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Biomedical subjects

S C Sharma

Publications and source records attributed to S C Sharma.

At least 217 records · Page 12Linked to original sources
PubMed1986

The visual system of the channel catfish (Ictalurus punctatus). I. Retinal ganglion cell morphology.

Horseradish peroxidase was applied to lesions in the optic nerve of catfish (Ictalurus punctatus). The retinae were processed to reveal HRP-labelled ganglion cells. The histochemical techniques employed allowed fine details of the dendritic arbor to be resolved. Flat-mounted retinae were examined and the following characteristics were noted in individual ganglion cells: Soma area, shape, and depth; number and diameter of major dendrites; shape, area, and depth(s) within the inner plexiform layer (ipl) of the dendritic arbor; origin of the axon (from the soma or a dendrite). On the basis of these characteristics, eleven classes of ganglion cells were delineated: four classes of giant cells (G1-G4) and seven classes of smaller cells (S1-S7). G1 cells had dendrites arborizing in the most distal sublamina of the ipl. G1 cells in the dorsal retina had nasotemporally elongated dendritic arbors. G2 cells had dendrites in the proximal portion of the ipl. G3 cells were almost completely confined to a band running between the nasal and temporal retinal poles, through the center of the retina. In this location, the cells had dorsoventrally elongated dendritic arbors, which were bistratified in the ipl. G4 cells were displaced into the inner nuclear layer. S1 and S4 cells had axons arising from their somata, and dendrites arborizing in the distal and the proximal ipl, respectively. S2 cells were typified by their unstratified dendritic arbors. Similarly, S3 cells were characterised by their bistratified arbors. S5 cells arborized in the most proximal ipl sublamina. S6 cells were small ganglion cells with their somata lying in the inner nuclear layer. S7 cells tended to have complex dendritic arbors, and their axons arose from dendrites.

Animals↗
PubMed1986

Bilateral projections of neurons in the lateral geniculate nucleus and nucleus lateralis posterior to the visual cortex in the neonatal rat.

The projection from the lateral geniculate nucleus (LGN) and nucleus lateralis posterior (LP) to the visual cortex was examined in rat pups 3-7 days of age using the fluorescent tracers True Blue, Fast Blue and Nuclear Yellow. Our data provide the first evidence that (1) these projections are bilateral, (2) the ipsilateral projection from these nuclei to the visual cortex in the neonatal rat is well localized and is similar in distribution and organization to that reported by others in the adult and (3) bilaterally projecting geniculocortical cells are morphologically heterogeneous; bilaterally projecting cells in LP are morphologically homogeneous.

Animals↗
PubMed1986

Malignant lymphoma of convoluted lymphocytes: diagnosis by fine-needle aspiration cytology and cytochemistry.

The technique of fine-needle aspiration cytology (FNAC) was utilized in the diagnosis of 31 cases of malignant lymphoma of convoluted lymphocytes. The age of the patients ranged from 5 to 70 yr (median, 24 yr). Clinical history was available in 29 cases. All patients had peripheral lymphadenopathy. There was radiological evidence of mediastinal adenopathy in 62% of the cases, and 41% had pleural effusion; 52% of the patients presented with mediastinal compression syndrome. The diagnostically crucial convoluted cells comprised 47.3 +/- 23.73% of all lymphoid cells. Nuclear convolutions were appreciated in a significant number of cells in paraffin sections of 17 of 21 cases (85.7%) having subsequent histopathology. Cytochemical and E-rosette tests performed in 17 cases confirmed the T cell nature of the neoplasms. On an average, 72.3% of cells showed focal positive reaction for acid phosphatase, and 73.8% of cells formed E-rosettes.

Adolescent↗
PubMed1986

Retinal topography in the optic tract of adult goldfish.

The present study was aimed at determining how transformations in fiber order establish a retinal topography in the optic tract of adult Carassius auratus. Horseradish peroxidase was applied to the optic nerve or retina, and the pathways of labeled axons originating from retinal annuli or wedges were analysed in reconstructed serial-sections and wholeamounts of the optic pathway. The age-related fiber order of the optic tract involves a rotation of the optic pathway that begins near the chiasm, continues through the optic tract as it wraps around the brain, and extends through the brachia. The relative order of laminae, in which each lamina is composed of age-related axons, is maintained in the optic pathway. The laminae add systematically onto the optic tract in a mediolateral direction with the oldest lamina forming the medial margin. Retinal sector order in the optic tract is established by the rearrangement of axons from each lamina. These rearrangements begin at the chiasm and, in part, involve transposition of axons originating from the ventrotemporal and dorsonasal sectors of the retina. The transformations achieve a fiber order in the optic tract that is appropriate for entry into the tectum. It is proposed that the final retinal topography of the optic tract is determined by the combined influences of selective affinities along the neural axis and substrate guidance mechanisms, the latter being mediated largely by the oldest axons of the fasciculus medialis tractus opticus.

Animals↗
PubMed1986

An intracavitary cone system for electron beam therapy using a Therac 20 linear accelerator.

The Therac 20 is an AECL medical linear accelerator that produces electron and photon beams. Electron fields are produced by a scanned beam; collimation is provided by two sets of primary collimators and further collimated by external electron trimmers located 11 cm above the plane of isocenter (100 cm). These collimators are not suitable for intracavitary treatment. To overcome this limitation, we have designed an intracavitary cone system that attaches to the electron trimmers. Since the trimmers do not have to be removed while this system is in use, there is no need to bypass the associated interlock system. The apparatus consists of a platform which slides onto the lower set of trimmers, onto which a lead insert is attached. Dosimetry measurements for 9, 13, and 17 MeV electron beams are reported for three different treatment cones.

Humans↗
PubMed1986

Hepatotoxicity of metals in glutathione-depleted mice.

Sublethal doses of cadmium chloride (CdCl2; 3 mg/kg i.v.), mercuric chloride (HgCl2; 2 mg/kg i.v.) and sodium vanadate (6 mg/kg i.v.) were administered to normal and glutathione (GSH)-depleted mice (phorone, 250 mg/kg i.p.). In normal mice serum sorbitol dehydrogenase (SDH) activity as a measure of hepatotoxicity was elevated 24 h after treatment with CdCl2 and HgCl2. Following GSH depletion more pronounced increments of SDH activities were observed only after CdCl2 treatment. No difference was seen in the exhalation of ethane by normal and GSH-depleted animals, neither in metal-treated nor in control mice, indicating that lipid peroxidation is not involved in their hepatotoxicity.

Animals↗
PubMed1986

The holoacardius: a correlative computerized tomographic, radiologic, and ultrasonographic investigation of a new case with review of literature.

A holoacardius from a monozygotic, monochorionic twin pregnancy of 36 weeks is described. Trisomy-18 was diagnosed in the viable female cotwin. Computerized tomographic, radiologic, and ultrasonographic procedures were applied to the acardiac. Its three-vessel umbilical cord was velamentously attached to the single placenta. Grossly malformed and poorly developed craniofacial structures, absence of neck and upper extremities, sirenomelic lower extremity, absence of heart, and development of only a few skeletal elements were prominent features. A review of selected world literature emphasizes the limits of the estimates dealing with the total number of reported cases and the incidence of acardii.

Abnormalities, Multiple↗
PubMed1986

Phenylbutazone and oxyphenbutazone distribution into tissue fluids in the horse.

The clinically recommended dose rate of phenylbutazone (4.4 mg/kg) was administered intravenously as a single dose to five Welsh Mountain ponies. Distribution of phenylbutazone and its active metabolite oxyphenbutazone into body fluids was studied by measuring concentrations in plasma, tissue-cage fluid, peritoneal fluid and acute inflammatory exudate harvested from a polyester sponge model of inflammation. The ready penetration of phenylbutazone into inflammatory exudate was demonstrated by the relatively high mean value for Cmax of 12.4 micrograms/ml occurring at a time of 4.6 h and a mean AUC0-24 of 128 microgram X h/ml. A high mean exudate:plasma AUC0-24 ratio of 0.83 was recorded. Plasma:exudate concentration ratios for phenylbutazone were initially greater than and subsequently less than one; the slower clearance from exudate was indicated by approximate t1/2 beta) values of 4.8 and 24 h for plasma and exudate, respectively. These findings may help to explain the relatively long duration of action of phenylbutazone, in spite of a plasma elimination half-life of less than 5 h. Lower values of Cmax and AUC0-24 for phenylbutazone passage into peritoneal fluid (6.3 micrograms/ml and 45 micrograms X h/ml) were recorded, and a limited number of sampling times indicated a similar degree of penetration as into tissue cage fluid. Mean concentrations of oxyphenbutazone in all fluids were lower than phenylbutazone concentrations at all times, but ready penetration of the metabolite into body fluids, especially into inflammatory exudate, occurred suggesting that oxyphenbutazone may contribute to the anti-inflammatory effect. The hyperaemia of acute inflammation and the high protein levels in inflammatory exudate may both assist passage of phenylbutazone and oxyphenbutazone into exudate.

Animals↗
PubMed1986

Glutathione depletion by phorone organ specificity and effect on hepatic microsomal mixed-function oxidase system.

Phorone (diisopropylidene acetone) led to a strong depletion of cellular glutathione in liver, kidney and heart but not in lung or brain upon administration to mice or rats. Its efficacy in lowering hepatic glutathione levels was comparable to that of diethylmaleate. Unlike this agent, however, phorone did not affect the microsomal mixed-function oxidase system at all. Our findings favor the use of phorone when studying the effect of a decreased glutathione content on detoxication, bioactivation or drug metabolism mechanisms, as it merely interacts with glutathione itself.

Animals↗
PubMed1986

Comparison of blood levels of vitamin A, beta-carotene and vitamin E in abruptio placentae with normal pregnancy.

Levels of vitamin A, beta-carotene and vitamin E in peripheral venous blood of women in abruptio placentae and in normal pregnancy have been compared. Chemical methods were used for the estimation of these compounds. The results show that levels of all three compounds in abruptio placentae are lower than those found in the normal pregnancy. We have earlier shown that levels of ascorbic acid in these subjects are low while other studies have indicated that levels of folic acid in them are also low. Based on our present and earlier published work it is suggested that abruptio placentae is a condition with multiple vitamin deficiency. Whether this is its cause or effect is however not clear.

Abruptio Placentae↗
PubMed1985

Role of calcium in the histamine release induced by D-galactosamine from rat mast cells.

Rat peritoneal mast cells were isolated and purified by differential centrifugation in Ficoll. Cells pooled from three to four rats were suspended at approximately 10(6) cells/ml in a buffered salt solution and incubated for 1 h at 37 degrees C in 300 microliter volumes in the absence or presence (9 X 10(-4) M) of calcium chloride. Addition of D-galactosamine hydrochloride (DGM; 2.8 X 10(-4)M) caused (in addition to basal release) a mean +/- SEM percent histamine release of 15.7 +/- 5.2 in the presence of Ca++ and 19 +/- 4.9 in the absence of Ca++ (p greater than 0.05). It is suggested that D-galactosamine does not require extracellular Ca++ for the release of histamine from the rat mast cell.

Animals↗
PubMed1985

A note on a tectal neuron projecting via the tectobulbar tract in teleosts.

Catfish and goldfish received small, unilateral tectal injections of horseradish peroxidase. In these fish a population of large diameter tectal efferent axons could be seen travelling to the hindbrain. Each of these axons gave up to 19 collateral branches. These branches arborized in or near the dendritic fields of the ipsilateral nucleus lobobulbaris and oculomotor nucleus, and the contralateral trigeminal nucleus, oculomotor nucleus, abducens nucleus, nucleus lateralis valvulae and medial reticular formation. The results suggest that these axons are involved in triggering eye movements.

Animals↗
PubMed1985

Retinal origin of the fasciculus medialis tractus optici in adult goldfish.

In teleosts, the fasciculus medialis tractus optici departs the optic tract and follows an aberrant path towards the midbrain tectum. To determine the retinal origin of the fascicle, horseradish peroxidase was injected into localized lesions of either the optic nerve or the retina. The fasciculus medialis axons of adult goldfish derive selectively from ganglion cells residing in the dorsotemporal portion of the central retina. The fasciculus medialis appears to be an integral part of the chronotopic ordering of fibers in the optic tract.

Animals↗
PubMed1985

Selective retinal reinnervation of a surgically created tectal island in goldfish. I. Light microscopic analysis.

Through anatomical and physiological studies of the regenerating retinotectal projection of goldfish, we sought to determine whether the establishment of a topographic projection is attained through a refinement of an initially less precise pattern of innervation. A 1-mm-wide mediolateral strip of caudal tectum was removed so that a small island of tectal tissue was spared at the caudal pole, and the contralateral nerve was either crushed (TIX) or left intact (TI). The presence of regenerated axons in the ablated zone and the reinnervation of the caudal island were assessed with anterograde and retrograde labeling methods in the following postoperative intervals: early, 20-50 days; middle, 50-110 days; and late, more than 170 days. The anterograde radioautographic method revealed that the appropriate layers of the tectal island became reinnervated by optic axons during the early period. During the middle and late periods, one to several large, discrete bundles bridging the lesion zone along the surface of exposed subtectal structures were readily identified both by radioautography and by anterograde or retrograde labeling following application of horseradish peroxidase to the transected optic nerve or tectal island, respectively. In contrast, the anterograde horseradish peroxidase method did not reveal axon bundles extending caudal to the half-tectum in the absence of a tectal island. Among TIX cases, retrograde horseradish peroxidase labeling of the contralateral nasal retina was more widespread in the middle period than in the late period, a result we interpret as reflecting an improvement in topographical precision with time. The area of retinal labeling among TIX cases in the late period was similar to that following caudal tectal injection in cases with simple nerve crush, although it was still elevated above normal control values. Physiological maps indicated a focal representation of the nasal retina in the tectal island in both periods and did not reveal a transient extreme convergence of retinal input. These findings are discussed in relation to Sperry's chemoaffinity theory.

Animals↗