Search PubMed⌕ Search

Biomedical subjects

N Qureshi

Publications and source records attributed to N Qureshi.

106 records · Page 6Linked to original sources
PubMed1978

Characterization of the purified components of a new homologous series of alpha-mycolic acids from Mycobacterium tuberculosis H37Ra.

Homologous series of alpha-mycolic acids from Mycobacterium tuberculosis H37Ra were separated according to size as their p-bromophenacyl ester by bonded C18 reverse-phase, high performance liquid chromatography. Mass spectrometry of the prominent components separated by high performance liquid chromatography gave relatively simple spectra and showed a series of components differing by 28 atomic mass units. A total of different structures were identified. The structures were established as follow: (formula see text) where a = 17, 18, 19; b = 10; c = 15, 17, 19, 21; and d = 21, 23. The C76 and C78 acids contained some C24 alpha-branch acid (d - 21), whereas the C80 and C82 acids contained some a = 19 acids. Several new homologous series were revealed.

Chromatography, High Pressure Liquid↗
PubMed1978

Isolation and characterization of the monounsaturated long chain fatty acids of Mycobacterium tuberculosis.

The positions of double bond in the monounsaturated C15-C32 fatty acids of Mycobacterium tuberculosis H37Ra were established by gas chromatography/mass spectrometry of the ozonized esters and their pyrrolidide derivatives. The monounsaturated C15-C21 fatty acids had the double bond primarily at the delta 9 position while the monounsaturated longer chain fatty acids (C22-C32) had the double bond in several positions. Many of the latter acids, especially the odd-numbered series, were very complex isomeric mixtures. Quantitation showed the most abundant even-numbered long chain fatty acid isomers to be as follows: C22, delta 4; C24, delta 5; C26, delta 7 and delta 9; C28, delta 9; C30, delta 11 and delta 13; C32, delta 13 and delta 15.

Chromatography, Gas↗
PubMed1977

Studies on the significance of hair root protein and DNA in protein-calorie malnutrition.

Hair root protein and DNA, serum nonessential amino acid/essential amino acid ratio, serum total protein, albumin, globulin and albumin/globulin ratio were estimated in children suffering from portein-calorie malnutrition (PCM) and the values compared to those obtained from healthy children. The data were presented in two ways: 1) classified as early malnutrition, marasmus, marasmic kwashiorkor, or kwasiorkor and the parameters compared 2) all the malnourished children were divided into four groups on the basis of percentage of body weight for age and the parameters compared. There was a progressive decrease in the content of hair root DNA and protein with the severity of PCM with these values decreasing to less than half of the normal values. In all types of PCM the serum albumin decreased significantly and the globulin increased while the total protein was altered only in the more severe stages. Differences in the serum consituents between groups were more pronounced when classified clinically than when grouped as percentage of normal body weight. Since hair root changes are progressive and of greater magnitude than those in the serum, hair root DNA and proteins might be useful chemical criteria in detectinc various stages of PCM, and further to help understand the pathogenesis of the condition.

Amino Acids↗
PubMed1976

Purification of beta-hydroxy-beta-methylglutaryl-coenzyme A reductase from yeast.

Beta-Hydroxy-beta-methylglutaryl-coenzyme A reductase of yeast has been solubilized by two different methods and then purified approximately 5000-fold. The purified enzyme shows a single precipitin band on immunodiffusion, and it moves as a single band of protein and enzyme activity on gel filtration and diethylaminoethylcellulose column chromatography. It also shows one major band on polyacrylamide gel electrophoresis. The specific activity of the pure enzyme is 18 000 to 22 000 nmol of reduced nicotinamide adenine dinucleotide phosphate oxidized per min per mg of protein. The molecular weights of the enzyme, estimated by gel filtration, and the subunits, determined by sodium dodecyl sulfate polyacrylamide gel electrophoresis, are 2.6 X 10(5) and 6.0 X 10(4), respectively.

Alcohol Oxidoreductases↗
PubMed1976

Kinetic analysis of the individual reductive steps catalyzed by beta-hydroxy-beta-methylglutaryl-coenzyme A reductase obtained from yeast.

The mechanism of action of yeast beta-hydroxy-beta-methylglutaryl-coenzyme A reductase has been investigated through kinetic studies on the oxidation of mevaldate by nicotinamide adeninine dinucleotide phosphate (NADP) in the presence of coenzyme A (CoA) and on the reduction of mevaldate by reduced NADP (NADPH) in the absence of presence of CoA or acetyl-CoA. NADP and mevalonate were also used as product inhibitors of the reduction of mevaldate. In the reduction of mevaldate to mevalonate, coenzyme A and acetyl-CoA decreased the Km for mevaldate 30- and 3-fold, respectively. Both compounds increased the Vmax 1.5-fold. These results suggest that CoA is an allosteric activator for the second reductive step and that it acts by enhancing the binding of mevaldate. The intersecting patterns obtained from initial velocities and the patterns produced by product inhibitions suggest the following features of the mechanism. The binding of substrates and release of products proceeds sequentially in both reductive steps, and is ordered throughout or random with respect to the binding of the beta-hydroxy-beta-methylglutaryl-coenzymeA and the first NADPH. The binding of NADPH enhances the binding of the beta-hydroxy-beta-methylglutaryl portion of the CoA ester and the binding of free mevaldate, whereas the binding of NADP leads to an increased affinity of the enzyme for the hemithioacetal (of mevaldate and CoA) and for mevalonate. Thus, the replacement of NADP by NADPH after the first reductive step promotes the conversion of the hemithioacetal to the free carbonyl form, which is then rapidly reduced. The products, CoA and mevalonic acid, of the second reductive step leave the enzyme before the release of the second NADP. This release of the last product is probably the rate-limiting step for the overall process.

Alcohol Oxidoreductases↗
PubMed1973

Occurrence of the enzymes effecting the conversion of acetyl CoA to squalene in homogenates of hog aorta.

Homogenates and subcellular fractions of the intimamedia of hog aorta have been prepared and examined for the presence of the enzymes catalyzing the conversion of acetyl CoA to squalene. Enzyme activities effecting the conversion of acetyl CoA to 3-hydroxy-3-methylglutarate (HMG); HMG CoA to mevalonic acid; mevalonic acid to 5-phosphomevalonic acid, 5-pyrophosphomevalonic acid, and isopentenyl pyrophosphate; isopentenyl pyrophosphate to farnesyl pyrophosphate; and farnesyl pyrophosphate to squalene have been demonstrated in these homogenates. The overall conversion of mevalonate to squalene has also been demonstrated with recombined fractions of hog aorta homogenates. Data are also presented that suggest that phosphatases present in the crude homogenates act to cleave farnesyl pyrophosphate to farnesol, and phospho- and pyrophosphomevalonate to mevalonate.

Acetyl Coenzyme A↗
PubMedDate not supplied

Effects of single and multiple courses of antenatal glucocorticoids in preterm newborns less than 30 weeks' gestation.

BACKGROUND: We compared outcomes between neonates receiving either single course, multiple courses, or no antenatal glucocorticoid exposure. METHODS: We retrospectively identified neonates whose mothers received a single course (SIN) of dexamethasone, multiple (2-3) weekly courses (MULT), or no (NO) glucocorticoids. Multiple gestations and infants with chromosomal abnormalities or not receiving a full course of antenatal dexamethasone were excluded from the study. The incidences of the following outcomes were examined: respiratory distress syndrome (RDS), Grades III or IV intraventricular hemorrhage (IVH), bronchopulmonary dysplasia (BPD), necrotizing enterocolitis (NEC), retinopathy of prematurity (ROP), sepsis, and in-hospital death. Means were compared with analysis of variance and outcome variable frequencies with chi-square test. RESULTS: A total of 147 infants were included in the analysis. There were no differences in the gestational age or growth parameters among the groups. As anticipated, infants exposed to antenatal glucocorticoids had a significantly lower incidence of morbidities (BPD, NEC, and IVH) than the unexposed infants. There were no differences in the incidence of RDS, IVH, BPD, NEC, ROP, PDA, sepsis, or death between the SIN and MULT groups. CONCLUSION: A single course of antenatal glucocorticoid therapy is associated with improved neonatal outcomes in infants less than 30 weeks' gestation. Multiple courses were not shown to confer additional benefits, but further investigation is required to definitively address the need for weekly treatment.

Bronchopulmonary Dysplasia↗
PubMedDate not supplied

Preparation and characterization of biologically active 6'-O-(6-aminocaproyl)-4'-O-monophosphoryl lipid A and its conjugated derivative.

N-tert-butyloxycarbonyl (t-Boc) protected 6-aminocaproic (Cap) anhydride was reacted with unprotected hexaacyl-4'-O-monophosphoryl lipid A (MLA) obtained from the lipopolysaccharide of Escherichia coli J5 to yield t-Boc-Cap-MLA. After a column purification step, the t-Boc group was removed by incubating the sample at low temperature in the presence of acid to yield Cap-MLA. This product was analyzed by californium plasma desorption mass spectrometry (PDMS). Purified t-Boc-Cap-MLA was further fractionated by reverse-phase high-performance liquid chromatography as its methyl ester and characterized by laser desorption mass spectrometry, PDMS, and proton nuclear magnetic resonance spectroscopy. These analyses revealed that the Cap group was selectively introduced into the 6'-position of MLA. To demonstrate that Cap-MLA can be conjugated to other compounds, it was reacted with biotin-Cap N-hydroxysuccinimide ester to yield biotin-(Cap)2-MLA. Analysis of this product by PDMS confirmed its expected molecular weight of 2171 and showed the presence of fragments containing the biotin and Cap groups. Monoclonal antibodies and streptavidin were used to show the presence of both lipid A and biotin in this conjugated product. These two novel lipid A derivatives were then tested for their bioactivities. Although both Cap-MLA and biotin-(Cap)2-MLA showed mitogenic activity using murine splenocytes, they were about 4-8 times less active than MLA at 20 micrograms/mL or less and only one-half as active at 100 micrograms/mL.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMedDate not supplied

Production of acetone butanol ethanol (ABE) by a hyper-producing mutant strain of Clostridium beijerinckii BA101 and recovery by pervaporation.

A silicone membrane was used to study butanol separation from model butanol solutions and fermentation broth. Depending upon the butanol feed concentration in the model solution and pervaporation conditions, butanol selectivities of 20.88-68.32 and flux values of 158.7-215.4 g m(-)(2) h(-)(1) were achieved. Higher flux values (400 g m(-)(2) h(-)(1)) were obtained at higher butanol concentrations using air as sweep gas. In an integrated process of butanol fermentation-recovery, solvent productivities were improved to 200% of the control batch fermentation productivities. In a batch reactor the hyper-butanol-producing mutant strain C. beijerinckii BA101 utilized 57.3 g/L glucose and produced 24.2 g/L total solvents, while in the integrated process it produced 51.5 g/L (culture volume) total solvents. Concentrated glucose medium was also fermented. The C. beijerinckii BA101 mutant strain was not negatively affected by the pervaporative conditions. In the integrated experiment, acids were not produced. With the active fermentation broth, butanol selectivity was reduced by a factor of 2-3. However, the membrane flux was not affected by the active fermentation broth. The butanol permeate concentration ranged from 26.4 to 95.4 g/L, depending upon butanol concentration in the fermentation broth. Since the permeate of most membranes contains acetone, butanol, and ethanol (and small concentrations of acids), it is suggested that distillation be used for further purification.

Acetone↗
PubMedDate not supplied

Consanguinity and genetic morbidity in a British primary care setting: a pilot study with trained linkworkers.

OBJECTIVES: To assess the feasibility of detecting consanguineous relationships and significant genetic morbidity through screening pedigrees administered by a primary care trained linkworker. SUBJECTS AND METHODS: A case-controlled crossover study with pedigree recording by both genetic nurse specialists and a primary care worker. From 1012 records of British Pakistani patients registered with an inner city practice, 14 women, identified as having increased genetic risk, were recruited (Group 1). A further 14 age- and parity-matched women, with no indication of genetic morbidity in their General Practice records (Group 2), were also recruited. RESULTS: Valuable genetic information, not recorded in General Practice records, were ascertained through the screening pedigrees, in four members of Group 1 (29%) and six members of Group 2 (43%). There was poor agreement between the coefficients of inbreeding recorded from pedigrees prepared by the primary care worker and genetic nurse specialists (Kappa = 0.157; 95% CI 0.028-0.286). CONCLUSION: Pedigrees can be utilized as a General Practice screening tool to detect relevant genetic morbidity, not ascertained in General Practice records. The process is enhanced when a primary care worker, from the same culture as the volunteers, collects information using the patients' mother tongue.

Adult↗
PubMedDate not supplied

Separation and characterization of toxic and nontoxic forms of lipid A.

Highly purified and well-characterized samples of precursors and derivatives of bacterial lipopolysaccharides (LPS) were used to study the relationship between the chemical structure of lipid A and its toxicity. These samples included lipids X and Y (monosaccharide precursors of lipid A) from Escherchia coli MN7; incomplete lipid A (a disaccharide precursor of lipid A) from Salmonella typhimurium i50; and monophosphoryl lipid A, TLC-3 (a derivative of LPS), from S. typhimurium G30/C21. In addition, a diphosphoryl lipid A, TLC-3, was prepared from LPS of S. typhimurium G30/C21 and characterized by positive fast atom bombardment mass spectrometry. The diphosphoryl lipid A, TLC-3 fraction, was determined to be very toxic by the chick embryo lethal-dose test (CELD50 = 0.0064 microgram). Lipids X and Y, incomplete lipid A, and monophosphoryl lipid A (TLC-3), were all nontoxic (CELD50 greater than 10 micrograms). These results suggest a multiple structural requirement for toxicity of lipid A. Toxic lipid A must contain all of the following components: a glucosamine disaccharide, a sugar-1-phosphate, and normal fatty acid(s).

Animals↗
PubMedDate not supplied

Lipid A and immunotherapy.

Endotoxin isolated from Re mutants of Salmonella typhimurium or Salmonella minnesota and consisting only of 3-deoxy-D-mannooctulosonic acid (KDO) and lipid A synergistically enhances the ability of mycobacterial cell wall skeleton (CWS) to regress transplantable, line-10 tumor (hepatocellular carcinoma) in syngeneic guinea pigs. Tumor regression is rapid, and systemic tumor immunity concomitantly develops when as little as 50 micrograms of each of these two components is combined and injected intralesionally. Selective removal of KDO from endotoxin yields diphosphoryl lipid A, which retains its toxic properties. Subsequent selective removal of the phosphate moiety at the reducing end of the diphosphoryl lipid A molecule yields nontoxic, monophosphoryl lipid A (determined by lethality for chick embryos). Like the parent endotoxin or toxic diphosphoryl lipid A, monophosphoryl lipid A retains the ability to synergistically enhance the antitumor activity of mycobacterial CWS adjuvant. Both di- and monophosphoryl lipid A contain mixtures of a series of structural analogs. They can be separated chromatographically into single components that differ in number, type, and position of ester-linked fatty acids. Comparison of chromatographic fractions reveals that components of toxic and nontoxic lipid A can be paired according to structure. Each component of the pair has the same molecular structure, with the exception of an additional phosphate group in the toxic component. The toxicity of "lipid A's" liberated from endotoxin by acid hydrolysis appears to be determined by the proportion of di- and monophosphoryl lipid A in the hydrolysis mixture. Structural analogs of monophosphoryl lipid A, which differ in degree of O-acylation and type and distribution of fatty acids, have comparable antitumor activity.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetylmuramyl-Alanyl-Isoglutamine↗
PubMedDate not supplied

Thoracentesis in clinical practice.

Thoracentesis is a commonly performed procedure indicated for diagnostic and therapeutic purposes. Removal of pleural fluid should be performed by experienced operators and, when attempted by physicians-in-training, close supervision by credentialed individuals is necessary. Diagnostic thoracentesis is most valuable in separating exudates from transudates. Analysis of the exudative fluid has the highest yield when infection and malignancy is likely. Pneumothorax is the most common major complication and can be minimized by the use of small-gauge needles (no. 21 or no. 22) when a small amount of fluid is removed (35 to 50 ml). Patients who may pose difficulties (e.g., those receiving ventilator support) appear to have no greater morbidity with thoracentesis than those patients not ventilator dependent. Ultrasound may be of value to decrease morbidity when small or loculated volumes of fluid are present. Therapeutic thoracentesis offers relief of symptoms of dyspnea, but caution is particularly needed because large needles and large volumes of fluid removed may increase morbidity.

Biopsy↗