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Biomedical subjects

S K Guha

Publications and source records attributed to S K Guha.

At least 55 records · Page 3Linked to original sources
PubMed1982

Brain glucose bisphosphatase requires inosine monophosphate.

Glucose bisphosphate phosphatase has been partially purified from the cytosol of mouse brain. Enzyme activity required Mg2+ and a heat-stable cofactor. The activator was present in boiled extracts of mouse brain mitochondrial-nuclear fraction, of red blood cells, or of rabbit muscle. The chemical properties of the activator are consistent with its identification as inosine monophosphate (IMP), including its mobility in a high pressure liquid chromatography (HPLC) system capable of resolving all of the biologically important mononucleotides. A large number of other biologically important compounds were not effective, including AMP, cAMP, cGMP, and UMP, GMP, purified by HPLC, (50 or 74 microM), gave a rate about 35% of that obtained with IMP (5 microM). The enzyme was separated completely from phosphoglucomutase and significantly from glucose bisphosphate synthase. The products of the reaction are glucose-P and Pi. Fructose bisphosphate at 500 microM inhibited only 40% in the presence of 20 microM glucose bisphosphate. The activation by IMP follows hyperbolic kinetics with an apparent Ka of 5 microM in the presence of 12 microM glucose bisphosphate. The apparent Km of glucose bisphosphate was 10 microM in the presence of 50 microM IMP. There was no inhibition by 5 or 50 microM AMP or ADP. The possible regulatory importance of glucose bisphosphate in carbohydrate metabolism and the significance of the regulation of the phosphatase by the nucleotide are discussed.

Animals↗
PubMed1982

Novel mode of contraception using polymeric hydrogels. I.

A new method of fertility control has been proposed and tested. The technique involves the use of the polymer, which when injected into the vas deferens lowers the pH sufficiently so as to kill the spermatozoa passing through. The polymer provides an acidic environment for a prolonged time and slowly erodes. The fertility may be restored after complete solubility of the polymer itself over a period of time or by flushing it with a suitable solvent. This method of male contraception is nonsurgical, nonocclusive, and reversible.

Contraception↗
PubMed1982

Comparison of electrical field plethysmography with electrical impedance plethysmography.

As a means for assessing cardiac function, electrical field plethysmography (EFP) has been shown to have some features quite different from electrical impedance plethysmography (EIP). Here the two techniques are compared by using the two systems simultaneously on a subject and also with independent use in different electrode configurations. The results conform with the view that EIP is related primarily to volumetric changes of the aorta, whereas EFP is affected predominantly by changes in cardiac dimensions and orientation. Because of this difference, the standard time differential formula used for EIP is not applicable for the computation of cardiac output from the EFP waveforms. An alternative method of computation based on the amplitude of the EFP waveform is suggested.

Cardiac Output↗
PubMed1982

p-Amino salicylic acid - oxidized cellulose system: a model for long term drug delivery.

The mobilization of p-amino salicylic acid (PASA) on periodic oxidized cellulose (O.C) as a biocompatible carrier was investigated. The immobilization of the PASA is based on Schiff's base formation between the amino group of PASA and the aldehyde group of O.C. The in vivo and in vitro release of p-amino salicylic acid was studied. Such a system may be useful for the sustained delivery of the drugs in the body, since O.C. itself is a biosoluble carrier.

Aminosalicylic Acid↗
PubMed1982

Dynamics of the ampullary-isthmic junction in rabbit oviduct.

A delay in the ovum transport at the ampullary-isthmic junction (AIJ) has been confirmed by various investigators, but the mechanism of retention and release at this junction is not yet well understood. Using a technique for monitoring unobstructed Fallopian tube motility with an impedance plethysmograph, an increase in luminal diameter was observed at the time when the ova are released from the AIJ. This enlargement persists till all ova emerge from the AIJ. Hence, it seems likely that the AU relaxation is a dominant factor contributing to ova release from the AIJ.

Animals↗
PubMed1982

An intravasal non-occlusive contraceptive device in rats.

An implantable miniature biogalvanic cell was developed to kill the spermatozoa in the vas deferens by an electric current. Experiments in vitro and in vivo showed that a combination of aluminum/silver electrodes connected with platinum wires with the vas deferens fluid as n electrolyte is effective in killing spermatozoa. Female rats paired with males having biogalvanic devices in the vas deferens, which remained patent, did not produce any young.

Aluminum↗
PubMed1982

An improved above-knee prosthesis with functional versatility.

An above-knee prosthesis is described which is designed to permit the patient to assume easily the squatting and sitting cross legged postures which are a part of routine living in Afro-Asian countries. The prosthesis incorporates a multibar linkage mechanism which co-ordinates knee flexion and extension with ankle dorsiflexion and plantarflexion, and a thigh rotation system fitted at the level of the knee axis.

Amputation, Surgical↗
PubMed1979

Injectable non-occlusive chemical contraception in the male-I.

A new contraceptive technique has been proposed and tested. The method uses a novel polymer which when injected into the vas deferens, lowers the pH sufficiently kill the spermatozoa passing through. The polymer itself does not degrade in the process but can be flushed out to regain fertility. Experiments carried out on rats demonstrate the efficacy of the technique so as to have non-surgical, non-occlusive and reversible male contraception.

Animals↗
PubMed1979

Potential biosoluble carriers: biocompatibility and biodegradability of oxidized cellulose.

The biocompatibility and biodegradability of periodate oxidized cellulose is assessed in vivo. Morophological and histopathological studies over a period of six months indicate that oxidized cellulose degrades slowly without producing excessive tissue reaction. Preliminary investigations on the kinetics of degradation of oxidized cellulose in vitro, immobilization of alpha-chymotrypsin on it and the rate of the enzyme release in a solution of pH 7.4 are also briefly reported.

Animals↗
PubMed1977

Regulation of L-ornithine decarboxylase and S-adenosyl-L-methionine decarboxylase in rat ventral prostate and seminal vesicle.

1. The activities of l-ornithine decarboxylase (EC 4.1.1.17) and S-adenosyl-l-methionine decarboxylase (EC 4.1.1.50) were dramatically enhanced in both the ventral prostate and the seminal vesicle of castrated rats in response to androgenic stimulation. The time course of the stimulation of ornithine decarboxylase together with the quantitatively different response of adenosylmethionine decarboxylase to testosterone treatment in the prostate gland and seminal vesicle indicated that the enhancement in polyamine synthesis in the ventral prostate may reflect both cellular proliferation and the restoration of the secretory functions of the organ. In the seminal vesicle, however, the stimulation of the polyamine-biosynthetic pathway more closely resembled the pattern found in other rat tissues, such as regenerating liver, undergoing compensatory growth. 2. Ornithine decarboxylase activity in the ventral prostate and especially in the seminal vesicle of sexually mature rat was diminished in vivo by various short-chain diamines such as 1,2-diaminoethane, 1,3-diaminopropane and putrescine (1,4-diaminobutane). These diamines had no direct effect on the enzyme activity in vitro. 3. In contrast with the marginal decrease in ornithine decarboxylase activity produced by diaminoethane in the ventral prostate of non-castrated animals, repeated injections of the latter amine completely prevented the intense stimulation of the enzyme activity in the ventral prostate and seminal vesicle of castrated rats at 24h after the commencement of testosterone treatment. 4. The decrease in ornithine decarboxylase activity observed after injections of diamines (putrescine) in the ventral prostate was apparently associated with a similar decrease in the amount of immunoreactive protein as revealed by immunotitration of the enzyme with antiserum to rat ornithine decarboxylase.

Adenosylmethionine Decarboxylase↗
PubMed1977

Polyamines and their biosynthetic enzymes in Ehrlich ascites-carcinoma cells. Modification of tumour polyamine pattern by diamines.

1. Ehrlich ascites-carcinoma cells contained relatively high concentrations of spermidine and spermine, but the putrescine content of the washed cells was less than 10% of that of higher polyamines. 2. Ascites-tumour cells likewise exhibited high activities of L-ornithine decarboxylase (EC 4.1.1.17), S-adenosyl-L-methionine decarboxylase (EC 4.1.1.50), spermidine synthase (EC 2.5.1.16) and spermine synthase. 3. During the first days after the inoculation, the polyamine pattern of the ascites cells was characterized by a high molar ratio of spermidine to spermine, which markedly decreased on aging of the cells. 4. Various diamines injected into mice bearing ascites cells rapidly and powerfully decreased ornithine decarboxylase activity in the carcinoma cells, apparently through a mechanism that was not a direct inhibition of the enzyme in vitro. Cadaverine (1,5-diaminopentane) and 1,6-diaminohexane were the most potent inhibitors of ornithine decarboxylase among the amines tested. 5. Chronic treatment of the mice with diamines resulted in a virtually complete disappearance of ornithine decarboxylase activity, and after 24h a significant decline in spermidine accumulation. 6. Cadaverine appeared to be an especially suitable compound for use as an inhibitor of the synthesis of higher polyamines, at least in Ehrlich ascites cells, since this diamine also acted as a competitive inhibitor for putrescine in the spermidine synthase reaction without being incorporated into the higher polyamines.

Adenosylmethionine Decarboxylase↗