.99, 95% CI 1.13 - 3.50). CONCLUSIONS: Among black SA women delivering in Johannesburg, about one in six mothers and one in three neonates have 25(OH)D levels indicative of VDD. Maternal HIV status appears not to affect levels of 25(OH)D in either the mother or her neonate. Research on the effects of VDD on the outcomes of pregnancy and the best methods to combat the high prevalence of VDD in women of childbearing age in the SA context is required.
Assuntos
População Negra/estatística & dados numéricos , Infecções por HIV/epidemiologia , Estado Nutricional , Complicações na Gravidez/epidemiologia , Deficiência de Vitamina D/epidemiologia , Adulto , Peso ao Nascer , Cesárea/estatística & dados numéricos , Estudos de Coortes , Feminino , Sangue Fetal/química , Humanos , Recém-Nascido , Gravidez , Estudos Prospectivos , Estações do Ano , África do Sul/epidemiologia , Vitamina D/análogos & derivados , Vitamina D/sangue , Adulto JovemRESUMO
Infection causes fever and suppression of appetite, a combination of effects which threatens normal growth in infected children. We have used an animal model to study the effects on growth of recurrent simulated Gram-positive bacterial infection. After weaning, 10 guinea pig pups underwent surgery under general anaesthesia for the implantation of temperature-sensitive radiotelemeters and thereafter were assigned to receive intramuscular injections of either 50 microg/kg muramyl dipeptide (MDP), or sterile saline. During a 30-day period corresponding to their rapid growth phase, the pups were given eight injections. MDP resulted in fevers of about 1.5 degrees C on each occasion, but no significant change in body temperature occurred after saline injections. Food intake was suppressed during each febrile episode such that 24-h intake was significantly lower on days of injections of MDP, compared to days between MDP injections in the same animals, and compared to that of animals injected with saline. The rate of weight gain of the MDP-injected guinea pigs was significantly lower than that of the control group and failed even to achieve a rate similar to the saline-injected group in their more adult-like growth phase. Plasma zinc concentration was significantly lower in MDP-compared to saline-injected animals sampled 8 days after the last injection. Our results show that recurrent fever during the growth phase of young guinea pigs results in irreversible growth failure, and that reduced food intake on days when the animals were febrile was at least partly responsible for this reduced rate of growth.
Assuntos
Temperatura Corporal/fisiologia , Peso Corporal/fisiologia , Febre Recorrente/fisiopatologia , Acetilmuramil-Alanil-Isoglutamina , Fatores Etários , Análise de Variância , Animais , Animais Recém-Nascidos , Temperatura Corporal/efeitos dos fármacos , Peso Corporal/efeitos dos fármacos , Modelos Animais de Doenças , Ingestão de Alimentos/efeitos dos fármacos , Ingestão de Alimentos/fisiologia , Cobaias , Injeções Intramusculares , Distribuição Aleatória , Febre Recorrente/induzido quimicamenteRESUMO
BACKGROUND/OBJECTIVES: Neonatal body composition is an important predictor of future metabolic risk; however, the comparability of objective assessment techniques, particularly in African populations undergoing rapid health transition, is not known. This paper compares body composition estimates by air-displacement plethysmography (ADP) and dual-energy X-ray absorptiometry (DXA) in South African neonates. SUBJECTS/METHODS: Fat mass, fat-free mass and body fat percentage (%fat) estimates by ADP and DXA were compared in 88 urban, black South African neonates. The level of agreement between the techniques was assessed using Bland-Altman analyses. RESULTS: Significant correlations were observed between ADP and DXA measurements of fat mass (r=0.766), fat-free mass (r=0.942) and %fat (r=0.630); however, ADP estimates of fat mass (408±172 g vs 337±165 g; P<0.001) and %fat (12.9±4.4% vs 9.9±4%; P<0.001) were significantly higher and fat-free mass (2681±348 g vs 2969±375 g; P<0.001) significantly lower than those by DXA. Fat-free mass estimates showed greater consistency in the level of agreement between the techniques compared with fat and %fat estimates where the differences between methods were less predictable. CONCLUSION: Although ADP and DXA body composition estimates are highly correlated in neonates, significant differences are observed between the techniques. This is particularly relevant for fat mass and %fat estimates, where differences are highly variable between methods. Further investigation is needed to minimise inter-method differences to ensure accurate and comparable assessment of body composition at birth and across longitudinal study follow-up.
Assuntos
Composição Corporal , Absorciometria de Fóton , Feminino , Humanos , Recém-Nascido , Masculino , Necessidades Nutricionais , Pletismografia , Reprodutibilidade dos Testes , África do SulRESUMO
We have previously documented evidence of dietary calcium deficiency in black children living in a rural community in the eastern part of South Africa. The present study determined the bone mass of the distal one-third of the radius in a random sample of children living in the same community and compared their bone mass measurements with those of black children living in a similar rural community but without evidence of dietary calcium deficiency. Further, factors (weight, height, serum corrected total calcium, phosphorus, and alkaline phosphatase [ALP]) that might influence appendicular bone mass were assessed and correlated with the bone mass measurements. A random sample of 306 boys and 345 girls between the ages of 1 and 20 years were included in the study. Hypocalcemia was found in 6.5% of the boys and 5% of the girls, while elevated ALP values were recorded in 20 and 26% of the boys and girls, respectively. After adjusting for differences in age, weight, and height, bone mineral density (BMD) and bone mineral apparent density (BMAD) were significantly lower and bone width (BW) greater in study than control children. In a stepwise regression analysis, weight and/or height accounted for the majority of the observed variance in BMC, BW, and BMD; however, a significant effect of serum calcium (positively) and ALP (negatively) on BMC and BMD was also found. In boys, but not girls, serum ALP also had a positive effect on BW.BMAD was negatively correlated to ALP and positively correlated to serum calcium in both boys and girls. Those children with hypocalcemia or elevated ALP levels had significantly lower BMC, BMD, and BMAD and a trend toward greater BW than children with normal biochemistry. The findings suggest that low dietary calcium intake may have a detrimental effect on appendicular bone density in rural black children. Whether or not these effects are disadvantageous in the long-term is not known.
Assuntos
Densidade Óssea/fisiologia , Cálcio da Dieta/administração & dosagem , Cálcio/deficiência , Rádio (Anatomia)/metabolismo , Absorciometria de Fóton , Adolescente , Adulto , Fosfatase Alcalina/sangue , População Negra , Estatura/fisiologia , Peso Corporal/fisiologia , Cálcio/sangue , Cálcio/urina , Criança , Pré-Escolar , Feminino , Inquéritos Epidemiológicos , Humanos , Lactente , Masculino , Rádio (Anatomia)/anatomia & histologia , Rádio (Anatomia)/diagnóstico por imagem , Análise de Regressão , África do Sul , Espectrofotometria AtômicaRESUMO
Calcium deficiency in black (African) children can cause rickets and osteomalacia with severe limb deformities. It is not known whether black teenagers with genu valgum or varum but without radiologic rickets suffer from a related disorder. To examine this question we studied 26 such patients by iliac crest bone biopsy and serum and urine biochemistry: 12 patients (46%) had osteopenia with normal or low bone turnover, 5 (19%) mildly increased bone turnover, 4 (15%) histologic hyperparathyroidism, 2 (8%) preosteomalacia, and 3 (12%) osteomalacia (with features of hyperparathyroidism). Radiographs did not reflect the severity of the bone disease. Serum calcium levels correlated inversely with eroded mineralized surface (p < 0.001), osteoid surface (p < 0.01), osteoid thickness (p < 0.001), mineralization lag time (p < 0.001), and 1,25-(OH)2 vitamin D (p < 0.005), and 1,25-(OH)2 vitamin D correlated positively with osteoid surface (p < 0.05), osteoid thickness (p < 0.05), osteoid volume (p < 0.01), eroded surface (p < 0.05), and eroded mineralized surface (p < 0.0005). Tubular reabsorption of phosphate and 25-OH vitamin D levels were normal, and 1,25-(OH)2 vitamin D levels were normal to high. This suggests that calcium deficiency may have caused the increase in bone turnover and the mineralization defects. The most severe osteomalacia was found in males aged 16-19 years. We cannot explain the cause of the osteopenia. We conclude that all patients had bone disease.
Assuntos
Doenças Ósseas Metabólicas/metabolismo , Adolescente , Adulto , População Negra , Densidade Óssea , Doenças Ósseas Metabólicas/diagnóstico por imagem , Doenças Ósseas Metabólicas/etiologia , Cálcio/sangue , Cálcio/deficiência , Feminino , Humanos , Hiperparatireoidismo/etiologia , Joelho/anormalidades , Masculino , Osteomalacia/etiologia , Radiografia , Raquitismo/diagnóstico por imagem , Raquitismo/etiologiaRESUMO
The prevalence of senile and postmenopausal osteoporotic fractures is considerably higher in white than black women. Although the reasons for the genetic difference have not been elucidated, it has been suggested that ethnic differences in peak bone mass may be partially responsible. The present study examined appendicular bone mass (single-photon absorptiometry, SPA) in black and white children between the ages of 6 and 20 years. The sample was stratified for ethnic group, age, and sex. The effect of weight, height, puberty, and skinfold thickness on bone mass was also assessed. The bone width (BW) and bone mineral content (BMC) of males were significantly higher than those of females (p less than 0.0001). There were no statistically significant differences in bone mineral content normalized for bone width (BMC/BW) between the sexes (p = 0.1743 for whites and p = 0.5456 for blacks). The bone mass parameters of black girls were generally lower than those of white girls. After adjusting for height, BMC and BMC/BW of black girls tended to be greater than those of white girls (unadjusted p = 0.0258 for BMC and p = 0.0340 for BMC/BW). White boys tended to have greater bone mass parameters than black boys. After adjusting for height the trends disappeared. Thus, unlike the studies of bone mass in adults from the United States, we were unable to show that age-matched black children have higher bone mass than whites. After adjusting for height, however, the bone mass of black children (especially black girls) was marginally, but not significantly, greater than that of white girls.
Assuntos
População Negra/genética , Densidade Óssea/genética , População Branca/genética , Adolescente , Adulto , Estatura/fisiologia , Peso Corporal/fisiologia , Criança , Extremidades , Feminino , Humanos , Masculino , Puberdade/fisiologia , Análise de Regressão , Caracteres Sexuais , África do Sul/epidemiologiaRESUMO
In the United States, the higher prevalence of osteoporosis and the higher incidence of fractures in whites than in blacks may be attributed to the finding of lower bone density (BD) in both white children and adults. In South Africa, osteoporosis and fractures also occur more frequently in whites than in blacks. Appendicular BD has been found to be similar in black and white children in South Africa, but there is little information available on BD of adults in South Africa. This cross-sectional study aimed to assess changes in BD with age in adult females in South Africa and to assess possible differences in peak BD and in the rate of postmenopausal bone loss between blacks and whites. Data for 180 black and 184 white female nurses aged 20-64 years were analyzed. The distal radius bone density (RBD) was measured by single photon absorptiometry. The lumbar spine bone density (SBD) and the femur bone density (FBD) were measured by dual-energy X-ray absorptiometry. Blacks were shorter than whites (p = 0.0001), and blacks' weight, body mass index, and skinfold thickness increased with age. Peak SBD and RBD were similar in blacks and whites, but peak FBD was higher in blacks (p = 0.0001). This ethnic difference in peak FBD became apparent in the fourth decade. Peak FBD was similar in black and white subjects with normal body mass indices (p = 0.09), but in overweight subjects peak FBD was higher in blacks than in whites (p = 0.0001).(ABSTRACT TRUNCATED AT 250 WORDS)
Assuntos
População Negra , Densidade Óssea/fisiologia , Osteoporose Pós-Menopausa/etnologia , População Branca , Absorciometria de Fóton , Adulto , Fatores Etários , Índice de Massa Corporal , Estudos de Coortes , Estudos Transversais , Feminino , Fraturas do Fêmur/epidemiologia , Fêmur/fisiologia , Humanos , Vértebras Lombares/fisiologia , Pessoa de Meia-Idade , Enfermeiras e Enfermeiros , Osteoporose Pós-Menopausa/fisiopatologia , Rádio (Anatomia)/fisiologia , Medição de Risco , África do Sul/epidemiologia , Fraturas da Coluna Vertebral/epidemiologiaRESUMO
Nutritional rickets is common in Nigeria where vitamin D deficiency is rare and dietary insufficiency of calcium is common. It occurs more commonly in siblings of affected children than of unaffected children. Postulating that vitamin D receptor (VDR) polymorphisms might relate to the susceptibility of some Nigerian children to develop rickets in the setting of low calcium intake, we compared the VDR genotypes, as determined by the presence or absence of Bsm I, Apa I, Taq I, and Fok I restriction enzyme cleavage sites, between 105 children with active nutritional rickets and 94 subjects representative of the community from which the rachitic children came. In the rickets group, the ff genotype was less common than in the community group, and the FF genotype was relatively increased (f allele frequency, 17% in rachitic children and 26% in the community group, p = 0.03). Neither individual allele frequencies for the other polymorphisms nor combinations of genotypes at different sites were different between the rachitic and community groups. Although it is not clear why a presumed better-functioning VDR variant (F allele) is associated with an increased risk of developing rickets, this study raises the possibility that VDR alleles might be important in determining an individual's susceptibility to developing rickets when faced with dietary calcium deficiency.
Assuntos
Polimorfismo Genético , Receptores de Calcitriol/genética , Raquitismo/genética , Adulto , Cálcio/deficiência , Estudos de Casos e Controles , Criança , Desoxirribonucleases de Sítio Específico do Tipo II/genética , Predisposição Genética para Doença , Humanos , NigériaRESUMO
The prevalence of biochemical abnormalities usually associated with rickets was investigated in three black school-going populations, one from a rural community, one from a small urban community, and one from a large urban area. A high prevalence of biochemical abnormalities was found in the rural community, where 13.2% of children were hypocalcemic and 41.5% had elevated alkaline phosphatase concentrations. No hypocalcemia was detected in the children from the large urban area. Urinary calcium excretion was lowest in the community with the highest prevalence of hypocalcimia and elevated alkaline phosphatase concentrations. Dietary calcium intake in those children with biochemical abnormalities was estimated at 125 mg/day, compared with 337 mg/day in those children with normal biochemistry. It is suggested that the pathogenesis of the biochemical abnormalities in the rural community is due to a low dietary intake of calcium.
Assuntos
Cálcio/deficiência , Envelhecimento , Fosfatase Alcalina/sangue , População Negra , Cálcio/metabolismo , Cálcio da Dieta , Criança , Feminino , Crescimento , Humanos , Hipocalcemia/etiologia , Masculino , População Rural , Fatores Sexuais , África do Sul , População UrbanaRESUMO
In a rural community, where low calcium intakes and a high prevalence of hypocalcemia elevated alkaline phosphatase values and hypocalciuria had previously been documented, two groups of 30 black school children were supplemented with calcium (500 mg/day) or a placebo for a period of 3 months. No change in serum calcium or alkaline phosphatase values occurred in the placebo group, while a significant rise in mean serum calcium and fall in mean alkaline phosphatase concentrations was found in the calcium-supplemented group over the 3-month trial. No difference in growth velocities in the two groups of children was noted over the period. These results suggest that the prevalence of biochemical abnormalities in the rural population is related to a low dietary calcium intake which can be corrected by a supplement of oral calcium only.