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Biomedical subjects

R Ward

Publications and source records attributed to R Ward.

At least 181 records · Page 10Linked to original sources
PubMed1994

Cutaneous leishmaniasis in Tachira State, Venezuela.

Cutaneous and mucocutaneous leishmaniases are widely spread in the mountainous Andean regions of South America. In Venezuela, these regions consist of the coffee-growing states of Trujillo, Merida and Tachira. Entomological and parasitological investigations in three geographically different climatic zones (Lomas Bajas, Delicias and La Grita) in Tachira state have shown a predominance of the sandfly species Lutzomyia spinicrassa (verrucarum group) and two Leishmania species, Leishmania mexicana and Leishmania braziliensis. Two transmission cycles appear to occur: a peridomestic cycle in Lomas Bajas and a sylvatic one in Delicias and La Grita.

Adolescent↗
PubMed1994

Input impedance of radiocephalic arteriovenous fistulae for haemodialysis access: its value in predicting early failure.

This study is concerned with an assessment of the quality of the blood vessels used in the construction of radiocephalic arteriovenous fistulae for haemodialysis vascular access in 20 patients. Following non-invasive preoperative assessment of the cephalic vein by means of a colour Doppler scanner, input impedance was determined intraoperatively from blood flow and blood pressure measured about 2 cm downstream of the anastomosis. The patients were re-assessed 1 day and 2, 4, 6 and 12 weeks after surgery, and the diameter and the flow through the fistulae, the location of major branches, and the presence and severity of stenoses in the cephalic veins were determined non-invasively. Five fistulae failed within the 12 weeks period following surgery, mainly due to thrombosis. In a further 3 patients, the fistulae were patent but did not achieve an adequately high blood flow and dilate sufficiently for haemodialysis and were therefore considered to be essentially failed. The impedance moduli from 0 to 10 Hz as well as the average impedance modulus of successful fistulae were significantly lower than those of fistulae that subsequently failed. An attempt was made to locate the presence of reflection sites (i.e. stenoses and branches) from the minima in the impedance modulus spectra. Their locations were compared with those of the reflection sites detected by ultrasound 2 weeks after surgery. However, not all reflection sites detected 2 weeks after surgery were located by the impedance method. It is recommended that both preoperative examination and intraoperative haemodynamic measurements be made to improve the accuracy of the assessment.

Arteriovenous Shunt, Surgical↗
PubMed1994

Histidine residues near the N terminus of staphylococcal alpha-toxin as reporters of regions that are critical for oligomerization and pore formation.

Chemical modification of histidine residues in staphylococcal alpha-toxin leads to loss of functional activity. Site-directed mutants of the toxin in which each of the four histidine residues was replaced by several amino acids were therefore produced. The mutant proteins were purified and characterized. Exchange of H-259 or H-144 was sometimes tolerated without reduction in hemolytic activity. These histidine residues are thus not essential for toxin function. Exchange of H-35 and H-48, however, had marked effects. H-35 mutant toxins bound with high affinity to rabbit erythrocytes but displayed faulty oligomerization and were unable to form pores. H-48 mutant toxins also had severely impaired hemolytic activity due probably to faulty hexamerization. We interpret these results to indicate that the N-terminal domain of alpha-toxin in the region of H-35 and H-48 is involved in protomer-protomer interactions that underlie the hexamerization and pore-forming process.

Animals↗
PubMed1994

Enhancement of ethanol induced rectal mucosal hyper regeneration with age in F344 rats.

Experimental studies in rats have shown an independent stimulation of rectal cell turnover by either chronic ethanol consumption or age. In this study the combined effect of these two factors on colorectal cell regeneration has been investigated. Ninety male F344 rats aged 2, 12, and 22 months were pair fed nutritionally adequate liquid diets containing 36% of total energy either as ethanol or isoenergetic carbohydrates. After four weeks of feeding, colorectal crypt cell production rates were measured using a stathmokinetic technique with vincristine. While age by itself did not affect colorectal cell renewal, chronic ethanol consumption stimulated rectal, but not colonic crypt cell production rate in an age dependent manner. While no significant effect of ethanol was noted in young animals, cell proliferation was significantly enhanced in middle aged animals by 81% (4.1 (2.7-5.5) v 7.4 (6.0-8.7) cells/crypt/hour, p < 0.001) and in old animals by 138% (4.5 (3.3-5.6) v 10.7 (8.9-12.4) cells/crypt/hour, p < 0.001) after ethanol ingestion. Because acetaldehyde, the first and most toxic metabolite of ethanol, has been detected in the colorectal mucosa and may lead to tissue injury influencing cell regeneration, acetaldehyde concentrations have been measured in the colons of 15 male F344 rats of various ages after an acute intraperitoneal dose of ethanol (2.5 g/kg bodyweight). There was a significant positive correlation between crypt cell production rate and acetaldehyde concentrations measured in the distal and proximal colon after an acute dose of ethanol (r = 0.5955, p < 0.005). These data clearly show that the ethanol mediated stimulation of cell regeneration in the rectum is age dependent. As reported earlier, there was found indirect evidence that acetaldehyde participates in the pathogenesis of rectal hyperregeneration after chronic alcohol consumption. This hyperregeneration of the rectal mucosa after alcohol drinking could by itself favour carcinogenesis, which is especially relevant in old age.

Acetaldehyde↗
PubMed1994

An experimental re-evaluation of the primary visual system of the European chameleon, Chamaeleo chameleon.

The retinofugal projections of the chameleon were investigated by means of autoradiography, horseradish peroxidase and fluorescent techniques after intraocular injection of tracers. An ipsilateral contingent of visual fibers and projections is absent. The retinal fibers decussate completely in alternating fascicles at the optic chiasma and course to terminate in two hypothalamic nuclei (nucleus suprachiasmaticus and nucleus opticus periventricularis hypothalami posterior), six thalamic nuclei (nucleus ovalis, nucleus geniculatus lateralis dorsalis partes lateralis and medialis, nucleus geniculatus lateralis ventralis, lateral part of nucleus dorsolateralis anterior, and nucleus ventrobasalis), four pretectal nuclei (nucleus griseus tectalis, nucleus lentiformis mesencephali, nucleus geniculatus pretectalis and nucleus posterodorsalis), the optic tectum (stratum griseum et fibrosum superficiale) and the tegmental nucleus opticus tegmenti. Our findings are, in general, compatible with previous descriptions of the primary visual system in other species of lizards. However, they indicate three features particular to chameleons: first, the total absence of an ipsilateral retinofugal projection; second, the existence of an additional hypothalamic visual center located in the posterior mediodorsal hypothalamus; and third, the large size of nucleus opticus tegmenti. These features are discussed in terms of the taxonomic position of chameleons with respect to other lizards.

Animals↗
PubMed1994

Angiotensinogen gene in human hypertension. Lack of an association of the 235T allele among African Americans.

The frequency of the 235T and 174M alleles of the angiotensinogen gene, previously reported to be associated with hypertension in Caucasians and Japanese, was compared between 57 hypertensive African Americans and 130 normotensive African Americans sampled as part of a community survey of hypertension in the Chicago area. The frequency of the 235T allele was unrelated to hypertension status (cases, 83%, control subjects, 82%), as was true for the 174M allele. Compared with Caucasians, the frequency of the 235T allele was twice as high in this African American population, while the frequency of the 174M allele was similar. Even higher frequencies of the 235T allele (93%) were noted in a sample of 122 Nigerians. It appears that the 235T allele is very common in populations of West African origin, although we found no evidence that it confers risk of hypertension.

Adult↗
PubMed1994

Immunoreactivity to glial fibrillary acid protein (GFAP) in the brain and spinal cord of the lamprey (Lampetra fluviatilis).

In contradiction to previous results, under certain conditions, it is possible to demonstrate GFAP immunoreactivity in the brain and spinal cord of a jawless vertebrate. The critical parameters appear to be (1) fixation with 4% paraformaldehyde at pH 7.4, (2) a very short period (2-6 hr) of postfixation, and (3) immunovisualization by the avidin/biotin/peroxidase technique rather than immunofluorescence or PAP techniques. Immunoreactivity appears throughout the brain and spinal cord, most frequently as fine prolongations normal to the pial surface, which can on occasion be traced to cell bodies near the ventricles or in the ependymal layer. The evolutionary implications of the presence of glial fibrillary acidic protein in a member of the Agnatha are discussed.

Animals↗
PubMed1994

A continuous quality improvement project to improve the quality of cervical Papanicolaou smears.

OBJECTIVE: To improve the quality of cervical Papanicolaou smears by continuous quality improvement techniques. METHODS: The study used a Papanicolaou smear data base of over 200,000 specimens collected between June 1988 and December 1992. A team approach employing techniques such as process flow-charting, cause and effect diagrams, run charts, and a randomized trial of collection methods was used to evaluate potential causes of Papanicolaou smear reports with the notation "inadequate" or "less than optimal" due to too few or absent endocervical cells. Once a key process variable (method of collection) was identified, the proportion of Papanicolaou smears with inadequate or absent endocervical cells was determined before and after employment of a collection technique using a spatula and Cytobrush. We measured the rate of less than optimal Papanicolaou smears due to too few or absent endocervical cells. RESULTS: Before implementing the new collection technique fully by June 1990, the overall rate of less than optimal cervical Papanicolaou smears ranged from 20-25%; by December 1993, it had stabilized at about 10%. CONCLUSION: Continuous quality improvement can be used successfully to study a clinical process and implement change that will lead to improvement.

Databases, Factual↗
PubMed1993

T- and B-cell functions and epitope expression in nonhuman primates immunized with simian immunodeficiency virus antigen by the rectal route.

Transmission of human immunodeficiency virus (HIV) in North America and Europe occurs most commonly through the rectal mucosa during homosexual intercourse. The simian immunodeficiency virus (SIV) macaque model has been used to investigate rectal immunization. The vaccine used was a recombinant SIV gag p27 expressed as hybrid Ty virus-like particles (Ty-VLP). Sequential ororectal (OR) mucosal immunization was compared with i.m. immunization. Whereas both routes of immunization induced serum IgA and IgG p27 antibodies, only OR immunization induced rectal secretory IgA antibodies. Specific CD4+ T-cell proliferative responses to stimulation with p27 were found after i.m. immunization only in the blood and spleen, but after OR immunization they were found in the internal iliac and inferior mesenteric lymph nodes in addition to the blood and spleen. T-cell epitope mapping of the proliferative responses of short-term cell lines (STCLs) grown from peripheral blood or lymphoid cells revealed a major epitope within the polypeptide 121-150 after either route of immunization. Two minor T-cell epitopes were found within peptide 41-80 in STCLs from splenic and circulating cells. B-cell epitope mapping of serum or biliary IgA and IgG antibodies revealed two overlapping or adjacent immunodominant epitopes to the T-cell epitopes within the polypeptides 121-170 and 51-90. The results suggest that rectal augmented by oral immunization with a recombinant particulate antigen in nonhuman primates elicits secretory IgA and to a lesser extent IgG responses in the draining lymph nodes and the rectal mucosa, whereas systemic immunization targets predominantly splenic and circulating T- and B-cell responses. These findings may have important implications in the strategy of designing vaccines in prevention of homosexual transmission of HIV infection.

Administration, Rectal↗
PubMed1993

Crystallization and preliminary X-ray analysis of a truncated tissue metalloproteinase inhibitor delta 128-194 TIMP-2.

Crystals of an active truncated form of a human tissue metallproteinase inhibitor (delta 128-194 TIMP-2), a protein implicated in a number of diseases of the connective tissues, have been grown in a form suitable for study by X-ray diffraction analysis. Crystals grow using polyethylene glycol 600 as a precipitant and are in space group P2(1)2(1)2, with cell dimensions a = 75.28 A, b = 100.77 A, c = 31.45 A. The asymmetric unit appears to contain two molecules of delta TIMP-2 with a Vm value of 2.3 A3/dalton. The crystals diffract to Bragg-spacings beyond 2.5 A. Native data to 3.2 A have been collected and a search for heavy-metal derivatives is in progress.

Crystallization↗
PubMed1993

Preaxial ray reduction defects as part of valproic acid embryofetopathy.

It is well known that prenatal exposure of valproic acid (VPA) may be associated with the occurrence of neural tube defects (Robert and Gibaud, 1982). Additional adverse effects related to VPA exposure include craniofacial abnormalities, skeletal defects, brain defects, cardiovascular defects, and urogenital defects (DiLiberti et al., 1984; Winter et al., 1987; Huot et al., 1987; Jager-Roman et al., 1986; Martinez-Frias, 1990). Recently, radial ray reduction has been reported as a severe type of skeletal defect associated with VPA exposure (Jager-Roman et al., 1986; Huot et al., 1987; Verloes et al., 1990). We report two additional cases of this severe limb reduction defect as part of a broader pattern of altered morphogenesis in fetuses exposed to VPA and to confirm an association between such severe specific skeletal defects and VPA exposure. We briefly review teratologic studies in experimental animals which document the biologic plausibility of this association, and suggest that fetuses exposed to VPA undergo detailed prenatal ultrasonographic evaluation of the limbs.

Abnormalities, Drug-Induced↗
PubMed1993

The primary visual system of flatfish: an evolutionary perspective.

The retinal projections of two species of flatfish (Scophthalmus maximus, Scophthalmidae; Platichthys flesus, Pleuronectidae) were investigated by autoradiography and by a HRP technique. Contralateral projections to five hypothalamic centres (area optica preoptica ventralis, nucleus opticus preopticus parvocellularis posterior pars lateralis, n. suprachiasmaticus, n. opticus hypothalami ventromedialis and area optica hypothalami posterior), thirteen thalamo-pretectal centres (nucleus opticus dorsolateralis (partes medialis, ventralis and lateralis), n. opticus ventrolateralis, n. opticus commissurae posterioris (partes dorsalis and ventralis), n. opticus accessorius, n. geniculatus lateralis mesencephali, nn. opticus pretectalis dorsalis, medialis and ventralis and n. corticalis), three layers of the optic tectum (stratum opticum pars externa, stratum fibrosum et griseum superficiale, stratum album centrale), and a single target in the tegmentum (n. opticus tegmenti mesencephali dorsalis), were identified in both species. Interspecific variation of the contralateral visual projections is relatively small. Ipsilateral visual projections of fibres which recross the midline in the minor and transverse commissures were also identified; in S. maximus this ipsilateral contingent is poorly developed and concerns principally hypothalamic structures, while in P. flesus the ipsilateral projections are considerably more extensive and involve both hypothalamic and thalamo-pretectal primary visual centres. No differences in the projections from the fixed and from the migrated eye were observed in either species. The findings are discussed in the general context of the existing literature on the visual projections of teleosts, in an attempt to characterize the primary visual system of the Pleuronectiformes in an evolutionary context.

Animals↗
PubMed1993

The repair of inguinal hernias using carbon fibre patches--a five-year follow-up.

One hundred and eight inguinal hernias were treated following a standard surgical technique, using 3-mm thick loosely woven carbon-fibre patches. The average follow-up was five and a half years. There was one recurrence. Otherwise, excellent clinical results without pain were found in all but one patient and only a further three experienced a slight discomfort in the area of the implant, without any restriction on function. The technique is simple and permeation of the carbon-fibre patch by fibrous tissue showed a lasting repair.

Adult↗
PubMed1993

The search for meanings in nursing: could Facet Theory be a way forward?

This paper examines some of the underlying tenets of Benner & Wrubel's Primacy of Caring, and suggests the use of Facet Theory as a possible route to overcome criticisms of the lack of systematic data collection and analysis in this approach to nursing research. Some of the steps undertaken in Facet Theory are described, and its use in wider nursing research discussed. It is proposed that Facet Theory offers a method of studying the multidimensional nature of nursing, which has the potential for a scientific approach without losing the essential ontological data.

Linguistics↗
PubMed1993

A common-source outbreak of callitrichid hepatitis in captive tamarins and marmosets.

Callitrichid hepatitis (CH) is a highly fatal, emerging arenavirus disease of captive South American marmosets and tamarins (Callitrichidae), including the endangered golden lion tamarin. A common-source outbreak of CH in golden lion tamarins and pygmy marmosets at a US zoo resulted from a single feeding of the primates with newborn mice in apparently infected with lymphocytic choriomeningitis virus (LCMV). Isolates from livers of mice and primates were related to isolates from previous CH outbreaks and to laboratory strains of LCMV by serology and nucleic acid hybridization, and 2 surviving animals developed antibody to other LCMVCH isolates and to laboratory strains of LCMV. Thus, LCMV, an arenavirus prevalent in wild mice in the US, can cause sporadic fatal hepatic disease in primates. Exposure of humans to wild or laboratory mice or to marmosets and tamarins that are infected with wild-type strains of LCMV poses the danger of serious disease.

Animals↗