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Biomedical subjects

C L Kapoor

Publications and source records attributed to C L Kapoor.

8 recordsLinked to original sources
PubMed1978

A possible role for guanosine 3',5'-monophosphate in the stimulus-secretion coupling in exocrine pancreas.

Carbamylcholine, caerulein and cholecystokinin octapeptide rapidly increased the cyclic GMP concentration and amylase secretion in isolated guinea pig pancreatic slices. The cyclic GMP concentration was increased eight-fold over the basal concentration in 30 s, with concomitant increase in the rate of amylase secretion. The tissue concentration of cyclic GMP then rapidly declined to a plateau value of approx. 16% of the peak level within 10 min and was maintained at that concentration for the duration of the experiment. We have shown earlier (Kapoor, CL. and Krishna, G. (1977) Science 196, 1003--1005) that the decrease of tissue cyclic GMP was due mainly to the secretion of cyclic GMP into the medium. The cyclic AMP concentration in the tissue was not changed, nor was it secreted into the medium. There was a correlation between the concentration response to various agents for the increase in cyclic GMP concentration and amylase secretion in pancreatic slices. Carbamylcholine increased both the cyclic GMP concentration and amylase secretion; the half-maximal effect was achieved at 1.5 micrometer concentration. Caerulein and cholecystokinin octapeptide were 5000 times more potent than carbamylcholine in increasing cyclic GMP concentration and amylase secretion; the half-maximal effect was achieved at 0.3 nM concentration. Atropine, which completely inhibited the increase in cyclic GMP and amylase secretion induced by carbamylcholine, did not block the effects of caerulein or cholecystokinin octapeptide. These results suggest that various secretagogues induced amylase secretion by increasing the cyclic GMP concentration, but the mechanism by which cyclic GMP caused amylase secretion remains to be elucidated.

Amylases↗
PubMed1978

Pineal serotonin N-acetyltransferase activity: abrupt decrease in adenosine 3',5'-monophosphate may be signal for "turnoff".

Dispersed pinealocytes have been used to study the role of adenosine 3',5'-monophosphate (cyclic AMP) in the "turnoff" of N-acetyltransferace activity. Activity was first stimulated 100-fold by treating cells with 1-norepinephrine. 1-Propranolol acted stereospecifically to rapidly reverse this, resulting in a 70 percent loss of enzyme activity within 15 minutes. An even more rapid 1-propranolol-induced decreased in cyclic AMP also occurred. This together with the observation that the inhibitory effect of 1-propranolol on N-acetyltransferase was blocked by dibutyryl cyclic AMP and phosphodiesterase inhibitors indicate that an abrupt decrease in cyclic AMP may be the signal for the rapid decrease in pineal N-acetyltransferase activity.

Acetyltransferases↗
PubMed1977

Hormone-induced cyclic guanosine monophosphate secretion from guinea pig pancreatic lobules.

Carbamylcholine (30 micronM) increased the concentration of guanosine 3',5'-monophosphate (cyclic GMP) in guinea pig pancreatic lobules about eight-to tenfold over the basal concentration in 30 seconds with a concomitant increase in the rate of amylase secretion. The concentration of cyclic GMP rapidly declined to a plateau value of about 16 percent of the peak level in 10 minutes. Cellular cyclic GMP decreased, mostly because the nucleotide was secreted into medium; cellular adenosine 3',5'-monophosphate (cyclic AMP), however did not change, nor was this nucleotide secreted into the medium. An immunocytochemical technique showed that cyclic GMP was distributed in the apical plasmalemma membrane and lumen of the pancreas. Carbamylcholine increased the cyclic GMP fluorescence in tha apical plasmalemma membrane within 30 seconds, and in zymogen granules and the plasma membrane in the apical part of acinar cells in 10 minutes. The islets of Langerhans did not show any change in cyclic GMP. Fluorescence of cyclic AMP in pancreatic lobules was not altered by carbamylcholine and was localized along the apical portion of plasmalemma and cytoplasm. Cyclic GMP may thus participate either in the process of exocytosis or in the activation of enzymes secreted from the pancreas.

Amylases↗
PubMed1975

Interaction of bilirubin with reconstituted collagen fibrils.

1. Interaction of bilirubin with collagen fibrils was explored in a two-phase system where collagen was present as an opaque rigid gel composed of striated fibrils, and bilirubin as an aqueous solution. 2. The Ka value of the binding of bilirubin to collagen fibrils is 5.4 X 10(3)M-1. The interaction of bilirubin with collagen fibrils depends on temperature. Below 5 degrees C, the binding is greatly diminished and denaturation of collagen fibril aggregates at 52--53 degrees C into a dissolution state abolishes binding of bilirubin. 3. Salicylate and sulphanilamide do not affect the binding of bilirubin to reconstituted collagen fibrils. 4. Serum albumin (40--80mM), known to reverse the binding of bilirubin to lipids, dissociates only 50% of the bilirubin bound to collagen fibrils. This suggests that sites located on collagen participate in some tight binding of bilirubin and the corresponding binding sites on albumin do not compete with them. 5. Urea (4M) abolishes more than 70% of the binding of bilirubin to collagen. Urea and thermal denaturation studies indicate the importance of conformation and organization of collagen fibrillar aggregates for the binding of bilirubin.

Animals↗