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Biomedical subjects

M M Sharma

Publications and source records attributed to M M Sharma.

At least 19 recordsLinked to original sources
PubMed1999

Selective imaging of biofilms in porous media by NMR relaxation.

Nuclear magnetic resonance imaging (NMRI) techniques were employed to identify and selectively image biological films (biofilm) growing in aqueous systems. Biofilms are shown to affect both the longitudinal (T1) and transverse (T2) NMR relaxation time values of proximal water hydrogens. Results are shown for biofilm growth experiments performed in a transparent parallel-plate reactor. A comparison of biofilm distributions by both NMR and optical imaging yielded general agreement for both an open-flow system and an idealized porous system (the reactor without and with packed glass beads, respectively). The selective imaging of biofilm by relaxation NMRI is dependent upon the resolution of relaxation times for the fluid phases, dynamic range, and signal-to-noise ratio. For open-flow systems, the use of a rapid and quantitative T2-sorted NMRI technique was preferred. For porous systems where T2 values are generally more similar, a T1-weighted technique was preferred.

Biofilms↗
PubMed1998

Molecular determinants of bacterial adhesion monitored by atomic force microscopy.

Bacterial adhesion and the subsequent formation of biofilm are major concerns in biotechnology and medicine. The initial step in bacterial adhesion is the interaction of cells with a surface, a process governed by long-range forces, primarily van der Waals and electrostatic interactions. The precise manner in which the force of interaction is affected by cell surface components and by the physiochemical properties of materials is not well understood. Here, we show that atomic force microscopy can be used to analyze the initial events in bacterial adhesion with unprecedented resolution. Interactions between the cantilever tip and confluent monolayers of isogenic strains of Escherichia coli mutants exhibiting subtle differences in cell surface composition were measured. It was shown that the adhesion force is affected by the length of core lipopolysaccharide molecules on the E. coli cell surface and by the production of the capsular polysaccharide, colanic acid. Furthermore, by modifying the atomic force microscope tip we developed a method for determining whether bacteria are attracted or repelled by virtually any biomaterial of interest. This information will be critical for the design of materials that are resistant to bacterial adhesion.

Bacterial Adhesion↗
PubMed1998

Evaluating the interaction of bacteria with biomaterials using atomic force microscopy.

Bacterial infection of biomaterials represents one of the most important reasons for the failure of transdermal or implanted medical devices. The first and least understood step in biomaterial-associated infections is the initial interaction between bacteria and a surface. This initial interaction can be either attractive or repulsive depending on the physiochemical nature of the biological and synthetic surfaces, as well as the properties of the interstitial fluid. We have shown that atomic force microscopy (AFM) can be employed as an exquisitely sensitive and versatile tool for quantifying the interaction between bacteria and surfaces in physiological solutions. The forces of interaction between an AFM cantilever tip and a uniform lawn of bacteria immobilized on glass were determined. By comparing the interactions of cantilever tips with lawns of isogenic E. coli strains carrying genetic lesions that alter their cell surface composition, it was possible to evaluate the effect of macromolecules such as lipopolysaccharide and capsular polysaccharide on the adhesion process. Mutations that result in the synthesis of truncated lipopolysaccharide or in the overproduction of the negatively charged capsular polysaccharide colanic acid render the interaction of the bacteria with the AFM tip unfavorable due to increased electrostatic repulsion. Furthermore, AFM could be used to evaluate the adhesion of bacteria onto commercially relevant biomaterials. In one approach, micron-size polystyrene beads were attached to AFM tips which were then used to measure forces. Unfortunately, this approach is limited by the meager number of materials manufactured as beads of a size suitable for AFM measurements. As an alternative approach, AFM cantilever tips were coated with a confluent layer of bacteria and used to probe planar surfaces. In this configuration, AFM could be employed to measure the force of interaction between virtually any bacterium and surface of interest.

Bacterial Adhesion↗
PubMed1994

Structural and immunological characterization of a biosurfactant produced by Bacillus licheniformis JF-2.

Bacillus licheniformis JF-2 produces a very active biosurfactant under both aerobic and anaerobic conditions. We purified the surface-active compound to homogeneity by reverse-phase C18 high-performance liquid chromatography and showed that it is a lipopeptide with a molecular weight of 1,035. Amino acid analysis, fast atom mass and infrared spectroscopy, and, finally, 1H, 13C, and two-dimensional nuclear magnetic resonance demonstrated that the biosurfactant consists of a heterogeneous C15 fatty acid tail linked to a peptide moiety very similar to that of surfactin, a lipopeptide produced by Bacillus subtilis. Polyclonal antibodies were raised against surfactin and shown to exhibit identical reactivity towards purified JF-2 lipopeptide in competition enzyme-linked immunosorbent assays, thus providing further evidence for the structural similarity of these two compounds. Under optimal conditions, the B. licheniformis JF-2 biosurfactant exhibits a critical micelle concentration of 10 mg/liter and reduces the interfacial tension against decane to 6 x 10(-3) dyne/cm, which is one of the lowest interfacial tensions ever reported for a microbial surfactant.

Amino Acid Sequence↗
PubMed1992

Herbert screw: results of a single-centre trial.

We report the results of a single-centre trial of the Herbert screw in the treatment of acute fractures, fracture-dislocations and non-unions of the carpal scaphoid. In the trial, 22 patients were studied with a maximum follow-up of 2.5 years. Of the patients, 84 per cent had minimal or no pain, and 94 per cent were happy with their result or significantly improved. There was an average loss of 34 per cent of radial deviation of the wrist and of 10 per cent in cylinder grip strength. On radiographic examination, 86 per cent achieved satisfactory union. However, only 73 per cent of type D2 fractures united. Overall, the subjective and objective clinical results achieved were more satisfactory than the radiographic results would suggest.

Adult↗
PubMed1992

Surface-active compounds from microorganisms.

Microbial surfactants are a structurally diverse group of compounds consisting of hydrophilic and hydrophobic domains and which partition preferentially at interfaces. Biosurfactants are of increasing interest commercially as substitutes for synthetic surfactants particularly for environmental applications. This article discusses recent progress in the genetic and biochemical analysis of biosurfactant synthesis as well as the current status of fermentation technologies.

Bacteria↗
PubMed1979

Efficacy of metronidazole in dracunculiasis. A clinical trial.

In a clinical trial of metronidazole for dracunculiasis (75 cases), the drug was effective in giving symptomatic relief but had no preventive or vermicidal action. It was well tolerated. No difference was observed in the results of two dose schedules (200 mg or 400 mg three times daily for 10 days).

Dracunculiasis↗
PubMed1978

Pancreatic hypersecretion in liver disease.

Abnormally large duodenal aspirates have been reported in a large percentage of patients with cirrhosis of the liver. The source of this fluid has been variously ascribed to the liver and/or pancreas. The present study was undertaken to clarify its source. Eleven patients with cirrhosis of the liver and one with cholestatic hepatitis underwent an intraductal secretin test during endoscopic cannulation of the pancreatic duct. Six patients with cirrhosis had pancreatic hypersecretion ranging from 7.8 to 26.0 ml/min, while three patients demonstrated low secretory flow rates. Bile flow was negligible or nonexistent in ten patients, while in two others, larger but unmeasurable amounts of bile secretion were present. This study conclusively demonstrates that pancreatic hypersecretion may occur in patients with cirrhosis during secretin stimulation. Impaired metabolism of secretin or the associated pancreatic hypersecretion of early pancreatitis may be responsible for this finding.

Bile↗
PubMed1978

Endoscopic measurement of pancreatic juice secretory flow rates and pancreatic secretory pressures after secretin administration in human controls and in patients with acute relapsing pancreatitis, chronic pancreatitis, and pancreatic cancer.

Secretory flow rates were measured inside the main pancreatic duct during endoscopic retrograde cholangiopancreatography (ERCP) in patients with acute relapsing pancreatitis, chronic pancreatitis, and pancreatic cancer and in controls after intravenous administration of secretin. Peak secretory flow rates in these groups were 5.04 +/- 1.74, 0.71 +/-1.28, 0.60 +/- 1.37, and 4.13 +/- 0.88 ml/min, respectively. Peak secretory pressures were also measured intraductally in patients with acute relapsing pancreatitis and pancreatic cancer and in controls and were 402 +/- 69, 75 +/- 161, and 403 +/- 99 mm pancreatic juice, respectively. Peak secretory flow rates and pressures measured in controls during constant administration of secretin were similar to those measured when secretin was administered as a bolus.

Endoscopy↗
PubMed1975

Splenic-gonadal fusion.

Various aspects of splenic-gonadal fusion are discussed and 1 case of the continuous type is reported. A plea is made to include this condition in the differential diagnosis of scrotal masses, particularly those on the left side.

Adolescent↗
PubMed1975

Primary actinomycosis of the abdominal wall.

A rare case of primary actinomycosis of the abdominal wall presenting as a tumour is described. The patient responded to penicillin therapy well. A brief account of the literature is included.

Abdominal Muscles↗