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Biomedical subjects

A Harris

Publications and source records attributed to A Harris.

At least 253 records · Page 14Linked to original sources
PubMed1996

Presentation format in analogue studies: effects on participants' evaluation.

Whether presentation format (video, audio, written transcript, or written transcript with photograph) affects participants' responses to counseling scenarios in an analogue study was examined. After watching a brief counseling session presented in one of four formats, 131 participants completed three instruments measuring counselor credibility and expectations. Results revealed significant differences among the formats on teh COunselor Rating Form (CRF-S; Corrigan & Schmidt, 1983) Trustworthiness and Expertness Scales, with transcripts with pictures rated the highest (higher than videotape and audiotape) and transcripts without pictures rated second highest (higher than video). No significant differences between the presentation formats were revealed on the Expectations about Counseling Questionnaire (EAC; Tinsley, Workman, & Kass, 1980) or 15 Personal Problem Inventory (15PPI; Cash, Begley, McCown, & Weise, 1975). Results suggest that studies using differing formats with the CRF-S are not necessarily comparable and that the four types of analogue approaches may not be interchangeable.

Adult↗
PubMed1996

Rapid assays for environmental and biological monitoring.

Rapid, inexpensive, sensitive, and selective enzyme-linked immunosorbent assays (ELISAs) now are utilized in environmental science. In this laboratory, many ELISAs have been developed for pesticides and other toxic substances and also for their metabolites. Compounds for which ELISAs have recently been devised include insecticides (organophosphates, carbaryl, pyrethroids, and fenoxycarb), herbicides (s-triazines, arylureas, triclopyr, and bromacil), fungicides (myclobutanil), TCDD, and metabolites of naphthalene and toluene. New rapid assays have been developed for mercury.

Antifungal Agents↗
PubMed1996

Aggregate/community-centered undergraduate community health nursing clinical experience.

Debate continues about the appropriateness of clinical experiences targeting aggregates in undergraduate community health nursing education. This paper describes a practical model to teach, through experience, the concepts of aggregate/community-centered practice at the baccalaureate level. As a voluntary alternative to the usual community assessment paper, groups of students worked in partnership with community groups to define health needs and to address one need. Sequential student groups focused the assessment and implemented a plan. The required time for each project varied. One project is described to illustrate the model. While independent community-centered practice is not expected of the B.S.N. graduate, the model described here develops comprehension of the concepts and process of such practice.

Clinical Competence↗
PubMed1996

Effects of topical dorzolamide on retinal and retrobulbar hemodynamics.

PURPOSE: Topical carbonic anhydrase inhibitors such as dorzolamide have been developed as ocular hypotensive agents devoid of the side effects plaguing their systemic predecessors. We evaluated the influence of dorzolamide on retinal and retrobulbar blood flow markers to determine if the drug has orbital vascular as well as ocular hypotensive effects. METHODS: Eleven persons with healthy eyes received either placebo or two drops 2% dorzolamide, 2 h prior to studies conducted in double-masked, counterbalanced fashion. Four retrobulbar vessels (nasal and temporal posterior ciliary, central retinal, and ophthalmic arteries) were analyzed by color Doppler imaging; scanning laser ophthalmoscopy was used to examined retinal and superficial optic nerve head blood linear velocity. RESULTS: Dorzolamide lowered IOP from 15.7 +/- 0.7 to 13.7 +/- 0.7 mmHg (p < 0.05). The drug also hastened retinal arteriovenous passage of fluorescein dye, and accelerated capillary dye transit in the macula and optic nerve head. The drug, however, left unaltered blood velocity or resistance index in any retrobulbar vessel. CONCLUSIONS: Dorzolamide is an effective ocular hypotensive agent that accelerates blood velocity in the retinal and superficial optic nerve head without an apparent effect upon retrobulbar hemodynamics.

Administration, Topical↗
PubMed1996

Acute IOP elevation with scleral suction: effects on retrobulbar haemodynamics.

AIMS/BACKGROUND: Mechanical and vascular factors may both contribute to glaucoma. This study investigated the relation of mechanical to vascular factors by examining how acute IOP elevation altered flow velocities in the central retinal and ophthalmic arteries. METHODS: IOP was elevated from a baseline near 14 to approximately 45 mm Hg using suction ophthalmodynamometry. During recovery from scleral suction, IOP fell to near 8 mm Hg. At each IOP, peak systolic and end diastolic velocities (PSV and EDV) were measured in the central retinal and ophthalmic arteries using colour Doppler imaging (Siemens Quantum 2000). Eleven healthy people served as subjects. RESULTS: Acute elevation in IOP had no effect upon PSV, EDV, or the derived resistance index in the ophthalmic artery: flow velocities in this vessel were identical at IOP of 8 mm Hg or 45 mm Hg. In contrast, in the central retinal artery, PSV and EDV fell, and the resistance index rose, in steady progression as IOP was acutely elevated (each p < 0.01). At IOP of 45 mm Hg, EDV was virtually absent and the resistance index was very nearly 1.0. CONCLUSION: Ophthalmic arterial haemodynamics are unrelated to acute fluctuations of the IOP over a wide range, suggesting that ocular hypertension itself cannot induce vascular dysfunction in this artery. In contrast, flow velocities in the central retinal artery were highly IOP dependent, implying that haemodynamic and mechanical factors are closely linked in this vascular bed.

Acute Disease↗
PubMed1996

Hyperoxia improves contrast sensitivity in early diabetic retinopathy.

AIM: The cause of vascular and visual pathology in diabetic retinopathy remains unknown. If retinal hypoxia plays a role, then early in the course of diabetes 100% oxygen breathing should normalise both contrast sensitivity and retinal blood flow. METHODS: This hypothesis was tested in 12 diabetic patients with minimal retinopathy who, none the less, exhibited reduced contrast sensitivity (p = 0.003 versus 12 age and sex-matched controls) and prolonged retinal arteriovenous dye transit (p = 0.0001 versus controls). RESULTS: Isocapnic hyperoxia failed to alter contrast sensitivity in controls, while it significantly improved contrast sensitivity in patients (at 12 cpd; p = 0.042) to levels indistinguishable from normal. Individual improvement in contrast sensitivity correlated positively with the severity of the initial defect (r = +0.84, p = 0.0008). Hyperoxia also had haemodynamic effects; it slowed retinal arteriovenous passage of fluorescein dye in controls, but did not further slow this transit time in patients. CONCLUSIONS: These results demonstrate the reversibility of early contrast sensitivity deficits in diabetes mellitus, and support the hypothesis that factors linked to tissue hypoxia initiate both visual and vascular dysfunction in diabetic retinopathy.

Adult↗
PubMed1996

Retinal blood flow indices in patients infected with human immunodeficiency virus.

AIMS/BACKGROUND: Abnormal blood flow dynamics are believed to contribute to the development of retinal microvascular disease in patients infected with human immunodeficiency virus (HIV). In this study, the scanning laser ophthalmoscope (SLO) was used, combined with fluorescein angiography, to measure retinal blood flow indices in HIV seropositive patients. METHODS: Arteriovenous passage time (AVP) and perifoveal capillary blood flow velocity (CFV) were measured in 23 HIV infected patients and 23 control subjects with SLO fluorescein angiography. RESULTS: No significant difference in AVP was found between the two groups. However, CFV was significantly reduced in HIV infected patients (p = 0.013). CONCLUSION: Patients infected with HIV show abnormal haemodynamics at the level of the perifoveal capillaries.

Adult↗
PubMed1996

Research ethics committee audit: differences between committees.

The same research proposal was submitted to 24 district health authority (DHA) research ethics committees in different parts of the country. The objective was to obtain permission for a multi-centre research project. The study of neonatal care in different types of unit (regional, subregional and district), required that four health authorities were approached in each of six widely separated health regions in England. Data were collected and compared concerning aspects of processing, including application forms, information required, timing and decision-making. The key finding was that ethics committees received and processed the applications variably, reflecting individual factors and local problems. To improve consensus and facilitate multicentre studies, standard forms and instructions are suggested and the establishment of a national committee or advisory group advocated.

Clinical Trials as Topic↗
PubMed1996

An ovine CFTR variant as a putative cystic fibrosis causing mutation.

This report describes a DNA variant in the ovine cystic fibrosis transmembrane conductance regulator (CFTR) gene that has been previously reported as a putative cystic fibrosis causing mutation in humans. The variant is a guanine to adenine base change at position 1019 of the ovine CFTR cDNA, corresponding to an arginine (R) to glutamine (Q) amino acid substitution at position 297 in the predicted CFTR polypeptide. The equivalent R297Q mutation in exon 7 of the human CFTR gene has been reported in a CF patient. This is the first putative cystic fibrosis mutation to be detected in another animal species.

Animals↗
PubMed1996

Hematopoietic bone marrow hyperplasia: correlation of spinal MR findings, hematologic parameters, and bone mineral density in endurance athletes.

PURPOSE: To determine the frequency of hematopoietic hyperplasia on spinal magnetic resonance (MR) images in endurance athletes and to correlate MR alterations with clinical parameters. MATERIALS AND METHODS: In 15 endurance athletes, MR images of the lumbar spine were analyzed for hematopoietic hyperplasia; vertebral T1 and T2 were determined. Bone mineral density (BMD) was determined, blood tests were performed, and maximum oxygen consumption (VO2max) was measured. RESULTS: Nine subjects showed evidence of hematopoietic hyperplasia: Eight showed T1 prolongation, and six had patchy or diffuse T1 hypointensity. No definite correlation existed between hematopoietic hyperplasia and duration of training, hematologic results, or VO2max levels. Borderline significance existed between hematopoietic hyperplasia and anemia (P = .103) and intensity of training (P = .09). BMD had no statistically significant effect on T1. CONCLUSION: Changes in BMD do not appear to contribute to MR marrow changes that are consistent with hematopoietic hyperplasia. Depleted iron reserves or increased hematopoiesis probably contribute to hematopoietic hyperplasia in endurance athletes.

Adult↗
PubMed1996

Ocular hemodynamic effects of acute ethanol ingestion.

PURPOSE: Because the protean biological effects of ethanol include acute alterations in both cortical function and circulatory control, we investigated the effect of acute alcohol consumption on retrobulbar hemodynamics and contrast sensitivity in healthy human volunteers. SUBJECTS AND METHODS: Twelve young adults received orange juice with and without ethanol in a double-masked fashion. The ethanol dose was sufficient to raise blood alcohol to 0.07 +/- 0.003 g/dl. Retrobulbar hemodynamics were assessed at baseline and twice at elevated blood alcohol by color Doppler imaging. RESULTS: Acute elevation of blood alcohol lowered intraocular pressure from 13.0 +/- 0.7 to 10.7 +/- 0.7 mm Hg (p < 0.05). In contrast, elevated blood alcohol left peak systolic velocity, end-diastolic velocity and the resistance index constant in three retrobulbar arteries (ophthalmic, central retinal and posterior ciliary). For example, in the central retinal artery, peak systolic velocity, end-diastolic velocity and the resistance index averaged 11.0 +/- 1.3 cm/s, 2.8 +/- 0.4 cm/s and 0.75 +/- 0.03 before ethanol, as compared with 10.5 +/- 1.0 cm/s, 2.9 +/- 0.3 cm/s and 0.72 +/- 0.03 after ethanol (all p = NS). Alcohol ingestion also failed to alter either visual acuity or contrast sensitivity, as assessed under both photopic and mesopic conditions. CONCLUSIONS: Although ethanol has widespread cognitive and cardiovascular effects, at blood levels near legal definitions of intoxication we found it ineffective in altering either retrobulbar hemodynamics or contrast sensitivity.

Adult↗
PubMed1996

Retinal hemodynamics during increased intraocular pressure.

The pathogenesis of primary chronic open-angle glaucoma (POAG) remains uncertain. It has been proposed that some of these patients may present with a deficiency in retinal hemodynamic autoregulation. It is also thought that visual field loss in POAG could be related to poor retinal perfusion. The present study was undertaken to evaluate the capacity of retinal autoregulation to maintain constant retinal circulation despite an acute rise in intraocular pressure (IOP). A total of 22 healthy subjects were recruited to this study. Retinal hemodynamics were assessed by digital video fluorescein angiograms using a scanning laser ophthalmoscope at normal (13.8 +/- 1.5 mmHg) and increased IOP (33.8 +/- 3.4 mmHg). Suction cups were used for raising the IOPs. The angiograms were performed at baseline and after 1 min of increased IOP. To quantify retinal hemodynamics the arm-retina time (ART) and arteriovenous passage time (AVP) were evaluated. The ART increased significantly from 9.4 +/- 1.8 to 11.8 +/- 2.2 s (P < 0.05) during elevated IOP, and the AVP was significantly prolonged from 1.6 +/- 0.4 to 3.0 +/- 0.8 s (P < 0.01) with IOP elevation as well. The increase in ART and AVP indicates an insufficiency of retinal autoregulation after an acute rise in IOP, even in healthy subjects. It appears that IOP values of > or = 30 mmHg may be detrimental to retinal perfusion in normals as well as in patients with POAG, who may have compromised retinal perfusion to begin with.

Adult↗
PubMed1996

Acetazolamide and CO2: acute effects on cerebral and retrobulbar hemodynamics.

PURPOSE: Acetazolamide and CO2 are cerebral vasodilators whose specific effects in various brain regions have not been carefully defined. We investigated the effects of these agents in both larger cerebral and smaller, retrobulbar arteries, to compare their general cerebral vasodilatory influence with their specific ocular vascular effects. METHODS: Twelve young adults with healthy eyes were studied under normocapnic and hypercapnic (6% CO2, 94% O2 tanked gas) conditions after receiving either placebo or 1,000 mg acetazolamide (3 h before study). Color Doppler imaging was used to measure peak systolic and end-diastolic velocities (PSV and EDV) in the internal carotid, middle cerebral, ophthalmic, and central retinal arteries under each condition. RESULTS: Acetazolamide and CO2 each lowered intraocular pressure; combining the agents provided no additive ocular hypotensive effect. Hypercapnia or acetazolamide per se failed to alter PSV, EDV, or the derived resistance index [RI; (PSV-EDV)/PSV] in the internal carotid or in either orbital artery. However, when hypercapnia was superimposed upon acetazolamide, the resistance index fell in the internal carotid and central retinal arteries (each p < 0.05). In contrast, the middle cerebral artery was responsive to either vasodilator and to their combination: PSV and EDV rose, and RI fell with each experimental treatment. CONCLUSIONS: In the brain, the middle cerebral artery exhibits substantial dependence of flow velocity on the vasodilators CO2 and acetazolamide. In contrast, the ophthalmic and central retinal arteries appear less responsive. Nonetheless, the combination of carbonic anhydrase inhibition (acetazolamide) with CO2 augmentation did lower vascular resistance distal to the central retinal artery, suggesting that this mechanism vasodilates critical ocular tissues.

Acetazolamide↗
PubMed1996

Laser Doppler flowmetry measurement of changes in human optic nerve head blood flow in response to blood gas perturbations.

PURPOSE: The objective of this study was to establish the ability of laser Doppler flowmetry to detect relative changes in human optic nerve head hemodynamics caused by physiologic blood gas perturbations. METHODS: Laser Doppler flowmetry permits the noninvasive assessment of relative blood velocity, volume, and flow (flux) in a sample volume of the nerve head. Such measurements were performed in two groups of healthy subjects. The first group (n = 11) was tested during normal room air breathing and then while breathing 100% oxygen (isocapnic hyperoxia). The second group (n = 10) was also tested under normal conditions as well as during isoxic hypercapnia (+ 15% end-tidal carbon dioxide). Results were analyzed by paired t tests. RESULTS: Hyperoxia created a significant 25% (p = 0.002) decrease in optic nerve head blood flow, with blood volume decreased by 9% (p = 0.095) and blood velocity reduced by 13% (p = 0.154) compared to the room air condition. During hypercapnia, optic nerve head blood flow was increased by 28% (p = 0.012), with blood volume increased by 22% (p = 0.017) and blood velocity increased by 9% (p = 0.218) as compared to the normal room air condition. CONCLUSION: Blood flow in the optic nerve head capillaries changes in response to hyperoxia and hypercapnia as demonstrated in the brain and retina. Laser Doppler flowmetry permits the noninvasive assessment of these responses in humans under conditions within the physiologic range.

Adult↗
PubMed1996

Cutaneous tuberculous abscess: a management problem.

A 66-year-old woman presented with a 6-week history of an indolent ulcerating lesion on the anterior chest wall. She had a past medical history of pulmonary tuberculosis which had been treated successfully in 1947. Biopsy of the ulcer showed granulomas and acid-fast bacilli. Cultures grew Mycobacterium tuberculosis, sensitive to all antituberculous drugs. After 7 months of treatment with isoniazid and rifampicin, there was little sign of healing. A sinogram showed a fistula leading into the plombage mass in the left upper lobe. Surgery to remove the plombage and excise the fistula was planned but was rejected by the patient as the risks of this operation are considerable. With continued antituberculous medication the discharge has reduced although the ulcer has not healed.

Abscess↗