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Biomedical subjects

S Wadhwa

Publications and source records attributed to S Wadhwa.

At least 19 recordsLinked to original sources
PubMed1999

Developmental expression of calretinin immunoreactivity in the human retina and a comparison with two other EF-hand calcium binding proteins.

This paper reports the localization pattern of calretinin, a calcium-binding protein, in the human retina during development, as studied by immunohistochemistry. A comparison is made of the cellular distribution of calretinin with two other calcium-binding proteins, calbindin and parvalbumin, recently reported by us in the human retina, and by parallel labeling with both antisera in the same tissues. At 11-12 weeks of gestation, calretinin immunoreactivity was expressed in many prospective ganglion cells of the central inner neuroblastic zone. At 16-17 weeks of gestation, the immunoreactivity was localized in the ganglion cell layer, inner plexiform layer, and in most differentiated amacrine, horizontal and cone cells located in the central (1-2 mm temporal from optic disc) to midperipheral parts of the retina. By midgestation (20-21 weeks), calretinin immunoreactivity was strongly developed in the cone photoreceptors. Parallel labeling with calbindin and parvalbumin antisera revealed that the calretinin-positive horizontal cells were somewhat smaller and less frequent and less intense than the calbindin- and parvalbumin-positive counterparts, at 16-21 weeks of gestation. No horizontal cells were calretinin immunopositive in the postnatal (four-month-old infant) and adult retinas examined. Also, at both stages, a few bipolar and cone cells were weakly immunoreactive. These observations suggest a critical role for calretinin in the development and maturation of a select class of horizontal cells. The widespread expression of immunoreactivity in the early ganglion cells indicates that calretinin may be involved in their differentiation. The weak immunoreactivity pattern noted in the adult photoreceptor and bipolar cells, and an apparent lack of immunoreactivity in the mature horizontal cells, tends to indicate that, unlike calbindin and parvalbumin, calretinin plays little role in the transport and physiological buffering of Ca2+ in these neurons of the human retina. It appears, however, that calretinin is predominantly involved in both processes in amacrine cells.

Calbindin 2↗
PubMed1998

The expression of nitric oxide synthases in human brain tumours and peritumoral areas.

Nitric oxide, a potent signalling molecule produced from L-arginine by nitric oxide synthase (NOS), has been implicated in diverse pathophysiological processes. Many characteristics of malignant tumours such as increased vascular permeability, vasodilation, neovascularisation and free radical injury to the tumour and adjacent normal tissues are believed to be mediated by nitric oxide. While NOS expression has been demonstrated in brain tumours, no equivalent studies have yet been reported on the adjacent peritumoral brain region. The present study examined the pattern of NOS expression in the human tumour and peritumoral brain areas. Biopsies were obtained from eight patients (six gliomas, one each of meningioma and metastatic adenocarcinoma) from three areas: tumour, peritumoral, and apparently 'normal' adjacent brain tissue. Immunohistochemical staining was performed for three isoforms of NOS: brain NOS (BNOS), endothelial NOS (ENOS) and macrophage-specific NOS (MacNOS). Except for glioblastoma multiforme and metastatic adenocarcinoma, the tumour cells expressed all three NOS isoforms. In four tumours, there was a demonstrable gradient of ENOS expression falling away from the tumour. In three gliomas, many glial cells were intensely labelled with BNOS. This labelling decreased in the peritumoral tissues. In four tumours, cells (presumably lymphocytes, and CD 45 positive macrophages) were labelled intensely with MacNOS in and around the blood vessels. These results suggest that nitric oxide is produced in the tumour cells and endothelium of tumour vasculature, while occasionally glial cells may also be induced to produce it. The possible role of nitric oxide in the production of peritumoral oedema is discussed.

Adenocarcinoma↗
PubMed1998

Photoreceptor morphogenesis in the human retina: a scanning electron microscopic study.

There are a number of scanning electron microscopic (SEM) studies on retinal photoreceptors of vertebrates. However, most of these are concerned with the adult retina, and only a very few deal with developing photoreceptors. In man, SEM studies have not been carried out on photoreceptor morphogenesis during fetal or postnatal stages. Hence, the present study was undertaken to examine the sequential morphological changes in developing photoreceptors during different gestational ages in the human retina. Retinas of human fetuses of gestational ages of 10-25 weeks and from autopsy of a 5-month-old infant were processed for SEM. The observations show some new information on the morphogenesis of photoreceptors. At 10-11 weeks, the outer and inner neuroblastic zones are well developed and separated from each other by the layer of Chievitz. By 15-16 weeks, the photoreceptor precursors appear as spherical inner segments on the scleral surface of the outer neuroblastic zone. Cilia develop as small protrusions from the apical ends of the inner segments. Photoreceptor inner segments become arranged in mosaic pattern by 18-19 weeks. In the mosaic, large cone inner segments (putative blue cones) stand out prominently from the remaining small cone inner segments (prospective red/green cones). The rod inner segments are identifiable and show cilia. Between 19-20 and 24-25 weeks, the cone inner segments elongate and change in shape from spherical to oval. At 24-25 weeks, the outer segments develop from the distal ends of rod cilia. At this period, the inner segments of rods and cones are interconnected by protoplasmic projections. Although the precursors of both rods and cones appear to be in a similar state of development at 14-15 weeks gestation, the rods undergo morphological maturation earlier than do the cones. Photoreceptor development in the anterior retina lags behind that of the posterior retina by about 10 weeks. At 5 months after birth, the posterior retina possesses fully developed photoreceptors that are comparable to those of the adult. However, the photoreceptors in the ora serrata resemble those in the posterior retina of 24-25 weeks gestation.

Fetus↗
PubMed1998

Gastric pneumatosis associated with preduodenal portal vein, duodenal atresia, and asplenia.

An 8-day-old newborn presented with non-bilious vomiting, upper abdominal fullness, and failure to pass meconium. Plain radiographs revealed gastric pneumatosis (GP). At operation, he was found to have a non-obstructive preduodenal portal vein, preampullary duodenal atresia, asplenia, and malrotation. The baby was treated by duodeno-duodenostomy without mobilizing the portal vein and correction of the malrotation according to Ladd's procedure. He made an uneventful recovery and the GP resolved spontaneously. The malformative process was believed to have occurred at or soon after the 5th week of gestation, and the GP probably resulted from intramural air tracking through mucosal tears caused by high intragastric pressure.

Cysts↗
PubMed1998

Immunohistochemical localization of taurine in the retina of developing and adult human and adult monkey.

The localization of taurine in the retina of fetal (12-25 weeks of gestation), postnatal (five-month-old infant) and adult human (35- and 65-year-old) was examined by immunohistochemistry. Additionally, retinas of fresh adult monkey, which served as positive controls, were employed. No immunoreactivity was found in the fetal retinas from 12-15 weeks of gestation. At 1617 weeks of gestation, the ganglion cells and some of their axons were conspicuously labelled for taurine. At 18-19 weeks, Muller glial endfeet, the inner plexiform layer, some amacrine and putative horizontal cells and photoreceptors showed moderate immunoreactivity. With further development at 20-21 and 24-25 weeks of gestation, the immunoreactivity was prominent in Muller cell endfeet, some bipolar cells and in horizontal cells that were aligned in a row in the inner nuclear layer, close to the fovea. At both fetal stages, the photoreceptors and horizontal cells showed strong immunoreactivity. In the postnatal infant retina, taurine immunoreactivity was present in some amacrine cells and photoreceptor inner segments and nuclei, but not in ganglion and horizontal cells, which was also the pattern noted in the adult monkey and human retinas. With development, a shift in the intensity of taurine immunoreactivity was noted towards the outer retina. The expression of taurine immunoreactivity in most fetal retinal neurons implies a role for this amino acid in the normal development as well as maturation of human retina.

Adult↗
PubMed1996

Calbindin and parvalbumin immunoreactivity in the developing and adult human retina.

We report the expression and pattern of two calcium-binding proteins (CBPs), calbindin (CALB) and parvalbumin (PV), in the fetal (13-25 weeks of gestation), postnatal (5 months) and adult human retina, as studied by immunohistochemistry. Both CBPs appear prenatally in different neurones as well as in the nerve fibre, inner and outer plexiform layers. The cones do not show immunoreactivity for both CBPs up to 25 weeks, the last fetal stage studied; however, they are immunopositive in the postnatal and adult retina. Of the two CBPs, CALB appears first, followed by PV. The immunoreactivity for both CALB and PV in the fetal retina follows a centroperipheral gradient and vitreal to scleral pattern of retinal differentiation. The CALB immunoreactivity shows a gradual increase in intensity with age. A spurt in intensity of PV immunoreactivity in the 24-25 week fetal retina and increased intensity in the 60 year normal adult retina when compared to the light-deprived retina of a 34-year-old staphyloma patient suggests an activity-dependent functional role for PV.

Adult↗
PubMed1994

Immunohistochemical localization of tyrosine hydroxylase, substance P, neuropeptide-Y and leucine-enkephalin in developing human retinal amacrine cells.

Prenatal changes in the neurotransmitter/neuromodulator profiles of tyrosine hydroxylase (for dopamine), substance P, neuropeptide Y, and leucine-enkephalin were studied in developing human retinal amacrine cells by the use of immunohistochemical techniques. Tyrosine hydroxylase was localized between 10 and 12 weeks of gestation, substance P and neuropeptide Y appeared little later around 14 weeks, and leucine-enkephalin-like immunoreactivity was observed at 16 weeks.

Enkephalin, Leucine↗
PubMed1994

Development of human lateral geniculate nucleus: an electron microscopic study.

A qualitative and quantitative ultrastructural study has been carried out on lateral geniculate nuclei (LGN) of 21 human fetuses ranging in gestational age from 13-14 to 34-35 weeks. At the early age period of 13-15 weeks, LGN is characterized by immature cells with indented nuclei possessing multiple nucleoli and by a sparse neuropil. During the subsequent age periods studied progressive maturational changes lead to neurons having round nuclei with a single nucleolus and well-developed cytoplasmic organelles as well as to an elaborate neuropil. Synaptic contacts which are seen for the first time at the age of 13-14 weeks are of retinogeniculate type. They show features of immature synapses and are located mainly on the juxtasomatic parts of dendrites. With increasing gestational age, the synapses increase in size, maturity, types and complexity; an acquisition of complex synaptic arrangement (triad) occurs by 20-21 weeks. Excitatory synapses appear earlier than do the inhibitory ones. Formation of retinogeniculate contacts precedes that of the corticogeniculate type. The synaptic density and total synapse number show a progressive increase with increasing gestational age. The age period of 15-20 weeks of gestation is marked by presence of organelles suggestive of a high rate of metabolic activity, significant increase in synaptogenesis, presence of transient contacts on soma and large number of free postsynaptic membrane densities (PSD). The period thereby represents a critical period in the development of synapses in LGN. The numerical values obtained by by the age of 34-35 weeks are still low as compared to the values reported for other areas of brain.

Adult↗