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At least 1,045 records · Page 58Linked to original sources
PubMed2006

Immune surveillance of the human central nervous system (CNS): different migration pathways of immune cells through the blood-brain barrier and blood-cerebrospinal fluid barrier in healthy persons.

BACKGROUND: Since for immune surveillance, only lymphocytes in the activated state are able to enter normal human central nervous system (CNS), available data are briefly reviewed to reveal lymphocyte transfer through blood-brain barrier (bbb) and blood-cerebrospinal fluid barrier (bCSFb). METHODS: With immuno-histochemical and -cytochemical methods, bbb was studied on brain microvessels and bCSFb on choroid plexus epithelium and microvessels. Lymphocyte transfer capacity on the barriers was determined with blood/CSF cell ratios revealed by quantified multicolour flow-cytometry of CSF and blood sample pairs. RESULTS: Four paths attenuated the restricted transfer of lymphocyte and NK cell subsets (none for B cells) through bbb and bCSFb, preferring memory cells in normal human brain, using different cell adhesion molecules (CAM). CAM pattern changed in choroid plexus where indication of lymphocyte recirculating from CSF into blood may exist in animal brains. CONCLUSIONS: Since efficiency of migration of blood-borne lymphocytes into CSF across bbb or bCSFb of normal human brain is not fully revealed, further data are needed to understand the transfer of immune cells across the barriers in health and disease.

B-Lymphocytes↗
PubMed2005

[Mechanisms influencing cellular physiology as a concept of treatment for wound healing disturbances].

AIM: Recent knowledge about repair mechanisms in different types of tissue is the basic of actual therapeutic efforts. Center of several experimental and clinical approaches is the influencing of angiogenesis with an also distinct meaning concerning wound healing. Therefore, application of growth factors, gene transfer, and employment of genetically manipulated cells often aim at angiogenesis. Nevertheless, manipulation of angiogenesis also leads to secondary problems such as hyperpermeability followed by impairment of local wound milieu. Our study was done to identify mechanisms to protect from disturbances of endothelial barrier function. METHOD: In a first experimental investigation on cultured endothelial cells, the influence of plasma-transglutaminase (Factor XIII) to endothelial barrier function was studied. In a second step, the influence of Factor XIII on wound healing properties was investigated in patients with a chronic venous ulceration. RESULTS: Activated Factor XIII (FXIIIA*) led to a dose-dependent reduction of endothelial cell permeability of 30 % compared to control with a maximum effect using 1 to 5 U/mL. Clinical investigation revealed a nearly complete reduction of wound secretion. CONCLUSION: Experimental studies revealed that activated Factor XIII stabilizes endothelial barrier under basic conditions as well as under conditions of induced hyperpermeability. Clinical study revealed that Factor XIII also distinctly reduces wound secretion. Therefore, plasma-transglutaminase may offer a new therapeutic option to treat the local or generalized leakage-syndrome.

Administration, Topical↗
PubMed2005

Perceived barriers to nurse practitioner practice in rural settings.

CONTEXT: Rural residents experience the same incidence of acute illness as urban populations and have higher levels of chronic illness. Overall, access to adequate rural health care is limited. Nurse practitioners (NPs) have been identified as safe, cost-effective providers in meeting these challenges in rural settings. PURPOSE: This replication study was conducted to examine NP perceptions of barriers to rural practice in Minnesota. Findings were compared to earlier studies to examine issues that have persisted over time. METHODS: A Barriers to Practice checklist was mailed to NPs from the database of the Board of Nursing of a midwestern state. Rural NPs (n = 191) identified and described barriers to practice and rated the overall restrictiveness of their practice. FINDINGS: Barriers to practice were perceived to be prevalent. Persisting barriers continued to stand in the way of full utilization of NP roles. Lack of understanding of NP roles on the part of the public and other health professionals has been particularly problematic over time. Key issues in 2001 were low salaries, lack of adequate office space, and a limited peer network. Perceived restrictiveness of the practice climate, gauged as somewhat restrictive, remained unchanged between 1996 and 2001. CONCLUSIONS: NPs have an excellent history of meeting rural primary health care needs. Enhancing the NP work environment could prove instrumental to retaining these professionals in the work force and thereby contribute to improved access and quality of care in underserved rural communities.

Adult↗
PubMed1997

Enteropathogenic Escherichia coli-induced myosin light chain phosphorylation alters intestinal epithelial permeability.

BACKGROUND & AIMS: Infection of epithelial cells with enteropathogenic Escherichia coli (EPEC) induces phosphorylation of the 20-kilodalton myosin light chain (MLC20). The physiological consequence of this biochemical observation, however, has not been discerned. The aim of this study was to determine if EPEC-induced phosphorylation of MLC20 was involved in the associated perturbation of intestinal epithelial barrier function. METHODS: Cultured intestinal epithelial cells, T84, were infected with EPEC. The effects of protein kinase inhibitors on EPEC-induced perturbation of barrier function were assessed using electrophysiological techniques. Alterations in MLC20 phosphorylation were correlated with functional responses. RESULTS: Inhibition of myosin light chain kinase, but not protein kinase C or tyrosine kinase, prevented the decrease in resistance caused by EPEC infection and significantly diminished EPEC-induced MLC20 phosphorylation. Epithelial cell monolayers genetically manipulated to constitutively increase MLC20 phosphorylation were relatively resistant to the effects of EPEC on barrier function. CONCLUSIONS: For the first time, these data show that a physiological consequence of the long-recognized increase in MLC20 phosphorylation by EPEC is perturbation of intestinal epithelial barrier function, which probably contributes to the diarrhea associated with this infection.

Bacterial Adhesion↗
PubMed1994

A calculation of all possible oligosaccharide isomers both branched and linear yields 1.05 x 10(12) structures for a reducing hexasaccharide: the Isomer Barrier to development of single-method saccharide sequencing or synthesis systems.

The number of all possible linear and branched isomers of a hexasaccharide was calculated and found to be > 1.05 x 10(12). This large number defines the Isomer Barrier, a persistent technological barrier to the development of a single analytical method for the absolute characterization of carbohydrates, regardless of sample quantity. Because of this isomer barrier, no single method can be employed to determine complete oligosaccharide structure in 100 nmol amounts with the same assurance that can be achieved for 100 pmol amounts with single-procedure Edman peptide or Sanger DNA sequencing methods. Difficulties in the development of facile synthetic schemes for oligosaccharides are also explained by this large number. No current method of chemical or physical analysis has the resolution necessary to distinguish among 10(12) structures having the same mass. Therefore the 'characterization' of a middle-weight oligosaccharide solely by NMR or mass spectrometry necessarily contains a very large margin of error. Greater uncertainty accompanies results performed solely by sequential enzyme degradation followed by gel-permeation chromatography or electrophoresis, as touted by some commercial advertisements. Much of the literature which uses these single methods to 'characterize' complex carbohydrates is, therefore, in question, and journals should beware of publishing structural characterizations unless the authors reveal all alternate possible structures which could result from their analysis.(ABSTRACT TRUNCATED AT 250 WORDS)

Biological Evolution↗
PubMed2001

A comprehensive investigation of barriers to adult immunization: a methods paper.

OBJECTIVE: Immunization rates for influenza and pneumococcal vaccines among the elderly (especially minority elderly) are below desired levels. We sought to answer 4 questions: (1) What factors explain most missed immunizations? (2) How are patient beliefs and practices regarding adult immunization affected by racial or cultural factors? (3) How are immunizations and patient beliefs affected by physician, organizational, and operational factors? and (4) Based on the relationships identified, can typologies be created that foster the tailoring of interventions to improve immunization rates? STUDY DESIGN: A multidisciplinary team chose the PRECEDE-PROCEED framework, the Awareness-to-Adherence model of clinician response to guidelines, and the Triandis model of consumer decision making as the best models to assess barriers to and facilitators of immunization. Our data collection methods included focus groups, face-to-face and telephone interviews, self-administered surveys, site visits, participant observation, and medical record review. POPULATION: To encounter a broad spectrum of patients, facilities, systems, and interventions, we sampled from 4 strata: inner-city neighborhood health centers, clinics in Veterans Administration facilities, rural practices in a network, and urban/suburban practices in a network. In stage 1, a stratified random cluster sample of 60 primary care clinicians was selected, 15 in each of the strata. In stage 2, a random sample of 15 patients was selected from each clinician's list of patients, aiming for 900 total interviews. CONCLUSIONS: This multicomponent approach is well suited to identifying barriers to and facilitators of adult immunizations among a variety of populations, including the disadvantaged.

Aged↗
PubMed2005

In vivo evidence for the efflux transport of pentazocine from the brain across the blood-brain barrier using the brain efflux index method.

The efflux transport of pentazocine (PTZ) from the brain across the blood-brain barrier (BBB) was investigated using the Brain Efflux Index method. PTZ was eliminated with the apparent elimination half-life of 13.0 min after microinjection into the parietal cortex area 2 region of the rat brain. The apparent efflux clearance of PTZ across the BBB was 137 microl/min/g brain, which was calculated from the elimination rate constant (5.35 x 10(-2) min(-1) and the distribution volume in the brain (2.56 ml/g brain). The efflux transport of PTZ was decreased in the presence of unlabeled PTZ, suggesting that PTZ is eliminated by a carrier-mediated transport system across the BBB. To characterize the efflux transport of PTZ from the brain in vivo, the effects of several compounds on the efflux transport of PTZ were investigated. P-glycoprotein (P-gp) inhibitors (verapamil and quinidine) reduced the PTZ efflux transport. In addition, the efflux transport of PTZ was inhibited by organic cations such as l-carnitine and tetraethylammonium (TEA), whereas organic anions such as p-aminohippuric acid, probenecid and taurocholate did not affect the PTZ efflux transport. The present results suggest that PTZ is transported from the brain across the BBB via l-carnitine/TEA-sensitive carrier-mediated efflux transport system(s) in addition to P-gp.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1994

Blood-brain barrier permeability measurements by double-indicator method using intravenous injection.

The double-indicator technique with intracarotid bolus injection is useful for the estimation of transfer rates across the human blood-brain barrier. A method using intravenous tracer injection is developed whereby the input is measured at a peripheral artery and the output is measured at the jugular vein. To correct for differences in the brain input of test and reference substances, a five-parameter Dirac impulse response for passage through the cerebrovascular bed is computed from the input and output of the reference substance. This response is then combined with a capillary model of the brain. This is then convoluted with the arterial input curve of the test substance to yield a theoretical test output curve, which is compared with the actual test output curve. On the basis of these two curves and an appropriate mathematical model for the brain, estimates of blood-brain barrier permeability are obtained. In the present study, the techniques are compared in 13 patients in whom alternating intracarotid and intravenous bolus injections were given. For D-glucose, the two techniques yielded similar results. This was also the case for L-phenylalanine, provided that the erythrocyte compartment was taken into account. Data obtained after intravenous injection of leucine and water yielded similar results compared with previous intracarotid data.

Adult↗
PubMed1996

Weighted-ensemble Brownian dynamics simulations for protein association reactions.

A new method, weighted-ensemble Brownian dynamics, is proposed for the simulation of protein-association reactions and other events whose frequencies of outcomes are constricted by free energy barriers. The method features a weighted ensemble of trajectories in configuration space with energy levels dictating the proper correspondence between "particles" and probability. Instead of waiting a very long time for an unlikely event to occur, the probability packets are split, and small packets of probability are allowed to diffuse almost immediately into regions of configuration space that are less likely to be sampled. The method has been applied to the Northrup and Erickson (1992) model of docking-type diffusion-limited reactions and yields reaction rate constants in agreement with those obtained by direct Brownian simulation, but at a fraction of the CPU time (10(-4) to 10(-3), depending on the model). Because the method is essentially a variant of standard Brownian dynamics algorithms, it is anticipated that weighted-ensemble Brownian dynamics, in conjunction with biophysical force models, can be applied to a large class of association reactions of interest to the biophysics community.

Algorithms↗
PubMed1997

An actual use comparison of condoms meeting Australian and Swiss standards: results of a double-blind crossover trial.

The performance of condoms in actual use has been poorly researched in the past, especially in comparing condoms that met different quality control standards as indicated by laboratory testing. The present study used a double-blind crossover design to compare the performance of 2 types of condoms in actual use; one that met the Australian and International Organization for Standardization (ISO) standards for condom quality and one that met the more stringent Swiss Quality Seal requirements. Ninety-two men recruited from Metropolitan Melbourne completed a self-report diary sheet after each condom was used which assessed the performance of the condom and the conditions under which it was used. From a total of 1917 condom uses, there was an overall breakage risk of 2.7%. The breakage risk ratio (Australian/ISO:Swiss) for all types of use was 1.16 (95% confidence interval 0.68-1.99). When subanalyses by method of entry were performed, the condoms meeting the Swiss standard appeared to fare better than the Australian/ ISO standards for anal sex (RR = 4.84, 95% CI 1.07-21.8, P = 0.022), while the opposite was the case for vaginal sex (RR = 0.74, 95% CI 0.35-1.53, P = 0.41). The result for anal use was statistically significant at the 5% level, despite being based on fewer condom trials than that for vaginal use, but this result needs to be replicated. Although the participants appeared representative of the general male population in Melbourne in the age bracket 18-46 years, there was a significant history of condom usage reported. This may have influenced the risk of breakage.

Adult↗