Search PubMed⌕ Search

Biomedical subjects

M Walker

Publications and source records attributed to M Walker.

At least 487 records · Page 27Linked to original sources
PubMed1986

Electron microscope study of the effect of temperature on the length of the tail of the myosin molecule.

The effect of temperature on the length of the tail of the myosin molecule has been studied by negative staining of molecules immobilized on carbon substrates at different temperatures. In buffers containing chloride as the principal anion, tail length was approximately constant up to 25 degrees C. Above this temperature, it shortened linearly with increasing temperature up to 42 degrees C, the highest temperature studied in this solvent. The amount of shortening per degree C was about 1.2 nm. A similar amount of shortening per degree C was seen in acetate-containing buffers up to 50 degrees C, but in this case it did not begin until the temperature exceeded about 40 degrees C. A large fraction of the observed shortening was localized in a region that lies roughly between the two positions in the tail where proteolysis results in production of short or long subfragment-2. Frequently, the tail had a different appearance in this region from elsewhere and could sometimes be seen to split into two strands that were separate but coiled around one another.

Macromolecular Substances↗
PubMed1986

Benign villous adenomas of the ampulla of Vater.

One of the most unusual sites of isolated villous adenomas is the ampulla of Vater. Six patients with this neoplasm have recently been identified. The mean age was 68 years, and four were female. Four of the six were evaluated on several occasions before definitive diagnosis. Preoperative endoscopy correctly identified the lesions in two of three patients. Five patients underwent local resection and one a radical pancreaticoduodenectomy. Six benign neoplasms of the ampulla were found. In discussing this entity, of which there have been 38 reported cases in the literature, the role of local excision that can be combined with more complex procedures such as sphincteroplasty and duct implantation should be emphasized.

Adenoma↗
PubMed1986

Identifying men at high risk of heart attacks: strategy for use in general practice.

A strategy was devised for identifying men at high risk of acute myocardial infarction or sudden ischaemic death. A risk score was devised using cigarette smoking, mean blood pressure, recall of ischaemic heart disease or diabetes mellitus diagnosed by a doctor, history of parental death from "heart trouble," and the presence of angina reported on a questionnaire. The top fifth of the score distribution identified 53% of ischaemic heart disease cases--that is, men who subsequently experienced major ischaemic heart disease over the next five years. The addition of serum total cholesterol concentration and electrocardiographic evidence only slightly improved prediction (to 59%) and would have considerably increased the cost and effort of screening. Using this risk score on an opportunistic basis could be particularly valuable in general practice. Management of this high risk group is regarded as appropriate medical care and is complementary to the population approach to preventing ischaemic heart disease. Such a strategy for reducing the incidence of and mortality from ischaemic heart disease in men at high risk would also increase professional and public awareness of the need for preventive action.

Adult↗
PubMed1986

Data corruption.

Explore the source record for details and available documents.

Computers↗
PubMed1986

High density lipoprotein cholesterol is not a major risk factor for ischaemic heart disease in British men.

The concentration of high density lipoprotein cholesterol (HDL cholesterol) in serum was measured at initial examination in a large prospective study of men aged 40-59 drawn from general practices in 24 British towns. After an average follow up of 4.2 years 193 cases of major ischaemic heart disease had been registered in 7415 men in whom both HDL cholesterol and total cholesterol values had been measured. The mean HDL cholesterol concentration was lower in the men with ischaemic heart disease ("cases") compared with other men, but the difference became small and non-significant after adjustment for age, body mass index, blood pressure, cigarette smoking, and concentration of non-HDL cholesterol. The higher mean concentration of non-HDL cholesterol in "cases" remained highly significant after adjustment for other factors. Men in the highest fifth of non-HDL cholesterol values had over three times the risk of major ischaemic heart disease compared with men in the lowest fifth. Multivariate analysis showed that non-HDL cholesterol was a more powerful predictor of risk than the HDL to total cholesterol ratio. These British findings were compared with six other prospective studies. All the larger studies showed similar results, suggesting that HDL cholesterol is not a major risk factor in the aetiology of ischaemic heart disease.

Adult↗
PubMed1986

Partial plasma exchange in patients with AIDS and Kaposi's sarcoma. Plasmapheresis in AIDS.

Intensive plasma exchange was performed in seven male homosexual patients with AIDS and Kaposi's sarcoma. Serial 1.2 plasma volume exchange procedures were performed three times a week for six weeks. In five of the patients, plasma replacement included gamma globulin in the form of plasma (two patients), or an IV IgG preparation (three patients). No changes in the mean number of helper-inducer or suppressor-cytotoxic cells were noted during the treatment period or the weeks following completion of the last procedure. The mean mitogenic response of the patients' lymphocytes to PHA increased by 32.4% during the course of the plasmapheresis procedures (p less than .05), but returned to baseline over the eight weeks following treatment. Mitogenic responsiveness to PWM did not significantly increase during the course of treatment. No regression of Kaposi's sarcoma lesions was found in any of the patients treated.

Acquired Immunodeficiency Syndrome↗
PubMed1986

The influence of denier and porosity on performance of a warp-knit Dacron arterial prosthesis.

The study objective was to determine the optimal water porosity for a warp-knit, externally veloured Dacron arterial prosthesis. Preclotting efficiency, surgical handling characteristics, thrombogenicity, and 56-day healing in the descending thoracic aorta of mongrel dogs were measured for seven different arterial prostheses of the same basic design constructed to test the influence of decreased porosity produced by increased yarn denier at a constant needle density. The six prototypes tested were 160, 180, 200, 220, 240, and 280 denier. The 140 denier prosthesis (Bionit, C. R. Bard, Inc., Billerica, MA) served as the control. The water porosity of these prostheses varied from 2036 ml/cm2/min at 120 mmHg for the control to 286 for the 280 prototype. The preclotting efficiency increased with decreased water porosity and with increased outer-wall filamentousness. Desirability of surgical handling characteristics decreased with lowered water porosity, while the degree of outer-wall filamentousness had little influence. All the prostheses showed excellent through-wall healing at 56 days, including endothelialization. The 160 prototype represented an optimal blend of high preclotting efficiency, desirable surgical handling characteristics, and excellent 56-day healing. These studies are pertinent to the future development of porous, warp-knit Dacron arterial prostheses.

Animals↗
PubMed1986

Excess of DR3/4 in type I diabetes. What does it portend?

The HLA-DR genotypes of 158 new type I diabetic probands from simplex families are compared with those of 43 multiply affected sibships. There were no significant differences in the gene frequencies of the insulin-dependent diabetes mellitus (IDDM)-associated alleles, DR3 and DR4, and whereas the DR3/4 heterozygotes were as frequent among simplex probands as among the first affected of multiplex sibships, subsequently affected sibs displayed lower frequencies of this genotype in this as well as in previously reported samples, indicating that the excessive risk associated with DR3/4 heterozygosity depends on the order of affection and thus on environmental factors. It is proposed that the penetrance of the susceptibility gene is enhanced by epistatic effects of this genotype and that this enhancement is strongest under conditions of low environmental liability. Thus, the excessive risk for DR3/4 individuals appears to depend on secondary interactions between DR and the environmental factors that trigger the onset of this disease and does not in itself indicate the existence of distinct susceptibility alleles in coupling with these genes, i.e., of genetic heterogeneity or overdominance.

Alleles↗
PubMed1986

Effects of acetylpromazine on the hemodynamics of the equine metatarsal artery, as determined by two-dimensional real-time and pulsed Doppler ultrasonography.

Heart rate, blood velocity, volumetric blood flow, and arterial diameter for 10 horses given acetylpromazine were determined from measurements of the dorsal metatarsal artery 3 (the great metatarsal artery), using 2-dimensional real-time and gated pulsed Doppler ultrasonography. Acetylpromazine induced significant increases in arterial diameter (P less than 0.01) and volumetric flow rate (P less than 0.05)--all compatible with adrenergic blockade. There was a trend indicating that there was increased blood velocity. Heart rate was unchanged.

Acepromazine↗
PubMed1986

Sickle cell crisis and the acute abdomen.

Abdominal pain is one of the most common symptoms in sickle cell crisis, and its cause remains controversial. Simple vaso-occlusive crisis may be an explanation. The abdominal pain may also reflect an acute surgical abdomen.A patient presented with sickle cell crisis and abdominal pain; he had a periappendiceal abscess at the site of an appendiceal stump five months after appendectomy. The role of sickle cell anemia in the pathogenesis of this abscess is uncertain.

Abdomen, Acute↗
PubMed1985

Negative staining of myosin molecules.

A reproducible method has been developed for the negative staining of myosin molecules. The dimensions of stained molecules are in close agreement with those obtained by metal shadowing. Sharp bends in the tail, indicative of hinge regions, were observed at two positions 44 nm and 76 nm from the head-tail junction. The tail was often ill-defined at the position of the first (44 nm) bend. The bend positions may be sites of proteolytic cleavage that result in the production of long and short myosin subfragment S2. About half the molecules exhibited bending to various degrees at one or both of these positions, but cases where the tail folded back on itself in a 180 degrees bend were comparatively rare (approximately equal to 10%). However, in the absence of EGTA, a large fraction of the molecules (approximately equal to 80%) exhibited 180 degrees bends. A small region, approximately 20 nm long, at the tip of the tail often appears to be significantly different from the rest. The heads are about 19 nm long and roughly pear-shaped. Although sometimes straight, more often they show a pronounced curvature. Both senses of curvature were observed, but those curved in a clockwise manner were the most common, indicating preferential binding of one side of the head to the carbon substrate. An analysis of the different combinations of head shapes in individual molecules indicates that each head can rotate independently around its long axis. No preferred angle of orientation between the two heads in a molecule, or between either head and the tail could be found. Substructure has been observed within the heads.

Animals↗
PubMed1985

Costal bone changes similar to hypertrophic osteopathy associated with pulmonary and abdominal mesothelioma in a dog.

An 8-year-old male Irish Setter was admitted because of nonweight bearing lameness of the left forelimb. Radiography failed to reveal any bony lesions of the forelimb; however, extensive periosteal new bone formation over most rib surfaces and an atypical cardiac silhouette suggestive of a mediastinal mass with pleural effusion were observed. New bone formation was seen on the ilium and a filling defect in the urethra, distal to the prostate, was apparent with contrast urethrocystography. Necropsy revealed scirrhous mesothelioma of the thorax and abdomen, multifocal periosteal exostoses, paraprostatic cyst, and benign prostatic cystic hyperplasia. Tumor cells were associated with the periosteal exostotic costal bone. The specific cause of the lameness was not determined.

Abdominal Neoplasms↗
PubMed1985

Cerebral blood flow and cognitive testing correlate in Huntington's disease.

Brain atrophy estimated by computed tomographic (CT) scanning and mean hemispheric and regional gray matter cerebral blood flow (CBF) values were measured in patients with mild to moderate Huntington's disease (HD) (N = 16) using the xenon Xe 133 inhalation method and in asymptomatic blood relatives at risk from HD (N = 6) using both the xenon Xe 133 inhalation and the stable xenon CT contrast CBF methods. Results were compared with measurements in two groups of age-matched normal volunteers (N = 48 and N = 42, respectively). Significant brain atrophy in the vicinity of both caudate nuclei was present in patients with HD but not in at-risk individuals. Mean hemispheric xenon Xe 133 CBF values were reduced in patients with HD but seemed to be normal in at-risk individuals. In HD, reductions in CBF were found in both frontotemporal regions. Correlations were found between severity of dementia estimated by reductions of Mini-Mental Status Questionnaire scores and reductions of either mean hemispheric or regional frontotemporal CBF values in HD. The CT estimates of brain atrophy and three-dimensional CBF by stable xenon-contrast measurements were normal in asymptomatic individuals at risk from HD.

Adult↗
PubMed1985

Conceptual organization and memory in nonretarded, mildly retarded, and moderately retarded adults.

Moderately retarded, mildly retarded, and nonretarded adults learned a list of 12 items from three categories to a criterion of 75% correct recall in a free-recall learning paradigm. Retention was measured 1 week later. The moderately retarded took more trials and had lower retention and clustering scores than the others. The mildly retarded took more trials and had lower retention than the nonretarded. The results violate Murdock's total time hypothesis (Cooper & Pantle, 1967) but support Mandler's (1967) contention that learning is enhanced by the mental capacity for organization.

Adult↗