Sensory neurons in the spinal cord of nominal female embryos in the marine turtle Lepidochelys olivacea respond to shifts in incubation temperature:implications for temperature dependent sex determination

Gonadal determination in marine turtles depends on incubation temperature. The mechanisms that spark off this process remain unclear. Previously, we proposed that sensory nerves reaching the gonadal primordium in nominal female embryos of Lepidochelys (L) olivacea may sense and signal incubation temperature. These nerves could later trigger ovarian determination by releasing neurotransmitters in a code constructed based on the thermal information (Gutierrez-Ospina et al., Acetylcholinesterase-positive innervation is present at the undifferentiated stages of the sea turtle Lepidochelys olivacea embryo gonads: implications for temperature-dependent sex determination, J. Comp. Neurol. 410 (1999) 90-98). The hypothesis briefly described, however, has been recently refuted under weak theoretical grounds and experimental misinterpretations (see introduction). Here, we present preliminary results that show that nominal female embryos have sensory neurons located in the dorsal horn laminae I and II of the lumbar spinal cord that display increased c-Fos-like immuno-staining after being incubated either at 15°C or 50°C. Because these spinal neurons are the primary central target of dorsal root ganglion neurons that innervate the urogential crest, these observations keep open the possibility that gonadal sensory nerves indeed signal thermal information that could later be used to trigger or instruct ovarian specification in marine turtles.

Differential effect of biotin on carboxylase activity and mice skeletal muscle metabolism

In mammalian skeletal muscle there are four carboxylases involved in several biochemical processes like gluconeogenesis, tricarboxylic acid cycle anaplerosis, metabolism of fatty acids and metabolism of various amino acids. It has been shown that biotin deficiency reduces body weight at the expense of muscular mass. When necessary, the liver uses skeletal muscle protein to provide glucose and amino acids to organs in need of such compounds. In this paper we analyzed carboxylase specific activities in hind limb skeletal muscle of 3 weeks old BALB/c male mice, at 0, 1, 4, 7, and 14 days of a specific diet with different biotin concentrations. Biotin was used at 0.0, 1.8 or 98.2 mg per kg of food;and was referred to as biotin deficient, sufficient and supplemented, respectively. Water and food supply and consumption by the three groups of mice were the same. Therefore, the observed effects were directly related to biotin ingestion. The body weight of biotin supplemented mice was the same as the body weight of mice in the biotin sufficient group, while biotin deficiency caused body weight reduction after 7 days of biotin depletion. We found that the total protein concentration in the vastus lateralis muscle is associated with the biotin content in the diet. After 7 days, the muscle total protein content was lower in mice of the biotin deficient group while it was higher in the mice from the biotin supplemented group

Increased serotonin concentration and tryptophan hydroxylase activity in reproductive organs of copulator males:a case of adaptive plasticity

Individual male rats may systematically display or not copulatory behavior when paired with receptive females. Although these phenotypes are associated with differences in brain organization and function, they might also do so at the level of the reproductive organs. We then used high performance liquid chromatography to quantify serotonin concentration and the activity of tryptophan hydroxylase in the reproductive organs of copulator and non-copulator males. Sexual behavior display was compared between groups and parameters of fertility and reproductive fitness were determined for copulator males. Copulator males had higher concentrations of serotonin in the epididymis, testicle and ventral prostate than their non-copulator counterparts, as it was found for epididymal and testicular tryptophan hydroxylase activity. However, preliminary data shows that serotonin elevation occurs in copulator males only until they have accumulated several sexual encounters, so it might be a response to genital gratification or sexual rewarding. Interestingly, only epididymal serotonin concentration correlated with reproductive fitness, offspring number, mating success and seminal plug volume in copulator males. Our results support that copulator and non-copulator male rats feature a phenotype-specific serotoninergic tone in the epididymis, testicle and ventral prostate gland. The observation documenting that epididymal serotonin concentration correlated with parameters that monitor male fertility and reproductive fitness in copulator males predicts that epididymal factors increase their chances of parenting offspring.

Cortical columns(barrels)display normal size in the brain’s primary somatosensory cortex of mice carrying null mutations of the insulin receptor substrate 1 gene:A preliminary report

Circuits in barrels of the rodent brain’s primary somatosensory (S1) cortex build up following constructivist rules. Previous evidence in mice supports that the precise addition of barrel neuropil is promoted by insulin-like growth factor-1 (IGF-1). The signaling cascades mediating this response remain undetermined. To address whether the effects of IGF-1 upon the growth of S1 circuits are mediated by insulin receptor substrate-1 (IRS-1), we studied barrel size in adult mice having the IRS-1 gene knocked out (IRS-1 ko). Our results reveal that barrel size is similar between wild type and IRS-1 ko mice suggesting that IRS-1 is not essential for barrel circuitry growth. Hence, investigations aimed at exploring other substrates activated by IGF-1, namely IRS-2 and IRS-4, are needed to reveal signaling pathways that mediate the precise addition of S1 neuronal circuitry.

Studying Some Brain and Ovarian Morphological Traits in Diaglena spatulata Female Frogs Thriving in Conserved and Perturbed Habitats:A Preliminary Report and Its Implications for Amphibian Survival and Continuity

Amphibians are thought to be highly susceptible to perturbed environments. However, recent studies show that many of them are successful inhabitants of disturbed, fragmented habitats. The source of this resilience is yet unclear, but it may be the byproduct of having a robust phenotype and/or the result of phenotypic plasticity. We then assessed the contribution of each by evaluating cytological features of two brain nuclei that modulate reproductive behavior and of the ovary, using female specimens of the frog Diaglena spatulata prospering in conserved and disturbed areas of a tropical dry forest. Our results in the brain show that the medial amygdala, but not the preoptic area, had a reduced size in frogs collected in disturbed forests compared to specimens collected in conserved forests. Both brain nuclei displayed, however, neurons with a reduced size in frogs captured in disturbed forest patches. In contrast, ovarian cytological features were similar between groups. Our preliminary results lead us to propose that Diaglena spatulata female specimens might combine robust ovary and plastic brain’s phenotypic traits to confront disturbed environments. This, however, is still a working hypothetical framework that needs to be experimentally confirmed.