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Biomedical subjects

S White

Publications and source records attributed to S White.

At least 19 recordsLinked to original sources
PubMed1992

The three-dimensional structures of methanol dehydrogenase from two methylotrophic bacteria at 2.6-A resolution.

The structures of methanol dehydrogenase (MEDH) from two closely related methylotrophic bacteria, Methylophilus methylotrophus and W3A1, have been determined at 2.6-A resolution. The molecule, a quinoprotein of molecular mass of about 138 kDa, contains two heavy (H) and two light (L) subunits of unknown sequence and two molecules of noncovalently associated pyrroloquinoline quinone. The two enzymes crystallize isomorphously in space group P2(1) with one H2L2 heterotetramer in the asymmetric unit. The electron density map of the M. methylophilus enzyme was obtained by multiple isomorphous replacement with anomalous scattering and improved by solvent leveling and electron density averaging. For model building, the amino acid sequence of MEDH from Paracoccus denitrificans for the H subunit and from Methylobacterium extorquens AM1 for the L subunit were used to represent the unknown amino acid sequence. At the present time, 579 and 57 amino acid residues for the large and small subunits, respectively, have been fitted into the map. The phases for MEDH from M. methylophilus were used directly to analyze the W3A1 structure, and both structures were refined to R-factors (where R = sigma[Fo-Fc[/sigma Fo) of 0.277 and 0.266, respectively. The L subunit contains a long alpha-helix and an extended N-terminal segment, both lying on the molecular surface of the H subunit. The H subunit contains eight antiparallel beta-sheets, each consisting of four strands arranged topologically like the letter W. The eight Ws are arranged circularly, forming the main disc-shaped body of the subunit, with some short helices and loops connecting the consecutive Ws, as well as some excursions within and between some of the Ws. The pyrroloquinoline quinone prosthetic group is located in the central channel of the large subunit near the surface of the molecule. The topology of the eight-W folding unit is similar to those of the six- and seven-W folding units previously reported for three other proteins, neuraminidase, methylamine dehydrogenase, and galactose oxidase.

Alcohol Oxidoreductases↗
PubMed1992

Monoclonal antibodies against defined epitopes of the human transferrin receptor cytoplasmic tail.

Three murine monoclonal antibodies (mAbs) against the 61-residue amino-terminal cytoplasmic tail of the human transferrin receptor (TR) have been produced by immunization of mice with recombinant human TR produced in a baculovirus expression system. Mutant human TRs expressed in chick embryo fibroblasts (CEFs) with point mutations or deletions in their cytoplasmic tails have been used to map the epitopes defined by each of the mAbs. One mAb, H68.4, previously shown to block receptor internalization, binds proximal to the carboxy-terminal side of the YTRF internalization signal of TR. The second mAb, H73.2, binds near to the carboxy-terminal side of the H68.4 epitope, whereas the third mAb, 160.1, binds closer to the transmembrane region. H68.4 and H73.2 are auto-antibodies consistent with their epitopes mapping to a region of the human TR that has an identical amino acid sequence to the mouse TR. All three mAbs crossreact with the cytoplasmic tail of Chinese hamster TR. Double labelling of recombinant human TRs on chick embryo fibroblast (CEF) cell membrane preparations with B3/35 and H68.4 antibody-gold conjugates established that receptors in clathrin-coated pits were not labeled with H68.4, implying that associated coated pit proteins may block binding of this mAb.

Amino Acid Sequence↗
PubMed1992

Adrenergic expression in the rat adrenal gland: multiple developmental regulatory mechanisms.

Phenylethanolamine N-methyltransferase (PNMT, EC 2.1.1.28) has been used as a marker to examine development of adrenergic expression in the rat adrenal gland and the putative role of glucocorticoids in this process. PNMT enzymatic activity increases 7-10-fold from birth to postnatal day 35. Immunotitration studies show that PNMT protein only increases 4-5-fold during this same time period. Moreover, the slopes from the immunotitration curves decrease with increasing age. Thus, a more active enzyme with lower affinity for the antiserum appears to be present in the older animals. Quantitative solution hybridization shows that PNMT mRNA increases 2.5-fold from birth through postnatal day 11. Thereafter, it declines, and eventually plateaus at values insignificantly different from birth by postnatal day 25. Northern analysis further shows that two forms of PNMT mRNA are expressed. Adrenal corticosterone remains low from birth through postnatal day 11, but then increases nearly 10-fold by adulthood. The lack of concordance between changes in PNMT activity, protein, and mRNA suggests that adrenergic expression is developmentally regulated at multiple levels; the above provides evidence for both transcriptional and post-transcriptional controls, since changes in PNMT mRNA may differ in both magnitude and direction from changes in PNMT activity and protein during the developmental window examined. These developmental regulatory mechanisms may be in part glucocortocoid-mediated, but corticosteroid control of PNMT gene expression does not appear to be the predominant mechanism of control.

Actins↗
PubMed1992

Proof of differentiative mode of action of all-trans retinoic acid in acute promyelocytic leukemia using X-linked clonal analysis.

Using X-linked clonal analysis, mechanism of action of all-trans retinoic acid (ATRA) was sought in a 16-year-old female with relapsed clonally evolved acute promyelocytic leukemia (APL), who achieved complete remission. On ATRA, metamorphosis of peripheral blood leukemic promyelocytes to mature neutrophils was observed, despite the persistence of t(15;17) in 100% of bone marrow metaphases. DNA was extracted from fractionated serial blood specimens, collected at diagnosis, in first complete remission (CR), relapse, and during ATRA treatment. Using a phosphoglycerokinase (PGK) probe, the patient was heterozygous for both Bgl I and Bst XI PGK polymorphisms. Methylation analysis showed monoclonal leukemic promyelocytes with a polyclonal first CR achieved by standard chemotherapy. Subsequent examination, in relapse, of granulocytes appearing during ATRA treatment showed these to be monoclonal, proving these were derived from the neoplastic clone. The X-linked clonal analysis methodology has provided in vivo evidence of cellular differentiation as the mechanism of action of ATRA. Parallel studies of cytogenetic and clonal analysis showed a regression of the t(15;17) cytogenetic abnormality and return of a polyclonal PGK methylation pattern in 5 weeks, indicating a repopulation of marrow by normal stem cells. As standard cytogenetic techniques are inappropriate for nondividing cells, X-linked clonal analysis provides a marker system to allow insight into mechanism of drug action in malignant hematologic disease.

Adolescent↗
PubMed1992

Correlation of x-ray deduced and experimental amino acid sequences of trimethylamine dehydrogenase.

The amino acid sequence of the iron-sulfur-flavoprotein, trimethylamine dehydrogenase, isolated from the bacterium W3A1 has been deduced from the x-ray diffraction pattern obtained at 2.4-A resolution. This sequence has been compared to portions of the primary sequence derived by gas-phase sequencing of isolated peptides obtained from cyanogen bromide and endoprotease Arg-C and Asp-N digestions of the purified enzyme. A consensus sequence has resulted and is comprised of 729 amino acids with Ala at both NH2- and COOH-terminal positions. The consensus sequence contains 13 cysteine residues. Approximately 80% of the sequence has been confirmed by direct sequencing with approximately 81% agreement with the x-ray deduced sequence. The calculated subunit molecular mass of the apoenzyme is 78,899 Da, in good agreement with published values of approximately 83,000. The anomalous scattering map from the native protein has also been shown to provide accurate information about the positions of most of the weak anomalous scattering centers such as sulfur or phosphorus atoms and to complement x-ray or chemical sequencing methods.

Amino Acid Sequence↗
PubMed1992

Use of the Family CAGE in screening for alcohol problems in primary care.

OBJECTIVE: To establish the reliability and validity of the Family CAGE (an acronym indicating Cut down on drinking; Annoyed by complaints about drinking; Guilty about drinking; had an Eye-opener first thing in the morning), a four-item instrument intended to assess family alcohol-related problems. DESIGN: Two distinct cross-sectional studies using a survey, and in one study, retrospective chart review. PARTICIPANTS: A random sample of 172 adult patients presenting for nonurgent care to a network of family practice settings and a convenience sample of 107 patients who smoked presenting to a university family practice residency training setting. MAIN OUTCOME MEASURES: The Family CAGE was compared with alcohol-related variables and scales measuring psychosocial constructs. In the first study, these scales included the Family Stress and Coping Scale; Profile of Mood States; the Family Problems Checklist; and the Duke/University of North Carolina Mini-Health Profile. Chart review included medical utilization rates and prescription of medications. In the second study, a revised version of the Family CAGE was compared with other scales such as the standard CAGE questionnaire; an "Anomy" Scale; the Catchment Epidemiologic Study-Depression Scale; a global self-assessment of alcohol-related problems; and a self-report of lifetime history of major depression and recent self-limited depression. RESULTS: The Family CAGE showed strong internal consistency reliability, with Cronbach's alpha coefficients of .84 in the first study and .89 in the second. Construct validity was supported by Family CAGE correlations with family stress, family problems, depression, anxiety, individual stress, and marital dissatisfaction. The Family CAGE was strongly correlated with global assessment of family alcohol-related problems, and was superior to this variable in predicting help-seeking behavior. The Family CAGE was also significantly correlated with a higher sick visit rate and more medications prescribed (despite no difference in functional health status). The standard CAGE was correlated with a recent history of self-limited depression, while the Family CAGE was correlated with a lifetime history of major depression. Sensitivity and specificity rates vary depending on the criterion addressed, but a cutoff score of 2 or more appears to offer the best clinical information. CONCLUSION: The Family CAGE appears to be a reliable, valid, utilitarian measure of family alcohol problems. It offers more information than either a single-item global assessment regarding family alcohol-related problems or the standard CAGE questionnaire. The Family CAGE is strongly correlated with other important psychosocial problems, prescription of psychotropic medications, and health-care utilization. It is brief, understandable, and equally effective in interview and self-administered formats.

Adult↗
PubMed1992

Systems versus performance problems: a peer review organization's perspective.

An analysis of Ohio's Medicare data base by the state's Peer Review Organization, using the most common diagnosis-related group in the Medicare population (heart failure and shock), from January 1, 1989 to January 1, 1991, identified 72 cases with confirmed quality-of-care problems. The analysis was performed to determine whether the majority of quality-of-care problems are related to systems or performance deficiencies. Study results indicated that health care workers are being inappropriately blamed for problems that are inherent in the health care system--74% of problems were related to inefficiencies in the health care delivery system, and 26% were determined to reflect performance problems.

Clinical Competence↗
PubMed1992

Anastomotic intimal hyperplasia: mechanical injury or flow induced.

All anastomotic intimal thickening may not be the same, and the underlying mechanism(s) regulating the different types may vary. We investigated the localization of experimental anastomotic intimal thickening in relation to known biomechanical and hemodynamic factors. Bilateral iliofemoral saphenous vein and polytetrafluoroethylene grafts were implanted in 13 mongrel dogs. The distal end-to-side anastomotic geometry was standardized, and the flow parameters were measured. After 8 weeks, seven of 10 animals (group I) with patent grafts were killed and the anastomoses fixed by perfusion. Histologic sections from each anastomosis were studied with light microscopy, and regions of intimal thickening were identified and quantitated with use of oculomicrometry. To characterize the anastomotic flow patterns, transparent silicone models were constructed from castings of the distal anastomosis of three animals (group II), and flow was visualized with use of helium-neon laser-illuminated particles under conditions simulating the in vivo pulsatile flow parameters. Histologic sections revealed two separate and distinct regions of anastomotic intimal thickening. The first, suture line intimal thickening, was greater in polytetrafluoroethylene anastomoses (0.35 +/- 0.23 microns) than in vein anastomoses (0.15 +/- 0.03 microns, p less than 0.05). The second distinct type of intimal thickening developed on the arterial floor and was the same in polytetrafluoroethylene (0.11 +/- 0.11 microns) and vein anastomoses (0.12 +/- 0.03 microns). Model flow visualization studies revealed a flow stagnation point along the arterial floor resulting in a region of low and oscillating shear where the second type of intimal thickening developed. High shear and short particle residence time were observed along the hood of the graft, an area devoid of intimal thickening.(ABSTRACT TRUNCATED AT 250 WORDS)

Anastomosis, Surgical↗
PubMed1992

Single dose ceftriaxone as prophylaxis for sepsis in colorectal surgery.

During the period May 1986 to July 1989, a prospective, double blind, randomized trial of antibiotic prophylaxis in colorectal surgery was undertaken at the Royal Brisbane Hospital. Three hundred and thirty patients were considered eligible for the trial. Three regimens were compared: a combination of 2 g ceftriaxone and 1 g metronidazole; a single dose of 2 g ceftriaxone; or 1 g cefazolin and 1 g metronidazole, as antibacterial prophylaxis in colorectal surgery. Fifty patients were excluded from analysis. The overall incidence of wound sepsis was 7.9% (22 patients). There was no statistical difference in the incidence of wound infections between the three groups. The presence of drains and the non-performance of a bowel anastomosis at the time of surgery predisposed patients to wound infection. Staphylococcus aureus or Staphylococcus epidermidis were the cause of wound infection in 16 cases. Patients in the cefazolin and metronidazole group had a significantly higher number of postoperative urinary tract and respiratory tract infections than the other two groups combined (P less than 0.01). There did not appear to be any change in sensitivity patterns to ceftriaxone during the 3 year trial. During the 3 year period of the study, ceftriaxone was found to be a safe and effective drug in antibacterial prophylaxis in colorectal surgery.

Cefazolin↗
PubMed1992

Primary culture of collecting duct cell epithelium from neonate rabbit kidney in monolayer.

Cortical collecting duct cells from rabbit neonate kidney capsula fibrosa explants were grown in low (0.1%) serum medium on permeable culture supports. We found that over a period of 3-4 days in culture, the cells migrated from the explants, to form monolayers. The cells in monolayer displayed morphology similar to adult collecting duct cells. Approximately 24% of cells grown in monolayer were found to bind a specific beta-cell-probe, peanut agglutinin. Single cells were isolated by brief exposure to 0 Ca(2+)-Mg2+ solutions and the whole-cell clamp technique was used to measure macroscopic currents. The whole-cell conductance of 1.35 +/- 0.1 nS was reduced to 0.9 +/- 0.2 nS in the presence of 100 microM-amiloride. We conclude that these cells express cell membrane properties consistent with those of the collecting duct and that it may be a useful model for the study of cellular transport mechanisms and the factors controlling development of collecting duct cell types.

Animals↗
PubMed1992

pH dependence and gene structure of inaA in Escherichia coli.

The weak-acid-inducible locus inaA in Escherichia coli was mapped to 48.6 min by P1 cotransduction of inaA Mud lac fusions and linked Tn10 insertions. The inaA1::lac fusion tested negative for phenotypes characteristic of mutations in the nearby locus ubiG. Sequence analysis of a fragment amplified by polymerase chain reaction located the inaA1::lac fusion joint within an open reading frame 311 nucleotides downstream of nrdB, transcribed in the opposite direction, encoding a 168-amino-acid polypeptide. Constitutive mutant strains identified on lactose MacConkey revealed a novel regulatory locus unlinked to inaA, which mapped at 34 min (designated inaR). Expression of inaA1::lac increased slightly with external acidification; the presence of benzoate, a membrane-permeant weak acid, greatly increased the acid effect. The expression at various combinations of benzoate and external pH correlated with the decrease in intracellular pH. The uncouplers salicylate and dinitrophenol also caused acid-dependent induction of inaA, but substantial induction was seen at external pH values higher than the internal pH; this effect cannot be caused by internal acidification. Nondissociating analogs of benzoate and salicylate, benzyl alcohol and salicyl alcohol, did not induce inaA. Expression of inaA was inversely related to growth temperature over the range of 30 to 45 degrees C. The inaA1::lac fusion was transferred to a strain defective for K+ uptake (kdpABC trkA trkD) in which pH homeostasis was shown to depend on the external K+ concentration. In this construct, inaA1::lac retained pH-dependent induction by benzoate but was not induced at low K+ concentrations. Induction of inaA appears to involve several factors in addition to internal pH. inaR may be related to the nearby locus marA/soxQ, which is inducible by acidic benzyl derivatives.

Amino Acid Sequence↗
PubMed1992

Differential expression of SM1 and SM2 myosin isoforms in cultured vascular smooth muscle.

Ribonuclease protection assays were used to measure expression of smooth muscle (SM) specific myosin heavy chain (MHC) isoforms SM1 (204 kDa) and SM2 (200 kDa) and also nonmuscle MHC-A in cultured smooth muscle cells isolated from rat aorta. In cells grown in 10% serum for 3-5 days until subconfluent, SM1 MHC mRNA decreased by 30% and SM2 MHC mRNA decreased by 80%. In cells grown in confluency for 7-11 days, SM1 MHC mRNA decreased by 45% and SM2 MHC mRNA decreased by 80%. Similar reductions were found in passaged cells. Serum withdrawal for 1-2 days from confluent cultures had little or no effect on SM1 or SM2 MHC mRNA levels. In contrast, nonmuscle MHC-A mRNA increased 10-fold in subconfluent cultures but increased only threefold higher than controls in quiescent cells. Myosin protein analysis using sodium dodecyl sulfate-polyacrylamide gel electrophoresis and Western blotting indicated that SM1 MHC protein was detectable at a reduced level in confluent cultured cells, whereas SM2 MHC protein was absent in confluent cells. The decrease in SM2 was much greater than SM1, indicating differential regulation. An apparently new isoform of SM1 MHC migrating with a mobility similar to SM2 type MHC was detected by immunoblot analysis in cultured cells.

Animals↗
PubMed1992

Effects of chlorhexidine gluconate douche on normal vaginal flora.

The effects of a 0.5% aqueous chlorhexidine gluconate (CHG) douche on the normal vaginal flora of twenty healthy nonpregnant volunteers were investigated. The douche was applied in a premeasured 180-ml quantity daily for 7 consecutive days. Specimens for aerobic and anaerobic culture of the vaginal flora were obtained on 3 occasions from each volunteer, once before and twice after CHG use. The culture results were analyzed qualitatively and quantitatively. A blood sample was also collected within 24 h of the last CHG application to determine serum CHG concentration. Lactobacillus spp., Gardnerella vaginalis and Staphylococcus epidermidis were the most prevalent aerobic bacteria at all phases of the study and Bacteroides spp. were the most prevalent anaerobes. The composition of the normal flora was essentially the same 30 days after the last dose as the pretreatment flora. Small amounts of CHG were detected in the serum of all but one subject. No untoward effects on the participants were observed. Candida albicans counts were slightly higher, but prevalence was not significantly increased at the end of the study.

Adult↗
PubMed1992

Endolaparoscopic palliation of pancreatic cancer.

Two patients with advanced pancreatic cancer were palliated for both duodenal and biliary obstruction without laparotomy. The techniques of endoscopic biliary stent and laparoscopic gastrojejunostomy are described. This combination achieved rapid palliation with minimum morbidity. Patients with advanced pancreatic cancer and a limited life expectancy benefit greatly from the shortened hospital stay and convalescence this manner of treatment offers.

Adult↗