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Biomedical subjects

B M Chassy

Publications and source records attributed to B M Chassy.

At least 55 records · Page 3Linked to original sources
PubMed1973

Growth of Dictyostelium discoideum in the presence of antibiotics.

Cultures of the amoeboid slime mold, Dictyostelium discoideum, were grown in the presence of various antibiotics and antimetabolites. Results indicate that many antibiotics may be used in amoeba cultures to help minimize contamination (for example: polymyxin B, kanamycin, tetracycline, neomycin, oxacillin, ampicillin, cephalothin, and erythromycin). A few potent antibiotics were found to be unsuitable (colistin, nystatin, amphotericin B, actinomycin, and cycloheximide); the mechanisms of the inhibitions observed were not investigated further.

Anti-Bacterial Agents↗
PubMed1972

Cyclic nucleotide phosphodiesterase in Dictyostelium discoideum: interconversion of two enzyme forms.

An extracellular cyclic nucleotide phosphodiesterase was isolated from either growing cultures or aggregating amoebas of Dictyostelium discoideum. The enzyme is released in a form with a low Michaelis constant (15 micromolar) and spontaneously undergoes a slow conversion to a less active form with a high Michaelis constant (2 mnillimolar). Inactivation was prevented or reversed by use of Cleland's reagent, dithiothreitol. The two enzyme forms may be part of a mechanism for control of concentration of cyclic adenosine monophosphate.

Chemical Phenomena↗
PubMed1972

Inhibition of aggregation and differentiation of Dictyostelium discoideum by antibodies against adenosine 3':5'-cyclic monophosphate diesterase.

A specific antibody directed against adenosine 3':5'-cyclic monophosphate diesterase (c-AMP diesterase; EC 3.1.4.c), which is secreted by the amoeboid slime mold, Dictyostelium discoideum, was prepared in rabbits. Purified gammaglobulin fractions that contain the antibodies inhibited the activity of cAMP diesterase preparations in vitro and interfered with aggregation and development in vivo. While cells that were treated with antibody were unable to aggregate because of the inability to destroy cAMP, they aggregated normally when washed free of antibody.

Animals↗
PubMed1971

Use of a fiber optic probe for spectral measurements and the continuous recording of the turbidity of growing microbial cultures.

This paper describes the properties and use of a fiber optic probe as an attachment to a spectrophotometer and its use for measurements in solutions and turbid suspensions. Measurements of a standard were identical when a spectrophotometer equipped with the probe was used or when a spectrophotometer was used in a conventional manner. The probe was calibrated for turbidimetric measurements with microorganisms by relating the apparent absorbancy measured on the spectrophotometer to the dry weight of each species of organism. Continuous measurements were made of the turbidity of growing cultures of Escherichia coli, Streptococcus mutans, and Saccharomyces cerevisiae. Transient changes in cell mass were observed in some cultures during continuous monitoring of growth. The data were recovered in a manner which allowed direct computer processing.

Brain↗
PubMed1969

The acrasin activity of 3',5'-cyclic nucleotides.

3',5'-Cyclic nucleotides are acrasins for the cellular slime mold, Dictyostelium discoideum; they have chemotactic activity on the myxamoebae at very low concentrations. However, not all cyclic nucleotides can evoke the adhesiveness necessary for aggregate formation. 2',3'-Cyclic nucleotides and dibutyrylcyclic adenosine monophosphate are not acrasins, though they enhance the rate of differentiation and morphogenesis. The addition of 3',5'-cyclic nucleotides to agar test plates stimulates the rate of morphogenesis. While the stimulatory effect of cyclic nucleotides is concentration-dependent, it is fairly uniform between pH 5 and 7, with an optimum at pH 6. The acrasins may be metabolized by extracellular phosphodiesterase to 5'-nucelotides which may then stimulate differentiation and morphogenesis.

Adenine Nucleotides↗