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Biomedical subjects

M Krishnan

Publications and source records attributed to M Krishnan.

At least 19 recordsLinked to original sources
PubMed1996

Aspergillus fumigatus peptides differentially express Th1 and Th2 cytokines.

Relevant allergens from Aspergillus fumigatus associated with allergic bronchopulmonary aspergillosis (ABPA) have been cloned and expressed. The pathogenesis of ABPA probably depends on specific cytokines and immunoglobulins secreted by lymphocytes on stimulation with different epitopes of those allergens. In the present study, we synthesized peptides of 12-16 amino acids from the sequence of Asp fI and compared their immunological responses in four mice strains (BALB/c, C57BL/6, AKR, and CBA). Of the five peptides studied for their cytokine profile, one showed a clear Th1, whereas another showed a Th2 response. The remaining three peptides varied in their immunoreactivity. The results suggest that a number of epitopes of diverse activities are present in individual molecules and may be involved in the pathogenesis of ABPA through differential cytokine secretions.

Allergens↗
PubMed1996

Pharmacokinetics of erythropoietin following single-dose subcutaneous administration in preterm infants.

The pharmacokinetics of recombinant human erythropoietin was studied in 12 very low birth weight preterm infants < 32 weeks of gestation after subcutaneous administration of 300 IU/kg at a postconceptional age of 34 (32-37) weeks and a weight of 1,505 (1330-1,740)g (median and range). The administration of recombinant human erythropoietin produced a rapid increase in serum erythropoietin levels with a peak level of 362.8 mIU/ml at 8.9 h. The area under the curve was 8,177.5 (4,597.1-15,453.0) mIU/ml/h, the absorption half-life was 5.5 (1.6-6.6) h, the elimination half-life was 7.9 (5.6-19.4) h, and the residence time was 19.6 (5.1-32.6) h (all values reflect median and range). There was no significant correlation between absorption and elimination half-life of erythropoietin and birth weight, gestational age, sex, and age and weight of the infants at the time of administration of erythropoietin. Based on absorption and elimination kinetics, the dosing interval for subcutaneous administration must not be < 48 h.

Absorption↗
PubMed1995

Allele frequency distribution for the variable number of tandem repeat locus D10S28 in Tamil Nadu (south India) population.

Allele frequencies were determined in unrelated individuals of Tamil speaking population from the Madras City (Tamil Nadu, South India) area for the polymorphic DNA locus D10S28 using the probe TBQ7. Membranes hybridized with the probe YNH24 were subjected to deprobing and were subsequently hybridized with random priming - labeled, purified inserts of TBQ7. The sizes of the fragments were grouped to 100 bp as well as to arbitrary fixed bins (Federal Bureau of Investigation / Royal Canadian Mounted Police). There were 14 bins in the latter with the most common bin being 11 (1789-1924 bp) with a frequency of 9.8%. We observed a heterozygosity of 92% comparable to Caucasian populations. The data presented here can be used as the basis for utilizing this variable number of tandem repeats (TNTR) DNA marker for paternity determinations and forensic investigations.

Alleles↗
PubMed1994

A study on children's condition thalassemia using neutron activation analysis and other techniques.

In this study, 50 thalassemia patients were tested using dual-energy X-ray absorptiometry (DEXA) and in vivo neutron activation analysis (IVNAA) to determine their bone mineral status. Both techniques were suitable for this purpose. Lower age was found to correspond to lower liver iron content and higher bone mineral content in the normal range. Patients undergoing treatment with transfusion had higher bone mineral content. Osteopenic patients had higher hepatic iron content than those with normal bone status. In the case of DEXA, bone mineral content (BMC) divided by height cubed was found to be a better indicator of bone mineral status than the BMD usually given. Liver density as determined by DEXA correlates well with hepatic iron.

Absorptiometry, Photon↗
PubMed1992

Peribulbar anesthesia for primary vitreoretinal surgery.

We prospectively studied the efficacy of peribulbar anesthesia in 76 consecutive patients who underwent vitreoretinal surgery. The mean duration of anesthesia was 124.74 +/- 50.17 minutes, and the mean duration of akinesia, 151.5 +/- 54.45 minutes. Adequate anesthesia and akinesia, independent of the duration of surgery, was obtained in 26 of 33 (78.8%) patients who underwent vitrectomy; 9 of 32 (28.1%) who underwent scleral buckling; and 2 of 11 (18.2%) who underwent vitrectomy combined with scleral buckling. In all, topical and systemic supplementation of drugs for inadequate anesthesia or akinesia allowed 32 of the 33 (97%) vitrectomies, 30 of the 32 (94%) scleral buckling procedures, and all 11 of the combined surgeries to be completed as planned. Three (4%) patients vomited, moved, or were restless, resulting in an operative complication or postponement of surgery. Fifty-eight (76%) said they would desire similar anesthesia if subsequent surgery was needed in the same or fellow eye. We conclude that peribulbar anesthesia should be considered primarily for patients requiring vitreous surgery alone, and as an alternative for patients requiring scleral buckling or combined surgery for whom general anesthesia is contraindicated.

Adult↗
PubMed1991

Transport of nonmetabolizable opines by Agrobacterium tumefaciens.

We have examined the uptake of [14C]octopine and [14C]nopaline by Agrobacterium tumefaciens strains containing the C58 chromosomal background in medium suitable for the induction of vir genes. All strains tested could transport both of these opines, regardless of the presence or type of Ti plasmid (octopine or nopaline) present in the bacterium. The transport of these opines required active cellular metabolism. Nonradioactive octopine, nopaline, and arginine competed effectively with [14C]octopine and [14C]nopaline for transport into A. tumefaciens A136, suggesting that the transport of these opines occurs via an arginine transport pathway not encoded by the Ti plasmid.

Arginine↗
PubMed1991

Fibrinogen acts as a bridging molecule in the adherence of Staphylococcus aureus to cultured human endothelial cells.

The propensity of Staphylococcus aureus to cause acute endovascular infections during transient bacteremia is poorly understood. To examine the events leading to the attachment of staphylococci to endothelium, adherence assays were developed to study the role of blood factors in the mediation of staphylococcal adherence to cultured human umbilical vein endothelium in vitro. Results indicate that the preferential attachment of S. aureus to endothelial cells is mediated by fibrinogen adsorbed from plasma onto the endothelial surface. The binding is apparently specific because it could be blocked by goat anti-human fibrinogen antibody in a dose-dependent fashion while nonimmune goat IgG, mouse MAb against AG-1 (a platelet antigen found on the endothelial cell surface), nonspecific mouse MAb and rabbit antibodies to human vitronectin and fibronectin were not inhibitory. Our data also indicate that fibrinogen is a necessary but not the only blood constituent in the mediation of binding of S. aureus to endothelium. This was supported by the finding that fibrinogen alone, at a concentration equivalent to that in plasma, did not potentiate staphylococcal adherence as much as plasma while afibrinogenemic plasma reconstituted with fibrinogen did. Because fibrinogen is known to bind to endothelial cells, our data is consistent with the hypothesis that fibrinogen and additional plasma factor(s), possibly activated during inflammation, promote staphylococcal adherence to endothelium. In addition, the role of the fibrinogen binding receptor of S. aureus as an adherence factor to native endothelium is also suggested.

Antibodies↗
PubMed1990

Drying acrylamide slab gels for fluorography without using gel drier and vacuum pump.

A method for drying acrylamide slab gels for fluorography without using a gel drier and a vacuum pump is described. The method involves the use of inexpensive acrylic frames, cellophane, and plastic supplies. The fluorographs obtained from gels dried by this method are comparable to those obtained using a gel drier and a vacuum pump. Several gels can be dried by this method simultaneously at room temperature. The method is less time consuming and is economical and practically crack free.

Acrylamide↗
PubMed1990

Ampicillin pharmacokinetics in Indian geriatric subjects.

Ampicillin elimination was studied in geriatric and younger subjects, 10 in each group. The geriatric subjects had higher serum concentration and elimination half-life of the drug. The plasma clearance and urinary excretion of the drug were significantly reduced in them when compared to younger subjects. Urinary excretion of the drug had significant correlation with creatinine clearance of the subjects.

Adult↗
PubMed1989

Opines stimulate induction of the vir genes of the Agrobacterium tumefaciens Ti plasmid.

Upon incubation of Agrobacterium tumefaciens A348 with acetosyringone, the vir genes encoded by the Ti (tumor-inducing) plasmid are induced. The addition of certain opines, including octopine, nopaline, leucinopine, and succinamopine, enhanced this induction 2- to 10-fold. The compounds mannopine, acetopine, arginine, pyruvate, and leucine did not stimulate the induction of the vir genes to such an extent. The enhancement of vir gene induction by opines depended on acetosyringone and the genes virA and virG. Opines stimulated the activity of the vir genes, the double-stranded cleavage of the T (transferred)-DNA at the border repeat sequences, and the production of T-strands by the bacterium. The transformation efficiency of cotton shoot tips was markedly increased by the addition of acetosyringone and nopaline at the time of infection.

Acetophenones↗
PubMed1989

Differential effect of type I and type II diabetes mellitus on serum ampicillin levels.

Ampicillin elimination was studied in 10 poorly controlled, 6 well controlled type I and 14 poorly controlled type II diabetic patients. Two groups of age-matched healthy volunteers served as controls. After oral administration of ampicillin (500 mg), the poorly controlled type I diabetics had significantly lower serum concentration of the drug when compared to their corresponding healthy controls. The elimination half-life (t1/2) remained unaltered. Their creatinine clearance rate and urinary excretion of the drug were significantly reduced. There was no difference in these parameters between well controlled diabetics and healthy volunteers. The bioavailability data calculated from the urinary recovery of the drug, after oral and i.v. administration, suggested reduced oral absorption in poorly controlled type I diabetic patients. Ampicillin kinetics data of poorly controlled type II diabetic patients were not significantly different from that of the control group. Serum ampicillin levels and urinary excretion of the drug were similar in these groups. It is concluded that serum ampicillin level may be lower in poorly controlled type I diabetics which may be due to reduced absorption of the orally administered drug.

Adult↗
PubMed1989

Effect of type II diabetes mellitus on theophylline elimination.

Theophylline elimination was studied in poorly-controlled and well-controlled type II diabetic patients, seven in each group. Eight healthy volunteers served as a control group. After a single oral dose of theophylline (200 mg) the drug concentration was measured in plasma, collected at different time intervals, using a high pressure liquid chromatography method. The poorly-controlled diabetics had significantly longer elimination half-life (t1/2) due to increased apparent volume of distribution (V) of the drug when compared to well-controlled diabetics. Their clearance rate (Cl) remained unaltered. There was no significant difference in these parameters between healthy volunteers and diabetic patients, although poorly-controlled diabetics had a tendency for higher t1/2 and V. It is concluded that theophylline clearance is unaltered in type II diabetic patients.

Adult↗
PubMed1988

Heat shock response of the chloroplast genome in Vigna sinensis.

The light-dependent protein synthesis occurring in chloroplasts isolated from the leaves of 7-day-old Vigna sinensis responded to heat shock with the induction of a set of four heat shock proteins (HSPs). The synthesis of these four HSPs at the elevated temperature was transcriptionally regulated, and all of them were found to be thylakoid membrane-bound. The synthesis of these chloroplast-coded HSPs was also observed in etioplasts during protein synthesis at the elevated temperatures with the exogenously added ATP. The in vivo induction of these plastid-coded HSPs was observed only in the leaves subjected to gradual increase in temperature but not in leaves subjected to rapid heat shock. Further, the in vitro synthesis of these plastid-coded HSPs was seen only in chloroplasts isolated from the control or from leaves subjected to gradual increase in temperature and not in chloroplasts isolated from leaves subjected to rapid heat shock. Taken together these observations suggest that in V. sinensis, the plastid genome contains a definite heat shock response and the in vivo expression of this response corresponds to the gradual rise in temperature normally occurring under field conditions.

Chloroplasts↗
PubMed1988

Antibodies to liver/kidney microsome1 in chronic active hepatitis recognize specific forms of hepatic cytochrome P-450.

Anti-liver/kidney microsome1-positive sera from children with chronic active hepatitis were studied in an effort to identify the microsomal antigens selected during induction and progression of this autoimmune disease. Immunoblot analysis of sodium dodecyl sulfate gel-resolved microsomal proteins from human and rat liver using anti-liver/kidney microsome1-positive sera revealed a single polypeptide of 48 kilodaltons (human microsomes) or 50 kilodaltons (rat microsomes). Levels of the 50-kilodalton rat microsomal polypeptide were suppressed in vivo by several drugs known to modulate expression of individual forms (enzymes) of hepatic cytochrome P-450, with the largest decrease effected by phenobarbital. Dot blot analysis using a panel of 10 electrophoretically homogeneous rat liver cytochrome P-450 forms under nondenaturing conditions established that the two methylcholanthrene-inducible forms, P-450 BNF-B and P-450 ISF-G (P-450 gene subfamily IA), are selectively recognized by the anti-liver/kidney microsome1 antibodies. These findings demonstrate that sera associated with autoimmune (anti-liver/kidney microsome1) chronic active hepatitis are specifically reactive with select rat hepatic P-450 forms and suggest that these autoantibodies may be principally directed against one or more constitutive forms of the corresponding human liver cytochromes.

Autoantibodies↗
PubMed1986

An efficient and prolonged in vitro translational system from isolated cucumber etioplasts.

Etioplasts were isolated from dark grown cucumber cotyledons pretreated with kinetin and gibberellic acid. When incubated in a cofactor enriched medium these etioplasts incorporated [35S] methionine into a hot trichloroacetic acid-insoluble fraction; this incorporation was linear for 8 h of incubation and was inhibited by chloramphenicol but not by cycloheximide. Over the same time period, the etioplasts showed continued linear synthesis of the chlorophyll precursors protochlorophyllide, Mg-protoporphyrin and protoporphyrin IX. Analysis of products of in vitro protein synthesis by etioplasts and cotyledons showed the thylakoid membrane polypeptide profiles to be identical. Continued incorporation of [35S] methionine into the large subunit of ribulose bisphosphate carboxylase/oxygenase (RuBisCO) for 8 h has been confirmed further by immunoprecipitation with anti-spinach RuBisCO. This competent in vitro translation system should be useful for future studies of chloroplast protein synthesis and gene expression.

Amino Acids↗
PubMed1984

Radioisotopic evidence for the polypeptides associated with photosystem II.

Direct radioisotopic evidence for the polypeptides associated with oxygen evolution in a non-destructive approach by comparing the polypeptides of photosystem II (PS II) particles in etioplasts that lack O2 evolution with that of chloroplasts that exhibit high rates of oxygen evolution is reported. Polypeptide analysis by coomassie blue staining revealed that 32, 23 and 15 kDa proteins were absent in etioplast particles but developed in chloroplast PS II particles after illumination. However, a strikingly different picture was obtained when labelled polypeptides were analyzed from the fluorograph. While the new proteins identified by coomassie blue staining were also labelled, intensely labelled major polypeptides of molecular range 40, 41, 43 kD and minor polypeptides of molecular range 47, 48, 51 kD were observed in chloroplast PS II particles but not in etioplasts or etioplast particles; these labelled polypeptides were so prominent that they could be identified even in thylakoid membranes.

Chlorophyll↗