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Biomedical subjects

D Lewis

Publications and source records attributed to D Lewis.

At least 199 records · Page 11Linked to original sources
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↗
PubMed1991

Sequential interleukin 2 and interleukin 2 receptor levels distinguish rejection from cyclosporine toxicity in liver allograft recipients.

Previous studies of renal transplant recipients have demonstrated that allograft rejection is accompanied by an increase in plasma and urinary levels of interleukin 2 and its soluble receptor before the development of clinical symptoms. After measuring interleukin 2 and interleukin 2 receptor levels in the plasma, bile, and urine of liver transplant recipients, we found that rejection is preceded by elevation of plasma and biliary levels of both substances, that cyclosporine toxicity did not affect either of these levels, and that urinary levels of the substances are unaffected in either condition. Levels of interleukin 2 and interleukin 2 receptors increased in bile earlier than in plasma, and interleukin 2 levels did not overlap among stable patients and those experiencing rejection, whereas levels of interleukin 2 receptors did. Serial measurements of interleukin 2 levels, particularly in the product of the transplanted organ, provide a reliable assessment of the immunologic status of the allograft.

Bile↗
PubMed1991

Eradication of colonization by methicillin-resistant Staphylococcus aureus by using oral minocycline-rifampin and topical mupirocin.

In an attempt to control the spread of methicillin-resistant Staphylococcus aureus (MRSA) within a spinal cord injury unit, we investigated the mode of transmission and implemented a multidisciplinary approach for control that consisted of grouping of patients into cohorts, contact isolation, and antibiotics. Surveillance cultures of patients and nose and hand cultures of medical personnel were performed. Of 11 colonized patients, 6 had MRSA isolates that shared a similar plasmid profile and antibiogram, raising the possibility of interpatient spread of the organism. Medical personnel had no evident role in transmitting MRSA. All patients' pretherapy MRSA isolates were susceptible to minocycline and, except for one, to rifampin. Time-kill studies showed an indifferent interaction of these two antibiotics. Ten colonized patients received a 2-week oral course of 100 mg of minocycline twice daily and 600 mg of rifampin once daily, while the 11th patient was treated for only 1 week. Patients with colonization of the nares also had twice daily nasal application of 2% mupirocin for 5 days. Colonization with MRSA cleared in 10 of 11 patients (91%) and 20 of 21 sites (95%). When the individual circumstances of a medical facility justify eradication of MRSA colonization, a multidisciplinary approach that includes antibiotic therapy with oral minocycline and rifampin, along with topical mupirocin for those with nasal carriage, may be successful.

Administration, Oral↗
PubMed1991

Abdominal CT findings after liver transplantation in 66 patients.

CT scanning is used frequently to assess the condition of patients after liver transplantation. The CT records of 174 adult patients who underwent liver transplantation were studied retrospectively to determine the number and timing of CT studies as well as the frequency and significance of the findings. One-hundred seventy CT scans were obtained in 66 (38%) of the 174 patients, with a mean of 2.6 scans/patient. The interval between transplantation and scanning was 1 day to 24 months; in 59 (89%) of 66 patients, the first CT scan was obtained within 30 days. The acute indications for CT scanning were fever or leukocytosis in 54 (92%) of 59 patients and abnormal liver function tests in five (8%) of 59 patients. CT scans obtained more than 30 days after transplantation were repeat scans in all but seven patients. Indications in this latter group were the same as for the acute group, plus evaluation of hepatic neoplasia in three patients. CT findings included periportal low attenuation in 41 (62%) of 66 patients; ascites in 25 (38%); splenomegaly in 19 (29%); loculated intraperitoneal noninfected fluid collections in 13 (20%); intrahepatic, splenic, pancreatic, or perihepatic abscesses in seven (11%); hepatic infarction in six (9%); splenic infarction in three (4%); and hepatic calcification in two (3%). Other major abnormalities included inferior vena caval thrombosis (one patient), pseudoaneurysm of the hepatic artery with rupture (one patient), and recurrent hepatocellular carcinoma (one patient). CT scanning after liver transplantation is used predominantly in the acute setting to evaluate for liver infarction or intraabdominal abscess. In this setting, CT showed these abnormalities, in addition to tumor recurrence or vascular abnormalities, in 15 (23%) of 66 patients.

Ascites↗
PubMed1991

Improved detection of in situ hybridization by laser scanning confocal microscopy.

Laser scanning confocal microscopy (LSCM) offers a significant improvement over conventional bright-field and dark-field light microscopy for producing images of silver grains in autoradiograms of specimens prepared by in situ hybridization. The out-of-focus image of the background silver grains present in the emulsion is eliminated from the in-focus image of the radioactive probe associated with the cells by optical sectioning with the LSCM operated in a reflected light mode. The improved images produced by the LSCM provide a significant increase in the sensitivity of detecting positively labeled cells and tissues prepared by in situ hybridization. The power of this detection method is demonstrated using samples of HIV-infected human peripheral blood cells, tissue sections of human placenta and human skin. It is anticipated that the method can be universally applied to samples prepared by in situ hybridization techniques.

Cell Line↗
PubMed1991

A long-term clinical review of patients with oesophageal pain.

Oesophageal and cardiac chest pain are often difficult to distinguish on clinical grounds. The clinical course of 32 patients with recurrent chest pain due to oesophageal dysmotility has recently been assessed by questionnaire 9 years after diagnosis. Twenty-six of the 27 who replied continued to have pain, but despite this there was a significant reduction in the number of hospital admissions associated with chest pain. Repeat oesophageal manometry in nine showed that the disturbance in motility persisted. Three had died, one of them from a myocardial infarction; two patients could not be traced.

Adult↗
PubMed1990

Erythroid membrane-bound protein kinase binds to a membrane component and is regulated by phosphatidylinositol 4,5-bisphosphate.

In the erythrocyte, a membrane-bound serine/threonine protein kinase (a casein kinase) has been shown to phosphorylate a number of membrane proteins, modulating their function. Here we report that the membrane-bound protein kinase binds to membranes by an association with a minor membrane component contained in preparations of glycophorin (possibly a minor glycophorin). The binding of the kinase to glycophorins does not significantly modify kinase activity. However, upon binding, the kinase activity is potently inhibited by phosphatidylinositol 4,5-bisphosphate, and the affinity of the kinase for the glycophorins is increased. Other phospholipids or polyanions such as inositol 1,4,5-trisphosphate or 2,3-diphosphoglycerate do not affect protein kinase activity when the kinase is bound to membranes but do inhibit the solubilized membrane-bound kinase. In the erythrocyte, there is a cytosolic form of the casein kinase which is very similar, having the same molecular weight and substrate specificity as the membrane-bound casein kinase. The cytosolic casein kinase is inhibited by 2,3-diphosphoglycerate but much less so by glycophorin preparations containing phosphoinositol 4,5-bisphosphate. When the sequences of both casein kinases were compared by two-dimensional peptide mapping, it was found that the two kinases were very similar but not identical.

Casein Kinases↗
PubMed1990

A cell cycle analysis of growth-related genes expressed during T lymphocyte maturation.

Fetal liver or bone marrow-derived T lymphocyte precursors undergo extensive, developmentally regulated proliferation in response to inductive signals from the thymic microenvironment. We have used neonatal mouse thymocytes size-separated by centrifugal elutriation to study the cell cycle stage-specific expression of several genes associated with cell proliferation. These include genes involved in the biosynthesis of deoxyribonucleotide precursors, such as dihydrofolate reductase (DHFR), thymidylate synthase (TS), and the M1 and M2 subunits of ribonucleotide reductase, as well as c-myc, a cellular oncogene of unknown function. Using nuclear run-on assays, we observed that the transcription rates for these genes, with the exception of TS, are essentially invariant not only throughout the cell cycle in proliferating cells, but also in noncycling (G0) cells. The TS gene showed a transient increase in transcription rate in cells which bordered between a proliferating and nonproliferating status. Studies of an elutriated T cell line, S49.1, yielded similar results, indicating that the process of immortalization has not affected the transcriptional regulation of these genes. Analysis of steady-state mRNA levels using an RNase protection assay demonstrated that the levels of DHFR and TS mRNA accumulate as thymocytes progress through the cell cycle. In contrast, only the M2 subunit of ribonucleotide reductase showed cyclic regulation. Finally, in contrast to cultured cell models, we observed an abrupt fivefold increase in the steady-state level of c-myc mRNA in the transition from G1 to S-phase. We conclude from these studies that the transcriptional regulation of specific genes necessary for cellular proliferation is a minor component of the developmental modulation of the thymocyte cell cycle.

Animals↗