The effect of maternal and fetal corticosteroids on the development of function of the pituitary-adrenocortical system.

The pituitary-adrenocortical system of rat fetuses was stimulated (larger adrenals at birth) by maternal adrenalectomy, or suppressed (smaller adrenals at birth) by implantation of an ACTH secreting pituitary tumor (MtTF4). Offspring were delivered by caesarean section and fostered to untreated females. Offspring of intact females delivered by caesarean section and normally delivered offspring of intact mothers both fostered to untreated lactating females served as controls. Body growth in the first three weeks of life was delayed in offspring of tumor bearing mothers in Control-fostered subjects as compared to the 2 other groups. At 70 days of age female offspring of the tumor implanted and adrenalectomized mothers, as well as the Control-caesarean females, had smaller adrenals than Control-fostered animals of the same sex. The adrenal size of males was not significantly affected. No significant differences were found in resting concentrations of corticosterone in plasma, although offspring of adrenalectomized mothers had high values. Suppressed adrenal response to ether stress was found in offspring of tumor bearing mothers. The supposition is that interference with maternal pituitary-adrenocortical activity during pregnancy has a long lasting effect on fetal hypothalamo-pituitary-adrenocortical system.     

Increased plasma corticosterone levels in bovine growth hormone (bGH) transgenic mice: Effects of ACTH,GH and IGF-I onin vitro adrenal corticosterone production

Previous work from our laboratory provided evidence for increased plasma corticosterone levels in mice transgenic for human and bovine growth hormone (GH). Corticosterone was elevated in both sexes, under both basal and ether-induced stress conditions. The objectives of the present study were to investigate thein vitro adrenal sensitivity to ACTH, GH and/or IGF-I in normal and bGH transgenic mice, to examine plasma corticosterone levels at different times of the day, and to determine plasma levels of ACTH in these animals. For the measurement of plasma corticosterone and ACTH levels, transgenic and normal siblings were housed 2 per cage and decapitated simultaneously within 20 seconds of the first disturbance of the cage. The corticosterone production byin vitro adrenal incubations did not differ between adrenals from normal and transgenic mice at the basal level or in the presence of different doses of ACTH. Growth hormone or IGF-I did not have any effect on corticosterone productionin vitro when given alone, and did not modify the effects of ACTH on the accumulation of corticosterone in the media. Plasma corticosterone concentrations were higher in transgenic than in normal animals in both morning and evening. Plasma concentrations of ACTH in animals killed in the morning were sharply increased in transgenic males as compared with their normal siblings. The results indicate that increased circulating levels of corticosterone in transgenic mice are not due to a potentiation of ACTH actions by GH or IGF-I, but rather to a chronic increase in plasma ACTH levels. The increase in ACTH is presumably a reflection of GH actions in the hypothalamic-pituitary system.     

Steroidogenesis in adrenal glands of young and adult female mice with hyperexpression of the Aguoti gene

Dominant mutation Agouti yellow (AY) leads to ectopic overexpression of the Agouti gene and yellow coat color in mice. Furthermore, the mutation Ay increased adrenal response to emotional stress. The study assessed whether pleiotropic effect of the mutation Ay on adrenals function was dependent on sex and age. 3- and 15-week old female C57B1/6J mice of two agouti-genotypes: Ay/a (ectopic Agouti-gene overexpression) and a/a (absence of Agouti-protein), were investigated. Cyclic AMP level (adenylate cyclase activity) and corticosterone production in adrenal isolated cells stimulated by ACTH and dibutyrul cAMP (db-cAMP) were measured. ACTH increased cAMP accumulation to the same extent in Ay/a- and a/a-mouse adrenal cells of both ages. The dibutyrul cAMP-induced corticosterone production was higher in Ay/a than in a/a-mouse adrenal cells of both ages. The ACTH-induced corticosterone production in 3-week- old Ay/a-m/CQ was lower and in 15-week old Ay/a-mice was higher than in a/a-mice of the respective ages. The ACTH- and db-cAMP-induced steroidogenesis was not changed in Ay/a-mice and decreased in a/a-mice with age. Thus, in females as well as in males, the mutation Agouti yellow did not affect adenylate cyclase activity, increased db-cAMP-induced corticosterone production and disturbed development of adrenal cortex.     

Differences in basal and stress-induced HPA regulation of wild house mice selected for high and low aggression

Male wild house mice, selected for short (SAL) and long (LAL) attack latency, show distinctly different behavioral strategies in coping with environmental challenges. In this study, we tested the hypothesis that this difference in coping style is associated with a differential stress responsiveness of the hypothalamic-pituitary-adrenal (HPA) system. SAL rather than LAL mice showed a clear fluctuation in circulating corticosterone concentrations around the circadian peak with significantly higher levels in the late light phase. LAL mice showed lower basal ACTH levels and higher thymic and spleen weights compared to SAL. Under basal conditions, glucocorticoid receptor (GR) and mineralocorticoid receptor (MR) mRNA in the hippocampus and corticotropin-releasing hormone (CRH) mRNA in the paraventricular nucleus of the hypothalamus were not different between the two lines. Forced swimming for 5 min induced high immobility behavior in LAL mice which was associated with an enhanced and prolonged corticosterone response as compared to SAL, while absolute ACTH levels did not differ. In addition, LAL mice showed an increase in hippocampal MR mRNA (but not GR) and hypothalamic CRH mRNA at 24 h after forced swimming. In conclusion, a genetic trait in coping style of wild house mice is associated with an idiosyncratic pattern of HPA activity, and greater responsiveness of physiological and molecular stress markers in LAL mice. In view of the profound differences in behavioral traits and stress system reactivity, these mouse lines genetically selected for attack latency present an interesting model for studying the mechanism underlying individual variation in susceptibility to stress-related psychopathology.     

Adrenocortical function in mice selectively bred for different sensitivity to ethanol

The adrenocortical response to ethanol, histamine and electric shock was studied in the Short-Sleep (SS) and Long-Sleep (LS) mice. The plasma corticosterone levels measured at 60 min following ethanol injection were consistently higher in LS mice (males and females) than in SS mice. The corticosterone levels determined 60 min after histamine injection (50 mg/kg) or electric foot shock were not statistically different in these two lines of mice. The initial rise of the corticosteroid after ethanol injection was identical in SS and LS mice, whereas the costicosteroid response to mild stress of saline injection was different: SS mice showed higher levels of corticosterone than LS mice at 20 and 30 min after the injection. Corticosterone increment attributable to alcohol stress clearly seemed greater in LS than in SS mice, even though the adrenals of the SS mice were 20–30% heavier than those of LS. The possible significance of these endocrine differences with respect to sensitivity to ethanol and behavioral arousal level was discussed.     

A condition dependent link between testosterone and disease resistance in the house finch.

Testosterone has recently been proposed as a link between male quality and health and the expression of sexual traits. We investigated the relationship between testosterone and measures of the individual condition and health of males in a natural population of house finches (Carpodacus mexicanus). We also conducted a captive experiment in order to test for the effects of testosterone on resistance to coccidia, which is a common parasite of house finches. Free-living males in better condition had higher testosterone levels and lower corticosterone levels than free-living males in poor condition. In our captive experiment, increased testosterone accelerated the rate of coccidial infection as compared with sham-implanted or gonadectomized males. Although the differences were not significant, free-living males infected with coccidia had lower levels of testosterone and higher levels of corticosterone than males that were not infected. Thus, experimentally elevating testosterone levels in captive males resulted in a higher percentage of infected males, while free-living males with coccidial infection had low testosterone levels. This apparent discrepancy between captive and free-living males in the association of testosterone and disease may be explained by the condition dependence of testosterone. These results suggest that the testosterone-dependent sexual traits reliably indicate male overall condition and health and, thus, females could benefit from assessing potential mates based on these traits.     

Circadian-stage-specified effects of a synthetic short chain ACTH-1-17 (HOE 433) on blood leukocytes and corticosterone secretion in mice

A synthetic short chain ACTH, ACTH-1-17 (HOE 433 = Synchrodyn 1-17), beta-ala1, lys17 corticotropin (1-17)heptadecapeptide-4-N-butylamide, was tested for activity at the anticipated circadian stage of highest adrenal corticosterone responsiveness (22-HALO) in BALB/c mice. Statistically significant dose-response relations were demonstrated both in vitro (corticosterone production by adrenals incubated in Krebs-Ringer solution) and in vivo (increases in the serum corticosterone concentration). Leukocyte counts in mice injected with this ACTH showed statistically significant decreases (as compared to controls) for all kinds of cells except the neutrophil and medium-sized lymphocyte.     

Sex-dependent effect of melatonin on the secretory activity of rat and hamster adrenal gland in vitro

Adrenal quarters from adult male or female hamsters were incubated in the presence of melatonin (10(-7) or 10(-4)M), and cortisol concentration in the incubation medium was assayed by RIA. Melatonin did not change cortisol output by adrenals obtained from the male hamsters, while a slight stimulatory effect was observed in female glands, the lower concentration of melatonin being more effective than the higher one. At both concentrations tested, melatonin notably stimulated corticosterone output by isolated rat adrenocortical cells derived from the males, and lowered corticosterone secretion by the cells obtained from the female glands only at a concentration of 10(-7) M. The lower concentration of melatonin increased ACTH (0.1 mU.ml-1)-stimulated corticosterone output by the cells of male and female rat adrenals. The pineal hormone was ineffective at a concentration of 10(-4) M, as well as in the presence of a higher dose of ACTH (1.0 mU.ml-1). These findings indicate a distinct sex-dependent effect of melatonin on in vitro cortisol and corticosterone production, and demonstrate that the modulatory effect of melatonin of the secretion of steroid hormones is more effective at lower concentrations.     

Adrenal glands of mouse and rat do not synthesize androgens.

Human adrenal glands produce considerable amounts of the C-19 steroids dehydroepiandrosterone (DHEA) and androstenedione. To investigate the capability of rodent adrenals to produce these steroids, cell suspensions of mouse and rat adrenal glands were incubated in the absence and presence of adrenocorticotropic hormone (ACTH). Corticosterone levels in the incubation medium increased dramatically in the presence of ACTH, but no significant amounts of 17-hydroxyprogesterone or androstenedione could be detected. This indicates that the adrenals of rat and mouse lack the enzyme 17 alpha-hydroxylase. Absence of plasma cortisol in the presence of high levels of corticosterone confirmed these data. Plasma levels of androstenedione were significantly decreased in castrated male rats as compared to levels observed in intact males, showing the contribution of the testes to the plasma content of androstenedione. Very low levels of androstenedione were observed in female, male and castrated male mice. Plasma concentrations of DHEA were not detectable in intact and castrated male mice and rats. It is concluded that rat and mouse lack the enzyme necessary to synthesize adrenal C-19 steroids and that the adrenals in these animals, therefore, do not contribute to plasma levels of androstenedione and DHEA.     

Role of sex dimorphism in the pharmacological action of etimizol

It has been shown that in female rats the level of ACTH, corticosterone in the blood, relative mass of adrenals, maintenance of T3, T4 in the serum and liver was significantly higher, but the activity of liver enzyme microsomes system was lower than in males; no sex differences were observed in myocardial creatine phosphokinase system. The influence of the etimizol on the female rats significantly speed up amidopyrine N-demethylation and biotransformation of hexobarbital. In males these systems react less on etimizol, but it reduces the speed of amidopyrine N-demethylation.     

Long-term effects of accelerated or delayed sexual maturation on reproductive output in wild female house mice (Mus musculus)

The effects of acceleration and delay of puberty in female house mice on survival and reproduction were tested using 6 experimental groups: (1) control females mated at the time of first oestrus, (2) females mated at weaning, (3) females treated with male urine starting at weaning and mated at first oestrus, (4) females housed in groups and mated at first oestrus, (5) females housed alone, treated with urine from grouped females and mated at first oestrus, and (6) females housed alone and mated at 68 days of age. Females caged with males at weaning or treated with male urine and mated at puberty had lower rates of survival to 180 days of age, but did not differ in rates of fertility from mice in the other four treatments. Those females that were housed with males from weaning or treated with male urine also had smaller total numbers of litters, fewer total young, and smaller average litter sizes than did females for which the age of mating was delayed, by grouping or treatment with urine from grouped females, or by being held until age 68 days before mating. Control females mated at first oestrus generally were intermediate or did not differ from the male treatments on these dependent variables. There were no differences in the average number of female young/litter across the 6 treatments. However, females that were delayed in age of first mating had significantly more male young/litter than did females that were accelerated in their sexual development or control females.(ABSTRACT TRUNCATED AT 250 WORDS)     

The interaction of cadmium-binding proteins (Cd-bp) and progesterone in cadmium-induced tissue and embryo toxicity.

Previous work indicates that a dimer of Cd-thionein (Cd-bp-D, 19,000 MW) is involved in the hereditary resistance to Cd-embryotoxicity seen in the inbred NAW/Pr (NAW) mouse strain. Cd-bp-D is not detected in virgin females after Cd exposure and is detected only after the first 24 hours of exposure to Cd in an inbred strain (C57BL/10ChPr) susceptible to Cd-induced embryotoxicity (Wolkowski, '74; Wolkowski-Tyl, '78). Since progesterone (P) is critical for maintenance of pregnancy in mice, we have studied the possible relationship between this hormone and Cd-bp-D production. As a model system, was examined effects of Cd treatment on Cd-bp synthesis in NAW males. It was anticipated that this model could provide information bearing not only on the relationship between P and Cd-bp-D production, but also on that between Cd-bp-D and Cd toxicity, since a single sc injection of CdCl2 causes typical testicular hemorrhagic necrosis in NAW males, and these animals make only metallothionein and not Cd-bp-D. NAW males were, therefore, given P (0.1 g/Kg bw) and then exposed to Cd. Sephadex gel chromatography (G-200) of liver cytosol from animals killed 24 hours later detected only Cd-bp-D. Testes of these males did not show hemorrhagic necrosis. Since the adrenals of male mammals release P in response to stress, NAW males were stressed by repeated sesame oil or propylene glycol injections (5 ml/Kg bw), or the adrenal was stimulated directly with injections of ACTH (100 IU/Kg bw) for seven days prior to Cd exposure. All methods tested which significantly elevated serum P levels (as confirmed by radioimmunoassay), also resulted in production of Cd-bp-D and absence of testicular hemorrhage in Cd-treated NAW males. Suppression of P release by injection of dexamethazone or corticosterone or by adrenalectomy resulted in testicular hemorrhage and production of only metalicthionein after Cd exposure. The relevance of the interaction between P, Cd-bp-D and protection against Cd-induced toxicity seen in the model system was supported by analysis of serum P levels in pregnant females; elevated levels were seen in resistant (NAW dams on day 10 of gestation and significantly lower levels seen in dams from a Cd-sensitive strain.     

Seasonal changes in testosterone and corticosterone levels in four social classes of a desert dwelling sociable rodent

Animals have to adjust their physiology to seasonal changes, in response to variation in food availability, social tactics and reproduction. I compared basal corticosterone and testosterone levels in free ranging striped mouse from a desert habitat, comparing between the sexes, breeding and philopatric non-breeding individuals, and between the breeding and the non-breeding season. I expected differences between breeders and non-breeders and between seasons with high and low food availability. Basal serum corticosterone was measured from 132 different individuals and serum testosterone from 176 different individuals of free living striped mice. Corticosterone and testosterone levels were independent of age, body weight and not influenced by carrying a transmitter. The levels of corticosterone and testosterone declined by approximately 50% from the breeding to the non-breeding season in breeding females as well as non-breeding males and females. In contrast, breeding males showed much lower corticosterone levels during the breeding season than all other classes, and were the only class that showed an increase of corticosterone from the breeding to the non-breeding season. As a result, breeding males had similar corticosterone levels as other social classes during the non-breeding season. During the breeding season, breeding males had much higher testosterone levels than other classes, which decreased significantly from the breeding to the non-breeding season. My results support the prediction that corticosterone decreases during periods of low food abundance. Variation in the pattern of hormonal secretion in striped mice might assist them to cope with seasonal changes in energy demand in a desert habitat.     

Anxiety and panic responses to a predator in male and female Ts65Dn mice, a model for Down syndrome

Hyperactivity is a feature frequently reported in behavioral studies on the Ts65Dn (TS) mouse, the most widely accepted model of Down syndrome, when tested in anxiety-provoking situations such as the plus-maze and the open-field tests. Although this behavior could be considered as an expression of reduced anxiety, it has been considered as a consequence of a lack of behavioral inhibition and/or reduced attention. This study addressed anxiety and panic behavior of male and female TS mice by evaluating serum biochemical parameters and behavioral responses to a predator in the Mouse Defense Test Battery. Flight, risk assessment, defensive threat/attack and escape attempts were measured during and after rat confrontation. When confronted to a rat, male TS mice showed similar biochemical and behavioral responses as control mice. However, female control and TS mice presented lower serum adrenocorticotropic hormone (ACTH) levels under basal conditions and higher corticosterone levels after predator exposure than male mice. Thus, there was a larger increase in ACTH and corticosterone levels after predator exposure with respect to the undisturbed condition in females than in males. In addition, TS females showed some alterations in defensive behaviors after predator exposure. The results emphasize the need to consider gender as a confounding factor in the behavioral assessment of TS mice.     

Severe pulmonary hypertension in aging female apolipoprotein E-deficient mice is rescued by estrogen replacement therapy

Corticotropin-releasing factor overexpressing (CRF-OE) male mice showed an inhibited feeding response to a fast, and lower plasma acyl ghrelin and Fos expression in the arcuate nucleus compared to wild-type (WT) mice. We investigated whether hormones and hypothalamic feeding signals are impaired in CRF-OE mice and the influence of sex. Male and female CRF-OE mice and WT littermates (4–6 months old) fed ad libitum or overnight fasted were assessed for body, adrenal glands and perigonadal fat weights, food intake, plasma hormones, blood glucose, and mRNA hypothalamic signals. Under fed conditions, compared to WT, CRF-OE mice have increased adrenal glands and perigonadal fat weight, plasma corticosterone, leptin and insulin, and hypothalamic leptin receptor and decreased plasma acyl ghrelin. Compared to male, female WT mice have lower body and perigonadal fat and plasma leptin but higher adrenal glands weights. CRF-OE mice lost these sex differences except for the adrenals. Male CRF-OE and WT mice did not differ in hypothalamic expression of neuropeptide Y (NPY) and proopiomelanocortin (POMC), while female CRF-OE compared to female WT and male CRF-OE had higher NPY mRNA levels. After fasting, female WT mice lost more body weight and ate more food than male WT, while CRF-OE mice had reduced body weight loss and inhibited food intake without sex difference. In male WT mice, fasting reduced plasma insulin and leptin and increased acyl ghrelin and corticosterone while female WT showed only a rise in corticosterone. In CRF-OE mice, fasting reduced insulin while leptin, acyl ghrelin and corticosterone were unchanged with no sex difference. Fasting blood glucose was higher in CRF-OE with female > male. In WT mice, fasting increased hypothalamic NPY expression in both sexes and decreased POMC only in males, while in CRF-OE mice, NPY did not change, and POMC decreased in males and increased in females. These data indicate that CRF-OE mice have abnormal basal and fasting circulating hormones and hypothalamic feeding-related signals. CRF-OE also abolishes the sex difference in body weight, abdominal fat, and fasting-induced feeding and changes in plasma levels of leptin and acyl ghrelin.     

Mating compatibility and competitiveness of transgenic and wild type Aedes aegypti (L.) under contained semi-field conditions

We conducted the world??s first experiments under semi-field conditions (ACL-2 field house) to assess the mating competitiveness of genetically sterile RIDL male mosquitoes (513A strain). The field house is a state-of-the-art, fully-contained trial facility, simulating the living space for a household of 2?C4 people in Peninsular Malaysia. Ten genetically sterile RIDL male A. aegypti mosquitoes competed with ten wild type males inside this field house to mate with ten wild type females. Hatched larvae from mated females were screened under a fluorescent microscope for genetic markers to determine if they were fathered by RIDL male or wild type male, and all results were cross-checked by PCR. Two such experiments were conducted, each repeated sufficient number of times. All strains were on a Malaysian lab strain background for the first experiment, while the RIDL males alone were on a recently-colonised Mexican strain background for the second experiment. A total of 52 % of the matings were with RIDL males in the first experiment, while 45 % of the matings were with RIDL (Mexican) males in the second experiment. Statistically, this is not significantly different from 50 % of the matings expected to take place with RIDL males if the latter were as competitive as that of the wild type males. This shows that A. aegypti RIDL-513A has excellent mating competitiveness under semi-field conditions, verifying earlier trends obtained in small lab cages. We also observed high mating compatibility between recently-colonised Mexican RIDL males and lab-reared Malaysian wild type females.     

Food supplementation and possible mechanisms underlying early breeding in the Florida Scrub-Jay (Aphelocoma coerulescens)

Food supplementation studies demonstrate the importance of resources in the timing of reproduction. Studies of Florida Scrub-Jays (Aphelocoma coerulescens) found that supplemented jays bred earlier than unsupplemented jays and that protein may play a critical role. In this study, free-living scrub-jays were provided with supplemental diets high in fat and protein (HFHP) or high in fat and low in protein (HFLP). Jays in both treatments bred earlier than unsupplemented controls (CNT), but HFHP-supplemented jays bred earlier than HFLP jays. To assess possible mechanisms, we measured testosterone (T) in males, estradiol (E2) in females, and corticosterone (CORT) in both. HFHP males had higher T than HFLP and CNT males, but treatment did not affect E2 levels of females. Pilot studies of scrub-jays in suburban environments suggest that the spatial and temporal predictability of food may influence corticosterone (CORT) levels. Suburban jays have year-round access to human-provided foods and breed earlier than wildland jays; thus, we compared CORT in all treatments in the natural site (wildlands) with those of suburban jays. CORT levels of suburban jays were lower than HFLP, HFHP, and CNT jays. HFHP-supplemented jays had lower CORT levels than those of HFLP and CNT jays. The observed differences in the timing of breeding, both between suburban and wildland populations and between experimental groups in the wildlands, may result from differences in the spatial and temporal predictability of food, and the nutritional differences in diets. Because CORT can negatively affect the reproductive axis, we postulate that nutrient availability, the predictability of food, CORT levels, and initiation of reproduction are inextricably linked.     

Age and food deprivation affects expression of the glucocorticosteroid stress response in Magellanic penguin (Spheniscus magellanicus) chicks

We examined how the glucocortical stress response in free-living Magellanic penguin (Spheniscus magellanicus) chicks changes with age and whether adrenocortical function of chicks within a brood varies in relation to food provisioned by adults. Chicks showed little corticosterone response to capture stress shortly after hatching, an intermediate response around 45-d posthatch, and a robust stress response near fledging. However, in response to an adrenocorticotropic hormone (ACTH) challenge, hatchlings were capable of secreting corticosterone at adult-like levels. The larger sibling in broods of two showed a similar gradual stress-response development pattern. In contrast, by day 45, when differences in body condition were well established between siblings, the smaller, food-deprived chicks significantly increased baseline levels of corticosterone but showed normal stress-induced levels. Near fledging, baseline levels had returned to normal, but stress-induced levels were lower than expected. Similar to altricial species, normally developing semialtricial Magellanic penguin chicks do not express a robust corticosterone stress response until near fledging. Chronic stressors such as food deprivation cause corticosterone use to be up-regulated earlier than expected. However, in cases of extended chronic stress, down-regulation may ensue, thus avoiding the negative effects of chronically elevated levels of corticosterone.