Alternative mating tactics in the yellow dung fly: resolving mechanisms of small-male advantage off pasture.

Recent work suggests that the yellow dung fly mating system may include alternative patroller-competitor mating tactics in which large males compete for gravid females on dung, whereas small, non-competitive males search for females at foraging sites. Small males obtain most matings off pasture, yet the behavioural mechanism(s) giving rise to this pattern are unknown. We investigated the male and female behaviours that determine mating success in this environment by conducting field mating experiments and found small males to benefit from several attributes specific to the off-pasture mating environment.

Glial and glutamatergic markers in depression, alcoholism, and their comorbidity.

Background: Alteration of glutamatergic neurotransmission in the prefrontal cortex (PFC) may contribute to the pathophysiology of alcoholism and major depressive disorder (MDD). Among glial cells, astrocytes are mostly responsible for recycling synaptic glutamate by uptake through excitatory amino acid transporters 1 and 2 (EAAT1 and EAAT2), and conversion to glutamine with glutamine synthetase (GS). Low density of astrocytes in the PFC of "uncomplicated' alcoholics and MDD subjects may parallel altered glutamate transporters and GS in the PFC.

The origin of projections from the medullary reticular formation to the spinal cord, the diencephalon and the cerebellum at different stages of development in the North American opossum: studies using single and double labeling techniques.

We have employed the retrograde transport of horseradish peroxidase alone or conjugated to wheat germ agglutinin, to label neurons within the medullary reticular formation which project to the spinal cord, the diencephalon and the cerebellum at different stages of development in the North American opossum. At selected ages, the fluorescent markers Fast Blue and Diamidino Yellow were also used in double-labeling experiments to determine if single neurons innervate both the spinal cord and diencephalon or the spinal cord and cerebellum, presumably via axonal collaterals. The opossum was employed because it is born in a very immature state, 12 days after conception, and is thus available for injections at early stages of development.

Organization of forebrain projections from the medullary reticular formation in the North American opossum. Evidence for connectional heterogeneity.

We have employed axonal transport techniques to study the organization of projections from the medullary reticular formation (RF) to the forebrain of the North American opossum. The results of retrograde transport studies using large injections of horseradish peroxidase (HRP), wheat germ agglutinin conjugated to HRP (WGA-HRP), and fluorescent markers suggest that all nuclei of the medullary RF project to the forebrain although the parvocellular reticular nucleus makes only a very small contribution. When injections of 3H-leucine or WGA-HRP are centered within areas shown by the retrograde transport studies to innervate the forebrain, characteristic patterns of orthograde labeling are produced.

Development of brainstem and cerebellar projections to the diencephalon with notes on thalamocortical projections: studies in the North American opossum.

The North American opossum is born in a very immature state, 12 days after conception, and climbs into an external pouch where it remains attached to a nipple for an extended period of time. We have taken advantage of the opossum's embryology to study the development of brainstem and cerebellar projections to the diencephalon as well as the timing of diencephalic projections to somatosensory motor areas of neocortex. The techniques employed included immunocytochemistry for serotonin, the retrograde and orthograde transport of wheat germ agglutinin conjugated to horseradish peroxidase, and the selective impregnation of degenerating axons.