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Biomedical subjects

J Weber

Publications and source records attributed to J Weber.

At least 415 records · Page 23Linked to original sources
PubMed1991

[Cartographic errors in perimetry].

Cartography in perimetry repeats the problem of the cartography of the globe: it is impossible to transfer the image properly without a distortion of either angles, distances or areas. The projection type mostly used in perimetry leads to an enlargement and a tangential deformation that increases overproportionally towards the periphery (30 degrees: +5%, 60 degrees: +20%, 90 degrees: +57%). A circular scotoma, for example, is charted as en ellipse. In the opposite case, when a test point pattern is transferred from the perimetric chart to a perimetric sphere, there is a deformation, too. The distances between the test points are reduced in tangential direction, compared to the chart. A test grid with equidistant points on the chart appears in a rhomboid or rectangular distortion. This phenomenon has to be considered in the design of test point patterns for automatic static perimeters.

Computer Graphics↗
PubMed1991

Piezoelectric lithotripsy in the treatment of symptomatic gallstone patients. A 12-month follow-up.

Between January and May 1989, 65 patients with symptomatic gallbladder stones were treated with extracorporeal piezoelectric lithotripsy (EPL) and supplementary dissolution therapy with oral bile acids. In 98% of the patients, fragmentation of stones was achieved. On average, each patient received 3.18 treatments. In addition to attacks of colic and asymptomatic changes in laboratory parameters, one hematoma of the gallbladder and one of the liver were observed, together with pancreatitis and cholecystitis in two patients each. During the follow-up period, three patients developed symptomatic bile duct stones. An endoscopic retrograde cholangiopancreatography (ERCP) with papillotomy was performed on four occasions, while one female patient had to undergo urgent cholecystectomy for inflammation of the gallbladder and empyema. Six months after the initial treatment, 36 (55%) patients were free of stones, while the stone-free rate after 12 months was 64.5% (41 of 65). Ninety percent of the patients with a solitary stone less than or equal to 2 cm in diameter became stonefree within a year. Extracorporeal piezoelectric lithotripsy is clearly a feasible procedure for the treatment of certain gallstone patients.

Adult↗
PubMed1991

A model for testing the mutagenicity of excimer laser radiation in ophthalmology.

Because excimer laser radiation is applied more and more in therapeutic and refractive corneal surgery, the possibility of mutagenic side effects of this treatment should be considered. A mutagenicity model is presented approximating closely the ophthalmological conditions when mutagenic effects are studied: Heparinized human blood is filled into the anterior chamber of an enucleated cow eye. After irradiation of the cornea with the excimer laser, the blood is removed and whole blood cultures are set up. Lymphocytes are stimulated, fixed during metaphase, and scored for chromatid and chromosome aberrations. First results obtained with this model after 248 nm laser irradiation (500 J, 277 mJ/cm2, 10 or 20 Hz) revealed no mutagenic effects. However, when the blood was exposed under the same physical conditions in a quartz chamber (positive control), statistically highly significant increases of the yields of chromatid aberrations were observed.

Adult↗
PubMed1991

[The biological availability of cefadroxil given simultaneously with N-acetylcysteine].

A preliminary study revealed that similarly to the antibiotics amoxillin, thiamphenicol, erythromycin and doxycycline, the oral cephalosporin cefadroxil (CAS 66592-87-8) can be administered simultaneously with the mucolytic n-acetylcysteine (CAS 616-91-1). In the present study 12 healthy male volunteers received in a randomised cross-over design a single oral dose of 1000 mg cefadroxil or a single oral dose of 1000 mg cefadroxil (Bidocef) plus 200 mg n-acetylcysteine. The two study days were separated by a wash-out period of one week. To determine the pharmacokinetic profile of cefadroxil, plasma and sputum were analysed by HPLC at defined intervals. Regarding the bioavailability of cefadroxil, the free combination is bioequivalent to the individual component. After administration of cefadroxil plus n-acetylcysteine, a higher cefadroxil concentration was found in the sputum compared to an administration of cefadroxil alone. However, the difference was not statistically significant. According to the results, simultaneous administration of the oral cephalosporin cefadroxil and the mucolytic n-acetylcysteine is possible without changes in the bioavailability of cefadroxil being observed.

Acetylcysteine↗
PubMed1991

[Induction of chromosome aberrations in human lymphocytes as a model for evaluating the mutagenic effect of excimer laser irradiation in ophthalmology].

A model for testing the mutagenicity of excimer laser radiation in ophthalmology is presented. In contrast to other studies using cell monolayers, in our study with this model human peripheral lymphocytes (heparinized whole blood) are exposed to laser irradiation at different conditions. The possible mutagenicity of secondary radiation after exposure of the cornea is also considered. The heparinized blood is either injected into the anterior chamber of an enucleated bovine eye or filled into a quartz chamber (positive control). After irradiation the lymphocytes are stimulated and fixed during metaphase, after which the metaphases are scored for chromatid and chromosome aberrations. In the positive control group, exposure to 248 nm excimer laser radiation (500 J, 277 mJ/cm2, 10 and 20 Hz) was followed by a highly significant increase in the yield of chromatid aberrations (chromatid breaks and achromatic lesions).

Animals↗
PubMed1991

Enhancement of the mutagenicity of anticancer drugs by the calcium antagonists verapamil and fendiline.

The enhancement of the mutagenicity of anticancer drugs by the calcium antagonists verapamil (CAS 52-53-9) and fendiline (CAS 13042-18-7) is reviewed. Both calcium antagonists enhance synergistically the induction of chromosome aberrations (dicentric and ring chromosomes) in cultured human lymphocytes by the antitumor agent bleomycin. Since two other calcium antagonists, nifedipine and diltiazem, when tested with the same system, did not show this effect, the comutagenicity of verapamil and fendiline does not seem to be related with calcium antagonism per se. Verapamil furthermore potentiates the induction of various chromosome and chromatid aberrations in Chinese hamster ovary (CHO) cells in vitro by the antitumor agent mitomycin C. In bacteria (Salmonella typhimurium) verapamil enhances synergistically the induction of gene mutations (frameshifts) by several anticancer drugs, including various anilinoacridine derivatives. When applied alone, neither verapamil which was tested in each of the three studies (human lymphocytes, CHO-cells, and bacteria) nor fendiline, which was tested only in human lymphocytes, proved to be mutagenic. To explain the comutagenicity of verapamil and fendiline, it is assumed that they prevent the mutagen (e.g., bleomycin) to be extruded from the cell. Consequently, the mutagen would be accumulated intracellularly and this would enhance its efficiency.

Animals↗
PubMed1991

[Extracorporeal piezoelectric and intracorporeal electrohydraulic lithotripsy in problematic bile duct calculi].

More than 90% of all common bile duct stones are today extracted endoscopically after papillotomy with the Dormia basket in combination with the mechanical lithotripter. For patients with endoscopically unremovable stones, there are now new therapies as an alternative to surgical intervention. Ductal stones can either be fragmented by extracorporeal shock wave lithotripsy or by peroral cholangioscopic guided electrohydraulic lithotripsy. The remaining fragments can then be easily extracted endoscopically. If the stone cannot be removed by using these new techniques, a palliative endoprosthesis can by implanted. We report on our experiences and results with the extracorporeal piezoelectric shock wave lithotripsy and the intracorporeal electrohydraulic therapy in 44 patients with complicated bile duct stones. Applying extracorporeal shock wave therapy, treatment was successful in 75% of the patients with common bile duct stones, intracorporeal electrohydraulic lithotripsy was successful in 71%. By combination of both techniques, the calculi could be removed in 84% of those patients where before one of both therapies had failed. Finally, the rate of success in the above mentioned 44 patients was 93%. It could be shown by this investigation that both therapeutic methods complete each other in the treatment of the complicated common bile duct stones.

Adult↗
PubMed1991

[A modification for reducing measurement value spread with the Hertel exophthalmometer].

The concave part of Hertel's exophthalmometer which contacts the orbita functions like an inclined plane. Therefore, the measurement is sensitive against tilting and changing of the basic distance. We modified this contact surface into a right angle. The tangents at the contact points form a common line at right angles to the measurement direction. Reproducibility of measurements was studied on 10 patients who were measured by 5 to 12 different examiners with both instruments. Accuracy improved significantly by 57%.

Equipment Design↗
PubMed1991

[Importance of cardiocirculatory and pulmonary monitoring in endoscopic retrograde cholangiopancreatography (ERCP)].

Among the side effects of endoscopy, cardiopulmonary complications are particularly important. This risk appears to be greatest in endoscopic retrograde cholangio- and pancreaticography (ERCP) because of the patient's prone position, iv sedatives and analgetics and the relatively long duration of the examination. We studied 75 patients (50 patients without and 25 patients with premedication) who were to undergo ERCP and looked at these data: age, weight, premedication, accompanying diseases, reason for this examination, blood count, oxygen saturation SaO2 (pulse oximeter), pulse, blood pressure and length of the examination. Overall, the oxygen saturation decreased considerably and two patients only had 69%. Pulse rate increased and one patient had 205 beats per minute, one 172. We looked for a correlation between SaO2, pulse rate and blood pressure and studied the patients' usual medication, the length of the ERCP, the indication for ERCP, age and hemoglobin. There was no correlation. But all patients suffering from a compromised cardiopulmonary status had received a rather heavy premedication and the ERCP was longer than in other patients. Since it is not clear which patients may develop cardiopulmonary complications, it is advisable to monitor all patients by pulse oximeter in order to avoid these complications. This seems also advisable because the rooms where the examination takes place are darkened and the patient is in a prone position so he cannot be seen clearly.

Adult↗
PubMed1991

Extracorporeal piezoelectric lithotripsy for complicated bile duct stones.

Today, common bile duct stones are extracted endoscopically. After endoscopic sphincterotomy, nearly 90% of all stones can be removed with a Dormia basket or a mechanical lithotripter. Problems are encountered if there are larger stones or a duct stenosis. New conservative therapies do serve as an alternative to surgical intervention for those few patients in whom endoscopic measures have failed. Stone fragmentation can be achieved by extracorporeal shock wave lithotripsy, and remaining fragments can be removed endoscopically. So far, authors of most reports on the successful disintegration of common bile duct stones used the Dornier lithotripter. Stone localization is thus achieved with x-rays, and the shock waves are generated by an underwater spark discharge. We report on our experiences and results with extracorporeal piezoelectric shock wave lithotripsy (EPL) in 19 patients with complicated bile duct stones. With this lithotripter, stones are visualized by ultrasound, and shock waves are produced by a piezoelectric acoustic generator. Fragmentation was achieved in 84.2%, and complete stone removal in 78.9%. These results show that piezoelectric lithotripsy is also a useful method for the treatment of complicated bile duct stones, as has already been proved for the electrohydraulic- and electromagnetic-generated shock waves systems. However, the renunciation of general anesthesia and the need for analgesia or sedation in only 25% of the treatments render this lithotripter system attractive, especially for elderly and frail patients.

Adult↗
PubMed1991

[Differential indications for peroral pancreaticoscopy].

Pancreatoscopy by the new mother-baby-endoscopy-system is an effective and safe diagnostic technique. Before the pancreatic duct can be entered by the pancreatoscope (diameter 3.2 mm), a sphincterotomy of the pancreatic sphincter must be performed. In 11 of 13 cases, the macroscopic and cytologic or histologic diagnosis respectively could be made. Main indications for this technique are intraductally localized lesions, where endoscopically guided cytology or histology can clarify the dignity of the lesion.

Ampulla of Vater↗