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2.
Pediatr Hematol Oncol ; 40(7): 659-672, 2023.
Article in English | MEDLINE | ID: mdl-37092844

ABSTRACT

Children with cancer require adequate nutritional support to prevent malnutrition. This study investigated the impact of chemotherapy on anthropometrical status and body composition during the first six months of treatment. Anthropometrical status and body composition were measured at diagnosis, utilizing standardized protocols and validated S10 InBody bio-electrical impedance (BIA) measurements and compared to subsequent consecutive monthly follow-up measurements to plot changes over time during the first six months. Statistical significance was defined as p < 0.05. Forty-three newly diagnosed children (median age 4 years, IQR: 2.0-7.6; male-female ratio 1:0.9; 53% haematological malignancies and 47% solid tumors) were included. Prevalence of malnutrition varied, with under-nutrition 14% (mid-upper arm circumference (MUAC)/body mass index (BMI)), over-nutrition 9.3% (BMI) and stunting 7% at diagnosis. MUAC (14%) identified fewer participants with underlying muscle store depletion than BIA (41.8%). Chemotherapy exposure acutely exacerbated existing nutritional depletion during the first two months after diagnosis for all variables except fat mass (FM), with contrary effects on cancer type. Haematological malignancies had rapid increases in weight, BMI and FM. All patients had an acute loss of skeletal muscle mass. Nutritional improvement experienced by all cancer types during month two to three of treatment resulted in catch-up growth, with a significant increase in weight (chi2=40.43, p < 0.001), height (chi2=53.79, p < 0.001), BMI (chi2=16.32, p < 0.005), fat free mass (chi2=23.69, p < 0.003) and skeletal muscle mass (chi2=24.19, p < 0.001) after six months. Monthly nutritional assessments, including advanced body composition measurements, are essential to provide timely nutritional interventions to overcome the acute decline in nutritional reserves observed during the first two months of chemotherapy exposure.


Subject(s)
Hematologic Neoplasms , Malnutrition , Neoplasms , Humans , Male , Child , Female , Child, Preschool , Anthropometry/methods , Body Mass Index , Nutritional Status , Body Composition , Malnutrition/epidemiology , Neoplasms/drug therapy , Hematologic Neoplasms/drug therapy
3.
Nature ; 602(7898): 585-589, 2022 02.
Article in English | MEDLINE | ID: mdl-35197615

ABSTRACT

Fast radio bursts (FRBs) are flashes of unknown physical origin1. The majority of FRBs have been seen only once, although some are known to generate multiple flashes2,3. Many models invoke magnetically powered neutron stars (magnetars) as the source of the emission4,5. Recently, the discovery6 of another repeater (FRB 20200120E) was announced, in the direction of the nearby galaxy M81, with four potential counterparts at other wavelengths6. Here we report observations that localized the FRB to a globular cluster associated with M81, where it is 2 parsecs away from the optical centre of the cluster. Globular clusters host old stellar populations, challenging FRB models that invoke young magnetars formed in a core-collapse supernova. We propose instead that FRB 20200120E originates from a highly magnetized neutron star formed either through the accretion-induced collapse of a white dwarf, or the merger of compact stars in a binary system7. Compact binaries are efficiently formed inside globular clusters, so a model invoking them could also be responsible for the observed bursts.

4.
S Afr Med J ; 110(11): 1128-1133, 2020 Oct 28.
Article in English | MEDLINE | ID: mdl-33403992

ABSTRACT

BACKGROUND: Vitamin D deficiency is common in intensive care unit (ICU) patients (50 - 82%) and is associated with multi-organ dysfunction. Vitamin D deficiency alters pathways of glutamine metabolism in critical illness, but the impact of vitamin D status on glutamine levels is poorly characterised. OBJECTIVES: To assess the prevalence of vitamin D deficiency and its association with organ dysfunction and glutamine levels in a South African (SA) ICU. METHODS: Records of 103 adult patients admitted to the Wits Donald Gordon Medical Centre ICU, Johannesburg, SA were retrospectively reviewed. 25-hydroxyvitamin D (25(OH)D) and glutamine levels were measured on admission. The association between admission vitamin D levels and glutamine levels, illness severity scores, organ support and outcomes was examined. RESULTS: On ICU admission, 66% (68/103) of patients were vitamin D deficient (<20 ng/mL) (95% confidence interval (CI) 56 - 75). Vitamin D deficiency was significantly associated with mechanical ventilation (40% v. 14%) (p=0.013) and a higher median sequential organ failure assessment (SOFA) score on admission (6 (interquartile range (IQR) 3 - 8) v. 4 (IQR 2 - 6)) (p=0.047) and on day 7 (5 (IQR 2 - 10) v. 2 (IQR 1 - 4)) (p=0.017). Median admission serum glutamine levels were 481 µmol/L, with 38% deficient (<420 µmol/L) (95% CI 28 - 48). Vitamin D deficiency status on admission was not significantly associated with median admission glutamine levels (p=0.66). CONCLUSIONS: Vitamin D deficiency is common in ICU patients in SA. Deficient patients were more severely ill and required more respiratory support. No significant relationship between deficiency and median glutamine levels was noted.


Subject(s)
Critical Illness/epidemiology , Glutamine/blood , Intensive Care Units , Vitamin D Deficiency/blood , Vitamin D/analogs & derivatives , Adult , Female , Humans , Length of Stay/statistics & numerical data , Male , Middle Aged , Multiple Organ Failure/diagnosis , Prevalence , Retrospective Studies , Risk Factors , South Africa , Vitamin D/blood , Vitamin D Deficiency/diagnosis
5.
Nature ; 568(7752): 360-363, 2019 04.
Article in English | MEDLINE | ID: mdl-30996312

ABSTRACT

Lightning is a dangerous yet poorly understood natural phenomenon. Lightning forms a network of plasma channels propagating away from the initiation point with both positively and negatively charged ends-called positive and negative leaders1. Negative leaders propagate in discrete steps, emitting copious radio pulses in the 30-300-megahertz frequency band2-8 that can be remotely sensed and imaged with high spatial and temporal resolution9-11. Positive leaders propagate more continuously and thus emit very little high-frequency radiation12. Radio emission from positive leaders has nevertheless been mapped13-15, and exhibits a pattern that is different from that of negative leaders11-13,16,17. Furthermore, it has been inferred that positive leaders can become transiently disconnected from negative leaders9,12,16,18-20, which may lead to current pulses that both reconnect positive leaders to negative leaders11,16,17,20-22 and cause multiple cloud-to-ground lightning events1. The disconnection process is thought to be due to negative differential resistance18, but this does not explain why the disconnections form primarily on positive leaders22, or why the current in cloud-to-ground lightning never goes to zero23. Indeed, it is still not understood how positive leaders emit radio-frequency radiation or why they behave differently from negative leaders. Here we report three-dimensional radio interferometric observations of lightning over the Netherlands with unprecedented spatiotemporal resolution. We find small plasma structures-which we call 'needles'-that are the dominant source of radio emission from the positive leaders. These structures appear to drain charge from the leader, and are probably the reason why positive leaders disconnect from negative ones, and why cloud-to-ground lightning connects to the ground multiple times.

6.
J Cachexia Sarcopenia Muscle ; 10(1): 207-217, 2019 02.
Article in English | MEDLINE | ID: mdl-30920778

ABSTRACT

RATIONALE: This initiative is focused on building a global consensus around core diagnostic criteria for malnutrition in adults in clinical settings. METHODS: In January 2016, the Global Leadership Initiative on Malnutrition (GLIM) was convened by several of the major global clinical nutrition societies. GLIM appointed a core leadership committee and a supporting working group with representatives bringing additional global diversity and expertise. Empirical consensus was reached through a series of face-to-face meetings, telephone conferences, and e-mail communications. RESULTS: A two-step approach for the malnutrition diagnosis was selected, i.e., first screening to identify "at risk" status by the use of any validated screening tool, and second, assessment for diagnosis and grading the severity of malnutrition. The malnutrition criteria for consideration were retrieved from existing approaches for screening and assessment. Potential criteria were subjected to a ballot among the GLIM core and supporting working group members. The top five ranked criteria included three phenotypic criteria (weight loss, low body mass index, and reduced muscle mass) and two etiologic criteria (reduced food intake or assimilation, and inflammation or disease burden). To diagnose malnutrition at least one phenotypic criterion and one etiologic criterion should be present. Phenotypic metrics for grading severity as Stage 1 (moderate) and Stage 2 (severe) malnutrition are proposed. It is recommended that the etiologic criteria be used to guide intervention and anticipated outcomes. The recommended approach supports classification of malnutrition into four etiology-related diagnosis categories. CONCLUSION: A consensus scheme for diagnosing malnutrition in adults in clinical settings on a global scale is proposed. Next steps are to secure further collaboration and endorsements from leading nutrition professional societies, to identify overlaps with syndromes like cachexia and sarcopenia, and to promote dissemination, validation studies, and feedback. The diagnostic construct should be re-considered every 3-5 years.


Subject(s)
Malnutrition/diagnosis , Adult , Body Mass Index , Consensus , Eating , Global Health , Humans , Phenotype , Sarcopenia/diagnosis , Weight Loss
7.
Clin Nutr ; 38(6): 2583-2591, 2019 12.
Article in English | MEDLINE | ID: mdl-30638739

ABSTRACT

BACKGROUND AND AIMS: Data in critically ill patients on the effect of intravenous lipid emulsions (LEs), containing omega-3 polyunsaturated fatty acids (PUFAs), in parenteral nutrition (PN) are scarce and conflicting. This study compared the effects of a four-oil LE (30% soybean oil, 30% medium-chain triglycerides, 25% olive oil and 15% fish oil (FO)) (SMOFlipid®) to those of a 100% soybean oil-based LE in critically ill adult intensive care unit (ICU) patients. METHODS: In this double-blind, randomised study, patients (n = 75) predicted to need PN for more than 5 days were randomised to receive either a four-oil LE (Study Group (SG)) or a 100% soybean oil LE (Control Group (CG)). Isocaloric, isonitrogenous PN was administered continuously for 5 days. FO was provided at a dose of 0.09-0.22 g/kg body weight. Measurements included biochemical parameters and sequential organ failure assessment (SOFA) score daily and plasma total phospholipid fatty acids (FAs) and cytokine levels on days 1, 3, 6. Days on mechanical ventilation, length of stay and mortality were also recorded. ANOVA was used to compare response variables between the two groups over the time and Pearson correlation was used to measure relationships between continuous variables. RESULTS: 68 patients completed the study (n = 35 SG, n = 33 CG), with male predominance (66% SG, 56% CG). Average age was 60.8 ± 13.9 years (SG) versus 55.7 ± 14.8 (CG) (p = 0.143). The majority were surgical admissions (85% SG versus 91% CG) followed by medical. Plasma phospholipid oleic acid (p = 0.022) and alpha-linolenic acid (p<0.0005) increased in both groups. In the SG, plasma phospholipid EPA and DHA increased (both p<0.001), whereas the omega-6:omega-3 PUFA (n-6:n-3 PUFA) ratio decreased (p < 0.001). Aspartate aminotransferase (AST), alanine aminotransferase (ALT) and bilirubin decreased in both treatment groups. Considering only the change from day 1 to day 6 there was a bigger decrease in AST, ALT and bilirubin levels in the SG. Concentrations of TNF-α decreased from day 1 to day 6 in the SG, whereas they increased in the CG, but the change was not statistically significant (p = 0.112). A significant negative correlation was found between EPA provision on day 3 and the SOFA score (r = -0.4047, p = 0.018). Days on mechanical ventilation (1.24 ± 0.83 days in SG versus 0.88 ± 1.63 days in CG, p = 0.385) and ICU LOS (9.5 ± 7.09 days in SG versus 10.7 ± 7.6 days in CG, p = 0.490) were not different between groups. CONCLUSION: PN containing a four-oil LE increased plasma EPA and DHA, decreased n-6:n-3 PUFA ratio, and was safe and well tolerated. The negative relationship between day 3 EPA and SOFA score seems promising, but EPA intake and effects may have been diluted by enteral nutrition which was started in more than half of patients on day 4. There was no significant difference in terms of other biochemical measurements, SOFA score, length of ICU stay and mortality. More research is needed in this patient population, particularly regarding dose, duration and timing of FO and the effects on clinical outcomes.


Subject(s)
Critical Care/methods , Critical Illness , Fat Emulsions, Intravenous , Fatty Acids/blood , Aged , Biomarkers/blood , Critical Illness/epidemiology , Critical Illness/therapy , Dietary Fats, Unsaturated , Double-Blind Method , Fat Emulsions, Intravenous/administration & dosage , Fat Emulsions, Intravenous/therapeutic use , Female , Fish Oils , Humans , Male , Middle Aged , Parenteral Nutrition , Treatment Outcome , Triglycerides
8.
Clin Nutr ; 38(1): 1-9, 2019 02.
Article in English | MEDLINE | ID: mdl-30181091

ABSTRACT

RATIONALE: This initiative is focused on building a global consensus around core diagnostic criteria for malnutrition in adults in clinical settings. METHODS: In January 2016, the Global Leadership Initiative on Malnutrition (GLIM) was convened by several of the major global clinical nutrition societies. GLIM appointed a core leadership committee and a supporting working group with representatives bringing additional global diversity and expertise. Empirical consensus was reached through a series of face-to-face meetings, telephone conferences, and e-mail communications. RESULTS: A two-step approach for the malnutrition diagnosis was selected, i.e., first screening to identify "at risk" status by the use of any validated screening tool, and second, assessment for diagnosis and grading the severity of malnutrition. The malnutrition criteria for consideration were retrieved from existing approaches for screening and assessment. Potential criteria were subjected to a ballot among the GLIM core and supporting working group members. The top five ranked criteria included three phenotypic criteria (non-volitional weight loss, low body mass index, and reduced muscle mass) and two etiologic criteria (reduced food intake or assimilation, and inflammation or disease burden). To diagnose malnutrition at least one phenotypic criterion and one etiologic criterion should be present. Phenotypic metrics for grading severity as Stage 1 (moderate) and Stage 2 (severe) malnutrition are proposed. It is recommended that the etiologic criteria be used to guide intervention and anticipated outcomes. The recommended approach supports classification of malnutrition into four etiology-related diagnosis categories. CONCLUSION: A consensus scheme for diagnosing malnutrition in adults in clinical settings on a global scale is proposed. Next steps are to secure further collaboration and endorsements from leading nutrition professional societies, to identify overlaps with syndromes like cachexia and sarcopenia, and to promote dissemination, validation studies, and feedback. The diagnostic construct should be re-considered every 3-5 years.


Subject(s)
Internationality , Malnutrition/diagnosis , Nutrition Assessment , Adult , Consensus , Humans , Leadership , Nutritional Status , Societies, Scientific
9.
S. Afr. fam. pract. (2004, Online) ; 61(4): 150-158, 2019. ilus
Article in English | AIM (Africa) | ID: biblio-1270106

ABSTRACT

Background: Vitamin D deficiency is fast emerging as a global pandemic. In South Africa few studies have been conducted to determine the vitamin D status of the healthy population.Methods: This prospective study with an analytical component investigated vitamin D status of healthy undergraduate students at two time points (winter and summer) at Stellenbosch University. Serum 25(OH)D was determined, anthropometric measurements taken and dietary vitamin D intake estimated (food-frequency questionnaire). Skin tone was determined (Fitzpatrick skin type classification), and a skin reflectometry device used to measure dermal melanin content.Results: Results of 242 students indicated a mean serum 25(OH)D of 63.80 ± 41.35 ng/ml and a high prevalence of vitamin D sufficiency (88%). Significantly more females experienced suboptimal vitamin D levels than males (18 vs. 5%; p < 0.01). Participants with lighter skin tones had higher levels of 25(OH)D than those with darker skin tones (chi-square = 24.02; p = 0.02). The majority (60.74%) had a normal BMI, although there was no significant relationship between BMI and serum 25 (OH)D (Spearman's r=­0.11; p = 0.09). Total mean dietary vitamin D intake was 7.99 ± 13.81 mcg, with 87.2% having inadequate intake (< 15 mcg). The relationship between total vitamin D intake and serum 25(OH)D was found to be significant in winter (p < 0.001) and summer (p = 0.01). Serum vitamin D levels were significantly higher in the winter phase (p < 0.001).Conclusions: A low prevalence of vitamin D deficiency was found amongst healthy young adults, despite low dietary vitamin D intakes. Significant relationships were found between serum 25(OH)D and gender, skin tone and vitamin D intake. Further studies need to be conducted, especially in high-risk groups, before results are applied to the greater South African public


Subject(s)
Adult , Healthy People Programs
10.
S. Afr. j. clin. nutr. (Online) ; 65(05): 29-34, 2018. ilus
Article in English | AIM (Africa) | ID: biblio-1270567

ABSTRACT

Introduction: Intestinal failure is the consequence of diverse aetiologies and pathophysiological causes. Fistuloclysis is an effective means of nutritional support to selected intestinal failure patients. This study aimed to investigate the management of adult intestinal failure patients in hospitals in South Africa, determining how practical and acceptable fistuloclysis is.Methods: The current management of type 2 and type 3 intestinal failure patients in South African hospitals was investigated by means of occupation-specific questionnaires, evaluating perceptions and opinions among dietitians. Results: Twenty-seven dietitians indicated willingness to participate in the survey, the majority (67%) having been involved with patient management in this field for one to five years. All indicated correctly that high fistula outputs would be defined as intestinal failure. Only 47% gave the correct definition of fistuloclysis, while 28% were currently utilising it as a means of nutrition support. All respondents agreed that unsuccessful implementation of fistuloclysis was due to training shortfalls and resistance Conclusion : There is a positive perception and awareness of fistuloclysis; however, numerous stumbling blocks hamper the wider use of this novel


Subject(s)
Intestinal Fistula/etiology , Intestinal Fistula/physiopathology , Nutritional Support , Nutritionists , South Africa
11.
Planet Space Sci ; Volume 143: 67-70, 2017 Mar 16.
Article in English | MEDLINE | ID: mdl-32020951

ABSTRACT

We present our method to calculate the meteor limiting magnitude. The limiting meteor magnitude defines the faintest magnitude at which all meteors are still detected by a given system. An accurate measurement of the limiting magnitude is important in order to calculate the meteoroid flux from a meteor shower or sporadic source. Since meteor brightness is linked to meteor mass, the limiting magnitude is needed to calculate the limiting mass of the meteor flux measurement. The mass distribution of meteoroids is thought to follow a power law, thus being slightly off in the limiting magnitude can have a significant effect on the measured flux. Sky conditions can change on fairly short timescales; therefore one must monitor the meteor limiting magnitude at regular intervals throughout the night, rather than just measuring it once. We use the stellar limiting magnitude as a proxy of the meteor limiting magnitude. Our method for determining the stellar limiting magnitude and how we transform it into the meteor limiting magnitude is presented. These methods are currently applied to NASA's wide-field meteor camera network to determine nightly fluxes, but are applicable to other camera networks.

12.
J Hum Nutr Diet ; 29(6): 777-785, 2016 12.
Article in English | MEDLINE | ID: mdl-27333813

ABSTRACT

BACKGROUND: Research investigating the association of infant dietary factors with later health outcomes often relies on maternal recall. It is unclear what the effect of recall bias is on the accuracy of the information obtained. The present study aimed to determine the extent of recall bias on the accuracy of infant feeding and food allergen data collected 10 years later. METHODS: Mothers were recruited from a prospective birth cohort from the Isle of Wight. When their child was 10 years of age (2011/2012), mothers were requested to complete a retrospective infant feeding questionnaire asking the same questions as those solicited in 2001/2002. RESULTS: In total, 125 mothers participated. There was substantial agreement for recollection of any breastfeeding (κ = 0.79) and the duration of breastfeeding from 10 years earlier (r = 0.84). Some 94% of mothers recalled accurately that their child had received formula milk. The exact age at which formula milk was first given was reliably answered (r = 0.63). The brand of formula milk was poorly recalled. Recall of age of introduction of solid food was not reliable (r = 0.16). The age of introduction of peanuts was the only food allergen that was recalled accurately (86%). CONCLUSIONS: The present study highlights the importance of maternal recall bias of infant feeding practices over 10 years. Recall related to breastfeeding and formula feeding were reliable, whereas recalls related to age of introduction of solid or allergenic foods, apart from peanut, were not. Caution should be applied when interpreting studies relying on dietary recall.


Subject(s)
Breast Feeding/psychology , Eating/psychology , Feeding Behavior/psychology , Mental Recall , Mothers/psychology , Allergens , Child , Female , Food Hypersensitivity/psychology , Humans , Infant , Infant Formula , Infant, Newborn , Male , Prospective Studies , Retrospective Studies , Time Factors
13.
Nature ; 503(7475): 238-41, 2013 Nov 14.
Article in English | MEDLINE | ID: mdl-24196713

ABSTRACT

Most large (over a kilometre in diameter) near-Earth asteroids are now known, but recognition that airbursts (or fireballs resulting from nuclear-weapon-sized detonations of meteoroids in the atmosphere) have the potential to do greater damage than previously thought has shifted an increasing portion of the residual impact risk (the risk of impact from an unknown object) to smaller objects. Above the threshold size of impactor at which the atmosphere absorbs sufficient energy to prevent a ground impact, most of the damage is thought to be caused by the airburst shock wave, but owing to lack of observations this is uncertain. Here we report an analysis of the damage from the airburst of an asteroid about 19 metres (17 to 20 metres) in diameter southeast of Chelyabinsk, Russia, on 15 February 2013, estimated to have an energy equivalent of approximately 500 (±100) kilotons of trinitrotoluene (TNT, where 1 kiloton of TNT = 4.185×10(12) joules). We show that a widely referenced technique of estimating airburst damage does not reproduce the observations, and that the mathematical relations based on the effects of nuclear weapons--almost always used with this technique--overestimate blast damage. This suggests that earlier damage estimates near the threshold impactor size are too high. We performed a global survey of airbursts of a kiloton or more (including Chelyabinsk), and find that the number of impactors with diameters of tens of metres may be an order of magnitude higher than estimates based on other techniques. This suggests a non-equilibrium (if the population were in a long-term collisional steady state the size-frequency distribution would either follow a single power law or there must be a size-dependent bias in other surveys) in the near-Earth asteroid population for objects 10 to 50 metres in diameter, and shifts more of the residual impact risk to these sizes.

14.
Toxicol In Vitro ; 27(5): 1425-32, 2013 Aug.
Article in English | MEDLINE | ID: mdl-23563205

ABSTRACT

The present study shows significant correlations between the EC50 for PPARγ activation in a reporter gene cell line and resistin downregulation in mouse adipocytes, and between the IC50 for resistin downregulation and the already published minimum effective dose for antihyperglycemic activity in a mouse model. These correlations indicate that PPARγ mediated downregulation of resistin might promote insulin sensitivity and that downregulation of resistin in mouse adipocytes provides an adequate and possibly more direct bioassay for screening of newly developed antihyperglycemic compounds. Because of the higher throughput of the PPARγ the resistin downregulation assays seems most suitable to be used as a second tier in a tiered screening strategy.


Subject(s)
Adipocytes/drug effects , PPAR gamma/metabolism , Resistin/genetics , Thiazolidinediones/pharmacology , 3T3-L1 Cells , Adipocytes/cytology , Animals , Cell Differentiation/drug effects , Cell Line , Down-Regulation , Mice , RNA, Messenger/metabolism
15.
J Synchrotron Radiat ; 8(Pt 6): 1186-90, 2001 Nov 01.
Article in English | MEDLINE | ID: mdl-11679770

ABSTRACT

The crystal structures of [1,2-bis(2,6-diisopropylphenylimino)acenaphthene-N,N']carbonylchlororhodium(I) (1) and [N,N'-ethylene-bis(3-methylsalicylideneiminato)-O,N,N',O'](tetrahydrofurfuryl)-cobalt(II) (2) have been determined from high-resolution synchrotron X-ray powder diffraction data. Compound 1 is the first neutral Rh complex, in contrast with findings in the literature, containing a bidentate nitrogen ligand, and compound 2 is the first three-dimensional structure of a (five-coordinated) tetrahydrofurfurylcobalt(III) complex. Grid-search and Rietveld refinement have been used to determine and refine the structures, respectively. Crystals of 1 are orthorhombic, space group Pbca, Z = 8, with cell parameters a = 21.729 (2), b = 27.376 (3), c = 11.580 (1) A. Crystals of 2 are monoclinic, space group P2(1)/n, Z = 4, a = 16.6701 (6), b = 9.4170 (4), c = 13.7088 (7) A and beta = 96.520 (3) degrees. Chemical diagrams for the two compounds are given. Soft restraints were applied during Rietveld refinement; for 1 converging to R(p) = 8.4%, R(w) = 11.0%, GoF = 2.3, and for 2 converging to R(p) = 8.5%, R(w) = 11.4%, GoF = 7.6.

16.
J Org Chem ; 66(1): 233-42, 2001 Jan 12.
Article in English | MEDLINE | ID: mdl-11429905

ABSTRACT

A synthesis of the bicyclo[2.1.1]hexane substructure of solanoeclepin A (1), the most active natural hatching agent of potato cyst nematodes, was approached via an intramolecular [2 + 2] photocycloaddition. Aldehyde 12 containing the dioxenone chromophore served as a useful starting material, allowing the synthesis of a variety of photocycloaddition substrates via Grignard addition or via a Nozaki-Hiyama-Kishi reaction. Photolysis of the unsubstituted alkene 14 led to the expected crossed cycloadduct bicyclo[2.1.1]hexane 15 according to the so-called rule of five. However, several functionalized alkenes 18, 20, and 31 exhibited a complete reversal of cycloaddition regioselectivity, providing straight cycloadducts bicyclo[2.2.0]hexanes 21-26 and 4, respectively. Their structures were proved by a combination of extensive NMR measurements, X-ray analyses, and subsequent retro-aldol reactions. The latter de Mayo process allowed the formation of spiro-[3.5]nonane 35 and spiro[3.4]octane 36 as well as the cyclobutanes 37 and 38. Finally, the cyclization of the more rigid lactone precursor 28 occurred in high yield in the desired fashion with complete regio- and stereoselectivity to give 3 containing the core bicyclo[2.1.1]hexane skeleton of the natural product.


Subject(s)
Antinematodal Agents/chemistry , Bridged-Ring Compounds/chemistry , Hexanes/chemistry , Antinematodal Agents/chemical synthesis , Bridged Bicyclo Compounds/chemical synthesis , Bridged Bicyclo Compounds/chemistry , Bridged-Ring Compounds/chemical synthesis , Cyclization , Hexanes/chemical synthesis , Photochemistry
18.
S Afr Med J ; 86(9): 1081-4, 1996 Sep.
Article in English | MEDLINE | ID: mdl-8888774

ABSTRACT

OBJECTIVE: The aim of this study was to compare the body fat distribution of patients with osteoporosis (OP) with that of an appropriately matched non-OP control group. DESIGN: Case control study. SETTING: Department of Endocrinology and Metabolism, Tygerberg Hospital. Participants. A total of 56 patients with histologically proven idiopathic OP, of whom 39 were women (mean age 61 +/- 11 years) and 17 men (49 +/- 15 years), were compared with 125 age- and sex-matched non-OP (confirmed by dual energy X-ray absorptiometry) subjects, 98 women (60 +/- 11 years) and 27 men (51 +/- 16 years). OUTCOME MEASURES: Anthropometric data, including weight, height, skinfold measurements, mid-upper arm, waist and hip circumferences, as well as elbow breadth. RESULTS: The men and women with OP were significantly shorter (P = 0.04 and P = 0.03 respectively) and of lower body mass (P = 0.04 and P = 0.02 respectively) than the control subjects, although their mean body mass indices were comparable. The OP population had significantly lower skinfold, elbow breadth and arm circumference values, although the majority of subjects in both groups fell within the 15-85th percentiles. Despite their lower body mass, both the OP women (P = 0.009) and men (P = 0.002) had significantly higher waist/hip ratios than corresponding controls. CONCLUSION: Whatever the underlying pathogenesis, this new finding suggests that, should these results be confirmed by larger studies, OP can be added to the list of diseases associated with a waist fat distribution.


Subject(s)
Obesity/complications , Osteoporosis/complications , Aged , Body Height , Body Weight , Bone Density/physiology , Female , Humans , Male , Middle Aged , Obesity/physiopathology , Osteoporosis/physiopathology , Risk Factors
20.
S Afr Med J ; 84(6): 328-32, 1994 Jun.
Article in English | MEDLINE | ID: mdl-7740378

ABSTRACT

Despite the vast number of risk factors that apparently predispose to the development of osteoporosis (OP), they have not been accurately identified and given relative priority. In order to analyse possible risk factors prospectively in a local patient population with overt OP (histomorphometrically confirmed and characterised) and compare it with an appropriately matched non-OP control group (with normal bone mass on dual-energy X-ray absorptiometry), a detailed general history, risk factor analysis, dietary history and anthropometric data were obtained from 56 OP and 125 non-OP subjects. In females a positive family history of OP (P = 0.002), a fair complexion (P = 0.009), lower body mass (P = 0.02) and height (P = 0.03), no breast-feeding of babies (P = 0.006), a history of smoking (P = 0.001) and fat distribution around the waist (P = 0.009) were identified as risk factors. In males lack of exercise (P = 0.008), a history of smoking (P = 0.01), lower body mass (P = 0.04) and height (P = 0.04), a preference for salty food (P = 0.02) and fat distribution around the waist (P = 0.002) appeared to predispose. Dietary calcium, phosphorus, protein and caffeine intakes were similar in OP and control subjects, but alcohol consumption was clearly higher in both OP males (P = 0.001) and females (P = 0.01).


Subject(s)
Osteoporosis/etiology , Absorptiometry, Photon , Aged , Anthropometry , Diet Records , Female , Humans , Male , Middle Aged , Osteoporosis/epidemiology , Prospective Studies , Risk Factors , South Africa/epidemiology
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