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Biomedical subjects

J Das

Publications and source records attributed to J Das.

At least 109 records · Page 6Linked to original sources
PubMed1988

Synthesis and pharmacological evaluation of 5,6-exo-epoxy-7-oxabicyclo[2.2.1]heptane derivatives.

1 alpha,2 beta(5Z),3 beta(1E,3S),4 alpha,5 alpha,6 alpha]-7-[5,6-Epoxy-3- (3-cyclohexyl-3-hydroxy-3-methyl-1-propenyl)-7-oxabicyclo[2.2.1]-hept-2- yl]-5-heptenoic acid (31) and [1 alpha,2 beta(5Z),3 beta(1E,3S),4 alpha,5 alpha,6 alpha]-7-[5,6-epoxy-3-[3-hydroxy-5-(p-hydroxyphenyl)-1- pentenyl]-7-oxabicyclo[2.2.1]hept-2-yl]-5-heptenoic acid (37) were found to be selective TxA2 antagonists at the platelet and pulmonary thromboxane receptors. An efficient stereospecific synthesis of these compounds and a series of structural analogues is described. Compounds 31 and 37 both inhibited the bronchoconstriction induced by arachidonic acid in the anesthetized guinea pig.

Adenosine Diphosphate↗
PubMed1988

Intracellular development of choleraphage phi 149 under permissive and nonpermissive conditions: an electron microscopic study.

Intracellular development of choleraphage phi 149 following infection of Vibrio cholerae and Vibrio eltor cells under different conditions was examined by thin-section electron microscopy. Degradation of the host DNA following infection and formation of mature phage particles inside the infected cells were demonstrated. The concatemeric DNA intermediate formed during intracellular replication of phi 149 DNA in permissive hosts was resolved. In confirmation of biochemical evidence, no concatemeric DNA intermediate was observed for infection in high-phosphate medium.

Bacteriophages↗
PubMed1987

Fast method for two-dimensional electrophoresis of proteins from biological samples.

The method for two-dimensional gel electrophoresis of J. Klose and M. Feller [(1981) Electrophoresis 2, 12-24] has been simplified by reducing the thickness of the gels from 3.5 to 1.1 mm for isoelectric focusing gels and from 3.5 to 0.84 mm for sodium dodecyl sulfate slab gels. Thin gels need less reagents and smaller sample volumes. Cooling of the thin gels during electrophoresis is more effective, which allows the use of higher electric power. Therefore, less time is required for an electrophoretic run (approx 4 h). The resolution increases due to the smaller size of the spots. The time required for staining the gels is reduced from at least 3 days to about 1 h. The method has been tested with a protein sample from the filamentous fungus Fusarium solani.

Electrophoresis, Polyacrylamide Gel↗
PubMed1987

Replication and packaging of choleraphage phi 149 DNA.

The intercellular replication of the circularly permuted DNA of choleraphage phi 149 involves a concatemeric DNA structure with a size equivalent to six genome lengths. The synthesis of both monomeric and concatemeric DNAs during replication of phi 149 occurred in the cytoplasm. The concatemers served as the substrate for the synthesis of mature phage DNA, which was eventually packaged by a headful mechanism starting from a unique pac site in the concatemeric DNA. Packaging of DNA into phage heads involved binding of concatemeric DNA to the cell membrane. A scheme involving sequential packaging of five headfuls proceeding in the counterclockwise direction from the pac site is proposed. After infection under high-phosphate conditions, the concatemeric DNA intermediates were not formed, although synthesis of monomeric molecules was unaffected.

Bacterial Proteins↗
PubMed1986

Contractile behaviour of the human pyelo-ureteral musculature. I. Contraction frequency/force relationship.

405 normal and pathological ureteral and pyelic strips were electrically stimulated according to different schemes. Reflux strips produced stronger contractions than normal ones; transversally excised strips contracted stronger than longitudinal ones. The amplitude of a test pulse after a series of stimuli increased with increasing delay until a constant value (at 30 s). The first contraction after a rest period had a lower latency and higher amplitude ("rest contraction"). The time to peak force of contractions was constant. Elongation of the strips increased the amplitude but not the latency of the contractions. In the discussion the similarities between the contractile behaviour of the pyeloureteral muscle and of the heart are discussed.

Electric Stimulation↗
PubMed1986

Contractile behaviour of the human pyelo-ureteral musculature. II. Repetitive electrical stimulation effects.

In normal proximal and distal pyeloureteral human strips and in pathological reflux or obstructive segments the influence of repetitive electrical stimulation at frequencies between 0.01 and 200 Hz on their contractile behaviour was studied. Between 0.01 and 1 Hz baseline tone and maximum amplitude of contraction were dependent on stimulation frequencies, but some strips showed an irregular response pattern. At frequencies between 1 and 200 Hz half of the strips showed a typical "on" and "off" contraction (at the beginning and end of the stimulus period respectively) separated by a plateau. We consider the "off" reaction to be a response to an ionic displacement at the end of the stimulus. Spontaneous activity was mostly observed in Tyrode solution and in calix and pyelum. Transmural nerve stimulation did not change the contraction patterns.

Electric Stimulation↗
PubMed1986

Cloning and expression in Escherichia coli of a recA-like gene from Vibrio cholerae.

A library containing more than 80% of the Vibrio cholerae genome was constructed by cloning BamH1 restriction fragments into pBR322. Using interspecific complementation of an Escherichia coli recA mutant with plasmids containing the gene bank of V. cholerae, a recA-like gene was identified. The recombinant plasmid, designated as pDP145, contained a 1.45 kb segment of V. cholerae DNA which codes for a protein of molecular weight 39,000. The product of this gene confers methyl methane sulphonate resistance on the E. coli recA mutant, suppresses its ultraviolet (UV) light sensitive phenotype and has proteolytic activity on the phage lambda repressor. Induction of a 39,000 dalton protein in UV-irradiated V. cholerae cells was demonstrated.

Bacteriophage lambda↗
PubMed1986

A computerized experimental set-up for in vitro evaluation of smooth muscle contractility.

A fully automated system is designed and developed for the investigation of in vitro contractility of muscle tissue in response to dose-dependent pharmacologic and/or electrical stimulation. The heart of the set-up is a personal technical computer. It drives the experiment by selecting and changing drug concentrations, by applying electrical stimulation, by sampling the tissue's contractile response and by real-time calculation of results. Parameters of interest are derived and updated for further selection and statistical manipulation. Alpha-numerical or graphical hardcopies may be drawn at any time. Investigator's intervention is limited to preparing perfusing solutions, mounting the muscle tissue strips, deciding test condition parameters, supervising the experimental progress and leading statistical calculations.

Animals↗
PubMed1986

Infection by choleraphage phi 138: bacteriophage DNA and replicative intermediates.

Choleraphage phi 138 contains a linear, double-stranded, circularly permuted DNA molecule of 30 X 10(6) daltons or 45 kilobase pairs. Upon infection, the host DNA is degraded, and synthesis of phage-specific DNA is detectable 20 min after infection. The phage utilizes primarily the host DNA degradation products for its own DNA synthesis. A physical map of phi 138 DNA was constructed with the restriction endonucleases Bg/II, HindIII, and PstI. A concatemeric replicative DNA intermediate equivalent to eight mature genome lengths was identified. The concatemer was shown to be the precursor for the synthesis of mature bacteriophage DNA which is subsequently packaged by a headful mechanism.

Bacteriophages↗
PubMed1985

Characterization and physical map of choleraphage phi 149 DNA.

Choleraphage phi 149 DNA is a linear double-stranded molecule 69 X 10(6) Da or 104 kilobase pairs (kbp). From restriction enzyme analysis, it has been concluded that the DNA is circularly permuted. There are at least three S1 nuclease-sensitive sites along the length of the molecule. These sites represent single-strand interruptions repairable by T4 DNA ligase. A physical map of the DNA has been constructed using the restriction endonucleases BamH1 and BglII.

Bacteriophages↗
PubMed1985

Urethral instability: related to stress and/or urge incontinence?

Urethral instability (pressure variations of more than 15 cm. water during bladder filling) was noted in 12 of 34 women with bladder instability and 13 of 139 with a stable bladder. Of the patients 10 had urge, 5 mixed and 8 genuine stress incontinence, while 1 had enuresis and 1 had recurrent cystitis. A clear correlation between urethral pressure variations and electromyographic fluctuations in the anal and/or urethral sphincter was found in 14 of 17 patients. Only urethral pressure variations of more than 35 cm. water are reported as provoking urgency. Different types of pressure fluctuations are described but no fundamental differences or causative factors were found. A nervous rather than a vascular factor is designated as the main cause for urethral instability.

Adult↗
PubMed1985

Long term oscillation in glycolysis.

To increase the period of glycolytic oscillations in yeast extracts (Saccharomyces uvarum), the dependence of the period on pH, on concentrations of phosphate and enzymes, and on temperature has been studied. Stable oscillatory trans were obtained at a pH value of about 6.5. Increasing the phosphate and decreasing the enzyme concentrations as well as decreasing temperature lengthened the period. By dilution of the extract with buffer while maintaining the metabolite concentrations at their initial level the period could be successively prolonged from 20 min to about 6 h.

Glycolysis↗
PubMed1985

Effect of changes in the osmolarity of the growth medium on Vibrio cholerae cells.

The rate and extent of lysis of Vibrio cholerae cells under nongrowing conditions were dependent on the osmolarity of the growth medium. Gross alterations in cellular morphology were observed when V. cholerae cells were grown in media of high and low osmolarity. The rate of lysis of V. cholerae cells under nongrowing conditions increased after treatment with chloramphenicol. Chloramphenicol-treated V. cholerae 569B cells showed formation of sphaeroplast-like bodies in medium of high osmolarity, but not in low osmolarity. Changes in the osmolarity of the growth medium also regulated the expression of the outer membrane proteins. This regulation was abolished if V. cholerae cells were grown in Pi-depleted medium. Analysis of the lytic behavior and composition of outer membrane proteins of an osmotically fragile mutant strain revealed a similar dependence on the osmolarity of the growth medium.

Cell Membrane↗
PubMed1985

Heterogeneous progeny viruses are produced by a budding enveloped phage.

Infection of Acholeplasma laidlawii cells by the temperate enveloped mycoplasma virus L2 results in production of three morphological forms of progeny L2 virus: L2-I, L2-II, and L2-III. These morphological forms can be separated by velocity sedimentation and agarose gel electrophoresis. The latter technique was used to size the quasi-spherical particles: L2-I is 74 nm, L2-II is 88 nm, and L2-III is 132 nm in diameter. The protein composition of the three L2 forms is the same, although there are differences in protein stoichiometric ratios. L2-I, L2-II, and L2-III have the same 11.8 kilobase pair superhelical DNA genome. However, UV inactivation studies and restriction frequency measurements indicate that L2-I and L2-III each contain 1 genome copy, while L2-II contains 2-3 genome copies.

Acholeplasma laidlawii↗
PubMed1985

Rotational differences in urethral pressure in incontinent women.

Urethral pressure profile measurements are made by means of microtransducers at four different positions in the urethra (anterior, posterior, left and right side). The maximum urethral closure pressure (MUCP) is always highest in the anterior position in stress as well as in urge incontinent women. The functional urethral length shows no differences in the four positions. In all positions the recorded pressures and urethral length are higher in the urge incontinent group than in the stress incontinent group. A decrease of MUCP with age is observed in both groups.

Adult↗
PubMed1985

Urethral and perineal instability.

50 out of 271 female patients showed urethral pressure variations of at least 15 cm H2O during bladder filling. These pressure fluctuations were accompanied by variations in the EMG activity of the anal and periurethral striated musculature. Urethral instability is frequently associated with bladder overactivity and occurs in younger people. Possible pathophysiological mechanisms and implications for therapy are discussed.

Adult↗