Bibliothek

Notizen: Spin injection into and spin transport through silicon spacer layers in iron/silicon/cobalt structures has been investigated. Ultrahigh vacuum evaporated silicon spacers of varying crystal quality from amorphous to epitaxial of thicknesses from 10 to 200 Å were shown to improve their electrical conduction with increasing crystallinity, but no spin dependent transport was observed through the structure. Silicon and iron interdiffusion was also observed at the interfacial region. Device quality silicon was studied using 460 and 540 μm doped silicon wafers of resistivity 0.1 and 1 Ω cm, respectively, polished on both sides, onto which were deposited iron and cobalt layers. Sharp metal-semiconductor interfaces were achieved in this way, but no spin dependent transport, putting an upper limit on the spin diffusion length in device quality silicon wafers. © 2000 American Institute of Physics.

Notizen: Background.  Duodenal ulcer in adults chronically infected with Helicobacter pylori is associated with a polarized T-helper cell type 1 (Th1) mucosal immune response, with a predominantly immunoglobulin G2 (IgG2) systemic specific response. It has been suggested that children colonized by H. pylori also produce a mucosal Th1 response, but there are few studies that have measured IgG subclass responses in children with duodenal ulcer.Materials and methods.  Seven children with endoscopically proven duodenal ulcer and H. pylori infection and 18 children with biopsy proven H. pylori infection but no duodenal ulcer had relative concentrations of IgG subclass responses (IgGsc) against H. pylori antigens measured by ELISA. Eighteen IgG seropositive adults acted as controls. The range of antigens recognised by IgG1 and IgG2 subclass responses were investigated by Western blots.Results.  There were no differences in mean IgGsc responses between children with or without duodenal ulcer. Adults produced an IgG2 predominant response. Western blots showed no qualitative differences in antigens recognised by IgG1 or IgG2.Conclusion.  Children with duodenal ulcer, in contrast to adults, produce an IgGsc response consistent with a mucosal Th2 response to H. pylori regardless of the presence of duodenal ulceration. This suggests that disease causation amongst children with H. pylori associated duodenal ulceration may not be dependant upon a mucosal Th1 biased response.

Notizen: Lucilia sericata larvae, or greenbottle fly maggots, placed within chronic wounds have been observed to remove necrotic tissue and infection. They are also believed to actively promote granulation tissue formation. Interactions between fibroblasts and the surrounding extracellular matrix play a crucial role in tissue formation, influencing fibroblast proliferation, migration, and tissue remodeling. For example, the strength of cell adhesion to surfaces coated with extracellular matrix influences cell motility. L. sericata larval excretory/secretory products having previously been shown to modify fibroblast adhesion to collagen and particularly fibronectin, it was hypothesized that these products would alter fibroblast migration. This was investigated using a two-dimensional in vitro wound assay, time-lapse digital photography, enzyme class-specific substrates and inhibitors, and gel electrophoresis. Results showed that L. sericata excretory/secretory products promoted fibroblast migration upon a fibronectin-coated surface. This was related to the degradation of fibronectin by serine proteinases within maggot excretion/secretions. The presence of a metalloproteinase activity may also have played a role. Thus, a possible mechanism by which maggots enhance tissue formation within wounds may be via the promotion of fibroblast motility, providing for a wider distribution of viable fibroblasts.

Notizen: Metabotropic γ-aminobutyric acidB (GABAB) receptors for the major inhibitory transmitter GABA, together with metabotropic glutamate (mGLuRs) receptors, the extracellular calcium-sensing receptors (CaSRs), some V2R pheromone receptors and T1R taste receptors, belong to the family of 3 G-protein-coupled receptors (GPCRs). GABAB receptors are known to control neuronal excitability and modulate synaptic neurotransmission, playing a very important role in many physiological activities. These receptors are widely expressed and distributed in the nervous system and have been implicated in a variety of neurodegenerative and pathophysiological disorders including epilepsy, spasticity, chronic pain, depression, schizophrenia and drug addiction. To form a functional receptor entity, GABAB receptors must exist as a heterodimer consisting of GABAB1 and GABAB2 receptor subtypes with two 7-transmembrane proteins, and these subunits arise from distinct genes. The GABAB1 subunit binds the endogenous ligand within its extracellular N-terminus, whilst the GABAB2 subunit is not only essential for the correct trafficking of the GABAB1 subunit to the cell surface, but is also responsible for the interaction of the receptor with its cognate G-protein. Allosteric modulation has recently been recognized as an alternative pharmacological approach to gain selectivity in drug action. It is now generally accepted that modulators acting at the allosteric sites provide a novel perspective for the development of subtype-selective agents acting at GPCRs. These agents interact with allosteric binding sites quite separate from the highly conserved agonist binding region. In this review, we present a new class of phenylalkylamines, based on the lead compound fendiline, that are potent positive potentiators of GABAB receptor-mediated function and discuss their putative clinical applications. It is proposed that these new modulators may have therapeutic value in GABAB receptor pharmacology and are capable of selectively modifying GABAB receptor function. The allosteric modulators are offering an attractive and novel means to identify new leads, that are devoid of side effects associated with GABAB receptor agonists, and may, therefore, represent a major advance in the drug discovery process.

Notizen: Background.  Helicobacter pylori, one of the commonest chronic bacterial infections of humankind, is an important risk factor for gastric carcinoma. It has also been suggested to be present in dental plaque. This study investigated the potential link between the number of teeth lost and H. pylori seropositivity at age 50 years.Methods.  H. pylori seropositivity at age 50 years was investigated among 334 individuals born in Newcastle upon Tyne, United Kingdom, in May and June 1947 and related to the number of teeth lost, after adjusting for socioeconomic status.Results.  The unadjusted risk of being seropositive for H. pylori increased with increasing number of teeth lost (odds ratio per tooth 1.03, 95% confidence interval 1.01–1.06, p = .019). However, after adjustment for socioeconomic status at birth and at age 50 years, the relationship was no longer significant (p = .36).Conclusions.  Our results, obtained using prospectively collected data, suggest that any relationship between poor oral health and seropositivity to H. pylori may be due to both tooth loss and H. pylori colonization being associated with socioeconomic status and related factors.

Notizen: Helicobacter pylori infection is very common in Africa, yet peptic ulcer disease and gastric malignancy are rare.〈section xml:id="abs1-3"〉〈title type="main"〉Aim.The aim of this study was to quantify mucosal responses to H. pylori in Gambian adults and children and to estimate the prevalence of antibodies to bacterial virulence factors (cagA and vacA) in a symptomatic population.〈section xml:id="abs1-4"〉〈title type="main"〉Patients and methods.Adults (mean 36 SD 12 years) with dyspepsia and children (mean 1.4 years SD 0.4 years) with malnutrition underwent gastroscopy with biopsy. Blood was simultaneously drawn for cagA and vacA antibody status. Histopathological scoring used the modified Sydney classification.〈section xml:id="abs1-5"〉〈title type="main"〉Results.Both adults (n = 45) and children (n = 37) mainly demonstrated chronic mild antral inflammation. Only 2/83 cases of focal atrophy (GA) and 4/83 cases of intestinal metaplasia (IM) were observed. Adults tended to demonstrate more frequent acute (AI) and chronic inflammation (CI) (38% compared with 18% and 85% compared with 72%, respectively). Sixty-seven percent of children were cagA IgG+ and 21%vacA IgG+ and 93% of adults were IgG cagA+ and 86%vacA+. There were no differences in mucosal responses between those who were cagA or vacA positive compared with those who were negative.〈section xml:id="abs1-6"〉〈title type="main"〉Conclusion.Gambian adults and children mount a CI response to H. pylori but GA, IM and AI are uncommon. cagA and vacA are commonly expressed in Gambian strains of H. pylori. Further studies are needed in order to confirm that GA and IM are not late findings in old age.

Notizen: We use survey data and field research to investigate the effects of employee involvement practices on outcomes for blue-collar workers in the auto-supply industry. We find these practices raise wages by 3–5%. The causal mechanism linking involvement and wages appears to be most consistent with efficiency-wage theories, and least consistent with compensating differences. We find no evidence that employee involvement affects plants' survival or employment growth.

Notizen: Background: Despite recent advances in therapy for atrial fibrillation (AF) following cardiac surgery, the potential superiority of antiarrhythmics over rate control therapy for suppression of AF has not been convincingly demonstrated. We sought to determine whether early treatment of AF following cardiac surgery with antiarrhythmics improves clinical outcome, as measured by recurrence rate, length of stay, and adverse events.Methods: Out of 1100 consecutive patients undergoing cardiovascular surgery from July 1997 to June 1998, AF was identified in 425 (38.6%) prior to discharge. Patients with a history of chronic AF prior to cardiovascular surgery and patients who died within 48 hours of cardiovascular surgery were excluded from the analysis; 365 patients were studied. Group I patients received rate control alone; Group II received antiarrhythmic drugs within 24 hours of the first onset of AF.Results: With the exception of frequency of pulmonary disease (4 vs 17, P = 0.009), CABG rate (35 vs 45%, P = 0.045), and rate of valve surgery (24 vs 15%, P = 0.028), there were no significant differences in clinical characteristics between the two groups. The rate of return to sinus rhythm within 24 hours (80 vs 82%), and the percentage of patients leaving the hospital in sinus rhythm (90 vs 92%) were similar between the two groups, as were total length of stay (10.6 ± 6.0 vs. 11.4 ± 5.8, P = 0.159) and postoperative length of stay (8.4 ± 15.0 vs. 9.4 ± 5.3, P = 0.061). Embolic event rates were similar in both groups (eight in Group I and three in Group II). Proarrhythmia occurred in two patients receiving early antiarrhythmic therapy.Conclusion: Traditional use of early antiarrhythmic therapy appears to provide no clear advantage to rate control after cardiovascular surgery in terms of length of stay, freedom from AF at discharge, and other common clinical outcomes. Routine use of antiarrhythmics for suppression of AF should be carefully reconsidered. A.N.E. 2000;5(4):365–372