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.

An autoradiographic analysis of ascending projections from the medullary reticular formation in the rat.

Ascending projections from the several nuclei of the medullary reticular formation were examined using the autoradiographic method. The majority of fibers labeled after injections of [3H]leucine into nucleus gigantocellularis ascended within Forel's tractus fasciculorum tegmenti which is located ventrolateral to the medial longitudinal fasciculus. Nucleus gigantocellularis injections produced heavy labeling in the pontomesencephalic reticular formation, the intermediate layers of the superior colliculus, the pontine and midbrain central gray, the anterior pretectal nucleus, the ventral midbrain tegmentum including the retrorubral area, the centromedian-parafascicular complex, the fields of Forel/zona incerta, the rostral intralaminar nuclei and the lateral hypothalamic area.

Spinal projections of the gigantocellular reticular formation in the rat. Evidence for projections from different areas to laminae I and II and lamina IX.

We have used the autoradiographic method to study the organization of spinal projections from the gigantocellular reticular nucleus in the rat. Of particular note was the evidence obtained for projections to laminae I, II and IX. Reticular projections to laminae I and II arise more rostrally in Gi than those to lamina IX.

Serotonergic innervation of the forebrain in the North American opossum.

The forebrain distribution of axons showing serotonin-like immunoreactivity was studied in the North American opossum. Serotonergic innervation of the hypothalamus was extensive, particularly within the ventromedial nucleus, the periventricular nucleus and the rostral supraoptic nucleus. Serotonergic axons were also present within the fields of Forel and zona incerta, but they tended to avoid parts of the subthalamic nucleus.

A double-labelling study of reticular collaterals to the spinal cord and cerebellum of the North American opossum.

Injections of horseradish peroxidase into either the spinal cord or cerebellum label neurons in the gigantocellular and lateral reticular nuclei of the North American opossum. In order to determine if neurons which project to the spinal cord and cerebellum are intermingled in these two nuclei and if single neurons provide collaterals to both areas, we have employed fluorescent markers in double-labelling experiments. Our results show that reticular neurons innervating either the spinal cord or cerebellum are often close together and that a few provide collaterals to both areas.

A study of overlap and collateralization of bulbar reticular and raphe neurons which project to the spinal cord and diencephalon of the North American opossum.

Labeled neurons were found in most reticular and raphe nuclei of the opossum's medulla after horseradish peroxidase (HRP) injections into either the spinal cord or diencephalon. The labeling produced by spinal injections differed somewhat from that produced by diencephalic ones, but HRP-positive neurons were found in what appeared to be comparable areas. In order to study the intermingling of bulbospinal and bulbodiencephalic neurons more directly, we used fluorescent markers (true blue, nuclear yellow and diamidino yellow dihydrochloride) in double-labeling experiments.

Anatomical demonstration of the location and collateralization of rubral neurons which project to the spinal cord, lateral brainstem and inferior olive in the North American opossum.

Rubral neurons innervating the spinal cord, the lateral brainstem and the inferior olivary nucleus have been identified in the North American opossum by the retrograde transport of horseradish peroxidase and fluorescent markers. Neurons which project to the spinal cord are found mainly in caudal and rostroventral parts of the red nucleus. In contrast, rubral neurons which innervate the facial nucleus and lateral areas of the medulla are most numerous rostrodorsally.