Role In Dimorphism Research Articles

The effect of annexin 1 on inflammatory stress in the microcirculation

The bodies' response mechanisms against inflammation can be influenced by gender and sex hormone status, and can become deregulated and detrimental, leading to tissue damage. This study has investigated the anti‐inflammatory protein annexin 1 and its role in the sexual dimorphism of inflammatory disease.Male and proestrous female WT (C57BL/6) and male AnxA1 null (ANXA1‐/‐) mice were challenged with lipopolysaccharide (LPS). The mesentery was exteriorised and leukocyte‐endothelial cell interactions were recorded using intravital microscopy.In both male and female WT mice, LPS caused a significant increase in leukocyte adherence and emigration in venules vs. saline group, but with no difference between sexes. LPS administration had a modest effect in AnxA1‐/‐ mice, with only venular leukocyte rolling being decreased, which may be indicative of the initial phase of inflammation. Further studies in which the time course of the response to LPS is examined are now required. However, our findings fit with previous data concerning the survival rate of AnxA1‐/‐ mice, which is significantly decreased at 24hr, but not 2hr (1).To conclude, these data suggest that there is no sexual dimorphism in the inflammatory response following 2hr LPS challenge. Furthermore, this inflammatory response is not observed in AnxA1‐/‐ mice.1. Damazo AS et al., Am J Pathol. 2005;166:1607‐17.

Differential sexual dimorphism: size and shape in the cranium and pelvis of grey foxes (Urocyon)

Patterns of sexual size dimorphism (SSD) and cranial dimorphism are well documented. However, limited examinations exist of the contrasts in the patterns and nature of dimorphism across body regions (e.g. cranium, pelvis), particularly when these regions have different sex-specific functions (e.g. display in mating, locomotion, and reproduction). Using landmark-based morphometric techniques, we investigated size and shape dimorphism variation in the crania and pelves of two closely-related fox species within the genus Urocyon. Although we found no significant size and shape dimorphism in the crania of either species, we did find significant dimorphism in the pelvis: its size was dimorphic in Urocyon littoralis (but not in Urocyon cinereoargenteus) and its shape was dimorphic in both species (though more pronounced in U. littoralis). The observation of greater dimorphism in the pelvis than in the cranium suggests that factors such as offspring size and locomotor mode play a greater role in sexual dimorphism than simple ‘whole body’ allometric affects associated with dimorphism in body size. © 2009 The Linnean Society of London, Biological Journal of the Linnean Society, 2009, 96, 339‐353. ADDITIONAL KEYWORDS: allometry ‐ Canidae ‐ Carnivora ‐ function ‐ geometric morphometrics ‐ shape dimorphism index.

The influence of digit ratio on the gender difference in learning style preferences

Fetal testosterone has been shown to affect the areas in the brain that are critical for learning and memory. The present study was designed to investigate if prenatal testosterone exposure is a candidate for having a causal role in sexual dimorphism observed in learning style preferences. A total of 183 students (mean age: 20.65 ± 2.42) from a population of 247 (74%) were enrolled in the study. Learning style preference was determined via the Turkish version of the learning style inventory, and the digit lengths of both hands were measured using digital calipers. Unimodal learning was more frequent among males (30.6% vs. 17.1%; p < 0.01). There was no marked difference in learning styles with respect to age. Digit ratio (2D/4D) of both hands was determined to be significantly lower in males, when compared to females ( p < 0.001). Lower 2D/4D ratios were determined to be associated with unimodal learning significantly in both genders. In conclusion, represented by digit ratio (2D/4D) as a proxy marker, prenatal testosterone exposure may have a causal role in the sexual dimorphism observed in learning style preferences.

Role of Larval Sexual Dimorphism, Biased Sex Ratios, and Habitat on the Energetics of a Tropical Chironomid

Larval sex dimorphism, fecundity, and sex ratios have been rarely studied in lotic insects, but can have ecological, energetic, and evolutionary importance. I evaluated the effect of microhabitat quality on larval and pupal sex dimorphism and sex ratios using a Hawaiian chironomid (Telmatogeton torrenticola Terry) and examined differences between sex-corrected and noncorrected biomass and secondary production estimates. Larvae and pupae were collected from two microhabitat types defined by microscale flow hydraulics to test for habitat effects on sex dimorphism, sex ratios, fecundity, standing stock biomass, secondary production, and Production/Biomass (P/B) ratios. Female larvae were more than twice as large as males, and this was more pronounced in pupae. Males were twice as abundant as females, and there was no effect of habitat on fourth-instar density. There was, however, a significant habitat effect on morphology, larval body size, standing stock biomass, secondary production, and P/B ratios. Biomass was not statistically different between sexes, but sex-corrected biomass was significantly lower than noncorrected biomass in both habitats but is likely not biologically significant. Sex-corrected secondary production estimates were 69-85% of noncorrected estimates depending on habitat, and sex correction did have a significant effect on P/B ratios in microhabitats of lower quality. This study is one of the first to address sex dimorphism and sex ratios in estimates of standing stock biomass and secondary production, providing initial evidence that microhabitat quality is important to understanding chironomid population biology and the potential role of sex-related demographics in estimates of productivity.

Role of Larval Sexual Dimorphism, Biased Sex Ratios, and Habitat on the Energetics of a Tropical Chironomid

Role of Larval Sexual Dimorphism, Biased Sex Ratios, and Habitat on the Energetics of a Tropical Chironomid

Sex differences in play behavior in juvenile tufted capuchin monkeys (Cebus apella)

According to the motor training hypothesis, play behavior in juvenile primates improves motor skills that are required in later adult life. Sex differences in juvenile play behavior can therefore be expected when adult animals assume distinct sexually dimorphic roles. Tufted capuchin monkeys show sexually dimorphic levels of physical antagonism in both inter- and intra-group encounters. Accordingly, it can be predicted that juvenile capuchins also show sex differences in social play behavior. To test this hypothesis, the play behavior of nine juvenile and two infant capuchins was examined. As predicted, juvenile males showed significantly higher levels of social play (wrestle, chase) than juvenile females, but no differences were found in nonsocial play (arboreal, object). Levels of infant play behavior were comparable to that of juveniles. These results lend support to the motor training hypothesis and highlight the need for more detailed investigations of individual differences in play behavior.

Choline metabolism is sexual dimorphic in the mouse

Premenopausal women are relatively resistant to choline deficiency compared with postmenopausal women and men. Moreover, studies in animals and human hepatocytes suggest that phosphatidylethanolamine N‐methyltransferase (PEMT) is regulated by estrogen. In this study we investigated whether choline metabolism is sexual dimorphic using a choline dehydrogenase (CHDH) knockout mouse model. After weaning, wild‐type (WT) and knockout (KO) mice were fed AIN‐76A diet for 4 weeks, and livers were collected. Hepatic choline and metabolites concentrations were measured using LC/MS. As expected, CHDH KO animals had significantly lower betaine and higher choline and phosphocholine concentrations than did WT animals, p&lt;0.001. WT females had lower hepatic choline and phosphocholine concentrations, but higher glycerophosphocholine concentrations than WT males. When we knocked out CHDH, the gender differences in hepatic choline and phosphocholine concentrations disappeared, suggesting that CHDH activity plays a role in sexual dimorphism in choline metabolism. We also found that males did not differ in hepatic triacylglycerol regardless of genotype, but female KO mice had 2‐fold more liver fat than did males, p&lt;0.05. We are currently studying whether the expression of CHDH is estrogen responsive.Teng and Johnson contributed equally to this work.

A transgenic mouse with vascular endothelial over-expression of the non-muscle myosin light chain kinase-2 isoform is susceptible to inflammatory lung injury: role of sexual dimorphism and age

We have generated genetically engineered mice that are uniquely susceptible to lipopolysaccharide (LPS)-induced and mechanical ventilation-induced lung injury in a sex-specific and age-specific manner. These mice express a nonmuscle isoform of the myosin light chain kinase gene (nmMLCK2) targeted to the endothelium. Homozygous mice have significantly reduced fecundity and litter survival until weaning, and they are initially growth delayed but eventually exceed the size of wild-type littermates. Mice at all ages show increased protein transport across the lung barrier; however, the phenotype is most discernible in 8-12-week-old male mice. When subjected to a clinically relevant LPS-induced lung injury model, 8-12-week-old young females and 30-36-week-old males seem to be the most significantly injured group. In contrast, 30-36-week-old males remain the most significantly injured group when mechanically ventilated at high tidal volumes, which is a clinically relevant model of mechanical stress lung injury. These data reveal that nmMLCK2 overexpression in the endothelium exacerbates lung injury in vivo in a sexually dimorphic and age-dependent manner.

Claw allometry in green crabs, Carcinus maenas: heterochely, handedness, and sex

Claw loss and reversal of handedness during regeneration are common phenomena in heterochelous decapod crustaceans, which typically have one large ‘crusher’ claw on the right side and a smaller ‘cutter’ claw on the left. Little is known about the relative importance of claw growth vs. body growth during claw regeneration. Here the relationship between claw size and body size of green crabs, Carcinus maenas, was examined to test for differences in claw allometry as a function of handedness and sex, as there are differences in how males and females use their claws. A total of 730 crabs (range = 15.7–83.6 mm CW) were collected from Maine to New Jersey, USA from May to October 1997, 2000, and 2004–2005. Claw growth, particularly crushers, was accelerated in left-handed crabs and in males compared to right-handed crabs and females respectively. These differing growth strategies highlight the role of sexual dimorphism in claw usage and the importance of achieving heterochely after claw injury. These results imply that handedness should be an important factor to consider in future studies of crab morphology, behavior, and morphometrics.

Transcriptional profile ofras1andras2and the potential role of farnesylation in the dimorphism of the human pathogenParacoccidioides brasiliensis

Paracoccidioides brasiliensis is a thermo-dimorphic fungus that causes a human systemic mycosis with high incidence in Latin America. Owing to their participation in the control of pathogen morphogenesis, differentiation and virulence, it was decided to characterize ras genes in P. brasiliensis. ras1 and ras2 were identified to be coding for two different proteins with high identity. The ras transcriptional pattern was investigated by reverse transcription PCR (RT-PCR) during mycelium-to-yeast (M-->Y) transition, heat shock at 42 degrees C and after internalization of yeast cells by murine macrophages. Both genes were downregulated inside macrophages and ras1, at 42 degrees C. In contrast, ras genes did not show any transcriptional variation during the M-->Y transition. The fact that Ras proteins are attached to the membrane via farnesylation prompted the use of a farnesyltransferase inhibitor to investigate the importance of this process for vegetative growth and dimorphic transition. Farnesylation blockage interfered with the vegetative growth of yeast cells and stimulated germinative tube production even at 37 degrees C. During Y-->M transition, the inhibitor increased filamentation in a dose-dependent manner, indicating that impaired farnesylation favours the mycelium form of P. brasiliensis. The results suggest that ras genes might have a role in dimorphism, heat shock response and in host-pathogen interaction.

Gender-Dependent Role of Endogenous Somatostatin in Regulating Growth Hormone-Axis Function in Mice

It has been previously reported that male and female somatostatin (SST) knockout mice (Sst-/-) release more GH, compared with Sst+/+ mice, due to enhanced GH-secretory vesicle release. Endogenous SST may also regulate GH secretion by directly inhibiting GHRH-stimulated GH gene expression and/or by modulating hypothalamic GHRH input. To begin to explore these possibilities and to learn more about the gender-dependent role of SST in modulating GH-axis function, hypothalamic, pituitary, and liver components of the GH-axis were compared in male and female Sst+/+ and Sst-/- mice. Pituitary mRNA levels for GH and receptors for GHRH and ghrelin were increased in female Sst-/- mice, compared with Sst+/+ controls, and these changes were reflected by an increase in circulating GH and IGF-I. Elevated levels of IGF-I in female Sst-/- mice were associated with elevated hepatic mRNA levels for IGF-I, as well as for GH and prolactin receptors. Consistent with the role of GH/IGF-I in negative feedback regulation of hypothalamic function, GHRH mRNA levels were reduced in female Sst-/- mice, whereas cortistatin (CST) mRNA levels were unaltered. In contrast to the widespread impact of SST loss on GH-axis function in females, only circulating GH, hypothalamic CST, and hepatic prolactin receptor expression were up-regulated in Sst-/- male mice, compared with Sst+/+ controls. These results confirm and extend the sexually dimorphic role of SST on GH-axis regulation, and suggest that CST, a neuropeptide that acts through SST receptors to inhibit GH secretion, may serve a compensatory role in maintaining GH-axis function in Sst-/- male mice.

Topical Review: Fetal Testosterone and Sex Differences in Typical Social Development and in Autism

Experiments in animals leave no doubt that androgens, including testosterone, produced by the testes in fetal and/or neonatal life act on the brain to induce sex differences in neural structure and function. In human beings, there is evidence supporting a female superiority in the ability to read nonverbal signals, specific language-related skills, and theory of mind. Even more striking than the sex differences seen in the typical population is the elevated occurrence of social and communicative difficulties in human males. One such condition, autism, occurs four times more frequently in boys than in girls. Recently, a novel theory known as the "extreme male brain" has been proposed. It suggests that the behaviors seen in autism are an exaggeration of typical sex differences and that exposure to high levels of prenatal testosterone might be a risk factor. In this article, we argue that prenatal and neonatal testosterone exposures are strong candidates for having a causal role in sexual dimorphism in human behavior, including social development, and as risk factors for conditions characterized by social impairments, particularly autism spectrum conditions.

Aboveground biomass allocation patterns within Mediterranean sub-shrubs: A quantitative analysis of seasonal dimorphism

The monthly patterns of aboveground biomass allocation were studied in the branches of six Mediterranean sub-shrubs with different leaf phenology. Four of them were seasonally dimorphic species, and the remaining two were a winter deciduous and a cushion plant with photosynthetic stems. By the analysis of these species we aimed to identify different aboveground biomass allocation patterns within seasonally dimorphic species and to understand the role of seasonal dimorphism as a strategy to avoid the main stresses of mediterranean climate: summer drought and winter cold. The biomass allocation to the different living and photosynthetic fractions of 3-year-old branches was studied monthly for a minimum of 13 months per species. Leaf area (LA, mm 2) and leaf mass per area (LMA, mg cm −2) measurements were used to characterize the diverse types of leaves of each species. Standing dead and senescent tissues accounted for a great percentage of the branch biomass of seasonally dimorphic species both during summer and winter. Different patterns of photosynthetic biomass allocation were found within the seasonally dimorphic species analysed. These patterns ranged from the moderate photosynthetic biomass oscillation of Salvia lavandulifolia to the almost deciduousness of Lepidium subulatum, and they were achieved by keeping alive, drying out or shedding different types of branches and leaves throughout the year. The formation of stress tolerant leaves and the reduction in the amount of photosynthetic biomass responded both to the occurrence of summer drought and winter cold. These results demonstrate that seasonal dimorphism is a flexible ecological strategy, as it comprises very different leaf phenologies and enables plants to escape both summer drought and winter cold.

Sex- and clock-controlled expression of the neuropeptide F gene in Drosophila.

Drosophila neuropeptide F (NPF), a homolog of vertebrate neuropeptide Y, functions in feeding and coordination of behavioral changes in larvae and in modulation of alcohol sensitivity in adults, suggesting diverse roles for this peptide. To gain more insight into adult-specific NPF neuronal functions, we studied how npf expression is regulated in the adult brain. Here, we report that npf expression is regulated in both sex-nonspecific and male-specific manners. Our data show that male-specific npf (ms-npf) expression is controlled by the transformer (tra)-dependent sex-determination pathway. Furthermore, fruitless, one of the major genes functioning downstream of tra, is apparently an upstream regulator of ms-npf transcription. Males lacking ms-npf expression (through tra(F)-mediated feminization) or npf-ablated male flies display significantly reduced male courtship activity, suggesting that one function of ms-npf neurons is to modulate fruitless-regulated sexual behavior. Interestingly, one of the ms-npf neuronal groups belongs to the previously defined clock-controlling dorsolateral neurons. Such ms-npf expression in the dorsolateral neurons is absent in arrhythmic Clock(Jrk) and cycle(02) mutants, suggesting that npf is under dual regulation by circadian and sex-determining factors. Based on these data, we propose that NPF also plays a role in clock-controlled sexual dimorphism in adult Drosophila.

Impact of androgen-induced oxidative stress on hypertension in male SHR

Men have higher blood pressure than women, and androgens and oxidative stress have been implicated as playing roles in this sexual dimorphism. The spontaneously hypertensive rat (SHR) is an animal model of both androgen- and oxidative stress-mediated hypertension. Therefore, the present studies were performed to test the hypothesis that androgens cause hypertension in SHR in part by stimulating superoxide production via NADPH oxidase. Castration of male SHR reduced blood pressure by 15% and attenuated both basal and NADPH-stimulated superoxide production in kidney cortical homogenates. Expression of p47(phox) and gp91(phox) but not p22(phox) subunits of NADPH oxidase were significantly lower in kidney cortex from castrated males compared with intact males. Moreover, inhibition of NADPH oxidase with apocynin caused approximately 15 mmHg reduction in blood pressure and reduced basal and NADPH-stimulated superoxide production in intact male SHR, but had no effect on blood pressure or superoxide production in castrated males. These data support the hypothesis that androgens cause oxidative stress and thereby increase blood pressure in male SHR via an NADPH oxidase-dependent mechanism.

The Ambient pH Response Rim Pathway in Yarrowia lipolytica: Identification of YlRIM9 and Characterization of Its Role in Dimorphism

Yarrowia lipolytica is a dimorphic fungus that secretes either an acidic or an alkaline protease depending on the environmental pH. Previous results have indicated that secretion of the alkaline protease is under control of the pH signaling Pal/Rim pathway originally described in Aspergillus nidulans. Several Y. lipolytica mutants defective in some Rim components of this pathway have been previously isolated and the RIM genes characterized. In the present study, Y. lipolytica RIM9 (palI) gene (YlRIM9) was sequenced from a plasmid (AL414126) of the Genolevures project (the DNA sequence data for YlRIM9 gene has been deposited at EMBL with accession number AJ566902). The derived translation product contains 724 amino acids with a predicted signal peptide and four transmembrane domains in its N-terminal region. We demonstrated that mutation in YlRIM9, as well as in other genes encoding members of the Pal/Rim pathway, did not affect the pH-dependent dimorphic transition of Y. lipolytica. A different pathway must exist in this fungus that controls the effect of pH on dimorphism.

STE11disruption reveals the central role of a MAPK pathway in dimorphism and mating inYarrowia lipolytica

Yarrowia lipolytica is a dimorphic fungus whose morphology is controlled by several factors such as pH and different compounds. To determine if the STE11-mitogen-activated protein kinase (MAPK) pathway plays a role in dimorphism of Y. lipolytica, we isolated the gene encoding a Mapkkk. The isolated gene (STE11) has an ORF of 2832 bp without introns, encoding a protein of 944 amino acids, with a theoretical Mr of 100.9 kDa, that exhibits high homology to fungal Mapkkks. Disruption of the STE11 gene was achieved by the pop-in/pop-out procedure. Growth rate and response to osmotic stress or agents affecting wall integrity were unaffected in the deleted mutants, but they lost the capacity to mate and to grow in the mycelial form. Both alterations were reverted by transformation with the wild-type STE11 gene. The Y. lipolytica STE11 gene driven by two different promoters was unable to complement Saccharomyces cerevisiae ste11Delta mutants, although the gene was transcribed. Also, a wild-type MAPKKK gene from Ustilago maydis failed to complement Y. lipolyticaDeltaste11 mutants. Both negative results were attributed to a failure of the transgenic gene products to interact with the corresponding regulatory and scaffold proteins. This hypothesis was supported by the observation that a truncated version of the U. maydis MAPKKK gene reversed mating and dimorphic defects in the mutants. All these results demonstrate that the MAPK pathway is essential for both morphogenesis and mating in Y. lipolytica.

Steroid 5α-reductase isozymes in the adult female rat brain: central role of dihydrotestosterone

The enzyme 5alpha-reductase (5alpha-R) (EC 1.3.99.5) exists as two isoforms, 5alpha-R type 1 (5alpha-R1) and 5alpha-R type 2 (5alpha-R2). 5alpha-R1 has been associated with catabolic functions whereas 5alpha-R2 has been associated with sexually dimorphic functions of the male. We recently demonstrated that both 5alpha-R isozymes are present in the central nervous system (CNS) of the adult male rat and are regulated in an opposing way by androgens. This finding raises the question as to whether both isozymes play a role in the sexual dimorphism of the CNS, besides other functions. To test this hypothesis, it is essential to study the regulation of both isozymes by androgens in the female. In this work, we studied the effects of testosterone (T) and dihydrotestosterone (DHT) on mRNA levels of both 5alpha-R isoforms in the prefrontal cortex of the adult female rat by one-step quantitative RT-PCR coupled with laser-induced fluorescence capillary electrophoresis. Our results demonstrate for the first time that 5alpha-R2 mRNA is slightly regulated by T and DHT in females. Surprisingly, 5alpha-R1 mRNA is not regulated by T in the intact female, whereas it is very positively regulated by DHT, a more potent androgen than T. These data indicate the great sexual dimorphism in the CNS with respect to both 5alpha-R isozymes, and suggest a crucial role of DHT in the sexual dimorphism of the CNS in the female. These results open up a new research line that may lead to a better understanding of the physiology of the CNS.

Castration inhibits exercise-induced accumulation of Hsp70 in male rodent hearts

Intense exercise leads to accumulation of the inducible member of the 70-kDa family of heat shock proteins, Hsp70, in male, but not female, hearts. Estrogen is at least partially responsible for this difference. Because androgen receptors are expressed in the heart and castration leads to decreases in calcium regulatory proteins and altered cardiac function, testosterone (T) or its metabolites could also be involved. We hypothesized that removal of endogenous T production through castration would reduce cardiac Hsp70 accumulation after an acute exercise bout, whereas castrated animals supplemented with 5alpha-dihydrotestosterone (DHT) would show the intact male response. Fifty-four 8-wk-old male Sprague-Dawley rats were divided into intact, castrated, or castrated + DHT groups (n = 18/group). At 11 wk of age, 12 animals in each group undertook a 60-min bout of treadmill running at 30 m/min (2% incline) while the remaining 6 in each group remained sedentary. At 30 min or 24 h after exercise (n = 6/time point), blood and hearts were harvested for analysis. Serum T was undetectable in castrated and DHT-treated castrated rats, whereas serum DHT was significantly reduced in castrated animals only (approximately 60% reduction) (P < 0.05). Although there were no differences in constitutive levels of Hsp70 protein, exercise significantly increased cardiac hsp70 mRNA and protein in intact and DHT-supplemented rats, but not in castrated animals (P < 0.05). To examine whether castration eliminated the ability to respond to stress, another six intact and six castrated animals were subjected to a 15-min period of hyperthermia (core temperature raised to 42 degrees C) and killed 24 h later. As opposed to exercise, castrated animals subjected to heat shock exhibited increases in Hsp70 above nonshocked (i.e., sedentary) animals, similarly to intact males (P < 0.05). These data suggest that androgens, in addition to estrogen, play a role in the sexual dimorphism observed in the stress response to exercise but not heat shock.

Role of the renal nerves in blood pressure in male and female SHR

Female spontaneously hypertensive rats (SHR) have lower blood pressures than males. The renin-angiotensin system plays an important role in the sexual dimorphism of blood pressure in SHR. The sympathetic nervous system can stimulate renin release, and, therefore, the present study was performed to determine whether the renal sympathetic nerves play a role in the sexual dimorphism of blood pressure in SHR. Male and female SHR underwent bilateral kidney denervation or sham surgery, and, 2 wk later, mean arterial pressure (MAP) and pulse interval were recorded, and baroreflex sensitivity (BRS) was measured by the sequence technique. Left ventricle index (LVI) was also calculated. MAP was higher in sham-operated males than females (182 +/- 5 vs. 169 +/- 4 mmHg; P < 0.01), but, despite the higher MAP in males, LVI was significantly greater in female rats. BRS was not different between sham-operated male and female SHR. Following bilateral renal denervation, MAP was decreased by a similar percentage (8-10%) in males (169 +/- 2 mmHg) and females (152 +/- 3 mmHg), whereas LVI was reduced only in female SHR. BRS was not altered by renal denervation in either sex. These data indicate that renal nerves play a role in the control of blood pressure in SHR independent of sex, but do not play a role in mediating the sex differences in blood pressure.