Biomedical subjects
S Das
Publications and source records attributed to S Das.
Properties of an acid phosphatase from Legionella micdadei which blocks superoxide anion production by human neutrophils.
The high-speed supernatant (100,000 g, 1 h) obtained after centrifuging a suspension of Legionella micdadei that had been freeze-thawed and sonicated contained (i) considerable acid phosphatase activity when assayed using 4-methylumbelliferyl phosphate (MUP) as the substrate, and a factor that blocked superoxide anion production by human neutrophils stimulated with f-Met-Leu-Phe. Chromatography of the extract on a hydroxylapatite column resolved two acids phosphatases (designated ACP1 and ACP2). Subsequent chromatography of ACP2 on a Sephadex G-150 column revealed coincident elution of phosphatase activity and neutrophil blocking activity. When heated at 45 degrees C for various periods of time, the phosphatase activity of the acid phosphatase preparation was lost at the same rate as the ability of the preparation to block superoxide anion production by neutrophils. Furthermore, preincubation of neutrophils and acid phosphatase together in the presence of a heteropolymolybdate complex that inhibits the phosphatase eliminated the effect of the L. micdadei phosphatase on neutrophil superoxide anion production. ACP2 had the following properties: pH optimum, 6.0; Km for MUP, 3.8 mM; isoelectric point, 4.5; substrate specificity, MUP greater than ADP greater than phosphoenolpyruvate greater than phosphothreonine greater than phosphoserine greater than phosphotyrosine; molecular weight (estimated by sucrose density gradient centrifugation and gel filtration chromatography), 71,000-86,000. These results indicate that a cell-associated phosphatase may play a role in the virulence of L. micdadei.
The primary structure of rabbit and rat prealbumin and a comparison with the tertiary structure of human prealbumin.
The primary structures of rabbit and rat prealbumin have been determined. The amino acid sequence of rabbit prealbumin was determined by analyses of peptides obtained by trypsin and Staphylococcus aureus protease digestions. The rat prealbumin sequence was deduced by analyses of tryptic peptides as well as by nucleotide sequencing of cDNA clones. Both amino acid sequences contain 127 amino acid residues, the same as human prealbumin. Pairwise comparisons show that the three sequences are more than 80% identical. All three prealbumins were found to display significant sequence homology with human thyroxine-binding globulin. A comparison of the primary structures of the prealbumins with the tertiary structure of human prealbumin shows that amino acid replacements are preferentially located at the surface of the molecule and in the loops connecting the beta-strands. The locations of the replacements are discussed as regards the different molecular interactions in which prealbumin is involved.
Characterization of Leishmania donovani acid phosphatases.
A crude membrane fraction from promastigotes of Leishmania donovani grown in a liquid culture medium containing 20% fetal calf serum was prepared by freeze-thawing, centrifugation (200,000 X g, 30 min), and extraction with 2% (w/v) sodium cholate. After removal of the bile salt by chromatography on a Sephadex G-75 column, the solubilized membrane protein fraction, rich in acid phosphatase activity, was chromatographed on columns containing concanavalin A-Sepharose, QAE-Sephadex, and Sephadex G-150 and G-100. Three distinct acid phosphatases were resolved: the major phosphatase activity (70% of the total) was L-(+)-tartrate-resistant (designated ACP-P1) and corresponds to the acid phosphatase localized to the outer surface of the parasite's plasma membrane; the other two phosphatases (ACP-P2 and ACP-P3) account for the remaining 30% of the particulate acid phosphatase activity, and both of these enzymes are L-(+)-tartrate-sensitive. Using a combination of sucrose density gradient centrifugation, gel filtration chromatography, and sodium dodecyl sulfate-polyacrylamide gel electrophoresis, it was determined that ACP-P1 is a 128,000-dalton protein composed of two subunits of 65,000-68,000 daltons. ACP-P1 has an isoelectric point of 4.1, a pH optimum of 5.5, hydrolyzes fructose 1,6-diphosphate, but no other sugar phosphates and dephosphorylates phosphotyrosine, yeast mannan, and the phosphorylated form of rat liver pyruvate kinase. ACP-P2 (pI, 5.4) and ACP-P3 (pI, 7.1) with molecular masses of 132,000 and 108,000 daltons, respectively, are both tartrate-sensitive and are distinguished from each other on the basis of their sensitivity to inhibition by polyanionic molybdenum complexes. These two phosphatases also have their pH optima in the pH 5.0-6.0 range, but have a considerably broader substrate specificity than ACP-P1.
A positive regulatory element is involved in the induction of the beta-galactosidase gene from Kluyveromyces lactis.
The regulation of the LAC4 gene encoding beta-galactosidase in the yeast Kluyveromyces lactis has been studied. The expression of cloned LAC4 gene present on autonomously replicating plasmids was normally regulated by lactose or galactose as inducers. The LAC4 transcription initiation sites were mapped on two plasmids, PTY75-LAC4 and pKL2. The sites were found to be dependent on the level of gene expression and on the plasmid used. Under induced conditions, the normal cluster of initiation sites was used on both plasmids, whereas under non-induced conditions LAC4 on pKL2 showed additional sites. Deletion mapping of the 5' regulatory region of the LAC4 gene revealed a DNA element required for induction, presumably for the binding of a positive regulator.
Role of interfacial structured water in membrane: osmotic properties of L-alpha-egg lecithin liposomes.
The role of large amounts of membrane-bound water in regulating various functions of the membrane is not clear at present. We have investigated the effect of perturbing the interfacial water structure on the osmotic shrinkage properties, such as water permeability and extent of shrinkage of egg lecithin liposomes. Water structure was perturbed by a series of reagents which have been earlier reported to affect phase transition of dipalmitoyl phosphatidylcholine liposomes by perturbing interfacial water structure. Anomalous variations of osmotic shrinkage properties with concentration of structure maker and breaker reagents have been interpreted to arise from concentration-dependent structural transitions of the ordered water at the membrane-aqueous interface. Various modes of interaction of these reagents on interfacial structured water have been suggested. Influence of molecular size and functional groups on the molecule in actions of some structure makers and breakers were also observed.
Lack of interaction between thyrotropin releasing hormone and its analogs with 3H-quinuclidinyl benzilate recognition sites in the rat striatum.
The effects of thyrotropin releasing hormone (TRH) on the binding of 3H-quinuclidinyl benzilate (QNB) to cholinergic muscarinic receptors of striatal region of rat brain were evaluated. In vitro studies indicate that neither TRH, its two analogs, MK-771 [L-N-(2-oxopiperidin-6-yl-carbonyl)-L-histidyl-L-thiazolidine-4-++ +carboximide] and DN-1417 (gamma-butyrolactone- gamma-carbonyl-L-histidyl-L-prolineamide) nor the metabolite histidyl-proline diketopiperazine [cyclo(His-Pro)] at concentrations ranging from 10(-9) to 10(-3) M affected 3H-QNB binding to striatal muscarinic receptors. On the other hand, p-Glu-His-Pro-OH (TRH-free acid), another metabolite of TRH caused significant inhibition (21%) at 10(-4) M concentration. Intraperitoneal administration of TRH (1 or 10 mg/kg) also failed to elicit any changes in the affinity (Kd) or density (Bmax) of muscarinic receptors in the striatum. The results suggest that TRH does not influence striatal muscarinic receptors and that the known effects of TRH and its analogs on central cholinergic system may be due to mechanisms other than those affecting postsynaptic muscarinic receptors directly.
Incarcerated femoral hernia after radical cystectomy.
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Chronic alpha-adrenoceptor blockade with trimazosin in congestive heart failure.
We evaluated chronic adjunctive alpha-1 receptor blockade with trimazosin in congestive heart failure. This agent produced hemodynamic effects consistent with venodilation (reduced left ventricular volume and filling pressure with increased left ventricular ejection fraction), but only during exercise. Resting hemodynamic parameters and exercise duration were not significantly altered by chronic alpha-1 receptor blockade.
Effect of prolyl-leucyl-glycinamide on blood pressure, heart rate and angiotensin converting enzyme activity in spontaneously hypertensive and Wistar-Kyoto normotensive rats.
The effect of melanotropin release inhibiting factor (L-prolyl-L-leucyl-glycinamide, MIF) on blood pressure and heart rate of both spontaneously hypertensive (SH) and age-matched normotensive Wistar-Kyoto (WKY) rats was investigated. A single s.c. injection of MIF at a lower dose (1 mg/kg) had no effect on the blood pressure of either SH or WKY rats when measured 1,4 and 7 hr after the injection of MIF. Higher doses of MIF (2 or 4 mg/kg), on the other hand, significantly depressed blood pressure in SH animals at 4 and 7 hr after the drug injection. However, MIF had no effect on the blood pressure of WKY rats. None of the doses of MIF had any appreciable effect on the heart rate of either SH or WKY rats. Angiotensin-converting enzyme (ACE) activity of anterior pituitary of WKY rats was significantly higher than that of SH rats. ACE activity of neurohypophysis, however, was lower in WKY rats than in SH rats. No change in the ACE activities of central and peripheral tissues (plasma, pituitary, striatum and hypothalamus) of SH rats was observed 4 hr after the administration of MIF (1, 2 or 4 mg/kg), a time at which MIF produced significant antihypertensive effect. It is concluded that MIF causes a delayed lowering of blood pressure only in the genetically hypertensive rats and that this effect is not mediated via an action on the ACE.
Vesicoureteral reflux in women with primary bladder diverticulum.
In 22 years we treated 271 adults, including 149 women, for vesicoureteral reflux. We describe our management of vesicoureteral reflux in 12 women between 18 and 58 years old who had an associated primary vesical diverticulum. A vesical diverticulum located near the ureteral orifice caused reflux by destroying the ureterovesical valve in 11 of these 12 patients. In 1 woman a bladder diverticulum distant from the ureteral orifice acted as a reservoir of chronic infection, which perpetuated reflux in a marginally competent ureterovesical junction. The reflux disappeared after excision of the diverticulum. Reflux was bilateral in 3 and unilateral in 9 cases. Symptoms of acute pyelonephritis were noted in 3 women and radiographic changes of chronic pyelonephritis were noted in 4. Urinary infection was controlled successfully by medical management in 4 patients. Ureteral reimplantation after excision of the bladder diverticulum and repair of the bladder wall was successful in eradicating reflux in 5 patients. Each patient was followed for 3 or more years.
Vesicoureteral reflux in patients with obstructive prostatic disease.
We present our experience during a 22-year period with the management of 53 patients in whom vesicoureteral reflux was associated with obstructive prostatic disease. There were 45 cases of benign prostatic hyperplasia and 8 cases of carcinoma of the prostate. After prostatectomy medical management of reflux was successful in controlling urinary infection in 34 patients and an operation was performed in 19. Each patient was followed for at least 1 year.
Upper urinary tract transitional cell carcinoma in patients with bladder carcinoma and associated vesicoureteral reflux.
Of 269 patients with bladder neoplasms treated during a 20-year period 47 had associated vesicoureteral reflux. All 47 patients were followed for 3 years or more, or until death. Upper urinary tract transitional cell cancer developed in 3, each of whom had recurrent bladder cancer. Among the 222 patients who had vesical cancer without reflux transitional cell carcinoma of the ureter developed in only 1, 11 years after transurethral resection for a bladder tumor. The incidences of upper tract transitional cell cancer in patients with and without vesicoureteral reflux were 6.4 and 0.44 per cent, respectively, which support the suggested role of reflux in disseminating or seeding of cancer cells from the bladder into the upper urinary tract. Patients with bladder cancer and associated vesicoureteral reflux have an approximately 15-fold greater risk of upper tract cancer developing compared with those without reflux. We recommend vigilant scrutiny of patients with recurrent bladder cancer and associated vesicoureteral reflux for early detection of upper urinary tract transitional cell carcinoma.
Resistance of leishmanial phosphatases to inactivation by oxygen metabolites.
Leishmania donovani promastigotes produce large quantities of two distinct acid phosphatases; a tartrate-resistant enzyme is localized to the external surface of the plasma membrane, and a tartrate-sensitive enzyme is secreted into the growth medium. It was shown previously that preincubation of human neutrophils and macrophages with the tartrate-resistant phosphatase markedly reduced the ability of these host cells to produce superoxide anions in response to stimulation with the activator formyl-methionyl-leucyl-phenylalanine. The possibility that the cell surface acid phosphatase or the phosphatase that is secreted into the extracellular fluid might compromise other host cell functions, especially intracellular ones, depends on the ability of the enzyme to resist exposure to toxic oxygen metabolites (e.g., superoxide anion, hydrogen peroxide, hypochlorite) generated by phagocytic cells. In the present report, we show that both leishmanial acid phosphatases were relatively resistant to inactivation by oxygen metabolites. At pH 5.5, the activity of the tartrate-resistant phosphatase was reduced 50% by incubation for 1 h with each of the following: 30 mM O2-, 500 mM hydrogen peroxide, and 6 mM hypochlorite ion. These concentrations are many fold greater than the concentrations of these substances that are generated by stimulated polymorphonuclear phagocytes. The tartrate-sensitive acid phosphatase differed markedly from the tartrate-resistant phosphatase in that the former was essentially insensitive to even very high concentrations of superoxide anion and hydrogen peroxide. Furthermore, 50% inactivation of the tartrate-sensitive leishmanial phosphatase required exposure to 35 mM hypochlorite for 30 min. These results indicate that the catalytic potential of these two leishmanial acid phosphatases probably survives exposure to toxic oxygen metabolites generated by neutrophils and macrophages.
Effect of chronic treatment with morphine on the binding of 3H-N-n-propylnorapomorphine to striatal membranes of rats: influence of prolyl-leucyl-glycinamide.
The effect of chronic administration of morphine to Sprague-Dawley rats on the binding of dopamine receptor agonist, 3H-N-n-propylnorapomorphine (3H-NPA) to striatal membranes was determined. For chronic administration of morphine, rats were implanted subcutaneously with four morphine pellets (each containing 75 mg of morphine free base) during a 3-day period. Placebo pellet-implanted rats served as controls. Two experimental protocols were followed. In one, the rats were sacrificed 70 h after the implantation of first pellet and in the other, the pellets were removed and the animals were sacrificed 24 h later, and the binding of 3H-NPA was determined. Rats receiving morphine showed no difference in the total number of binding sites (Bmax value) but there was a decrease in the apparent dissociation constant (Kd value) compared with placebo controls. Moreover, such a decrease in Kd in morphine-treated rats persisted even 24 h after removal of morphine pellets. The effect of prolyl-leucyl-glycinamide (MIF; 2 mg/kg), which has been shown to inhibit the development of tolerance to and dependence on morphine, on the changes in the binding of 3H-NPA induced by the implantation of morphine pellets was also determined. MIF antagonized the decreases in Kd values induced by the administration of morphine. However, when administered chronically by itself, MIF had no effect on either the Bmax or Kd values of 3H-NPA. It is concluded that the chronic administration of morphine is associated with enhanced activity of dopamine receptors in the central nervous system as revealed by lowering of the Kd value of the agonist, NPA.(ABSTRACT TRUNCATED AT 250 WORDS)
Partial purification and characterization of tumor associated antigen in cervical carcinoma.
An identical component of tumor associated antigen (TAA) was detected in all clinical stages of the carcinoma of cervix (CaCx), in both premenopausal and postmenopausal patients, using heterologous antisera against the cancer tissues by immunodiffusion and immunoelectrophoretic tests. The TAA appeared to be cross-reacting specifically with carcinoma of other gynecological organs. A second TAA component was observed to be present only in CaCx, Stage II of premenopausal patients. The TAA component of CaCx common for all clinical stages, irrespective of climacteric states, was partially purified by subjecting postmeno CaCx, Stage II to gel filtration on Sephadex G-200. The antigen was found to be glycoprotein in nature, enzyme sensitive, highly thermostable and antigenically active at a pH range of 2.0-10.7. The approximate molecular weight of the component was found to be 67 000.
Effect of lithium treatment on blood pressure and angiotensin-converting enzyme activity in normotensive Wistar-Kyoto and spontaneously hypertensive rats.
Short-term administration of LiCl (4 mEq/kg) reduced blood pressure of SH rats but had no effect on WKY animals. Lower doses of lithium, however, did not alter blood pressure in the SH or WKY rats. Acute and chronic administration of lithium had no appreciable effect on heart rate. Although all rats gained weight during the treatment period, the per cent increase in body weight of LiCl (4 mEq/kg) treated SH and WKY rats was significantly lower than the corresponding vehicle treated animals. Angiotensin converting enzyme (ACE) activity of anterior pituitary of WKY rats was significantly higher than that of SH rats. ACE activity of neurohypophysis, instead was lower in WKY rats than in SH rats. ACE activities in plasma, striatum and hypothalamus of SH and WKY rats did not differ. After short-term lithium treatment (4 mEq/kg), plasma ACE activity was significantly reduced only in the SH animals although ACE activities in pituitary, striatum or hypothalamus remained unaffected in the SH animals. The results suggest that the antihypertensive effect of lithium in SH animals may be related to decreased plasma ACE activity.
Effect of phospholipid enrichment on nystatin action: differences in antibiotic sensitivity between in vivo and in vitro conditions.
Polyene-nystatin had a selective effect on the transport of glutamic acid and lysine in phosphatidylcholine-, or phosphatidylethanolamine-enriched cells of Saccharomyces cerevisiae. However, liposomes prepared from lipid extracts from the same cells did not mimic the results of in vivo studies. Our in vitro results demonstrated that factors other than sterols, e.g. phospholipid enrichment, protein lipid interactions and lipid bilayer asymmetry may also affect the overall susceptibility of polyene antibiotics.