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Biomedical subjects

F Ahmad

Publications and source records attributed to F Ahmad.

At least 127 records · Page 7Linked to original sources
PubMed1989

The denatured states of ribonuclease-A: mechanism of denaturation by lithium chloride.

Denaturation of ribonuclease-A by lithium chloride has been studied using difference spectral, circular dichroic and viscometric measurements. The difference spectral results were interpreted in the light of our observations that the solvent effect of the denaturant on the tyrosyl residue is non-linear. It has been observed that (1) the lithium chloride-denatured protein contains 3% alpha-helix and 18% beta-structure, and (2) only two of the three buried tyrosyl residues are normalized in the denatured protein.

Chlorides↗
PubMed1987

Analysis of lipids containing hydroxy fatty acids.

Lipids containing hydroxy fatty acids or hydroxyacyl moieties are acetylated with [1-14C]acetic anhydride or [3H]acetic anhydride, and the content of hydroxy fatty acids or hydroxyacyl moieties is estimated from the specific radioactivity of the acetylated products with respect to that of radioactive standards, such as radioacetylated ricinoleic acid or triricinoleoylglycerol. Mixtures of triacylglycerols containing one, two and three hydroxyl groups per molecule are derivatized in a similar manner, and the resulting acetates are fractionated by thin layer chromatography according to the number of acetate groups per molecule. The relative proportion of each type of triacylglycerols in the mixture is estimated from the distribution of radioactivity in the various fractions. Applications of these techniques are demonstrated by the analysis of several seed lipids.

Hydroxy Acids↗
PubMed1987

Characterisation of Branhamella catarrhalis and differentiation from Neisseria species in a diagnostic laboratory.

To distinguish Branhamella catarrhalis from Neisseria species a study of 140 strains was made on simple laboratory media, with particular reference to deoxyribonuclease (DNase) production, superoxol reaction, and growth characteristics. All 97 clinical isolates of B catarrhalis (58 of which were beta-lactamase positive) and eight strains of B catarrhalis from the National Collection of Type Cultures were DNase positive and superoxol positive. None grew on modified New York City medium, modified Thayer Martin medium, MacConkey agar, crystal violet blood agar, nor under anaerobic conditions. Of the 16 different non-pathogenic Neisseria species tested, all were DNase negative, eight (50%) were superoxol reaction negative, and 13 (81%) grew on crystal violet blood agar. Using simple laboratory media, DNase, and superoxol tests, it was possible to identify B catarrhalis and to distingish it from pathogenic and non-pathogenic Neisseria species.

Deoxyribonucleases↗
PubMed1986

Rat liver pyruvate carboxylase. Purification, detection and quantification of apo and holo forms by immuno-blotting and by an enzyme-linked immunosorbent assay.

A simple scheme for the purification of pyruvate carboxylase from rat liver mitochondria is described. It is rapid and provides high-purity pyruvate carboxylase with excellent yield and reproducibility. The final enzyme preparations appear to be homogeneous by the following criteria: elution behaviour on molecular-sizing matrix, SDS/polyacrylamide-gel electrophoresis, Ouchterlony double-diffusion analysis and Western blotting. Detection and quantification of nanogram amounts of pyruvate carboxylase (apo and holo forms) in total tissue homogenates by immuno-blotting and by enzyme-linked immunosorbent assay are described. The data provided suggest that under normal physiological conditions (both in vivo and in vitro) essentially all the pyruvate carboxylase molecules are biotinylated.

Adipose Tissue↗
PubMed1986

Increase in bronchopulmonary infection due to branhamella catarrhalis.

In a six month prospective study during the winter Branhamella catarrhalis was isolated from the sputum of 63 patients with symptoms of bronchopulmonary infection: 49 isolates were in pure culture and 14 were with another pathogen, Haemophilus influenzae being the commonest (found with 10 of the 14 B catarrhalis isolates). Of 36 patients infected in the community, 26 required admission to hospital. The remaining 27 patients were infected while in hospital. Forty four of the 63 isolates produced beta lactamase; 26 of these had been acquired in the community. As a result 29 patients were treated inappropriately with ampicillin and did not respond to this treatment. beta Lactamase produced by B catarrhalis may also protect other pathogens normally susceptible to beta lactam antibiotics. Most patients had chronic lung diseases or lung cancer, but three otherwise healthy patients who did not smoke developed bronchitis. B catarrhalis contributed to the death of five patients. A survey of the antibiotic prescribing habits of the referring general practitioners together with the sensitivity results of B catarrhalis suggest that changes in antibiotic prescribing habits in the community may be responsible for the increase in B catarrhalis infection.

Adult↗
PubMed1986

Lack of immunoglobulin A1 protease production by Branhamella catarrhalis.

Clinical isolates of Branhamella catarrhalis from the sputum of 20 patients with acute bronchopulmonary infection were examined for synthesis of immunoglobulin A1 protease by immunoelectrophoresis. Ten strains produced beta-lactamase, and 10 were beta-lactamase negative. None of the strains demonstrated immunoglobulin A1 protease activity despite the fact that three different culture media were used.

Humans↗
PubMed1986

Domain unfolding and the stability of thermolysin in guanidine hydrochloride.

Equilibrium and kinetic studies of the unfolding and autolysis of the two domain protein thermolysin in guanidine hydrochloride are described. Enzyme activity, circular dichroism, fluorescence, sedimentation, size exclusion chromatography, and viscosity measurements were used to monitor conformational transitions and characterize the native and denatured states. The observation of biphasic transitions for the unfolding of apothermolysin and the spectroscopic changes associated with each phase of the overall unfolding process suggest unfolding of the N-terminal domain at less than 1 M guanidine hydrochloride, followed by the unfolding of the C-terminal domain, with the transition midpoint at 3 M guanidine hydrochloride. The refolding of the C-terminal domain is reversible; however, refolding of the N-terminal domain could not be demonstrated owing to protein aggregation. A quantitative analysis of the two transitions suggest that the unfolding of the two structural domains of thermolysin is not completely independent. Attempts to measure the unfolding of holothermolysin were hampered by autolysis. However, it was possible to show that at least three calcium ions serve to stabilize thermolysin against autolysis or unfolding in guanidine hydrochloride. Similar stabilization was observed for thermolysin with a single terbium ion bound at calcium site S(1). This result is consistent with our earlier findings, which suggest that calcium bound at sites S(1)-S(2) are located at a critical point on the unfolding pathway of thermolysin and serve to act as an interdomain lock.

Apoenzymes↗
PubMed1986

The incidence and antibiotic susceptibility of Branhamella catarrhalis in respiratory infections.

The incidence of Branhamella catarrhalis in respiratory infections at City Hospital, Edinburgh from January 1981 to April 1984 is described. Beginning in January 1982 there was an increased incidence associated with a high proportion of beta-lactamase-producing strains. The number of these strains increased: from January 1981 to April 1983, 61% of strains produced beta-lactamase, and 83% produced beta-lactamase from January to April 1984. 53% of patients were infected in hospital. Environmental studies showed that 7% of staff and 8% of patients were carriers; there was also circumstantial evidence of ward and patient-to-patient infection. The antimicrobial susceptibility of 54 clinical strains was tested: all strains were resistant to trimethoprim but were susceptible to clavulanic acid plus amoxycillin, chloramphenicol, erythromycin, co-trimoxazole, cefotaxime and cefuroxime. beta-Lactamase-negative strains were uniformly susceptible to penicillin and ampicillin.

Adult↗
PubMed1986

Bronchopulmonary infection due to B. catarrhalis. Clinical features and therapeutic response.

A study was made of the clinical features and therapeutic response of 144 patients from whose sputum Branhamella catarrhalis was isolated. Typically, features of bronchopulmonary infection with cough productive of moderate amounts of purulent sputum, fever and dyspnoea were present. Of 74 patients who were infected in the community, 50 required hospital admission. Nosocomial infection occurred in the remaining 70 patients. Most patients had chronic pulmonary diseases or carcinoma bronchus; pneumonia occurred in 12 patients. Acute tracheobronchitis developed in 4 healthy non-smokers after viral illnesses. B. catarrhalis contributed to the death of 8 patients. Overall, 59% of isolates produced beta-lactamase but the proportion had risen to 70% by the end of the study; half of these were community acquired. 41% of patients who were treated initially with ampicillin did not respond. Clavulanic acid plus amoxycillin, co-trimoxazole, erythromycin, tetracycline, cefuroxime and cefotaxime are useful alternative antibiotics. All strains of B. catarrhalis were resistant to trimethoprim.

Adult↗
PubMed1985

Complexities in the denaturation of horse metmyoglobin by guanidine hydrochloride.

The denaturation of horse metmyoglobin by guanidine hydrochloride was studied at pH 6.4 and 25 degrees C. Measurements of both the peptide circular dichroism and the absorbance in the Soret region suggest that the extent of renaturation strongly depends on the time interval during which the protein is exposed to concentrated solutions of the denaturant. From the equilibrium measurements of the absorption in the Soret region, it is concluded that the unfolding of metmyoglobin is complex. This is further supported by kinetic studies of denaturation which suggest the occurrence of the least four species in the reaction.

Animals↗
PubMed1985

Flow cytometric analysis of DNA replication during the differentiation of 3T3-L1 preadipocytes.

We have employed a flow cytometric method of monitoring DNA synthesis in order to study the stimulation of DNA replication during the induction of adipocyte differentiation in the preadipocyte cell line 3T3-L1. When confluent monolayers of this cell line are treated with a mixture of methyl isobutyl xanthine, dexamethasone, and insulin (MDI), they undergo at least one round of cell division, which is followed by the de novo synthesis of many enzymes that are involved in the formation of lipid. If the MDI-treated cells are incubated in iododeoxyuridine (IdUrd)- or bromodeoxyuridine (BrdUrd)-containing medium and subsequently stained with antibodies specific for these base analogues and with propidium iodide (PI), the kinetics of the induction of replication can be monitored. No differences in the patterns of IdUrd incorporation versus PI staining were observed between exponentially growing 3T3-L1 cells and those that had been stimulated to replicate DNA with MDI. In addition, we developed a flow cytometric (FCM) method for staining fatty acid synthetase and localizing the antigen in the G1 phase. We have thus demonstrated the feasibility of this methodology for correlating by FCM the production of enzymes such as fatty acid synthetase with IdUrd and BrUrd incorporation. The technique should permit studies of the inhibition of differentiation of adipocytes by halogenated pyrimidines.

Adipose Tissue↗
PubMed1985

Branhamella catarrhalis prevalence in a hospital population.

The prevalence of environmental and nasopharyngeal carriage of Branhamella catarrhalis in hospital staff members and in-patients was higher than previous studies suggested. Pernasal swabs performed on 59 members of staff revealed four isolates of Branh. catarrhalis, two of which were beta-lactamase producers. Seven isolates, two beta-lactamase positive, were recovered from 89 in-patients none of whom had bronchopulmonary infection with Branh. catarrhalis. From 117 settle plates six isolates, one beta-lactamase positive, were recorded. Attempts to bacteriocine type the isolates failed. In the absence of a typing system for Branh. catarrhalis evidence of nosocomial spread remains circumstantial.

Adult↗