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Biomedical subjects

J B Baseman

Publications and source records attributed to J B Baseman.

At least 127 records · Page 7Linked to original sources
PubMed1976

Attachment of Mycoplasma pneumoniae to respiratory epithelium.

The attachment of radioisotope-labeled Mycoplasma pneumoniae to hamster tracheal rings in organ culture was examined by radioautography and liquid scintillation counting. Radioautographs of individual rings exposed for 8 h to (3H) thymidine-labeled virulent M. pneumoniae revealed a dense extracellular collection of emulsion grains along the luminal surface of epithelial cells. Similar exposure of rings to isotope-labeled avirulent M. pneumoniae resulted in no accumulation of emulsion grains. The numbers of attached virulent mycoplasmas, as measured by liquid scintillation counting of infected rings, were found to increase in a nearly linear fashion over an 8-h incubation period. Viability of the mycoplasmas and metabolic integrity of the tracheal rings were important for optimal attachment. Pretreatment of rings with neuraminidase or sodium periodate significantly impaired orgainism adherence. These data suggest a specificity of interation between virulent M. pneumoniae and tracheal epithelial cells that can be further examined through the use of isotopically labeled mycoplasmas.

Animals↗
PubMed1976

Interaction of virulent Mycoplasma pneumoniae with hamster tracheal organ cultures.

Exposure of hamster tracheal organ cultures to virulent Mycoplasma pneumoniae leads to alterations in ribonucleic acid (RNA) and protein biosynthesis and metabolism of the respiratory epithelium. An examination of the turnover rates of RNA and protein in infected tracheal organ cultures indicates that the rates of degradation of both prelabeled host cell RNA and protein are similar to those of uninfected controls. Infected tracheal organ cultures shifted to a nonpermissive medium within 24 h after infection and further incubated in the nonpermissive medium for 72 or 96 h behaved as normal uninfected cultures in terms of metabolic precursor uptake. Under these conditions, mycoplasmas remained attached to the respiratory epithelium. Cell membranes prepared from virulent mycoplasmas by several procedures neither attached to nor altered the metabolic activity of tracheal cultures. These data indicate that the intimate contact between virulent mycoplasmas and the respiratory epithelium does not alone account for the subsequent interruption of host cell metabolism but must be accompanied by continued multiplication and biochemical function of attached mycoplasmas.

Animals↗
PubMed1975

Differential effect of hormones on macromolecular synthesis and mitosis in chick embryo cells.

Exposure of serum-deprived confluent monolayers of chick embryo cells to fresh serum results in maximal stimulation of synthesis of RNA and protein followed by increased DNA synthesis and mitosis. The addition of insulin to quiescent cultures effects a similar acceleration of synthesis of RNA and protein, but little stimulation of DNA synthesis and mitosis is evident. However, the simultaneous addition of insulin and hydrocortisone to resting cells causes a significant increase in the rate of DNA synthesis although the level reached is considerably lower than that obtained with serum and still no mitosis occurs. Unexpectedly, insulin plus hydrocortisone prevents maximal synthesis of RNA and protein in contrast to insulin-treated cultures. Nuclear autoradiography and percent mitosis of cells incubated with various regulatory factors indicate that cell heterogeneity exists and is reflected in the metabolic responses of subpopulations to specific regulatory signals.

Animals↗
PubMed1975

Alterations in the metabolism of hamster tracheas in organ culture after infection by virulent Mycoplasma pneumoniae.

Exposure of hamster tracheal rings in organ culture to virulent Mycoplasma pneumoniae organisms leads to alterations in macromolecular biosynthesis and metabolic activity of the respiratory epithelial cells. Avirulent organisms derived from the same parent strain do not produce these effects. During the course of infection by virulent mycoplasmas, tracheal rings show an initial increase in [14C]galactose uptake followed by a significant decline as infection progresses which is also accompanied by abnormal processing of galactose as evidenced by amounts of 14CO2 released. Parallel decreases in the rate of [3H]orotic acid and [3H]amino acid uptake are observed. Within 24 h after infection of tracheal rings by virulent mycoplasmas, inhibition of host cell ribonucleic acid and protien synthesis is evident. Ribonucleic acid synthesis in infected cells, analyzed by gel electrophoresis, is reduced by 80% at 48 h and is negligible by 96 h. The course of mycoplasma infection can be interrupted or reversed by erythromycin after the initial mycoplasma-host cell interaction since addition of erythromycin 24 h or earlier after infection prevents the onset of abnormal orotic acid uptake. However, 48 h after infection, rescue of host cells by erythromycin cannot occur and cytopathology becomes evident. These data suggest that mediation of host cell injury requires continued protein synthesis by attached mycoplasmas, and the primary effect of mycoplasma infection on tracheal organ culture may be at a transcriptional or translational level.

Animals↗
PubMed1975

Carbon sources utilized by virulent Treponema pallidum.

Carbon sources utilized by virulent Treponema pallidum organisms extracted from infected rabbit tissue have been investigated. Utilization of 14C-labeled compounds by T. pallidum was monitored by degradation of these compounds to 14CO2. Experiments have consistently shown that of 22 carbon sources examined, [14C]glucose and [14C]pyruvate are selectively degraded to 14CO2 under the experimental conditions employed. When [1-14C]pyruvate, [2-14C]pyruvate, and [3-14C]pyruvate are tested, virulent T. pallidum preferentially degrade and release the carboxyl group as 14CO2. End product analyses indicate that CO2 and acetate are the major products of pyruvate degradation by T. pallidum.

Acetates↗
PubMed1974

Stimulation by insulin of RNA synthesis in chick fibroblasts.

After the addition of insulin to monolayers of chick fibroblasts previously incubated in serum-free medium, the rates of protein and RNA synthesis increase continuously during the first 8-10 h. Little stimulation of DNA synthesis or mitosis results with the addition of insulin alone in contrast to the addition of fresh serum which stimulates both markedly. The stimulation in RNA synthesis does not result from expansion of the nucleotide pool but is correlated with increases in RNA polymerase activity. All major classes of RNA are stimulated; processing of preribosomal RNA to 28S and 18S and the association of this mature RNA with ribosomes appear to occur normally. The kinetics of stimulation of 5S RNA differ from those of the synthesis of 4S and of ribosomal RNA. Insulin and serum appear to affect the synthesis or stability of certain transcripts differentially.

Animals↗
PubMed1974

Purification of Treponema pallidum from Infected Rabbit Tissue: Resolution into Two Treponemal Populations.

Virulent Treponema pallidum organisms, extracted from infected rabbit testes, were subjected to velocity sedimentation in discontinuous gradients of Hypaque, a high density, low viscosity material. After centrifugation of extracts at 20 C for 45 min at 100,000 x g, treponemes separated into two distinct bands based upon their relative velocities, although some variation was observed in the densities of the two bands and the number of treponemes per band. Rabbit tissue components sedimented more rapidly. Dark field and electron microscopy of preparations after velocity sedimentation indicated that treponemes retained general structural characteristics and no tissue contamination occurred in the treponemal fractions. Purification of treponemes in Hypaque resulted in their loss of motility and infectivity based upon animal inoculation. Antigenicity with respect to reactivity with antibody was preserved as shown by the high fluorescence intensity of treponemes in the fluorescent treponemal antibody adsorption test.

Journal Article↗
PubMed1974

Diphtheria pathogenesis in Guinea pig tracheal organ culture.

The effect of diphtheria toxin on guinea pig trachea in organ culture was examined to measure the susceptibility of respiratory epithelial cells to toxin action. Exposure of individual tracheal rings to toxin resulted in cessation of protein synthesis as well as the development of cytopathology within a few hours. Continued incubation led to further inhibition of protein synthesis and extensive disorganization of the epithelial layer. Other inhibitors of protein synthesis were monitored for their effect on the structural integrity of tracheal cells but were found incapable of eliciting similar histopathology. Early after its addition, toxin at minute concentrations possessed cytotoxic properties as well as the ability to inhibit protein synthesis. Interpretation of these data is correlated with current information on the structure and activity of diphtheria toxin.

Journal Article↗
PubMed1974

Protein synthesis by Treponema pallidum extracted from infected rabbit tissue.

Virulent Treponema pallidum organisms, extracted from infected rabbit testes, incorporated amino acids into protein. A temperature of 34 C and a pH of 7.6 were optimal for protein synthesis, which was linear during in vitro incubation for 24 h. Selective inhibition of protein synthesis by erythromycin as judged by the incorporation of radiolabeled amino acids and radioautography demonstrated that treponemes were actively synthesizing proteins. Since addition of various sera and ultrafiltrates to the basal incubation mixture did not stimulate the level of protein synthesis, it was uncertain whether treponemes synthesized protein at a maximal or endogenous rate. Based upon the size of the unlabeled amino acid pool contained in infected testicular extract, it appeared that virulent treponemes utilized the majority of amino acids for protein synthesis but at varying efficiency.

Amino Acids↗
PubMed1970

Action of diphtheria toxin in the guinea pig.

The blood clearance and distribution in the tissues of (125)I after intravenous injection of small doses (1.5-5 MLD or 0.08-0.25 microg) of (125)I-labeled diphtheria toxin has been followed in guinea pigs and rabbits and compared with the fate of equivalent amounts of injected (125)I-labeled toxoid and bovine serum albumin. Toxoid disappeared most rapidly from the blood stream and label accumulated and was retained in liver, spleen, and especially in kidney. Both toxin and BSA behaved differently. Label was found widely distributed among all the organs except the nervous system and its rate of disappearance from the tissues paralleled its disappearance from the circulation. There was no evidence for any particular affinity of toxin for muscle tissue or for a "target" organ. Previous reports by others that toxin causes specific and selective impairment of protein synthesis in muscle tissue were not confirmed. On the contrary, both in guinea pigs and rabbits, a reduced rate of protein synthesis was observed in all tissues that had taken up the toxin label. In tissues removed from intoxicated animals of both species there was an associated reduction in aminoacyl transferase 2 content. It is concluded that the primary action of diphtheria toxin in the living animal is to effect the inactivation of aminoacyl transferase 2. The resulting inhibition in rate of protein synthesis leads to morphologic damage in all tissues reached by the toxin and ultimately to death of the animal.

Amino Acids↗
PubMed1969

Terminal electron transport in Leptospira.

The cytochrome content of three leptospiral strains grown in several media was investigated after it was shown that respiratory inhibitors suppressed oxygen consumption of a water isolate, B(16), and that two pathogenic serotypes, pomona and schueffneri, were active catalase producers, whereas B(16) lacked catalase activity. Reduced minus oxidized difference spectra disclosed cytochromes of the a, c, and c(1) types in all strains. Although no spectral evidence suggested the existence of cytochrome b components, they could have been masked by cytochrome c, and their presence cannot be ruled out. Carbon monoxide difference spectra revealed peaks indicative of a cytochrome oxidase of the o type in all strains. Carbon monoxide spectra further suggested that a cytochrome a oxidase, possibly a(1) or a(3), and a pigment with absorption spectra different from those of previously characterized cytochromes existed in the two pathogens and not in the water isolate. Physiological reduction of the cytochromes by various metabolic substrates implied that the cytochrome system in Leptospira was functional. No effect of the various growth media on the cytochrome patterns of the three strains was observed, indicating that all three strains were capable of synthesis of cytochrome components and did not require heme prosthetic groups present in serum.

Azides↗
PubMed1969

Intermediate energy metabolism of Leptospira.

Metabolic studies were performed on three representative serotypes of Leptospira: a water isolate designated B(16) and two pathogenic serotypes, pomona and schueffneri. Examination of whole cells of B(16) for their ability to oxidize various substrates revealed that oleate significantly stimulated oxygen uptake. The respiratory quotient of 0.7 implied that oleate was degraded to carbon dioxide and water. Other substrates, such as carbohydrates, alcohols, intermediates of the citric acid cycle, and short-chain acids, including selected amino acids, did not stimulate endogenous respiration of whole cells. No oxygen uptake could be measured when cell-free extracts were tested with the substrates used with whole cells. Enzymatic analyses of cell-free extracts of the three strains demonstrated enzymes of the citric acid cycle, enzymes of the glycolytic and pentose pathways, and the general acyl coenzyme A dehydrogenase required for beta-oxidation of fatty acids. Strain B(16) and the two pathogenic serotypes appeared to possess similar metabolic capabilities. Enzymatic data might also explain the apparent inability of B(16) to oxidize other substrates; kinases necessary for activation of common nonphosphorylated compounds were not detected in leptospiral extracts. These findings emphasized the dependence of leptospiral growth upon long-chain fatty acids.

Cell-Free System↗