Biomedical subjects

P C Madtes

Publications and source records attributed to P C Madtes.

5 recordsLinked to original sources

PubMed1996

The temporal and spatial development of corticotropin-releasing factor (CRF) binding sites and CRF afferents in the opossum cerebellum.

The intent of this study is to determine the developmental timecourse of the appearance and distribution of corticotropin releasing factor (CRF) binding sites within the developing opossum cerebellum, and to correlate this with the temporal and spatial distribution of CRF-labeled axons. 125I-labeled ovine CRF was used to identify the distribution and temporal expression of CRF binding sites in the opossum cerebellum. By PD8, binding sites are evident over cells in the external granular layer, as well as the subjacent immature Purkinje cell layer, but not over the ventricular layer or the intermediate zone. At PD 8, the intermediate zone, located between the ventricular and immature Purkinje cell layers, contains migrating nuclear, Golgi and Purkinje cells. By PD12, binding sites are present over all layers of the immature cerebellum (the external granular layer, the multitiered Purkinje cell layer, and the intermediate zone of migrating cells), except the ventricular layer. The adult distribution of CRF binding sites is evident by PD30-38 which includes the molecular, Purkinje and internal granule cell layers. The present results provide the first account of the ontogeny of CRF binding sites in the developing cerebellum. The early expression and distribution of CRF receptors, when correlated with the temporal expression and distribution of the peptide, provide additional evidence to support our working hypothesis that CRF functions as a regulator of developmental events which is distinct from its proposed function as a neuromodulator in the mature cerebellum.

Afferent Pathways↗

PubMed1995

Distribution of corticotropin-releasing factor (CRF) binding sites in the opossum cerebellum.

Corticotropin-releasing factor (CRF) has been demonstrated in the hypothalamic-pituitary-adrenal axis and studied in extrahypothalamic sites throughout the brain. Localization of CRF immunoreactivity, CRF mRNA, and CRF receptors within specific brain areas supports an extrahypothalamic function for CRF. Previous reports have revealed the localization of several peptides, including CRF, in the cerebellar cortex and nuclei of the North American opossum (Didelphis marsupialis virginiana); climbing fibers, mossy fibers, and a beaded plexus of axons in the Purkinje cell layer demonstrate CRF immunoreactivity. CRF also is localized within neurons in the inferior olivary complex and other brainstem nuclei which are known to project to the cerebellar cortex. Physiological recordings indicate CRF potentiates the excitatory effects of both aspartate and glutamate, the putative transmitters of the major afferent inputs to the cerebellum. The present study reports that specific CRF binding sites are present in all lobules of the opossum cerebellar cortex, with the greatest density in vermal lobules V through X, the flocculus, and the paraflocculus. The cerebellar nuclei do not appear to be labeled. CRF binding sites are present over all neuronal layers of the cerebellar cortex. The presence of CRF immunoreactivity in climbing fibers, mossy fibers, and a beaded axonal plexus, and CRF binding sites within the cerebellar cortex, as well as the fact that CRF potentiates the excitatory effects of both aspartate and glutamate, indicate that this peptide may function as a neuromodulator in the cerebellum of the North American opossum. An attempt is made to correlate the distribution of CRF-IR neurons and fibers, CRF mRNA, and CRF receptors to the extrahypothalamic function of CRF as it relates to the olivocerebellar pathway.

Animals↗

PubMed1994

Distribution of cholecystokinin binding sites in the North American opossum cerebellum.

Previous studies in our laboratory have reported on the differential distribution of several neuropeptides, including the octapeptide cholecystokinin (CCK8), in the cerebellar cortex and nuclei of the North American opossum (Didelphis marsupialis virginiana). The present account reports on the distribution of CCK8 binding sites as determined from serial autoradiographic images of the cerebellum which were labelled by using [125I]Bolton Hunter sulfated CCK8. Evidence for the limited presence of CCK8-like immunoreactivity and CCK8 binding sites in several other species suggests that the distribution of this peptide and its receptor(s) may be species specific. In the opossum, CCK8-like immunoreactivity is present in mossy fiber terminals that distribute throughout the cerebellar cortex; it has a very limited distribution in climbing fibers (King and Bishop (1990) J. Comp. Neurol. 238, 373-384. CCK8 binding sites are present throughout all lobules of the cerebellar cortex and the cerebellar nuclei, which correlates well with the distribution of the peptide. CCK8-like immunoreactivity is located primarily in the granule cell layer, although the greatest density of binding sites is in the molecular layer. The presence of CCK8 is mossy fiber terminals, coupled with the presence of CCK8 binding sites in the cerebellar cortex, and the fact that CCK8 alters the firing rate of Purkinje cells (Madtes et al. (1992) Neurosci. Abstr. 18, 853) indicate this peptide may function as a neuromodulator in the cerebellum of the North American opossum.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1986

Rhizobins, a group of peptides in the free-amino-Acid pool of the soybean-Rhizobium system.

Free-living Rhizobium (according to Bergey's Manual of Systematic Bacteriology, [1984, The Williams & Wilkins Co., Baltimore], Bradyrhizobium) japonicum was found to release a peptide into the nutrient media. Soybean nodules contained this peptide and exuded it into the soil. The name "rhizobin A" is suggested for this peptide. Nodules also contained another peptide, rhizobin B, as well as an unidentified, ninhydrin-positive compound, rhizobin C. The three peptides were confined to the free-amino-acid pool of the soluble fraction and eluted consecutively from a cation-exchange column. Rhizobin A was isolated in a highly purified form; its molecular mass was approximately 1,600 daltons as determined by Sephadex gel filtration and mass spectrometry. The amino-acid composition could be determined only approximately, because a long time was necessary for acid hydrolysis, possibly due to unusual linkages. The rhizobin concentration in soybean nodules continually increased during 50 days of growth, from 2 to approximately 400 mug/g (fresh weight). When combined nitrogen was added to nodulated soybean and subsequently removed, nitrogenase activity, nodulation, and nodule growth first decreased and then recovered. The relative amount of rhizobin A followed a similar pattern. Rhizobins were not detected in the roots, stems, and leaves of nodulated soybean plants. They were present in Lupinus nodules, but absent in alder nodules.

Journal Article↗

PubMed1983

Synaptic interactions in the GABA system during postnatal development in retina.

Using biochemical analyses, we have demonstrated the presence of a high-affinity, sodium- and temperature-dependent uptake system for GABA in the retinas of newborn rabbits. The activity of this system two days after birth is approximately 70 percent of adult values, slowly increasing to adult level by postnatal day 6-8. An intraocular injection nipecotic acid (final concentration = 10 mM) into one-day-old rabbit pups resulted in a 60 percent inhibition in uptake activity. In order to study the possible role of the GABA uptake system in retinal development, we have determined the consequences of blocking GABA uptake with nipecotic acid on the postnatal development of post-synaptic GABA receptors, as measured by 3H-muscimol binding. Nipecotic acid treatment caused a significant increase in receptor binding in retinas prior to eye opening, with the maximal stimulation being one day after the intraocular injection. Our data indicate that the development of GABA receptor sites is influenced by the activity of the GABA uptake system and suggest that GABA may function as a trophic factor in the developing rabbit retina.

Animals↗