Testosterone In Male Mice Research Articles

Loss of testosterone induces postprandial insulin resistance and increases the expression of the hepatic antioxidant flavin-containing monooxygenases in mice exposed to intermittent hypoxia.

We tested the hypothesis that low testosterone alters the effects of intermittent hypoxia (IH) on glucose homeostasis, hepatic oxidative stress, and transcriptomic profile in male mice. We used sham-operated or orchiectomized (ORX) mice exposed to normoxia (Nx) or IH for 2 weeks. We performed fasting insulin and glucose tolerance tests and assessed fasting and postprandial insulin resistance with the HOMA-IR. The activity of hepatic prooxidant (NADPH oxidase-NOX), antioxidant enzymes (superoxide dismutase, catalase, and glutathione peroxidase-SOD, Cat, GPx), lipid peroxidation (MDA concentration), and the total concentration of glutathione (GSH) were measured under postprandial conditions. mRNA sequencing and pathway enrichment analyses were used to identify hepatic genes underlying the interactions between IH and testosterone. In Sham mice, IH improves fasting insulin sensitivity and glucose tolerance, while there are no effects of IH in ORX mice. In ORX mice, IH induces postprandial hyperinsulinemia, insulin resistance, and a prooxidant profile of enzyme activity (low SOD activity) without altering hepatic MDA and GSH content. ORX and IH altered the expression of genes involved in oxidoreductase activities, cytochromes-dependent pathways, and glutathione metabolism. Among the genes upregulated in ORX-IH mice, the flavin-containing monooxygenases (FMO) are particularly relevant since these are potent hepatic antioxidants that could help prevent overt oxidative stress in ORX-IH mice. Low levels of testosterone in male mice exposed to IH induce post-prandial hyperinsulinemia and insulin resistance and determine the mechanisms by which the liver handles IH-induced oxidative stress.

Recovery of Prenatal Baicalein Exposure Perturbed Reproduction by Postnatal Exposure of Testosterone in Male Mice.

Baicalein (BC), a flavonoid, which lacks the qualities of reproductive health and shows adverse effects, is tested in this study. Inseminated mice were injected with 30, 60, and 90 mg BC/Kg body weight on gestation days 11, 13, 15, and 17. The F1 BC-exposed males of each dosage were divided into six groups. First three groups (n = 6 from each BC dosage) were used for assessment of reproductive performance, the others (n = 4 from each BC dosage) were administered with testosterone 4.16 mg/kg body weight on postnatal days 21, 31, and 41. The reproductive health of adult F1 males at the age of 55 and 60 was tested. Prenatal BC exposure showed reduced fertility after cohabitation with control females. The BC exposure significantly reduced the body weight, tissue indices, and sperm parameters (motility, count, viability, and daily sperm count) and altered the sperm membrane in a hypoosmotic swelling test. A downward trend was observed in testicular steroidogenic marker enzymes (3β- and 17β-steroid dehydrogenases) and serum testosterone, whereas increase in serum titers of FSH and LH along with altered the testicular histology. Conversely, testosterone (4.16 mg/kg body weight) partially recovered reduced male reproductive health by BC. BC impaired male reproductive health due to low levels of testosterone is reverted by external testosterone is evidenced in this study.

Sexual-Dimorphism in Exercise-Induced Beiging and Altered Mitochondrial Function in Inguinal White Adipose Tissue (iWAT) from the Mouse

Regular physical exercise has numerous benefits on metabolic health, likely involving adaptations to many tissues, including adipose tissue. There are conflicting reports on the effects of exercise training on adaptations to iWAT and we hypothesized that these discrepancies may stem in part from sex-specific differences. Male and female 10 week old C57BL6/J mice were housed in cages with (trained) or without (sedentary) running wheels for 11 days (n=6-9/sex/experiment). Males performed less voluntary exercise vs. females (56±7 vs. 78±5 km; p<0.05). In males, training decreased iWAT fat pad weight (19.6%) and adipocyte size (19%) (both p<0.05), whereas training did not have these effects on iWAT in females, most likely due to increased food intake. Training did not alter perigonadal WAT weight or adipocyte size in either sex. In iWAT, training in males increased mRNA of the beiging genes Ucp1 (304%; p<0.01); Pgc1α (228%; p<0.05); Cidea (206%; p<0.05); and Dio2 (197%; p<0.01), as well as Ucp1 protein (124%; p<0.01), but none of these markers were increased in females. Exercise training also increased mitochondrial parameters in iWAT only from males, including basal respiration (170%; p<0.01), glycolytic capacity (227%; p<0.001) and the mitochondrial fission genes Opa1 (235%; p<0.05), Mfn1 (231%; p<0.001), and Mfn2 (229%; p<0.01). Since exercise may increase testosterone in male mice, we tested the effects of testosterone on iWAT beiging and mitochondria. iWAT of male and female mice were treated with testosterone (10μM) for 24 hours. Interestingly, testosterone increased Ucp1 protein (175%; p<0.05) and mRNA (386%; p<0.05) in iWAT from male, but not in females. We conclude that voluntary wheel running in mice results in beiging and mitochondrial adaptations to iWAT exclusively in males. Sex-specific differences in WAT function will be important to consider in all research investigating adipose tissue beiging and mitochondrial function. Disclosure P. Nigro: None. R. Middelbeek: None. C.R. Alves: None. B.G. Albertson: None. L.A. Rowland: None. A.B. Wagner: None. N.B. Prince: None. M.F. Hirshman: None. L.J. Goodyear: None.

Pyrethroid Insecticide Cypermethrin Accelerates Pubertal Onset in Male Mice via Disrupting Hypothalamic-Pituitary-Gonadal Axis.

Pyrethroids, a class of insecticides that are widely used worldwide, have been identified as endocrine-disrupting chemicals (EDCs). Our recent epidemiological study reported on an association of increased pyrethroids exposure with elevated gonadotropins levels and earlier pubertal development in Chinese boys. In this study, we further investigated the effects of cypermethrin (CP), one of the most ubiquitous pyrethroid insecticides, on hypothalamic-pituitary-gonadal (HPG) axis and pubertal onset in male animal models. Early postnatal exposure to CP at environmentally relevant doses (0.5, 5, and 50 μg/kg CP) significantly accelerated the age of puberty onset in male mice. Administration of CP induced a dose-dependent increase in serum levels of luteinizing hormone (LH), follicle-stimulating hormone (FSH) and testosterone in male mice. CP did not affect gonadotropin-releasing hormone (GnRH) gene expression in the hypothalamus, but CP at higher concentrations stimulated GnRH pulse frequency. CP could induce the secretion of LH and FSH, as well as the expression of gonadotropin subunit genes [chorionic gonadotropin α (CGα), LHβ, and FSHβ] in pituitary gonadotropes. CP stimulated testosterone production and the expression of steroidogenesis-related genes [steroidogenic acute regulatory (StAR) and Cytochrome p 450, family 11, subfamily A, polypeptide 1 (CYP11A1)] in testicular Leydig cells. The interference with hypothalamic sodium channels as well as calcium channels in pituitary gonadotropes and testicular Leydig cells was responsible for CP-induced HPG axis maturation. Our findings established in animal models provide further evidence for the biological plausibility of pyrethroid exposure as a potentially environmental contributor to earlier puberty in males.

Endocrine-Disrupting Activity of Hydraulic Fracturing Chemicals and Adverse Health Outcomes After Prenatal Exposure in Male Mice.

Oil and natural gas operations have been shown to contaminate surface and ground water with endocrine-disrupting chemicals. In the current study, we fill several gaps in our understanding of the potential environmental impacts related to this process. We measured the endocrine-disrupting activities of 24 chemicals used and/or produced by oil and gas operations for five nuclear receptors using a reporter gene assay in human endometrial cancer cells. We also quantified the concentration of 16 of these chemicals in oil and gas wastewater samples. Finally, we assessed reproductive and developmental outcomes in male C57BL/6J mice after the prenatal exposure to a mixture of these chemicals. We found that 23 commonly used oil and natural gas operation chemicals can activate or inhibit the estrogen, androgen, glucocorticoid, progesterone, and/or thyroid receptors, and mixtures of these chemicals can behave synergistically, additively, or antagonistically in vitro. Prenatal exposure to a mixture of 23 oil and gas operation chemicals at 3, 30, and 300 μg/kg · d caused decreased sperm counts and increased testes, body, heart, and thymus weights and increased serum testosterone in male mice, suggesting multiple organ system impacts. Our results suggest possible adverse developmental and reproductive health outcomes in humans and animals exposed to potential environmentally relevant levels of oil and gas operation chemicals.

Sexual dimorphism in BDNF signaling after neonatal hypoxia–ischemia and treatment with necrostatin-1

Brain injury due to neonatal hypoxia–ischemia (HI) is more homogenously severe in male than in female mice. Because, necrostatin-1 (nec-1) prevents injury progression only in male mice, we hypothesized that changes in brain-derived neurotrophic factor (BDNF) signaling after HI and nec-1 are also sex-specific providing differential conditions to promote recovery of those more severely injured. The increased aromatization of testosterone in male mice during early development and the link between 17-β-estradiol (E2) levels and BDNF transcription substantiate this hypothesis. Hence, we aimed to investigate if sexual differences in BDNF signaling existed in forebrain and diencephalon after HI and HI/nec-1 and their correlation with estrogen receptors (ER). C57B6 mice (p7) received nec-1 (0.1μl [8μM]) or vehicle (veh) intracerebroventricularly after HI. At 24h after HI, BDNF levels increased in both sexes in forebrain without evidence of tropomyosin-receptor-kinase B (TrkB) activation. At 96h after HI, BDNF levels in forebrain decreased below those seen in control mice of both sexes. Additionally, only in female mice, truncated TrkB (Tc.TrkB) and p75 neurotrophic receptor (p75ntr) levels increased in forebrain and diencephalon. In both, forebrain and diencephalon, nec-1 treatment increased BDNF levels and TrkB activation in male mice while, nec-1 prevented Tc.TrkB and p75ntr increases in female mice. While E2 levels were unchanged by HI or HI/nec-1 in either sex or treatment, ERα:ERβ ratios were increased in diencephalon of nec-1-treated male mice and directly correlated with BDNF levels. Neonatal HI produces sex-specific signaling changes in the BDNF system, that are differentially modulated by nec-1. The regional differences in BDNF levels may be a consequence of injury severity after HI, but sexual differences in response to nec-1 after HI may represent a differential thalamo-cortical preservation or alternatively off-target regional effect of nec-1. The biological significance of ERα predominance and its correlation with BDNF levels is still unclear.

Estrogen supplementation in female mice yields higher sodium (Na) retention than that of testosterone in male mice

Our purpose was to determine the effects of estrogen and testosterone supplementation on Na retention, blood pressure (MAP), and mRNA levels of renal Na transporters in mice. Gonadectomized female and male mice (CD1, 30–35g, 4–6 weeks old) received a pellet of 1.5 mg 17β‐estradiol (E2) and 5 mg testosterone, respectively. In metabolic cages mice consumed 1% salt diet for 10 days, 4% salt for the next 10 days, and 1% salt for the final 10 days. Na intake (Nai) and renal Na excretion (Nae) were measured daily. MAP was measured in the final 4–5 days of each period via tail‐cuff. Real‐time PCR was conducted on kidney tissue processed on the final day of each period. Nae/Nai % (mean ± se): (n=4) 1% Salt 4% Salt 1% Salt NF 57.3 ± 3.9 59.9 ± 2.5 54.0 ± 3.3 NM 47.9 ± 3.8 55.8 ± 2.9 48.4 ± 2.9 OE 28.3 ± 1.3* 32.4 ± 1.7* 37.8 ± 2.6*# CT 53.5 ± 3.1 56.7 ± 3.5 47.6 ± 3.3 NF & NM: normal female and male mice, OE: ovariectomized + E2, CT: castrated + T, ‐ different from all other values (p<0.001); ‐ different from first 1% OE period (p<0.05) MAP (mmHg) of OE mice were 95.7 ± 4.1, 79.5 ± 4.6, 93.0 ± 4.9 (1%, 4%, 1%, respectively) and not different from those of NF. PCR data showed E2‐induced upregulation of NCC, NKCC2, and ENaC mRNA.ConclusionE2 supplementation in female mice produced higher Na retention than that of T in male mice without enhancing MAP. Study supported by OCAST (OK Center for the Advancement of Science and Technology) # HR 09‐123, and OK Epscor INBRE #P20RR016478.

Sex differences of urinary and kidney globotriaosylceramide and lyso-globotriaosylceramide in Fabry mice

The aim of our study was to measure globotriaosylceramide (Gb(3)) and lyso-Gb(3) levels by tandem mass spectrometry in the urine and kidney in Fabry (gla knockout) mice and wild-type controls. We found that urine Gb(3) of male and female Fabry mice was higher than wild-type mice of the same sex but also significantly higher in male mice compared with females of the same genotype. In kidney tissue, sex and genotype-dependent differences in Gb(3) levels paralleled those in the urine. Isoforms C16, C22:1, and C24OHA were particularly higher in males compared with females in both wild-type and Fabry mice. Similarly, kidney lyso-Gb(3) concentrations were significantly higher in 12-month-old male Fabry mice than in their homozygous female counterparts. However, lyso-Gb(3) was undetectable in wild-type mice of both sexes. α-Galactosidase A activity and mRNA levels in kidney were significantly lower in male wild-type mice compared with female mice. This study shows the sex differences in kidney and urine Gb(3) and kidney lyso-Gb(3) levels in both wild-type and Fabry mice, and it suggests that these male-female differences should be taken into consideration when using murine models for Fabry disease.

Androgen Receptor-Dependent and Independent Atheroprotection by Testosterone in Male Mice

The atheroprotective effect of testosterone is thought to require aromatization of testosterone to estradiol, but no study has adequately addressed the role of the androgen receptor (AR), the major pathway for the physiological effects of testosterone. We used AR knockout (ARKO) mice on apolipoprotein E-deficient background to study the role of the AR in testosterone atheroprotection in male mice. Because ARKO mice are testosterone deficient, we sham operated or orchiectomized (Orx) the mice before puberty, and Orx mice were supplemented with placebo or a physiological testosterone dose. From 8 to 16 wk of age, the mice consumed a high-fat diet. In the aortic root, ARKO mice showed increased atherosclerotic lesion area (+80%, P < 0.05). Compared with placebo, testosterone reduced lesion area both in Orx wild-type (WT) mice (by 50%, P < 0.001) and ARKO mice (by 24%, P < 0.05). However, lesion area was larger in testosterone-supplemented ARKO compared with testosterone-supplemented WT mice (+57%, P < 0.05). In WT mice, testosterone reduced the presence of a necrotic core in the plaque (80% among placebo-treated vs. 12% among testosterone-treated mice; P < 0.05), whereas there was no significant effect in ARKO mice (P = 0.20). In conclusion, ARKO mice on apolipoprotein E-deficient background display accelerated atherosclerosis. Testosterone treatment reduced atherosclerosis in both WT and ARKO mice. However, the effect on lesion area and complexity was more pronounced in WT than in ARKO mice, and lesion area was larger in ARKO mice even after testosterone supplementation. These results are consistent with an AR-dependent as well as an AR-independent component of testosterone atheroprotection in male mice.

A microsphere-based duplex competitive immunoassay for the simultaneous measurements of aldosterone and testosterone in small sample volumes: Validation in human and mouse plasma

Background The small blood volumes available in rodent studies often limit adequate quantification of all hormones of interest. We report here the development of two new assays combining an extraction step with multiplex immunoassay (MIA) technology for the simultaneous determination of aldosterone and testosterone in 50 μl sample volume. Methods Following solvent extraction, aldosterone and testosterone competitive immunoassays are performed incorporating biotinylated tracers and antibody-coated beads each having a unique fluorescence. Quantification is via addition of streptavidin–R–phycoerythrin (SA–PE). The assays were validated and compared to established methods. Baseline hormone levels in mice from four different strains, and changes after ACTH and HCG stimulation in CD-1 mice are shown. Results The assays are sensitive (aldosterone 15 pg/ml, testosterone 12 pg/ml), reproducible (intra-/inter-assay imprecision aldosterone 5.1–15.6%/9.9–15.8% and testosterone 9.7–10.9%/7.7–11.4%) and correlate significantly to established assays ( r = 0.94–0.95). Baseline aldosterone levels varied between strains, but not between the genders. Testosterone was significantly higher in male of all strains except in C57BL/6× NMRI mice. After ACTH injection, aldosterone (median, interquartile range) rose from 354 (261–396) pg/ml to 2008 (875–2467) in male and from 260 (210–576) to 1120 (734–1528) in female CD-1 mice. HCG injection in the same strain increased testosterone in male mice only (3.5 (0.4–8.3) ng/ml to 31.8 (30.4–33.9) ng/ml, P < 0.01). Conclusions We describe a MIA for the simultaneous measurement of aldosterone and testosterone in small volumes after extraction. In addition to presenting a new tool for steroid research in rodent models, our data show strain-dependent differences in steroid hormone metabolism in rodents.

Early handling increases susceptibility to experimental autoimmune encephalomyelitis (EAE) in C57BL/6 male mice

Brief maternal separations of neonatal animals can exert long-lasting effects on the reactivity of the neuroendocrine system. The aim of the present study was to investigate whether manipulations of the mother–infant interaction could affect susceptibility to immune-mediated diseases, such experimental autoimmune encephalomyelitis (EAE), and whether this effect would be mediated by changes in leptin which has been shown to regulate disease susceptibility and severity at adulthood. Given the different gender susceptibility to EAE previously described, we tested also whether early experiences could differentially affect the two genders. To this purpose, female and male C56BL/6 mice were subjected to handling (15 min daily) postnatally, from day 2 until day 14. All subjects were weaned at 21 days. At 7 weeks of age mice were immunized with MOG 35-55 to actively induce EAE. We thus determined the effect of neonatal handling on plasma concentrations of testosterone in male mice and leptin in both genders at different times post EAE induction. Our results show that early experiences influence susceptibility to EAE in a gender-specific manner, early manipulations resulting in an enhancement of sex-related differences in susceptibility. These effects were associated with changes in the testosterone profile of male subjects. Changes in leptin levels during the preclinical stage of EAE may predict a more severe disease course.

The Effects of Vitex agnus castus Extract and its Interaction with Dopaminergic System on LH and Testosterone in Male Mice

The purpose of this study was to evaluate the probable effects of Vitex agnus castus (Vac.) on the male reproductive physiology. It is a well known fact that LH secretion from the anterior pituitary of mammals is controlled by many neurotransmiters such as dopamine. In this experiment, we have studied the effect of Vac. extract on the LH and testosterone hormones and its interaction with the dopaminergic system on male mice. In order to evaluate these effects, we used the hydroalcoholic Vac. extract (for extraction we used percolation technique) injection with the following doses: 65, 165, 265, 365 and 465 mg kg-', bromocriptine as a dopamine receptor agonist (5, 10, 20 mg kg(-1)) and haloperidol as a dopamine receptor antagonist (1, 1.5, 2, 2.5, 3 mg kg(-1)). To study the interaction between Vac. extract and dopaminergic system, we injected the optimum doses of Vac. with bromocriptine or haloperidol at the same time. Intraperitoneal injections were applied in all experiments, once a day for 30 days. The control group remained intact and the sham group received vehicle. After the last injection, we collected the animal blood serums for hormonal assays. LH and testosterone were measured by Radio Immuno Assay (RIA). LH and testosterone, showed significant decrease in bromocriptine group and haloperidol increased these hormones. Vac. extract decreased significantly the LH and testosterone levels. The coadministration of Vac. extract and bromocriptine decreased LH and testosterone. Coadministration of Vac. extract and haloperidol decreased LH and testosterone levels. These results suggest: dopamine regulates the gonadotroph-leydig cells axis. It appears that Vac. exertes effects through dopaminergic system and other pathways. The findings of this study show we can use Vac. extract for pathological cases of increasing LH and testosterone.

High level of circulating testosterone abolishes decline in scent attractiveness in antigen-treated male mice

We hypothesized that a decrease in the attractiveness of odours from infected male mice, Mus musculus could be caused by either parasite-induced changes in host metabolism (parasite-dependent pathway) or activation of the immune defence system (immune-dependent pathway). Activation of the immune defence system by nonreplicated antigens (sheep red blood cells, SRBC) is sufficient for a decrease in both scent attractiveness and the concentration of plasma testosterone in male mice. Since the scent attractiveness of male mice depends on androgen levels, we studied the olfactory effect of SRBC in sham-operated, gonadectomized and testosterone-treated male mice of the outbred strain ICR. SRBC administration resulted in a decline in both sexual odour attractiveness and concentration of urinary proteins in sham-operated control males. The effect of SRBC on concentration of urinary proteins was abolished by stabilizing the testosterone level in gonadectomized and androgen-treated males. At the same time, only the high dose of testosterone was sufficient to maintain the scent attractiveness in SRBC-treated males at the pretreatment level.

Effects of repeated aggressive encounters on approach to a female and plasma testosterone in male mice

Effects of repeated experience of aggression accompanied by social victories or social defeat in 10 daily agonistic confrontations on testosterone levels in and the behavioral response of CBA/Lac male mice exposed to a receptive female from behind a perforated transparent partition have been examined. Testosterone levels were not changed significantly in the mice that had consistently been victorious over 10 days (winners) or in the mice that had consistently been defeated over 10 days (losers). Losers and controls (mice that had been caged individually for 5 days) responded with increased levels of behavioral activity near the partition and elevated testosterone. Winners showed a significantly poorer behavioral and hormonal response. It is concluded that the repeated display of aggression by male mice led to a reduction in both their behavioral and neuroendocrine responses to an estrous female.

Role of some types of serotonin receptors in murine hypophyseal-testicular complex activation induced by the presence of a female

Placement of a sexually receptive female mouse behind a partition that prevents physical contacts, but permits it to see and smell caused an increase in the blood levels of testosterone in male mice. The selective 5-HTIA-serotonin receptor agonist 08-OH- DPAT (0.1 mg/kg) and the mixed 5-HTIA/IB agonist eltoprazine, 3.0 and 10.0 mg/kg, blocked the activating effect of female exposure on the male pituitary-testicular system. The 5-HT/-receptor agonist p-MPPI (0.2 mg/kg) prevented the inhibitory effects of 8-OH-DPATand eltoprazine. The 5-HT/B-receptor agonist CGS- 12066A (1.0 and 2.0 mg/kg) exerted no effect while the mixed 5-HTIB/2C-receptor agonist TFMPP (5.2 mg/kg) inhibited a female-induced increase in the levels of male blood testosterone. The 5-HT/-receptor agonist keranserin (1.0 and 2.0 mg/kg) prevented a female-induced increase in the levels of testosterone. The 5-HT3-receptor agonist ondansetron (0.05 and 0.1 mg/kg) elevated the baseline level of plasma testosterone, but blocked receptive female-induced activation of the male hypothalamic-pituitary-testicular system (HPTS). It is concluded that 5-HTIA-receptors are involved in the control of male sexual activation. At the same time different types and even subtypes of the same type of 5-HT-receptors produce varying inhibitory and activating effects on the receptive female-induced activation of HPTS. Blocking of the female-induced activation of HPTS seems to be realized by involving 5-HTu- and 5-HT2C-receptors and its activation occurs with the participation of 5-HT^- and 5- HT3-receptors.

Pfaffia paniculata-induced changes in plasma estradiol-17beta, progesterone and testosterone levels in mice.

The present study undertook chemical analysis of components of Pfaffia paniculata roots. In addition, an animal experiment was conducted in which mice had ad libitum access to water enriched with powdered P. paniculata root for 30 days. Changes in plasma concentrations of estradiol-17beta and progesterone in female mice and of testosterone in male mice were ascertained. The results revealed that P. paniculata roots contain two types of phytosteroids, beta-sitosterol and stigmasterol, in addition to other compounds such as pfaffic acid, allantoin, saponins, beta-sitosteryl-beta-D-glucoside, and stigmasteryl-beta-D-glucoside. Regarding changes in plasma concentrations of hormones, levels of the sex hormones estradiol-17beta, progesterone and testosterone were clearly higher for mice that drank P. paniculata root-enriched water than for mice that drank plain water. Powdered P. paniculata root is easily dissolved in feed or water, and as no adverse reactions were seen in mice within 30 days of oral intake, consumption of P. paniculata for long periods of time appears safe.

Sex Hormones in Experimental Autoimmune Encephalomyelitis: Implications for Multiple Sclerosis

For decades, it has been known that females are more susceptible than males to multiple sclerosis (MS). It has also long been appreciated that during late pregnancy there is a decrease in MS disease activity. Interestingly, these two observations have also been made in an extensively used animal model for MS, experimental autoimmune encephalomyelitis (EAE) in SJL mice. Female mice are more susceptible to disease than male mice, and there is an improvement in disease during late pregnancy. In this review, the role of sex hormones in each of these two observations is characterized in this EAE model using castration and exogenous hormone treatment strategies. The gender difference in EAE susceptibility is due primarily to a protective effect of testosterone in male mice. The decrease in disease severity during late pregnancy appears to be due at least in part to high levels of estriol, which characterize this time period.

Testosterone levels in plasma and testes of neonatal mice

Newborn female and male C57BL6 mice were decapitated at birth or at different times during the first 24 h after birth and testosterone was determined by radioimmunoassay in plasma and testes. In newborn females, plasma testosterone is low and does not significantly change over the first 24 h after birth. In contrast, in newborn males, plasma testosterone more than doubles during the first 2 h after birth and then falls rapidly to remain relatively low for the remainder of the 24 h period after birth. The increase in plasma testosterone is of almost certain testicular origin since it follows a decrease in testicular testosterone content. It seems likely that the increase in plasma testosterone in male mice which reaches its peak at 2 h after birth is involved in an essential way in the development of well-documented sex differences in gonadotropin secretion and behavior.

Effects of castration and testosterone in male mice on Schistosoma mansoni

Effects of castration and testosterone in male mice on Schistosoma mansoni Get access Edward Berg, Ph.D. Edward Berg, Ph.D. Department of Biology, New York State College for Teachers USA Search for other works by this author on: Oxford Academic PubMed Google Scholar Transactions of The Royal Society of Tropical Medicine and Hygiene, Volume 51, Issue 4, July 1957, Pages 353–358, https://doi.org/10.1016/0035-9203(57)90127-X Published: 01 July 1957