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A M Kidwai

Publications and source records attributed to A M Kidwai.

At least 19 recordsLinked to original sources
PubMed1995

A step towards developing the expertise to control hunger and satiety: regulatory role of satiomem--a membrane proteoglycan.

Regulation of hunger and satiety is a complex process thought to be controlled by a complex interplay of neurotransmitters in the hypothalamic region of the brain. Reduced food intake or anorexia has also been observed under various disease or disorder conditions including AIDS and cancer. On the other hand, increased appetite because of some impairment of central mechanisms regulating the food intake could also cause/obesity. A large number of substances including neuropeptides, hormones, drugs, and synthetic peptides have been implicated in the regulation of appetite and food intake behavior in normal as well as disease or disorder conditions. Most of these substances are not directly involved in the regulation of normal hunger and satiety but exert their effect indirectly via other media. Some of them are involved under certain pathologic conditions and during the course they become involved directly or indirectly in the triggering of hunger and satiety regulatory mechanism. Recently, we have been able to isolate and purify an endogenous proteoglycan from membranes of animal and plant sources. This membrane anchored proteoglycan termed as 'Satiomem' reduces food intake without any rebound effects and has no apparent toxicity. It also fulfils all the criteria of a true satiety or anorexigenic substance. The release of satiomem from the cell surface could be mediated by a specific phospholipase-C. Satiomem seems to be involved in transducing activating signals and may also act as a source of second messenger for the regulatory mechanism of appetite. This article summarizes the regulatory aspects of hunger and satiety mechanisms controlled by endogenous substances with the emphasis on our present knowledge about satiomem.

Animals↗
PubMed1994

Calpain from rat intestinal epithelial cells: age-dependent dynamics during cell differentiation.

Micromolar and millimolar Ca(2+)-requiring neutral protease (calpain I and calpain II) along with their endogenous inhibitor calpastatin were isolated and partially purified from the same preparation of rat intestinal epithelial cells. Calpain I and II were partially purified by 1300 and 900-fold with 57 and 53 per cent yield, respectively. The optimum assay conditions revealed pH 7.5, 20 min incubation at 25 degrees C and 0.24% casein substrate for both calpains. The optimum calcium concentration obtained for calpain I and II were 25 microM and 4 mM, respectively. Distribution of rat intestinal epithelial cells calpain I and II along with calpastatin during cell differentiation stages in weanling to senescence age were studied. Calpain I in weanling rats was in an increasing order from villus to crypt regions. Adult rats indicated well expressed consistent calpain I throughout the differentiation stages. Whereas, significant lowering towards crypt region cells were evident in old rats. Calpain II in weanling and adult rats was found to be consistent throughout the differentiation stages. Old animals revealed an increasing trend from villus to crypt region with insignificant activity present in upper villus cells. Concomitantly, different concentrations of calpastatin were observed throughout the differentiation stages in all the age groups. Moreover, the levels of calpains exceeded that of calpastatin in most of the epithelial cell populations during developmental stages. In addition to casein, intestinal epithelial cell membranes were found to be equally good substrates for calpains. Proteolytic susceptibility of weanling, adult and old rat membrane proteins varied significantly all along the ageing process in rats. Simultaneous age-dependent calpastatin response were also evident. Taken together the results obtained provided strong evidence that calpain plays significant role in rat intestinal cell differentiation and ageing process with calpastatin as its specific regulatory protein.

Aging↗
PubMed1994

Experimental anorexigenic effect of a membrane proteoglycan isolated from plants.

The cessation of eating under normal physiological conditions is a voluntary act induced by a conscious sensation known as satiety. In pathological situations there is loss of appetite or anorexia. We have been able to isolate and characterize a proteoglycan from membranes of mono- and dicotyledonous plant sprouts which reduced the food intake significantly when injected into murine model systems without any rebound. Due to its membrane origin, it has been termed 'satiomem'. The plant proteoglycan (50 kDa) consisted of 70-85% carbohydrates and 15-30% proteins.

Animals↗
PubMed1993

A novel plant membrane proteoglycan which causes anorexia in animals.

Hunger and satiety are complex interplay of several factors in human and animal species. Reduced food intake has also been observed under various pathological conditions. Earlier, we have been able to isolate an endogenous glycoprotein from erythrocyte membranes, which causes anorexia in rats. In the present study, a similar anorexigenic proteoglycan from Mung bean sprout membranes has been isolated and purified. The proteoglycan (50 kDa) consisted of 70-85% carbohydrate with galactose, glucose galactosamine and mannose as the main sugars. Protein part on analysis showed higher glutamic acid and serine content. This proteoglycan reduces food intake when injected in rats deprived of food for 96 hr as well as normally fed rats, mice and rabbits without any rebound. The TCA-soluble proteoglycan from different plant sources have also been compared for their anorexigenic activity. The similarities observed among plant and animal cell membrane proteoglycans with satietins isolated from human blood plasma could be due to membrane origin of satietins.

Amino Acids↗
PubMed1992

Biochemical analysis of jejunal brush border membrane of golden hamster: pathogenic modulations due to ancylostomiasis.

The common hookworm (Ancylostoma ceylanicum) infection of humans was studied in golden hamsters model system. Significant biochemical modulations were observed in hamster jejunal brush border membrane (BBM), the primary site of infection. Analysis of BBM at the peak of infection (3-weeks) revealed a marked decrease in the activities of sucrase, lactase and maltase, while activities of alkaline phosphatase, (Ca2+ + Mg2+)-ATPase and gamma-glutamyl transpeptidase were increased. Kinetic studies conducted with maltase, a superficially localised enzyme of jejunal BBM, revealed loss of enzyme active site during the infection. Among other constituents, the levels of cholesterol and triglycerides were significantly decreased with slight increase in phospholipid content in the infected animals. The hookworm infection also caused a decline in total hexose content indicating an altered membrane glycocalyx. Conversely, there was significant enhancement of hydroxyproline and sialic acid contents. SDS-PAGE analysis showed an enhancement in both low and high molecular weight proteins in jejunal BBM preparations of the infected group. Gel electrophoresis of glycoproteins further revealed the appearance of two additional peaks in the low molecular weight region and concomitant disappearance of a peak in the high molecular weight region. These results strongly support the view that the hookworm infection causes severe damage not to the site of attachment alone but also to the entire cell lining of the jejunum and therefore could influence overall digestion and absorption.

Ancylostomiasis↗
PubMed1991

Membrane damaging potential of photosensitized riboflavin.

Riboflavin upon exposure to UV and visible radiations has been shown to produce active oxygen species. The present work deals with erythrocyte membrane as model system to study the damaging potential of photosensitized riboflavin. Membrane preparations (2.5 mg protein/ml) following exposure to sunlight in presence of riboflavin for different time intervals revealed significant inhibition of ATPases, p-nitrophenyl phosphatase and acetylcholinesterase. Considerable increase in lipid peroxidation was caused by the photosensitized riboflavin. Quenching studies using specific scavengers indicated remarkable inhibition. The production and identification of reactive oxygen species by photosensitized riboflavin and their possible involvement in membrane damaging effect has been discussed.

Erythrocyte Membrane↗
PubMed1990

An anorectic proteoglycan of membrane origin.

The endogenous substance(s) involved in the regulation of food intake has been isolated from serum, urine and feces. In the present study, a similar type of anorexigenic proteoglycan was isolated from human rat erythrocyte membranes and rat liver membranes. Membranes were suspended in 2.0% deoxycholate and allowed to stand at 25 degrees C for 30 min. The suspension was treated with 5% TCA, supernatant was collected, dialyzed and concentrated. TCA-soluble proteins were fractionated on Sephadex G-150. The active second peak fractions were further purified on DEAE-Sephadex A-25. Biologically active substance reduced the appetite in rats significantly when given intraperitoneally. The proteoglycan (50 kDa) consisted of 70-85% carbohydrate. Similar properties of plasma and membrane anorectic substance further indicated its membrane origin. We believe that this anorectic proteoglycan is anchored to cell membranes and released into the blood circulation to regulate the food intake.

Animals↗
PubMed1987

Interaction of di- and tributyltin chloride with human erythrocyte membrane.

Analysis of the binding of tributyltin chloride (TBT) to human erythrocyte membrane indicated a single class of binding site with an affinity of approximately 6.78 X 10(3) M-1, whereas dibutyltin dichloride (DBT) showed the presence of more than one class of binding sites with a high affinity value of 2.53 X 10(4) M-1 and a low affinity value of 2.06 X 10(3) M-1. Membrane protein binding studies revealed that both di- and tributyltin compounds bind significantly with band 3 protein of the erythrocyte membrane. These results indicate the significant interactions of erythrocyte membrane components with alkyltin compounds.

Erythrocyte Membrane↗
PubMed1987

Isolation and characterization of basement membrane from frog skeletal muscle.

Isolation of basement membrane from frog skeletal muscle has been described. The membrane preparation contained 35 micrograms hexoses, 1.72 micrograms sialic acid, 6.8 micrograms phospholipids, 0.21 micrograms cholesterol/mg protein. Na + K-ATPase and 5'-nucleotidase could not be detected in the membrane preparation. Glycine accounted for about 20% of the total amino acids. On SDS-PAGE, the membrane resolved into 20-22 polypeptide bands.

Amino Acids↗
PubMed1986

Effects of fluoride on membrane permeability and brush border enzymes of rat intestine in situ.

The effect of different concentrations of sodium fluoride (12, 24, 48 and 96 mM), instilled into the ligated intestine of anaesthetized rats for 30 min, on intestinal permeability and some brush border enzymes was investigated. A concentration-dependent change in permeability was observed; there was an increase in the volume of luminal fluid and altered net transport of Na+ and K K+ ions. The change in permeability was accompanied by increased protein, sialic acid and nucleic acid accumulation in the luminal fluid. A striking loss of brush border alkaline phosphatase (41%) sucrase (59%) and gamma-glutamyl transpeptidase (73%) activities was observed at 96 mM fluoride with a corresponding increase in the activity of these enzymes in luminal fluid, while 12 mM fluoride did not produce any significant effect. This loss was probably not due to an inhibition of the enzymes by fluoride since in vitro experiments did not produce any such effect over a range of NaF concentrations (0-32 mM) except on alkaline phosphatase activity at the 32 mM NaF concentration. The studies, therefore, suggest that the loss of brush-border enzyme activities observed in situ was most probably due to membrane damage caused by the high fluoride concentration.

Alkaline Phosphatase↗
PubMed1986

Effect of fluoride on uptake of D-glucose by isolated epithelial cells of rat intestine.

Inhibition on uptake of D-glucose by isolated intestinal epithelial cells (IIEC) was observed when the fluoride concentration ranged between 0.25 and 5 mM. Active transport was almost completely inhibited at 5 mM. When CaCl2 was added to fluoride, the inhibitory effect on glucose uptake was abolished. Preincubation of IIEC with different concentrations of fluoride (2.5-5.0 mM) for different intervals of time (2-20 min) at different pH levels (6.2-7.8) and temperatures (0-37 degrees C) revealed that the conditions which led to higher uptake of fluoride by IIEC produced maximum inhibition. The degree of inhibition was not appreciably altered by a change in glucose concentrations. A concentration-dependent effect of fluoride on lactic acid and carbon dioxide production by IIEC was also observed.

Animals↗