Search PubMed⌕ Search

Biomedical subjects

L Daneo-Moore

Publications and source records attributed to L Daneo-Moore.

84 records · Page 5Linked to original sources
PubMed1972

Morphokinetic reaction of cells of Streptococcus faecalis (ATCC 9790) to specific inhibition of macromolecular synthesis: dependence of mesosome growth on deoxyribonucleic acid synthesis.

The application of quantitative electron microscopy to thin sections of cells of Streptococcus faecalis specifically inhibited for deoxyribonucleic acid (DNA), ribonucleic acid, and protein synthesis shows that septal mesosomes (i) increase in size when protein synthesis is inhibited by at least 80% while DNA synthesis proceeds at no less than 50% of the control rate and (ii) decrease in size when DNA synthesis is inhibited 50% or more during the initial 10 min of treatment. This indicates that fluctuations in mesosome size are dependent on the extent of DNA synthesis. The fluctuations in mesosome areas observed on treatment do not correlate with the kinetics of glycerol incorporation per milliliter of a culture. However, when glycerol incorporation is placed on a per cell basis, a strong correlation is observed between increases in (i) the thickness of the electron-transparent layer of the cytoplasmic membrane and (ii) the amount of glycerol incorporated per cell. It seems that the electron-transparent membrane layer may thicken to accommodate changes in lipid content when protein and lipid synthesis are uncoupled.

Anti-Bacterial Agents↗
PubMed1972

Influence of macromolecular biosynthesis on cellular autolysis in Streptococcus faecalis.

The addition of several different antibiotics to growing cultures of Streptococcus faecalis, ATCC 9790, was found to inhibit autolysis of cells in sodium phosphate buffer. When added to exponential-phase cultures, mitomycin C (0.4 mug/ml) or phenethyl alcohol (3 mg/ml) inhibited deoxyribonucleic acid synthesis, but did not appreciably affect the rate of cellular autolysis. Addition of chloramphenicol (10 mug/ml), tetracycline (0.5 mug/ml), puromycin (25 mug/ml), or 5-azacytidine (5 mug/ml) to exponential-phase cultures inhibited protein synthesis and profoundly decreased the rate of cellular autolysis. Actinomycin D (0.075 mug/ml) and rifampin (0.01 mug/ml), both inhibitors of ribonucleic acid (RNA) synthesis, also reduced the rate of cellular autolysis. However, the inhibitory effect of actinomycin D and rifampin on cellular autolysis was more closely correlated with their concomitant secondary inhibition of protein synthesis than with the more severe inhibition of RNA synthesis. The dose-dependent inhibition of protein synthesis by 5-azacytidine was quickly diluted out of a growing culture. Reversal of inhibition was accompanied by a disproportionately rapid increase in the ability of cells to autolyze. Thus, inhibition of the ability of cells to autolyze can be most closely related to inhibition of protein synthesis. Furthermore, the rapidity of the response of cellular autolysis to inhibitors of protein synthesis suggests that regulation is exerted at the level of autolytic enzyme activity and not enzyme synthesis.

Alcohols↗
PubMed1971

Effects of essential amino acid starvation in Streptococcus faecalis: structural change in the 50S ribosomal subunit.

The 50S ribosomal subunits obtained from exponential-phase and valine-limited cultures of Streptococcus faecalis 9790 differed in protein content. Approximately 35% of the valine-limited subunits showed protein losses when analyzed by CsCl density centrifugation after formaldehyde fixation. Results of density gradient analysis and of acrylamide gel electrophoresis localized the protein to a "split" subunit fraction. No differences could be detected in the protein contents of 30S subunits from exponential-phase and valine-limited cultures.

Acrylates↗
PubMed1971

Balanced macromolecular biosynthesis in "protoplasts" of Streptococcus faecalis.

Osmotically fragile forms of Streptococcus faecalis 9790 were grown in 0.5 m sucrose- or 0.5 m NH(4)Cl-stabilized medium. The "protoplast" cultures exhibit an average growth rate constant of 0.66 to 0.94 mass doublings/hr. In a variety of experiments, turbidity and the net content of protein, ribonucleic acid (RNA) and deoxyribonucleic acid increase at the same rate, indicating balanced macromolecular biosynthesis. A total of two to three mass doublings was obtained, with no evidence of cell division. After osmotic shock, "protoplast" cultures released 93 to 94% of their RNA content in a form not sedimentable at 12,800 x g for 15 min, in contrast to streptococci, which released 7% of their RNA content after the same treatment.

Ammonium Chloride↗
PubMed1971

Incorporation of radioactive macromolecular precursors into intact cells and osmotically stabilized "protoplasts" of Streptococcus faecalis.

Growing "protoplasts" of Streptococcus faecalis were shown to incorporate newly administered radioactive precursors in the same manner as growing intact streptococci. No observable differences could be found between the size of the leucine precursor pools of the two cultures. The extent of turnover of protein and ribonucleic acid in both "protoplast" and streptococcal cultures appeared to be identical. Finally, the absolute rate of macromolecular biosynthesis was found to be equivalent whether determined on the basis of "new" or "old" label incorporation.

Bacterial Proteins↗
PubMedDate not supplied

Analysis of nutritional shift-up of Streptococcus faecium.

Three-dimensional reconstruction methods were applied to electron micrographs of Streptococcus faecium to study the initiation of cell wall growth sites during a nutritional shift-up experiment. Upon lowering the mass doubling time from 76 to 33 min by the addition of excess glutamate, the formation of new cell wall growth sites was studied in relation to other growth parameters (autolytic capacity, cell number, mass, RNA, DNA and peptidoglycan). The findings from these studies, to be described below, support a model in which new sites are introduced when cells grow to a relatively constant, growth-rate-independent size, while the rate at which sites form and grow increases with growth rate. In this model, chromosome synthesis does not regulate the formation of new sites of cell wall growth, but existing sites cannot be completed until rounds of chromosome synthesis are completed.

Cell Wall↗
PubMedDate not supplied

Does penicillin kill bacteria?.

The thesis is presented that the bactericidal action of penicillin and of other inhibitors of cell wall peptidoglycan synthesis, such as vancomycin and cycloserine, is secondary or tertiary to their ability inhibit specific reactions in the assembly of an osmotically protective cell wall. Examples are given of the inhibition of these reactions, which results in inhibition of cell growth (bacteriostatic action) in the absence of either cellular lysis or rapid loss of viability. Thus, in some instances, inhibitory concentrations of these drugs are, in effect, sublethal; this is true, for example, for Streptococcus mutans, a species of bacteria that is part of the normal flora of the oropharynx and that can cause subacute bacterial endocarditis. On the other hand, the damaging effects of the subminimal inhibitory concentrations of penicillin G on Streptococcus faecalis, a species with an active autolytic enzyme system, can be uncovered and converted to a lytic (and lethal) response by partial inhibition of fatty acid synthesis with low concentrations of cerulenin. Some theoretical and practical implications of the occurrence and inhibition of these secondary lethal consequences are discussed.

Bacteria↗