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Biomedical subjects

S G Desai

Publications and source records attributed to S G Desai.

At least 19 recordsLinked to original sources
PubMed2004

Cloning of L-lactate dehydrogenase and elimination of lactic acid production via gene knockout in Thermoanaerobacterium saccharolyticum JW/SL-YS485.

The gene encoding L-lactate dehydrogenase from Thermoanaerobacterium saccharolyticum JW/SL-YS485 was cloned, sequenced, and used to obtain an L-ldh deletion mutant strain (TD1) following a site-specific double-crossover event as confirmed by PCR and Southern blot. Growth rates and final cell densities were similar for strain TD1 and the wild-type grown on glucose and xylose. Lactic acid was below the limit of detection (0.3 mM) for strain TD1 on both glucose and xylose at all times tested, but was readily detected for the wild-type strain, with average final concentrations of 8.1 and 1.8 mM on glucose and xylose, respectively. Elimination of lactic acid as a fermentation product was accompanied by a proportional increase in the yields of acetic acid and ethanol. The results reported here represent a step toward using metabolic engineering to develop strains of thermophilic anaerobic bacteria that do not produce organic acids, and support the methodological feasibility of this goal.

Acetic Acid↗
PubMed2001

Characterization of 13 newly isolated strains of anaerobic, cellulolytic, thermophilic bacteria.

Characteristics of 13 newly isolated thermophilic, anaerobic, and cellulolytic strains were compared with previously described strains of Clostridium thermocellum: ATCC 27405 and JW20 (ATCC 31549). Colony morphology, antibiotic sensitivity, fermentation end-products, and cellulose degradation were documented. All 13 strains were sensitive to erythromycin (5 microg/ml) and chloramphenicol (25 microg/ml), and all strains but one were sensitive to kanamycin (20 microg/ml). Polymerase chain reaction (PCR) amplification using primers based on gene sequences from C. thermocellum ATCC 27405 was successful for all 13 strains in the case of the hydrogenase gene and 11 strains in the case of phosphotransacetylase/acetate kinase genes. Ten strains amplified a product of the expected size with primers developed to be specific for C. thermocellum 16SrRNA primers. Two of the 13 strains did not amplify any product with the PCR primers designed for the phosphotransacetylase/acetate kinase and 16SrRNA primers. A MboI-like GATC- recognizing restriction activity was present in all of the five strains examined. The results of this study have several positive implications with respect to future development of a transformation system for cellulolytic thermophiles.

Bacteria, Anaerobic↗
PubMed1994

Lipids of extremely halophilic archaeobacteria from saline environments in India: a novel glycolipid in Natronobacterium strains.

Several strains of extremely halophilic archaeobacteria, both non-alkaliphilic and alkaliphilic, including Halobacterium, Haloferax and Natronobacterium species, were isolated from salt locales in India. The major phospholipids in these strains were the C20-C20-glycerol diether analogues of phosphatidylglycerolmethylphosphate (PGP-Me), phosphatidylglycerol (PG) and phosphatidic acid (PA). In addition, the Halobacterium strains possessed the characteristic glycolipids, sulfated triglycosyl and tetraglycosyl diethers (S-TGD-1 and S-TeGD, respectively) and the unsulfated triglycosyl diether (TGD-1); and the Haloferax strains had the characteristic sulfated and unsulfated diglycosyl glycerol diethers (S-DGD-1 and DGD-1, respectively). The PGP-Me, and PG components of the haloalkaliphiles each occurred as two molecular species with C20-C20- and C20-C25-(isopranoid) glycerol diether lipid cores. In contrast to previous reports of the absence of glycolipids in natronobacteria, the Natronobacterium strains from India were found to contain small amounts of a novel glycolipid identified as glucopyranosyl-1-->6-glucopyranosyl-1-->1-glycerol diether (DGD-4). The lipid cores of DGD-4 also contained mainly unhydroxylated or hydroxylated C20-C20, C20-C25 and C25-C25 molecular species with unsaturated (isoprenoid) chains. Hydroxylated lipid cores have previously been identified only in some methanogenic archaeobacteria.

Carbohydrate Sequence↗
PubMed1991

Angiotensin II augmentation of tyrosine kinase activity in human adherent mononuclear cells.

The relationship of angiotensin converting enzyme activity and angiotensin II to the inflammatory process in diseases such as sarcoidosis remains unclear. We hypothesize that granuloma macrophages regulate inflammation by release of angiotensin converting enzyme, which produces angiotensin II, and that angiotensin II in turn modulates monocyte/macrophage activity. Since tyrosine kinase catalyzes phosphorylation of tyrosine residues in proteins and is important in signal transduction and cellular activation, we further postulated that monocyte tyrosine kinases may play a role in the regulation of this process. Mononuclear cells from 11 healthy subjects were assayed for tyrosine kinase activity in the presence and absence of angiotensin II. In addition, tyrosine-specific phosphorylation of cellular proteins was also determined. Angiotensin II increased tyrosine kinase activity in a concentration-dependent manner. The maximal stimulation, which varied from 31 to 506%, was achieved following incubation of cells with 10(-4) M angiotensin II. Angiotensin II also increased the tyrosyl-phosphorylation of three proteins with molecular weights of 57, 62, and 63 kDa. We conclude that tyrosine kinase activity of adherent mononuclear cells and tyrosine phosphorylation of certain protein(s) may be involved in angiotensin II regulation of inflammatory processes.

Angiotensin II↗
PubMed1988

Primary antituberculosis drug resistance and acquired rifampicin resistance in Gujarat, India.

The prevalence of primary antituberculosis drug resistance in Gujarat, as studied between 1983 and 1986, was found to be significantly high, especially for isoniazid (13.9%) and streptomycin (7.4%). Primary rifampicin and pyrazinamide resistance were not detected in any strain. The prevalence of rifampicin resistance among treatment failure and relapse cases of pulmonary tuberculosis increased significantly from 2.8% in 1980 to 37.3% in 1986. In about 95% of the rifampicin resistant strains there was also resistance to isoniazid or streptomycin or both: resistance to isoniazid was detected in more than 90%.

Antitubercular Agents↗
PubMed1988

Multimodality evoked potentials in sarcoidosis.

Neurosarcoidosis is suspected on clinical grounds and then confirmed by radiography, by spinal fluid examination, or by biopsy. To determine whether evoked potential testing may also be of value in diagnosing and following the course of neurosarcoidosis, multimodality evoked potentials were obtained in 12 men with sarcoidosis, including two with neurosarcoidosis. Seven of 12 subjects, one of whom had neurosarcoidosis, manifested abnormal evoked potentials. Visual evoked potentials were abnormal in one patient and somatosensory evoked potentials were abnormal in one patient. Five additional patients, including one with neurosarcoidosis, had abnormal auditory evoked potentials suggestive of auditory nerve or low pons involvement. These data indicate that multimodality evoked potentials, especially auditory potentials, may show central nervous system involvement in patients with sarcoidosis in the absence of clinically apparent disease.

Adrenal Cortex Hormones↗
PubMed1987

Pyrazinamidase activity of Mycobacterium tuberculosis--a test of sensitivity to pyrazinamide.

Pyrazinamidase activity has been found to correlate with pyrazinamide sensitivity in strains of Mycobacterium tuberculosis. In vitro sensitivity to pyrazinamide in acidified Löwenstein-Jensen medium, and pyrazinamidase activity by the Wayne method, were determined in 378 clinical isolates of M. tuberculosis. A close correlation was observed between the results of both tests. This method of detecting pyrazinamidase activity was found to be a rapid, simple and reliable substitute for pyrazinamide sensitivity testing, and it overcomes the difficulty of growing M. tuberculosis at pH 5.5, as required in the standard method.

Amidohydrolases↗
PubMed1987

Multimodality evoked response testing in sarcoidosis.

Neurosarcoidosis is suspected on clinical grounds. The diagnosis is confirmed radiographically or by spinal fluid examination or biopsy. Evoked response testing in sarcoidosis has been studied by three groups of investigators. Visual, somatosensory, or brainstem auditory evoked potentials were abnormal in some sarcoidosis patients with, and in others without clinical evidence of neurological involvement. Multimodality evoked response testing may be useful in further defining neurosarcoidosis and in detecting subclinical disease.

Evoked Potentials↗
PubMed1986

T-cell differentiation antigens and antigenic lymphocyte reactivity in pleural effusions.

Blood and pleural effusion mononuclear cells from thirteen patients were examined for the expression of T lymphocyte differentiation antigens as well as in vitro thymidine incorporation. The ratio of T4 to T8 cells was significantly greater among pleural effusion lymphocytes than among blood lymphocytes. Effusion lymphocyte responses to phytohaemagglutinin were less than those of blood lymphocytes. Unstimulated thymidine incorporation was greater in pleural effusion lymphocytes. Antigen-stimulated lymphocyte reactivity was not consistently greater in either blood or effusion lymphocytes. Lymphocytes from tuberculous effusions all reacted to tuberculin. Pleural effusion lymphocytes, regardless of the etiology of the effusion, possessed the same range of antigenic specificities as did blood lymphocytes. Therefore, effusion lymphocyte responsiveness to tuberculin does not prove the presence of tuberculous pleurisy but does indicate sensitisation to tuberculin.

Adult↗
PubMed1984

Hypoxemia during hemodialysis using acetate versus bicarbonate dialysate.

To evaluate the extent and cause(s) of dialysis-related hypoxemia, we studied 10 patients, 7 days apart using acetate (AC) and bicarbonate dialysate (HCO3). We measured arterial blood gases, WBC, minute ventilation (VE) and inspired and expired gas concentrations and calculated the respiratory quotient (R) and the alveolar-arterial oxygen difference (A-a)DO2 before and during hemodialysis. 8 patients developed hypoxemia. Arterial PO2 (PaO2) dropped similarly at 30 min from 93 +/- 5 to 78 +/- 6 (p less than 0.05) and 89 +/- 4 to 79 +/- 5 mm Hg (p less than 0.05) with AC and HCO3, respectively. R and VE decreased during AC (p less than 0.05). (A-a)DO2 increased at 30 min and correlated with the drop in PaO2 during both AC (r = 0.68, p less than 0.025) and HCO3 (r = 0.76, p less than 0.025). The fall in PaO2 also correlated with the fall in WBC count for both AC and HCO3 (r = 0.63, p less than 0.005). The increase in arterial pH during HCO3 (up to 7.45 +/- 0.01) was significantly greater than that during AC (up to 7.42 +/- 0.01) (p less than 0.025), and coincided with a relative decrease in VE. We conclude that (1) HCO3 does not prevent hypoxemia, and (2) hypoventilation V/Q abnormalities and increase in arterial pH, contribute variably to dialysis related hypoxemia depending on the type of dialysate and the time during dialysis.

Acetates↗