Provisional QTL for circadian period of wheel running in laboratory mice: quantitative genetics of period in RI mice.

Wheel running was monitored in B x D recombinant inbred (RI) mice under dark-dark (DD) conditions, and the mean circadian period was calculated for each strain. There were significant differences for this trait among B x D recombinant inbred strains (p < .0001) and a narrow-sense heritability of 21%. Analysis of strain means and variances indicates that at least four segregating loci contribute to the genetic variance for the free-running circadian period in this population. Correlation of the strain means for the circadian period of wheel running for each RI strain against the distribution of markers at over 1500 loci along the mouse genome identified a number of provisional quantitative trait loci (QTL). There were provisional QTL for wheel running at p < .001 on chromosome 11 and at p < .01 on chromosomes 1, 6, 9, 17, and 19. Most were in agreement with a second analysis done under similar conditions.     

Additivity in murine circadian phototransduction

Additivity in the circadian phototransduction system of the mouse has not been tested directly. Because of this, accurate prediction of circadian phase shifts elicited by polychromatic light stimuli cannot be derived from the results of studies using monochromatic light stimuli. This limitation also makes it impossible to deduce the relative contributions of the photoreceptive mechanisms (rods, cones and melanopsin-containing retinal ganglion cells) underlying circadian phototransduction in the mouse. Using nearly monochromatic light stimuli of different spectral composition, and combinations thereof, we demonstrated that murine circadian phototransduction exhibits additivity. Based on the locomotor activity phase shifts elicited by these stimuli, we developed the first quantitative assessment of the relative contributions of conventional and novel photoreceptive mechanisms for circadian functioning in the mouse.     

Aggression in male rats receiving anabolic androgenic steroids: effects of social and environmental provocation.

This study examined the effects of anabolic androgenic steroids (AAS) on aggression under different social and environmental conditions. Three AAS were tested in gonadally intact male rats: testosterone propionate (TP), nandrolone (ND), and stanozolol (ST). Doses of 5 mg/kg were given 5 times/week, with gonadally intact controls receiving vehicle only (propylene glycol). Animals received six weekly tests under each condition in a counterbalanced order. Results show that the three AAS differed in their ability to elicit aggression. Males receiving TP were more aggressive than controls, ND males were similar to controls, and ST males were less aggressive than controls. In the social and environmental provocation tests TP-treated males were more aggressive than other groups, but were able to discriminate between intact and castrated opponents and between their home cage and a neutral cage. In the environmental provocation test, TP males were also more aggressive against opponents when tested in the opponent's home cage. It is suggested that chronic exposure to high levels of TP does not eliminate the ability to discriminate between social or environmental cues, as might be expected if it induces a " 'roid rage." However, TP does increase the likelihood that the animal will respond with aggression/dominance in a provoking situation. All three AAS variably affected serum testosterone and LH levels, as well as testes, seminal vesicle, and prostate weights. No effect on body weight was observed.     

Circadian complexes: Circadian rhythms under common gene control

Summary Circadian rhythms for food and water consumption were measured in five inbred strains of mice under a photoperiod of 16 h light and 8 h dark (16:8 LD), and under constant light (LL).Significant strain differences were observed which indicate that a common gene difference, or set of differences inMus musculus influences both the phase angle () associating the rhythms with the light-dark cycle, and the periods (_LL) of circadian rhythms for food and water consumption. The biological clock mechanism influenced by this genetic variance is common to both food and water circadian rhythms, and differs among the five inbred strains. A positive genetic correlation was observed between the phase angle () and the period (_LL) of each rhythm. This observation can be understood in terms of a functional relationship between phase and period proposed by Pittendrigh and Daan (1976b) for the entrainment of a circadian oscillator by a light-dark cycle in nocturnal rodents.These results suggest that circadian rhythms for food and water consumption in mice are regulated by a common physiological mechanism, and would respond to natural selection as a single circadian complex under common gene control.     

An overview of malaria transmission from the perspective of Amazon Anopheles vectors

In the Americas, areas with a high risk of malaria transmission are mainly located in the Amazon Forest, which extends across nine countries. One keystone step to understanding the Plasmodium life cycle in Anopheles species from the Amazon Region is to obtain experimentally infected mosquito vectors. Several attempts to colonise Ano- pheles species have been conducted, but with only short-lived success or no success at all. In this review, we review the literature on malaria transmission from the perspective of its Amazon vectors. Currently, it is possible to develop experimental Plasmodium vivax infection of the colonised and field-captured vectors in laboratories located close to Amazonian endemic areas. We are also reviewing studies related to the immune response to P. vivax infection of Anopheles aquasalis, a coastal mosquito species. Finally, we discuss the importance of the modulation of Plasmodium infection by the vector microbiota and also consider the anopheline genomes. The establishment of experimental mosquito infections with Plasmodium falciparum, Plasmodium yoelii and Plasmodium berghei parasites that could provide interesting models for studying malaria in the Amazonian scenario is important. Understanding the molecular mechanisms involved in the development of the parasites in New World vectors is crucial in order to better determine the interaction process and vectorial competence.     

Ultrastructural localization of amiloride-sensitive sodium channels and Na+,K(+)-ATPase in the rat's olfactory epithelial surface

Several studies have indicated that olfactory responses are impeded byamiloride. Therefore, it was of interest to see whether, and if so which,olfactory epithelial cellular compartments have amiloride- sensitivestructures. Using ultrastructural methods that involved rapid freezing,freeze-substitution and low temperature embedding of olfactory epithelia,this study shows that, in the rat, this tissue is immunoreactive toantibodies against amiloride sensitive Na(+)- channels. However, microvilliof olfactory supporting cells, as opposed to receptor cilia, contained mostof the immunoreactive sites. Apices from which the microvilli sprout andreceptor cell dendritic knobs had much less if any of theamiloride-antibody binding sites. Using a direct ligand-bindingcytochemical method, this study also confirms earlier ones that showed thatolfactory receptor cell cilia have Na+, K(+)-ATPase. It is proposed thatsupporting cell microvilli and the receptor cilia themselves havemechanisms, different but likely complementary, that participate inregulating the salt concentration around the receptor cell cilia. In thisway, both structures help to provide the ambient mucous environment forreceptor cells to function properly. This regulation of the saltconcentration of an ambient fluid environment is a function that theolfactory epithelium shares with cells of transporting epithelia, such asthose of kidney.