Biomedical subjects
Publications and source records attributed to B Unger.
After 8 years of comparison to MV, BP reveal no significant difference in early mortality and late survival statistics, yet demonstrated a higher rate of late complications such as endocarditis and perivalvular leak. In conclusion our data indicate that BP are not superior to MV after 8 years of follow-up.
The purpose of this study was to determine the incidence of work-related low back pain (LBP) in physical therapists and to identify common characteristics of therapists who reported work-related LBP. Questionnaires were mailed to a random sample of 500 registered physical therapists. Of the 344 (69%) questionnaires returned, 29 percent reported work-related LBP. The initial onset most frequently occurred between the ages of 21 and 30 years and within the first four years of experience as a physical therapist. Eighty-three percent of the therapists first incurred work-related LBP during treatment of patients, primarily in acute care and rehabilitation facilities. "Lifting with sudden maximal effort" and "bending and twisting" were frequent mechanisms of injury. Further research is necessary to investigate the effect work-related LBP has on productivity and quality of patient care within facilities and to identify preventive measures to decrease the incidence of work-related LBP.
Homologous and heterologous repressor-operator interactions among four different classes of tetracycline resistance determinants have been compared. These are represented by RP1/Tn1721 (class A), R222/Tn10 (class B), pSC101/pBR322 (class C), and RA1 (class D). By the use of the purified repressor proteins of class A (TetRA) and class B (TetRB), operator sequences of all four classes are recognized by both with an identical stoichiometry of four repressor subunits per control sequence, but with different affinities. In vitro transcription has been used to demonstrate regulatory activities of TetRA and TetRB upon all four classes of tet genes. Tetracycline acted as an inducer. A functional relationship among the tet regulatory systems was also shown in vivo by complementation of a class A tetR'-galK fusion mutant with the tetR genes of classes A, B, and C. Repression of tetRA-linked galactokinase was ca. 80% in the presence of tetRA or tetRC, and ca. 50% in the presence of tetRB. Taken together, these results demonstrate heterologous repressor-operator interaction, suggesting close relationships among the four classes of Tcr determinants.
The murein and membrane protein compositions of Caulobacter crescentus strains CB13B1a and CB15 have been characterized, and the influence on cell envelope constituents of culture conditions which affect morphogenesis have been studied. Amino acid and sugar analysis of murein sacculi revealed a simple A1gamma murein configuration typical of gram-negative bacteria. The membranes of C. crescentus had low levels of 2-keto-3-deoxyoctonate relative to enteric bacteria, in addition to the absence of lipid A components (Shapiro et al., Science 173:884-892, 1971; Chow and Schmidt, J. Gen. Microbiol, 83:369-373, 1974). Nevertheless, C. crescentus membranes could be fractionated into inner and outer membrane components by sucrose density gradient centrifugation procedures developed for Escherichia coli. The proteins of the outer membrane were distributed between three major (I, II, and III) and two minor (IV and V) protein classes. Class I proteins were greater than or equal to 74,000 daltons and constituted the primary proteins of the outer membrane. Class I proteins were separated into approximately 50 polypeptides by two dimensional gel electrophoresis; the protein composition of thi s class was affected by culture conditions in both CB13B1a and CB15. Class II (47,000 to 39,000 daltons) and III (20,000 to 11,500 daltons) proteins differed in each strain in composition and response to culture conditions.
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