Biomedical subjects

R Kapoor

Publications and source records attributed to R Kapoor.

At least 217 records · Page 12Linked to original sources

PubMed1988

Electrophysiology of the mammalian cerebellar cortex in organ culture.

A direct comparison was made between the electrical properties of rat Purkinje cells in cerebellar organotype cultures and those in acute slices from age-matched animals. Cultures were prepared from 9-11-day-old animals. Intracellular recordings were made 5-12 days later, at which time the folia architecture of the cerebellum was still well preserved. The resting membrane potentials and input resistances of Purkinje cells in cultured and acute slice preparations from young animals were comparable to those of mature Purkinje cells in slices. Neurons from animals younger than 14 days differed from mature Purkinje cells in that they fired at low frequencies in response to outward current pulses. The latter property was found in all cultured neurons studied, independent of their time in culture. These action potentials were generated by Na+ and Ca2+ conductances as shown by the application of selective channel blockers. Cultured or acute slice preparations from animals younger than 11 days shared other immature electroresponsive features. In both groups, Na+-dependent plateau depolarizations were observed in less than 10% of Purkinje cells unless K-conductances were blocked, and considerable membrane depolarization was often required to elicit Ca2+-dependent action potentials. These findings are compatible with the relative prominence of voltage-dependent outward currents in immature Purkinje cells, a property which may be enhanced in culture. The injection of hyperpolarizing current pulses revealed a marked time-dependent anomalous rectification in all Purkinje cells. At the breaks of such pulses, several events were observed. In all cells, a rebound conductance was identified which could generate post-anodal spike bursts. In cultured neurons, however, hyperpolarizing pulses were also followed by a slow return to resting potential. This membrane potential profile was similar to that produced by the activation of an A conductance. Experiments on acute slices from animals of different ages (P9-P17) showed that this A-like conductance was expressed only during a brief period in Purkinje cell development. A higher level of spontaneous synaptic activity was observed in cultured than in acute slice preparations. Both unitary excitatory postsynaptic potentials and inhibitory postsynaptic potentials could be elicited in the former by parallel fiber stimulation, and could be fully reversed by outward or inward transmembrane current injections, respectively.(ABSTRACT TRUNCATED AT 400 WORDS)

Aging↗

PubMed1988

Cytology and organization of rat cerebellar organ cultures.

Roller tube cultures of parasagittal cerebellar slices were taken from young rats aged 9-11 days, and maintained in vitro for 1-2 weeks. Morphological aspects of cell types and synaptic relationships in such organ cultures were examined at light and electron microscopic levels. Some neurons were marked by intracellular injections of horseradish peroxidase for subsequent identification of their connection patterns. Cytoarchitecture of the cerebellar cortex was largely preserved in the organ cultures. Dendritic trees of Purkinje cells exhibited isoplanar organizations that often resembled their orientation at the time of explanation. Other cerebellar neurons, namely granule cells, Golgi cells, basket cells, stellate cells, all differentiated within the organ cultures. In addition, some neurons of the deep cerebellar nuclei remained viable during the period of culture. Mossy fibers most probably of cerebellar nuclear origin were found terminating on the dendrites of granule cells and Golgi cells. Quite unexpected were certain types of direct synapses of afferent fibers on short necked spines arising from Purkinje cell smooth dendrites and somata. Such terminals resembled climbing fibers. They were most likely modified mossy fiber afferents, since the organ cultures did not include neurons of the inferior olive which are well spearated from the cerebellar mass at postnatal stages. These "ascending" mossy fibers presumably occupied postsynaptic surfaces that were either vacated by deafferentation or induced by the afferent fibers themselves. Intracellularly labeled Purkinje cells had widely distributed axonal collateral branches. Labeled axons were distributed within the Purkinje cell layer. Several recurrent Purkinje cell axon collaterals stained with reaction products of horseradish peroxidase tracer were followed at the ultrastructural level. In one case, labeled terminals were examined in an area of approximately 2 mm2. Terminals of Purkinje cell collaterals formed symmetric synapses with somata of basket cells and dendrites of Golgi cells, but not Purkinje cell somata. Some large boutons of serially traced Purkinje cell axon collaterals formed asymmetric contacts with profiles interpreted as Golgi cell dendrites. In contrast to the apparent axonal sprouting in cerebellar organ cultures, maturation of dendritic processes remained static. Astroglia cells of diverse shapes were observed following immunocytochemical staining with antisera to glia filament proteins. The distribution patterns of immunoreactive astrocytes changed dramatically in cerebellar slice cultures maintained for 3-6 weeks in vitro.

Animals↗

PubMed1988

Renal stone presenting as an abdominal lump.

We report a case of bilateral ureteropelvic junction obstruction associated with bilateral stones, one of which was large. An Anderson-Hynes operation was performed on both sides, the stones were removed and the patient became asymptomatic. To our knowledge the stone in our case is the largest and heaviest ever to be described in the literature.

Abdomen↗

PubMed1988

Type VIII collagen has a restricted distribution in specialized extracellular matrices.

A pepsin-resistant triple helical domain (chain 50,000 Mr) of type VIII collagen was isolated from bovine corneal Descemet's membrane and used as an immunogen for the production of mAbs. An antibody was selected for biochemical and tissue immunofluorescence studies which reacted both with Descemet's membrane and with type VIII collagen 50,000-Mr polypeptides by competition ELISA and immunoblotting. This antibody exhibited no crossreactivity with collagen types I-VI by competition ELISA. The mAb specifically precipitated a high molecular mass component of type VIII collagen (EC2, of chain 125,000 Mr) from the culture medium of subconfluent bovine corneal endothelial cells metabolically labeled for 24 h. In contrast, confluent cells in the presence of FCS and isotope for 7 d secreted a collagenous component of chain 60,000 Mr that did not react with the anti-type VIII collagen IgG. Type VIII collagen therefore appears to be synthesized as a discontinuous triple helical molecule with a predominant chain 125,000 Mr by subconfluent, proliferating cells in culture. Immunofluorescence studies with the mAb showed that type VIII collagen was deposited as fibrils in the extracellular matrix of corneal endothelial cells. In the fetal calf, type VIII collagen was absent from basement membranes and was found in a limited number of tissues. In addition to the linear staining pattern observed in the Descemet's membrane, type VIII collagen was found in highly fibrillar arrays in the ocular sclera, in the meninges surrounding brain, spinal cord, and optic nerve, and in periosteum and perichondrium. Fine fibrils were evident in the white matter of spinal cord, whereas a more generalized staining was apparent in the matrices of cartilage and bone. Despite attempts to unmask the epitope, type VIII collagen was not found in aorta, kidney, lung, liver, skin, and ligament. We conclude that this unusual collagen is a component of certain specialized extracellular matrices, several of which are derived from the neural crest.

Animals↗

PubMed1988

Hyponatraemia and mental symptoms following vesical ultrasonic lithotripsy.

A patient became confused and restless after vesical ultrasonic lithotripsy performed with distilled water as the irrigant. Serum sodium decreased to 120 mmol/litre from the pre-operative value of 138 mmol/litre. A cystogram revealed intraperitoneal extravasation of contrast. She recovered promptly after intravenous infusion of normal saline and emergency surgery for repair of the damaged bladder wall. This case illustrates that hyponatraemia and mental symptoms similar to those following transurethral resection syndrome also occur with ultrasonic lithotripsy when distilled water is used as the irrigant.

Extravasation of Diagnostic and Therapeutic Materi↗

PubMed1988