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A Zerial

Publications and source records attributed to A Zerial.

28 records · Page 2Linked to original sources
PubMed1979

[Immunostimulating and adjuvant activities of a low molecular weight lipopeptide].

From crude extracts of a Streptomyces strain exhibiting immunopotentiating effects, a tetrapeptide was isolated and its structure established as L Ala leads to D isoGlu leads to L, L Dap comes from Gly. This peptide was devoid of biological activity but its chemical coupling with lauric acid gave a substance endowed with adjuvant and immunostimulating properties. This substance and the corresponding synthetic lauroyltetrapeptide were as active in this respect as the muramyl-dipeptide, thus far considered as the minimal adjuvant-active structure of bacterial cell walls: the presence of a sugar moiety is therefore not a prerequisite for immunopotentiating activities.

Adjuvants, Immunologic↗
PubMed1978

Glycolipids stimulate DNA polymerase activity in a DNA-membrane fraction and in a partially purified polymerase system extracted from pneumococci.

We have assayed the ability of various lipids to affect DNA polymerases activity in a DNA-membrane complex extracted from Streptococcus pneumoniae by the Sarkosyl-M-band technique. In addition, to determine which DNA polymerases were affected by the lipids, we partially purified three DNA polymerase activities from cell lysates, the first such demonstration outside of Escherichia coli and Bacillus subtilis. Glycolipids are unique among polar lipids in stimulating the rate and extent of DNA polymerase activity in M-bands and in Sarkosyl lysates from which the M-band is derived. It appears that they exert this stimulatory effect, in part, by removing (neutralizing) detergent molecules which act as inhibitors, as well as by substituting for the detergent, thereby creating a favorable environment for the polymerases involved in DNA synthesis. That the stimulatory effect is not simply a detoxification of the detergent was shown by two observations. One, phospholipids, although interacting with Sarkosyl and therefore "potentially" capable of detoxifying the system, did not stimulate DNA polymerase activity in vitro. Two, glycolipids were capable of stimulating the activity of at least two DNA polymerases partially purified from cell lysates in the absence of any Sarkosyl. The stimulatory effect was greater for a polymerase that had four characteristics similar to those observed with polymerase III in other organisms.

DNA, Bacterial↗
PubMed1977

Membrane fusion: studies with a calcium-sensitive dye, arsenazo III, in liposomes.

Fusion between vesicles, cells, or organelles may be defined as confluence of two membrane-bound compartments without access of their solutes to external milieu. To study fusion by this criterion, we have trapped the metallochromic calcium-sensitive dye, arsenazo III (AIII), partially calcium-saturated (AIII-Ca) in one population of liposomes (phoshatidylcholine 90:dicetylphosphate 10), and ethylene glycol-bis(beta-aminoethyl ether)-N,N'-tetraacetate (EGTA) in a second. In such mixtures, interaction of EGTA with AIII-Ca was measured by a large color shift from blue leads to red (decreased absorbance at 660 nm). Fusion of liposomes (but also lysis and diffusion across the membranes) was proportional to these decrements. The exogenous "fusogens," lysolecithin and retinol, were added to liposomes for 5-24 hr at 37 degrees; after rechromatography, measurements were made of total dye, fraction of dye converted from AIII-Ca to AIII, and total lipid. After correction for lysis and diffusion, lysolecithin (200 microng/ml) induced 23% fusion (volume of AIII liposomes confluent with EGTA liposomes) and retinol (300 microng/ml) induced 15%. With one molar percent cortisol (a membrane stabilizer) in the liposome membranes, fusion induced by fusogens was reduced 2-fold. Neither multi-nor unilamellar liposomes fused with each other in the absence of exogenous fusogens, despite wide variations in molar lipid ratios. Results suggest that liposome-liposome fusion is a slow process requiring exogenous fusogens, which may depend upon contributions of other membrane constituents to mimic closely the fusion of natural membranes.

Arsenicals↗
PubMedDate not supplied

Protective activity of tetracycline analogs against the cytopathic effect of the human immunodeficiency viruses in CEM cells.

Tetracycline analogs were evaluated for anti-HIV activity in CEM cells; minocycline and doxycycline were the most active of these in inhibiting the virus-induced cytopathic effect between 7 and 14 days post-infection. The active concentrations (0.3-1.5 micrograms/ml) were devoid of toxicity in uninfected cultures. Virus production, however, was not inhibited, indicating a dissociation between protection against cell death and suppression of virus growth. These protected cells could be maintained in culture for 6-7 weeks, even in the absence of the compounds. After that period, virus production ceased and cells could then be cultivated for several months without loss of viability or reappearance of virus production. As HIV stocks produced in the presence of tetracycline analogs were unable to induce cell death, we suggest that the cytopathogenicity of HIV may be due in some cases to the presence of tetracycline-sensitive contaminating microorganisms.

Cell Line↗
PubMedDate not supplied

Immunostimulating substances from human casein.

Delipidated human casein was digested with trypsin and the enzymatic digest was fractionated on Sephadex G-50. The peptidic fractions were assayed for immunomodulating activity in two in vitro models. Fractions corresponding to molecular weights in the range of 2,000 +/- 600 were found to possess stimulating activity in these models.

Adjuvants, Immunologic↗
PubMedDate not supplied

Comparative effects of an inflammatory reaction on the resistance of mice to bacterial and viral infections.

The induction in mice of a sterile subcutaneous granuloma exerted no influence upon the mortality following their infection with herpes type 1, murine hepatitis or encephalomyocarditis viruses. Attempts to reproduce the resistance -- which has been found to occur as a result of the granulomatous reaction, in the case of bacterial, fungal or protozoa infections and tumour invasions -- by varying the route and timing of the virus inoculation or the strain of mice have failed. We conclude that it is not merely through their inflammatory properties that some non-specific immunostimulating substances enhance resistance against viral infection.

Aging↗