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Biomedical subjects

M Young

Publications and source records attributed to M Young.

At least 19 recordsLinked to original sources
PubMed1992

Purification and characterization of the mouse mammary tumor virus protease expressed in Escherichia coli.

The mouse mammary tumor virus (MMTV) protease gene was cloned into pGEX-2T, an Escherichia coli expression vector containing the glutathione S-transferase coding region of Schistosoma japonicum. The chimeric protein was formed by fusion of the glutathione S-transferase with a hexapeptide which contains a thrombin cleavage site, followed by the MMTV protease. Affinity chromatography on a glutathione-Sepharose 4B column was used to isolate the chimeric protein. After thrombin cleavage, the glutathione S-transferase and the protease were separated by gel filtration chromatography on a Sephadex G-75 column. The overall yield of the protease purification procedure was about 1 mg of protease/liter of culture, and the specific activity was 380 pmol/min.micrograms of enzyme. Like other retroviral proteases, the MMTV enzyme was active as a dimer, showed maximum activity at pH between 4 and 6, and could be inhibited by pepstatin A and a phosphinic acid derivative HIV-1 protease inhibitor. Enzymatic characterization of this protease reveals its broad specificity, showing a clear preference for the oligopeptide substrate mimicking the cleavage site at the amino-terminal end of the capsid protein (kcat/Km = 9725.5 M-1.s-1). The chimeric protein was also an active dimer and showed a similar Km (17 microM) for such an oligopeptide, although its kcat was about 10 times smaller. Autocatalytic processing of the MMTV protease was observed after expression of clones containing the natural cleavage site, as it occurs at the amino-terminal end of the viral protease, instead of the thrombin-sensitive sequence.

Amino Acid Sequence↗
PubMed1992

Mortality after coronary angioplasty and coronary artery bypass surgery (the national Medicare experience).

Mortality rates for Medicare patients who underwent coronary artery bypass surgery were compared with those who had angioplasty or angioplasty and bypass surgery. Two data sets were used for this study: The first contained information on demographic factors, co-morbidities and subsequent mortality on all 96,666 Medicare patients who had bypass surgery or angioplasty in 1985; the second contained additional detailed clinical data collected using the MedisGroups method on a random sample of 2,931 revascularization patients from 6 states. From the national data set 30-day and 1-year mortality rates were 3.8 and 8.2% for 25,423 angioplasty patients and 6.4 and 11.8% for 71,243 bypass surgery patients (p less than 0.001 for both time periods). Mortality rates for the MedisGroups data were 4.4 and 8.5% for the angioplasty patients and 6.5 and 11.9% for the bypass surgery patients. After eliminating patients admitted with a myocardial infarction, mortality rates were 1.9 and 6.0% for 632 angioplasty patients and 5.1 and 10.8% for 1,730 bypass surgery patients. The risk-adjusted relative risk of mortality for bypass surgery versus angioplasty was 1.72 (p = 0.001) for all patients, 2.15 (p less than 0.001) for low-risk patients and 0.90 (p = not significant) for high-risk patients. Results suggest that low-risk patients have better survival with angioplasty because of lower short-term mortality.

Angioplasty, Balloon, Coronary↗
PubMed1992

Skin cancer in an Irish renal transplant population.

One hundred and forty-nine renal transplant patients attending 2 centres in Dublin were examined. Twelve patients (8.1%) were found to have cutaneous malignancy while dysplastic lesions (premalignant and/or malignant) were identified in 34 (22.8%). The prevalence of cutaneous malignancy in this study is substantially greater than that of previous Irish studies. The introduction of cyclosporin A (CyA) as a new and more effective immunosuppressive agent in renal transplantation may in part explain this increase.

Adult↗
PubMed1992

Kinetics of dissolution of gaseous halothane in Krebs-Ringer's solution.

The responses of biological tissues to volatile anaesthetics are commonly studied by incubating specimens in a bath containing dissolved anaesthetic. One accepted technique is to bubble an anaesthetic gas into several incubation chambers simultaneously. To assess the validity of this technique in producing dissolved anaesthetic (the biologically active form) at equal rates among the several chambers, we determined the kinetics of dissolution of halothane gas in three tissue incubation chambers containing Krebs-Ringer's solution. We found that (1) the dissolution kinetics were first-order in all three chambers; (2) the rate of halothane dissolution depended on the gas bubbling rate; (3) even with the same bubbling rates, chamber shapes and chamber volumes, the dissolution rates for the three chambers were not equal, suggesting that dissolution rate depended on small differences in chamber geometry; (4) the dissolution rates could be made equal by adjusting chamber bubbling rates according to calculations involving the first-order rate equation; and (5) the maximum coefficient of variation of dissolved halothane concentration was 9% at 63% approach to equilibrium and 3% at equilibrium.

Carbon Tetrachloride↗
PubMed1992

Physical characterization of the replication origin of the cryptic plasmid pCB101 isolated from Clostridium butyricum NCIB 7423.

The complete nucleotide sequence of a 3484-bp Sau3A fragment, previously shown to carry the replication origin of the Clostridium butyricum NCIB 7423 plasmid pCB101 (6.05 kb), has been determined. Of the four open reading frames (ORF A-D) identified within this fragment, two (B and C) were shown to be encoding by in vitro transcription/translation assays. Evidence was obtained that both polypeptides are required for autonomous replication of the plasmid in Bacillus subtilis. ORF C is immediately preceded by a small ORF (C') that encodes a relatively small polypeptide (50 amino acids) that demonstrates significant homology with RepA of plasmid pLS1. Whereas the ORF C polypeptide (27,100 Da) exhibits no homology to any known protein, that encoded by ORF B (RepB, 43,039 Da) exhibits significant homology with the Rep proteins of the pC194/pUB110 subfamily of single-strand (ss) DNA plasmids, which are widely distributed in gram-positive bacteria. Conserved amino acids include the presumed active site of topoisomerase activity and four cysteine residues in the N-terminus of all Rep proteins compared. The repB gene is preceded by a sequence motif exhibiting substantial homology to the "plus" origins of this family of ss DNA plasmids and was shown to act as a "hot spot" for deletion formation in certain plasmid chimaeras. The compelling suggestion that pCB101 replicates via a rolling circle mechanism was substantiated by the demonstration of ss DNA replication intermediates in B. subtilis cells carrying a pCB101-derived plasmid.

Amino Acid Sequence↗
PubMed1992

Testosterone and 5 alpha-dihydrotestosterone interact differently with the androgen receptor to enhance transcription of the MMTV-CAT reporter gene.

Testosterone and its 5 alpha-reduced derivative 5 alpha-dihydrotestosterone exert different actions in the male during embryogenesis and in postnatal life. Nevertheless the two hormones bind to the same intracellular androgen receptor, and genetic and endocrinological studies in the Tfm mouse suggest that the actions of both hormones are mediated by this single receptor. Previous studies indicate that dihydrotestosterone binds more tightly to the androgen receptor but that the Bmax of binding of the two hormones is the same. To determine whether these differences in binding parameters could explain the mechanism by which the two hormones exert different physiological actions via the same receptor, we introduced a plasmid encoding the androgen receptor cDNA and a reporter plasmid encoding MMTV-CAT into Chinese hamster ovary cells. These cells do not express endogenous androgen receptor and do not convert testosterone to dihydrotestosterone. Therefore, it was possible to examine the relation between the concentration of each of the steroids and reporter gene expression. Both hormones enhanced CAT activity, but dihydrotestosterone was approximately 10 times as potent (half maximal of 0.018 nM) as testosterone (half maximal of 0.2 nM); the maximal activity achieved was the same for the two androgens. These findings are nearly identical to the apparent Kd values for the interaction of the two hormones with the androgen receptor. Although testosterone and dihydrotestosterone may influence the expression of other genes differently, these findings are compatible with a model system in which the differential effects can be explained as a consequence of different binding affinities to the receptor.(ABSTRACT TRUNCATED AT 250 WORDS)

5-alpha-Dihydroprogesterone↗
PubMed1992

Adenocarcinoma of the pancreas with osteoclast-like giant cells: a case report with immunocytochemistry.

Histological examination of a tumor centered in the body of the pancreas of a 65-year-old Iranian man revealed it to have a substantial component in which osteoclast-like giant cells were set within a stroma of pleomorphic mononuclear cells though other areas were composed of conventional adenocarcinoma. Immunocytochemistry was used to investigate the differentiation of the various component cells of the tumor. The carcinoma cells of the usual type expressed epithelial antigens (EMA and cytokeratin). The giant cells expressed vimentin and showed membrane staining with anti-LCA, in common with examples of cells originating from the mononuclear phagocytic system, including normal osteoclasts. The accompanying stromal cells expressed vimentin only. This implies that the giant cells are likely to have their origin in the bone marrow, whereas the mononuclear stromal cells that separate them may represent tumor cells that have lost their epithelial phenotype. The giant cells are therefore an unusual tissue response to the presence of the carcinoma.

Adenocarcinoma↗
PubMed1992

Minimizing the risk of post-operative pyoderma gangrenosum.

A 61-year-old woman with seropositive rheumatoid arthritis developed numerous ulcers due to pyoderma gangrenosum at suture entry/exit sites following an arthroplasty of the right hip when interrupted silk sutures were used to close the skin. When a subsequent arthroplasty was performed on the left hip and subcuticular Dexon sutures were used to close the skin only two small ulcers developed. Sixteen cases of pyoderma gangrenosum developing in surgical wounds have previously been reported. We recommend that surgery in patients with a history of pyoderma gangrenosum is performed when the pyoderma is clinically quiescent, and that subcuticular sutures are used for skin closure, thus avoiding puncturing the skin surface.

Adolescent↗
PubMed1992

Fluoroquinolone supersusceptibility mediated by outer membrane protein OprH overexpression in Pseudomonas aeruginosa: evidence for involvement of a nonporin pathway.

Overexpression of Pseudomonas aeruginosa outer membrane protein OprH led to an 8- to 32-fold increase in susceptibility to chloramphenicol and the quinolones nalidixic acid, norfloxacin, ciprofloxacin, and fleroxacin in comparison with the susceptibility of the wild-type strain H103 grown on Mg(2+)-sufficient medium. This was true regardless of whether OprH overexpression was induced by growth of strain H103 on Mg(2+)-deficient medium, the addition of 5 mM m-toluate to cells containing the cloned oprH gene behind the inducible tol promoter in plasmid pGB25, or mutation in the polymyxin-resistant derivative strain H181. In contrast, OprH overexpression failed to reverse the quinolone resistance phenotype of a nalB mutant. OprH was purified to homogeneity by selective detergent solubilization and fast protein liquid chromatography. The addition of OprH to the solution bathing a black lipid bilayer membrane failed to give rise to an increase in membrane conductance. This suggests that OprH is not a porin but, instead, may cause increased uptake of quinolones and chloramphenicol via a non-porin pathway.

Anti-Infective Agents↗
PubMed1992

Subglottic ulceration and healing following endotracheal intubation in the neonate: a morphometric study.

In neonates, acquired subglottic stenosis is the most serious long-term complication of endotracheal intubation and is due primarily to posttraumatic fibrosis of the infant larynx. We have examined 78 larynges, 75 of which were intubated, from infants ranging in gestation from 22 to 40 weeks, and who survived from a few hours to up to 300 days. Each larynx was morphometrically assessed for the extent of acute injury, indicated by the percentage of epithelial loss, and healing, indicated by the percentage of a subglottic ulcer covered by metaplastic squamous epithelium. Results show that acute injury is almost invariable, and up to 100% of the subglottic epithelium may be lost within a few hours of intubation, but that progression of injury is relatively short-lived. Ulcer healing starts after a few days, rapidly progresses from day 10, and in the majority of cases is complete after 30 days. This study suggests that long-standing acute injury in the subglottis is the exception rather than the rule, even with the endotracheal tube remaining in place.

Humans↗
PubMed1992

An interesting case presentation: a possible new route for perinatal acquisition of Chlamydia.

Chlamydia trachomatis is currently the most common sexually transmitted disease in the United States. The prevalence in pregnant women ranges between 2% and 47%. It is well known that C trachomatis can be transmitted from the genital tract of an infected mother to her newborn infant, causing conjunctivitis or pneumonia or both, along with their longstanding complications. A review of the literature failed to show, however, conclusive evidence of transmission of infection to the newborn infant when the infant was born by cesarean section with intact amniotic membranes. We present a case of a young black woman with a history of chlamydia cervicitis during pregnancy whose infant was delivered by cesarean section because of failure to progress. She gave birth to a healthy term infant who developed ophthalmia neonatorum on the 3rd day of life. Examinations of conjunctival scrapings with direct fluorescent staining (chlamydia MicroTrak) performed on the 1st and 3rd day of life were positive. The initial test was performed because of the maternal history. The infant was mildly symptomatic at the time the study was repeated for confirmation. Our findings strongly suggest the possibility of either transmembrane or transplacental route of infection in the pathogenesis of neonatal chlamydia infection. Further study is needed to confirm this possibility.

Adult↗
PubMed1992

Clinical apnea as an early manifestation of Pneumocystis carinii pneumonia in an infant with perinatal HIV-1 infection.

This article describes the first case of Pneumocystis carinii pneumonia in a human immunodeficiency virus (HIV) seropositive infant in whom apnea was the earliest presenting clinical finding. Pediatricians treating infants with HIV infection need to be aware of this unusual clinical presentation of P carinii pneumonia to avoid a delay in diagnosis and management of this disease.

Apnea↗