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Biomedical subjects

D F Brown

Publications and source records attributed to D F Brown.

At least 163 records · Page 9Linked to original sources
PubMed1972

Assessment of the sanitary effectiveness of holding temperatures on beef cooked at low temperature.

Beef cubes cooked at low temperature were surface inoculated and incubated at 43.3 through 53.3 C to establish temperature limits for growth of staphylococci, salmonellae, and Clostridium perfringens. A greater than 99% reduction in staphylococci was achieved after 6 hr at 48.8 C, of salmonellae at 51.1 C, and of C. perfringens at 53.3 C. There were no survivors of a mixed inoculum of Staphylococcus aureus, Salmonella enteritidis, and C. perfringens after 12 hr at 51.1 C.

Animals↗
PubMed1971

Synthesis and some properties of an actin-like nuclear protein in the slime mold Physarum polycephalum.

A protein was extracted from isolated nuclei of the slime mold Physarum polycephalum which could be labeled with radioactive precursors only during G(2) phase. The native protein was purified by extraction in low-ionic-strength buffer [10 mm tris(hydroxymethyl)aminomethane-hydrochloride] of isolated nuclei and by preparative polyacrylamide gel electrophoresis. It was extracted from isolated nucleoli. Its electrophoretic properties in three different polyacrylamide gel systems, its molecular weight (44,000 +/- 3,000), its precipitability by vincaleucoblastine, a vinca alkaloid, and its aggregation properties suggested that it might be actin. In a direct comparison with slime mold actin purified from the cytoplasm, no difference could be found between the two proteins in all these characteristics. The synthesis of cytoplasmic actin was not found to occur exclusively during G(2) phase. This suggested that nuclear actin was either synthesized independently from cytoplasmic actin or transported into the nuclei exclusively during G(2) phase. The possible role of nuclear actin during intranuclear mitosis is discussed.

Actins↗
PubMed1970

Differential protein synthesis during sporulation in the slime mold Physarum polycephalum.

The size distribution and synthesis of polypeptide chains and the polysome patterns were studied during sporulation of the slime mold Physarum polycephalum, and were compared with nonsporulating controls. The proteins were divided into a 27,000 x g supernatant (buffer-soluble proteins) and a pellet (buffer-insoluble proteins) while still native. The sodium dodecyl sulfate complexes of the denatured proteins were separated on polyacrylamide gels containing urea. The following differences were found between sporulating and nonsporulating cultures. (i) The distribution of the soluble proteins into bands from sporulating and control cultures was the same in stained patterns; however, there was a slight shift toward increased synthesis of larger polypeptide chains in the radioactivity patterns of the soluble proteins in sporulating cultures. (ii) The amount of histones in the sporulating cultures was less than 30% of the values in the controls. Also, histone synthesis was reduced to less than 10% of that in the nonsporulating controls. In addition, proteins in three defined regions, corresponding to molecular weights of 70,000 to 75,000 (I), 55,000 (II), and 41,000 (III), were synthesized in sporulating cultures at a rate at least twice that in controls. Polypeptides corresponding to peaks I and II could be extracted from purified walls of mature spores. (iii) The polysome pattern as revealed by sucrose density centrifugation showed a breakdown of heavy polysomes at 3 hr after illumination, with their reappearance 4 hr later. The latter pattern, however, differed from that of the nonsporulating control in that the amount of light polysomes was reduced. This might account for the reduction in histone synthesis.

Cell Wall↗
PubMed1967

Examination of market foods for coliform organisms.

Food specimens (490) in nine categories were examined for total aerobic plate count and numbers and types of coliform organisms, including the enteropathogenic Escherichia coli (EEC). The total counts were compared with various suggested standards, and a limit of 100,000/g appeared to be a realistic goal, except for certain food types with a high level of natural flora. Plate counts in VRB were compared to counts obtained by isolation by enrichment in LST Broth, and the latter method produced a higher percentage of isolations. The presence of E. coli was determined by use of EC Medium incubated at 44.5 +/- 0.1 C. Only 40.4% of the positive EC tubes, however, contained E. coli. It appeared that a limit of 10 coliform organisms per g as a suggested standard could be met with several types of foods. Isolation of EEC was obtained only three times, or in 0.6% of the specimens.

Enterobacter↗