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Biomedical subjects

D Lewis

Publications and source records attributed to D Lewis.

At least 19 recordsLinked to original sources
PubMed1992

Hawkinsinuria in two families.

Hawkinsinuria, a disorder of tyrosine metabolism has been documented in two families in the United States, in one of which there was clear evidence of autosomal dominant inheritance. Metabolic acidosis and failure to thrive appear to be confined to infancy. Tyrosyl metabolites and 5-oxoproline are also found only in infancy, while 4-hydroxycyclohexylacetic acid was present only with time. The disease may be detected by organic acid analysis or by staining an electropherogram for sulfur containing compounds.

Acidosis↗
PubMed1992

Coupled expression of Ca2+ transport ATPase and a dihydrofolate reductase selectable marker in a mammalian cell system.

Stable expression of a full-length cDNA encoding chicken fast muscle Ca2+ transport ATPase was obtained in a Chinese hamster lung cell line (DC-3F), using a dual-promoter expression vector (pH beta FCaA3) in which the ATPase was cloned downstream of a human beta-actin gene promoter, and a mutant dihydrofolate reductase cDNA (A3/DHFR) was cloned downstream of an SV40 promoter-enhancer. Owing to its essentially normal catalytic activity and modest (20-fold) resistance to the antifolate methotrexate (MTX), the A3/DHFR mutant enzyme served as an efficient dominant selection marker in transfected cell populations challenged with MTX and, within a broad range of drug concentrations, allowed subsequent amplification and overexpression of vector sequences. In stable transfectants, the expressed ATPase was targeted to intracellular membranes, and the microsomal fractions from those cells exhibited high rates of Ca2+ transport. In comparative experiments using transient expression in COS1 cells, the level of ATPase per transfected cell was greater, but less than 5% of the transfected population exhibited ATPase expression. Furthermore, as opposed to the stable lines, the transiently expressing cells could not be propagated. Overall, the yield of ATPase was 12-16 and 4-6 micrograms per milligram of microsomal protein in the stable and the transient expression systems, respectively. The advantages of the stably transfected cell lines therefore lie in the homogeneity of ATPase expression and its distribution in cells and microsomes, in the large yield of microsomes obtained by continuous cell propagation, and in the reproducible functional characteristics of the microsomes. Moreover, the microsomes derived from stably transfected cell lines provide a convenient system for studies of Ca2+ transport and ATPase partial reaction, eliminating the need to conduct repetitive transient transfections to obtain sufficient amounts of enzyme for functional studies.

Animals↗
PubMed1992

Construction of a dominant selectable marker using a novel dihydrofolate reductase.

Simian virus 40 promoter-enhancer-based mammalian expression plasmids using dihydrofolate reductase (DHFR)-encoding cDNA sequences originally isolated from two methotrexate (MTX)-resistant, DHFR-overproducing Chinese hamster lung cell lines were constructed. One, designated pSVA75, contains a DHFR cDNA that encodes leucine (Leu22) and corresponds to the wild type (wt), MTX-sensitive form of the enzyme [Melera et al., J. Biol. Chem. 263 (1988) 1978-1990]. The other plasmid, pSVA3, contains a cDNA that encodes a novel mutant form of the enzyme in which Leu22 has been changed to Phe [Melera et al., Mol. Cell Biol. 4 (1984) 38-48]. The resulting DHFR displays a 20-fold-enhanced resistance to inhibition by MTX, but maintains the catalytic activity of the wt enzyme [Albrecht et al., Cancer Res. 32 (1972) 1539-1546]. Transfection of DHFR- Chinese hamster ovary cells with either plasmid demonstrated that both were able to reconstitute the DHFR+ phenotype with equal efficiency (i.e., greater than 2.5 x 10(-3), indicating that both the wt and mutant enzymes were catalytically active in transfected cells. In addition, the mutant form of the enzyme was found to act as a dominant selectable marker when transfected into diploid DHFR+ cells, and to allow selection of resistant clones at low MTX concentrations (125 nM MTX) with a frequency of greater than 8 x 10(-4). Moreover, transfected clones were found to amplify their exogenous DHFR sequences to reasonably high levels (42-fold) at relatively low (888 nM) MTX concentrations, suggesting that substantial amplification of DHFR DNA and cotransfected sequences as well, can be achieved with this vector.

Animals↗
PubMed1992

When should a synthetic casting material be used in preference to plaster-of-Paris? A cost analysis and guidance for casting departments.

An accurate cost analysis of the use of one of the new synthetic casting materials (Cellacast) compared with plaster-of-Paris (Gypsona) was undertaken over a 3-month period in the fracture clinic of Cardiff Royal Infirmary. The mean duration of usage before failure for synthetic forearm, scaphoid and below-knee casts was found to be approximately twice that of plaster casts. The use of synthetic casting materials was found to be cost-effective in situations where there was thought to be a high probability that structural failure of the cast would occur. Guidelines for the use of plaster-of-Paris and synthetic casting materials are presented.

Calcium Sulfate↗
PubMed1992

Congestive heart failure: survival trial of antiarrhythmic therapy (CHF STAT). The CHF STAT Investigators.

This study is a prospective, double-masked, randomized, clinical trial to determine the effect of anti-arrhythmic drug therapy on mortality in patients with congestive heart failure and ventricular arrhythmia. Patients will be assigned to receive either amiodarone or placebo. Eligible patients include those with ischemic and nonischemic congestive heart failure (New York Heart Association class III or VI) and with 10 or more ventricular premature beats per hour. All patients must have shortness of breath with minimal exertion or paroxysmal nocturnal dyspnea, a left ventricular internal dimension (LVIDd) by echocardiogram of 55 mm or greater (> or = 55 mm) or a CT ratio of greater than 0.5, and an ejection fraction of 40% of less. Patients will be entered into the study for 2.5 years and followed for an additional 2 years. Drug therapy will be continued for all patients throughout the entire study unless adverse reactions occur that necessitate individualized treatment. The expectation is that 674 patients are to be entered into the study from 25 participating centers. This sample size will allow for the detection of a 33% decrease in 2-year mortality (20% vs. 30%) in the treated patients as compared to those in the placebo group with a power of 0.90 and a two-sided alpha level of 0.05. Intermittent Holter monitoring, radionuclide ventriculograms, pulmonary function tests, echocardiograms, and blood tests, including arterial blood gases, will be required for each patient. The study analysis will address differences in total mortality, cardiac mortality, and sudden cardiac death between patients receiving anti-arrhythmic drug therapy and those receiving placebo. Other factors to be examined include the effects of antiarrhythmic therapy on suppression of arrhythmias, on ejection fraction, and relation of ischemic events to mortality.

Amiodarone↗
PubMed1992

Risk of viral hepatitis among military personnel assigned to US Navy ships.

A prevalence study of 2072 male US shipboard military personnel scheduled for deployment to South America/West Africa and the Mediterranean was conducted to determine whether serologic evidence of prior hepatitis A, B, or C infection is associated with exposure in foreign countries. There were 210 subjects (10.1%) who had antibodies to hepatitis A virus (anti-HAV), 76 (3.7%) to hepatitis B core antigen (anti-HBc), and 9 (0.4%) to hepatitis C virus (anti-HCV). By multivariate analysis, anti-HAV seropositivity was independently associated with age, non-white racial/ethnic groups, birth outside of the United States, and prior Caribbean deployment for less than 1 year. Anti-HBc seropositivity was independently associated with black and Filipino race/ethnicity, foreign birth, a history of a sexually transmitted disease, South Pacific/Indian Ocean deployment (less than 12 months), and South Pacific or Mediterranean duty for (greater than 1 year). No geographic risk factors were associated with anti-HCV positivity. These data indicate that military personnel deployed outside the United States are at increased risk of viral hepatitis infection and should be considered for vaccination.

Adult↗
PubMed1992

The use of DiI-marked hepatocytes to demonstrate orthotopic, intrahepatic engraftment following hepatocellular transplantation.

A novel method is described for marking primary hepatocytes with the fluorescent dye DiI prior to hepatocellular transplantation and identifying these cells within the hepatic parenchyma of recipient animals by fluorescence microscopy and flow cytometry. Optimal conditions are described for marking cells with DiI in suspension or in monolayer cultures prior to transplantation. DiI is shown to be nontoxic to hepatocytes and not to be exchanged between adjacent cells in vitro. Histological analysis of transplanted tissues shows DiI staining of engrafted hepatocytes and phagocytotic cells (Kupffer cells). This analysis shows that hepatocytes engraft within the hepatic parenchyma and exhibit a histological appearance indistinguishable from normal by conventional hematoxylin and eosin staining. Many previous reports of hepatocellular transplantation have been limited by their inability to unequivocally identify transplanted cells within the liver. These data illustrate the importance of having specific markers for transplanted cells that engraft in an orthotopic location and assume a normal morphological appearance.

Animals↗
PubMed1992

Anaemia, iron-related measurements and erythropoietin levels in untreated patients with active leprosy.

The mechanisms responsible for anaemia in leprosy were studied prior to the institution of therapy in 56 patients with active disease. Haematological indices, iron-related measurements, inflammatory markers and erythropoietin levels were assessed, with bone-marrow studies being performed on anaemic patients. Anaemia was more common in the patients with lepromatous leprosy (85.7%) than it was in the rest of the group (19%). The lepromatous group exhibited the disordered iron transport of the anaemia of chronic disorders in that they had a significantly lower mean serum iron level (P less than 0.05), and a mildly raised serum ferritin concentration. Anaemic lepromatous patients also showed a blunted erythropoietin response compared with controls with non-inflammatory anaemia. A subgroup of five anaemic subjects displayed apparently adequate transport of iron to the erythroid marrow (normal percentage transferrin saturations and appropriate sideroblast counts) and the blunted erythropoietin response appeared to be the dominant factor in the pathogenesis of their anaemia. Analysis of inflammatory markers revealed that while the erythrocyte sedimentation rate was very high in the lepromatous subjects, there was no concomitant rise in C-reactive protein concentration. This suggests the presence of a disordered cytokine-mediated acute phase response in the condition.

Adolescent↗
PubMed1992

DiI as a marker for cellular transplantation into solid organs.

Research in cellular transplantation is frequently compromised by an inability to identify transplanted cells engrafting into orthotopic sites if they exhibit normal morphology and no unique antigenic markers. A method is described for using the fluorescent dye DiI as a marker for cell transplantation studies. This dye is not metabolized or exchanged between cells in vitro or in vivo and enables identification of engrafted cells by fluorescence microscopy, flow cytometry or fluorescence-activated cell sorting. Applications are described in autologous hepatocellular and thyroid follicular cell transplantation.

Animals↗
PubMed1992

Markers of hepatitis B infection in Tari District, Southern Highlands Province, Papua New Guinea.

Serum samples collected from two groups in the Tari District of Southern Highlands Province were assayed for markers of hepatitis B virus (HBV) infection. 85% of women of childbearing age were found to have markers of HBV infection; 37% were positive for HBV surface antigen (HBsAg), indicative of the chronic carrier state, and 6.6% were positive for HBV e antigen (HBeAg), indicating the presence of actively replicating virus. 75% of women negative for HBsAg were positive for antibody to HBV core antigen (HBcAb), a marker of past infection. A group of children aged 6 to 18 years showed a significantly lower prevalence of markers of infection (66%) but higher rates of HBsAg positivity (46%) and HBeAg positivity (30%). Only 37% of the HBsAg-negative children in this group were positive for HBcAb. The results from this serosurvey suggest that the major route of HBV transmission in this population is horizontal, between older children, though significant transmission also occurs during the neonatal period.

Acute Disease↗
PubMed1992

Factors influencing medical interns trained at U.W.I. to work subsequently in a rural area in Jamaica.

Recognising the present paucity of doctors trained at the University of the West Indies who are working in rural government health facilities in Jamaica, and its impact on the health services, this study was done to determine the factors influencing the decision of UWI-trained interns to work in these facilities post-internship. A questionnaire was administered to 57 UWI-trained medical graduates presently doing their internship in Jamaica. The results showed that there was no significant difference in the choice of placement with respect to sex, or residential background of the intern, though the latter seemed to indicate a trend. Of those who thought they would work in a rural government health facility, two-thirds would do so immediately post-internship but 50% did not plan to work there for more than five years. Opportunities for postgraduate training and lack of equipment were the most important deterrents to working in a rural government health facility.

Choice Behavior↗
PubMed1991

Anticoagulant properties of semisynthetic polysaccharide sulfates.

Several naturally occurring polysaccharides were purified and subsequently sulfated by chlorosulfonic acid-pyridine complex. These were isolated as the sodium salt and further purified by ECTEOLA cellulose chromatography. Anticoagulant properties of the sulfated polysaccharides were compared with commercial heparin by measuring their in vitro effects on activated partial thromboplastin time (APTT), prothrombin time (PT) and thrombin time (TT) using pooled normal human plasma. In general, all the compounds exhibited antithrombic (anti-TT) properties similar to heparin but were less effective than heparin in inhibiting APTT or PT. The in vivo anticoagulant properties were also compared with commercial heparin by injecting rats a single intraperitoneal dose and measuring plasma APTT at 2, 4 and 6 hour intervals. All of the compounds including heparin increased APTT significantly at 2 hours and then gradually returned to near normal value after 6 hours. Larchwood xylan sulfate was almost as active as heparin in inhibiting APTT while the rest of the compounds were less active. Toxicological studies using rats showed wide variations in the LD50 of various compounds. Sulfated xylan and heparin were least toxic while sulfated polysaccharide of locust bean was most toxic. For most of the compounds the LD50 was 5-100 fold higher than the effective dosage.

Animals↗