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Biomedical subjects

A K Sen

Publications and source records attributed to A K Sen.

At least 55 records · Page 3Linked to original sources
PubMed1989

Studies on the development of a medium with peptone and casein hydrolysate for the production of foot-and-mouth disease vaccine in BHK-21 cells.

Studies were undertaken to develop a cheaper medium with indigenous sources of peptone and casein hydrolysate for continuous culture of BHK-21 (suspension) cells and production of foot-and-mouth disease (FMD) vaccine. Eleven batches of experimental media were prepared using different indigenous sources of casein hydrolysate and peptone. These batches of media were tested for the growth of Razi BHK-21 cells in suspension and compared with the growth in control Eagle's medium. Out of eleven batches only four batches of the media produced cell growth equivalent to that with the Eagle's medium. Cells passaged in these batches of the experimental media supported virus growth and titres were comparable with those in Eagle's medium. Experimental batches of vaccine against FMD virus type A5 were prepared on a pilot scale as well as on a fermenter scale. The protection indices of these vaccine in guinea-pigs were satisfactory and induced 100% protection in cattle. One source each of peptone and casein hydrolysate was found suitable for the experimental medium. The medium developed is able to replace 10 out of 13 amino acids and also tryptose phosphate broth in Eagle's medium and is expected to reduce the cost of medium by 33% compared with Eagle's medium.

Animals↗
PubMed1989

Altered myocardial prostaglandin synthesis in spontaneously diabetic rats.

Patients with diabetes mellitus have an increased susceptibility to heart disease. The exact mechanism for this phenomenon is unclear. Abnormalities in prostaglandin (PG) production have been suggested as a possible cause. In this connection, we examined the PG synthetic capacity of cardiac microsomes from spontaneously diabetic rats. Cardiac microsomes from diabetic and control rats produced varying amounts of 6-keto-PGF1 alpha (stable degradation product of PGI2), PGE2, PGD2, PGF2 alpha, and TXB2 (stable breakdown product of TXA2). In both instances the production of 6-keto-PGF1 alpha predominated, however, microsomes from diabetic rats showed markedly greater conversion of arachidonic acid to all the PG products, especially 6-keto-PGF1 alpha. When PGF2 alpha metabolism was detected between diabetic and control heart preparations. These results show an enhanced cyclooxygenase activity in diabetic rat hearts without any change in prostaglandin dehydrogenase activity. Such a change may promote some of the cardiac alterations seen in diabetic mellitus.

Animals↗
PubMed1989

Effect of diabetes on metabolic coronary dilatation in the rat.

There is increasing evidence that patients with diabetes mellitus are prone to ischaemic heart disease. This study examined cardiac hyperactivity and its consequent metabolically induced coronary dilatation in isolated, perfused, electrically paced rat hearts from control and spontaneously diabetic Bio-Breeding (BB) rats. Cardiostimulation produced by noradrenaline, calcium, or by tachycardia elicited increases in coronary flow that were significantly lower in diabetic hearts. However, the inotropic responses to noradrenaline and calcium in diabetic preparations were comparable to control. When coronary vascular reactivity was tested with sodium nitroprusside and adenosine, a decreased dilator response was observed with adenosine in diabetic hearts while no difference was observed with sodium nitroprusside. It is suggested that failure in the adaptive coronary flow response to cardiac hyperactivity in diabetes may, in part, be responsible for the higher incidence of ischaemic heart disease in the diabetic population.

Adenosine↗
PubMed1989

Alterations in atrial reactivity in a strain of spontaneously diabetic rats.

1. The present study examined the reactivity of atria from control and spontaneously diabetic rats to various adrenoceptor agonists and to adenosine. 2. Isoprenaline (1.5 nM-1500 nM) produced concentration-dependent increases in inotropy which were unchanged in diabetic atria. However, the sensitivity to isoprenaline-induced changes in chronotropy was reduced in diabetic preparations. 3. In the presence of propranolol (2 microM), phenylephrine (0.2 microM-100 microM) produced concentration-dependent increases in both inotropy and chronotropy; however, atria from diabetic rats exhibited a much greater maximal response. The diabetic state did not alter the sensitivity to phenylephrine. 4. Adenosine (0.15 microM-300 microM) produced concentration-dependent decreases in both inotropy and chronotropy which were unchanged in diabetic atria. 5. Radioligand binding studies revealed that both alpha 1- and beta-adrenoceptor populations were substantially reduced in atria from diabetic rats. However, there was no change in receptor affinity for either adrenoceptor. 6. These results show that diabetes leads to an alteration in atrial reactivity to adrenoceptor stimulation. Future studies examining steps following hormone-receptor coupling are required in order to characterize this defect.

Adenosine↗
PubMed1989

Partial replacement of serum with peptone and lactalbumin hydrolysate for the production of foot-and-mouth disease vaccine in BHK-21 cells.

Two batches of experimental media were prepared with Difco-Peptone and Centron-Peptone in combination with lactalbumin hydrolysate (LAH) in Eagle's salts containing 3 amino acids, vitamins and 1% bovine serum. Both medium batches supported the growth of Razi BHK-21 cells in serial passages and the replication of foot-and-mouth disease (FMD) virus type "A". The infectivity and complement fixing antigen (CFU) titres of the virus were comparable with those in Eagle's medium. The protection indices "C" of the experimental batches of vaccine were highly satisfactory. The experimental media saved up to 90% of serum in comparison with Eagle's medium.

Animals↗
PubMed1988

On the time course of the reversible Michaelis-Menten reaction.

The methods of Padé approximants and Euler transformation are used to construct approximate solutions for the time course of the reversible Michaelis-Menten reaction. The solutions are found to describe the concentrations of the various species quite accurately throughout and beyond the transient phase. To illustrate the results, the ratio of the reverse bi-molecular rate constant to the forward bi-molecular rate constant, k2/k1, is varied from 0.1 to 5, and the initial enzyme-to-substrate concentration ratio is changed from 0.01 to 5. Only when k-2/k1 is less than one, the concentration of the intermediate complex, y(t), undergoes a maximum (steady state); for all other values of this ratio, y(t) increases monotonically with time t, to the equilibrium value, i.e. no maximum is attained. The present methods are particularly useful when the total enzyme concentration is comparable to, or greater than the initial substrate concentration, a situation commonly found under in vivo conditions.

Enzymes↗
PubMed1988

Impairment of endothelium-dependent relaxation in aortae from spontaneously diabetic rats.

1. Diabetes mellitus is known to produce alterations in vascular reactivity. The present study examined the effects of endothelium-dependent and endothelium-independent relaxing substances on thoracic aorta from control and spontaneously diabetic rats. 2. Endothelium-dependent relaxation produced by acetylcholine or the calcium ionophore, A23187, in aortic rings precontracted with phenylephrine was significantly attenuated in diabetic vessels. 3. Relaxations produced by sodium nitroprusside or adenosine in diabetic preparations were comparable to those in control vessels. 4. The results show that diabetes leads to a specific impairment of endothelial-dependent relaxation.

Acetylcholine↗
PubMed1988

Characterization and partial purification of rat submandibular gland protein kinase C.

Membrane-bound protein kinase C of rat submandibular gland was characterized and the cytosolic kinase C of the tissue was partially purified. The membrane-bound kinase could be activated by Triton X-100 but not EGTA in the presence of both Ca2+ and phosphatidylserine (PS). The Km values for Ca2+ and PS were 150 microM and 5 micrograms, respectively. Addition of 10(-6) M diacylglycerol resulted in an increased affinity of the kinase for Ca2+ (Km = 10 microM). Phorbol 12,13-dibutyrate activated the kinase in the absence of exogenous Ca2+ and PS, suggesting that adequate amounts of each activator are present in the membrane itself. Polymyxin B inhibited the stimulated kinase C activity in a concentration-dependent manner. This inhibition could be overcome by addition of PS. The cytosolic kinase was partially purified 133-fold by chromatography on columns of DEAE-Sephacel and S-300 Sephacryl. The total kinase activity increased with respect to the kinase activity measured in the starting material with column chromatography, suggesting that an inhibitor is present in the cytosolic fraction of the tissue.

Animals↗
PubMed1987

Studies on chemical modification of cold agglutinin from the snail Achatina fulica.

The cold agglutinin isolated from the albumin gland of the snail Achatina fulica was modified with various chemical reagents in order to detect the amino acids and/or carbohydrate residues present in its carbohydrate-binding sites. Treatment with reagents considered specific for modification of lysine, arginine and tryptophan residues of the cold agglutinin did not affect the carbohydrate-binding activity of the agglutinin. Modification of tyrosine residues showed some change. However, modification with carbodiimide followed by alpha-aminobutyric acid methyl ester causes almost complete loss of its binding activity, indicating the involvement of aspartic acid and glutamic acid in its carbohydrate-binding activity. The carbohydrate residues of the cold agglutinin were removed by beta-elimination reaction, indicating that the sugars are O-glycosidically linked to protein part of the molecule. Removal of galactose residues from the cold agglutinin by the action of beta-galactosidase indicated that the galactose molecules are beta-linked. These carbohydrate-modified glycoproteins showed a marked change in agglutination property, i.e. they agglutinated rabbit erythrocytes at both 10 degrees C and 25 degrees C, indicating that the galactose residues of the glycoprotein play an important role in the cold-agglutination property of the glycoprotein. The c.d. data showed the presence of an almost identical type of random-coil conformation in the native cold agglutinin at 10 degrees C and in the carbohydrate-modified glycoprotein at 10 degrees C and 25 degrees C. This particular random-coil conformation is essential for carbohydrate-binding property of the agglutinin.

Agglutinins↗
PubMed1987

Phosphorylation of the alpha-subunit of (Na+ + K+)-ATPase by carbachol in tissue slices and the role of phosphoproteins in stimulus-secretion coupling.

This study examined the changes in protein phosphorylation in response to cholinergic (muscarinic) stimulation of salivary secretion in the rat submandibular gland. Carbachol stimulation was associated with phosphorylation in a number of protein bands as detected by sodium dodecyl sulfate (SDS) polyacrylamide gel electrophoresis and autoradiography. The molecular masses (Mr) of two proteins, in which the amount of phosphorylation more than doubled in response to carbachol, were 22,000 and 96,000. The Mr 96,000 protein precipitated at 120,000 X g while most of the Mr 22,000 protein remained in the supernatant at this speed. The effect of carbachol on the phosphorylation of the Mr 22,000 and 96,000 proteins was blocked by atropine, indicating that the cholinergic receptor involved is muscarinic. The time course of phosphorylation of the Mr 22,000 protein consisted of a rapid increase in phosphorylation within the first min of carbachol stimulation. This increased phosphorylation persisted for less than 1 min. The increased phosphorylation of the Mr 96,000 protein also occurred within the first min but it persisted for at least 10 min. However, removal of the muscarinic agonist, carbachol, resulted in the rapid dephosphorylation of this protein. When the plasma membranes were purified, the Mr 96,000 protein was phosphorylated by ATP in the presence of Na+ and Mg2+. It was dephosphorylated by K+. This proves that the Mr 96,000 dalton protein is the alpha-subunit of the (Na+ + K+)-ATPase.

Animals↗
PubMed1987

Effect of job satisfaction on stress, performance and health in self-paced repetitive work.

The present study was designed to investigate the effect of job satisfaction on stress, performance and health in self-paced repetitive work. There were two groups of subjects. One group consisted of 41 subjects with a high score on job satisfaction and the second group consisted of an equal number of subjects with a low score on job satisfaction. The mean age and experience of high and low satisfied groups are respectively 34.63 and 13.60 and 34.14 and 15.51 years. The educational qualifications of all the workers were below primary level. The results of the study indicate that the low satisfied workers experience more stress and describe their job more unfavourably than the highly satisfied workers. It is also observed that the high satisfied workers are better performers and possess good health (fewer health complaints and good mental health) than that the dissatisfied workers. The findings of the study suggest that the quality of working life may be improved by increasing the job satisfaction of the workers.

Adult↗
PubMed1987

Tumor-promoting phorbol esters inhibit cardiac functions and induce redistribution of protein kinase C in perfused beating rat heart.

Activation of protein kinase C has been implicated in the regulation of a variety of cellular reactions. Although we, and others, have found protein kinase C and its substrate proteins to be present in both membrane and cytosolic fractions in the heart, the physiologic role of this kinase in the regulation of cardiac functions remains unknown. In the present study, we found that in isolated perfused rat heart, administration of phorbol esters 4 beta-phorbol 12,13-dibutyrate(PDBu) and 12-0-tetradecanoylphorbol 13-acetate(TPA), which are specific activators of protein kinase C, produced marked dose-dependent negative changes in inotropy and chronotropy. A dose-dependent decrease in coronary flow was also observed. The diacylglycerol analogues, 1,2-oleoylacetyl-glycerol and 1,2-dioctanoylglycerol, produced similar effects as the active phorbol esters on these isolated perfused hearts. An inactive analogue of phorbol ester, 4 alpha-phorbol, failed to produce any effect. Protein kinase C activity in both membrane and cytosolic fractions prepared from rat heart could be activated by TPA and PDBu at the same concentration range as used in the experiments with perfused hearts. Following perfusion of the hearts with PDBu, a rapid translocation of protein kinase C from cytosolic to membrane fractions was also observed. Our findings provide the first direct evidence that protein kinase C may play a potentially important role in the regulation of cardiac functions.

Animals↗
PubMed1986

Species-dependent isoenzyme subtypes of membrane-bound cyclic AMP-dependent protein kinase in highly purified cardiac sarcolemma.

Highly purified sarcolemma from dog and pig cardiac muscle has been shown to contain significant activities of a membrane-bound cyclic AMP-dependent protein kinase. In addition, these membranes undergo endogenous phosphorylation when incubated with Mg2+ and [gamma-32P]ATP. By comparing 32P-labelled patterns obtained with [gamma-32P]ATP and the photoaffinity label 8-azidoadenosine 3':5'-[32P]monophosphate (8-azido-cyclic [32P]AMP), we have demonstrated that, whereas the major kinase isoenzyme in dog sarcolemma was Type II, that in the pig membrane was the Type I isoenzyme.

Adenosine Triphosphate↗
PubMed1986

Characterization of the membrane-bound protein kinase C and its substrate proteins in canine cardiac sarcolemma.

Cardiac sarcolemma was purified from canine ventricles. Enrichment of the sarcolemmal membranes was demonstrated by the high (Na+ + K+)-ATPase activity of 28.0 +/- 1.5 mumol Pi/mg protein per h and the high concentration of muscarinic receptors with the Bmax of 8.2 +/- 2.5 pmol/mg protein as determined by [3H]QNB binding. The purified sarcolemma also contains significant levels of a membrane-bound Ca2+ and phospholipid-dependent protein kinase (protein kinase C). To elucidate the protein kinase C activity in sarcolemma, a prior incubation of the membranes with EGTA and Triton X-100 was necessary. The specific activity of protein kinase C was found to be 131.4 pmol Pi/mg per min, in the presence of 6.25 micrograms phosphatidylserine and 0.5 mM CaCl2. Treatment of sarcolemma with 12-O-tetradecanoylphorbol 13-acetate (TPA) and phorbol 12,13-dibutyrate (PBu2) resulted in a concentration-dependent activation of protein kinase C activity. The effect of TPA and PBu2 on protein kinase C in sarcolemma was independent of exogenous Ca2+ and phosphatidylserine. Polymyxin B inhibited phorbol-ester-induced activation of protein kinase C activity. The distribution of protein kinase C in the cytosolic fraction was also examined. The specific activity of the kinase in the cytosolic fraction was 59.7 pmol Pi/mg per min. However, the total protein kinase C activity in the cytosol was 213500 pmol Pi/min, compared to that of 1025 pmol Pi/min in the sarcolemma isolated from approx. 100 g of canine ventricular muscle. Several endogenous proteins in cardiac sarcolemma were phosphorylated in the presence of Ca2+ and phosphatidylserine. The major substrates for protein kinase C were proteins of Mr 94 000, 87 000, 78 000, 51 000, 46 000, 11 500 and 10 000. Most of these substrate proteins have not been identified before. Other proteins of Mr 38 000, 31 000 and 15 000 were markedly phosphorylated in the presence of Ca2+ only. Phosphorylation of phospholamban (Mr 27 000 and 11 000) was also stimulated in the presence of Ca2+ and phosphatidylserine, but the low Mr form of phospholamban was distinct from two other low Mr substrate proteins for protein kinase C. Polymyxin B was more selective in inhibiting the protein kinase C dependent phosphorylation. On the other hand, trifluoperazine selectively inhibited the phosphorylation of phospholamban and Mr 15 000 protein. Although the exact function of this kinase is unknown, based on these observations, we believe that protein kinase C in the cardiac sarcolemma may play an important role in the cell-surface-signal regulated cardiac function.

Animals↗