Effect of corticosteroids on arachidonate induced mortality in male and female mice

Sodium arachidonate (50 mg/kg) given intravenously to male and female mice induces pulmonary emboli followed by respiratory distress and cyanosis. Female mice are significantly more resistant to this treatment than male mice. Cortisone pretreatment for four days to intact mice (10 mg/kg/day/4 days) had a significant protective effect in both males and females against arachidonate toxicity, eliminating the sex difference previously observed. Adrenalectomy four days before arachidonate infusion increased the sensitivity to SA and resulted in 100% mortality in both sexes. Pretreatment of adrenalized animals with cortisone significantly reduced to some degree the mortality rate in both sexes. Castration of male and female mice three weeks before adrenalectomy did not affect the mortality rate seen following adrenalectomy alone. In conclusion, exogenous cortical steroids augment the resistance of even intact mice and are absolutely necessary for survival in adrenalectomized animals. The observed sex differences in untreated intact animals is not seen after treatment with cortisone or adrenalectomy.     

Differential Responses to Same and Opposite Sex Odors by Adult House Mice Are Associated with Anogenital Distance

Intrauterine position (IUP) of female and male fetuses in litter-bearing mammals can affect their physiology, morphology and behavior. The relationship between anogenital distance (AGD) and IUP was used as a bioassay for the degree of exposure of female and male fetuses to hormones in utero . Based on laboratory work in several rodent species, the following predictions were made for house mice ( Mus musculus domesticus ): (1) female mice should prefer odors from males with larger AGDs because such males are more aggressive, could protect more resources, and are better parents than males with smaller AGDs; (2) male mice should prefer odors from females with smaller AGDs because these females produce more offspring and are better parents than females with larger AGDs. We also tested the prediction that within sexes, mice should avoid odors from mice with larger AGDs because such mice are more aggressive. Responses to odors in traps were used to test these predictions for house mice living in outdoor enclosures using odor-baited traps. Both predictions were confirmed. Furthermore, mice of both sexes tended to avoid odor cues from individuals of the same sex that had larger AGDs, probably to decrease chances of an aggressive encounter that could result in injury.     

Hypothyroidism in reproductively inhibited prairie deer mice (Peromyscus maniculatus bairdi) from laboratory populations

Several thyroid function parameters were compared between reproductively inhibited prairie deer mice of both sexes taken from laboratory populations and corresponding reproductively capable controls. The results of these experiments indicated the following: 1) prairie deer mice females had a statistically significant daily variation in mean serum thyroxine concentration and males displayed a similar trend; 2) total serum thyroxine and triiodothyronine were significantly lower in both male and female reproductively inhibited population animals compared with reproductively capable controls; 3) several morphometric characteristics of the thyroid of male and female population prairie deer mice were significantly different from that of control males and females, suggesting functional hypothyroidism in both sexes; 4) thyroid histology of male population deer mice was different from that of female population animals. In males, the data suggested that thyroid-stimulating hormone (TSH) stimulation was deficient due to some undetermined secondary hypothyroidism. In females, reduced serum thyroxine and triiodothyronine concentrations were observed due to primary hypothyroidism of unknown origin. The interrelationship between thyroid and adrenal function is discussed here and it is concluded that each of the systems may contribute to the observed reproductive inhibition. In particular, it was noted that the mechanism of response between population males and females may be quite different. No conclusive data are available to suggest whether one or the other system is the primary controller of the reproductive inhibition.     

Effect of multiple mating on the reproductive performance of the rice leaffolder moth,Cnaphalocrocis medinalis (Lepidoptera: Crambidae)

To clarify whether multiple mating of females and males affects the reproductive performance of the rice leaffolder moth, Cnaphalocrocis medinalis (Guenée), we examined the effect of the number of matings (once, twice, or three times) for females (female treatment) and males (male treatment) on the incidence of moth mating, number of eggs laid, egg hatchability, and adult longevity. We also compared the effect of multiple mating imposed on males or females separately with the effect of that imposed on both sexes simultaneously (both sexes treatment). The incidence of mating of females and males that mated three times (3-mated females and males) was significantly lower than for females and males that mated twice or once (2-mated or 1-mated females and males). The incidence of mating of 1-mated moths (both sexes) was significantly higher than for 2-mated or 3-mated moths (both sexes). Two-mated or 3-mated females laid significantly more eggs with significantly higher hatchability than 1-mated females. Females that mated with 1-mated males (second male mating) or 2-mated males (third male mating) laid significantly fewer eggs than those that mated with virgin males (first male mating). Females laid significantly more eggs after the second and third matings for moths of both sexes than after the first mating for moths of both sexes. The mechanisms of improvement and decline of female reproductive performance when multiple mating was imposed on males or females are also discussed in relation to the reproductive biology of C. medinalis.     

Asymmetrical costs of sexual conflict in the seaweed fly, Coelopa frigida

Abstract.  1. Sexual conflict can play an important role in the evolution of animal life-history characteristics, including lifespan. Seaweed flies show an increase in mortality rates when exposed to brown algae. The seaweed stimulates females to oviposit and males to mount females. Females typically respond to male mounts by performing a violent rejection response.
2. Here the contribution of sexual conflict to the increase in mortality seen in the presence of seaweed was determined. The survival of single and mixed sex pairs of flies was followed in the presence and absence of seaweed.
3. The two sexes showed differential survival rates, with females living longer in the absence of seaweed. The presence of seaweed reduced survival in both sexes. In the presence of seaweed, female survival was lower when paired with a male. Over 40% of the reduction in survival in females in the presence of seaweed appears to be attributable to sexual conflict.
4. The presence of a female did not significantly affect male survival. Thus the mortality cost of being in the presence of the opposite sex and seaweed appears highly asymmetric.
5. In the presence of seaweed, female survival was lower when females were paired with small males. Small males exhibit higher levels of harassment of females, thus it is argued that pre-copulatory sexual conflict is the probable cause of the increased mortality cost to females of being in the presence of both males and seaweed.     

QT interval prolongation and decreased heart rates after intravenous bolus oxytocin injection in male and female conscious rabbits

The aim of this study was to evaluate changes in heart rate (HR), QT and RR intervals and corrected QT (QTc) values in conscious male and female New Zealand rabbits which intravenously received oxytocin (OXT) at different dosages. Animals were divided into 6 equal groups: group I (n = 6 male, received 0.75 U OXT per animal); group II (n = 6 male, received 1.5 U OXT per animal); group III (n = 6 male, received 3 U OXT per animal); group IV (n = 6 female, received 0.75 U OXT per animal); group V (n = 6 female, received 1.5 U OXT per animal); group VI (n = 6 female, received 3 U OXT per animal). ECG recording were taken from all animals before injection and then at 2, 4, 6, 8, 10, 15 and 20 min of OXT administration. QT and RR intervals obtained at 2 min of OXT administration were significantly prolonged in all groups (p < 0.05) with one exception that is the 1.5 U OXT injected female group where only QT interval did not change. The prolongation of QT and RR intervals persisted for 20 min in 1.5 U OXT injected male group while only QT interval prolongation was obvious for 20 min in 3 U OXT injected female group as for the other groups the prolonged interval were observed for 8-10 min and then returned to baseline values. Generally, a significant prolongation of QTc was noticed in both male and female rabbits at the 2 and 4 min in all groups and bradycardia was noticed at 2 min of OXT administration in all groups. Heart beats returned to normal values in all groups after 8 min of OXT administration. The change of HR, RR, QT and QTc was gender- but not dose-dependent (p < 0.001). The male rabbits were more sensitive to OXT effect then female rabbits. In conclusion, OXT used in therapeutic dosages decreased heart rate and prolonged QT and QTc intervals. Although cardiovascular effect of OXT are of short duration, its use in patient with risk factors for malignant arrhythmias requires more attention.     

Genetically heterogeneous mice exhibit a female survival advantage that is age‐ and site‐specific: Results from a large multi‐site study

The female survival advantage is a robust characteristic of human longevity. However, underlying mechanisms are not understood, and rodent models exhibiting a female advantage are lacking. Here, we report that the genetically heterogeneous (UM‐HET3) mice used by the National Institute on Aging Interventions Testing Program (ITP) are such a model. Analysis of age‐specific survival of 3,690 control ITP mice revealed a female survival advantage paralleling that of humans. As in humans, the female advantage in mice was greatest in early adulthood, peaking around 350 days of age and diminishing progressively thereafter. This persistent finding was observed at three geographically distinct sites and in six separate cohorts over a 10‐year period. Because males weigh more than females and bodyweight is often inversely related to lifespan, we examined sex differences in the relationship between bodyweight and survival. Although present in both sexes, the inverse relationship between bodyweight and longevity was much stronger in males, indicating that male mortality is more influenced by bodyweight than is female mortality. In addition, male survival varied more across site and cohort than female survival, suggesting greater resistance of females to environmental modulators of survival. Notably, at 24 months the relationship between bodyweight and longevity shifted from negative to positive in both sexes, similar to the human condition in advanced age. These results indicate that the UM‐HET3 mouse models the human female survival advantage and provide evidence for greater resilience of females to modulators of survival.     

Male life history and the unusual adult sex ratios of redfronted lemur, Eulemur fulvus rufus, groups

In group-living species, theoretical considerations indicate the existence of a fundamental conflict of interest between the sexes over the adult sex ratio within groups. Females may derive certain benefits from living with many males. Males, in contrast, should generally try to monopolize access to a group of females. Which sex ultimately controls adult group sex ratio is poorly known. We examined this conflict between the sexes in redfronted lemurs, Malagasy primates characterized by an unusual lack of female-biased adult sex ratios. Using various demographic and behavioural data from several groups collected over 6 years, we examined (1) the proximate determinants of this unusual sex ratio, (2) the temporal distribution of female fertile phases within groups as a determinant of male monopolization potential, (3) sources of between-group variation in the adult sex ratio, and (4) possible social benefits of the relatively high number of males for both sexes. Birth and mortality rates were not sex biased and males migrated considerably more frequently than females, providing no proximate explanation for the unusual sex ratio. However, certain life history traits (fast maturation, short interbirth intervals) may ultimately play a role because they act to facilitate joint group transfers of male coalitions. Despite a relatively small female group size and an associated high monopolization potential, female oestrous synchrony may prevent the formation of single-male groups. Reduced male group size seems to be the main predictor of take-over rate, and, thus, infanticide risk, suggesting that both sexes may benefit from the high number of coresident males, thereby considerably defusing the conflict of interest between the sexes.     

Biotransformation in Egyptian spiny mouse Acomys cahirinus

The activities of several representative biotransformation enzymes were determined in male and female spiny mouse tissues. Cytochrome P450 monooxygenase activity toward benzo(a)pyrene was significantly greater in female spiny mouse intestine than in males. Activity toward benzphetamine in both sexes was high in the liver, with little activity in the kidney and intestine. Sulfotransferase activity was high in kidney and intestine of female spiny mice but undetectable in the same tissues in males. Hepatic glutathione s-transferase activity towards 1-chloro-2,4-dinitrobenzene in females was significantly higher than in males. UDP-Glucuronosyltransferase activity toward 1-naphthol in both sexes in the kidney was significantly higher than hepatic and intestinal activity. Intestinal N-acetyltransferase activity towards 2-aminofluorene and β-naphthylamine was significantly greater in females than males. No consistent relation appeared to exist between biotransformation activities in spiny mouse and those in other related rodent species.     

Response to hyperoxia is associated with similar ho-1 gene expression level in lungs of aging CBA mice of both sexes

Beside classical antioxidative enzymes, the response to hyperoxia might be mediated via regulation of other systems, such as heme oxygenase (HO). Ho-1 gene expression is found to be upregulated by hyperoxia in all groups of mice, while HO-1 protein isoform was increased only in 4 months old male mice. In steady-state conditions ho-1 and ho-2 gene expression remained unchanged irrespective of sex or age, which was not the case with protein level of both isoforms. This study suggests that in lungs of CBA mice the response to oxidative stress may be mediated through the interaction of other systems such as heme oxygenase, primarily via upregulation of ho-1 gene expression in both sexes. Contrary to our previous study in liver of hyperoxia treated mice, current results might imply that at conventional oxygen conditions lungs of female mice with the emphasis on aging females, are better prepared for oxidative stress conditions through the increase of HO-activity.     

Encoding choosiness: female attraction requires prior physical contact with individual male scents in mice

Scents, detected through both the main and vomeronasal olfactory systems, play a crucial role in regulating reproductive behaviour in many mammals. In laboratory mice, female preference for airborne urinary scents from males (detected through the main olfactory system) is learnt through association with scents detected through the vomeronasal system during contact with the scent source. This may reflect a more complex assessment of individual males than that implied by laboratory mouse studies in which individual variation has largely been eliminated. To test this, we assessed female preference between male and female urine using wild house mice with natural individual genetic variation in urinary identity signals. We confirm that females exhibit a general preference for male over female urine when able to contact urine scents. However, they are only attracted to airborne urinary volatiles from individual males whose urine they have previously contacted. Even females with a natural exposure to many individuals of both sexes fail to develop generalized attraction to airborne male scents. This implies that information gained through contact with a specific male's scent is essential to stimulate attraction, providing a new perspective on the cues and olfactory pathways involved in sex recognition and mate assessment in rodents.     

Schistosoma mansoni: mortality, pathophysiology, and susceptibility differences in male and female mice.

In parallel studies of Schistosoma mansoni infections in male and female CBA/J mice, major sex-related differences are seen in the development of infection and disease. Upon equal subcutaneous exposures to 45 cercariae female mice present a more severe clinical course with consequent higher mortality than male mice. By 12 weeks of infection, more than 80% of female mice die, while less than 20% of infected males succumb to infection. This greater index of mortality is apparently due to the higher susceptibility of female mice to the development of adult worms. Exposed to 45 cercariae, virtually all females develop patent infections, but 8-34% of male mice do not do so. Also, the recovery rate of adult worms per cercariae from female mice is much higher than that from males, indicating that schistosomula are more successful in developing into adult worms in female mice. Additional studies indicate that this dichotomy of schistosomiasis in the sexes is not restricted to mice of the CBA/J strain, but also occurs in C57BL/6 and outbred CF1 strain mice.     

Sexual differences in hormonal control of release calls in bullfrogs

Release calls in anuran amphibians are given when animals are inappropriately clasped by others. Since other call types, such as mate calls, are sexually dimorphic in frogs and toads, sonogram analysis was used to determine whether release call characteristics might also be sexually dimorphic in bullfrogs (Rana catesbeiana). Only intercall intervals differed significantly between males and females. Call duration, dominant frequency characteristics, and the display of secondary or tertiary harmonic frequencies were similar in both sexes. In the spring, but not the fall, calling rates were significantly lower in female bullfrogs, compared to males. Females also had significantly lower plasma androgen concentrations and higher plasma estrogen in the spring, compared to males. In both sexes, plasma androgen and estrogen were significantly higher in the spring, compared to the fall. The neuropeptide arginine vasotocin significantly decreased release call rates in females in the spring while it significantly increased rates in males. Vasotocin had no significant effect in the fall. Prostaglandin E2 significantly inhibited release calling in both males and females. On the other hand, prolactin significantly inhibited calling in female bullfrogs, but had no affect in males. Thus, although acoustic characteristics of release calls were similar in male and female bullfrogs, hormonal control of call rates was sexually dimorphic and seasonally variable.     

Conspecific odor detection by the male broad-headed skink, Eumeces laticeps: effects of sex and site of odor source and of male reproductive condition

Olfactory stimuli are sufficient for detection and discrimination of sex of conspecific lizards by the male broad-headed skink, Eumeces laticeps, a member of a large group of lizards with pronounced chemosensory abilities, the Autarchoglossa. The capacity of male broad-headed skinks to detect conspecific odors was assessed by measuring tongue extrusion rates in response to odor stimuli presented on moist cotton applicators. Tongue-flick rates of postreproductive males were significantly higher for cloacal odors of postreproductive conspecifics of both sexes than to distilled water and higher to female than male odors over the initial 20- and 60-sec intervals. In a second experiment using testosterone-treated males and estrogen-injected females, testosterone-treated males emitted significantly more tongue flicks to female cloacal odors than to the other stimuli, and two males bit applicators bearing male odors. Testosterone did not affect reaction to male cloacal odors, but markedly increased tongue-flick rates in response to cloacal odors of estrogen-treated females. Postreproductive males also responded to female, but not male, skin odors at a significantly higher rate than to water. Possible sources and presumed adaptive significance of conspecific odors are discussed.     

Schistosoma mansoni: male-biased sex ratios in snails and mice

Adult sex ratios of Schistosoma mansoni, in mice, were shown to be biased toward males (3:1) despite the finding that sex ratios of miracidia were 50:50. The adult male bias was caused by greater male infectivity of miracidia for snails and cercariae for mice. A significantly higher percentage of male miracidia developed to cercarial production in unimiracidial infections (57 male, 34 female), and a significantly higher percentage of male cercariae developed to adulthood in mice (143 male, 79 female worms resulted from 900 male and 900 female cercariae). No significant differences were found between male and female parasites for longevity of miracidia (both sexes, 10 hr) and cercariae (males 21.3 +/- 5.75 hr, females 25.0 +/- 7.02 hr), prepatent periods in snail hosts (male 34 +/- 2.92 days, females 33 +/- 2.36 days), longevity of snail infections (males 96.6 +/- 25.15 days, females 115.2 +/- 82.43 days), and the numbers of cercariae produced per snail lifetime (males 30,751.44 +/- 18,064.33, females 34,083.00 +/- 33,732.82). Present results provide a better understanding of the life cycle of S. mansoni, are of theoretical significance for theories of biased sex ratios (which at present cannot account for the male-biased ratio of S. mansoni), and also suggest that schistosomiasis transmission models assuming a 50:50 sex ratio at all stages of the life cycle should be reassessed.     

Elevated 17β-estradiol protects females from influenza A virus pathogenesis by suppressing inflammatory responses

Studies of the 1918 H1N1 influenza pandemic, the H5N1 avian influenza outbreak, and the 2009 H1N1 pandemic illustrate that sex and pregnancy contribute to severe outcome from infection, suggesting a role for sex steroids. To test the hypothesis that the sexes respond differently to influenza, the pathogenesis of influenza A virus infection was investigated in adult male and female C57BL/6 mice. Influenza infection reduced reproductive function in females and resulted in greater body mass loss, hypothermia, and mortality in females than males. Whereas lung virus titers were similar between the sexes, females had higher induction of proinflammatory cytokines and chemokines, including TNF-α, IFN-γ, IL-6, and CCL2, in their lungs than males. Removal of the gonads in both sexes eliminated the sex difference in influenza pathogenesis. Manipulation of testosterone or dihydrotestosterone concentrations in males did not significantly impact virus pathogenesis. Conversely, females administered high doses of estradiol had a ≥10-fold lower induction of TNF-α and CCL2 in the lungs and increased rates of survival as compared with females that had either low or no estradiol. The protective effects of estradiol on proinflammatory cytokines and chemokines, morbidity, and mortality were primarily mediated by signaling through estrogen receptor α (ERα). In summary, females suffer a worse outcome from influenza A virus infection than males, which can be reversed by administration of high doses of estradiol to females and reflects differences in the induction of proinflammatory responses and not in virus load.     

Function and genetics of long versus short copulations in the cactophilic fruit fly,drosophila mojavensis (diptera: drosophilidae)

Variation in copulation duration of Drosophila mojavensisstrains was influenced by both sexes. Males maintained predominant control, as copulation duration of pairs from different strains was more similar to that of the strain from which the male was derived, but female origin also contributed significantly to the duration of copulation. Variation among strains was controlled by genes acting additively in both sexes. The size of both males and females also affected copulation duration. Small males copulated longer on average than large males, while males paired with large females copulated longer than those paired with small females. The importance of copulation duration to fitness was tested by correlation analyses with male size, female size, female remating latency, and number of eggs laid prior to female remating. Longer copulations stimulated earlier oviposition, possibly by increasing accessory gland secretions that are passed by males during copulation.     

Enhanced urinary odor discrimination in female aromatase knockout (ArKO) mice

We asked whether odor discrimination abilities are sexually dimorphic in mice and, if so, whether the perinatal actions of estradiol contribute to these sex differences. The ability to discriminate different types of urinary odors was compared in male and female wild-type (WT) subjects and in mice with a homozygous-null mutation of the estrogen synthetic enzyme, aromatase (aromatase knockout; ArKO). Olfactory discrimination was assessed in WT and ArKO male and female mice after they were gonadectomized in adulthood and subsequently treated with estradiol benzoate. A liquid olfactometer was used to assess food-motivated olfactory discrimination capacity. All animals eventually learned to distinguish between urinary odors collected from gonadally intact males and estrous females; however, WT males as well as ArKO mice of both sexes learned this discrimination significantly more rapidly than WT females. Similar group differences were obtained when mice discriminated between urinary odors collected from gonadally intact vs. castrated males or between two non-social odorants, amyl and butyl acetate. When subjects had to discriminate volatile urinary odors from ovariectomized female mice treated with estradiol sequenced with progesterone versus estradiol alone, ArKO females quickly acquired the task whereas WT males and females as well as ArKO males failed to do so. These results demonstrated a strong sex dimorphism in olfactory discrimination ability, with WT males performing better than females. Furthermore, female ArKO mice showed an enhanced ability to discriminate very similar urinary odorants, perhaps due to an increased sensitivity of the main olfactory nervous system to adult estradiol treatment as a result of perinatal estrogen deprivation.     

Sex-dependent antioxidant enzyme activities and lipid peroxidation in ageing mouse brain

We investigated whether oxidant status and antioxidant enzyme activities during ageing of mouse brain are regulated in sex-dependent manner. In the homogenate from the brain of 1, 4, 10 and 18 months old male and female CBA mice, lipid peroxidation (LPO), total superoxide dismutase (tSOD), catalase (CAT) and glutathione peroxidase (Gpx) were determined. LPO was age- and sex-related, favoring males over females throughout the lifespan with the peak in both sexes at 10 months of age. Throughout ageing, no difference in tSOD activity between male and female brains was observed, except in immature 1 month old mice. Gender-related difference in Gpx activity was observed, with higher level in females comparing to males, reaching statistical significance in senescent (18 months old) animals. CAT activity was drastically changed with ageing in both the male and female brain. We found different age associated trends in CAT activity in males and females: decreased with age in males and increased with age in females. Taken together, the present findings indicate that brains of female mice have lower oxidant and higher antioxidant capacity mostly related to CAT and to a lesser extent to Gpx activity.     

支气管肺发育不良小鼠模型的建立

目的建立支气管肺发育不良小鼠模型。方法将30只4日龄雌性昆明小鼠随机分为2组,每组15只,氧气组置于氧箱（FiO20.6）,空气组置于空气中（FiO20.21）,分别于暴露7 d、14 d、21 d时每组随机选取5只,称重后处死,观察肺组织形态学、放射状肺泡计数（radical alveolar counts,RAC）及肺胶原含量变化。结果氧气组各时间点体重较空气组均明显降低（P〈0.001）;实验21 d时氧气组肺组织HE染色下见正常肺泡结构破坏,肺泡隔增厚,肺泡融合;氧气组RAC较空气组显著降低（P〈0.001）;肺胶原天狼猩红特殊染色见Ⅰ型、Ⅲ型胶原增生,较空气组显著增加（P〈0.001）。结论中等浓度氧（FiO20.6）暴露21 d可致小鼠肺发生类似人类支气管肺发育不良改变。