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Biomedical subjects

P D Gupta

Publications and source records attributed to P D Gupta.

At least 73 records · Page 4Linked to original sources
PubMed1985

Cell to cell association in Zajdela ascitic hepatoma. An ultrastructural study.

Zajdela ascitic hepatoma cells exist as small islands of two or more cells in addition to single cells. It is now shown that the number of cells per island is directly proportional to the age of the tumor. The number of single cells is maximal 24 h after transplantation of the tumor. Various types of inter-cellular connections are seen between adjacent cells in the island. These junctions are predominant in the apical regions of the cells. The electron-dense material present at junctional sites disappears from several sites after treatment of the islands with chelating agents such as EDTA, EGTA and citrate; the latter being most effective. No appreciable effect on the removal of electron-dense material from the junctional sites is observed when the islands are treated with either collagenase or trypsin.

Animals↗
PubMed1981

Carotid chemoreceptors and vagi in hypoxic and cyanide-induced tachycardia in the dog.

We investigated the mechanisms underlying heart rate changes resulting from systemic hypoxia in anesthetized artificially ventilated dogs with low control heart rate (less than or equal to 93 beats/min). We observed that systemic hypoxia evoked tachycardia in intact dogs that was not significantly different from that evoked in dogs with beta-adrenergic blockade (BB). Also, tachycardia elicited in dogs with BB plus spinal section at C3 (BBSS) was significantly greater than in dogs with BBSS plus bilateral section of carotid sinus nerves. Furthermore, under various anesthetics, intracarotid injection of sodium cyanide induced a tachycardia response in dogs with low control heart rate (less than or equal to 97 beats/min) and a bradycardia response in dogs with high control heart rate (greater than or equal to 130 beats/min). These results suggest that 1) when the resting cardiac parasympathetic tone is high, systemic hypoxia evokes tachycardia which is mediated predominantly through efferent vagus nerves and 2) the stimulation of carotid chemoreceptors causes excitation of both cardioacceleratory and cardioinhibitory reflexes, the resultant response being dependent on the prevalent autonomic drive.

Animals↗
PubMed1980

Resistance of human syncytiotrophoblast to hypotonic and thermal stress.

Human placental syncytiotrophoblast was not lysed when exposed to acutely hypotonic environments (distilled water) or during repeated freeze-thawing. The ability of the syncytiotrophoblast to synthesize and secrete hCG was not blocked after exposure to hypotonic stress (0.055 osmol) and elevated temperature (47 degrees C), treatments which caused lysis of erythrocytes and lymphocytes. The stress-resistant property of the syncytiotrophoblast may be an important element in enabling its survival as a barrier between the maternal environment and the conceptus.

Chorionic Gonadotropin↗
PubMed1979

Neural mechanism underlying tachycardia induced by nonhypotensive a-v shunt.

The mechanism underlying tachycardia resulting from nonhypotensive arteriovenous shunt (shunt open plus infusion of blood to compensate for the fall in mean arterial pressure resulting from opening of a shunt) was investigated in anesthetized, artificially ventilated dogs. In dogs with intact autonomic innervation, dogs with beta-adrenergic blockage (BB), and dogs with BB plus spinal section at C7 (BBSS), opening of the shunt resulted in tachycardia (P less than 0.01 for all comparisons), which was, however, not significantly different on comparison among groups (P greater than 0.40 for all comparisons). This shows that afferent and efferent sympathetic-mediated reflexes do not play a significant role in this tachycardia response. Additionally, the tachycardia response was significant in dogs with BBSS plus right or left vagotomy, but it was completely abolished in dogs with BBSS plus bilateral vagotomy. This suggests that in dogs with blockade of sympathetic afferent and efferent pathways, tachycardia resulting from nonhypotensive arteriovenous shunt may be due to a cardioacceleratory reflex with its ascending and its descending pathways in each vagus nerve.

Animals↗
PubMed1978

Structural transformation and modulation of succinic dehydrogenase activity in the mitochondria of germinating seeds.

Ultrastructural transformation of mitochondria in the cotyledons of dry and germinating seeds of Vigna sinensis from the 'orthodox' to 'condensed' forms is coupled with an increasing rise in the specific activity of succinic dehydrogenase (SDH). Apparently, the transformation of mitochondria to the 'condensed' form associated with the utilization of substrate which is reflected in the rise in enzyme activity. During the process of germination, the mitochondria of the cotyledonary cells undergo three different phases namely, (1) activation phase, (2) preparatory phase, and (3) multiplication phase.

Mitochondria↗
PubMed1977

Autonomic afferents at T1 in elicitation of volume-induced tachycardia in the dog.

Intravenous infusion of blood elicited tachycardia in anesthetized dogs with beta-receptor blockade (dogs with vagal efferents intact but cardiac sympathetic efferents blocked) and bradycardia in dogs with combined beta-receptor blockade and rhizotomy at T1 (dogs with vagal efferents intact but cardiac sympathetic efferents plus autonomic afferents at T1 blocked). This suggests that tachycardia elicited by volume in infusion may be partly due to a reflex with its afferent pathway at the T1 segment of the spinal cord and its efferent pathway in the vagi. Moreover, infusion evoked bradycardia in dogs with right-sided rhizotomy at T1, which was not significantly different from the response elicited in dogs with bilateral rhizotomy at T1. Additionally, the tachycardia response induced in dogs with ventral or dorsal rhizotomy at T1 was significantly different from the bradycardia response elicited in dogs with both dorsal and ventral rhizotomy at T1. These results suggest that the afferent pathway predominates on the right side, and its entry at T1 may be via both dorsal and ventral roots.

Afferent Pathways↗
PubMed1976

Ontogenesis, distribution and relative sensitivity of hCG receptors to hCG and LH in goat ovaries.

The binding of [125I]hCG to immature and mature follicles and corpora lutea of goat ovaries has been studied. The hormone is bound maximally by corpora lutea although mature follicles also exhibit some binding. Immature follicles are practically devoid of receptors for this hormone. In the corpus luteum, the receptors for the hormone are present in thecal and luteal cells. Autoradiographic studies show the location of the bound radioactivity grains primarily along the plasma membranes of these cells, although some radioactivity grains were also seen in the cytoplasm of luteal but not thecal cells. On a mole to mole basis, hCG was found to displace [125I]hCG from binding to receptors on corpus luteum better than hLH and oLH.

Animals↗