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Biomedical subjects

E R Johnson

Publications and source records attributed to E R Johnson.

At least 55 records · Page 3Linked to original sources
PubMed1990

Electron-capture gas chromatography as a sensitive method for measuring subnanogram amounts of cholesterol in saliva and urine.

This is a sensitive method, suitable for measuring subanogram amounts of cholesterol. Cholesterol and the internal standard, epicoprostanol (5-beta-cholestan-3-alpha-ol), are derivatized with pentafluorobenzoyl chloride and detected by electron-capture gas chromatography. The pentafluorobenzoyl esters of cholesterol and the internal standard are easily formed and possess excellent chromatographic and electron-capturing properties. The lower limit of detection of the method, approximately 100 pg injected, is about 500-fold as sensitive as chromatographic methods involving flame-ionization detection. Within-day and between-day coefficients of variation were 4.2% and 8.2%, respectively, for determinations of a urinary cholesterol concentration of 570 micrograms/L (1.47 mumol/L). Such sensitivity permits analysis for cholesterol in (e.g.) physiological fluids, tissue samples, and cell cultures that contain very low concentrations of cholesterol.

Benzoates↗
PubMed1989

Single-dose piperacillin versus triple-dose cefoxitin prophylaxis at vaginal and abdominal hysterectomy.

Two hundred fourteen women having vaginal or abdominal hysterectomy were entered into a prospective, randomized, blind clinical trial comparing a preoperative intravenous dose of piperacillin to three perioperative intravenous doses of cefoxitin given over an eight-hour period. Interregimen clinical, surgical, and outcome variables of the 207 evaluable subjects were statistically similar, but there were significant interprocedure differences in a variety of categories; many benefits exist when vaginal hysterectomy is possible. Efficacy of a single dose of piperacillin was similar to that of three cefoxitin doses. Seven women (3.4%) had major postoperative infection requiring parenteral antimicrobial therapy, two (1.9%) after vaginal hysterectomy and five (4.8%) after abdominal hysterectomy. Three of the latter five infections (60%) occurred after discharge from the hospital. Even with prophylaxis, postoperative anemia was associated with increased frequency of infection at the operative site after both procedures, and diabetes was associated with late infection of the abdominal incision after abdominal hysterectomy.

Adult↗
PubMed1988

Use of progress curves to estimate the co-substrate-to-substrate flow ratio of a symport mechanism. Application to the isoleucine-Na+ symport of mouse ascites-tumour cells and to the lactose-proton symport.

The model envisages two components in the process, whereby Ht equivalents of co-substrate and St equivalents of substrate accumulate in the cellular compartment in time t. The first is the flow through the symport, n equivalents of co-substrate entering or leaving with each substrate equivalent. The second is the basal flow of co-substrate outside the symport. In certain specific circumstances n can be derived by plotting Ht/t against St/t. The principal requirement is that, whereas the ratio of the component flows must change in the interval t, the magnitude of the basal flow must either be zero or constant. The procedure is applied to published observations [West & Mitchell (1973) Biochem. J. 132, 587-592] on the lactose-proton symport of Escherichia coli [n = 1.075 +/- 0.064(7)] and to new observations on the isoleucine-Na+ symport of mouse ascites-tumour cells [n = 1.136 +/- 0.120(18)].

Animals↗
PubMed1987

Single-dose cephalosporin for prevention of major pelvic infection after vaginal hysterectomy: cefazolin versus cefoxitin versus cefotaxime.

Antimicrobial overutilization accelerates the development of bacterial resistance. A prospective, randomized, blinded clinical trial of vaginal hysterectomy prophylaxis was designed to compare the efficacy, safety, and costs of cefazolin with those of cefoxitin and cefotaxime. Sixteen women (7.5%) developed febrile morbidity only, 10 (4.7%) developed major pelvic infection requiring parenteral antimicrobial therapy, and neither clinical nor laboratory adverse reactions of significance were observed. Anemia, diabetes, and additional surgical procedures were associated with a significantly increased incidence of postoperative infection; no regimen was more protective for women with or without these risk factors. Infections almost doubled hospital stay and the charges for health care. Diagnosis-related group reimbursement would have been more than $1,300 less than the mean hospital charge for women who developed infection. Utilizing cefazolin for prophylaxis and reserving cefoxitin and cefotaxime for therapy is cost and antimicrobial efficient.

Adult↗
PubMed1987

Explanation of pressure effects on a nitrogen dioxide (NO2) sampler.

When nitrogen dioxide (NO2) samplers were exposed at several reduced pressures, it was found that the sampling rate was correspondingly decreased; that finding did not agree with accepted diffusional theory. When the experiments were repeated using water vapor as the gas and molecular sieve as the sorbent, the observed sampling rates were in very good agreement with diffusional theory. These findings demonstrated that the pressure effect was not common to all diffusional samplers and suggested that there might be an alternate explanation for the results with NO2-triethanolamine (TEA). The best possibility appeared to be the dehydration of TEA that takes place at reduced pressures. That this is a very significant factor was demonstrated by simultaneous exposure to identical concentrations of NO2 at 1 atm and 50% or 0% relative humidity. In dry air the sampling rate was equivalent to that found previously at about 1/10 atm. The earlier results can be satisfactorily explained as indirect rather than direct effects of reduced pressure.

Diffusion↗
PubMed1987

Determination of the cleavage specificity of Streptomyces griseus protease B in the presence of guanidinium chloride.

Streptomyces griseus protease B (SGPB), a Pronase enzyme, has been shown to be stable and active in the presence of 6.0 M guanidinium chloride (Siegel, S. et al. (1972) J. Biol. Chem. 247, 4155-4159). In order to determine the cleavage specificity of this unusual enzyme under denaturing conditions, 12 peptides of known amino acid sequence were hydrolyzed by SGPB in the absence and presence of 6.0 M guanidinium chloride. The new N-terminal amino acids produced by the action of SGPB were dansylated and quantitatively identified by reverse phase HPLC. The results indicate that SGPB retained its cleavage specificity for phenylalanyl, tyrosyl, tryptophanyl, and leucyl peptide bonds in the presence of 6.0 M guanidinium chloride. Of these peptide bonds, SGPB exhibited a greater cleavage preference for phenylalanyl and tryptophanyl bonds, which was relatively unaffected by the presence of the denaturant. The SGPB-catalyzed cleavages of the leucyl peptide bonds examined (Leu-Met, Leu-Arg, Leu-Val, Leu-Thr, and Leu-Ile) were substantially decreased under denaturing conditions, while Leu-Gly bond cleavage by SGPB was virtually unaffected by denaturant. The demonstrated predictability of the catalytic preference of this unusual protease for phenylalanyl, tyrosyl, tryptophanyl, and leucyl-glycine peptide bonds under denaturing conditions enhances its utility in the site-specific proteolysis of insoluble or otherwise proteolysis-resistant polypeptide substrates.

Amino Acid Sequence↗
PubMed1985

Ceftriaxone and cefazolin prophylaxis for hysterectomy.

Two hundred and twenty-five women scheduled for elective hysterectomy were entered into a prospective, comparative, randomized, double-blind clinical trial of antibiotic prophylaxis; 117 had vaginal hysterectomy and 108 had abdominal hysterectomy. They were given a 1 gram preoperative dose of ceftriaxone, an investigational cephalosporin or three 1 gram parenteral doses of cefazolin over a 16 hour period. Antibiotic concentrations were measured in serum and vagina, myometrium, fallopian tube or ovary and mean ceftriaxone concentrations were consistently higher than those of cefazolin. Both regimens were safe, well tolerated and equally effective at preventing major postoperative infection. Diabetes increased the risk for infection regardless of regimen and surgical approach (p = 0.009) and specific risk factors were identified for women undergoing vaginal hysterectomy. The incidence of infection was 1.7 per cent after vaginal hysterectomy, significantly lower than the 7.4 per cent observed after abdominal hysterectomy (p = 0.039). Several of the clinical and surgical variables were identified that could explain this difference.

Adult↗
PubMed1984

Cefoperazone and cefoxitin prophylaxis for abdominal hysterectomy.

One hundred one women undergoing elective abdominal hysterectomy were given perioperative cefoperazone or cefoxitin in a prospective randomized blinded study. Both regimens were well tolerated and no significant toxic or allergic manifestations were observed. Interrelationships between antimicrobial concentration in serum and pelvic tissues, intraoperative cardinal ligament cultures, febrile morbidity, and major postoperative infection were determined. At uterine removal, mean cefoperazone concentrations in serum (56.1 micrograms/mL) and pelvic tissues (18.6 micrograms/g) were significantly higher than mean concentrations of cefoxitin, ie, 16.1 micrograms/mL and 8.1 micrograms/g, respectively (P less than .001). The incidence of major postoperative infection was 6% or less with both regimens. Perioperative prophylaxis significantly reduced the incidence of this infection. When it did develop, however, it continued to cause significant morbidity, prolonging hospital stay a mean of more than four days (P less than .001) and increasing the hospital bill a mean of almost $1500 (P less than .001).

Adult↗
PubMed1983

The liver and circulating thyroid hormones.

The liver plays a major role in modifying the total circulating hormone concentrations of thyroxine and triiodothyronine by secretion and degradation of carrier proteins. It also is a major site of peripheral conversion, degradation, and excretion of thyroid hormones. We review the liver's role in thyroid hormone physiology and summarize the changes in circulating thyroid hormone concentrations in various liver diseases.

Carcinoma, Hepatocellular↗
PubMed1976

Formation of three-dimensional structure in protein fragments. Reactivation of reduced hen egg lysozyme fragment 1-127.

Regeneration of enzymic activity from reduced hen egg lysozyme peptide 1-127 was effected with a glutathione oxidation-reduction buffer. The rate of regeneration was nearly as great for peptide 1-127 as for reduced lysozyme itself, and the yields were the same (greater than 80%). The regenerated fragment 1-127 was shown to be indistinguishable from fragment 1-127 before reduction by ion exchange chromatography, amino acid analysis, polyacrylamide gel electrophoresis, and disulfide analysis. These results show that the COOH-terminal dipeptide Arg-Leu is not essential for the acquisition of the native three-dimensional structure of lysozyme.

Amino Acids↗
PubMed1976

An evaluation of the Australian beef carcase appraisal system.

The australian Beef Carcase Appraisal System (ABCAS) which evaluates the commerical worth of carcases by scoring fat percentage, estimated from carcase weight and fat thickness, and by scoring muscle weight, estimated from rib-eye area (REA) and carcase length (CL), was used on 45 steer carcases. Scores were related to carcase components determined by total dissection. ABCAS underestimated fat percentage in 44 of the 45 carcases, the degree increasing with carcase fatness. In 26 of the 44 carcases (59.1%) fat was underestimated by over 7%. Twenty-nine of the 45 carcases (64.4%) received more points for the ABCAS estimates of fat percentage than for dissected values. Nine (20.0%) received the same score for the estimate but in 7 of these this was the minimum score for overfatness. Seven carcases only (15.6%) scored less for estimated fat percentage, 6 of these resulting from under-estimations on the ABCAS scale. Nine carcases which should have been penalised for overfatness were penalised for underfinish. ABCAS adjustments to estimated fat percentage for carcase weight were contradicted because of the small (0.03) but highly significant positive regression of fat percentage on carcase weight. ABCAS scores for carcase muscle, based on REA and CL were neither closely nor consistently related to dissected muscle percentage. The range of dissected muscle in the fat-free carcase (72-81%) was not accurately reflected by the ABCAS points score range (14-46). REA and CL were not satisfactory predictors of carcase muscle. It is concluded that differences in weight or percentage of muscle between carcases at constant fat-free carcase weight may be too small to determine accurately using current prediciton parameters. A useful estimation of the commercial value of a carcase may be based on cold carcase weight and fat thickness at the 10th rib. Two equations utilising these measurements are given for estimating fat percentage and muscle weight.

Adipose Tissue↗