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Biomedical subjects

M Walker

Publications and source records attributed to M Walker.

At least 217 records · Page 12Linked to original sources
PubMed1998

Apparent blood stream origin of endothelial and smooth muscle cells in the neointima of long, impervious carotid-femoral grafts in the dog.

The purpose of this study was to determine whether endothelial and smooth muscle cells originating from the blood stream contribute to the endothelialization of impervious, small-caliber, long Dacron grafts used as extraanatomical bypasses in dogs. We implanted silicone-rubber-coated, permanently impervious grafts 64 to 77 cm long and 6 mm in diameter, made of externally supported knitted Dacron as unilateral carotid-femoral bypasses with distal femoral arteriovenous fistulae in 10 dogs for 3 months; sides were alternated between cases. Subjects received 162 mg/day of aspirin, and its effectiveness on platelet aggregation (PA) was evaluated and expressed as a PA score. Graft healing was studied by stereomicroscopy with silver nitrate staining, by light microscopy with hematoxylin-eosin and immunocytochemical staining for endothelial and smooth muscle cells, and by scanning and transmission electron microscopy. Five grafts were patent for 3 months and could be included in the healing study; the five occluded grafts thrombosed within 14 days. Although there was no transinterstitial tissue ingrowth from perigraft tissues into the impervious Dacron grafts, scattered islands of endothelial cells were conclusively demonstrated on graft flow surfaces 3 months after implantation. Average endothelial-like cell coverage of the flow surfaces was 15.6% +/- 3.8%, and alpha-actin-positive smooth muscle cells and microvessels were found beneath some of the endothelial islands. These findings suggest that blood stream-derived endothelial and smooth muscle cells play a role in the healing of the inner wall of Dacron grafts in the dog.

Animals↗
PubMed1998

Lipoprotein composition and serum apolipoproteins in normoglycaemic first-degree relatives of non-insulin dependent diabetic patients.

Cardiovascular disease is the leading cause of death in non-insulin dependent diabetes mellitus and first degree relatives of such patients are at increased risk of developing diabetes and cardiovascular disease. The aim of the present study was to determine whether lipid abnormalities occur in normoglycaemic relatives of non-insulin dependent diabetic patients. Cholesterol, triglycerides, apolipoprotein A-I and apolipoprotein B concentrations were measured in serum; the lipoprotein fractions very low density, intermediate density, low density and high density lipoprotein were prepared by sequential flotation ultracentrifugation and their composition investigated. The groups were matched for age, sex and blood glucose concentrations although the relatives (n = 126) were more insulin resistant as determined using the homeostasis model assessment method [1.9 (0.8-9.0) vs 1.6 (0.4-4.9) mmol/mU per l (mean [95% confidence intervals]); p < 0.001] and had greater body mass indices [26.6 (4.1) vs 24.8 (3.9) (mean [S.D.]); p = 0.001] than control subjects (n = 126). Relatives had higher serum apolipoprotein B concentrations than control subjects [0.9 (0.3) vs 0.8 (0.3) g/l, p = 0.02) and lower serum apolipoprotein A-I concentrations (1.4 (0.3) vs 1.5 (0.3), p = 0.02). In multivariate linear regression analysis of all subjects log insulin resistance (p = 0.0001), age (p = 0.002) and waist:hip ratio (p = 0.01) were independent predicators of apolipoprotein B concentrations while waist:hip ratio (p < 0.001) and smoking status (p = 0.002) were independent predictors of apolipoprotein A-I concentrations. Lipoprotein composition (measured in a subgroup of 76 control subjects and 88 relatives), serum cholesterol and serum triglyceride concentrations did not differ between the groups. We conclude that atherogenic apolipoprotein abnormalities occur in normoglycaemic relatives of non-insulin dependent diabetic patients.

Adult↗
PubMed1998

Efficacy of vestibular rehabilitation.

The purpose of this study was to determine significant changes in the Dizziness Handicap Inventory (DHI) scores in patients before and within 1 year after a vestibular rehabilitation program. Efficacy of a vestibular rehabilitation program was tested retrospectively in 37 patients by comparison of pretreatment and posttreatment DHI scores. A significant improvement in test scores was found, indicated by the Sign test at the 0.05 level after vestibular rehabilitation. This difference is evident in the total score and in the functional and physical subscore component. Prerehabilitation and postrehabilitation differences among diagnostic categories were analyzed by using the Kruskal-Wallis test. Patients with peripheral lesions demonstrated greater improvement in the emotional component of the DHI as compared with patients with central or mixed lesions. The Wilcoxon two-sample test assessed the influence of compliance with a home exercise program after discharge from a vestibular physical therapy program. There was no significant difference in improvement between patients who performed home exercises for at least a month after discharge and those who did not.

Adult↗
PubMed1998

The toilet as a transmission vector of vancomycin-resistant enterococci.

An elderly woman, admitted to the intensive care unit of a large university teaching hospital, was found to be colonized with vancomycin-resistant enterococci leading to the temporary closure of the unit. She had acquired the organism nosocomially, most likely from an environmental source, which had been contaminated when the toilet of a former patient, also colonized with vancomycin-resistant enterococci, had become blocked and overflowed throughout his and the adjoining room. This is the first report of a hospital toilet as the transmission vector for vancomycin-resistant enterococci.

Aged↗
PubMed1998

Professional knowledge, midwifery and the role of the external examiner.

Following the move of midwifery education into institutions of higher education (IHE), professional sources have voiced some concern over the apparent 'cultural conflict' between IHE and the midwives. In order to investigate this, a 1-day conference was convened for midwife teachers and external examiners in the south of England, during which data were collected from recorded discussions and interviews. The findings confirm the existence of conflict which polarized around two issues: first, the centrality of practice for midwives and the perceived undermining of that practice by the academically orientated IHE; and second, the somewhat ambiguous role of the external examiner. These findings are explained in terms of recent work on professionalization which suggests that professional knowledge can be legitimized where the emphasis is placed on the indeterminate elements of the work and where knowledge originates from abstractions and conceptualizations derived from working practice. Such a knowledge base would be rather more resistant to undermining by the deductive, rationalist approach employed by IHE academics. It is suggested that external examiners are best placed to represent practice based knowledge to IHE examiners.

Conflict, Psychological↗
PubMed1998

False allegations of pregnancy resulting from incestuous rape and physician misconduct: proof positive.

BACKGROUND: The veracity of adult allegations of remote childhood sexual abuse have been the focus of intense debate fueled by the controversy over both repressed and false memory syndromes. Likewise, increased awareness of physician misconduct in recent years has mandated numerous policy statements and task force guidelines to protect patients. CASE: A 23-year-old woman alleged that she had suffered incestuous rape at age 12 years, resulting in pregnancy. She named a physician who she claimed had performed an illegal pregnancy termination. Subsequent evaluations revealed that she had uterovaginal agenesis. CONCLUSION: Neither sexual abuse nor physician misconduct should be tolerated, and all such allegations deserve thorough and expeditious investigations. However, we must remain cognizant that any such allegation may be false and have devastating consequences for the unjustly accused.

Abortion, Illegal↗
PubMed1998

Effects of impaired renal function on the pharmacokinetics of raltitrexed (Tomudex ZD1694).

This open-label, non-randomized, parallel-group trial investigated the pharmacokinetics of raltitrexed (Tomudex, formerly ZD1694) after a single intravenous dose of 3.0 mg m(-2), comparing eight cancer patients with mild to moderate renal impairment (creatinine clearance 25-65 ml min(-1)) with eight cancer patients with normal renal function (creatinine clearance >65 ml min(-1)). The primary end points were area under the plasma raltitrexed concentration-time curve from the start of the infusion to the last determined concentration (AUC(0-tldc)) and AUC to infinity (AUC(0-infinity)); secondary end points were peak concentrations of raltitrexed (Cmax) and elimination half-life (t(1/2gamma)). The groups were compared statistically using analysis of covariance. The AUCs were greater for patients with renal impairment than for patients with normal renal function (2452.2 compared with 1247.3 ng h ml(-1) for AUC(0-tldc) (ratio 1.97; 95% CI 1.36-2.84); 2961.5 compared with 1457.0 ng h ml(-1) for AUC(0-infinity) (ratio 2.03; 1.25-3.29). These differences were statistically significant (P = 0.002 and P = 0.008 for AUC(0-tldc) and AUC(0-infinity) respectively. Terminal half-life was longer for the renally impaired patients (271.2 compared with 143.3; P = 0.030). There was no significant statistical difference between the groups for Cmax (652.9 compared with 564.7 ng ml(-1) for patients with impaired and normal renal function respectively: ratio 1.16; 0.91-1.46; P = 0.204). There was a clear relationship between raltitrexed clearance and creatinine clearance. Adverse events, severe (WHO grade 3 or 4) toxicity and hospitalization due to adverse events were more frequent in the group with renal impairment. Therefore, a reduction in raltitrexed dose and increased interval between doses is recommended for patients with mild to moderate renal impairment.

Adult↗
PubMed1998

Biosynthesis and metabolism of native and oxidized neuropeptide Y in the hippocampal mossy fiber system.

Neuropeptide Y (NPY) gene expression is known to be modulated in the mossy fiber projection of hippocampal granule cells following seizure. We investigated NPY biosynthesis and metabolism in an attempt to characterize NPY biochemically as a neurotransmitter in the granule cell mossy fiber projection. NPY biosynthesis was compared in normal control animals and in animals that had experienced a single pentylenetetrazole-induced seizure. In situ hybridization analysis established the postseizure time course of preproNPY mRNA expression in the hippocampal formation, localizing the majority of increased preproNPY mRNA content to the hilus of the dentate gyrus. Radioimmunoassay analysis of the CA3/mossy fiber terminal subfield confirmed a subsequent increase in NPY peptide content. Biosynthesis of NPY peptide by granule cells and transport to the CA3/mossy fiber subfield was demonstrated by in vivo radiolabel infusion to the dentate gyrus/hilus followed by sequential HPLC purification of identified radiolabeled peptide from the CA3/mossy fiber terminal subfield. Additional in vivo radiolabeling studies revealed a postseizure increase in an unidentified NPY-like immunoreactive (NPY-LI) species. HPLC/radioimmunoassay analyses of CA3 subfield tissue extracts comparing normal control animals and pentylenetetrazole-treated animals confirmed the increased total NPY-LI, and demonstrated that the increased NPY-LI was comprised of a minor increase in native NPY and a major increase in the unknown NPY-LI. Data from subsequent and separate analyses incorporating immunoprecipitation with anti-C-terminal flanking peptide of NPY, further HPLC purification, and matrix-assisted laser desorption/ionization mass spectrometry support the conclusion that the unknown NPY-LI is methionine sulfoxide NPY. NPY and NPY-sulfoxide displayed differential calcium sensitivity for release from mossy fiber synaptosomes. Similar to NPY, NPY sulfoxide displayed high-affinity binding to each of the cloned Y1, Y2, Y4, and Y5 receptor subtypes. Postrelease inactivation of NPY was demonstrated in a mossy fiber synaptosomal preparation. Thus, the present study in combination with previously reported electrophysiological activity of NPY in the CA3 subfield demonstrates that NPY fulfills the classical criteria for a neurotransmitter in the hippocampal granule cell mossy fiber projection, and reveals the presence of two molecular forms of NPY that display differential mechanisms of release while maintaining similar receptor potencies.

Amino Acid Sequence↗
PubMed1998

Chest pain on questionnaire and prediction of major ischaemic heart disease events in men.

OBJECTIVE: To examine the prediction of major ischaemic heart disease events by questionnaire-assessed chest pain and other symptoms. DESIGN: Population-based prospective study. SUBJECTS: 7735 randomly selected men, aged 40-59 years at entry. METHODS: Symptoms and history of diagnosed ischaemic heart disease were ascertained by administered questionnaire at baseline. Follow-up was for an average of 14.7 years, for first major ischaemic heart disease event. RESULTS: During follow-up, 969 men had a major ischaemic heart disease event. 'Definite' angina (chest pain fulfilling all WHO criteria) and 'possible' angina (exertional chest pain without all other WHO criteria) were associated with similar ischaemic heart disease outcome, and a single combined angina category was used. In the whole cohort, the relative risks (95% CI) of a major ischaemic heart disease event were 2.03 (1.61, 2.57) for angina only, 2.13 (1.72, 2.63) for possible myocardial infarction only and 4.50 (3.57, 5.66) for angina plus possible myocardial infarction, compared to no chest pain. The relative risk for recall of an ischaemic heart disease diagnosis was 3.98 (3.36, 4.71). Only 33% of men with angina or possible myocardial infarction symptoms recalled a previous ischaemic heart disease diagnosis. In men without recall of an ischaemic heart disease diagnosis (in whom 82% of events during follow-up occurred), chest pain symptoms remained predictive of major ischaemic heart disease events with relative risks (95% CI) of 1.69 (1.27, 2.24) for angina only, 1.49 (1.12, 1.97) for possible myocardial infarction only and 2.55 (1.44, 4.53) for angina plus possible myocardial infarction. 'Other chest pain' increased risk of a major ischaemic heart disease event by 1.19 (1.01, 1.40) compared to no chest pain. Symptoms of breathlessness or calf pain on walking increased ischaemic heart disease risk in men with 'other chest pain' and in men without chest pain, but had no further effect on ischaemic heart disease risk in men with symptoms of angina or possible myocardial infarction. CONCLUSIONS: In defining angina by chest pain questionnaire, the exertional component is the crucial criterion. When using questionnaire-assessed symptoms to determine ischaemic heart disease risk, information on previous ischaemic heart disease diagnoses should be taken into account. The majority of men with angina or possible myocardial infarction symptoms do not have a diagnosis of ischaemic heart disease, but they remain at significantly increased risk of a major ischaemic heart disease event. The value of breathlessness and calf pain on walking in stratifying ischaemic heart disease risk is restricted to men with 'other chest pain' or no chest pain.

Adult↗
PubMed1998

Effect of cryopreservation on survival of composite tissue grafts.

The problems in cryopreserving complex tissues remain poorly understood. In the present study, the viability of cryopreserved complex tissue, including skin and muscle flaps, and tail, was compared to simple artery and vein grafts in a rat model. Forty-four grafts, including the femoral artery (n = 15), femoral vein (n = 9), gracilis muscle flap (n = 8), groin cutaneous flap (n = 9), and tail (n = 3) were cryopreserved at -196 degrees C for 1 to 2 weeks, and then microvascularly transferred to analogous sites in inbred recipient animals. Three to 60 days post-transplant, all cryopreserved femoral arteries and veins were patent. Host groin cutaneous flaps with cryopreserved vessels grafted into the arterial pedicle survived with no complications However, severe endothelial-cell damage with extensive sloughing in the grafts was demonstrated at 30 min and 1 week following reperfusion, using factor VIII immunologic stain. Reendothelialization was evident at 2 months postoperatively. All cryopreserved composite tissue underwent early pedicle thrombosis The muscle and cutaneous tissue also showed gross and microscopic edema, with extensive red-cell extravasation within 30 min of reperfusion Cryopreservation thus can maintain the functional integrity of simple vessel grafts, but these grafts survive only as a conduit, given the severe endothelial-cell damage The failure of transferred complex cryopreserved tissue may reflect a combination of cellular or architectural damage to the capillary bed from ice formation during the freezing process and from reperfusion injury.

Animals↗
PubMed1998

Acute effects on insulin sensitivity and diurnal metabolic profiles of a high-sucrose compared with a high-starch diet.

Decreased insulin sensitivity is associated with diabetes mellitus, ischemic heart disease, and hypertension, both independently and in association as what is called the metabolic syndrome. Although the negative effects of obesity, sedentary lifestyles, and high-fat diets on insulin sensitivity are well established, the influence of type and quantity of dietary carbohydrate is more controversial. This study aimed to assess the acute (24 h) effects of a high-sucrose compared with a high-starch diet on insulin sensitivity and to identify changes in blood metabolites that might lead to altered insulin sensitivity. Eight healthy adults consumed high-sucrose or high-starch diets (50% of dietary energy) in a randomized, crossover trial. Insulin sensitivity was assessed by a short insulin tolerance test the following morning. No differences were detected in insulin sensitivity, either for glucose metabolism [Kitt(glucose) (the rate constant for the decline in blood glucose concentrations) for sucrose diet = 3.86%/min, for starch diet = 3.72%/min; pooled SEM = 0.23] or for lipid metabolism [Kitt(NEFA) (the rate constant for the decline in blood fatty acid concentrations) for sucrose diet = 12.9%/min, for starch diet = 11.4%/min; pooled SEM = 1.18]. Profiles for blood glucose and serum insulin concentrations revealed higher peaks and lower troughs with the high-sucrose diet whereas area under the curve for glucose was higher with the high-starch diet (6780 +/- 245 mmol x L/min) than with the high-sucrose diet (6290 +/- 283 mmol x L/min) (P < 0.001). Plasma fatty acid concentrations showed a late postprandial rise with the sucrose-rich diet relative to the starch-rich diet, which was mirrored with a fractionally later peak in triacylglycerol concentrations.

Adult↗
PubMed1998

Children's willingness to share activities with a physically handicapped peer: am I more willing than my classmates?

OBJECTIVE: To examine factors affecting children's willingness to share activities with a peer presented as physically handicapped. METHOD: Participants were 120 elementary school children randomly assigned to view a video of an ambulatory child or the same child in a wheelchair. They rated, on the Shared Activities Questionnaire (SAQ), their own willingness (SAQ-Self) and their perceptions of classmates' willingness (SAQ-Others) to participate in activities with the child. RESULTS: SAQ-Self ratings were consistently higher for the peer in the wheelchair. On the SAQ-Others, differences favoring the child in the wheelchair disappeared, and ratings of this child were lower than SAQ-Self ratings. No interactions were found between ambulation status and age or rater gender or preference for type of shared activity. CONCLUSIONS: Children showed highly positive intentions toward a peer in a wheelchair, but intentions attributed to classmates were less positive, which suggests "social desirability" influenced their own ratings.

Child↗
PubMed1998

Outbreak of Acinetobacter spp. bloodstream infections in a nursery associated with contaminated aerosols and air conditioners.

BACKGROUND: Acinetobacter spp. are multidrug-resistant bacteria that grow well in water and cause infections with unexplained, increased summer prevalence. In August, 1996, eight infants acquired Acinetobacter spp. bloodstream infection (A-BSI) while in a nursery in the Bahamas; three infants died and an investigation was initiated. METHODS: A case patient was defined as any newborn in the nursery during August 6 to 13, 1996, with A-BSI. To identify risk factors for A-BSI we conducted a retrospective cohort study and performed environmental cultures and air sampling using settle plates. The genetic relatedness of environmental isolates was assessed by pulsed field gel electrophoresis. RESULTS: Of 33 patients in the nursery 8 (24%) met the case definition. Patients with peripheral iv catheters were more likely to develop A-BSI (8 of 21 vs. O of 10, P < 0.05). Multivariate analysis among patients with iv catheters indicated that only exposure to one nurse was an independent risk factor for developing A-BSI (P < 0.005). Nursery settle plates were more likely to grow Acinetobacter spp. than were settle plates from other hospital areas (8 of 9 vs. 0 of 5, P < 0.005); cultures from nursery air conditioners also grew Acinetobacter spp. Environmental isolates were genetically diverse. After installation of a new air conditioner in May, 1995, A-BSIs occurred more frequently during months of increased absolute humidity or environmental dew point. CONCLUSIONS: Acinetobacter spp. may cause nosocomial BSI and death among infants during periods of polyclonal airborne dissemination; breaks in aseptic technique during i.v. medication administration may facilitate transmission from the environment to the patient. Environmental conditions that increase air conditioner condensate may predispose to airborne dissemination via contaminated aerosols and increase the risk of nosocomial A-BSI.

Acinetobacter↗
PubMed1998

Template for surgical crown lengthening: fabrication technique.

This article describes a technique for the easy fabrication of a template to facilitate surgical lengthening of the clinical crown to enhance esthetics and/or increase retention of a fixed prosthesis. The use of this surgical guide should result in more predictable clinical results.

Crown Lengthening↗
PubMed1998

Relationship between foot pressure pattern and foot type.

Foot type and location of area of peak pressure under the metatarsal heads were determined for 54 healthy adults between the ages of 21 and 39 years. Feet were classified as neutral, pronated, or supinated. Each subject walked barefoot over a pedobarograph, and the area of peak pressure was identified as being either medial, central, or lateral under the metatarsal heads. A Fisher's exact test determined that there was a significant relationship between the area of peak pressure and foot type. A post hoc lambda asymmetric test showed that the relationship was very weak. Nearly half (49%) of the feet were classified as neutral, 36% were pronated, and 15% were supinated. Pressure patterns were as follows: 62% central, 26% medial, and 12% lateral. Other factors besides foot type influence the area of peak pressure under the metatarsal heads.

Adult↗