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Biomedical subjects

D Bose

Publications and source records attributed to D Bose.

90 records · Page 5Linked to original sources
PubMed1975

Utilization of calcium pools during pharmaco or electromechanical coupling in smooth muscle.

Isometric contraction of cat spleen capsule due to noradrenaline had a fast and a slow phase. These phases were due to a tightly and a loosely bound (or extracellular) pool of calcium, respectively. Depolarization due to high potassium caused mainly a reduction of the slow phase. In sodium-loaded spleen strips recovering from potassium deprivation, the sodium pump is electrogenic and the muscle cells are probably hyperpolarized. In this situation also the slow phase of noradrenaline response is reduced. It is concluded that both depolarization and hyperpolarization affect the utilization of loosely bound calcium and that tightly bound calcium may be released during 'pharmacomechanical coupling' in splenic smooth muscle.

Animals↗
PubMed1975

Mechanics of guinea pig taenia coli smooth muscle during anoxia and rigor.

Potassium-contracted guinea pig taenia coli relaxed when exposed to hypoxic glucose-free conditions, and this was followed by a second contraction. During this second contraction, which was not inhibited by ethylene glycol-his-(beta-aminoethylether)-N,N'-tetracetic acid (EGTA) the muscle was in rigor. After development of this contraction the muscle did not have an active state and was less extensible than a muscle normally contracted with KCl. Tension during rigor in an isometrically contracting muscle was short-lived in contrast to shortening during rigor development in a lightly loaded isotonically contracting muscle. These findings, together with the observation of irreversible lengthening of a muscle in rigor on stretching, suggest that rigor linkages can be broken. Glucose removal under aerobic conditions did not produce rigor, but oxygen removal in the presence of glucose resulted in relaxation followed by secondary contraction. This later contraction, unlike that accompanying rigor, was reversed by removal of calcium with EGTA. These data imply that in the absence of oxygen the removal of cytoplasmic free-Ca2+ is inhibited.

Animals↗
PubMed1975

Reversibility of mechanical and biochemical changes in smooth muscle due to anoxia and substrate depletion.

The effect of temporary glucose and oxygen deprivation on isometric tension as well as content of glycogen, creatine phosphate (CP), adenosine triphosphate (ATP), adenosine diphosphate (ADP), adenosine monophosphate (AMP), and adenylate pool (AP) were studied in potassium-contracted guinea pig isolated taenia coli. Under aerobic conditions glucose removal caused a decrease in tension, glycogen, CP, ATP, and energy charge; ADP and AMP increased, keeping the adenylate pool size unchanged. During rigor caused by additional anoxia, there was an increase in tension associated with further decrease in ATP and marked reduction of adenylate pool. Restoration of oxygen supply caused only a small increase in ATP that, though sufficient for abolishing rigor, was insufficient to support potassium contraction. Restoration of both glucose and oxygen did not restore tension even though ATP stores were increased further. Elevation of extracellular calcium caused partial restoration of tension, suggesting that the defect was in calcium metabolism rather than energy metabolism. During recovery AP remained low, possibly due to deamination of AMP. Anoxia in the presence of glucose reduced ATP to a concentration similar to that due to aerobic glucose deprivation but tension decreased much less. This result is consistent with different degrees of ATP depletion in various functional (Ca pump vs. contractile mechanism) compartments.

Adenosine Diphosphate↗
PubMed1973

The role of sodium pump in the inhibition of smooth muscle responsiveness to agonists during potassium restoration.

1. Isometric contractions of cat splenic capsular smooth muscle in response to noradrenaline and histamine were recorded.2. Removal of potassium from the bathing medium did not change the resting tension or the responsiveness to noradrenaline. Restoration of potassium inhibited responses to noradrenaline or histamine only if the muscles were stimulated with an agonist while in the K-free medium.3. This inhibition of responses to the agonists due to potassium was reversed rapidly by removing the ion or reversed slowly by prolonged exposure to the ion. The inhibition was also blocked by procedures or agents which block the sodium pump (ouabain, substitution of NaCl by LiCl), inhibit active processes (low ambient temperature) or prevent intracellular accumulation of sodium (substitution of choline for sodium).4. It is proposed that under special circumstances such as when there is an increase in internal sodium concentration, the sodium pump is probably electrogenic and causes relaxation when activated by external potassium. In the normal muscle the pump is probably electrically neutral.

Animals↗
PubMed1972

Influence of sodium pumping on smooth muscle contraction.

Isolated capsular muscle from cat spleen did not contract on exposure to a potassium-free bathing fluid. After exposure to conditions favouring downhill sodium and potassium movement (i.e. stimulation by noradrenaline in the absence of external potassium), subsequent reactivation of the sodium pump inhibited responses to noradrenaline. Under these special conditions, but not normally, the sodium pump may be behaving in an electrogenic manner.

Animals↗
PubMedDate not supplied

Effects of prazosin and phenoxybenzamine on alpha- and beta-receptor-mediated responses in intestinal resistance and capacitance vessels.

Previous studies have suggested that prazosin is a selective post-synaptic alpha-receptor blocker. It has also been suggested that it may have greater blocking actions on arterioles than on venous beds. These aspects have been investigated in cats anesthetized with pentobarbital. Prazosin had no effect on conductance in the acutely denervated hindlimb bed but caused a slowly developing vasoconstriction in the acutely denervated intestinal bed. The vasoconstrictor responses to sympathetic nerve stimulation were reduced to a similar extent in both vascular beds. Since maximal doses of prazosin produce only partial block of the alpha-receptor responses, there may be more than one type of postsynaptic alpha-receptor, and it is suggested that the postsynaptic receptors are of both alpha 1- and alpha 2-types. In the intestinal bed, prazosin produced similar reductions in both resistance and capacitance responses to sympathetic nerve stimulation. In isolated guinea pig aorta and portal vein, prazosin blocked the responses to noradrenaline competitively, and the pA3 values for the aorta and portal vein were similar. Thus, no selectivity for resistance vessels compared to capacitance vessels could be demonstrated in the intestine, and this result is compared to our previous observations in the liver. Although prazosin only reduced the vasoconstrictor responses to sympathetic nerve stimulation in the intestine, phenoxybenzamine reversed the response to a beta-receptor-mediated vasodilatation, as reported some years ago. These observations support our earlier hypothesis that nerve stimulation does not normally activate beta-receptors, but after phenoxybenzamine, the increased release of noradrenaline combined with alpha-receptor blockade results in a beta-receptor-mediated vasodilatation in the intestinal bed.

Animals↗
PubMedDate not supplied

Madhusudan Gupta.

Madhusudan Gupta (1800-1856) hailed from a high family. He joined the newly created Ayurvedic classes in Sanskrit College, Calcutta in 1926 [1826] and was promoted to the post of a teacher in the same medical college in view of his great interest and enthusiasm. He was the first man who dissected cadaver in 1936 [1836] and created a sensation in the orthodox Hindu Society. Madhusudan made a consistent effort for the improvement of medical science in India. A summary of the salient features of Madhusudan and his activities is presented in this paper with extracts of original passages appearing in reports of different committees and works.

History, 19th Century↗