Sexual cranial dimorphism in malnourished rats treated with growth hormone.

One hundred and sixty two Holtzman rats of both sexes were malnourished during suckling and post-weaning periods. Some of them received periodic injections of growth hormone. After sampling, at 56 days of age, skulls were cleaned and measured. Differences within and between sexes were estimated by Mahalanobis D2 distances. Normal cranial differentiation between sexes (SCD) was decreased by malnutrition and restored by growth hormone treatment. The effect of the growth hormone on skull size was larger in malnourished males than females. This differential increment between sexes explains how growth hormone acted on the restoration of SCD.

Growth of functional cranial components in Saimiri sciureus boliviensis (Cebidae): a longitudinal study.

Ten male Saimiri sciureus boliviensis (Cebidae) born at the Centro Argentino de Primates (CAPRIM) were divided into a control group (five animals fed ad libitum on a 20% protein diet) and an undernourished group (five animals fed ad libitum on a 5% protein diet) at weaning (seven months old). Each animal was radiographed monthly from both later-lateral and dorsal-ventral views, from the first to the third year of age. The length, width and height of the optic, respiratory, and masticatory components of the face and anterior neural, middle neural, and posterior neural components were measured in the radiographs. Volumetric (VI) and morphometric (MI) indices were calculated for each component. Correlations and simple linear regressions with respect to age were performed. In the face, two components -respiratory and masticatory- showed the greatest growth rate. In the neurocranium, the middle neural component grew most, approaching the rate observed for the component of the lowest growth in the face (optic). The anterior neural and posterior neural components showed the lowest -although significant- growth rates of the skull. The determination coefficients showed that linearity explained from 12% (posterior neural component) to 74% (masticatory component) of the variation, the remainder being attributed to shape changes and noise effects. The neurofacial rate showed a high level (80%) of nonlinearity since the neurocranium grew almost 1/3 with respect to the face. The morphometric indices showed that only the masticatory component was linear to the face. While the respiratory component grew more, the optic one grew less than the whole face. Only the anterior neural component kept linearity with the neurocranium. While the middle neural component grew more, the posterior neural one grew less than the whole neurocranium. Significant alterations due to undernutrition were seen in both major components. While the three facial and the anterior neural components showed correlation coefficients lower -but significant- than in controls, in the remaining indices -morphometrics included- the correlation values were abruptly broken. The slopes of the regressions which remained significant showed that undernutrition affected mainly the components with greater growth rates (respiratory, masticatory, and middle neural). Secondarily affected were those with lower growth rates (optic, anterior neural and posterior neural), despite their function and according to the histology of the organs they support and protect.

Influence of intrauterine blood supply on cranial growth and sexual dimorphism at birth.

Many experimental studies of the effects of placental blood flow on growth exist. Nevertheless, few of them deal with the relationship between impaired uterine blood supply, and cranial growth and sex differentiation. The object of the present study was to investigate the impact of intrauterine growth retardation (IUGR) on sexual cranial dimorphism in the newborn rat. Three experimental groups were employed: (a) control; (b) operated (IUGR), in which both uterine vessels were partially bent in the 15th day of gestation; and (c) sham-operated, identical to (b) but without vessel bending. At birth, pups were weighed, and their bodies and craniums, measured. In the cases of asymmetric distributions, data were logarithmically transformed. A multi-way analysis of variance (ANOVA) and LSD post-hoc tests were used to find out differences between experimental groups and sex. Controls had significant sex differences in body and cranial variables. The prenatal growth of IUGR pups was significantly inhibited. Body and facial variables were more affected than the neurocranial ones. Undernutrition produced body and cranial size changes. Since IUGR affected male more than female growth, sex dimorphism was clearly reduced in all variables which were dimorphic in controls.

Body growth and food intake in moderately and severely malnourished rats.

A longitudinal study with eighty-six rats (Rattus norvegicus albinus var. Wistar) of both sexes was made. The aim was to express adaptability to malnutrition in terms of Age-of-Fitness Point (AFP) and Trend-to-Fitness Stage (TFS). The AFP means the age in which both control and malnourished animals show the same Relative Food Intake (RFI) value, expressed in mg of food intake per g of body weight. The TFS means the percent of RFI reached by the malnourished animals at a given age stage. A TFS=70 for example, means that the animals have to gain 30% of RFI to reach its AFP. Growing animals were submitted to one of the following treatments: control (fed on a stock diet ad libitum), moderate malnutrition (fed on 1/2 of the daily stock diet of a control of the same age and sex) and severe malnutrition (fed on 1/3 of the mentioned diet). Body weight and food intake of all of the animals were registered every ten days, when they were from 20 to 80 days old. Relative Food Intake (RFI) was calculated dividing the food intake (mg) of each animal/day by its respective body weight (g). The RFI data series belonging to each sex and treatment was obtained. The significance of the three independent variables (age, sex, and nutrition) was tested by multiple regressions. Covariation and degree of linearity between RFI and age were tested by simple correlation and simple regression tests. The intercepts of the regressions were all significant. For both sexes they were greater in controls than in the moderately malnourished group, in the latter being greater than in the severely malnourished group. The slopes were significant and negative in all of the groups. While, in males and females, control and moderately malnourished rats showed little differences, the severely malnourished slopes were, respectively, 3.2 and 2.4 times lower than in controls. In controls there were sexual differences for RFI correlated with age which were not present in the malnourished groups. The AFP was calculated by extrapolation: 80-90 days of age in males, with RFI of 80 mg/g, and 100-110 days of age in females, with RFI of 70 mg/g. In males TFS was 29.5% and 88.6 % in moderate and severe malnutrition, respectively. In females these values were 9.1% and 63.2%, respectively. Sexual dimorphism in TFS was significant in the moderately malnourished animals and nonsignificant in the severely malnourished ones.

[Growth and sex dimorphism in school children according to their father's occupation]. / Crecimiento y dimorfismo sexual de escolares según la ocupación laboral paterna.

A cross-sectional morphometric study on 569 school children from the city of San Clemente del Tuyú (Buenos Aires, Argentina) has been performed. The sample was subdivided into 28 subgroups according to the age range (7-13 years old), sex, and occupational status -low or high- of the fathers. Body weight, height, sitting height, and head and arm circumferences were measured. Statistics of analysis of variance (ANOVA) and Tukey test for unequal sample sizes were performed at each stage of age. Both males and females belonging to the lower social status showed a general decrement in growth: shortening in leg length was evident. Since the girls from both occupational status showed -in general terms-hypothesis of "better canalization of the females" has been corroborated by the present work.

[Growth in school children of Villa IAPI (Quilmes, Buenos Aires, Argentina)]. / Crecimiento en escolares de Villa IAPI (Quilmes, Buenos Aires, Argentina).

Growth in schoolchildren of Villa IAPI--a poor neighborhood placed near Buenos Aires (Argentina)--were cross-sectionally studied. Six hundred and forty five--291 males and 354 females--children from six to twelve years old were weighed (W), and the standing (StH) and sitting (SiH) heights, the head (HC) and the arm (AC) circumferences, and the triceps (TS) an the subscapular (SS) skinfolds were measured. The muscular braquial circumference (MC), and the length of the inferior segment of the body (IS) were also calculated. All of the measurements were transformed to "z" scores. It was observed that in all cases--except for 11 year-old females--both W and StH were diminished. This trend was stronger in males than in females. Both SiH an HC did not show differences with respect to local growth standards. Skinfold values however, were always greater in Villa IAPI children--except SS in 9 to 12 year-old males, and in 12 year-old females--than those of normal standards, Such differential growth pattern suggests that two joined strategies--for protection and adaption to unbalanced environment--actually acted in the Villa IAPI population.

An ontogenetic approach to facial variation in three Native American populations.

Various explanations have been formulated regarding high levels of craniofacial variation among Native American populations but the contribution of developmental processes to the establishment of these patterns of variation remains unknown. In this study, we compare facial morphology in ontogenetic series of three Native South American populations, one hunter-gatherer group and two farmer groups, in order to test the null hypothesis that indicates that the pattern of facial differentiation between populations does not change during ontogeny. If diet-related factors contribute to outline facial morphology, it is likely to find greater differences between hunter-gatherer and both farmer groups than between two groups of farmers and this differentiation is expected to increase with age, especially in those structures that are influenced by the mechanical load of mastication. According to our results, hunter-gatherers clearly differ from the two groups of farmers. Non-heritable factors linked to diet, such as nutritional content of food, may increase differentiation across ontogeny in some cases. However, as hunter-gatherers were clearly separated from farmer populations during entire postnatal ontogeny, an important proportion of size variation may not necessarily reflect eco-sensitive changes. Consequently, the hypothesis cannot be completely rejected.

The effects of race, sex, and nutrition on craniofacial differeniation in rats. A multivariate analysis.

Wistar and Holtzman rats were fed (a) control diet ad libitum (controls); (b) restricted control diet (undernourished); and (c) low-protein diet ad libitum (malnourished), from weaning to 70 days of age. Mahalanobis D2 distances between cranial groups were assessed. Besides, differences among traits were assessed by the analysis of variance and Tukey test. The relative influence of each factory yielded a decreasing sequence: protein-calorie malnutrition (PCM)-Protein deficit (PD)-race-sex. However, this sequence differed between races. The significant sexual dimorphism in Wistar controls disappeared because of PCM and PD. Race and sex, race and nutrition, and race, sex, and nutrition interacted. Traits were classified into: (a) specific, (b) nonspecific, and (c) invariable. The specific race traits were alveolar length and foraminal width. The specific nutritional traits were neurocranial and splanchnocranial length and heights, alveolar and neurocranial widths, and the neuro-splanchnocranial index (NSI) and the neurocranial vertico-transversal index (NVTI). There were no specific sexual traits. It was concluded that nutritional factors can modify a taxonomic distance in three different ways: (a) evoking morphological differences among populations of the same racial group, (b) altering differences among racial groups, and (c) modifying the pattern of sexual dimorphism of a population. It is suggested that craniological studies should take into account only the set of specific traits, disregarding both specific traits due to other factors and nonspecific ones.

Growth of the functional components of the rat skull and its alteration by nutritional effects. A multivariate analysis.

Weanling male Holtzman rats were subjected to each of the following nutritional treatments: malnutrition-recuperation; undernutrition; and undernutrition-recuperation. The rats were sacrificed when they were 49 days old, and dimensions of each one of the neurocranial, respiratory, and masticatory components were measured. Each component was compared with its counterpart in control rats (21, 28, 35, 42, and 49 day-old) by means of Mahalanobis D2 distances. The same functional components of 49 day-old control skulls were compared with their counterparts in younger control skulls. The means of the chosen cranial dimensions were compared by Tukey tests. Two periods of craniofacial development were identified. In the first, both facial components showed a similar growth that was greater than the neurocranial growth. In the second period, the growth of the masticatory component was greater than that of the respiratory component, which in turn, was greater than that of the neurocranial component. Nutritional deficiencies delayed the growth of the masticatory component more than that of the neurocranial component, which, in turn, was delayed more than that of the respiratory one. About 7% of the dimensions measured were insensitive to both growth and nutrition; 31% were insensitive to nutrition; and 62% were modified by nutrition. Craniofacial development in the rat seems to be a process more complex than what has been generally accepted. A nutritional stress may alter the relative growth between the facial functional components to a greater extent than that between the major functional components; viz. the neurocranium and the splanchnocranium. The cranial dimensions studied were classified according to their sensitivity to growth and/or nutrition into invariable, nutritionally stable, and nutritionally unstable traits.

Craniofacial development of the rat with respect to vestibular orientation.

The vestibular orientation was applied in the present work. Its purpose was to contribute to the knowledge of the craniofacial development of the growing rat. Sagittal cuts were made in 91 crania from Wistar rats (44 males and 47 females) at 8, 15, 30 and 60 days of age. The x and y coordinates of the sagittal points were determined. The sagittal intersection of the vestibular plane was employed as the abscissa and its perpendicular at the mid point of the external semicircular canal (mesovestibion) as the ordinate. Cranial diagrams were constructed in which the length of the sagittal projection of each bone and its angulation with respect to the abscissa were measured. It was confirmed a progressive evolution towards orthocrania due to the bone rotation complexes, which characterized three cranial regions: the anterior region (frontal-ethmiodal-facial complex) with trigonometric rotation; the mid region (parietal-sphenoidal complex) remained stable, and the posterior region (interparietal-occipital complex) with clockwise rotation. Each complex had its own pattern of rotation. The causal factors reside in the differential increment between the functional components: (a) neurocranium-splanchnocranium, (b) neurocranium-cervical column, (c) dorsal neurocranium-basilar neurocranium and (d) dorsal splanchnocranium-basilar splanchnocranium. Its etiology obeys to the functional requirements induced by the adaptation of the modern rodents.

The influence of experimental deformation on craniofacial development in rats.

Cranial deformation was produced experimentally in rats 8 to 40 days old for the purpose of studying the rotation of the craniofacial bones and the modification of the growth rates of the functional cranial components. One hundred and twenty four skulls (65 males and 59 females) were employed, classified as: deformed , deformed-hydrocephalic, sham-operated and controls. A midsagittal diagram was drawn for each skull and the angle subtended by each bone with respect to the vestibular plane was measured. Growth indices were worked out for both the neural skull and the facial skull. Deformation altered the rotation of the parietal, interparietal and basisphenoidal bones and restricted the rotation of the fronto-ethmo-facial complex. Alteration of the longitudinal growth rates of the dorsal and basilar components of the neurocranium and the splanchnocranium produced the persistence of the klinorynchal state.

Effects of maternal food restriction during lactation on craniofacial growth in weanling rats.

Adult Holtzman rats were submitted during suckling period to a food restriction with or without protein or carbohydrate restoration. Twenty-one-day-old weanling pups were compared with controls of 9, 13, 17, and 21 days of age. Lateral craniofacial roentgenographies were taken. The length in midsagittal plane of each bone and its angle with respect to the vestibular line were measured in males. In females, the brain and the left masseter muscle were weighed, and the muscle/brain ratios (neuromuscular index) were calculated. Food restriction altered skull size and shape. Size changes were due to arrested lengths in all studied skull bones. Shape variation was evident by orthocephalization changes, reflected in angulation changes of bones belonging to the frontoethmofacial (frontal, nasal, and maxillary bones) and to the occipitointerparietal (interparietal bone) complexes. Partial restorations by both protein or carbohydrate supplementation were found. Nutritional stresses during lactation affected orthocephalization through an altered growth ratio between two soft tissues functionally associated to the craniofacial complex: brain and masticatory muscles.

Variations in sexual dimorphism in the skulls of rats subjected to malnutrition, castration, and treatment with gonadal hormones.

Two groups of weanling rats were subjected to malnutrition, one with periodic injections of testosterone (males) and the other with estradiol (females). Two other groups (castrated males or castrated females) received normal feedings. In control animals, the relative weights (mg/gm body weight) of testes, seminal vesicles, and ovaries were greater than in malnourished rats. However, relative weights of those organs in hormone-treated, malnourished animals were greater than in those subjected to malnutrition alone and still greater than in controls. Normal sexual cranial dimorphism (SCD) was decreased 16% by male castration, 23% by malnutrition, and 83% by estradiol treatment in malnourished females. On the other hand, normal SCD was increased 20% by female castration and more than 200% by testosterone treatment in malnourished males. All monosexual comparisons corroborated the bisexual range of distances found. Testicular but not ovarian secretions seemed to influence sexual cranial dimorphism. Malnutrition delayed SCD because of a deficiency of testosterone level in stressed males. It is suggested that estradiol in females may counteract sexual cranial development and that its inhibitory effect may be additive to the testosterone deficit evoked by malnutrition.

Influence of food restriction during gestation on craniofacial growth of the weanling rat.

Holtzman rats were subjected to food restriction during gestation or lactation, or both periods (overall stress). At weaning, male pup skulls were measured and female brains and cranial masticatory muscles were weighed and a neuromuscular index was calculated. It was found that gestational protein-calorie malnutrition (PCM) without suckling restoration accounted for about 30% of the growth delay observed under overall stress. That effect disappeared after a normal suckling restoration. Under the same conditions of maternal food restriction in both periods, growth delay in the offspring was greater during lactation than gestation. As in lactation, craniofacial changes during gestational restriction were due to an adjustive response of bone growth to PCM. This response seemed to accrue from an altered relationship between the growth of the brain-less sensitive and highly restorable-and the growth of the masticatory muscles-more sensitive and less restorable. Some degree of delay in orthocephalization would be the skeletal outcome of such adjustive neuromuscular response.

The influence of gonadic hormones on skull differences in rats malnourished during lactation.

One hundred and twenty five Holtzman rats of both sexes were submitted to malnutrition during suckling with or without periodic injections of testosterone enantate in males and estradiol valerianate in females. Ten cranial measurements were made, and morphological differences within and between sexes were calculated by multivariate Mahalanobis D2-distances. Malnutrition delayed the cranial difference between sexes, which was restored by hormonal treatment. Testosterone arrested the skull size difference between sham and malnourished males. Estradiol stimulated the skull size difference between sham and malnourished females. This counteracting effect indicates that at early ages, both hormones stimulate sexual cranial dimorphism when a protein-calorie malnutrition acts on both sexes.

Cranial growth in Saimiri sciureus (Cebidae) and its alteration by nutritional factors: a longitudinal study.

Ten male Saimiri sciureus boliviensis (Cebidae), born at the Centro Argentino de Primates (CAPRIM), were grown in captivity. At weaning (6 months old), five individuals were fed ad libitum on a 20% protein diet (controls). The other five animals were fed ad libitum on a 5% protein diet (malnourished). Animals were radiographed monthly. The length, width, and height of the anterior, middle, and posterior components of the neurocranium, and those of the masticatory, respiratory, and optic components of the face were measured. A pattern of high growth rate was observed in both the three facial and the middle neural components. The anterior and posterior neural components showed a pattern of low rate of growth. The growth behavior of each variable was also different. Lengths grew more than widths and heights in the facial components, whereas widths grew more than heights and lengths in the neurocranium. Malnutrition delayed growth in size and altered the normal shape changes. High-patterned variables, such as masticatory and respiratory lengths, and the anterior and middle neural widths were particularly affected. The masticatory and the middle neural components underwent the greatest growth arrest. The optic and the respiratory components suffered a mild effect. The anterior and the posterior neural components were affected to a lesser degree.

Orthocephalization in the postweaning squirrel monkey.

Twenty male squirrel monkeys (Saimiri sciureus boliviensis) raised in captivity were allotted to one of the following groups: weanling control (C6) sampled at 6 months of age; young control (C24) fed ad libitum on a control diet and killed at 24 months of age; and malnourished (M24) fed ad libitum on a low-protein diet and sampled at 24 months of age. Cranial points and the lateral semicircular canals were marked. On each skull, a strict lateral teleradiograph was taken, and the lengths of the midsagittal chords and their angles with respect to the vestibular line were measured. Age changed the lengths in about 70% of the chords and more than 50% of the angles. Malnutrition arrested about 50% of the lengths, but the angles were practically not affected. It is concluded that the postweaning Saimiri sciureus undergoes orthocephalization according to a general pattern already observed in rodents and suggested for pongids. Postweaning malnutrition affected growth in size but not shape changes related to the orthocephalization of the Saimiri skull.

Effects of post-weaning malnutrition on the weight of the head components in rats.

Female Holtzman rats, weighing about 40 g, were given one of each of the following treatments: (a) 6% protein diet ad libitum throughout; (b) 6% protein diet for 2 weeks followed by 25% protein diet ad libitum for 2 weeks; (c) 25% protein diet fed in amounts isocaloric with treatment (a) and (d) 25% protein diet ad libitum throughout. These treatments were applied from weaning (21 days) to 49 days of age. Selected pairs of treatments were compared in order to elicit the influences of protein-calorie malnutrition, malnutrition recuperation, and protein deficit on both the absolute and relative weights of the following head components: skin (plus subcutaneous adipose tissue), muscular mass, eyeballs, skull, and encephalon. DNA and total protein concentrations in encephalon and muscle were also measured. The head components were classified into stables, for which growth decreased less than that of the head as a whole, and variables, for which growth decreased more than that of the head as a whole. The eyeballs, encephalon, and skull behaved as stable components, whereas the muscular mass and skin did so as variable components. The well-known modifications in the craniofacial growth pattern evoked by nutritional deficiencies were explained by the different reactions shown by the encephalon, functionally associated with the neurocranium, and the skeletal muscles, functionally associated with the masticatory apparatus. The changes observed in DNA concentration suggest that protein deficit delayed muscle growth through a decrease in cell size rather than a decrease in cell number in the muscular fibre.

Effects of protein-calorie malnutrition during suckling and post-weaning periods on discontinuous cranial traits in rats.

The influences of protein-calorie malnutrition (PCM), and sex during lactation and post-lactation on the frequencies of 25 discontinuous cranial traits (DCT), were investigated in Holtzman rats. Significant differences were observed in about 20% of the traits. Those traits were: the interfrontal fusion, the posterior incurvation of the palatine border, the double maxillary foramen, the double posterior palatine foramen, and the double frontal foramen. Total PCM was the nutritional factor which showed the greatest influence on the variability of the DCTs. It was followed, in decreasing order, by the PCM imposed during post-lactation and lactation. Sex had more influence than early PCM but less than late PCM. It is concluded that despite their apparent stability, a substantial number of DCTs were altered by both biological (like sex) and environmental factors (like nutritional deficiencies) imposed at different stages of postnatal development.

Effect of age, sex and nutrition on discontinuous traits of rat skull.

The effect of biological (age and sex) and environmental factors (protein-calorie malnutrition and protein deficit) on 24 discontinuous cranial traits was investigated in Holtzman rats. The traits affected were (a) the interfrontal fusion, by age and nutrition; (b) the double posterior palatine foramen, by sex and nutrition, and (c) the double maxillary foramen, by nutrition. It is concluded that most of the traits studied were fairly stable. Nevertheless, it must be pointed out that taxonomic studies based on discontinuous cranial traits should be interpreted with care due to the influence of environmental and biological factors on the phenotypic expression of some of them.