The effects of mate separation on pair re-formation in the Texas cichlid fish (Cichlasoma cyanoguttatum)

This study tested whether mated pairs of Texas cichlid ($\text{Cichlasoma cyanoquttatum}$) would reform and continue rearing their offspring after being separated for either one, four, or ten days. All pairs successfully re-formed after one day, while only 50% re-formed after 4 days. No pair re-formed after 10 days of separation. In successfully re-formed pairs, the female was always more aggressive than her mate, irrespective of whether the female was the resident or the returning individual. Aggressiveness seemed related to the female's attempt to control the male's parental behavior. For pairs which did not re-form, the resident parent, either the male or female, violently and continously attacked the returned mate.     

Effect of cultural inheritance of reproductive compensation on the incidence of a sex-linked lethal disease

For a sex-linked recessive lethal disease, a model is constructed to study reproductive compensation for having at least one normal male with partial cultural inheritance. The equilibrium frequency of heterozygous females depends on the probability that a female offspring of the compensating parents will not compensate, α, the probability that a female offspring of the non-compensating parents will compensate, β, and the mutation rate, u. When α = 0, the equilibrium frequency of heterozygous females is given by √2u, whereas when α ≠ 0 it is given by 2[{β +(2α + β) (α + β)}/{α(α + β)}]u.Then, the proportion of affected males due to fresh mutations is much smaller than Haldane's estimate of $\text{1}\text{3}$ without reproductive compensation.     

Ethanol-induced inhibitions of testicular steroidogenesis in the male rat: Mechanisms of actions

Ethanol markedly inhibits the biosynthesis of testosterone in the male of several species. Since several $\text{in vitro}$ studies have suggested that ethanol $\text{per se}$ is not a gonadal toxin and that it must be metabolized to exert its effects, we examined this possibility under $\text{in vivo}$ conditions in the present studies. We found that the administration of the alcohol dehydrogenase inhibitor, pyrazole, to adult male rats significantly elevated blood ethanol levels. However, rather than resulting in a potentiation of the effects of ethanol on testicular steroidogenesis, pyrazole-induced elevations in blood ethanol concentrations produced a significant attenuation of ethanol's effects. In view of these observations, it is difficult to maintain that ethanol itself is responsible for inhibiting the production of testosterone. On the contrary, our results may provide the first $\text{in vivo}$ support for the hypothesis that ethanol must be metabolized to exert its effects on testicular steroidogenesis.     

Parent-offspring conflict that is not limited by degree of kinship

Models are presented showing that, under certain conditions, when multiple offspring are reared simultaneously, the magnitude of offspring selfishness is independent of offspring-offspring genetic relatedness. When the cost (θ) of the selfish offspring's behavior approaches zero, alleles causing offspring selfishness spread as long as $\text{c}\text{b}$ is positive.In general, simultaneous offspring are predicted to behave more selfishly than sequential offspring.Stable equilibria between alleles for selfish and non-selfish behavior are predicted for certain selfish alleles.     

Biliary metabolites of testosterone and testosterone glucosiduronate in the rat

A mixture of testosterone-4-¹⁴C and testosterone-1,2-³H-17-glucosiduronate was intraperitoneally administered into male and female rats with bile fistulas. Biliary metabolites were separated and purififd by a combination of column chromatography, enzymic hydrolysis or solvolysis of the conjugate fractions and identification of the liberated aglycones. The injected steroids were extensively metabolized and excreted predominantly in the blue. 5β-Androstane-3α, 17β-diol was found principally in monoglucosiduronate fraction and was produced preferentially from the injected conjugate in both sexes. Very marked sex differences from the injected conjugate in both sexes. Very marked sex differences were observed in the following metabolites: Androsterone was present only in the female as monoglucosidironate, which was preferentially derived from testosterone. 5α-Androstane-3α,17β-diol was identified in both monoglucosiduronate and diconjugate fractions of the female, which was formed significanrly more from the conjugate than testosterone. These findings provide evidence that testosterone glucosiduronate could be converted directly into 5α-steroids as well as 5β-ones $\text{in}$$\text{vivo}$. In marked contrast, the major portion of testosterone was metabolized to polar steroids in the male.     

The development of lactate and malate dehydrogenases in the C57BL-6 mouse kidney

The development of lactate dehydrogenase (LDH; EC 1.1.1.27) and malate dehydrogenase (MDH; EC 1.1.1.37) was measured in the kidney of male and female $\text{C57BL}\text{6}$ mice from ages prenatal 16 days to 80 days. Maximum reactions rates of the enzymes were measured in vitro by following the reduction of the nicotinamide-adenine dinucleotide spectrophotometrically.Analysis of variance showed no significant sex difference for LDH and MDH. There was a significant sex difference for the ratio LDH:MDH and a significant age difference for LDH, MDH, and the ratio LDH:MDH. In the male and female, LDH activity increased from prenatal 16 days to 30 days. Malate dehydrogenase activity reached adult values at 22 days in the male and at 30 days in the female. The ratio LDH:MDH in the male decreased from prenatal 16 days to 3 days, after which the ratio continued to decline to 20 days at a less rapid rate. This general pattern was also found in the female followed by a further decline in the ratio at 50 days.The development of LDH and MDH in the $\text{C57BL}\text{6}$ mouse is tissue specific and probably parallels the development of the tissue's function. In the case of the kidney, LDH and MDH development may reflect maturation of mitochondrial function and the kidney's ability to concentrate urine.     

Interactions of chlorinated hydrocarbon pesticides with the 8S estrogen-binding protein in rat testes

The effect of certain DDT analogs on the binding of ³H-estradiol to the 8–9S estrogen binding protein of rat testicular cytosol was studied by sucrose sedimentation analysis. The binding of ³H-estradiol to testicular cytosol was inhibited by o,p'DDT, a DDT analog which is estrogenic in the intact female, but not by p,p'DDE which is a nonestrogen in the female. The pesticide methoxychlor, which is estrogenic $\text{in vivo}$ in the female, failed to inhibit ³H-estradiol binding, presumably requiring metabolic activation for binding to the testicular cytosol. In fact, its di-demethylated metabolite 2,2-bis(p-hydroxyphenyl)-1, 1,1-trichloroethane (HPTE), also estrogenic $\text{in vivo}$, caused $\text{marked}$ suppression of ³H-estradiol binding.     

Exposure of embryos to an aromatization inhibitor increases copulatory behaviour of male quail

This experiment examined the possibility that endogenous embryonic androgen contributes to sexual differentiation of behaviour in male or female quail ($\text{Coturnix}$$\text{coturnix}$$\text{japonica}$), and that it does so via aromatization (conversion to oestrogen). Eggs were injected on day 9 of incubation with oil or ATD (an aromatization inhibitor). As adults, males and females were exposed to short days, injected with testosterone propionate, tested for male-typical behaviour, then injected with oestradiol benzoate and tested for female-typical receptivity. ATD increased the level of male-typical copulatory behaviour in males. Male-typical behaviour in females was not affected, nor was female-typical behaviour in either sex. Thus normal male quail are actually slightly demasculinized by their own androgen during embryonic development, and this process is mediated by aromatization.     

Characterizations and constructions of reverberating networks

Consider the family $\text{G}$_n of all n neuron networks whose dynamical behaviors are described by Caianiello's neuronic equations, and also its subfamily $\text{R}$_n of all reverberating networks each of whose neuronic equations have only periodic solution (states), i.e., without having any transient states. This paper is specifically concerned with characterizations of the subfamily $\text{R}$_n. First, we show that $\text{R}$_n is contained in a subfamily $\text{S}$_n of $\text{G}$_n consisting of all self-dual networks. We introduce Chow's matrix corresponding to each network of $\text{S}$_n, using Chow parameters and some algebraic operations {$\text{2}$_α} applied to the coefficient matrix of the network in $\text{S}$_n, such as interchanges of coefficients between two neurons or changes of their signs. Then we give some necessary conditions on Chow's matrix under which any network in $\text{S}$_n belong to $\text{R}$_n, and a necessary and sufficient condition on the coefficient matrix. We also discuss relations between Chow's matrix and the maximum period of reverberations. In particular, it is shown that Chow's matrix of a network in $\text{R}$_n is symmetric if and only if the maximum period of reverberations is less than three. By virtue of these results, we propose two methods of construction of networks in $\text{R}$_n. The first method is an inductive construction. The second is based on the algebraic operations.     

The estrogenic activity of DDT: Invivo and invitro induction of a specific estrogen inducible uterine protein by o,p'-DDT

The pesticide o,p'-DDT stimulates the production of a specific uterine protein, the so-called induced protein or IP, normally associated with an estrogenic response of the uterus. $\text{In}$$\text{vivo}$ stimulation of IP production is observed 1 hour after the administration of 250 mg/kg of o,p'-DDT to immature rats. $\text{In}$$\text{vitro}$ stimulation of IP production is observed after a 1 hour incubation of uteri with 100 μM o,p'-DDT. This $\text{in}$$\text{vitro}$ response is blocked by Actinomycin D. In contrast to o,p'-DDT, which binds to the cytoplasmic estrogen receptor and stimulates IP production, p,p'-DDT which does not bind well to the estrogen receptor does not stimulate IP production $\text{in}$$\text{vitro}$. These findings represent the first report of an estrogenic effect of o,p'-DDT in a completely $\text{in}$$\text{vitro}$ system.     

In vitro androgen metabolism in mouse kidney: High 3-keto-reductase (3α-hydroxysteroid dehydrogenase) activity relative to 5α-reductase

The $\text{in vitro}$ metabolism of testosterone and dihydrotestosterone was studied in slices and cell fractions of mouse kidney. When testosterone was used as substrate, very little metabolism to dihydrotestosterone occurred suggesting very low 5α-reductase activity. When dihydrotestosterone was substrate, it was rapidly converted to 5α-androstane-3α, 17β-diol by a potent 3-keto-reductase. Ninety-five percent of this latter enzyme is located in cytosol and it requires NADPH as cofactor. The 3-keto-reductase may exist in two molecular forms which can be separated by polyacrylamide gel electrophoresis. Form A and B have mean molecular radii which correspond to molecular weights of 38, 700 and 28, 700, respectively. Sufficient 3-keto-reductase activity is present in cytosol at 0°C to reduce physiological concentrations (2×10^?9 M) of dihydrotestosterone without the addition of cofactor. 3-Keto-reductase activity is higher in intact male than in castrate male or female mice and increases with androgen treatment.From these studies we conclude: (a) The virtual absence of 5α-reductase in mouse kidney is consistent with the thesis that testosterone rather than dihydrotestosterone may be the intracellular androgen in this organ. (b) Kinetic studies which depend upon the $\text{in vitro}$ uptake and retention of dihydrotestosterone by receptor proteins may be difficult to interpret due to rapid metabolism of ligand.     

Effects of naloxone and acetylcholine on medial thalamic and cortical units in naive and morphine dependent rats.

The administration of 0.5 mg of testosterone propionate (TP) for 3 days to castrated male rats caused ³H-leucine incorporation into pineal proteins to increase significantly by 79%. TP effects depended on time of administration; rats receiving TP at 06.00 h exhibited a significant 150% increase in pineal protein synthesis 24 h later whereas rats injected at 14.00 h only showed a 54% increase in ³H-leucine incorporation into proteins. Superior cervical ganglionectomy decreased pineal testosterone uptake $\text{in vitro}$ by 21% and pineal protein synthesis by 27%; in addition it blocked the stimulatory effects of TP on protein synthesis. Ganglionectomy also modified the $\text{in vitro}$ metabolism of testosterone by pineal cells; it increased the amounts of ³H-androstenedione and decreased ³H-5∝-androstanedione extracted from pineal glands incubated with ³H-testosterone. These results indicate that the sympathetic nervous input reaching the pineal via the superior cervical ganglia is important to modulate the early steps of androgen action on the pinealocytes.     

In vitro androgen metabolism in mouse kidney: high 3-keto-reductase (3alpha-hydroxysteroid dehydrogenase) activity relative to 5alpha-reductase

The $\text{in vitro}$ metabolism of testosterone and dihydrotestosterone was studied in slices and cell fractions of mouse kidney. When testosterone was used as substrate, very little metabolism to dihydrotestosterone occurred suggesting very low 5α-reductase activity. When dihydrotestosterone was substrate, it was rapidly converted to 5α-androstane-3α, 17β-diol by a potent 3-keto-reductase. Ninety-five percent of this latter enzyme is located in cytosol and it requires NADPH as cofactor. The 3-keto-reductase may exist in two molecular forms which can be separated by polyacrylamide gel electrophoresis. Form A and B have mean molecular radii which correspond to molecular weights of 38,700 and 28,700, respectively. Sufficient 3-keto-reductase activity is present in cytosol at 0°C to reduce physiological concentrations (2×10^?9 M) of dihydrotestosterone without the addition of cofactor. 3-Keto-reductase activity is higher in intact male than in castrate male or female mice and increases with androgen treatment.From these studies we conclude: (a) The virtual absence of 5α-reductase in mouse kidney is consistent with the thesis that testosterone rather than dihydrotestosterone may be the intracellular androgen in this organ. (b) Kinetic studies which depend upon the $\text{in vitro}$ uptake and retention of dihydrotestosterone by receptor proteins may be difficult to interpret due to rapid metabolism of ligand.     

A theoretical study of calcium entry in nerve terminals, with application to neurotransmitter release

In his study of a kin selection model for the evolution of workers' behavior in an incipiently social insect, Craig (1979) found that the haplodiploid mode of sex determination, combined with a female-biased sex ratio, cannot accelerate an evolutionary trend toward eusociality. This seems to contradict to Hamilton's (1964) theory. It is my intention to prove that Craig's result is due to the dependence of relative reproductive success in each sex on the sex ratio of a population. The oviposition of unfertilized eggs by workers is indispensable, in primitive stages in the evolution of eusociality, for maintaining the relative reproductive success of a female. Assuming that workers control the sex ratios, we can distinguish the following three evolutionary phases in accordance with the ratio $\text{N}{}_2\text{N}{}_{10}$ (the ratio of the number of the queen's second brood to that of the progeny laid by workers derived from the same nest). During Phase 1 in which $\text{N}{}_2\text{N}{}_{10}$ < $\text{1}\text{2}$, the reproductive successes of a male and a female are equal, and Hamilton's rule holds. In Phase 2 in which $\text{1}\text{2 <}\text{N}{}_2\text{N}{}_{10}\text{<}\text{3}\text{2}$, the queen produces females, and workers oviposit males. As $\text{N}{}_2\text{N}{}_{10}$ increases, the sex ratio in the whole population becomes female-biased and relative reproductive success of a male increases. In Phase 3 in which N₂/N₁₀ >$\text{3}\text{2}$, the queen lays some male eggs in addition to female eggs. The sociality threshold ($\text{B}\text{C}$)_crit the minimum value of the benefit/cost ratio leading to the evolution of altruism, is $\text{2}\text{3}$on Phase 1. It rises threefold as N₂/N₁₀ increases in Phase 2, and, in Phase 3, it is twice as high as that in a diploid species. The anatomical and physiological characteristics of workers must have been so developed that they are efficient in helping activities after the beginning of eusociality. The evolutionary process before the beginning of helping behavior is also discussed. The egg laying by unmated females, which stay their mother's nest, seems to have been an important preadaptation for the evolution of eusociality in Hymenoptera.     

Stimulation of leydig cell testoterone secretion in vitro and in vivo in hypophysectomized rats by an agonist of luteinizing hormone releasing hormone

Injection of a luteinizing hormone-releasing hormone (LHRH) agonist into 55-day-old male rats which had been hypophysectomized 3 days earlier resulted in a 10- to 30-fold increase in the levels of testosterone in serum and testicular interstitial fluid (IF) in the 4h following injection. The levels achieved were within or above the normal range for intact untreated rats of this age. In similar animals, injection of LHRH agonist also enhanced the serum testosterone response to injected hCG at $\text{1}\text{1}\text{2}\text{h}$, but not at later times after injection, and by 24h reduced IF levels of testosterone suggested that LHRH agonist had begun to inhibit stimulation by hCG. $\text{In vitro}$, dispersed Leydig cells from untreated hypophysectomized rats showed a 2-fold increase in testosterone responsiveness to LHRH agonist when compared to cells from intact rats, and this change was associated with an 80% increase in the number of Leydig cell LHRH-receptors.     

Testosterone Increases Susceptibility to Amebic Liver Abscess in Mice and Mediates Inhibition of IFNγ Secretion in Natural Killer T Cells

Amebic liver abscess (ALA), a parasitic disease due to infection with the protozoan Entamoeba histolytica, occurs age and gender dependent with strong preferences for adult males. Using a mouse model for ALA with a similar male bias for the disease, we have investigated the role of female and male sexual hormones and provide evidence for a strong contribution of testosterone. Removal of testosterone by orchiectomy significantly reduced sizes of abscesses in male mice, while substitution of testosterone increased development of ALA in female mice. Activation of natural killer T (NKT) cells, which are known to be important for the control of ALA, is influenced by testosterone. Specifically activated NKT cells isolated from female mice produce more IFNγ compared to NKT cells derived from male mice. This high level production of IFNγ in female derived NKT cells was inhibited by testosterone substitution, while the IFNγ production in male derived NKT cells was increased by orchiectomy. Gender dependent differences were not a result of differences in the total number of NKT cells, but a result of a higher activation potential for the CD4⁻ NKT cell subpopulation in female mice. Taken together, we conclude that the hormone status of the host, in particular the testosterone level, determines susceptibility to ALA at least in a mouse model of the disease.     

Tyrosine's pressor effect in hypotensive rats is not mediated by tyramine

Tyrosine, the amino acid precursor of catecholamines, increases blood pressure (BP) in hemorrhaged hypotensive rats. Since tyrosine may also be decarboxylated to form $\text{tyramine}$^∞, which releases norepinephrine from sympathetic terminals, we tested the hypothesis that $\text{tyramine}$ formation might mediate tyrosine's ability to increase BP. Three lines of evidence indicate that tyrosine does not act via this mechanism: pretreatment with reserpine blocked $\text{tyramine's}$ but not tyrosine's pressor activity; pretreatment with hexamethonium left $\text{tyramine's}$ effect intact but blocked the pressor response to tyrosine; and plasma $\text{tyramine}$ did not increase after an hemodynamically-active dose of tyrosine (100 mg/kg).     

Ribosomal proteins L1, L17 and L27 from Escherichia coli localized at single sites on the large subunit by immune electron microscopy

Three-dimensional locations have been determined for Escherichia coli ribosomal proteins L1, L17 and L27 by immune electron microscopy using antibodies directed against these proteins. From the positions of immunoglobulin G attachment, observed in two characteristic projections, it was determined that these three proteins are located at single sites in different regions on the surface of the large subunit. In the quasisymmetric projection, L1 maps on the side opposite the “$\text{L}\text{7}\text{L}\text{12}$ stalk,” named the L1 ridge; protein L17 maps at the base of the subunit opposite the “central protuberance” (toward the $\text{L}\text{7}\text{L}\text{12}$ side of the subunit); and protein L27 is found on the central protuberance (on the side distal to the $\text{L}\text{7}\text{L}\text{12}$ stalk). In the asymmetric projection, proteins L1 and L27 are found on the surface of the subunit contracting the small subunit and protein L17 is on the surface of the subunit distal to the small subunit; i.e. on the cytoplasmic surface of the large subunit. Antibody binding at all three sites was eliminated when the immunoglobulin G molecules were preabsorbed with their specific proteins.     

Birth sex ratio in captive mammals: Patterns,biases, and the implications for management and conservation

Sex allocation theory predicts that a female should produce the offspring of the sex that most increases her own fitness. For polygynous species, this means that females in superior condition should bias offspring production toward the sex with greater variation in lifetime reproductive success, which is typically males. Captive mammal populations are generally kept in good nutritional condition with low levels of stress, and thus populations of polygynous species might be expected to have birth sex ratios biased toward males. Sex allocation theory also predicts that when competition reduces reproductive success of the mother, she should bias offspring toward whichever sex disperses. These predicted biases would have a large impact on captive breeding programs because unbalanced sex ratios may compromise use of limited space in zoos. We examined 66 species of mammals from three taxonomic orders (primates, ungulates, and carnivores) maintained in North American zoos for evidence of birth sex ratio bias. Contrary to our expectations, we found no evidence of bias toward male births in polygynous populations. We did find evidence that birth sex ratios of primates are male biased and that, within primates, offspring sex was biased toward the naturally dispersing sex. We also found that most species experienced long contiguous periods of at least 7 years with either male‐ or female‐biased sex ratios, owing in part to patterns of dispersal (for primates) and/or to stochastic causes. Population managers must be ready to compensate for significant biases in birth sex ratio based on dispersal and stochasticity. Zoo Biol 19:11–25, 2000. © 2000 Wiley‐Liss, Inc.