The relationship between reproductive state and "sexually" dimorphic brain areas in sexually reproducing and parthenogenetic whiptail lizards

The anterior hypothalamus-preoptic area and ventromedial hypothalamus are sexually dimorphic in the reproductively active whiptail lizard Cnemidophorus inornatus. The anterior hypothalamus-preoptic area, which is involved in the control of male-typical copulatory behaviors, is larger in males, whereas the ventromedial hypothalamus, which is involved in the control of female-typical receptivity, is larger in females. In the parthenogenetic whiptail lizard C. uniparens, which is a direct descendant of C. inornatus and exhibits both male-like and female-like pseudosexual behaviors, both brain areas are comparable in size to those of female C. inornatus. This study was conducted to determine whether these brain areas change in size in either species or sex during a time of year when these animals are reproductively inactive, or after removal of the gonads. In male C. inornatus both brain areas changed during reproductive inactivity (either seasonally or surgically induced) and became equivalent to the size characteristic of reproductively active female C. inornatus. When corrected for brain size, the anterior hypothalamus-preoptic area was significantly smaller in intact hibernating and castrated males than in intact males from the summer breeding season. Conversely, the ventromedial hypothalamus was significantly larger in intact hibernating and castrated males than in intact males from the summer breeding season. The two brain areas were not significantly different among the groups of female C. inornatus or parthenogenetic C. uniparens. These results suggest that 1) the brain of whiptail lizards may differentiate seasonally and 2) the female state may be a neutral one to which the male brain reverts during reproductive inactivity.     

Sexual behavior and 2-deoxyglucose uptake in male red-sided garter snakes (Thamnophis sirtalis parietalis).

The [14C]2-deoxyglucose (2-DG) technique was used to study patterns of neural activity associated with the species-typical courtship behavior of male red-sided garter snakes (Thamnophis sirtalis parietalis). Males in this species court females intensely during the first month following spring emergence from their prolonged winter hibernation. Autoradiographic methods were used to measure the accumulation of radioactive label in various regions through the brains of male garter snakes that courted females, males that failed to court females, and males not exposed to females. Male garter snakes that actively courted females showed a pronounced increase in 2-DG accumulation, and therefore presumably neural activity, in the region of the anterior hypothalamus/preoptic area, relative to males that did not actively court females. Males exposed to females (regardless of whether they courted or not) showed widespread, non-specific increases in 2-DG uptake relative to males not exposed to females. The results indicate the utility of the 2-DG technique for studying complex, species-typical behaviors in vertebrates.     

Up-regulation of guinea pig myometrial beta-adrenoreceptors by systemic estradiol and progesterone

The effects of systemic administration of 17 beta-estradiol (E2) and progesterone (P) on the concentration and affinity of myometrial beta-adrenoreceptors were studied in non-pregnant, previously oophorectomized guinea pigs receiving a continuous infusion of E2, P, a combination of the two hormones, or placebo for 7 days. Myometrial beta-adrenoreceptors were characterized by using (-)-[125I-cyanopindolol as the specific beta-adrenoreceptor ligand. Compared to that in the control group, E2 administration resulted in a 7-fold increase in the density of myometrial beta-adrenoreceptors. Administration of P alone resulted in a significant increase in both beta-adrenergic receptor concentration and the receptor dissociation constant (Kd). Finally, a combination of E2 and P treatment did not result in any synergistic or additive effect for the beta-adrenergic receptors, while the Kd was twice that of the control or E2-treated animals. We conclude that systemic administration of these sex steroid hormones, directly or indirectly, modulates myometrial beta-adrenergic receptor concentrations and their ligand affinity.     

Blood pressure and retinopathy in type I diabetes

The relationship between blood pressure and diabetic retinopathy was evaluated in 249 young subjects with type I diabetes. Although hypertension is known to be associated with an increased risk for retinopathy, the effects of high-normal blood pressure are unknown. Retinopathy (158 of 249 subjects, 63%) is considerably more common in a young diabetic population than is hypertension (7 of 249 subjects, 2%). Thus, if blood pressure is important in the etiology or progression of diabetic retinopathy, levels below the hypertensive range (less than 141/90 mmHg) must be considered. The combined effect of hypertension and high-normal blood pressure (greater than 90th percentile but less than 141/90 mmHg) was studied. Elevation in diastolic blood pressure, alone, and in combination with elevated systolic blood pressure, correlated significantly (P less than 0.03) with retinopathy. The presence of high-normal blood pressure resulted in a prospectively higher occurrence of retinopathy and of progression of preexisting retinopathy. Glycohemoglobin (HbA1) and duration of diabetes also correlated with retinopathy. Both good glycemic control and maintenance of diastolic blood pressure below the 90th percentile for age may be important in relation to diabetic retinopathy.     

Dietary NaC1 during pregnancy and lactation: effect on brain angiotensin II receptors and behavior

Female rats were fed diets containing either a basal (0.12%), mid- (1%) or high (3%) level of NaCl during pregnancy and lactation. Plasma aldosterone was elevated approximately 5- and 15-fold in dams fed basal compared with either the mid- or high-NaCl diets at the end of both pregnancy and lactation (Postnatal Day 21), respectively. Dams fed basal diet and killed at the end of lactation had a higher density of angiotensin II receptors in the organum vasculosum laminae terminalis, paraventricular hypothalamus, and median preoptic nucleus than did rats fed either mid- or high-NaCl diets. Other dams, treated identically, were returned to rodent chow (approximately 0.2% NaCl) at the end of lactation for intake tests during the next week. Dams that had received basal diet did not differ from mid-NaCl and high-NaCl groups in sodium appetite induced by either acute sodium depletion or mineralocorticoid administration but showed the lowest spontaneous intake of NaCl solution.     

Relative medial and dorsal cortex volume in relation to foraging ecology in congeneric lizards

The need to locate distributed resources such as mates, food, and nests is correlated with an enlarged hippocampus in many mammalian and avian species. This correlation is believed to be a consequence of selection for spatial ability. Little is known about how such ecological needs affect non-mammalian, non-avian species. In lizards, the putative hippocampal homologues are the dorsal cortex (DC) and medial cortex (MC). We examined the relationship between foraging ecology and the size of the DC and MC in congeneric male lizards. We predicted based on the mammalian and avian literature that Acanthodactylus boskianus, an active forager that captures clumped, immobile prey would have a larger MC and DC than A. scutellatus, a sit-and-wait predator, that captures mobile prey. Our previous behavioral studies showed that A. boskianus did not differ from A. scutellatus on a spatial task but that A. boskianus was significantly better at the reversal of a visual discrimination, another task that is hippocampally dependent in mammals. In the current study, we found that, relative to telencephalon volume, the MC and DC were larger in the active forager whereas a control region, the lateral, olfactory, cortex, was similar in size between species. The current anatomical results suggest that MC and DC size is related to active foraging in lizards and, along with our previous behavioral studies, show that it is possible for this relationship to occur in the absence of evidence for species differences in spatial memory. Copyright (R) 2000 S.Karger AG, Basel     

Functional connectivity among limbic brain areas: differential effects of incubation temperature and gonadal sex in the leopard gecko, Eublepharis macularius

The neural basis of individual differences in behavior has been studied primarily by analyzing the properties of specific neural areas. However, because of the organization of the nervous system, it is also plausible that differences in behavior are mediated by differences in the interactivity or functional connectivity among brain nuclei in particular neural circuits. In the leopard gecko, Eublepharis macularius, the temperature of the egg during incubation not only determines gonadal sex, but also shapes the sociosexual behaviors, reproductive physiology, and hormone sensitivity of adult animals. In this study the effects of both incubation temperature and gonadal sex on functional connectivity among limbic brain areas were examined. Functional connectivity was assessed by analyzing covariance patterns in metabolic capacity, as revealed by quantitative cytochrome oxidase histochemistry. It was hypothesized that incubation temperature and gonadal sex affect the propensity to display aggressive or sexual behaviors by altering the functional connectivity within relevant neural circuits. The correlations of metabolic capacity between the anterior hypothalamus and both the septum and preoptic area were significant only in relatively aggressive individuals, suggesting that these circuits may regulate the phenotypic variation in aggressiveness caused by incubation temperature. The correlations between the ventromedial hypothalamus and both the dorsal ventricular ridge and septum were significant only in females, suggesting that these circuits may modulate female-typical sexual behaviors. Correlations among preoptic, hypothalamic and amygdalar areas tended to be distributed across both sexes, suggesting that there may be shared pathways underlying the expression of male-typical and female-typical behaviors.     

Hypothalamic arginine vasotocin mRNA abundance variation across sexes and with sex change in a coral reef fish

Gonadal hormones are important mediators of sexual and aggressive behavior in vertebrates. Recent evidence suggests that the peptide hormones arginine vasotocin (AVT) and its mammalian homologue arginine vasopressin (AVP) often critically mediate these gonadal hormone effects on behavior and have direct influences on behavioral variation. Behavioral differences between sexes, across reproductive states, and even among closely related species are correlated with differences in central AVT/AVP systems in many species. We report differences in hypothalamic AVT mRNA levels between distinct alternate male phenotypes and with female-to-male sex change in the bluehead wrasse (Thalassoma bifasciatum), a teleost fish. The aggressively dominant and strongly courting male phenotype has greater numbers of AVT mRNA producing cells in the magnocellular preoptic area of the hypothalamus than females. Levels of AVT mRNA within these cells in dominant males are also approximately three times female levels whereas the non-aggressive male phenotype has AVT mRNA levels approximately twice female levels. Behavioral sex change is very rapid in this species and is not dependent on the presence of gonads. Conversely, rapid increases in sexual and aggressive behavior during sex change are closely paralleled by approximate fourfold increases in hypothalamic AVT-mRNA levels. The behavioral plasticity shown by bluehead wrasses in response to social environment might be mediated in part by a neuropeptide, AVT, with changes in the gonads and gonadal hormones as the result rather than the cause of behavioral dominance. Copyright (R) 2000 S. Karger AG, Basel     

CT-Cephalometry—A study in Indian population

Determination of obstructive site in obstructive sleep apnoea (OSA) is of paramount importance is planning the management. Cephalometric evaluation of lateral X-rays when combined with clinical assessment and fibreoptic examination of the airway helps in locating the site of obstruction. The usual technique of cephalometry has been modified so as to give a better delineation of the soft tissues. Holding a 2mm card board in the mouth and using barium paste helped in more accurate calculations. Using our technique, various parameters have been quantified and a number of controls were studied and normal range derived. Further improvement in cephalometry has been done by using C.T. cephlometry topogram technique. A topogram is a scan done on a running table top cranio-caudally. Using the topogram technique 38 OSA patients were evaluated for all the parameters. The technique, its advantages over traditional cephalometry and the values obtained in the study are discussed in this paper.