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Biomedical subjects

K Ray

Publications and source records attributed to K Ray.

At least 181 records · Page 10Linked to original sources
PubMed1986

Comparative studies on lens neutral endopeptidase and pituitary neutral proteinase: two closely similar enzymes.

A neutral endopeptidase (EC 3.4.24.5) previously thought to be unique to the eye lens has been found to be closely similar if not identical in native molecular size, component polypeptides and antigenic structure to a neutral proteinase from pituitary. Here we investigated some subtle differences in properties of the two enzymes, such as the effects of temperature, divalent cations and SDS on their activities with respect to different substrates. We conclude that the pituitary enzyme may have a relatively more compact structure requiring relaxation by low SDS concentration or higher temperature for maximum activity.

Animals↗
PubMed1986

Effect of halothane anaesthesia on salivary elimination of paracetamol.

The effect of halothane anaesthesia on paracetamol elimination was studied in 6 male patients undergoing short surgical procedures. Seven males operated on for the same indications under epidural anaesthesia served as the control group. Paracetamol concentration in saliva was measured at intervals on the day before and after surgery. Paracetamol t1/2 significantly decreased from 2.1 to 0.96 h and clearance rate (CL) significantly increased from 8.7 to 17.0 ml min-1 kg-1, when compared with the preoperative values. The control group also showed a significant but smaller alteration in the parameters. The results suggest that halothane anaesthesia per se may enhance the hepatic metabolism of paracetamol.

Acetaminophen↗
PubMed1985

Purification of neutral lens endopeptidase: close similarity to a neutral proteinase in pituitary.

A neutral endopeptidase (EC 3.4.24.5) that degrades alpha- and beta-crystallins occurs in mammalian lens. A procedure for purification of this enzyme from bovine lens is described. The enzyme appears to have a high molecular weight (Mr approximately equal to 700,000) and under denaturing conditions dissociates into at least eight polypeptide subunits with Mrs ranging from 24,000 to 32,000. A neutral proteinase in bovine pituitary has been reported previously to have similar structural characteristics. We have found that this enzyme purified from bovine pituitary is indistinguishable in molecular weight and in subunit composition from bovine lens endopeptidase. In addition, antiserum raised in rabbit against the purified lens enzyme crossreacts with bovine pituitary enzyme. When examined side by side in Ouchterlony double-diffusion tests, the two enzymes give a continuous precipitin line with no spurring. It is concluded that lens neutral endopeptidase and pituitary neutral proteinase are structurally closely similar, if not identical. This is a surprising result because it had been thought previously that the lens endopeptidase was unique to lens, where its crystallin substrates comprise a large proportion of the total tissue protein. In other tissues, crystallin is either absent or occurs, at most, in trace amounts.

Animals↗
PubMed1985

Effect of short surgical procedures on salivary paracetamol elimination.

The effect of short surgical procedures on paracetamol elimination was studied in seven male patients undergoing surgery with epidural anaesthesia. Five healthy volunteers who did not undergo surgery served as a control group. Paracetamol concentration was measured in saliva at various intervals 1 day before and after surgery. Paracetamol half-life (t1/2,z) decreased and metabolic clearance rate (CL) increased after surgery as compared to preoperative values. The results suggest that surgical stress may enhance the hepatic metabolism of paracetamol.

Acetaminophen↗
PubMed1985

Assay of total and free propranolol in plasma by liquid chromatography with fluorometric detection.

We report a liquid-chromatographic method for assay of total and free propranolol and its metabolite, propranolol glycol, in plasma. An ultrafiltration device is used to separate the free drugs from the protein-bound drugs. The total and free drugs are isolated from plasma or ultrafiltrate by liquid-solid extraction on a Waters C18 SEP-PAK and the drugs are quantified on a C18 mu-Bondpak radial-compression column. The mobile phase consists of equal parts of methanol and a solution of potassium 50 mmol/L phosphate and 2.5 mmol/L 1-pentane-sulfonic acid, pH 5.0. Detection was by fluorescence, with excitation at 296 nm and emission at 338 nm. Time required for sample preparation for total-propranolol assay is 40 min per eight samples. Sample preparation for free-propranolol assay requires an additional 1 h per eight samples. Chromatography requires 15 min per sample. The extraction recovery is approximately 75% and the assay curve is linear from 5 to 400 micrograms/L. The run-to-run CV is 4% for total propranolol, 15% for free propranolol.

Binding, Competitive↗
PubMed1984

Anion-induced increases in the affinity of colcemid binding to tubulin.

Colcemid binds tubulin rapidly and reversibly in contrast to colchicine which binds tubulin relatively slowly and essentially irreversibly. At 37 degrees C the association rate constant for colcemid binding is 1.88 X 10(6) M-1 h-1, about 10 times higher than that for colchicine; this is reflected in the activation energies for binding which are 51.4 kJ/mol for colcemid and 84.8 kJ/mol for colchicine. Scatchard analysis indicates two binding sites on tubulin having different affinities for colcemid. The high-affinity site (Ka = 0.7 X 10(5) M-1 at 37 degrees C) is sensitive to temperature and binds both colchicine and colcemid and hence they are mutually competitive inhibitors. The low-affinity site (Kb = 1.2 X 10(4) M-1) is rather insensitive to temperature and binds only colcemid. Like colchicine, 0.6 mol of colcemid are bound/mol of tubulin dimer (at the high-affinity site) and the reaction is entropy driven (163 J K-1 mol-1). Similar to colchicine, colcemid binding to tubulin is stimulated by certain anions (viz. sulfate and tartrate) but by a different mechanism. Colcemid binding affinity at the lower-affinity site of tubulin is increased in the presence of ammonium sulfate. Interestingly, the lower-affinity site on tubulin for colcemid, even when converted to higher affinity in presence of ammonium sulfate, is not recognized by colchicine. We conclude that tubulin possesses two binding sites, one of which specifically recognized the groups present on the B-ring of colchicine molecule and is effected by the ammonium sulfate, whereas the higher-affinity site, which could accommodate both colchicine and colcemid, possibly recognized the A and C ring of colchicine.

Ammonium Sulfate↗
PubMed1984

Immunodiagnosis of malaria.

Different approaches to immunodiagnosis of malaria in an endemic country have been described in this paper. Demonstration of circulating malaria antigen may be done by gel-diffusion and counter-immunoelectrophoresis. Parasite associated antigen may be demonstrated by highly sensitive methods like radio-immunoassay or enzyme linked immuno sorbent assay. Malaria antibodies of the IgG type being long lasting do not appear to have any role in immuno-diagnosis. However, determination of malaria specific IgM antibodies by P. gallinaceum haemagglutination test or IgM immunofluorescence test may be simple and useful in immunodiagnosis of malaria. The tests though evaluated in different laboratories may not be applicable in the field for diagnosis of malaria at the present moment. However, it is envisaged that with the availability of different specificities of monoclonal antibodies by way of hybridoma technology and also with the help of recombinant DNA techniques immunodiagnosis of malaria in the field situation may become a reality.

Animals↗
PubMed1983

Opioid peptide effects on insulin release and c-AMP in islets of Langerhans.

The time course and specificity of the effect of opioid peptides on c-AMP production in the islets of Langerhans was examined. An enkephalin analogue, d-Ala2Me Phe4 Met(O)-ol enkephalin (DAMME, Sandoz) produced a significant stimulation of basal c-AMP levels, with a peak of stimulation at 5 minutes and a decline thereafter. These changes in intracellular c-AMP levels were of the same order of magnitude as those induced by other secretagogues, but did not coincide in time with the more rapid peak of enkephalin-induced insulin release. The rise in islet c-AMP and insulin secretion induced by DAMME and alpha-endorphin but not leu enkephalin was antagonised by naloxone. The effects of high and low concentrations of a variety of opioid peptides and naloxone on insulin release and islet c-AMP levels were determined, alpha-endorphin, dynorphin, leu enkephalin and met enkephalin all stimulated insulin secretion significantly, though not to the same extent. Higher concentrations of alpha-endorphin, dynorphin and met enkephalin inhibited insulin release relative to effects at low opiate concentrations. However, higher concentrations of leu enkephalin stimulated insulin release further. We conclude from these results that the mode of action of opioid peptides in stimulating insulin release is not via increased islet c-AMP exclusively. Furthermore, the results obtained with different classes of opioid suggest the presence of distinctive types of opiate receptor in islets of Langerhans.

Animals↗
PubMed1983

Effect of dynorphin on insulin and somatostatin secretion, calcium uptake, and c-AMP levels in isolated rat islets of Langerhans.

Dynorphin-[1-13], at concentrations of 5.8 X 10(-12) to 5.8 X 10(-9) M, stimulated insulin secretion from isolated islets of Langerhans of the rat, in medium containing 6 mM glucose. Higher concentrations of dynorphin had no significant effect on secretion. Dynorphin (5.8 X 10(-9) M) was unable to initiate insulin release from islets in the presence of 2 mM glucose, or to increase insulin secretion further in the presence of 20 mM glucose or 6 and 12 mM glyceraldehyde. Dynorphin-induced insulin secretion from islets was blocked by verapamil (5 microM) or by chlorpropamide (72 microM), but not by a mu opiate receptor antagonist, naloxone (0.11 microM), or by ICI 154129, a specific antagonist for the delta receptor (0.25 microM). Dynorphin had no effect on islet somatostatin secretion, under conditions in which insulin secretion was greatly stimulated. Glucose (20 mM) and glyceraldehyde (6 and 12 mM) significantly increased both insulin and somatostatin secretion. Dynorphin (5.8 X 10(-9) M) increased 45Ca2+ uptake into islets, and also increased intracellular islet c-AMP levels. These changes persisted when higher concentrations of dynorphin were used. These results suggest that (1) dynorphin is a very potent stimulus for insulin secretion; (2) dynorphin does not affect somatostatin secretion in static incubations of islets, in the same way as does glucose and glyceraldehyde; (3) dynorphin's effects may involve increased calcium ion movement and can be blocked by verapamil; (4) dynorphin can also increase islet c-AMP, and could thereby modulate the responsiveness of other secretagogues; (5) the actions of dynorphin on insulin secretion are not mediated by delta or mu opiate receptors in islets.

Animals↗