Urolithiasis in rats consuming a dl bitartrate form of choline in a purified diet

Urolithiasis appeared in rats maintained to study the effects of nutrients and methylmercury on development and aging. After a year, the mortality rate was approximately 10%, and by 2 years, it had increased to nearly 30%. Clinical signs and urinary tract pathology were examined as a function of diet, duration on diet, gender, methylmercury exposure, genetics, and other potential risk factors by using survival analyses and qualitative comparisons. Urolithiasis in female rats appeared 15 weeks after beginning a purified diet and after 5 weeks for male rats. After 97 weeks, the mortality rate of female rats was 22% and for male rats was 64%. Lifetime urolithiasis-associated mortality was about 2% in a group of rats that consumed the contaminated diet for < 30 weeks. No urolithiasis occurred in siblings or cohorts of the rats described here that were maintained on a standard rodent chow containing choline chloride. Urolithiasis was traced to racemic, rather than levo-, bitartaric acid in some purified diets shipped in 2001 and 2002. It is unknown when the impurity first appeared in the diet, so estimates of exposure duration are upper limits. Chronic methylmercury exposure increased vulnerability. Some families (dam + offspring) had multiple cases of urolithiasis, but probability models constructed to evaluate familial clustering revealed no evidence for a genetic predisposition to urolithiasis apart from gender. Removing racemic tartaric acid did not decrease mortality once rats had been on the diet for 20 to 30 weeks, but it helped when exposure duration was shorter.     

The effects of elk velvet antler consumption on the rat: development, behavior, toxicity and the activity of liver gamma-glutamyltranspeptidase

The effect of exposure to, followed by consumption of, a diet containing 10% powdered elk velvet antler (EVA) from the 18th day of gestation to the 88th day after birth was examined in male and female Fischer 344 rats. There were no teratogenic effects of EVA exposure in utero or differences in birth outcomes between pups born to regular chow fed and EVA chow fed dams. Growth curves of the EVA fed rats were identical to those of regular chow fed rats, as were developmental milestones of pinna development and eye-opening. Acoustical startle and righting reflexes, developmental and behavioral indices, were identical. Blood glucose levels were comparable in EVA chow fed and regular chow fed rats, indicating that EVA is without effect on glucose balance. There were no signs of toxicity in the EVA chow fed compared to regular chow fed rats as judged from plasma enzyme markers of liver damage: plasma levels of alanine aminotransferase were 50% lower in EVA chow fed rats compared to regular chow fed rats; and plasma levels of gamma-glutamyltranspeptidase (gammaGT) were the same. The activity of gammaGT displayed a decrease in the livers of EVA chow fed rats, more so in the male (22%) than in the female (14%), suggestive of an androgenic effect. A possible hepatobeneficial effect of the EVA induced decrease in liver gammaGT is discussed. In summary, dietary10% EVA chow is without long term effect on growth, development and behavior is non-toxic and may be hepatobeneficial.     

Sex-differentiated enzyme levels and oestrogen uptake in adult rats treated neonatally with tamoxifen or CI-628

Serum cholinesterase, hepatic histidase and monoamine oxidase activity levels are higher in adult female rats than in adult male rats. Exposure of neonatal rats to antioestrogen (tamoxifen or CI-628) resulted in increased serum cholinesterase in adult females only and no effect on hepatic histidase and monoamine oxidase in both sexes. Neonatal tamoxifen or CI-628 treatment resulted in reduced body weights in adult male rats and reduced uterine wet weights in adult female rats. Circulating oestrogen levels measured in adult female rats treated neonatally with tamoxifen were not significantly different from controls. Specific oestrogen uptake in the brain of adult male and female rats was found to be higher in the pituitary than in the preoptic-anterior hypothalamic area and the median eminence-basal hypothalamus than in the cerebral cortex. There was higher uptake of [3H]oestradiol-17 beta in male pituitaries than in female pituitaries. No other sex-difference was observed. Neonatal tamoxifen treatment did not alter the capacity of these brain tissues to take up oestrogen. It is suggested that neonatal antioestrogen exposure has altered the endocrine expression of serum cholinesterase in adult female rats by interfering with normal imprinting mechanisms.     

Gonadal hormones during puberty organize environment-related social interaction in the male rat

This study examined the role of gonadal androgens during puberty on the development of environment-related social interaction (SI) in male rats. SI in an unfamiliar environment versus SI in a familiar environment was evaluated in young adult rats as a function of sex and gonadal status. Intact male rats at 60 days of age exhibited a differential response to the two environments, whereas SI in intact female rats at 60 days was equivalent in the two environments. Furthermore, male rats castrated as juveniles and tested for SI at 60 days displayed a pattern of environment-related SI similar to SI in intact adult female rats. This effect of juvenile castration on SI in male rats was prevented by chronic exposure to testosterone propionate (TP) over Days 30 through 60. SI in male rats castrated in adulthood, on the other hand, was not altered either 2 or 4 weeks postcastration. The results from this study indicate that pubertal secretions of gonadal androgen(s) are necessary for the development of environment-related SI in male rats. In contrast, secretions of gonadal androgens in adulthood do not appear to be critical for the continued expression of environment-related SI, as suggested by the observation that environment-related SI in male rats remains unchanged by castration in adulthood.     

Prenatal administration of arginine vasopressin impairs memory retrieval in adult rats

Eight pregnant female rats were chronically treated via an osmotic pump with arginine vasopressin or placebo during days 13 to 19 gestation. All offspring were tested as adults in either a discrimination task or a 25 day retention of a passive avoidance response. The results revealed that rats whose mother had been treated with vasopressin did not differ from controls on the acquisition or reversal of a brightness discrimination; however, they did require more trials to reach criterion during the ten day memory test of discrimination reversal. Further, treatment resulted in impaired memory retrieval in male rats on the 25 day memory test, while female rats were not affected. Treatment did not influence body weight. The results indicated that vasopressin administered during the prenatal period of development may have had a teratogenic effect on memory retrieval.     

Administration of gonadal steroids to neonatal rats affects beta-endorphin levels in the adult

Administration of gonadal steroids to neonatal rats has a profound effect on the function of the neuroendocrine system in the adult animal. Considering that gonadal steroids modulate hypothalamic and pituitary levels of beta-endorphin (BE) in adult male and female rats, the effects of neonatal gonadal steroid treatment on BE levels in the adult animal were investigated. Neonatal male rats were administered testosterone and neonatal female rats were treated with estrogen. Matched control littermates received vehicle. All animals were sacrificed at 90 days of age. Neonatal gonadal steroid treatment did not affect the level of immunoreactive beta-endorphin (IR-BE) in the anterior pituitary (AP) of male rats but did result in a significant increase in IR-BE in the AP of female rats. Neonatal administration of gonadal steroids produced a significant decrease in IR-BE in the neurointermediate lobe of the pituitary (NIL) of both male and female rats, with the magnitude of the decrease being greater in the NIL of the female rats. IR-BE levels in the hypothalamus of male or female rats were not altered by the treatments. Column chromatography indicated that the increase in IR-BE in the AP represented a proportional increase in BE and beta-lipotropin, while the reduction in IR-BE in the NIL of the treated rats represented a reduction in BE. These findings suggest that gonadal steroids may influence the development of the neurotransmitter systems which regulate BE levels in the adult pituitary, the development of the biosynthetic mechanisms of the adult pituitary, or both.     

Prenatal testosterone exposure leads to hypertension that is gonadal hormone-dependent in adult rat male and female offspring

Prenatal testosterone exposure impacts postnatal reproductive and endocrine function, leading to alterations in sex steroid levels. Because gonadal steroids are key regulators of cardiovascular function, it is possible that alteration in sex steroid hormones may contribute to development of hypertension in prenatally testosterone-exposed adults. The objectives of this study were to evaluate whether prenatal testosterone exposure leads to development of hypertension in adult males and females and to assess the influence of gonadal hormones on arterial pressure in these animals. Offspring of pregnant rats treated with testosterone propionate or its vehicle (controls) were examined. Subsets of male and female offspring were gonadectomized at 7 wk of age, and some offspring from age 7 to 24 wk received hormone replacement, while others did not. Testosterone exposure during prenatal life significantly increased arterial pressure in both male and female adult offspring; however, the effect was greater in males. Prenatal androgen-exposed males and females had more circulating testosterone during adult life, with no change in estradiol levels. Gonadectomy prevented hyperandrogenism and also reversed hypertension in these rats. Testosterone replacement in orchiectomized males restored hypertension, while estradiol replacement in ovariectomized females was without effect. Steroidal changes were associated with defective expression of gonadal steroidogenic genes, with Star, Sf1, and Hsd17b1 upregulation in testes. In ovaries, Star and Cyp11a1 genes were upregulated, while Cyp19 was downregulated. This study showed that prenatal testosterone exposure led to development of gonad-dependent hypertension during adult life. Defective steroidogenesis may contribute in part to the observed steroidal changes.     

Estrogen treatment during development alters adult partner preference and reproductive behavior in female laboratory rats

There is broad acceptance for the idea that during development estradiol ‘organizes’ many aspects of reproductive behavior including partner preferences in the laboratory rat. With respect to partner preference, this idea is drawn from studies where estrogen action was in someway blocked, either through aromatase or estrogen receptor inhibition, during development in male rats. The lack of estrogens neonatally results in a decrease in the male rat's preference for females. In this study, the effect of early postnatal estradiol treatment on the partner preferences of female rats was examined as a further test of the hypothesis that male-typical partner preference is dependent upon early exposure to estrogens. Our principal finding was that increased postnatal estradiol exposure during development affected partner preference in the expected direction, and this effect was seen under several adult hormonal and behavioral testing conditions. Female rats that received exogenous estradiol during development spent more time with an estrous female and less time with a sexually active male than did cholesterol treated females. The estradiol treatment also disrupted normal female sexual behavior, receptivity, and proceptivity.     

Spatial and temporal variations in nesting success and the causes of nest losses of the freshwater three-spined stickleback,Gasterosteus aculeatus

Synopsis Two experients were conducted to determine the effect of male color phenotype present during development on the mate choice of adult female guppies. Females were raised with either a colorful male, non-colorful male, or no male, and then measured for choice of a colorful or non-colorful male in a two-stimulus visual choice test. In the first experiment, adult females were measured for choice between the same male phenotypes used during the developmental exposure. Females raised with colorful males had significantly higher choice scores for colorful males than did females raised with non-colorful males or with no male. In the second experiment, an effect of developmental experience was observed when adult females were tested for choice with a general range of colorful and non-colorful males. However, this effect of experience during development was not detected when females were tested for choice between the same male phenotypes used during the developmental exposure. The predation regime of the source population, either high or low, showed no consistent effect on average female choice or on whether developmental experience changed female mate choice. Overall, these experiments show that experience with male phenotypes can affect the mate choice of adult guppies, but this effect was not observed under all developmental treatments or test conditions. Such an effect could significantly change the dynamics of the evolution of female preference due to sexual selection in the guppy.     

Perinatal exposure to low doses of 2,3,7,8-tetrachlorodibenzo-p-dioxin alters sex-dependent expression of hepatic CYP2C11

The cytochrome P450 (CYP) isoform CYP2C11 is specifically expressed in the liver of adult male rats, and 5alpha-reductase is specifically expressed in the liver of the adult female rats. The sexually dimorphic expressions of these hepatic enzymes are regulated by the sex-dependent profiles of the circulating growth hormone (GH). However, it is not well known whether hormonal imprinting or activation factors in the neonatal brain influence the sexually dimorphic expression patterns of hepatic enzymes. We therefore examined the effect of perinatal exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) on sex-dependent expressions of hepatic enzymes. Pregnant rats were treated with TCDD at a dose of 0, 200, or 800 ng/kg on gestation day 15, exposing the pups to the chemical. Although the expression of CYP2C11 protein in the livers of male pups on postnatal day (PND) 49 was significantly higher than that of the controls, but the 5alpha-reductase activities in the livers of female pups were not altered by exposure to TCDD. Focusing on perinatal periods, testosterone and estrogen levels significantly increased in the brain of male pups on PND 2. The results suggest that the alteration of testosterone and estrogen levels affect hormonal imprinting in the neonatal brain of male pups, and thus induces a change in the level of male-specific hepatic CYP2C11. We conclude that perinatal exposure to TCDD at low doses may change the sexual differentiation of the neonatal brain in male rats.     

Effects of testosterone and estrogen on hepatic levels of cytochromes P450 2C7 and P450 2C11 in the rat.

The effects of exogenous hormone treatment on the expression of cytochromes P450 2C7 and P450 2C11 were studied in neonatally gonadectomized and sham-operated male and female rats. Hepatic levels of cytochrome P450 2C7 were found to be two- to threefold higher in intact adult female versus male rats. Neonatal gonadectomy resulted in a reversal of the relative cytochrome P450 2C7 levels in male and female animals at maturity. Expression of this isozyme was restored in ovariectomized females by estradiol treatment. Furthermore, neonatal and/or pubertal administration of estradiol to intact male rats induced cytochrome P450 2C7 to adult female levels. On the other hand, administration of testosterone at all times examined had no effect in intact female rats, but decreased cytochrome P450 2C7 to normal levels in neonatally castrated males treated during adulthood. Neonatal testosterone treatment also increased hepatic cytochrome P450 2C7 content in both ovariectomized females and intact males. These results indicate that estrogen is required for full expression of cytochrome P450 2C7 while the effect of testosterone is ambiguous. In comparison, neonatal gonadectomy of male rats abolished the adult expression of cytochrome P450 2C11. Normal levels were restored only by treatment with testosterone during adulthood. Neonatal testosterone treatment did not induce cytochrome P450 2C11 levels in gonadectomized rats of either sex. In contrast, neonatal estrogen treatment suppressed cytochrome P450 2C11 expression in intact adult male rats to the same extent as neonatal castration. These results indicate that androgen exposure during the adult, and not the neonatal, phase is essential for full expression of cytochrome P450 2C11.     

Ovarian hormones act early in development to feminize adult open-field behavior in the rat

Three experiments were done to investigate the feminizing effect of prepubertal ovarian hormones on the development of adult sex differences in open-field behavior in the rat. Gonadectomy at either 1 or 8 days of age, but not at 23 days or later, disrupted the normally high levels of activity found in adult females. Exposure of Day 1 gonadectomized female and male rats to low doses of exogenous estradiol between Days 10 and 20 led to higher levels of adult activity than did oil treatment. Finally it was shown that low doses of estradiol had similar effects on open-field scores whether given between Days 10 and 20 or between Days 30 and 40, whereas exposure of Day 1 gonadectomized females to a high dose of estradiol as late as 10 days of life appeared to suppress adult open-field activity. It was concluded that estrogens given during the period prior to weaning can have a feminizing effect on adult open-field behavior and that the sex difference normally observed in adult rats is dependent in part on the presence of the ovaries during a period after birth.     

Teratogenic effects of environmental chemicals.

Despite the widespread distribution of a great many chemical substances in the environment, very few have been implicated in human teratogenicity, and most of these are drugs used at relatively high biological effect levels. Although several other types of environmental chemicals such as pesticides, solvents, and metals can be shown under laboratory conditions to have some teratogenic potential, there is little evidence that these, at present ambient concentrations and conditions of exposure, represent significant hazards to human intrauterine development. An exception to the latter generalization is methylmercury which, because of peculiarities in distribution, can reach high concentration in the human diet.     

Partial isolation of a pheromone accelerating puberty in female mice.

The sexual development of female mice is accelerated by exposure to an adult male or to male urine. The component of the urine responsible for this effect is androgen-dependent, heat labile, nondialysable, precipitatable with ammonium sulphate, and is not extractable in ether. These results indicate that the pheromone causing accelerated sexual development is associated with a protein component of male urine. Tests of the active fraction after digestion with proteolytic enzymes suggest that the pheromone may be a portion of a protein or a substance bound to a protein.     

Effects of estradiol and testosterone on the activity of pyruvate kinase of the cardiac and skeletal muscles of rats as a function of age and sex

The specific activities of pyruvate kinase of cardiac and skeletal (gastrocnemius) muscles of adult rats of both sexes are lower than those of immature rats. The activity does not change after adulthood in the cardiac muscle, but decreases in the gastrocnemius. The activity of pyruvate kinase of the heart of immature and adult rats of both sexes decreases after castration, but is unaffected in old rats. Castration has no effect on the activity of pyrovate kinase of the gastrocnemius muscle of rats of both sexes at any age. In invo administration of estradiol (50 μg/100 g body weight) increases the activity of pyruvate kinase of the heart of castrated male and female rats of the three ages. For the skeletal muscle, the activity increases in castrated adult female and old male rats only. A higher dose (100 μg) of estradiol has variable effects on pyruvate kinase of the heart of male and female castrated rats of different ages. This dose increase pyruvate kinase significantly in the skeletal muscle of old castrated male and female rats. However, it decreases it in the skeletal muscle of adult castrated male rats. Testosterone (100 μm) increases the activity of pyruvate kinase of the heart of castrated male rats. This increase is lower in old age. It has no effect in the heart of castrated female rats of any age. Testosterone (50 μg) increases pyruvate kinase activity of the skeletal muscle of young ovariectomized rats only. A higher dose (100 μg) causes a significant increase in pyruvate kinase of the skeletal muscle of castrated adult and old male, and young and adult female rats, respectively. These data show that sex steroid hormones induce pyruvate kinase of striated muscles, and that the age- and sex-dependent variations may be due to changes in the levels of receptor proteins.     

Is androgen-dependent aromatase activity sexually differentiated in the rat and dove preoptic area?

Aromatase activity is higher in the male than in the female anterior hypothalamic-preoptic area (POA) in both the avian and the rodent adult brain. This sex difference is abolished after castration of the male and restored by androgen treatment. Gonadectomy has no effect on POA aromatase in the female. The aim of this study was to find out whether sex dimorphism in adult POA aromatase is only due to a sex difference in circulating gonadal hormones or dependent upon sexual differentiation of the brain. Aromatase activity was measured in vitro in microdissected POA samples using a sensitive radiometric assay. We examined the effects of gonadectomy and testosterone treatment on enzyme activity in adult rats and doves of both sexes. We also studied the effects of neonatal gonadectomy and hormone substitution in male and female rats. The results suggest that levels of POA aromatase in the adult depend primarily on gonadal activity, but that mechanisms involved in the regulation of aromatase activity and enzyme induction may be sex-specific and could result from sexual differentiation of the brain in early life. Further work will be required to determine the developmental stage when this occurs and the exact mechanism(s) responsible for increased sensitivity of the adult male POA to the inductive effect of testosterone.     

Modest maternal protein restriction fails to program adult hypertension in female rats

Modest maternal dietary protein restriction in the rat leads to hypertension in adult male offspring. The purpose of this study was to determine whether female rats are resistant to developing the increased blood pressure seen in male rats after maternal protein restriction. Pregnant rats were fed a normal protein (19%, NP) or low-protein (8.5%, LP) diet throughout gestation. Renal renin protein and ANG II levels were reduced by 50-65% in male LP compared with NP pups, but were not suppressed in female LP compared with female NP. Mean arterial pressure in conscious, chronically instrumented adult female offspring (22 wk) was not different in LP (LP: 120 +/- 3 mmHg vs. NP: 121 +/- 2 mmHg), and glomerular filtration rate was also not different in LP vs. NP. The number of glomeruli per kidney was similar in adult LP and NP female offspring (LP: 26,050 +/- 2,071 vs. NP: 26,248 +/- 1,292, NP), and individual glomerular volume was also not different (LP: 0.92 +/- 0.11 10(6) microm(3), LP vs. NP: 1.07 +/- 0.11 10(6) microm(3)); the total volume of all glomeruli per kidney was also not significantly different. Thus female rats are relatively resistant to the programming for adult hypertension by perinatal protein restriction that we have described in males. This resistance may be due to the fact that modest maternal protein restriction does not reduce the number of glomeruli with which females are endowed as it does in males. The intrarenal renin-angiotensin system during development may play a key role in this protective effect of female gender.     

Testosterone modulation of reproductive indices vs. morphine antinociception in male rats

The purpose of this study was to determine whether testosterone (T) concurrently modulates reproductive and nociceptive systems in the adult male. Male Sprague-Dawley rats were orchidectomized, and then 28 days later implanted with capsules containing T or nothing (blanks). After 2, 7, 14 or 28 days' exposure to T-filled or blank capsules, rats were tested for male sexual and nociceptive behaviors in a counter-balanced design. As the duration of T exposure lengthened, the percentage of rats showing male sexual behaviors and the weights of steroid-sensitive organs systematically increased, and latencies to show sexual behaviors decreased. T treatment did not affect basal nociception on either the hotplate or tail withdrawal tests, but significantly increased morphine's antinociceptive potency on the tail withdrawal test -- however, this effect was small, and independent of duration of T exposure. Thus, T treatment that altered male sexual behavior and reproductive physiology in a systematic, duration-dependent manner did not similarly alter basal nociception or morphine antinociception. These findings suggest that in adult male rats, although T may modulate both male sexual behaviors and opioid antinociceptive sensitivity, these T effects do not occur in concert.     

Estradiol increases growth hormone secretion in rats exposed to swimming stress or reserpine treatment

The secretory pattern of growth hormone (GH) in female rats differs from that in males with respect to e.g. the inter-peak baseline levels being higher in females. In the present study the influence of sex steroids on plasma GH levels was investigated in male rats under various conditions. Administration of estradiol, but not testosterone, was found to increase GH release in rats with suppressed levels induced by exposure to swimming stress or by treatment with the monoamine depleting agent reserpine. In line with previous studies, administration of estradiol was found to increase also inter-peak GH levels in adult male rats; i.e. to cause a feminization of the secretory pattern. In stressed and in reserpinized animals as well as in normal male rats, the effect of estradiol is similar to that earlier demonstrated for somatostatin antiserum, and hence it is suggested that estradiol may act antagonistic to the GH inhibiting factor.     

Hypoxia in early pregnancy induces cardiac dysfunction in adult offspring of Rattus norvegicus, a non-hypoxia-adapted species

Environmental stresses such as hypoxia can alter the development of the fetus that are manifested later in life, but the impact of early maternal hypoxia (MH) on cardiac performance, coronary flow and catecholamine responsiveness in adult offspring is less clear. The effects of exposure to chronic hypoxia (FIO(2)=0.12) in early intrauterine development (days E1-10) on cardiac performance of the adult offspring were estimated using the Langendorff-perfused rat heart. Cardiac dysfunction is presented as increased end-diastolic volume, with decreased ventricular stiffness in both male and female adult offspring (P<0.01 for both). While developed pressures were preserved in female MH rats, males demonstrated a decrease in systolic function, estimated as peak developed pressure (P<0.01). Challenge with dobutamine (300nM), an adrenergic positive inotrope, increased cardiac work for control rats (P<0.01 for male and female rats) but not in MH-male rats. Coronary flow was reduced (P<0.01) and SERCA2 protein expression increased (2-fold, P<0.05) in female offspring, while eNOS protein levels were increased (2.5-fold, P<0.05) in females. This suggests gender-specific differences in compensatory responses to early MH, with female rats increasing calcium turnover to improve contractility and increasing coronary flow through increased expression of eNOS protein, partially restoring coronary perfusion while male rats show little compensation.