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Biomedical subjects

J Hagel

Publications and source records attributed to J Hagel.

18 recordsLinked to original sources

Magnetic-field-induced band-structure change in CeBiPt.

We report on a field-induced change of the electronic band structure of CeBiPt as evidenced by electrical-transport measurements in pulsed magnetic fields. Above approximately 25 T, the charge-carrier concentration increases nearly 30% with a concomitant disappearance of the Shubnikov-de Haas signal. These features are intimately related to the Ce 4f electrons since for the non-4f compound LaBiPt the Fermi surface remains unaffected. Electronic band-structure calculations point to a 4f-polarization-induced change of the Fermi-surface topology.

Journal Article↗

The structure of the antimicrobial peptide Ac-RRWWRF-NH2 bound to micelles and its interactions with phospholipid bilayers.

The hexapeptide Ac-RRWWRF-NH2 has earlier been identified as a potent antimicrobial peptide by screening synthetic combinatorial hexapeptide libraries. In this study, it was found that this peptide had a large influence on the thermotropic phase behavior of model membranes containing the negatively charged headgroup phosphatidylglycerol, a major component of bacterial membranes. In contrast, differential scanning calorimetry showed that it had little effect on model membranes containing the zwitterionic phosphatidylcholine headgroup, the main component of erythrocyte membranes. This behavior is consistent with its biological activity and with its affinity to these membranes as determined by titration calorimetry, implying that peptide-lipid interactions play an important role in this process. The structure of this peptide bound to membrane-mimetic sodium dodecyl sulfate (SDS) and dodecylphosphocholine micelles has been determined using conventional two-dimensional nuclear magnetic resonance methods. It forms a marked amphipathic structure in SDS with its hydrophobic residues on one side of the structure and with the positively charged residues on the other side. This amphipathic structure may allow this peptide to penetrate deeper into the interfacial region of negatively charged membranes, leading to local membrane destabilization. Knowledge about the importance of electrostatic interactions of Arg and the role of Trp residues as a membrane interface anchor will provide insight into the future design of potent antimicrobial peptidomimetics.

Amino Acid Sequence↗

Field-induced metal-insulator transition in a two-dimensional organic superconductor.

The quasi-two-dimensional organic superconductor beta"-(BEDT-TTF)2SF5CH2CF2SO3 (Tc approximately 4.4 K) shows very strong Shubnikov-de Haas (SdH) oscillations which are superimposed on a highly anomalous steady background magnetoresistance, Rb. Comparison with de Haas-van Alphen oscillations allows a reliable estimate of Rb which is crucial for the correct extraction of the SdH signal. At low temperatures and high magnetic fields insulating behavior evolves. The magnetoresistance data violate Kohler's rule, i.e., cannot be described within the framework of semiclassical transport theory, but converge onto a universal curve appropriate for dynamical scaling at a metal-insulator transition.

Journal Article↗

kappa-(BEDT-TTF)2Cu[N(CN)(2)]Br: a fully gapped strong-coupling superconductor.

High-resolution specific-heat measurements of the organic superconductor kappa-(BEDT-TTF)(2)-Cu[N(CN)(2)]Br in the superconducting ( B = 0) and normal ( B = 14 T) states show a clearly resolvable anomaly at T(c) = 11.5 K and an electronic contribution, C(es), which can be reasonably well described by strong-coupling BCS theory. Most importantly, C(es) vanishes exponentially in the superconducting state which gives evidence for a fully gapped order parameter.

Journal Article↗

Clinical relevance of hepatitis G virus (HGV) infection in heart transplant patients.

To investigate whether the recently discovered hepatitis G virus (HGV) influences the clinical outcome of heart transplant recipients under immunosuppression, we determined the prevalence of HGV infections correlated with liver function and survival in 51 patients. Presence of HGV RNA and anti-E2, a marker for resolved HGV infection, were serially tested in sera from patients before and after heart transplantation (HTX) by nested RT-PCR and ELISA. Four of 51 (7.8%) patients before transplantation, and 22 of 50 patients (44%) after transplantation showed signs of persistent or resolved HGV infection. HGV infection was not associated with impairment of liver function or with patient survival. In summary, presence of HGV infection does not influence the clinical outcome in heart transplant patients.

Enzyme-Linked Immunosorbent Assay↗

Acupuncture inhibits vagal gastric acid secretion stimulated by sham feeding in healthy subjects.

In a prospective randomised study, the effect of acupuncture on sham feeding stimulated gastric acid secretion was investigated. In eight healthy volunteers (five men, three women, mean (SEM) age 26.3 (4.7) years) various methods of acupuncture were performed. Apart from the sham procedure, the acupuncture was performed at the classic acupuncture points. Electroacupuncture reduced gastric acid secretion expressed as median (range) significantly during the first 30 minute period to 1.6 (0-5.2) mmol compared with 3.8 (2.3-14.5) mmol (p < 0.05) during control period (sham feeding without acupuncture). Inhibition of gastric acid secretion by electroacupuncture was also significant during the second 30 minute period (0.2 (0-5.6) v 3.6 (0.3-9.1) mmol; p < 0.05) and for peak acid output (0.8 (0.2-5.1) v 7.6 (3.4-12.1) mmol; p < 0.05). Transcutaneous electrical nerve stimulation also resulted in significant reduction of gastric acid secretion during the first 30 minute period (1.0 (0-3.6) mmol v 3.8 (2.3-14.5) mmol; p < 0.05), and peak acid output (3.6 (1.2-12.0) v 7.6 (3.4-12.1) mmol; p < 0.05). The classic needle acupuncture, laser acupuncture, and sham acupuncture had no significant effect on gastric acid secretion. This study shows firstly that in healthy volunteers, only the versions of acupuncture using more pronounced stimulation (electroacupuncture, transcutaneous electrical nerve stimulation), but not those with only mild stimulation of the nerves (classic needle acupuncture, laser acupuncture), and secondly only acupuncture performed at defined points lead to significant reduction in gastric acid secretion.

Acupuncture Therapy↗

Cultural factors associated with health-risk behavior among the Cheyenne River Sioux.

A field study was conducted to identify cultural factors--values, beliefs, and related characteristics--associated with health-risk behavior among adult members of the Cheyenne River Sioux Tribe. The Cultural Values Survey (CVS), an instrument for measuring cultural values and related characteristics, was developed and pilot tested in the study population. This instrument, along with the Health Risk Appraisal (HRA) (an instrument developed by the Centers for Disease Control to quantify major health-related behaviors), was administered to a random sample of 429 adults in the study community. Significant differences between females and males for both cultural characteristics and health-risk behaviors were found. Females had significantly higher HRA-calculated Health Index values than males, reflecting overall healthier behaviors. Females who scored higher on cultural factors consistent with more traditional Lakota Indian lifestyles (e.g., degree of Indian blood, Lakota language spoken in the home, traditional Lakota beliefs) had higher HRA Health Index values than females scoring lower in these characteristics. Males who scored higher in factors related to self-determination (e.g., hard work, personal control, industriousness, individual action) had higher Health Index values than those who scored lower in these areas. Further testing of the CVS instrument, as well as further research from both epidemiologic and social science perspectives is essential to elucidate the nature of the relationship between cultural factors and health-related behavior.

Adolescent↗

Fate and effects of the alpha-glucosidase inhibitor acarbose in humans. An intestinal slow-marker perfusion study.

The alpha-glucosidase inhibitor acarbose has been successfully used in diabetic patients to decrease the postprandial rise in blood glucose. The aim of the present experiments was to investigate the fate and effects of acarbose along the small intestine using a slow-marker perfusion technique. In 8 healthy volunteers, jejunal and ileal loads of acarbose, glucose, and total carbohydrates were determined following a liquid, 400-kcal formula meal containing either 200 mg of acarbose or placebo. Preprandial and postprandial plasma concentrations of glucose and several polypeptide hormones were determined. Recovery of acarbose during 4 h was 65% +/- 9% (mean +/- SEM) of ingested dose in the ileum but 94% +/- 9% in the jejunum, indicating that the compound was neither degraded nor absorbed by the intestine to a major degree. After acarbose administration, ileal loads of glucose and total carbohydrates were considerably higher, whereas postprandial plasma concentrations of glucose, insulin, and gastric inhibitory polypeptide were lower when compared with placebo. The retardation of carbohydrate digestion to be inferred from these findings is confirmed by significantly elevated plasma concentrations of enteroglucagon after acarbose administration compared with placebo administration.

Acarbose↗

Human intestinal motor activity and transport: effects of a synthetic opiate.

Effects of opiates on intestinal motor activity and transport of water and electrolytes have been studied separately in previous investigations. The aim of these experiments was to evaluate simultaneously the effects of a synthetic opiate, loperamide, on motor activity and transport in the human intestine. Jejunal, ileal, and colonic perfusions were performed in 9 healthy volunteers. After application of loperamide (12 mg), cyclically recurring migrating motor complexes in the small intestine occurred at a significantly higher frequency than after application of placebo. This was primarily due to a decrease in the duration of irregular motor activity (phase II). Loperamide increased the transit time in the jejunum but not in the ileum or in the colon. Transport rates of water and electrolytes and transmural electrical potential differences were not significantly affected by the drug. These results suggest that opiates exert their constipating effect by inhibiting phase II-related irregular motor activity.

Adult↗

Antacids and gastric mucosal protection.

Aluminum hydroxide-containing antacids have a protective effect on the stomach in that they prevent grossly visible mucosal necrosis and hemorrhages produced by noxious agents, such as aspirin or absolute ethanol. Histologically, this protective effect is mainly confined to the tissue located deep in the gastric mucosa, essentially comprising gastric glands, while the damage to the surface epithelium is not significantly lessened. Accordingly, integrity parameters of the superficial epithelial layer (potential difference, mucous secretion, cell desquamation) do not indicate a protective action of antacids against damage by necrotizing agents. By contrast, significantly diminished microbleeding rates do suggest that protection by antacids works at a deeper level within the mucosa. The protective action of antacids may be mediated, at least partly, by endogenous prostaglandins, which were found to be elevated in this context.

Animals↗

Antacid protection of gastric mucosa.

Antacids containing aluminum hydroxide are protective for the stomach in that they prevent grossly visible mucosal necrosis and hemorrhages produced by noxious agents such as aspirin or absolute ethanol. Histologically, this protective effect is confined mainly to the tissue located deep in the gastric mucosa, essentially comprising gastric glands, while the damage to the surface epithelium is not significantly lessened. Accordingly, integrity parameters of the superficial epithelial layer (potential difference, mucus secretion, cell desquamation) do not indicate a protective action of antacids against damage by necrotizing agents. By contrast, significantly diminished microbleeding rates do suggest that protection by antacids works at a level deeper within the mucosa. The protective action of antacids may be mediated, at least in part, by endogenous prostaglandins, which were found to be elevated in this context.

Aluminum Hydroxide↗

[Gastric microhemorrhage and acetylsalicylic acid. Prevention using prostaglandin E2].

The possible prophylactic effect of prostaglandin E2 (PGE2) pretreatment against gastric microbleedings caused by acetylsalicylic acid was investigated in six healthy volunteers. Gastric microbleeding rate was determined by the gastric tube technique of Fisher and Hunt, at first without any medication. The test was repeated after a two-day intake of acetylsalicylic acid (four times 0.5 g/d) and after two days of the same dose, 15 minutes after the administration of PGE2 (four times 0.5 mg/d). Between the two treatment periods, their sequence randomized, there was a treatment-free pause of at least eight days. Basic gastric microbleeding rate was 0.42 +/- 0.10 ml/d (means +/- Smeans). After administration of acetylsalicylic acid this rose highly significantly elevenfold (4.59 +/- 1.64 ml/d). Prophylactic administration of PGE2 prevented this rise (0.24; 0.04-2.55 ml/d) (median; 10th-90th percentile). There were no side effects to the administration of PGE2.

Adolescent↗

Gastric cytoprotection by antacids and papaverine in rats.

Prostaglandin E2 (PGE2) prevented hemorrhagic ulceration of rat stomach mucosa induced by various procedures when given orally at a non-antisecretory dose. This effect of PGE2 is called gastric cytoprotection. We used absolute ethanol, 0.6 N hydrochloric acid and 0.2 N sodium hydroxide as damaging agents. Ranitidine at an antisecretory dose did not exhibit any cytoprotective effect. However, the poorly absorbable antacids, magnesium hydroxide plus aluminium hydroxide and aluminium phosphate inhibited the development of hemorrhagic lesions significantly. A similar protective effect was seen after intragastric administration of papaverine, which is known to stimulate endogenous prostaglandin synthesis. However, the question as to whether or not stimulation of endogenous prostaglandin synthesis is the mode of action of the cytoprotective effect of papaverine and poorly absorbable antacids, cannot yet be answered.

Aluminum Compounds↗

Gastric epithelial cell turnover, mucus production, and healing of gastric ulcers with carbenoxolone.

Nineteen healthy subjects were studied and 17 patients with gastric ulcer before and after ulcer healing with carbenoxolone. Gastric deoxytibonucleic acid (DNA) loss was measured as an index of epithelial cell turnover, and N-acetylneuraminic acid (NANA) content of gastric juice as an index of mucus secretion. In normal subjects there was a negative correlation (p less that 0-025) between gastric DNA loss and NANA secretion; the lower the cell turnover the higher the NANA production. In gastric ulcer patients DNA loss or turnover was significantly (p less than 0-01) higher than normal, and fell significantly (p less than 0-01) after four weeks' treatment with carbenoxolone when 16 of the 17 ulcers had healed. At the same time NANA output increased significantly (p less than 0-01). It is suggested that patients with gastric ulcer lose cells at a high rate, a state of affairs which is returned towards normal by carbenoxolone, thus allowing the epithelial cells to mature within the mucosa and produce more mucus.

Adult↗

The coming battle for customer information.

Companies collect information about customers to target valuable prospects more effectively, tailor their offerings to individual needs, improve customer satisfaction, and identify opportunities for new products or services. But managers' efforts to capture such information may soon be thwarted. The authors believe that consumers are going to take ownership of information about themselves and start demanding value in exchange for it. As a result, negotiating with customers for information will become costly and complex. How will that happen? Consumers are realizing that they get very little in exchange for the information they divulge so freely through their commercial transactions and survey responses. Now new technologies such as smart cards, World Wide Web browsers, and personal financial management software are allowing consumers to view comprehensive profiles of their commercial activities-- and to choose whether or not to release that information to companies. Their decision will hinge, in large part, on what vendors offer them in return for the data. Consumers will be unlikely to bargain with vendors on their own, however. The authors anticipate that companies they call infomediaries will broker information to businesses on consumers' behalf. In essence, infomediaries will be the catalyst for people to start demanding value in exchange for information about themselves. And most other companies will need to rethink how they obtain information and what they do with it if they want to find new customers and serve them better.

Community Participation↗

Unbundling the corporation.

No matter how monolithic they may seem, most companies are really engaged in three kinds of businesses. One business attracts customers. Another develops products. The third oversees operations. Although organizationally intertwined, these businesses have conflicting characteristics. It takes a big investment to find and develop a relationship with a customer, so profitability hinges on achieving economies of scope. But speed, not scope, drives the economics of product innovation. And the high fixed costs of capital-intensive infrastructure businesses require economies of scale. Scope, speed, and scale can't be optimized simultaneously, so trade-offs have to be made when the three businesses are bundled into one corporation. Historically, they have been bundled because the interaction costs--the friction--incurred by separating them were too high. But we are on the verge of a worldwide reduction in interaction costs, the authors contend, as electronic networks drive down the costs of communicating and of exchanging data. Activities that companies have always believed were central to their businesses will suddenly be offered by new, specialized competitors that won't have to make trade-offs. Ultimately, the authors predict, traditional businesses will unbundle and then rebundle into large infrastructure and customer-relationship businesses and small, nimble product innovation companies. And executives in many industries will be forced to ask the most basic question about their companies: What business are we really in? Their answer will determine their fate in an increasingly frictionless economy.

Commerce↗