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Biomedical subjects

J Robinson

Publications and source records attributed to J Robinson.

At least 235 records · Page 13Linked to original sources
PubMed1996

Estimation of bladder volume using portable ultrasound in clam enterocystoplasty patients.

PURPOSE: We evaluated portable ultrasound for the measurement of residual volume following clam enterocystoplasty. MATERIALS AND METHODS: Bladder volumes were measured in 25 clam enterocystoplasty patients using a portable ultrasound machine and compared with urethral catheter volumes. A similar study was performed on a control group of 50 patients with normal bladder architecture. RESULTS: There was a close correlation (r = 0.978) between ultrasound and catheter volumes in the control group with a regression line slope of 0.88. There was an equally close correlation (r = 0.960) in the clam enterocystoplasty group but the regression line slope was lower at 0.65, which suggests an underestimation of the true bladder volume. There was a significant difference (p < 0.0001) between the ultrasound-to-catheter volume ratio in the 2 groups. CONCLUSIONS: Portable ultrasound is inaccurate for the measurement of residual bladder volume in clam enterocystoplasty patients.

Case-Control Studies↗
PubMed1996

Architectural features and perceptions of community residences for people with mental retardation.

Architects, group home administrators, people with mental retardation, family members of people with mental retardation, and college undergraduates substantially agreed regarding the rated homelikeness of slides of interiors of 20 community residences for people with mental retardation ranging from institutional to homey, mean r = .87. Clusters of physical features identified using an architectural inventory were found to be associated with homelikeness ratings. Adjectives applied to rooms with these features were determined using a Q-sort method. Two factors were identified from Q-sort correlations: Homelikeness-Institutionality and Spatial Organization as well as a third variable, privacy.

Adolescent↗
PubMed1996

Interdependence of architectural features and program variables in community residences for people with mental retardation.

In an earlier study, we found that architects, group home administrators, people with mental retardation, family members of people with mental retardation, and college undergraduates rated the homelikeness of slides of community residences for people with mental retardation similarly. In addition, clusters of physical features were identified that were specifically associated with homelikeness ratings. In the present study, behavior of residents with mental retardation living in those residences was assessed using the Aberrant Behavior Checklist and direct behavioral observations. After statistically controlling for confounding variables, we found that adaptive and maladaptive behavior covaried with homelikeness ratings. In addition, we were able to identify associations between specific architectural features of residential settings and the behavior of residents living in those settings.

Activities of Daily Living↗
PubMed1995

Statistics of quantal secretion during long trains of sympathetic nerve impulses in mouse vas deferens.

1. A statistical analysis has been made of the occurrence of excitatory junctional currents (EJCs) of similar amplitude recorded with an extracellular electrode during long trains of nerve impulses to the mouse vas deferens. 2. The number of EJCs of similar amplitude that occurred in consecutive impulses during trains of 500-1000 impulses at 0.5-2.0 Hz increased with the number of EJCs evoked during the train. 3. There was no evidence of significant dependence between consecutive EJCs of similar amplitude in sixteen out of eighteen trains in eighteen preparations. 4. The time course of clusters of EJCs of similar amplitude was examined by determining the standard deviation of different groups of EJCs within a cluster throughout their time course. Most EJCs within a cluster could be grouped with a coefficient of variation < 0.1 throughout their time course. 5. The observations on EJCs of similar amplitude leave open the possibility that secretion from single varicosities is, in general, multiquantal.

Animals↗
PubMed1995

Carotid intima-media thickness is only weakly correlated with the extent and severity of coronary artery disease.

BACKGROUND: Intima-media thickness (IMT) of the common carotid artery (CCA), measured with external vascular ultrasound, has been widely used in clinical trials as a surrogate marker for coronary atherosclerosis. Despite this, the degree of correlation between carotid IMT and the extent and severity of coronary artery disease (CAD) is not known. METHODS AND RESULTS: Common carotid IMT was measured by ultrasound in 350 consecutive subjects of age 60 +/- 10 years (range, 30 to 85 years) on the day of coronary angiography. Carotid mean IMT was 0.83 +/- 0.20 mm (range, 0.43 to 1.80 mm), and maximum IMT was 1.04 +/- 0.27 mm (range, 0.49 to 2.19 mm). Coronary angiograms were analyzed by independent observers for disease severity (number of vessels with > or = 70% stenosis), extent score, and a modified Gensini score. Mean carotid IMT was weakly but significantly correlated with CAD severity (r = .26), extent (r = .23), and modified Gensini score (r = .29, P < .0001 for all correlations). Carotid IMT was not clinically useful, however, because it was not specific or sensitive enough to identify patients with or without significant CAD. Increasing age, male sex, and presence of diabetes were all associated with a significantly (P < .01) higher CAD score than the average for any level of carotid IMT, suggesting differential effects of these traditional risk factors on the coronary and common carotid arteries. CONCLUSIONS: Although carotid IMT is significantly correlated with extent and severity of CAD, the relationship is weak. This relatively poor correlation (r2 < .10) should be considered in the interpretation of clinical trials that use carotid IMT as a surrogate end point for coronary atherosclerosis.

Cardiac Catheterization↗
PubMed1995

Probabilistic secretion of quanta at somatic motor-nerve terminals: the fusion-pore model, quantal detection and autoinhibition.

The probability of detecting first, second, and later quanta secreted at release sites of a motor-nerve terminal during the early release period following a nerve impulse has been addressed. The possibility that early quantal release autoinhibits later quantal release during this period has also been ascertained. In this investigation, a model for the secretion of a quantum at a release site is developed in which, following the influx and diffusion of calcium ions to a release site protein associated with synaptic vesicles, kappa steps of association of the ions with the protein then occur at rate alpha. The release site protein then undergoes a conformational change which may not go on to completion if calcium ions dissociate from the protein at rate gamma. If this process does reach completion then a fusion-pore between the vesicle and the presynaptic membrane is created; this happens at rate delta. Key assumptions of this fusion-pore model are that the quantal secretions from each site are independent of each other, and that there is a large number of vesicles, each with a small probability of secretion, so that the number of secretions is Poisson in nature. These assumptions allow analytical expressions to be obtained for predicting the times at which first, second and later quanta are secreted during the early release period following an impulse. To test the model, experiments were performed in which the times of first, second and later quantal releases were determined at discrete regions along the length of visualized motor-terminal branches in toad (Bufo marinus) muscles. Estimates of model rate constants and of kappa from the times for first quantal secretions failed to give satisfactory predictions of the observed times of later secretions. Therefore, either the model fails, or the procedure used for detecting later quantal events as a consequence of their being masked by earlier quantal events is inadequate. To solve this detection problem, a two-dimensional analysis of the spread of charge following the secretion of a quantum at a random site on the motor-terminal branch has been done. This allows determination of the probability that later quanta will be detected following secretion of earlier quanta. The detection model was then incorporated into the fusion-pore model to predict the times at which second and later quanta occur during the early release period, based on the estimates of the model parameters derived from the analysis of first quantal releases. Good estimates were now obtained for the observed times of second and later quantal releases, indicating that appropriate procedures must be adopted for adequate detection of quantal secretions. Furthermore, the experiments provide support for the fusion-pore model. It has been suggested that the binomial nature of quantal release from the entire motor-nerve terminal may be explained if early quantal release inhibits later quantal release during the early quantal release phase (M. R. Bennett & J. Robinson 1990, Proc. R. Soc. Lond. B 239, 329-358). Although the fusion-pore detection error model gave good predictions of the observed times of first, second and later quantal releases, these may be improved if a model for autoinhibition is included. In this model the first quantum was taken as giving rise to an inhibition of secretion that propagates to surrounding release sites with a constant velocity, v. A combined model incorporating the fusion-pore detection error model and that for autoinhibition was then used to predict second and later quantal latencies, by using the first quantal latencies to determine the estimates for the parameters in the combined model. When this analysis was done on the times for quantal secretion at sites on thirteen different motor-nerve terminals, the value of v was estimated as zero in each case, so that no autoinhibitory effect was observed.

Animals↗
PubMed1995

CD14: physical properties and identification of an exposed site that is protected by lipopolysaccharide.

Soluble CD14 (sCD14) is a 55-kDa serum protein that binds lipopolysaccharide (LPS) and mediates LPS-dependent responses in a variety of cells. Using recombinant sCD14 expressed in Chinese hamster ovary (CHO) cells, we examined the structural characteristics of sCD14 and sCD14.LPS complexes. The circular dichroism and fluorescence spectra of the sCD14 indicate that it contains substantial beta-sheet (40%) and a well-defined tertiary structure with the tryptophan residues located in environments with different degrees of hydrophobicity and solvent exposure. The spectra of the sCD14.LPS complex are identical within experimental error to the uncomplexed sCD14. Changes in surface accessibility upon LPS binding were examined using limited proteolysis with endoproteinase Asp-N. This analysis revealed that aspartic acid residues at amino acids 57, 59, and 65 are susceptible to cleavage by Asp-N, while the same residues are protected from proteolytic cleavage in the sCD14.LPS complex. These results suggest that a region including amino acids 57 to 64 is involved in LPS binding by sCD14.

Amino Acid Sequence↗
PubMed1995

Regional and arterial localization of radioactive microparticles after local delivery by unsupported or supported porous balloon catheters.

Catheter-mediated intramural delivery of pharmaceutical agents after angioplasty is a potential method to reduce postangioplasty restenosis. The efficacy of such delivery has been limited both by an incomplete initial intramural deposition of delivered agents and by rapid diffusion of soluble agents from the site of delivery. The local delivery of microparticulate agents results in prolonged retention of material at the delivery site. Accordingly this study was designed to evaluate the complementary issue of the initial delivery efficiency and pattern of localization of microparticles after local catheter-mediated delivery with two types of porous balloons. These two types were a "standard" porous balloon (PB) in which hydraulic pressure both inflated the balloon and infused the agents and a porous balloon with a mechanical undergirding that permitted mechanical expansion (PB/ME) before agent infusion. Radioactive cerium 141-labeled microparticles (11.4 microns diameter) were locally delivered into atherosclerotic rabbit femoral arteries after angioplasty to test the hypothesis that use of the PB/ME apparatus would yield enhanced intramural particle deposition and decreased systemic administration by increased balloon-wall contact before microparticle infusion. Six animals underwent infusion with the PB catheter, and seven animals underwent infusion with the PB/ME catheter. An image of the in vivo particle distribution was obtained with a gamma camera during infusion, immediately after infusion, and 1, 3, and 7 days after infusion. Tissue samples from the artery, periadventitia, thigh, calf, and foot musculature, and liver were obtained at animal death, and retained radioactivity was measured with a well counter.(ABSTRACT TRUNCATED AT 250 WORDS)

Angioplasty, Balloon↗
PubMed1995

Thyrotropin-releasing hormone: does two hundred micrograms provide effective stimulation to the preterm fetal pituitary gland compared with four hundred micrograms?

OBJECTIVE: Our purpose was to compare the response of the fetal pituitary-thyroid axis to 200 and 400 micrograms of thyrotropin-releasing hormone administered to the mother immediately before delivery with a control group. STUDY DESIGN: A randomized controlled trial was conducted of 26 women at gestational ages between 24 weeks and 33 weeks 6 days who had received one or more doses of betamethasone who were expected to be delivered within 1 to 4 hours. Women received either 200 or 400 micrograms of thyrotropin-releasing hormone or were in the control group. RESULTS: Thyroid-stimulating hormone determinations on cord blood had a higher mean level in both treatment groups compared with the control group. No differences were seen in cord blood results between the two treatment groups for thyroid-stimulating hormone, thyroxine, triiodothyronine, free thyroxine, free triiodothyronine, and prolactin levels. The only other differences found were in a higher level in total thyroxine and a lower level of free thyroxine in the 400 micrograms thyrotropin-releasing hormone group compared with the 200 micrograms group in the 48-hour blood determinations. CONCLUSION: Both 200 and 400 micrograms of thyrotropin-releasing hormone provided fetal pituitary stimulation, as reflected in fetal thyroid-stimulating hormone levels in cord blood, and both gave significantly higher levels compared with a control group.

Adult↗
PubMed1995

Oral L-arginine inhibits platelet aggregation but does not enhance endothelium-dependent dilation in healthy young men.

OBJECTIVES: Our aim was to assess the effect of oral L-arginine on endothelial or platelet physiology in humans. BACKGROUND: L-Arginine is the substrate for nitric oxide synthesis, and in cholesterol-fed rabbits, oral L-arginine improves endothelium-dependent dilation, inhibits platelet aggregation and reduces atheroma. In hypercholesterolemic humans, intravenous L-arginine immediately improves endothelium-dependent dilation; however, the vascular effects of oral L-arginine in healthy humans have not previously been investigated. METHODS: In a prospective, double-blind, randomized crossover trial, 12 healthy young men 27 to 37 years old took L-arginine (7 g three times daily) or placebo for 3 days each, separated by a washout period of 7 to 14 days. RESULTS: After L-arginine, plasma levels of arginine (mean +/- SEM 303 +/- 36 vs. 128 +/- 12 mumol/liter, p = 0.01) and urea (6.7 +/- 0.5 vs. 5.2 +/- 0.2 mmol/liter, p < 0.01) were higher than levels measured after placebo, and platelet aggregation in response to adenosine diphosphate was markedly impaired (37 +/- 12% vs. 81 +/- 3%, p = 0.02). The inhibition of platelet aggregation correlated with the plasma level of L-arginine (r = 0.74, p = 0.01), and it could be completely or partially reversed by ex vivo incubation with N-monomethyl-L-arginine, a specific nitric oxide synthase inhibitor. Platelet cyclic guanosine monophosphate levels were higher after oral L-arginine than at baseline (1.91 +/- 0.46 vs. 1.38 +/- 0.40 pmol/10(9) platelets, p = 0.04). No changes were seen in fasting lipid levels, heart rate, blood pressure, endothelium-dependent dilation of the brachial artery (measured in response to reactive hyperemia, using external vascular ultrasound) (6.1 +/- 0.7% vs. 6.5 +/- 0.7%, p = NS) or in plasma levels of nitrosylated proteins (a marker of in vivo nitric oxide production) (3.5 +/- 0.5 vs. 3.3 +/- 0.4 mumol/liter, p = NS) 1 to 1.5 h after the last dose of L-arginine. CONCLUSIONS: In these healthy young adult men, oral L-arginine inhibited platelet aggregation by way of the nitric oxide pathway. However, it had no effect on systemic hemodynamic variables, plasma nitrosylated protein levels or endothelium-dependent dilation. Therefore, at certain doses, oral L-arginine may result in a relatively platelet-specific increase in nitric oxide production.

Administration, Oral↗
PubMed1995

Probabilistic secretion of quanta: spontaneous release at active zones of varicosities, boutons, and endplates.

The amplitude-frequency histogram of spontaneous miniature endplate potentials follows a Gaussian distribution at mature endplates. This distribution gives the mean and variance of the quantum of transmitter. According to the vesicle hypothesis, this quantum is due to exocytosis of the contents of a single synaptic vesicle. Multimodal amplitude-frequency histograms are observed in varying degrees at developing endplates and at peripheral and central synapses, each of which has a specific active zone structure. These multimodal histograms may be due to the near synchronous exocytosis of more than one vesicle. In the present work, a theoretical treatment is given of the rise of intraterminal calcium after the stochastic opening of a calcium channel within a particular active zone geometry. The stochastic interaction of this calcium with the vesicle-associated proteins involved in exocytosis is then used to calculate the probability of quantal secretions from one or several vesicles at each active zone type. It is shown that this procedure can account for multiquantal spontaneous release that may occur at varicosities and boutons, compared with that at the active zones of motor nerve terminals.

Animals↗
PubMed1995

Intra-uterine and juxtanatal repair of syndactyly in foetal mice.

39 foetal mice with genetic syndactyly were identified in utero at 17 days of gestation, and the right hindfoot extruded through the uterus. The syndactylous digits were separated by simple incisions. In one group (n = 25) digit separation was maintained during wound healing by the interdigital application of a silver microclip. Digit separation was also assessed in a second group of newborn mice less than 24 hours old (juxtanatal population, n = 24). Two foetuses (5%) and six newborns (25%) developed digital necrosis following microclip application. In the remaining microclipped animals (23 intrauterine and 10 juxtanatal), microclip application maintained digit separation, allowing wound healing to occur with epithelialization of the separated digits. No inflammation or scar formation occurred. In the third group (n = 22) without microclip application, the digital skin reapproximated and webbing recurred during wound healing. These studies demonstrate the need to maintain digit separation during wound healing following intra-uterine or juxtanatal syndactyly repair.

Animals↗
PubMed1995

Project 2000: a review of published research.

The findings of research into the implementation of the Project 2000 reforms of nurse education in England and Wales are reviewed in this paper. The work of nine research teams who have published their findings between 1990 and 1994 is reviewed. Following a brief summary of the major Project 2000 recommendations, the findings of the various research teams are presented. Both successes and difficulties in implementing Project 2000 are highlighted. The findings are discussed in the light of the original Project 2000 proposals, and it is concluded that, notwithstanding 'teething' difficulties, the Project 2000 reforms are proving workable in practice.

Curriculum↗