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Biomedical subjects

J Evans

Publications and source records attributed to J Evans.

At least 19 recordsLinked to original sources
PubMed1992

Systemic embolism as a complication of percutaneous mitral valvuloplasty.

Systemic embolism is a potential and severe complication of percutaneous mitral valve dilatation. In our series of 80 cases, the incidence of systemic embolism was 3.75% (3 cases). Two cases occurred during the procedure itself. The cause of embolism was different in each case: cruoric thrombus formation occurred in 2 cases during or after dilatation, and was attributable to inappropriate heparinization, and catheter and guidewire thrombogenicity. In both cases heparin administration was delayed or given at a lower dosage. In the third case, calcific embolism occurred several days after valve dilatation. We think that the embolic calcified fragment was detached from the mitral leaflet at the time of or after balloon inflation. In these 3 cases, intraatrial thrombus mobilization was not the mechanism of systemic embolism. In 2 cases, transesophageal echocardiography had been performed before dilatation and excluded the presence of an atrial thrombus the day before the procedure. It is concluded that, together with mobilisation of left atrial thrombi, which can be adequately detected by transesophageal echocardiography, catheter-induced thrombi represent a significant cause of embolic complications and must be prevented by giving full-dose heparin during the total duration of the procedure. Calcific embolism may also occur, and may become more frequent if mitral valve balloon dilatation is proposed to a larger number of patients with valvular and subvalvular calcifications.

Aged↗
PubMed1992

Involvement of a neutral glycolipid in differential cell adhesion in the Xenopus blastula.

Many different molecular species mediate cell adhesion during embryonic development. These can have either protein or carbohydrate functional groups, which can act in either a homophilic or a heterophilic manner, and often in concert. We report here that a monoclonal antibody, M4B, raised against Xenopus blastomere membranes, inhibits the calcium-dependent adhesion of dissociated blastomeres. M4B maintains its inhibitory effect on adhesion when converted into univalent fragments, and specifically affects calcium-dependent adhesion. The antigen is regulated in both space and time during early development. It is found on cell surfaces throughout the egg to blastula stages, but is more concentrated on cells in the animal and marginal zones of the blastula. It is dramatically downregulated during gastrulation, and becomes largely restricted to gut epithelium by the larval stages. We show also that M4B function is spatially differentiated at the blastula stage, since it inhibits the aggregation of dissociated animal cells to a greater extent than vegetal cells. This membrane antigen may therefore play a role in the differential adhesion observed between different regions of the blastula, and which we presume to underlie the segregation of the primary germ layers during gastrulation. M4B recognizes a complex of plasma membrane glycolipids. Periodate treatment destroys the ability of these glycolipids to react with the antibody, indicating that the epitope resides in the carbohydrate moiety of the glycolipids. Chemical characterization shows that it is a neutral glycolipid, and that the major component is of the glycoglycerolipid, rather than the more common glycosphingolipid class. Blocking experiments with oligosaccharides of defined structure, and antibody crossreactivity show that the M4B antibody does not recognize several known embryonic carbohydrate antigens. These results demonstrate that M4B antibody recognizes a novel group of developmentally regulated glycolipids which function in calcium-dependent cell--cell adhesion in the Xenopus blastula.

Animals↗
PubMed1992

Nucleotide sequence and genomic structure analyses of the p70 subunit of the human Ku autoantigen: evidence for a family of genes encoding Ku (p70)-related polypeptides.

cDNA encoding the p70 polypeptide subunit of the human Ku autoantigen was isolated. In vitro expression analysis of the cDNA demonstrates that it encodes the entire open reading frame. Nucleotide sequence analysis and comparison to other previously described sequences indicate the existence of several single-nucleotide and amino acid polymorphisms. Southern blot analyses demonstrate the presence of multiple copies of homologous DNA sequences in the human genome. These data support the hypothesis that multiple genes encode a family of Ku(p70)-related polypeptides.

Amino Acid Sequence↗
PubMed1992

Carotid stenosis is a powerful predictor of a positive exercise electrocardiogram in a large hyperlipidemic population.

Hypercholesterolemia is a major risk factor in coronary heart disease (CHD) and ischemic stroke. However, there is no general agreement on the usefulness of systematic screening of patients with hyperlipidemia by stress exercise electrocardiogram (ECG). The feasibility of this approach would depend on selecting patients with a high risk of CHD, since the sensitivity and specificity of the test depends on the prevalence of the disease. In view of the association of CHD and ischemic stroke, we undertook a study to determine whether the presence of atherosclerosis in the carotid arteries was predictive of a positive exercise ECG in a group of 778 asymptomatic patients referred to their hyperlipidemia. We a much higher percentage of positive exercise ECG in patients with carotid atherosclerosis in our ultrasonographic examinations. In a multiple regression analysis which included 13 parameters (age, sex, body mass index, arterial blood pressure, lipid parameters, serum level of glucose, smoking status and the severity of carotid lesions), the strongest predictors of a positive exercise ECG test were age (P = 0.014) and the degree of carotid atherosclerosis (P = 0.010). We therefore conclude that hyperlipidemic patients with atherosclerotic lesions on carotid arteries would benefit most from screening by the exercise ECG.

Adult↗
PubMed1992

Chronic myelomonocytic leukemia with t(13;14) in a child.

Bone marrow cells from a child with chronic myelomonocytic leukemia showed an acquired, non-Robertsonian translocation between chromosomes 13 and 14, t(13;14)(q12.?2;q32.?3). This rearrangement has not previously been reported in childhood myeloproliferative or myelodysplastic disorders.

Child↗
PubMed1992

Developing competency objectives as a basis for planning and assessing health visiting practice in training.

Evaluating student performance in health visiting practice is complex. This paper reports the development of a schedule which combines identification of learning needs, planning of learning experiences, implementation of student activities and the evaluation of student competencies for the fieldwork component of a Health Visitor Diploma. The schedule is intended to encourage students and community practice teachers to develop a shared approach to the planning of learning and the assessment of competence. The approach described may have implications for the planners of post-registration nursing courses who wish to meet the learning needs of students with a variety of professional and academic backgrounds.

Clinical Competence↗
PubMed1992

Accumulation of Cd(II) in the CNS depending on the route of administration: intraperitoneal, intratracheal, or intranasal.

The uptake and subsequent neuronal transport of certain heavy metals in the olfactory mucosa may be a major means by which these compounds gain access to the CNS. To contrast olfactory versus blood-borne routes of exposure, three groups (n = 4) of adult Long-Evans rats were exposed to solutions of radiolabeled CdCl2. Exposure was by one of three routes: unilateral intranasal instillation (IN), intratracheal lavage (IT), or intraperitoneal injection (ip). The dose level for the intranasal route was 30 microliters of 1 microM CdCl2 labeled with 1 microCi 109Cd. For IT and ip, the dose was 30 microliters of 1 microM CdCl2 diluted to 300 microliters in saline and labeled with 1 microCi 109Cd. Rats were euthanized 24 hr after exposure, tissue samples were taken, and radioactivity was counted. Cd levels were low in the olfactory bulbs of rats exposed either intratracheally or intraperitoneally. However, in rats intranasally exposed, Cd levels were nearly 40 x higher in olfactory bulbs ipsilateral to the exposed side than in those on the contralateral side. With all routes of exposure, Cd levels in brain samples were only slightly elevated. These results suggest that for certain airborne toxicants, especially those that are excluded from the CNS by the blood-brain barrier, the olfactory system may provide a direct route of entry into the CNS.

Administration, Intranasal↗
PubMed1992

Patients' choices and perceptions after an invitation to participate in treatment decisions.

Previous search indicates that treatment outcomes may be improved if patients perceive greater control over their treatment, but the practical implications of encouraging patients to take more control have not been investigated. The present study investigated responses of 143 patients in a cardiovascular risk management clinic to an invitation to make a decision about their treatment. Subjects' choices of the target behaviour for their behaviour-change treatment were highly predictable from their state of health, reasons for coming to the clinic, what behaviours they were told they were at risk from, and contacts with health workers. The degree of control that subjects reported they had over the decision varied considerably, being negatively related to blood pressure and positively related to the degree of control that subjects believed they had over their health in general. Issues such as time-demands, the practitioner's job satisfaction, and ethical implications of patient participation are discussed.

Adolescent↗
PubMed1992

The prediction of human tumor radiosensitivity in situ: an approach using chromosome aberrations detected by fluorescence in situ hybridization.

No method of predicting the radiation sensitivity of individual human tumors is presently available, and recently published data show that other factors, in addition to the intrinsic radiosensitivity of the tumor cells, may play a role in the in vivo response of human tumors. Since these factors likely involve the tumor milieu (e.g., cell-cell contact and tumor hypoxia), an in situ assay of radiosensitivity is required. Although an analysis based on chromosome damage is the only suitable assay that would fit the requirements of sensitivity and speed of analysis, conventional examination of chromosome damage is impractical. By allowing the visualization of chromosomes in interphase cells, the technique of premature chromosome condensation (PCC) overcomes the need to culture the tumor cells in vitro, but the technical problem remains of counting a small excess number of breaks over the often large pretreatment chromosome number. We demonstrate here that the combination of fluorescence in situ hybridization (FISH) with PCC enormously simplifies the problem by focusing the analysis on a single chromosome. It also allows exchange aberrations to be scored easily. We demonstrate that the FISH technology may also be used to estimate radiation sensitivity from stable reciprocal translocations in metaphase identified by combining whole chromosome painting with a second color hybridization to the repeat sequences common to the centromeres. Since the frequency of stable translocations should correlate with initial chromosome damage, and since these translocations are not preferentially lost from the irradiated tumor cell population by cell death, an estimate of tumor cell killing following 1-5 dose fractions should be possible. Each of these two methods has its advantages, and a careful study of the two should establish which is superior for routine use to determine tumor radiosensitivity in situ.

Chromosome Aberrations↗
PubMed1992

Autobiographical memory and problem-solving strategies of parasuicide patients.

Recent research has noted the tendency of parasuicide patients to retrieve over-general autobiographical memories. Separate studies suggest problem-solving deficits within this group. The present study was concerned first with replicating these findings and, secondly, with developing a model of the relationship between over-general memory recall and poor problem-solving abilities in parasuicide patients. Anger and hopelessness were measured as markers for mood. In line with the hypotheses, the parasuicide group (N = 12) produced significantly over-general memories in contrast to a matched control group (N = 12). This occurred significantly in relation to positive cues, and latency to first responses was significantly delayed in the parasuicide group. The parasuicide group also provided fewer and less-effective problem-solving strategies than the control group, and a significant association was found between low effectiveness of problem-solving strategies and over-general memory recall in the parasuicide group. Anger and hopelessness levels were significantly higher within the parasuicide group in line with previous findings. The clinical implications of these findings are discussed.

Adaptation, Psychological↗
PubMed1992

Problems measuring contrast sensitivity in children.

A preliminary study measured the contrast sensitivity function (CSF) in 30 children (aged 3 months-5 years). Preferential looking techniques were used to assess CSF to sine wave gratings displayed on one of two screens. To find a meaningful contrast sensitivity procedure we compared the results with a shorter procedure using an edge stimulus. The following problems were encountered: measuring the contrasts required to detect four or five different spatial frequencies took time, resulting in boredom and loss of attention in our subjects; there was poor correlation between CSF and edge detection; an interesting artefact resulted in a plateau rather than a low frequency fall-off in the CSF of five of the children greater than 30 months old. This artefact may have resulted from peripheral rather than central retinal responses and/or motion artefacts in the stimulus onset. A follow up study with 41 additional children aged 3-36 months limited the contrast testing to that of the spatial frequency corresponding to the peak of the CSF. The shortened procedure, plus a lot of encouragement, resulted in higher contrast sensitivities in all but the oldest age group and successful monocular contrast measurements. In order to avoid artefacts arising from peripheral vision, children were encouraged to look at each screen before responding.

Child, Preschool↗
PubMed1992

Pituitary oxytocin and vasopressin content of rats flown on COSMOS 2044.

Preliminary studies in rats (COSMOS 1887) suggested that levels of posterior pituitary hormones were reduced by exposure to spaceflight. To confirm these preliminary findings, we obtained pituitary tissue from rats flown for 14 days on COSMOS 2044. Posterior pituitary content of oxytocin (OT) and vasopressin (VP) were measured in these tissues as well as those from ground-based controls. The synchronous control group had feeding and lighting schedules synchronized to those in the spacecraft and were maintained in flight-type cages. Another group was housed in vivarium cages; a third group was tail suspended (T), a method used to stimulate microgravity. Flight rats showed an average reduction of 27% (P less than 0.05) in pituitary OT and VP compared with the three control groups. When hormone content was expressed in terms of pituitary protein (micrograms hormone/mg protein), the average decrease in OT and VP for the flight animals ranged from 20 to 33% (P less than 0.05) compared with the various control groups. Reduced levels of pituitary OT and VP were similar to preliminary measurements from the COSMOS 1887 mission and appear to result from exposure to spaceflight. These data suggest that changes in the rate of hormone secretion or synthesis may have occurred during exposure to microgravity.

Animals↗
PubMed1992

Myocardial viability in patients with Q wave myocardial infarction and no residual ischemia.

BACKGROUND: Coronary revascularization in patients with persistent angina after myocardial infarction reduces the incidence of recurrent angina pectoris and myocardial infarction and improves left ventricular function. The results of revascularization after a Q wave myocardial infarction when there is no residual ischemia may depend on myocardial viability. METHODS AND RESULTS: To determine whether there was viable myocardium in the infarct area in the absence of clinical and scintigraphic evidence of myocardial ischemia, 15 asymptomatic patients with a Q wave myocardial infarction, no redistribution on stress 201Tl test, and single-vessel disease (greater than 70% stenosis) with persistent anterograde blood flow were randomized to percutaneous transluminal coronary artery angioplasty (PTCA) or conservative medical treatment. After 2 months of follow-up, mean coronary blood flow measured by Doppler catheter in the infarct-related artery was higher in the PTCA treatment group (33 +/- 6 ml/min, n = 8) than in the conservative treatment group (16 +/- 4 ml/min, n = 7; p less than 0.05 between groups). The 201Tl pathological-to-normal ratios measured on postexercise images did not change in patients treated conservatively during the follow-up period (delta = +1.1 +/- 2.2%; NS from baseline) but increased significantly in patients treated by PTCA (delta = +8.5 +/- 2.3%; p less than 0.01 from baseline; p less than 0.05 between groups). Segmental wall motion improved on left ventricular angiography 2 months after PTCA (delta = +11.5 +/- 2.2%; p less than 0.001 from baseline) significantly more than in the conservative treatment group (delta = +4.1 +/- 1.4%; p less than 0.05 between both groups). Improvements of 201Tl ratios and segmental wall motion indexes correlated significantly (r = 0.73, p = 0.002). The mild improvement of global left ventricular ejection fraction measured in the PTCA treatment group did not differ significantly from changes in the conservative treatment group. CONCLUSIONS: Successful angioplasty of the stenotic infarct artery in patients with a Q wave myocardial infarction and no residual ischemia improved coronary flow, 201Tl uptake in the infarct area, and regional wall motion. Therefore, myocardial viability may last several weeks, as long as residual blood flow persists in the infarct-related artery. Optimal assessment of viability by imaging techniques should identify patients who are most likely to benefit from revascularization.

Angioplasty, Balloon, Coronary↗