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Biomedical subjects

S E Martin

Publications and source records attributed to S E Martin.

At least 145 records · Page 8Linked to original sources
PubMed1980

Ribosome assembly during recovery of heat-injured Staphylococcus aureus cells.

The process of ribosome formation during repair of sublethal heat injury was examined in Staphylococcus aureus. Sublethal heating of this organism results in the degradation of the 30S ribosomal subunit and alteration of the 50S subunit. Cells recovering from sublethal injury were examined for changes with time in the sedimentation and electrophoretic properties of ribonucleoprotein particles and ribonucleic acid, respectively. When cells were allowed to recover in [3H]uridine, the label could be followed into ribonucleic acid species that coelectrophoresed with 23S and 16S ribonucleic acid. Three ribonucleoprotein particles (49S, 36S, and 30S) were isolated from repairing cells by sedimentation through sucrose gradients. Polyacrylamide gel electrophoresis showed that the 49S particle contained 23S ribonucleic acid, the 36S particle contained both 23S ribonucleic acid and 16S precursor and mature ribonucleic acid, and the 30S particle contained 16S and precursor 16S ribonucleic acid. Particles with similar sedimentation properties were found in unheated cells.

Bacterial Proteins↗
PubMed1980

Plasmic degradation of crosslinked fibrin. I. Structural analysis of the particulate clot and identification of new macromolecular-soluble complexes.

Plasmic degradation of crosslinked fibrin has been studied to identify the proteolytic cleavages that convert the clot into a soluble lysate and also to identify the derivatives that are likely to circulate during clot dissolution. Initial polypeptide chain cleavages do not disrupt the solid clot matrix. With continued exposure to plasmin, high molecular weight derivatives are produced that remain attached to the clot by noncovalent forces. Further degradation then results in the liberation into solution of several large, noncovalently bound complexes. Progressive degradation of the largest, initially liberated complexes to the terminal derivatives, DD/E, DD, and E, occurs in solution after their release from the clot. As the fibrin clot is exposed to plasmin for longer intervals, progressive dissolution occurs, but the structure of the covalently bound insoluble fibrin core, the noncovalently attached derivatives, and the liberated complexes remains constant. Since much of the initially liberated protein is in complexes larger than DD/E, these derivatives probably represent the more prevalent plasmic degradation products of crosslinked fibrin in vivo.

Blood Coagulation↗
PubMed1979

Heat inactivation of catalase from Staphylococcus aureus MF-31.

The effects of heat on catalase from Staphylococcus aureus lysates were examined. Catalase activity increased with increasing concentrations of potassium phosphate buffer, when heated at temperatures between 50 and 65 degrees C for 10 min. Inactivation of catalase by NaCl during heating was demonstrated. Extended heating of S. aureus cells at 52 degrees C resulted in a slight decrease in catalase activity of the resultant lysates. This decrease was more pronounced in the presence of salt. Heating at 62 degrees C caused a decrease in catalase activity, but not complete inactivation. These results implicate the combined effects of heat, and NaCl in the inactivation of catalase from S. aureus. The findings are consistent with the hypothesis that H2O2 may accumulate as a result of decreased catalase activity and be responsible for the decreased colony-forming ability of stressed S. aureus.

Buffers↗
PubMed1979

Catalase activity during the recovery of heat-stressed Staphylococcus aureus MF-31.

Sublethal heating of Staphylococcus aureus produced little loss of catalase activity, but incubation of the injured cells in tryptic soy broth, with or without 10% NaCl added, produced an 85% decrease in catalase activity. Cells recovered in tryptic soy broth demonstrated increases in catalase levels after approximately 5 h, whereas in tryptic soy broth with 10% NaCl the levels remained low for at least 12 h. Thus, the loss of catalase activity during the recovery period was greater than during the heat treatment.

Catalase↗
PubMed1979

Detection of circulating crosslinked fibrin derivatives by a heat extraction-SDS gradient gel electrophoretic technique.

A technique has been developed to identify and quantitate unique plasmic degradation products of crosslinked fibrin in plasma. In this method, fibrin derivatives are extracted by heat precipitation and dissolved with disulfide bond reduction, after which the crosslinked gamma-gamma chain remnants are identified by SDS-polyacrylamide gradient gel electrophoresis and quantitated by densitometric analysis. A heterogenous group of gamma-gamma chains with molecular weights between 100,000 and 76,000 daltons was identified in lysates of crosslinked fibrin during plasmic degradation in vitro. Three stages of crosslinked fibrin degradation have been arbitrarily defined based primarily on the extent of degradation of these gamma-gamma polypeptide chains. As little as 20 microgram of crosslinked fibrin digests added to 1 ml of normal plasma could be detected by the heat-extraction--gel-electrophoresis technique, identifying the gamma-gamma derivatives with molecular weights of 96,000, 86,000, 82,000, and 76,000 daltons. Plasmic derivatives of gamma-gamma chains were not found in normal plasma, but they were identified in the plasma of patients with disseminated intravascular coagulation and deep-vein thrombosis, both before and in increased quantity during successful thrombolytic therapy.

Autoradiography↗
PubMed1978

Responses of human platelets to immunologic stimuli: independent roles for complement and IgG in zymosan activation.

Analysis of the zymosan (Z)-induced human platelet response with washed platelets, fresh agammaglobulinemic plasma, and purified human IgG has identified a previously unrecognized role of IgG in this reaction, in addition to the previously reported requirements for C and fibrinogen. The rate-limiting step involves the assembly of C components on the Z particles and is independent of immunoglobulin. After the heat-labile components (supplied by agammaglobulinemic plasma) are Z bound, Z-specific IgG (apparently antibody) can bind to Z very rapidly, conferring on the previously inactive Z-complement-fibrinogen intermediate the capacity to induce platelet aggregation and serotonin release. The critical function of this Z-bound IgG appears to be in the interaction of the active Z complex with the platelet through Fc receptors, since soluble Fc fragments of each IgG subclass can totally block platelet activation. It is proposed that the human platelet requires a dual, or multi-site, stimulation to become activated during some forms of immunologic injury. These findings may provide some insight into clinical syndromes involving thrombocytopenia and intravascular coagulation during sepsis.

Agammaglobulinemia↗
PubMed1977

Catalase and enumeration of stressed Staphylococcus aureus cells.

The effects of catalase on the enumeration of stressed (heated, reduced water activity, or freeze-dried) Staphylococcus aureus cells on several selective media were examined. The addition of catalase greatly increased the enumeration of stressed cells. The beneficial effects of catalase were most pronounced on those media least efficient in enumeration of stressed staphylococci, showing increases in enumeration of up to 1,100-fold. The effects of catalase appear to be due to the reduced ability of stressed cells to repair and form colonies in the absence of an exogenous decomposer of H2O2. Thermally stressed cells were more sensitive to H2O2 than unstressed cells. During recovery, stressed cells overcame the requirement for catalase. These findings implicate H2O2 as a factor in the failure of certain selective media to adequately enumerate stressed cells and demonstrate that the addition of catalase to these media markedly increases their productivity.

Catalase↗
PubMed1977

Beneficial effects of catalase or pyruvate in a most-probable-number technique for the detection of Staphylococcus aureus.

The effects of the addition of catalase (EC 1.11.1.6) or pyruvate on the enumeration of Staphylococcus aureus in Trypticase soy broth with 10% NaCl were examined using a most-probable-number technique. Addition of catalase or pyruvate to the broth increased enumeration of all heat-stressed S. aureus strains tested. Increases were also observed with nonstressed cells. Catalase and pyruvate were similarly effective when added to Trypticase soy broth-10% NaCl in enumerating staphylococci naturally present in low-temperature-rendered ground-beef samples.

Bacteriological Techniques↗
PubMed1976

Derepressed alloantigen in transplacentally induced lung tumor coded for by H-2 linked gene.

A transplacentally induced lung tumor of strain C3Hf mice grows progressively when transplanted to (C3Hf X A)F1 hybrid mice but not when transplanted to C3Hf recipients. Progressive tumor growth occurs in [(C3Hf X A)F1 X C3Hf] backcross mice inheriting the H-2a haplotype from the F1 parent. Furthermore, radioresistant immunity to the lung tumor can be induced in C3Hf mice by immunization with normal tissue of B10.A and B10.A(2R) but not of B10 or B10.A(5R) strain mice.

Animals↗
PubMed1976

Catalase: its effect on microbial enumeration.

The addition of catalase to the surface of selective medium plates permitted increased enumeration of physically or chemically injured (stressed) microorganisms. Catalase acted by preventing the accumulation of hydrogen peroxide in, or around, injured cells. Heat-injured Staphylococcus aureus cells had decreased catalase activity, and heat-inactivated catalase had no effect on enumeration.

Bacteria↗
PubMed1975

Anti-tumour antibodies in normal mouse sera.

Evidence for the involvement of the immune system in surveillance against nascent tumors was sought by testing whether normal mouse sera were cytotoxic in the presence of rabbit complement for a variety of lymphoid and non-lymphoid tumor-cell lines. Tumour-reactive antibodies were detected in all mouse sera tested, including sera from congenitally athymic (nude) mice. Considerable variation was noted, however, in the levels of naturally occurring antibodies against specific tumor antibodies were identified as being predominantly IgM. The possible relevance of natural anti-tumor antibodies to immune surveilance was discussed.

Animals↗
PubMed1975

Interspecies brain antigen detected by naturally occurring mouse anti-brain autoantibody.

Normal mouse sera contain naturally occurring antibodies that are cytotoxic in the presence of rabbit complement for NB1, a cell line derived from a neuroblastoma adrenal metastasis of a spontaneous ovarian teratoma. The anti-NB1 antibodies can be specifically removed from normal mouse sera by absorption of the sera with homogenized brain tissue of mouse, rat, guinea pig, chicken, and man and by homogenized kidney tissue of mouse and man. The antigen recognized by anti-NB1 naturally occurring autoantibodies, designated mouse brain antigen-2 (MBA-2), is not present on other normal tissues or tumor cell lines tested. MBA-2 is distinct from previously described mouse brain antigens.

Animals↗
PubMed1975

Translational Control of Protein Synthesis in Staphylococcus aureus.

The calculated in vivo polypeptide chain growth rate for Staphylococcus auteus MF-31 grown in nutritionally rich medium assuming all the ribosomes were functional was found to be approximately 16 amino acids/s/ribosome, but decreased to 10.2 amino acids/s/ribosome for cells grown in poor medium. An in vitro analysis revealed that 70S ribosomes isolated from rich medium cells were more active than similar 70S ribosomes derived from cells grown in poor medium. The 30S subunit was found responsible for the increased activity of the rich monosomes, whereas the 50S subunit appeared to be capable of either high or low activity.

Bacterial Proteins↗