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Biomedical subjects

N Nath

Publications and source records attributed to N Nath.

At least 19 recordsLinked to original sources
PubMed1994

A mechanistic approach into a diabetic serum factor-mediated release of beta-glucuronidase in normal neutrophils.

The possible mechanism of diabetic serum factor (DSF)-mediated lysosomal degranulation has been investigated. It was observed that pertussis toxin, sodium fluoride and vanadate could significantly inhibit DSF-mediated beta-glucuronidase release, whereas atropine exhibited only a partial blockage against DSF. Since DSF can generate toxic free radicals, various free radical quenchers were tested in order to evaluate their contributions. Superoxide dismutase was found to be the most effective in inhibiting lysosomal release as compared to catalase and peroxidase. The mixtures of all the enzymes failed to exhibit any additive effect. Interaction of DSF with heparin, insulin and Con A revealed that heparin can completely block DSF-mediated lysosomal release. The implications of the observations are discussed.

Adult↗
PubMed1994

Plausible involvement of extralysosomal proteinase in derangement of leucocytic Ca2+/Mg2+ ATPase in diabetes.

Translocation of calcium activated neutral proteinase from cytosol to plasma membrane, concurrently with decrease in the activity of membrane bound Ca2+/Mg2+ ATPase has been detected in diabetic polymorphonuclear leucocytes. Plausible involvement of the extralysosomal proteinase in the derangement of the Ca2+/Mg2+ ATPase is indicated by non restoration of the enzyme activity on treatment with activators such as trypsin or calmodulin and enhanced membrane translocation of the proteinase observed with concomitant decrease in the activity of Ca2+/Mg2+ ATPase in normal neutrophils on insult with diabetic serum factor.

Adult↗
PubMed1993

Presence of 11 beta-hydroxysteroid dehydrogenase enzyme in the human prostate tumor cell line LNCaP.

11 beta-Hydroxysteroid dehydrogenase (11 beta-HSD) is the enzyme that catalyzes the reversible oxidation of the biologically active steroid cortisol and corticosterone to their inactive metabolites cortisone and dehydrocorticosterone. We report its presence in significant levels in the human prostate carcinoma cell line LNCaP cultured in medium RPMI-1640 with 10% fetal calf serum (FCS). The 11-dehydrogenase activity of 11 beta-HSD is present, while the 11-reductase activity is undetectable in these tumor cells under the present culture conditions. The enzyme activity is found to be linear with time of incubation, and is proportional to plated cell density. The enzymatic activity can be determined in cultures maintained for longer times. Carbenoxolone, the potential inhibitor of the 11 beta-HSD, inhibits 95% of the dehydrogenase activity of the tumor cells when used in nM concentration. The presence of this enzyme in tumor cell line indicates that 11 beta-HSD plays an important role in maintaining the active glucocorticoid levels in the prostate.

11-beta-Hydroxysteroid Dehydrogenases↗
PubMed1993

Characterization of 11 beta-hydroxysteroid dehydrogenase of human placenta: evidence for the existence of two species of 11 beta-hydroxysteroid dehydrogenase.

The enzyme, 11 beta-hydroxysteroid dehydrogenase converts the active glucocorticoids cortisol and corticosterone to their inactive 11-oxo metabolites cortisone and dehydrocorticosterone, respectively. The properties of the human placental 11 beta-hydroxysteroid dehydrogenase (11 beta-HSD) were studied. The enzyme was active in the oxidative and reductive directions. pH optimum for 11 beta-dehydrogenase activity was in the range of 7-10 and for 11-oxoreductase it was in the range of 5.5-6.0. The crude placental homogenate was unstable. Reductase activity was more labile than dehydrogenase activity. Removal of cytosol enabled the enzyme to retain activity. 11 beta-HSD a membrane bound enzyme was distributed in all particulate subcellular fractions. Addition of detergent released latent activity of 11 beta-dehydrogenase and inactivated 11-reductase activity. Both corticosterone and cortisol were substrates for the enzyme. The Km value with corticosterone as substrate was much lower than with cortisol. The Km values with cortisone and dehydrocorticosterone were similar.

11-beta-Hydroxysteroid Dehydrogenases↗
PubMed1993

Status of nitric oxide free radicals in diabetic neutrophils: effect of diabetic serum factor on the generation of these species in normal neutrophils and their relation to lysosomal degranulation.

Normal polymorphonuclear leukocytes (PMNL) in contrast to diabetic PMNL, generated significant amounts of .NO and NO2 when challenged with opsonised zymosan. Diabetic neutrophils, on the other hand, responded either weakly or insignificantly to the same stimulants. However, in resting state the levels of .NO and NO2 were higher in diabetic as compared to normal PMNL. Diabetic serum factor (DSF) provoked a significant generation of .NO and NO2 in normal PMNL, a phenomenon found parallel to the enhancement in cytosolic cathepsin D activity in normal cells on insult with DSF.

Biological Factors↗
PubMed1993

Plausible involvement of a diabetic serum factor in neutrophil membrane pathology.

With a view to determining the role of diabetic serum factor (DSF) in the progression of membrane pathology, time-dependent preincubation effects of DSF on certain membrane-bound enzymes of normal polymorphonuclear leucocytes (PMNL) have been studied. DSF is found to cause significant decrements in the activities of Na+/K+ ATPase, PLC and AcE of PMNL on in vitro incubation for 60 min, while the effect on Ca2+/Mg2+ ATPase appears only on prolonged incubation with an initial hike in activity at 5 min. The implications of these results have been discussed.

Acetylcholinesterase↗
PubMed1992

Stability of the recombinant hepatitis B core antigen.

The recombinant gene for hepatitis B core antigen (HBcAg) was cloned and expressed, and the protein was purified from Escherichia coli cultures. Purified HBcAg was tested for the effects of various physical and chemical agents on its immunoreactivity by a paramagnetic particle-based enzyme immunoassay. Recombinant HBcAg retained its immunoreactivity when heated at 70 degrees C for 60 min but was inactivated at 85 degrees C in 10 min. It was stable between pHs 5 and 10.5 but not at pHs 2 and 13.5. Treatment with sodium dodecyl sulfate (SDS), ethanol, and methanol caused a significant loss in HBcAg reactivity. The proteolytic enzymes papain and bacterial protease (type VIII from Bacillus licheniformis) degraded HBcAg significantly, but trypsin and chymotrypsin did not. The effect of combined SDS and 2-mercaptoethanol on recombinant HBcAg was an immediate loss in immunoreactivity, followed by rapid recovery to about 50% of the initial level. This level was maintained for 24 to 48 h and was followed by an almost total loss of HBcAg in about 120 h.

Base Sequence↗
PubMed1992

Sex variation in ascorbic acid catabolism.

Male and female albino rats of same age and body weight were pair fed with laboratory stock diet and ascorbic acid, dehydroascorbic acid and diketogulonic acid were determined in the liver and urine, while in blood only ascorbic acid was estimated. Male rats had concentration higher of ascorbic acid in liver and urine as compared with females, while there were no significant variations in the contents of dehydroascorbic acid and diketogulonic acid. Hepatic and renal 2, 3-diketoaldonate decarboxylase, and hepatic dehydroascorbatase were also found to be significantly higher in male rats. Similar sex variations were also observed in ascorbic acid catabolism in guinea pigs without any differences in urinary ascorbic acid contents.

Animals↗
PubMed1988

Hepatitis B virus particles contain a polypeptide encoded by the largest open reading frame: a putative reverse transcriptase.

A segment of the largest open reading frame of hepatitis B virus (HBV) was inserted into an open reading frame vector directing the expression in Escherichia coli of a fusion molecule containing 143 HBV-encoded amino acids. The fusion protein was used to generate antiserum which served in immunoblots to identify a polypeptide with a molecular mass of 65 kilodaltons in HBV particles. Because of the small number of molecules in virus particles, unambiguous detection required the development of a highly sensitive immunoblot procedure.

3,3'-Diaminobenzidine↗
PubMed1987

Increased risk for lethal forms of liver disease among HBsAg-positive blood donors in the United States.

We have used a death-record search to define the frequency of lethal outcomes of hepatitis B virus infection among a population of more than 15,000 overtly healthy blood donors found positive in routine HBsAg testing. We have compared the study population with a control group of some 18,000 donors selected on the basis of a negative test result. The index and control groups were observed for periods reflecting a total of 55 and 59 thousand person-years, respectively. Twenty percent of the 134 deaths identified among HBsAg positive donors were in some way liver related, including seven deaths due to hepatitis, seven to cirrhosis and six to hepatoma. In contrast, only one of the 95 deaths in the control population was liver related, and was due to fatty degeneration of the liver. The majority (four) of the hepatoma deaths occurred among blacks, three of whom were less than 35 at the time of death. In contrast, deaths from cirrhosis were all among whites. We conclude that there is significant mortality associated with the HBsAg positive state, even though the affected individuals may be asymptomatic and well enough to give blood at some stage. We estimate the standardised mortality ratio for hepatoma among HBsAg-positive persons in the United States is at least 27, confirming the association observed in other populations. The risk for hepatoma among young, HBsAg positive black males appears to approach that reported for HBsAg positive males in Taiwan. Data on the feasibility of AFP testing for early detection of hepatoma are included and discussed.

Blood Donors↗
PubMed1987

A test for human cytomegalovirus-specific immunoglobulins using a modification of a commercial test kit.

A technique (Ig-EIA) for the detection of CMV-specific IgG, IgM and IgA in human blood is described. Ig-EIA utilizes alkaline phosphatase-labeled goat anti-human IgG, IgM and IgA as a detection probe and CMV antigen-coated solid phase from commercial kits. Ig-EIA is compared to indirect fluorescent assay (IFA) and indirect hemagglutination (IHA) for sensitivity and specificity. On sequential samples of blood from a set of patients, Ig-EIA clearly demonstrated seroconversion in CMV-specific IgG and IgM. A test of 332 blood donors by Ig-EIA showed 177 (53%) had CMV-specific IgG and 17 (5%) had CMV IgM. Only two of the 17 donors with CMV IgM were nonreactive for CMV-IgG. The potential of CMV-IgM as an indicator of CMV infectivity is discussed.

Adult↗
PubMed1987

Immunoglobulin level in donor blood reactive for antibodies to human immunodeficiency virus.

Blood samples from 98 asymptomatic volunteer blood donors, including 55 that were reactive for antibodies to human immunodeficiency virus (HIV) in Western blot (WB) assay, were tested for levels of immunoglobulin G (IgG), IgM, and titer of antibodies to HIV, cytomegalovirus, and herpes simplex virus. Levels of IgG were significantly elevated (P less than or equal to 0.001) in donors with specific anti-HIV reactivity. A total of 69% of donors with anti-HIV had IgG levels of greater than or equal to 12 mg/ml, and 44% had IgG levels of greater than or equal to 14.5 mg/ml. Levels of IgM were not significantly different among WB-reactive and nonreactive donors. The titer of anti-HIV was significantly (P less than 0.02) correlated with IgG levels among donors reactive in the WB assay. Elevation of IgG, however, was not significantly associated with the presence of anticytomegalovirus or anti-herpes simplex virus antibodies. The data show that elevation of IgG may represent an early manifestation of HIV infection before the development of clinical symptoms of acquired immunodeficiency syndrome.

Adolescent↗
PubMed1986

Location of the sites of reaction of N-ethylmaleimide in papain and chymotryptic fragments of the gizzard myosin heavy chain.

The thiol of the gizzard myosin heavy chain, which reacts most rapidly with N-ethylmaleimide (MalNEt), has been located in the subfragment 2 region of myosin rod by fragmentation of [14C]-MalNEt-labeled myosin with papain and chymotrypsin. MalNEt reacts more slowly with thiols present in the 70- and 25-kilodalton (kDa) papain fragments of subfragment 1. The reaction of MalNEt with thiols present in these regions is increased on addition of ATP by factors of 2 and 10, respectively, when myosin is modified in 0.45 M NaCl where it is present in the extended, 6S conformation. The rate of increase of Mg2+-activated adenosinetriphosphatase (ATPase) activity, which reflects the loss of ability of myosin to assume the folded, 10S conformation, and the rate of loss of K+-EDTA-activated activity produced by MalNEt are both accelerated 5- to 10-fold on addition of ATP. The rates at which ATPase activities change agree closely to the reaction rates of MalNEt with the 25-kDa region of subfragment 1; therefore, the changes in these activities can be attributed to modification of a thiol of the 25-kDa segment. An increase in actin-activated ATPase activity produced by reaction of myosin with MalNEt in 0.45 M NaCl is accelerated by ATP by a factor of at least 4. Reaction with [14C]MalNEt in the presence of MgATP and 0.2 M NaCl, where myosin is in the 10S form, inhibits the incorporation of radioactive MalNEt into the 25-kDa papain fragment of subfragment 1. It also prevents the increase in actin-activated ATPase activity and preserves the ability of myosin to assume the 10S form.

Adenosine Triphosphatases↗
PubMed1986

Ca2+ dependence of the ATPase activity of phosphorylated smooth muscle myosin: effects of tropomyosin and actin.

Calcium ions produce a 3-4-fold stimulation of the actin-activated ATPase activities of phosphorylated myosin from bovine pulmonary artery or chicken gizzard at 37 degrees C and at physiological ionic strengths, 0.12-0.16 M. Actins from either chicken gizzard or rabbit skeletal muscle stimulate the activity of phosphorylated myosin in a Ca2+-dependent manner, indicating that the Ca2+ sensitivity involves myosin or a protein associated with it. Partial loss of Ca2+ sensitivity upon treatment of phosphorylated gizzard myosin with low concentrations of chymotrypsin and the lack of any change on similar treatment of actin supports the above conclusion. Although both actins enhance ATPase activity, activation by gizzard actin exhibits Ca2+ dependence at higher temperatures or lower ionic strengths than does activation by skeletal muscle actin. The Ca2+ dependence of the activity of phosphorylated heavy meromyosin is about half that of myosin and is affected differently by temperature, ionic strength and Mg2+, being independent of temperature and optimal at lower concentrations of NaCl. Raising the concentration of Mg2+ above 2-3 mM inhibits the activity of heavy meromyosin but stimulates that of myosin, indicating that Mg2+ and Ca2+ activate myosin at different binding sites.

Actins↗
PubMed1986

Hepatitis B virus polypeptide X: expression in Escherichia coli and identification of specific antibodies in sera from hepatitis B virus-infected humans.

Sequence analysis of the hepatitis B virus (HBV) genome revealed the presence of an open reading frame (ORF X) which has the potential to encode a 154-amino acid polypeptide. A fusion protein containing 145 of the amino acids encoded by ORF X and 8 amino acids of beta-galactosidase was expressed and characterized in bacterial extracts. Immunoprecipitations with the ORF X fusion protein as a radioactively labeled antigen were performed to screen sera of humans infected with HBV for the presence of antibodies against ORF X-encoded determinants (anti-X). Such antibodies were identified in 9 samples from a set of 26 sera characterized as positive for HBV surface antigen but were not found in 16 normal human sera. The data reported here demonstrate that sera from some patients with markers of HBV infection contain antibodies directed against the polypeptide encoded by ORF X. As such, these findings represent evidence that ORF X constitutes a gene, or a portion of a gene, which is expressed during HBV infection. Although there does not appear to be a direct relationship between anti-X and any individual markers of HBV infection, our data suggest that anti-X is more prevalent in HBV-positive sera containing antibodies to HBe3 antigen (anti-HBe3).

Base Sequence↗