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Biomedical subjects

H Weber

Publications and source records attributed to H Weber.

At least 253 records · Page 14Linked to original sources
PubMed1990

[Ultimate tensile strength of plasma- and laser-welded cast titanium (Titaniumer, Ohara)].

The ultimate tensile strength (UTS) of titanium castings (Titaniumer, Ohara) as cast and after plasma-welding, laser-welding and soldering was investigated according to DIN 13912. The UTS of titanium as cast was 567 (+/- 36) MPa. After plasmawelding UTS decreased by 69% on the average, after laser-welding by 20%, after soldering with Ag65Cu20Pd15 (1060 degrees C) by 46% and after soldering with Ag72Cu20Ti8 (980 degrees C) by 63%. The highest tensile strength was observed in laser-welded titanium under the conditions described.

Dental Casting Technique↗
PubMed1990

Characterization of Bay U 3405, a novel thromboxane A2/endoperoxide receptor antagonist.

The thromboxane A2-receptor antagonistic properties of Bay U 3405 [(3R)-3-(4-fluorophenylsulfonamido)-1,2,3,4-tetrahydro-9-carbaz o-lepropanoic acid] have been evaluated in various pharmacologic models. Bay U 3405 specifically inhibits platelet aggregation induced by U 46619, collagen, platelet-activating factor, and the second wave of ADP (IC50 0.5, 0.07, 0.3, 0.19 microM) in human plasma. The plasma phase of ADP-induced aggregation is not affected. U 46619-induced platelet aggregation is competitively antagonized (pA2 = 6.3). In humans, ex vivo platelet aggregation is inhibited after oral application of 2 or 50 mg Bay U 3405. Bay U 3405 also specifically and competitively antagonizes U 46619-induced contractions of rabbit aortic rings (pA2 = 7.4). In vivo, Bay U 3405 protects rabbits dose dependently from arachidonic acid or collagen-induced thromboembolism (ED50 1-3 mg/kg p.o). Chronic administration of Bay U 3405 to stroke-prone spontaneously hypertensive rats reduces stroke-related mortality and diminishes the occurrence of cerebral hemorrhages. From these results, we conclude that Bay U 3405 is an orally active, selective, and competitive thromboxane A2-receptor antagonist that may be beneficial in the treatment of cardiovascular or cerebrovascular diseases.

Adenosine Diphosphate↗
PubMed1990

[Determining guidelines for metals in children's playgrounds in North Rhine-Westphalia].

In 1990, the State of North-Rhine-Westphalia established an ordinance on the quality of playground soil and sand. This ordinance includes guideline values for toxic metals (arsenic, lead, cadmium, chromium) in playground soil not covered by vegetation and quality standards for sand to be applied on playgrounds. Additionally guideline values were set for mercury, nickel and thallium. The guideline values include two categories: guideline value I represents the upper limits (95-percentiles) of the background levels of toxic metals generally found in upper soil layers in the State of North-Rhine-Westphalia. Guideline values II ("action levels") were selected on the basis of toxicological considerations. In cases where concentrations of metals above these guideline values are detected, immediate actions (urgent redevelopment measures) are required. Quality standards for playground sand were established to ensure that only noncontaminated sand is applied for playgrounds.

Child↗
PubMed1990

[Functional status of patients prior to and after orthognathic surgery].

The functional status of 12 patients was evaluated before and after orthognathic surgery for a malocclusion. The results of surgical intervention showed distinctive differences in the status of the temporomandibular joint and masticatory musculature. The number of tender muscles on palpation and the occurrence of temporomandibular joint sounds was reduced to approximately one third. However, the number of joints showing pain on palpation increased. Axiographical recordings of movement paths shawed normal values in 2 patients postoperatively. Chewing patterns were generally more harmonious, but the size of the chewing field was smaller.

Adult↗
PubMed1990

[Special ceramic hard substances as separating agents in cast-on procedures for the construction of precision attachments].

A new direct cast-on technology for the construction of telescopic crowns and precision attachments using non-precious alloys is described. Special ceramic hard substances, such as silicides and borides, are used as separating agents for the casting of the secondary structure. The application of the ceramic layers to the primary crown is accomplished with a chemical vapor deposition method. The layer thickness can be controlled and may range between some hundred nanometres and up to a few micrometres. The attainable gaps between primary and secondary casting range between 1 and 8 microns after separating and finishing.

Crowns↗
PubMed1990

Influence of age on antileukemic action, subacute toxicity and tissue distribution of ambazone in B6D2F1 mice.

The influence of age of experimental animals on the antileukemic activity, toxicity and distribution of ambazone, a new potential antineoplastic agent, was studied in 2- and 12-month-old B6D2F1 mice. The predominant effect observed was a significant reduction of the antileukemic action of this compound in old-aged mice. Together with a slight increase in several toxicity parameters this caused a marked reduction of the therapeutic index in 12-month-old mice compared to younger individuals. Furthermore, a general tendency to increased ambazone levels in liver, kidneys and thymus of old-aged mice was observed. Our data therefore provide further evidence that age has to be taken into consideration as one factor that may account for the variety of drug response frequently observed during clinical therapy with anticancer agents.

Aging↗
PubMed1990

[Enzymatic determination of glandular kallikrein in human pancreatic secretions].

A method for the enzymatic determination of tissue kallikrein (EC 3.4. 21.8) in human pancreatic juice using D-Val-cyclohexyl-Ala-Arg-4-nitroaniline as substrate as well as the reaction conditions optimized for 37 degrees C are described. The reaction is characterized by the following kinetic parameters, determined according to Hanes and Eisenthal, Cornish-Bowden: KM = 2.10(-5) mol/l; Vmax = 0.800 mumol/(l.s). The coefficient of intra-assay variation (N = 10) was determined to 2.54%. The detection limit of the assay was found to be 8.63 nmol/(l.s).

Clinical Enzyme Tests↗
PubMed1990

Dual or single infection of the terrestrial snail Solatopupa similis (Bruguière, 1792) with two protostrongylid nematodes, Muellerius capillaris (Mueller, 1889) and Neostrongylus linearis (Marotel, 1913).

The land snails Solatopupa similis were experimentally infected with two protostrongylidae, Muellerius capillaris and Neostrongylus linearis. Although the apparent rate of penetration was always high (64-91%), infection remained low (less than 3 larvae/snail); most of the larvae that penetrated the snails did not develop into second stage larvae. Rates of snail mortality recorded in infected groups were higher than those observed in non infected snails.

Animals↗
PubMed1990

[Therapeutic use of splenopentin (DA SP-5) in patients with psoriasis arthropathica].

8 patients with confirmed psoriatic arthritis were treated with splenopentin for 12 months. A relief of joint pain could be detected under this treatment both after 6 weeks (improvement of the Ritchie-indices: 44%) and after 12 months (improvement: 28%). In contrast to this, X-ray investigations show a worsening of the disease after 12 months. Therefore we conclude that splenopentin alone is not a sufficient therapeutic drug in patients suffering from psoriatic arthritis.

Adult↗
PubMed1990

[Abnormal hematopoiesis in psoriasis--in vitro studies].

Using mononuclear cells (MNC) of patients suffering from psoriasis for production of colony-stimulating factors (CSF) an abnormal colony formation in bone marrow of healthy volunteers was detected (colony-forming assay): Number of colonies per 10(5) bone marrow cells after cultivation with 10(6) MNC of patients suffering from psoriasis vulgaris: 65 +/- 14 (n = 8); psoriasis arthropathica: 63 +/- 11 (n = 8). Control values (10(5) bone marrow cells plus 10(6) MNC of healthy donors): 116 +/- 23 (n = 10). Statistical differences: psoriasis vulgaris: p less than 0.001; psoriasis arthropathica: p less than 0.001. The mechanisms responsible for these abnormalities in hematopoiesis are still unknown. They may be of pathogenic significance in psoriasis.

Adolescent↗
PubMed1989

Different selectivities of oxidants during oxidation of methionine residues in the alpha-1-proteinase inhibitor.

Oxidation of the reactive site methionine (Met) in alpha-1-proteinase inhibitor (alpha-1-PI) to methionine sulfoxide (Met(O] is known to cause depletion of its elastase inhibitory activity. To estimate the selectivity of different oxidants in converting Met to Met(O) in alpha-1-PI, we measured the molar ratio Met(O)/alpha-1-PI at total inactivation. This ratio was determined to be 1.2 for both the myeloperoxidase/H2O2/chloride system and the related compound NH2Cl. With taurine monochloramine, another myeloperoxidase-related oxidant, 1.05 mol Met(O) were generated per mol alpha-1-PI during inactivation. These oxidants attack preferentially one Met residue in alpha-1-PI, which is identical with Met 358, as concluded from the parallelism of loss of elastase inhibitory activity and oxidation of Met. A similar high specificity for Met oxidation was determined for the xanthine oxidase-derived oxidants. In contrast, the ratio found for ozone and m-chloroperoxybenzoic acid was 6.0 and 5.0, respectively, indicating oxidation of additional Met residues besides the relative site Met in alpha-1-PI, i.e. unselective action of these oxidants. Further studies were performed on the efficiency of oxidants for total depletion of the elastase inhibitory capacity of alpha-1-PI. Ozone and m-chloroperoxybenzoic acid were 10-fold less effective and the superoxide anion/hydroxyl radicals were 30-50-fold less effective to inactivate the elastase inhibitory activity as compared to the myeloperoxidase-derived oxidants. The myeloperoxidase-related oxidants are discussed as important regulators of alpha-1-PI activity in vivo.

Animals↗
PubMed1989

Affinity purification of endothia protease with a novel renin inhibitor SQ 32,970.

A novel tripeptidic renin inhibitor is described, SQ 32,970, that will potently inhibit endothia protease. This inhibitor can be coupled to Sepharose and will allow the affinity-purification of endothia protease in one step to greater than 95% purity as measured by SDS PAGE. The purified endothia protease cleaves the Lys-Pro-Ala-Glu-Phe-Nph-Arg-Leu substrate at the Phe-Nph bond with a Kcat/Km of 7445 (s-1 mM-1) at pH 3.1 and 4057 (s-1 mM-1) at pH 6.0. Affinity purified endothia protease can be crystallized in the pH range in which it is enzymatically active and can be inhibited by renin inhibitors.

Ascomycota↗
PubMed1989

[In vivo 31P magnetic resonance spectroscopy and MRI in patients with superficial tumors].

Simultaneous 31P-MR spectroscopy (MRS) and MR imaging (MRI) of 10 patients suffering from superficial tumours like carcinoma, lymphoma and adenoma, revealed significantly enhanced concentrations of phosphomonoester, phosphodiester and inorganic phosphorus in the tumour, whereas the concentration of phosphocreatine was lower in comparison to muscle tissue. In all tumours the pH showed a slight alkaline shift. The existing of necrotic regions detected by MRI was accompanied by an increase of inorganic phosphorus in the spectra. A follow-up study of a patient with a lymphoma during chemotherapy showed a tumour regression, whereas the spectra indicated a continuous approach of tumour values to the muscle values.

Contrast Media↗
PubMed1989

[Enzyme activities of the retina and vitreous body following experimental implantation of a brass splinter].

Brass splinters weighing 28 mg were implanted in the center of the vitreous of rabbit eyes. After a few days the well-known infiltration and liquefaction of the vitreous body were observed, together with retinal necrosis. Cellular and lysosomal enzymes usually found only in very low concentrations in the vitreous body increased more than a hundredfold during the inflammatory process and the increasing opacification. The enzymes assayed were lactic dehydrogenase (LDH), phosphofructose aldolase (ALD), glycerinaldehyde phosphate dehydrogenase (GAPDH), malate dehydrogenase (MDH), glucose-6-phosphate dehydrogenase (G-6-PDH), glutathione reductase (GR), beta-N-acetylglucose aminidase (NAcGA), and cathepsin-D. The kinetics of enzyme reproduction in the vitreous suggested that the cellular enzymes of the energy producing metabolism might originate both from the invading leukocytes as well as from the degrading retina. It seems likely that the cathepsin-D occurring in the vitreous originates mainly from the retina, and the beta-N-acetylglucose aminidase mainly from the pigment epithelium. The pathologically increased enzyme activity might well permit diagnostic conclusions concerning the intensity and stage of destruction of the retina by brass poisoning.

Animals↗
PubMed1989

Catheter technique for ablation of accessory atrioventricular pathway: long-term results.

Catheter ablation of an accessory atrioventricular pathway was attempted in six patients with recurrent tachyarrhythmias resistant to medication (four to five trials). Localization of the accessory pathway was performed by potential recordings with an electrode catheter from the region of the tricuspid and mitral valve rings during orthodromic supraventricular tachycardia (n = 4), during sinus rhythm (n = 1), and during ventricular pacing (n = 1). Using this mapping technique, the site of earliest atrial or ventricular activation through the accessory pathway was localized in the anterior septal (n = 2), right free wall (n = 2), posterior septal (n = 2), or left free wall (n = 1) region of the atrioventricular valve rings. The shortest ventriculo-atrial (VA) and atrio-ventricular (AV) intervals measured in the local electrograms ranged from VA = 45-70 ms, and AV = 45-65 ms, respectively. The accessory pathway responsible for the arrhythmia demonstrated exclusive retrograde (n = 4) or bidirectional (n = 2) conduction properties. A total of 13 direct-current transcatheter shocks (one to three per patient) of 20-200 J each were aimed at the site of the accessory pathway. Thereby, conduction through the accessory pathway was abolished (n = 5) or modified (n = 1) and the patients were freed from their syncope and disabling arrhythmias (follow-up: 4.6-5.9 years). The procedure was well tolerated without complications. Mapping-guided catheter ablation of accessory pathways is an effective treatment of refractory supraventricular tachyarrhythmias in selected patients.

Cardiac Catheterization↗
PubMed1989

Percutaneous Nd:YAG laser coagulation of ventricular myocardium in dogs using a special electrode laser catheter.

A novel catheter system was used for intracardiac electrogram recordings, ventricular pacing and continuous-wave Nd:YAG laser (1,064 nm) irradiation of ventricular myocardium in eight dogs. Radiation at a power of 10 W for 3, 5, and 10 seconds was delivered through a 400 microns optical fiber. Power density was 15 W/mm2. A total of 96 laser injuries (12 per dog) were produced in selected sites in both the right and the left normal canine ventricle. Ventricular arrhythmias were noted during 12 of 96 (12.5%) laser pulses. Programmed electrical stimulation performed during control study immediately (all dogs) at 2 days (two dogs), and 4 months (4 dogs) following the experiments showed no episodes of sustained or nonsustained ventricular tachycardia. Radiation energies up to 50 J (10 W over 5 s) caused focal injuries of homogeneous coagulation/fibrosis localized to the target area, without vaporizing tissue and forming craters. Morphometrically and histologically there was a direct relationship between the energy of radiation delivered, and the extent and severity of the injury produced. The maximum size of lesions measured 7/11 mm (diameter/depth). Using a special catheter system laser coagulation of myocardium can be accomplished percutaneously. This method can create controlled subendocardial injuries without major side effects and appears to overcome most disadvantages of transcatheter high energy direct-current shocks when used as a regular course of procedure in ablation of arrhythmogenic tissue in the heart.

Animals↗
PubMed1989

Computer-assisted densitometric image analysis (CADIA) for the assessment of alveolar bone density changes in furcations.

The purpose of this study was to test the applicability of computer-assisted densitometric image analysis (CADIA) for the quantitative assessment of alveolar bone density changes in furcations of multirooted teeth. In 21 patients, standardized radiographs were obtained immediately after and at 1, 6 and 12 months after periodontal flap procedures. Digitized images were obtained by means of a video-camera combined with an image processor that was linked to a computer. Quantitative information regarding density changes within windows covering furcation areas was obtained after superimposition and grey-level correction of images to be compared. 1 month after flap reflection, significantly more density loss was obtained in test furcations exposed to periodontal surgery, compared to the density changes in control furcation exposed to scaling and root planing. At 12 months, however, significantly greater increase in density was measured in test furcations compared to the 1-month results. The radiographic data were compared to the clinical parameters. In test furcations, there was a negative correlation of r = -0.52 between the GI and the loss in density at 1 month, and a negative correlation of r = -0.61 between the loss in density at 6 months and the probing attachment level at 12 months. These results indicate that CADIA may give valuable additional diagnostic information regarding alveolar bone density changes in furcations in studies on periodontal therapy.

Alveolar Process↗