Search PubMed⌕ Search

Biomedical subjects

P Walker

Publications and source records attributed to P Walker.

At least 163 records · Page 9Linked to original sources
PubMed1990

Skeletal muscle metabolism in the leg during exercise in patients with congestive heart failure.

1. Using 31P nuclear magnetic resonance, it has previously been demonstrated that patients with congestive heart failure exhibit a greater than normal phosphocreatine (PCr) depletion in the working skeletal muscles of the arm. We have studied the importance of the work necessary to reach a similar PCr depletion ([PCr]/([PCr] + [Pi]) = 0.5) in calf muscle. Our results show significantly lower values for patients with congestive heart failure in both aerobic and ischaemic conditions (respectively: 0.009 +/- 0.007 vs 0.026 +/- 0.013 W/kg body weight, P less than 0.01; 0.29 +/- 0.16 vs 0.90 +/- 0.25 J/kg body weight, P less than 0.01). 2. This original model of skeletal muscle exercise facilitates a comparison of PCr recovery rate due to a similarity in the PCr depletion and intracellular pH in the two series at the start of recovery. However, the PCr recovery rate is similar after both normoxic and ischaemic exercise, i.e. respective percentages of PCr increase in the first 25 s recovery spectrum were: (a) aerobic exercise, congestive heart failure 133 +/- 18%, control series 138 +/- 18%; (b) ischaemic exercise, congestive heart failure 114 +/- 13%, control series 118 +/- 12%. The absence of a difference in PCr recovery rate and the greater PCr depletion by ischaemic work in patients with congestive heart failure suggest modifications that cannot be explained by a reduced blood flow to the muscle. 3. When comparing the two series, intracellular pH evolved similarly in normoxia and ischaemia during both work and recovery. Thus, no increase in anaerobic glycolytic activity appears when equivalent PCr depletion has occurred.

Adult↗
PubMed1990

Computer aided time-lapse video analysis of hepatocyte morphology during adhesion to cellulose membranes.

An investigation was performed to demonstrate that time-lapse cinematography and computer aided video analysis of cell morphology is suitable to study and compare the characteristics of hepatocytes during the adhesion process to membranes. We chose to compare ordinary cellulose Cuprophan membranes and membranes coated with collagen or fibronectin. Striking differences between uncoated cellulose and fibronectin or collagen coating were seen in the cell count per square millimeter and adhesion behaviour. On the investigated uncoated Cuprophan the hepatocytes were found to attach but not to spread whilst on collagen coated Cuprophan most of the cells spread spherically, and on fibronectin coated membranes most of the cells flattened spherically or polygonally. Time-lapse video microscopy seems to be a valuable technique for assessing the morphologic behaviour of cells in a detailed and quantitative manner in order to improve the hepatocyte culture technique in bioreactors for hybrid systems.

Animals↗
PubMed1989

Immunogenicity of synthetic peptides derived from the sequences of a Streptococcus mutans cell surface antigen in nonhuman primates.

The immunogenicity and antigenicity of synthetic peptides (SP) derived from the sequences of a cell surface Ag of Streptococcus mutans were investigated in macaque monkeys. Immunization with the free peptides of 11, 17, and 21 residues failed to elicit serum antibodies or T cell responses. However, immunization with the SP17 and SP21 linked to tetanus toxoid (TT) as a carrier elicited serum antibodies and proliferative responses of lymphocytes, not only to the SP but also to the native streptococcal Ag. In vivo recall of SP-TT immunized monkeys with suboptimal doses of the native streptococcal Ag resulted in a significant increase in antibodies, both to the SP and the streptococcal Ag, confirming that the SP shares antigenic epitopes with the native Ag. B and T cell epitopes were then determined and a B cell epitope was found in residues 8-13, whereas an overlapping T cell epitope was located in residues 7-15. The T cell epitope has an amino-terminal leucine and carboxy-terminal glycine and alanine added to residues 8-13 of the B cell epitope. In spite of the B and T cell epitopes being expressed in SP17 (residues 1-15), the monomer failed to induce serum antibodies without a carrier. However, immunization with a dimer of SP17 elicited both serum antibodies and proliferative responses of lymphocytes without a carrier. The results suggest that the monomeric SP17 is not immunogenic and needs to be dimerised in order to elicit antibodies and T cell responses, both to the SP and to the streptococcal Ag.

Amino Acid Sequence↗
PubMed1989

Cognitive function and regional cerebral blood flow in partial seizures.

Patients with partial seizures have cognitive function impairments that have been attributed to the toxic side effects of anticonvulsants and structural cerebral damage. However, even when these factors are absent, neuropsychological (NP) deficits have been demonstrated, although of milder degree than in structurally brain-damaged patients. Assessment of cerebral metabolism using positron emission tomography and cerebral blood flow with single photon emission computed tomography (SPECT) reveals focal physiologic deficits in structurally normal areas. Using both SPECT and NP assessment with the Halstead-Reitan Battery, we evaluated 50 patients with partial seizures. Comparison of the location of visually identified regional cerebral blood flow (rCBF) deficits in these patients with the location of the NP deficits revealed a significant correlation. Additional analyses indicated that rCBF quantification in visually identified areas of hypoperfusion was significantly lower than in "normal" areas and that quantified NP variables significantly discriminated patients with and without visual rCBF deficits in temporal and frontal brain regions.

Adult↗
PubMed1989

Renal cystic disease of infancy: results of histochemical studies. A report of the Southwest Pediatric Nephrology Study Group.

Histochemical techniques utilizing Tetragonolobus lotus (proximal tubules), Arachis hypogaea (distal nephron, i.e., distal convoluted tubules and collecting ducts), and antibodies against Tamm-Horsfall protein (thick ascending limbs of Henle) were used to determine the site of origin of renal cysts in five children with autosomal recessive polycystic kidney disease (ARPKD) and three patients with glomerulocystic disease (GCD) presenting in the 1st year of life. The findings support a distal nephron origin for the cysts in the children who had ARPKD, whereas the majority of cysts in the children with GCD were confirmed as having a glomerular origin. Tamm-Horsfall protein was identified in the cysts of both ARPKD and GCD; this finding suggests free communication between some of the cysts with the thick ascending limb of Henle. An unexpected finding was the frequent presence of cysts surrounded by muscle fibers. We suggest that these cysts are of collecting duct origin.

Child↗
PubMed1989

The accuracy of repeat cytology in women with mildly dyskaryotic smears.

A special colposcopy clinic was established at the Royal Free Hospital to investigate women whose referral smears showed mild dyskaryosis. Of 200 women in the study, 66 (33%) had histologically proven CIN II or CIN III, 59 (29%) had CIN I or human papillomavirus changes, and 54 (27%) were considered normal. These findings demonstrate the importance of adequate diagnosis of this group of women. Of 143 women who had had a single mildly dyskaryotic smear, 45 (31%) had either CIN II or III. Age was not useful for predicting which women were at high risk of significant disease. Careful repeat cervical cytology correlated closely with the histological grade of the lesion. Repeat cytology was associated with an overall 24% false-negative rate, but most missed lesions were of low grade. Repeat cytology correctly identified 82% of all CIN lesions, and 93% of the most significant lesions (CIN II and III). Women who have a mildly dyskaryotic smear followed by a negative smear should not be considered normal, but careful repeat cytology can be considered a reasonably safe practice.

Adolescent↗
PubMed1989

Typographic influences on reading.

The research reported here comprises an empirical investigation of the phenomenon of typographic allusion. In a preliminary study, subjects rated the perceptual qualities possessed by different typefaces (e.g. heavy-light, fast-slow). The results indicated that subjects agreed as to typeface characteristics and that typefaces were distinguished by such qualities. In Expt 1, subjects undertook a speeded decision task in which they responded according to which one of four adjectives appeared tachistoscopically. Each word appeared in a typeface whose qualities were either consistent or inconsistent with its meaning. Reaction times for inconsistent stimuli were significantly slower than those for consistent trials. In preparation for Expt 2, the same rating procedure was used to elicit subjects' judgements of the attributes of different animals. Subjects agreed as to animals' qualities and such qualities reliably distinguished between the animals. The names of these animals were then used as targets in a binary decision task and each one appeared in a typeface possessing qualities which were either congruent or incongruent with those of the animal. Subjects responded according to whether they considered the animal presented on each trial to be heavy or light, or fast or slow moving. Responses on trials in which the animal and typeface possessed conflicting attributes were significantly slower than responses when animal and typeface qualities were congruent. These results are discussed in relation to current views regarding the processing of written English. We argue that typographic features of words are able to access a semantic code and that this code can interact with the derivation of a linguistic code specifying a word's meaning and/or with post-lexical access decision processes.

Decision Making↗
PubMed1989

A comparison of amlodipine, verapamil and placebo in the treatment of mild to moderate hypertension. Amlodipine Study Group.

This is a double blind parallel group comparison in patients with mild-moderate hypertension, of amlodipine, verapamil and placebo. One hundred and sixty patients entered the double blind phase. In the amlodipine group the mean supine and standing systolic pressures at week 12 were respectively lowered from baseline by 11.9 mmHg and 11.3 mmHg more than for the placebo group (P = 0.0001). Diastolic blood pressures were also significantly reduced. With verapamil the mean supine and standing systolic blood pressure at week 12 were reduced by 7.7 mmHg and 8.3 mmHg more on verapamil than on placebo (P = 0.0083). Blood pressures of the amlodipine group were lower 24 hour post-dose than verapamil 12 hours post dose. The responder rates after eight weeks of double blind therapy were amlodipine 72.3%, verapamil 47.8% and placebo 32.6%. Body weight after verapamil increased by mean 0.9 kg, after amlodipine by 0.2 kg and after placebo decreased by 0.2 kg. Six patients were withdrawn because of adverse effects (3 amlodipine, 2 verapamil, 1 placebo). The number of patients with adverse effects possibly related to therapy were 22/53 for amlodipine, 19/54 for verapamil and 14/53 for placebo. Both drugs were, overall, well tolerated, effective and had no unexpected adverse effects.

Adult↗
PubMed1989

Oropharyngeal mucositis complicating bone marrow transplantation: prognostic factors and the effect of chlorhexidine mouth rinse.

Oral mucosal ulceration complicating bone marrow transplantation interferes with patients' comfort, nutrition and may lead to systemic infection derived from the mouth. The mucosal injury results from epithelial damage due to the cytotoxic effects of chemotherapy and radiation conditioning as well as from superficial oropharyngeal infection. Because chlorhexidine gluconate is a broad spectrum topical antimicrobial which has been demonstrably effective in preventing oral infection and gingivitis, we performed a randomized, placebo controlled, double-blind trial of chlorhexidine as a mouth rinse in BMT recipients to study the severity of oral mucositis and both oral and systemic infectious complications. One hundred patients were randomly assigned to receive either chlorhexidine gluconate 0.12% mouth rinse or placebo three times daily from the initiation (day -8) of chemoradiotherapy conditioning until day +35 post-BMT. Chlorhexidine use resulted in a trend toward improved oral hygiene index (reduced dental plaque) (p = 0.06) but did not modify the oral mucositis. Patients using chlorhexidine developed a maximum ulceration of 18 +/- 22% of their oral mucosa, while placebo patients ulcerated 25 +/- 31% of the mouth. Ulcerative mucositis was significantly worse in adults compared with children, in individuals who received methotrexate for graft-versus-host disease prophylaxis, and was most prominent on non-keratinized epithelium. Overall, there was no clinically demonstrable additional therapeutic advantage to the use of chlorhexidine in either reducing the mucositis, controlling oral pain, facilitating oral nutrition, shortening hospital stay, or reducing oral infection with herpes simplex virus. There was a trend toward diminished oral candidiasis in chlorhexidine users (p = 0.06).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1989

The rate and distribution of muscle blood flow after prolonged ischemia.

The magnitude and distribution of muscle blood flow in the lower extremity after relief of an acute arterial occlusion may influence the extent of the resulting necrosis. The object of this study was to document the distribution of blood flow in the resting state and after prolonged periods of complete ischemia, and to assess the relationship between the degree of reactive hyperemia and subsequent necrosis. The isolated bilateral canine gracilis muscle preparation that we have previously characterized was used for microsphere studies. Total blood flow was measured by means of timed venous collections, and the distribution of flow was determined by means of a multiple microsphere injection technique. Measurements of microsphere distribution and blood flow were made before ischemia and during the initial 48 minutes of reperfusion after both 4 and 5 hours of normothermic ischemia, which resulted in 46.7% +/- 6% and 71.2% +/- 7% necrosis, respectively. The muscle was harvested and sectioned transversely into six slices approximately 1.5 cm thick, and the extent of necrosis was quantified by means of nitroblue tetrazolium staining 48 hours after reperfusion. Blood flow distribution during the early reperfusion phase was determined in each muscle slice and in both the alive and dead portions of each slice by use of the microsphere injection technique. Preischemic blood flow was distributed homogeneously throughout the muscle and was 4.5 +/- 0.8 ml/100 gm/min (mean +/- SEM, n = 8). On reperfusion total flow was 6 to 10 times higher than it was before ischemia and was distributed predominantly to the middle slices (p less than 0.05, n = 12).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Neonatal nursing.

Explore the source record for details and available documents.

Education, Nursing, Continuing↗
PubMed1988

The Xenopus laevis ribosomal gene promoter contains a binding site for nuclear factor-1.

Nuclear Factor I (NF1) is a DNA binding protein that is known to function in the replication of Adeno virus and also binds to many promoters recognized by RNA polymerase II. We have found that there is also an NF1 binding site within the ribosomal gene promoter from Xenopus laevis as well as in several other promoters recognized by RNA polymerase I. The function of a binding site for a polymerase II transcription factor within a promoter recognized by polymerase I is not known. However, its presence suggests interesting regulatory possibilities.

Animals↗