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Biomedical subjects

M Dasgupta

Publications and source records attributed to M Dasgupta.

At least 37 records · Page 2Linked to original sources
PubMed1993

K-252a and staurosporine promote choline acetyltransferase activity in rat spinal cord cultures.

The protein kinase inhibitor K-252a increased choline acetyltransferase (ChAT) activity in rat embryonic spinal cord cultures in a dose-dependent manner (EC50 of approximately 100 nM) with maximal stimulatory activity at 300 nM resulting in as much as a fourfold increase. A single application of K-252a completely prevented the marked decline in ChAT activity occurring over a 5-day period following culture initiation. Of 11 kinase inhibitors, only the structurally related inhibitor staurosporine also increased ChAT activity (EC50 of approximately 0.5 nM). Effective concentrations of K-252a were not cytotoxic or mitogenic and did not alter the total protein content of treated cultures. Insulin-like growth factor I, basic fibroblast growth factor, ciliary neurotrophic factor, and leukemia inhibitory factor yielded dose-dependent increases in ChAT activity in spinal cord cultures. The combination of K-252a with insulin-like growth factor-I or basic fibroblast growth factor increased ChAT activity up to eightfold over that of untreated controls, which was greater than that observed with each compound alone. K-252a combined with ciliary neurotrophic factor or leukemia inhibitory factor demonstrated no additive or synergistic effects on ChAT activity. These results suggest that there are multiple mechanisms for the regulation of ChAT activity in spinal cord cultures. The enhancement of spinal cord ChAT activity by K-252a and staurosporine defines a new neurotrophic activity for these small organic molecules and raises the possibility that they may activate some regulatory elements in common with the ciliary neurotrophic factor and leukemia inhibitory factor family of neurotrophic proteins.

Alkaloids↗
PubMed1993

Reduction in peritonitis incidence in continuous ambulatory peritoneal dialysis with a new catheter and implantation technique.

Recurrent episodes of peritonitis with the same organism cultured at the catheter exit site suggest that early tunnel colonization is associated with a transfer of these organisms through the catheter tunnel directly from the skin into the peritoneal cavity. In this instance the catheter has failed in its fundamental design to establish and maintain a bacteriological barrier. A three-part study was conducted using the Moncrief-Popovich catheter and implantation technique. The first part of the study included 59 patients who used standard spike exchange systems with this new catheter and implantation technique. A reduction in the incidence of peritonitis occurred in the continuous ambulatory peritoneal dialysis (CAPD) program at the Austin Diagnostic Clinic. The previous peritonitis incidence was 1 every 9 patient-months. This study had 1 every 29 patient-months with 530 patient-months of experience. The second part of the study had 79 patients. All except 11 used disconnect exchange systems. There was a total of 482 patient-months of experience with 1 episode every 27 patient-months. Those using the disconnect systems (86%) had 1 episode every 32 patient-months. The third part of the study included microscopic studies of 12 excised catheters. Three were known to be contaminated. The examiners identified those catheters that were free or nearly free of biofilm on the catheter segment between the two cuffs. It is concluded that biofilm analysis and reduction in peritonitis incidence supports the theory that the new catheter and implantation technique form an improved bacteriological barrier in the access for peritoneal dialysis.

Catheterization↗
PubMed1989

The gamma-subunit of skeletal muscle phosphorylase kinase contains two noncontiguous domains that act in concert to bind calmodulin.

Phosphorylase kinase is a Ca2+-regulated, multisubunit enzyme that contains calmodulin as an integral subunit (termed the delta-subunit). Ca2+-dependent activity of the enzyme is thought to be regulated by direct interaction of the delta-subunit with the catalytic subunit (the gamma-subunit) in the holoenzyme complex. In order to systematically search for putative calmodulin (delta-subunit)-binding domain(s) in the gamma-subunit of phosphorylase kinase, a series of 18 overlapping peptides corresponding to the C terminus of the gamma-subunit was chemically synthesized using a tea bag method. The calmodulin-binding activity of each peptide was tested for its ability to inhibit Ca2+/calmodulin-dependent activation of myosin light chain kinase. Data were obtained indicating that two distinct regions in the gamma-subunit, one spanning residues 287-331 (termed domain-N) and the other residues 332-371 (domain-C), are capable of binding calmodulin with nanomolar affinity. Peptides from both of these two domains also inhibited calmodulin-dependent reactivation of denatured gamma-subunit. The interactions of peptides from both domain-N and domain-C with calmodulin were found to be Ca2+-dependent. Dixon plots obtained using mixtures of peptides from domain-N and domain-C indicate that these two domains can bind simultaneously to a single molecule of calmodulin. Multiple contacts between the gamma-subunit and calmodulin (delta-subunit), as indicated by our data, may help to explain why strongly denaturing conditions are required to dissociate these two subunits, whereas complexes of calmodulin with most other target enzymes can be readily dissociated by merely lowering Ca2+ to submicromolar concentrations. Comparison of the sequences of the two calmodulin-binding domains in the gamma-subunit of phosphorylase kinase with corresponding regions in troponin I indicates similarities that may have functional and evolutionary significance.

Amino Acid Sequence↗
PubMed1989

Tobramycin resistance of mucoid Pseudomonas aeruginosa biofilm grown under iron limitation.

Mucoid Pseudomonas aeruginosa isolated from a patient with cystic fibrosis was cultivated at a slow growth rate (D = 0.05 h) under iron limitation in a chemostat. Biofilm was allowed to form on acrylic tiles. The kinetics of the biofilm formation was then investigated. The population of sessile bacteria reached 1.5 x 10(9) cells/cm2 on day 5 and remained relatively constant throughout the study (day 7). The population of planktonic cells in the chemostat reached 4 x 10(9) on day 1 and stayed fairly constant throughout. Planktonic cells were very sensitive to tobramycin. They were killed by exposure to 10 mg/l tobramycin within 2 h. Young biofilm cells of P. aeruginosa (day 2 of colonization) were found to be more resistant. Approximately 40% of the adherent cells remained viable after exposure to 10 micrograms tobramycin/ml for 5 h. An increase in the concentration of tobramycin to 20 mg/l resulted in an enhancement of the killing of young biofilm bacteria and approximately 1.5% of them remained viable after exposure to this concentration of antibiotic for 5 h. Old biofilm bacteria, examined at day 7, were the most resistant and 15% of the cells were found to be viable after they were exposed to 200 mg/l of tobramycin for 5 h. When either young or old biofilm cells of mucoid P. aeruginosa were scraped from the tiles to produce a planktonic cell suspension they were sensitive to 5 mg/l tobramycin.

Culture Media↗
PubMed1989

Interaction of biofilm bacteria with antibiotics in a novel in vitro chemostat system.

Pseudomonas aeruginosa was cultivated at low growth rates under iron-limiting conditions on acrylic tiles. Biofilm cells exhibited increased tobramycin resistance compared with that of planktonic cells, and in old biofilms were more resistant than were cells in young biofilms. However, on suspension of the biofilm bacteria, glycocalyx-mediated resistance was lost.

Anti-Bacterial Agents↗
PubMed1987

Suppression of superoxide generation by normal polymorphonuclear leukocytes preincubated in plasma from patients with Felty's syndrome.

Polymorphonuclear leukocytes (PMN) isolated from patients with Felty's syndrome (FS) generate fewer superoxide anions (O-2) upon stimulation with fmet-leu-phe than PMN from normal controls or patients with rheumatoid arthritis (RA). In this study, plasma samples were obtained from 12 patients with RA and 12 patients with FS. Incubation of normal PMN in plasma from Felty patients resulted in a significant reduction in both the rate and total quantity of O-2 generation when activated with fmet-leu-phe. This was not observed with plasma from RA patients. The capacity of a plasma sample to suppress O-2 generation correlated with plasma IgG-PMN-binding activity (IgG-PBA) and, to a lesser extent, with the content of circulating immune complexes (CIC). These data suggest that IgG-PBA and possibly CIC have a pathogenetic role in both qualitative and quantitative defects in PMN in Felty patients.

Aged↗
PubMed1986

Elastase from polymorphonuclear leucocytes: a regulatory enzyme in immune complex disease.

In sputa of 21 cystic fibrosis patients suffering from chronic Pseudomonas aeruginosa lung infections, activities of lysosomal proteases released from polymorphonuclear leukocytes (PMN) and immune complexes were quantitatively determined. The results showed that low immune complex values correlated with high protease activities and vice versa. In a longitudinal study fluctuating, reciprocal changes of the parameters were observed. Therefore, the hypothesis was investigated as to whether PMN elastase cleaves immune complexes and regulates inflammation. It was shown that treatment of immune complex-positive sputa with PMN elastase decreased IgG and IgA immune complex values and lead to cleavage of the immunoglobulins in the hinge region. PMN elastase-treated samples were not able to stimulate the oxidative burst of PMN. Cleavage of in vitro built immune complexes did not lead to liberation of bound antigen. Western blot analysis of one sputum sample revealed split products of the IgG heavy chain. The results suggest that PMN elastase splits off the Fc portion of immunoglobulins in immune complexes and thus regulates inflammation by a feedback mechanism leading to cyclic inflammatory states.

Antigen-Antibody Complex↗
PubMed1986

Measures of immunologic and inflammatory responses in vitro in rheumatoid patients treated with methotrexate.

We examined the effects of low dose parenteral methotrexate (MTX) on immunologic and inflammatory responses of potential importance in the pathogenesis of rheumatoid arthritis. Only 2 significant changes were noted: the number of esterase positive cells in the peripheral blood decreased, and the uptake of tritiated thymidine by incubated peripheral blood mononuclear cells fell markedly. These changes were present 48 h after an injection of MTX, before decreased disease activity became clinically apparent. We therefore conclude that they were direct effects of the drug itself.

Antibody Formation↗
PubMed1983

Superoxide production in neutrophils of patients with rheumatoid arthritis and Felty's syndrome.

The production of superoxide by N-formylmethionyl-leucyl-phenylalanine activated neutrophils was measured prospectively with a ferricytochrome C reduction assay in 33 normals, 33 patients with rheumatoid arthritis and 9 patients with Felty's syndrome. Both the rate and quantity of superoxide production were significantly lower in patients with Felty's syndrome when compared to the other 2 groups. This finding suggests a possible additional factor in the increased propensity of these patients to develop infections.

Arthritis, Rheumatoid↗
PubMed1975

The behavior of carbenicillin as a nonreabsorbable anion.

In order to study the mechanism of hypokalemic alkalosis which occurs in some patients being treated with disodium carbenicillin, renal clearance experiments were carried out in rats and observations were made on electrical changes in isolated toad bladders. In rats maintained on a sodium-free diet, intravenous infusion of carbenicillin at 40 mg. per hour resuited in an immediate diuresis characterized by a striking increase in K and NH4 excretion, and progressive acidification of the urine. In a control group of rats, also prepared with a sodium free diet, intravenous infusion of mannitol resulted in a comparable diuresis, but no significant changes in K and NH4 excretion, and no acidification of the urine. The urinary changes in the carbenicillin-treated rats could not be accounted for by any alterations in blood electrolytes, acid-base values, or glomerular filtration rate (GFR). Isonatric, isohydric substitution of carbenicillin for chloride in the mucosal bathing media of toad bladders mounted in Ussing chambers resulted in a reversible increase in electrical potential (PD) and resistance (R) without a comparable change in short-circuit current (SCC). Substitution in the serosal medium resulted in a reversal of polarity of PD and SCC in 4 of 9 experiments, a finding best explained by more rapid movement of chloride from M leads to S than carbenicillin movement from S leads to M (a chloride diffusion potential). The observations in both the rat and toad bladder experiments are consistent with the view that carbenicillin behaves as a nonreabsorbable anion. Hypokalemic alkalosis in patients receiving this drug can thus be attributed to increased electrical negativity of the distal nephron with subsequent enhancement of K and H secretion.

Acid-Base Equilibrium↗