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Biomedical subjects

M J Stewart

Publications and source records attributed to M J Stewart.

At least 163 records · Page 9Linked to original sources
PubMed1986

Micro-scale ultracentrifugation as an alternative to ultrafiltration for the determination of the unbound fraction of phenytoin in human serum.

Free phenytoin has been determined using micro-scale ultracentrifugation followed by analysis by EMIT. The effect of temperature on the determined free fraction was investigated and the ultracentrifugation procedure validated against ultrafiltration. Ultracentrifugation gave free fractions which were on average 16% lower than those obtained using ultrafiltration, but correlation was good, as was the correlation with measurements of total phenytoin (r = 0.90). Micro-scale ultracentrifugation is a simple procedure which can be of great utility in the measurement and investigation of free drug levels.

Blood Proteins↗
PubMed1986

Rhoptry secretion of membranous whorls by Plasmodium falciparum merozoites.

Multilamellar membranous whorls were localized, by electron microscopy, in elements of the rhoptry-microneme complex from glutaraldehyde-tannic acid (TA)-fixed merozoites of the human malarial parasite, Plasmodium falciparum. These multilaminate structures, which have a dark line-to-dark line periodicity of approximately 5 nm, were also found in the nuclear envelope and closely apposed to the external surface of merozoites. Segmented schizonts, which contain intracellular merozoites, often showed membranous whorls within their parasitophorous vacuoles and closely apposed to the external surface of the parasitophorous vacuole membrane. Whorls were not found in trophozoites, immature schizonts, and uninfected erythrocytes. Most rhoptries in merozoites fixed in glutaraldehyde-TA were electron-lucent whereas rhoptries fixed in glutaraldehyde alone were electron-dense. Some merozoites fixed in glutaraldehyde-TA had both an electron-dense and an electron-lucent rhoptry. These findings suggest that TA induces the premature extrusion of rhoptry materials. Our findings support previous suggestions in the literature that phospholipid materials secreted from merozoite rhoptries are involved in merozoite interaction with host erythrocytes.

Animals↗
PubMed1985

The effect of surfactants on the high-performance liquid chromatography of anthracyclines.

A rapid, reversed-phase high-performance liquid chromatographic method is described for the determination of the antineoplastic drug, doxorubicin (Adriamycin), and its major metabolites in plasma. The addition of anionic, cationic or non-ionic surfactants was found to reduce k'; the mechanisms of this finding are discussed and the performance of an optimized method using a non-ionic surfactant, Brij-35, is described for plasma samples.

Journal Article↗
PubMed1985

Rhoptry secretion of membranous whorls by Plasmodium berghei sporozoites.

Electron microscopy of sporozoites of the rodent malaria parasite, Plasmodium berghei, reveals electron-dense multilaminate membranous whorls within components of the rhoptry-microneme complex after fixation with tannic acid in conjunction with glutaraldehyde. This multilaminate material, which has a dark line to dark line periodicity of approximately 5 nm, appears to be secreted from the sporozoite since it is also found adhering to the sporozoite's external surface. The material may function in sporozoite gliding motility and in invasion of host cells.

Animals↗
PubMed1984

Early discharge and return to work following myocardial infarction.

Individuals who have experienced a myocardial infarction (MI) account for the largest component of all hospitalization costs and foregone earnings due to cardiac disease. Early return to full employment and premorbid activity level should be the focus of cost-effective rehabilitative programs. Yet the economic benefits of vocational rehabilitation have not been directly researched. Therefore, issues of import regarding activity after MI include the timing of ambulation, discharge and return to work. Studies of early mobilization and discharge are contrasted in terms of methodology and outcome. These cite economic, social and psychological advantages, yet these factors are examined in isolation of other variables. A review of the literature reveals that there is a reluctance by many health professionals to institute such practices based in part on the dilemma surrounding selection of specific indicators and risk factors. Yet analysis reveals that the contention surrounding these exclusion criteria is perhaps unfounded, as the variance is less than is commonly assumed. Recurrent themes likewise emerge regarding the multiplicity of variables associated with the timing of resumption of employment, which is considered to be the most precise index of recovery following an MI. Of these, only early intense rehabilitation, directed at attitudinal and behavioural change, is amenable to modification by health professionals. Related research endeavours have examined employment following aortocoronary bypass surgery, risk factors in the work environment and work stressors which occur following MI. Controversy arises regarding the correlation of age and personality factors with return to work. Discrepancies in research findings are attributed to the diverse approaches to data collection, obstacles encountered in measuring psychological states, lack of operational definitions, differences in degree of rehabilitation and length of follow-up and the absence of controlled trials. Clearly, experimental research focusing on the job-related economic and human cost impact of specific rehabilitation programs must be conducted.(ABSTRACT TRUNCATED AT 400 WORDS)

Clinical Trials as Topic↗
PubMed1983

An assay for methotrexate and its metabolites in serum and urine by ion-pair high-performance liquid chromatography.

A high-performance liquid chromatographic assay for methotrexate and its metabolites, 7-hydroxy-methotrexate, 4-amino-4-deoxy-N10-methyl-pteroic acid and 7-hydroxy-4-amino-4-deoxy-N10-methyl-pteroic acid in the range 10 microg/l to 50 mg/l (2.2 x 10(-8) to 1.1. x 10(-4)M) has been developed using L-tryptophyl-L-glutamic acid as internal standard. Extraction was performed using an anion exchange resin (Dowex 1-X2) with subsequent ion-pair chromatography of the appropriate eluent fraction. The method has been found to be sensitive and precise for the analysis of both serum and urine, and may also be used for the quantitation of polyglutamyl metabolites.

Journal Article↗
PubMed1983

Pharmacokinetics of two dosage levels of trimethoprim to 'steady-state' in normal volunteers.

Trimethoprim (TMP), previously available only with a sulphonamide, is now available alone. The kinetics of two dosage regimens (200 mg b.d. p o. and 300 mg o.d. p.o.) have been examined. The expected disposition of higher TMP concentrations following the initial dose of the 300 mg preparation is reversed when steady-state is reached, and is a function of dosage. The MIC of TMP for sensitive organisms in urine was greatly exceeded following both regimens and is the result of a favourable pH gradient. The serum concentrations at CSS (trough) following the 300 mg regimen did not consistently exceed the MIC for TMP, those for the 200 mg regimen were more satisfactory. The implications of these findings are that while both regimens would be satisfactory in the treatment of urinary tract infection the 200 mg regimen would be more appropriate for the treatment of infected sites where pH dependent accumulation of TMP does not occur.

Adult↗
PubMed1983

Compression arthrodesis of the ankle. Evaluation of a cosmetic modification.

Between 1955 and 1979, a modification of the compression arthrodesis of the ankle was performed in twenty-eight patients at The Campbell Clinic. The ages of the patients ranged from twenty-one to seventy-seven years, with an average of 48.4 years. The modification narrows both the medial and lateral sides of the ankle, resulting in a much better cosmetic appearance as the fused ankle is essentially the same width as the normal ankle. The distal end of the tibia and the talus are easily approached through anteromedial and anterolateral incisions, and all articular cartilage can be removed without difficulty. A solid arthrodesis was achieved in 92.8 per cent of the ankles, a higher percentage than in most reported series. Not only is the final appearance of the ankle more pleasing to the patient, but the modification also eliminates the complication of irritation and abrasion of the soft tissue beneath the malleoli by the top of the shoe.

Adult↗
PubMed1983

The handicapped in sports.

The first U.S.O.C. workshop on sports medicine for the handicaPped athlete led to several conclusions. First and foremost, the disabled athlete as an amateur athlete with a desire to participate must ever be uppermost in our minds, hearts, and planning. It appears that one of our chief objectives within the U.S.O.C. should be a central unifying force operating with joint support of the Sports Medicine Council and the Handicapped in Sports Committee, under the Sports Medicine Division. This arrangement will serve as an information and clearing center for the better understanding of each other and each organization of sports for the disabled athletes. We need to identify and classify for attention the common problems inherent among these groups and coordinate our various efforts. Fundamental to improvement in the application of sports medicine concepts is development of a definite plan for the education of voluntary coaches and trained or professionally prepared coaches, athletic trainers, physical therapists, and physicians. A variety of concurrent approaches are feasible with initiative and sharing of resources. An additional venture must be to begin pooling and computerizing our present and future information in this regard (professional articles and medical records) within the U.S.O.C. information retrieval system. This must be systematized so the pertinent information can then the disseminated and furnished nationwide to anyone or any group dealing with the disabled athlete in sports. Ultimately, our objective is to make this information available to all handicapped people.(ABSTRACT TRUNCATED AT 250 WORDS)

Athletic Injuries↗