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Biomedical subjects

D Skelton

Publications and source records attributed to D Skelton.

16 recordsLinked to original sources
PubMed1999

Immune response to green fluorescent protein: implications for gene therapy.

Green fluorescent protein (GFP) is a widely used intracellular reporter molecule to assess gene transfer and expression. A potential use for GFP is as a co-expressed marker, to select and enrich gene-modified cells by flow cytometry. Processed peptides derived from GFP and presented by the major histocompatibility complex on the cell surface could potentially induce T cell immune responses against GFP+ cells. Thus, clinical application of GFP is premature, since in vivo studies on its immunogenicity are lacking. Therefore, we investigated immune responses against EGFP (enhanced-GFP) in two transplantable murine models: the BALB/c (H-2d) BM185 pre-B leukemia and the C57BL/6 (H-2b) EL-4 T cell lymphoma. BM185 and EL-4 cell lines modified to express high levels of EGFP showed drastic reduction of disease development when transplanted into immunocompetent mice. BM185/ EGFP did lead to rapid development of disease in immunodeficient Nu/Nu mice. Mice surviving BM185/EGFP leukemia challenge developed high cytotoxic T lymphocyte (CTL) responses against EGFP-expressing cells. Furthermore, immune stimulation against BM185/EGFP cells could also be induced by immunization with EGFP+ transduced dendritic cells. The effects of the co-expression of EGFP and immunomodulators (CD80 plus GM-CSF) were also investigated as an irradiated leukemia vaccine. EGFP co-expression by the vaccine did not interfere with the development of CTLs against the parental leukemia or with the anti-leukemia response in vivo. These results indicate that the immune response against EGFP may interfere with its applicability in gene insertion/replacement strategies but could potentially be employed for leukemia cell vaccines.

Animals↗
PubMed1995

Multiple modifications in cis elements of the long terminal repeat of retroviral vectors lead to increased expression and decreased DNA methylation in embryonic carcinoma cells.

Infection by murine retroviruses in embryonic carcinoma (EC) and embryonic stem cells is highly restricted. The transcriptional unit of the Moloney murine leukemic virus (MoMuLV) long terminal repeat (LTR) is inactive in EC and embryonic stem cells in association with increased proviral methylation. In this study, expression in F9 EC cells was achieved from novel retroviral vectors containing three modifications in the MoMuLV-based retroviral vector: presence of the myeloproliferative sarcoma virus LTR, substitution of the primer binding site, and either deletion of a negative control region at the 5' end of the LTR or insertion of a demethylating sequence. We conclude that inhibition of expression from the MoMuLV LTR in EC cells is mediated through the additive effects of multiple cis-acting elements affecting the state of methylation of the provirus.

3T3 Cells↗
PubMed1994

Familial juvenile polyposis. Study of a kindred: evolution of polyps and relationship to gastrointestinal carcinoma.

Familial juvenile polyposis is a rare intestinal polyposis that has recently been associated with gastric and colonic adenocarcinoma. The authors report a kindred of 41 members, 11 of whom have familial juvenile polyposis. In these patients, random sections of otherwise grossly normal-appearing colonic mucosa showed a dense population of mixed inflammatory cell infiltrates in the superficial third of the lamina propria. Fine nodular mucosa was noted focally and diffusely in six of eight colons resected. These consisted of foci of dense inflammatory cell infiltrates in the mucosa with slight crypt architectural abnormalities. The majority of lesions were typical juvenile polyps. Dysplastic changes were noted in the polyps that were 1-2.9 cm or larger. The largest polyps contained foci of villous adenoma and juvenile polyp. A focus of adenocarcinoma of the colon was noted at the base of the villous adenoma portion of the largest polyp. The gastric polyps were histologically identical to hyperplastic polyps of the stomach. This report represents the largest number of patients (eight) in a single family with familial juvenile polyposis studied histologically. This is also the first time that the changes in the nonpolypoid colonic and gastric mucosa have been reported. The pattern of inheritance in this family suggests that the trait for familial juvenile polyposis segregates as an autosomal dominant.

Adenocarcinoma↗
PubMed1993

Treadmill walking in old age may not reproduce the real life situation.

OBJECTIVE: In a preliminary study in our laboratory, healthy elderly people had a higher heart rate during treadmill walking than during corridor walking at the same speed. The objective of this study was to determine whether this initial observation, (1) persisted after repeated testing, (2) was present in younger adults, (3) was due to wearing a mouthpiece during treadmill walking, or (4) was due to a change in gait. DESIGN: A study of elderly and young volunteers undergoing repeated testing, with comparison of treadmill walking with corridor walking. SETTING: The Royal Free Hospital School of Medicine. PARTICIPANTS: Twelve healthy elderly (71-80 years) and 12 healthy young (21-37 years) volunteers. MAIN OUTCOME MEASURES: Heart rate (beats/min) and step rate (steps/min) during comfortable self-paced corridor walking and during treadmill walking at the same speed. MAIN RESULTS: The elderly subjects had higher heart rates during treadmill walking than during corridor walking at the same speed (mean difference = 6 beats/min, 95% Confidence Interval (CI) = 1 to 10). This difference increased (to a mean of 11 beats/min, 95% CI = 5 to 16) when a mouthpiece was worn on the treadmill. These differences persisted after repeated testing. The young subjects did not have higher heart rates on the treadmill, (with or without the mouthpiece). In both groups, step rate was lower (95% CI = -9 to -2, elderly; -5 to -2, young) during treadmill walking, corresponding to a 3% increase in stride length. CONCLUSION: The heart rate response to treadmill walking in healthy elderly people may be less representative of the "real life" situation than in younger adults.

Adult↗
PubMed1991

Nutrition of the elderly.

The progressively increasing number of elderly people in the Canadian population and the disproportionate expenditure on their health care has stimulated interest in prevention of common illnesses observed in this age group. It is now recognized that nutrition plays an important role in health status, and both undernutrition and overnutrition are associated with greater risk of morbidity and mortality. Nutritional problems in the elderly can be suspected if there are several high-risk factors present--for example, living alone, physical or mental disability, recent loss of spouse or friend, weight loss, use of multiple medications, poverty, and high consumption of alcohol. Physical examination, anthropometry, and measurements of serum albumin levels and hemoglobin and lymphocyte counts are simple but helpful tools in confirming the presence of nutritional disorders. The prevention and correction of nutritional problems is likely to prove beneficial in the management of common geriatric illnesses. In these efforts, it is desirable to have a team approach in which the physician, the dietitian and the nurse each have a defined interactive role. Home care support services are important adjuncts in continuing care. Nutrition should receive a greater emphasis in the training of physicians and other health professionals.

Aged↗
PubMed1988

Treatment of tardive dyskinesia: preliminary report on use of tetrabenazine.

Tetrabenazine has been used for treatment of tardive dyskinesia sporadically over the past twenty years. Dose has usually been decided empirically without assaying blood levels. This report describes 23 cases treated successfully with tetrabenazine. Our method of measuring levels of tetrabenazine and its metabolites in biological samples is described briefly.

Adult↗
PubMed1986

Direct injection high-performance liquid chromatography of tetrabenazine and its metabolite in plasma of humans and rats.

A convenient, selective, and sensitive reversed-phase HPLC assay was developed to measure concentrations of the dopamine-depleting agent, tetrabenazine (1,3,4,6,7,11b-hexahydro-3-isobutyl-9,10-dimethoxy-2H-benzo(a)quinoli zin-2-one) and its dihydro metabolite in the plasma of patients with tardive dyskinesia receiving therapeutic doses of the drug and in the plasma of rats. The method involves plasma protein precipitation, oxidation of the compounds with mercuric acetate at 110 degrees C for 1 h, addition of internal standard, and injection into the instrument. Fluorescence detection was utilized at excitation and emission wavelengths of 265 and 418 nm, respectively. The peaks from the drug, its metabolite, and at least three other substances were best resolved at 60 degrees C using a mobile phase of water:acetonitrile:acetic acid:triethylamine (65:33:2:0.15) at a flow rate of 0.6 mL/min; the 4.6 mm X 10 cm column contained 5 micron of octadecylsilane packing. To assess the applicability of the assay, the drug was administered intravenously to rats, and plasma concentrations were determined before (by UV-HPLC) and after (by fluorescence-HPLC) the oxidative procedure. In addition, the MS spectra of tetrabenazine and the dihydro metabolite, isolated from biological samples, were identical to those of authentic samples. Excellent linearity was observed between the peak area ratios and concentrations over the ranges 0.5-200 and 2-1000 ng/mL of the drug and the metabolite, respectively. Minimum quantifiable concentrations of the drug and its metabolite were 0.5 and 2.0 ng/mL, respectively. The sensitivity was found to be adequate for pharmacokinetic studies of tetrabenazine in humans and rats.

Animals↗
PubMed1985

Vitamin B12 (cobalamin) and folate blood levels in geriatric reference group as measured by two kits.

For serum vitamin B12 levels there was little apparent difference between a geriatric healthy reference group and a hospitalized group for the total population studied; however, the hospitalized males did have an increased prevalence of values less than normal range. The frequency distribution for both sexes of the geriatric reference group gave lower range limits than manufacturer's normal range. (68-632 vs 133-708 pmol/L for Becton Dickinson, and 125-609 vs 179-930 pmol/L for Bio-Rad, using 95% non-parametric limits). For folate there was an increased incidence in values of less than normal in the hospitalized group versus the geriatric reference group, but there was no difference in the ranges calculated for the latter compared to either manufacturer's normal range derived from a younger population. Comparison of results by two manufacturers' kit methods confirmed Bio-Rad's claim to increased low-end sensitivity of standard curve in range of clinical interest.

Age Factors↗
PubMed1977

The future of health care for the elderly.

Problems facing the modern health care worker are examined. These include population changes, the changing pattern of disease, the psychosocial aspects of aging, and altered pathophysiologic mechanisms. The major future requirements in health care for the elderly are outlined. Greater emphasis should be placed upon education in the disciplines of Gerontology and Geriatric Medicine. Society needs to be made more aware of the realities of aging. Health care professionals need to develop their communication skills and to practice more effective teamwork. Greater coordination of the components of health care delivery systems will be needed in order to provide comprehensive and continuing health services. Research into the true and changing needs of the elderly recipients of health care should be emphasized. Prevention and early detection of disease is an important focus in Geriatric Medicine for the future.

Aged↗
PubMedDate not supplied

Pharmacokinetics of tetrabenazine and its major metabolite in man and rat. Bioavailability and dose dependency studies.

The pharmacokinetics of tetrabenazine (TBZ), a catecholamine and serotonin depletor, and its major metabolite, dihydrotetrabenazine (HTBZ), were studied in four patients affected by tardive dyskinesia, who were under treatment with different doses of TBZ (12.5-37.5 mg, t.i.d.), and in the rat. In the patients, the steady-state area under the plasma concentration-time curves (AUCs) of the metabolite were 82.6-199-fold higher than those of TBZ. The drug showed a small and erratic bioavailability (F = 0.06 +/- 0.026, mean +/- SD). It appears to be extensively metabolized, as no unchanged TBZ could be detected in the urine of the patients. Single oral doses of 0.5-10 mg/kg and single iv dose of 1 mg/kg of TBZ were each administered to four to six rats. The clearance of the drug following iv administration to the rat (mean +/- SD, 58.9 +/- 6.01 ml X min-1 X kg-1) was very close to the rat hepatic blood flow indicating a perfusion-limited clearance. An F value of 0.17 was obtained following iv and po doses of 1 mg/kg TBZ in the rat. The oral absorption of TBZ seems to be rapid and almost complete. Plots of the AUCs of TBZ and HTBZ vs. five different po doses (0.5-10 mg/kg) were linear with correlation coefficients of 0.998 and 0.986 for TBZ and HTBZ, respectively, suggesting linear kinetics in the examined dosage range. In both the patients and rats, the plasma profile of TBZ followed characteristics of a multiexponential pharmacokinetic model.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗