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Biomedical subjects

A Day

Publications and source records attributed to A Day.

At least 55 records · Page 3Linked to original sources
PubMed1998

Ethanol, stroke, brain damage, and excitotoxicity.

The N-methyl-d-aspartate (NMDA)-glutamate receptor could contribute to stroke, trauma, and alcohol-induced brain damage through activation of nitric oxide formation and excitotoxicity. In rat primary cortical cultures NMDA was more potent at activating nitric oxide formation than triggering excitotoxicity. Ethanol dose dependently inhibited both responses. In contrast, treatment of neuronal cultures with ethanol (100 mM) for 4 days significantly increased NMDA stimulated nitric oxide formation and excitotoxicity. These findings suggest that ethanol acutely inhibits but chronically causes supersensitivity to NMDA-induced excitotoxicity in neuronal cultures. To investigate ethanol's interaction with stroke induced damage models of global cerebral ischemia were studied. Transient global ischemia resulted in a loss of hippocampal CA1 pyramidal neurons over a 3- to 5-day period. Determinations of the NMDA receptor ligand binding stoichiometry or postischemic receptor binding changes did not show differences between neurons that undergo delayed neuronal death following ischemia and those that show no toxicity, for example, CA1 and dentate gyrus, respectively. Acute ethanol (3 g/kg) was found to protect against ischemia-induced CA1 hippocampal damage by lowering body temperature, but not under temperature controled conditions. These studies indicate that the factors contributing to stroke-induced brain damage are complex, although they are consistent with chronic ethanol increasing stroke-induced brain damage by increasing NMDA excitotoxicity.

Animals↗
PubMed1998

Stable albinism induced without mutagenesis: a model for ribosome-free plastid inheritance.

Maternally inherited chlorophyll deficiency, or albinism, is a standard marker in plant cytoplasmic genetics. Its stability is consistent with mutations in the plastid genome. Nuclear mutations inducing plastid ribosome deficiency (PRD) also lead to maternally inherited chlorophyll deficiency. Here we report that stable chlorophyll deficiency can be efficiently generated in cruciferous plants without mutagenesis by a short exposure to spectinomycin, an inhibitor of plastid protein synthesis. We show that the chlorophyll-deficient phenotype results from a deficiency in plastid ribosomes and plastid translation products. Loss of plastid ribosomes is irreversible. The data suggest that mutations are not essential for generating inheritable PRD. It allows the formulation of a more general model in which stable PRD can be induced by a variety of factors that prevent the formation of functional plastid ribosomes. A non-mutational mechanisms for generating inheritable chlorophyll deficiency has implications for the origin and inheritance of green-white variegation in nature.

Arabidopsis↗
PubMed1998

Presence: creating order out of chaos.

Surgery can be experienced as a time that throws the many dimensions of a person into a state of chaos. This article provides insight to the responses to chaos and describes ways in which to offer the quality of Presence as the essence of holistic care.

Holistic Nursing↗
PubMed1997

The psychological effects of laparoscopy on women with chronic pelvic pain.

BACKGROUND: Many women who undergo diagnostic laparoscopy for chronic pelvic pain do not have pelvic pathology. This has led to an interest in psychological factors that might contribute to their experience of pain. This study was designed to evaluate the effects of diagnostic laparoscopy on women with chronic pelvic pain and to explore possible psychological mechanisms. METHODS: Seventy-one women undergoing laparoscopy for chronic pelvic pain were randomly allocated to one of two groups waiting different lengths of time for laparoscopy. Women were interviewed before laparoscopy and were followed up 1 week, 3 months and 6 months afterwards. Pain was assessed with an interview measure, diaries and visual analogue scales. RESULTS: Pain reductions were observed from before to after diagnostic laparoscopy. Regression analysis was used to identify factors which predicted improvements in pain. The hypothesis that psychological factors would predict improvements in pain was confirmed. Pain improvements after laparoscopy were predicted by beliefs about pain and the change in each woman's evaluation of the seriousness of her condition. Other than baseline pain, these psychological variables were the only ones to emerge as predictors of pain change despite exploratory analysis of over 40 other variables. CONCLUSIONS: Diagnostic laparoscopy can have beneficial effects in women with chronic pelvic pain. These effects appear to be the result of psychological mechanisms. Further investigation of these mechanisms could help in the understanding and treatment of women with chronic pelvic pain.

Adolescent↗
PubMed1996

Hyperhomocysteinaemia is a risk factor for vein graft stenosis.

OBJECTIVES: Many infrainguinal vein graft failures are due to progressive vein graft stenosis (VGS) from intimal hyperplasia. Systemic factors have been implicated in the aetiology of intimal hyperplasia. Hyperhomocysteinaemia (HHCA) is established as an independent risk factor for coronary and peripheral arterial disease. The objective of this study was to examine the influence of HHCA and other serological factors upon the development of VGS. STUDY DESIGN: Thirty-eight patients who had undergone infrainguinal vein bypass were recruited to a case/control study from a graft surveillance program. Nineteen patients with documented VGS were matched against controls without stenosis for age, sex, length of time from surgery, diabetes, smoking history and preoperative symptom score. All patients were recalled for Duplex ultrasound scans, venesection and carbon monoxide estimation which were performed in a blinded fashion. RESULTS: Statistical analysis of all parameters revealed that plasma homocysteine was significantly elevated in patients with VGS (p < 0.3, Wilcoxon rank sum). CONCLUSIONS: These results suggest that HHCA is a previously unidentified risk factor for VGS. Patients with HHCA are susceptible to VGS and preoperative investigation would allow identification of patients at risk.

Adult↗
PubMed1996

Homocysteine: an independent risk factor for the failure of vascular intervention.

Hyperhomocysteinaemia is an independent risk factor for the early development of arterial disease. Homocysteine and cardiovascular risk factors were assessed in 41 young and 25 older patients with vascular disease. As homocysteine may act by the generation of free radicals, total antioxidant capacity was measured. Hyperhomocysteinaemia was found in 29 per cent of patients but there was no difference between young and older patients. Homocysteine level was unrelated to other cardiovascular risk factors. Young age, diabetes and hyperhomocysteinaemia were independent risk factors for the failure of vascular procedures (P = 0.006). Patients with hyperhomocysteinaemia had raised total antioxidant capacity. The potential of identifying and treating a subgroup of patients with a poor prognosis deserves further study.

Adult↗
PubMed1995

Evidence for a role of pituitary ATP receptors in the regulation of pituitary function.

Despite a rapidly increasing acceptance for a role of ATP as an extracellular mediator in several biological systems, the present report shows that ATP may mediate physiological responses in pituitary cells. We have now been able to demonstrate a specific action of ATP receptors to mediate the release of luteinizing hormone from gonadotropes and have coupled them with further studies that clearly show that ATP can be exocytotically released from cultured rat pituitary cells. Both ATP and UTP (100 microM) caused a > 14-fold increase in the rate of luteinizing hormone release from superfused cells. Adenosine 5'-[alpha, beta-methylene]triphosphate and 5'-[beta,gamma-methylene triphosphate were ineffective, and 2-methylthio-ATP had only a modest stimulatory effect. Homologous and heterologous desensitization occurred with UTP and ATP, and these did not have additive effects. Thus, nucleotides can be effective stimulators of luteinizing hormone release through a single class of ATP receptor (P2U subtype). The calcium ionophore A23187 provoked release of a substantial amount of ATP from pituitary cells in a concentration- and Ca(2+)-dependent manner, which was desensitized by pretreatment with A23187. This implies a possible paracrine and/or autocrine mechanism by which nucleotides may exert their effects on pituitary cells. In conclusion, we have provided strong evidence for a novel role of extracellular nucleotides as mediators in pituitary--in particular, in gonadotrope--function.

Adenosine Triphosphate↗
PubMed1995

Guidelines for carotid endarterectomy. A multidisciplinary consensus statement from the Ad Hoc Committee, American Heart Association.

BACKGROUND AND PURPOSE: Indications for carotid endarterectomy have engendered considerable debate among experts and have resulted in publication of retrospective reviews, natural history studies, audits of community practice, position papers, expert opinion statements, and finally prospective randomized trials. The American Heart Association assembled a group of experts in a multidisciplinary consensus conference to develop this statement. METHODS: A conference was held July 16-18, 1993, in Park City, Utah, that included recognized experts in neurology, neurosurgery, vascular surgery, and healthcare planning. A program of critical topics was developed, and each expert presented a talk and provided the chairman with a summary statement. From these summary statements a document was developed and edited onsite to achieve consensus before final revision. RESULTS: The first section of this document reviews the natural history, methods of patient evaluation, options for medical management, results of surgical management, data from position statements, and results to date of prospective randomized trials for symptomatic and asymptomatic patients with carotid artery disease. The second section divides 96 potential indications for carotid endarterectomy, based on surgical risk, into four categories: (1) Proven: This is the strongest indication for carotid endarterectomy; data are supported by results of prospective contemporary randomized trials. (2) Acceptable but not proven: a good indication for operation; supported by promising but not scientifically certain data. (3) Uncertain: Data are insufficient to define the risk/benefit ratio. (4) Proven inappropriate: Current data are adequate to show that the risk of surgery outweighs any benefit. CONCLUSIONS: Indications for carotid endarterectomy in symptomatic good-risk patients with a surgeon whose surgical morbidity and mortality rate is less than 6% are as follows. (1) Proven: one or more TIAs in the past 6 months and carotid stenosis > or = 70% or mild stroke within 6 months and a carotid stenosis > or = 70%; (2) acceptable but not proven: TIAs within the past 6 months and a stenosis 50% to 69%, progressive stroke and a stenosis > or = 70%, mild or moderate stroke in the past 6 months and a stenosis 50% to 69%, or carotid endarterectomy ipsilateral to TIAs and a stenosis > or = 70% combined with required coronary artery bypass grafting; (3) uncertain: TIAs with a stenosis < 50%, mild stroke and stenosis < 50%, TIAs with a stenosis < 70% combined with coronary artery bypass grafting, or symptomatic, acute carotid thrombosis; (4) proven inappropriate: moderate stroke with stenosis < 50%, not on aspirin; single TIA, < 50% stenosis, not on aspirin; high-risk patient with multiple TIAs, not on aspirin, stenosis < 50%; high-risk patient, mild or moderate stroke, stenosis < 50%, not on aspirin; global ischemic symptoms with stenosis < 50%; acute dissection, asymptomatic on heparin. Indications for carotid endarterectomy in asymptomatic good-risk patients performed by a surgeon whose surgical morbidity and mortality rate is less than 3% are as follows. (1) Proven: none. As this statement went to press, the National Institute of Neurological Disorders and Stroke issued a clinical advisory stating that the Institute has halted the Asymptomatic Carotid Atherosclerosis Study (ACAS) because of a clear benefit in favor of surgery for patients with carotid stenosis > or = 60% as measured by diameter reduction. When the ACAS report is published, this indication will be recategorized as proven. (2) acceptable but not proven: stenosis > 75% by linear diameter; (3) uncertain: stenosis > 75% in a high-risk patient/surgeon (surgical morbidity and mortality rate > 3%), combined carotid/coronary operations, or ulcerative lesions without hemodynamically significant stenosis; (4) proven inappropriate: operations with a combined stroke morbidity and mortality > 5%.

Arterial Occlusive Diseases↗
PubMed1995

A transposon-like sequence with short terminal inverted repeats in the nuclear genome of Chlamydomonas reinhardtii.

A 1.2 kb DNA sequence, flanked by a potential seven base target-site duplication, was found inserted into a TOC1 transposable element from Chlamydomonas reinhardtii. The insertion sequence, named TOC2, is a member of a family of repeated DNA sequences that is present in all the C. reinhardtii strains tested. It resembles class II transposable elements: it possesses short 14 bp imperfect terminal repeats that begin AGGAGGGT, and sub-terminal direct repeats located within 250 bp of the termini. No large open reading frames were found. The terminal bases and length of target-site duplication are important in classifying transposable elements. On this basis TOC2 does not fall readily into existing families of class II transposable elements found in plants.

Animals↗
PubMed1995

Isolation of a Chlamydomonas reinhardtii telomere by functional complementation in yeast.

We attempted to determine whether Chlamydomonas reinhardtii telomeres, which do not form G-quartet structures readily in vitro, are able to nucleate telomere addition in Saccharomyces cerevisiae. Restricted C. reinhardtii genomic DNA was ligated to a linear S. cerevisiae vector lacking a telomere. A C. reinhardtii telomere ligated to this unprotected end allowed vector replication as a linear DNA molecule in S. cerevisiae. DNA sequencing revealed common [T4AG3]n and variant T6AG3 and T5AG3 C. reinhardtii telomere repeats capped by S. cerevisiae telomere repeat units. The recognition of a C. reinhardtii telomere by the telomere maintenance machinery of S. cerevisiae is consistent with a common theme for telomere structure in organisms with divergent telomere repeats.

Animals↗
PubMed1995

Hysterectomy and psychiatric disorder: are the levels of psychiatric morbidity falling?

This paper compares the findings of three studies carried out at intervals over the years 1975-1990. The three studies were concerned with different issues, but each study examined psychiatric morbidity among women undergoing hysterectomy for menorrhagia of benign origin. In all three studies levels of psychiatric morbidity were measured before the operation and 6 months after the operation. Psychiatric morbidity was measured with the Present State Examination (PSE) (Wing et al. 1974), and with established self-report questionnaires. Levels of psychiatric morbidity fell significantly across the three studies. In Study 1, the proportions of psychiatric cases were 58% before hysterectomy and 26% after; in Study 2, 28% before and 7% after; and in Study 3, 9% before and 4% after. The decline in psychiatric morbidity was not associated with demographic and social characteristics, previous psychiatric history, family psychiatric history, the nature of the women's menstrual complaints, or the women's understanding and expectations of the operation. In Study 3 anti-menorrhagic drugs were prescribed twice as frequently as in the two previous studies; while the prescribing of psychotropic medication was significantly higher in Study 1 than in Study 2 or Study 3. The implications of these findings are discussed.

Adaptation, Psychological↗
PubMed1995

Emotional reactions in women attending a UK colposcopy clinic.

STUDY OBJECTIVE: To assess the emotional responses of women attending a colposcopy clinic for investigation of an abnormal cervical smear, and to elicit the women's views on the screening service and colposcopy clinic. DESIGN: Over 12 months all new attenders at a colposcopy clinic were invited to join the study. They were assessed psychiatrically four weeks before their first clinic appointment, and four weeks and 32 weeks after their first clinic appointment. SETTING: Colposcopy clinic, John Radcliffe Hospital, Oxford. PATIENTS: Of 114 women attending the colposcopy clinic for investigation of an abnormal cervical smear, 102 agreed to enter the study. MEASUREMENTS: Psychiatric symptoms were assessed with a standardised psychiatric interview, the present state examination; and with four self rated mood scales:--the general health questionnaire, the Beck depression inventory, the Leeds depression scale, and the Leeds anxiety scale. MAIN RESULTS: On all these measures, in the whole patient group, psychiatric morbidity was found to be transient and relatively minor. Thus ratings on the present state examination were not significantly higher than the rate found in a community sample of 520 women in Oxford, while on the four self rated mood scales, mean total scores were lower than the cut off value used to distinguished cases. Patient satisfaction with the colposcopy services was generally high but there was some dissatisfaction with delays. CONCLUSIONS: After an abnormal cervical smear, further investigation by colposcopy is generally associated with low levels of anxiety and depression.

Adolescent↗