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Biomedical subjects

J Das

Publications and source records attributed to J Das.

At least 145 records · Page 8Linked to original sources
PubMed1978

Endotoxin-induced changes in human platelet membranes: morphologic evidence.

Interaction between human platelets and bacterial endotoxin was studied in vitro with transmission and scanning electron microscopy. Washed human platelets, whose aggregation was blocked with apyrase, were incubated in a plasma-free medium containing crude endotoxin that had previously been complexed with copper. Thirty minutes of incubation resulted in adherence of endotoxin particles to the platelet surface, breaks in the platelet plasma membrane with apparent attempts at repair, pseudoped formation, and centralization of platelet organelles. Copper appeared to potentiate these phenomena, since neither Cu2+ at low concentrations nor endotoxin alone altered the morphology of the platelet membrane. This platelet-endotoxin interaction may be an intermediary step in the detoxification and clearance of endotoxin from the plasma.

Blood Platelets↗
PubMed1977

Host cell and ultraviolet reactivation of ultraviolet-irradiated Mycoplasmaviruses.

The mycoplasma Acholeplasma laidlawii was shown to have mechanisms for both host cell and ultraviolet (UV) reactivation of UV-irradiated mycoplasmaviruses. Host cell reactivation was examined by comparing the survival abilities of UV-irradiated double-stranded deoxyribonucleic acid mycoplasmavirus plated on both untreated and on acriflavine-treated cells. Acriflavine treatment inhibited cell exision repair. Decreased survival on the acriflavine-treated cells demonstrated host cell reactivation. UV reactivation was studied by comparing the survival of UV-irradiated virus plated on untreated cells with its survival on cells that received a small UV dose before plating. The UV-irradiated cells gave increased virus survival, showing UV reactivation. Similar experiments with a single-stranded deoxyribonucleic acid mycoplasmavirus showed that this virus could be UV reactivated, but not host cell reactivated.

Acholeplasma laidlawii↗
PubMed1976

Replication of mycoplasmavirus MVL51: attachment of MVL51 parental DNA to host cell membrane.

The replication of the single-stranded circular DNA of MVL51 mycoplasmavirus has been studied with respect to the roles of free and membrane-associated viral DNA intermediates. Replication involves the formation of parental replicative intermediate (RF) molecules on, at most, two to three membrane sites per cell, symmetric RF replication at the membrane and apparent asymmetric RF replication in the cytoplasm leading to single-stranded progeny chromosomes.

Acholeplasma laidlawii↗
PubMed1976

Characterization of an Acholeplasma laidlawii variant with a REP- phenotype.

An Acholeplasma laidlawii variant has been isolated that has a REP- phenotype. The properties of this variant, relative to parental cells, are: (i) it exhibits no change in cell growth kinetics; (ii) it does not propagate single-stranded deoxyribonucleic acid (DNA) mycoplasmaviruses but does propagate double-stranded DNA mycoplasmaviruses; (iii) it converts parental circular single-stranded mycoplasmavirus DNA to double-stranded replicative forms that are not replicated further; (iv) it exhibits no change in host modification and restriction; and (v) it has an increased ultraviolet light sensitivity. The REP- isolate is the first stable mycoplasma variant to which a physiological defect has been attributed.

Acholeplasma laidlawii↗
PubMed1976

Replication of mycoplasmavirus MVL51. IV. Inhibition of viral synthesis by rifampin.

The effect of rifampin on the replication of MVL51, a bullet-shaped mycoplasmavirus with single-stranded circular DNA of molecular weight 2 X 10(6), has been examined in a rifampin-resistant host cell. Rifampin does not block the early steps in MVL51 infection but does decrease the total amount of parental viral DNA taken up. The single-stranded parental viral DNA that enters the cell is found in membrane-associated, double-stranded DNA replicative forms I and II. Rifampin had no significant effect on the synthesis of progeny viral DNA RFI and RFII early in infection and SSI (single-stranded progeny viral chromosomes) later in infection. The rifampin block in virus synthesis was found to be in the step converting SSI into assembled virions. Rifampin was shown to affect the synthesis of virus-specific RNA, Which suggests that viral transcription is necessary for virion assembly.

Acholeplasma laidlawii↗
PubMed1976

Replication of mycoplasmavirus MVL51. III. Identification of a progeny viral DNA-protein intermediate.

Intracellular replication of the non-lytic single stranded circular DNA mycoplasmavirus MVL51 has been shown to involve three DNA intermediates: RFI, RFII and SSI. Growth in Eagle's basal medium, rather than richer tryptose medium, has allowed the identification of an intermediate between nascent progeny chromosomes (SSI) and mature virus. This intermediate is a protein associated form of SSI.

Acholeplasma laidlawii↗