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Biomedical subjects

H Weber

Publications and source records attributed to H Weber.

At least 19 recordsLinked to original sources

A thermostable, sequence-specific restriction endonuclease from Bacillus stearothermophilus: BstPI.

A restriction endonuclease, BstPI, was purified from a strain of B. stearothermophilus, and its cleavage specificity was determined. The enzyme cleaves at palindromic sites of the general structure: (Formula: see text) where N.N' can be any base pair. It produces phosphorylated 5'-termini which are single stranded over a length of 5 nucleotides. Ends generated by cleavage with BstPI can be rejoined by DNA ligase.

Base Composition

Fast and slow myosin within single skeletal muscle fibres of adult rabbits.

There is good evidence for the coexistence of different myosin types both in developing muscles and in Purkinje cells from adult chicken hearts. In skeletal muscle fibres of adult animals, however, coexistence of fast (FM) and slow (SM) myosin has only been demonstrated after long-term electrical stimulation. The term 'promiscuity' has recently been coined to describe the coexistence of different myosin isoenzymes within a single fibre. Using novel, refined immunological methods we demonstrate here the presence of both FM and SM within single fibres of the musculus tibialis anterior of adult rabbits. Essentially identical results were also obtained with other muscles. Our findings imply that the genes coding for FM and SM can be expressed simultaneously within the same cell throughout an animal's entire life, and not only during development or after artificial electrical stimulation.

Animals

[Effect of polyene antibiotics and their perhydrovderivatives on intact cells and protoplasts of yeast Candida guilliermondii].

Perhydroderivatives of polyene antibiotics have a much lower activity against eukaryotic cells than the polyene antibiotics itself. Bacterial cells are normally resistant against most polyene antibiotics and their perhydroderivatives. In earlier experiments with wall less L-form cells of Escherichia coli we have shown that the bacterial cell wall may be responsible for the resistance of the intact bacterial cells against polyene antibiotics and their perhydroderivatives by masking internal target sites. In the present paper we studied the effect of polyene antibiotics and their perhydroderivatives on intact cells and protoplasts of Candida guilliermondii. Our experiments have shown that most of the perhydroderivatives studied had a lower activity against intact cells as well as protoplasts than the corresponding polyene antibiotics. This means that in the case of eukaryotic cells the cell wall as a penetration barrier cannot mainly be responsible for the low activity of perhydroderivatives. The results are compared with those obtained previously with intact cells and protoplast type L-form cells of E. coli.

Anti-Bacterial Agents

Substructural studies on sporulation of Saccharomycopsis lipolytica.

During sporulation of diploids from crosses between different strains of the yeast Saccharomycopsis (Candida) lipolytica irregular numbers of ascospores per ascus have been observed. Using the serial section method it could be shown now by means of electron microscopy that in one-, two-, and three-spored asci unenclosed "naked" nuclei occur additionally to nuclei incorporated in mature spores. It was demonstrated that the production of less than four spores per ascus in this yeast is not the result of a lack of meiotic products but of the nonutilization of nuclei from meiosis. In 2--4 spored asci usually four products of meiosis in form of enclosed and free nuclei could be demonstrated which indicate a normal meiotic division. All ascospores derived from asci with different spore numbers are uninuclear. It is assumed that a defect in spore formation caused by structural changes of chromosomes or aneuploidy should give rise to the occurrence of non incorporated nuclei and spore irregularity. It was concluded that meiosis and spore formation in Saccharomycopsis lipolytica seem to represent parallel and coordinated processes which generally resemble those recorded for Saccharomyces cerevisiae and Hansenula species.

Ascomycota

Greatly decreased susceptibility of nonmetabolizing cells towards detergents.

The addition of different detergents to Chlorella cells that had previously accumulated 6-deoxyglucose causes a rapid release of the hexose analogue into the medium. This effect is independent of the nature of the detergent and is observed only when the cells are in an energized state. Thus, in the presence of the uncoupler p-trifluoromethoxycarbonylcyanide phenylhydrazone or of inhibitors such as N-ethylmaleimide, the cells show a greatly reduced susceptibility towards detergents. Similarly, the detergent-induced loss of accumulated alpha-aminoisobutyric acid from Saccharomyces cerevisiae and of potassium from Escherichia coli is also strongly affected by the energy state of the cells. The differential susceptibility of energized and nonenergized cells was observed at all detergent concentrations tested. Measurements of substrate efflux at different concentrations of Triton indicated that only Triton monomers are responsible for the increase in permeability. The absorption of [14C]Triton X-100 by Chlorella and the binding of detergent to the cells were measured in the presence of metabolic inhibitors. Again, nonenergized cells bound a significantly lower amount of Triton X-100. The amphiphilic antibiotic nystatin produced effects on cell permeability similar to those of detergents, whereas toluene, which is apolar, gave opposite results.

Aminoisobutyric Acids

Excretion of metrizamide (Amipaque) in humans following lumbar subarachnoid injection.

The excretion of metrizamide through the kidneys and intestinal tract was determined in 10 patients submitted to myelography because of sciatica, for a period of 7 days following the examination. In the faeces, less than 5 per cent of the injected contrast medium was recovered during this period. Total recovery in the urine varied considerably from patient to patient, but most of the contrast medium was excreted during the first 48 hours. From the fourth day on, only small amounts were excreted, but even on the 7th day 3 to 11 mg iodine remained, which corresponds to 6 to 22 mg of metrizamide.

Adolescent

[ECG changes in adriamycin therapy].

185 electrocardiograms, of a total of 39 patients were analyzed during and after Adriamycin treatment. Total Adriamycin doses did not exceed 70--120 mg in each course, respecting the 550 mg/m2 limit. ECG changes were found in 80% of such therapeutic regimen, changes of heart-rate, PQ, QT-intervals and ST/T predominating, Arrhythmias (supraventricular and ventricular ectopic beats as well as AV-blocks grade I--II) were observed in several patients.

Adolescent

[A new electrophoretic method for coating metalceramic elements with opaque].

A new, electrophoretical method of coating dental alloys (Au or Ni-Cr) with opaque is described for the first time. The comparison of this method with the known wet brush technique shows that bubbles or voids might occur at the interface between metal and opaque when applying the first ceramic layer manually whereas the electrophoretical one generates a thin and dense layer of porcelain being free of voids within the adherence zone. Those bubbles are considered to be inherent with the brush technique. The author suggests to galvanize dental alloys particularly noble metals in order to suppress any anodic reactions. General advantage for the bond due to galvanization are expected no matter how the opaque was applied.

Dental Bonding

[Casting of dental alloys with special reference to the bonding capacity of Ni-Cr alloys].

A short review on castability of dental alloys -- for which a definition is proposed -- reflects the different factors influencing the results of a casting. In this case solid sieves and plates are cast by use of one gold-base alloy (Type III) and two base metal alloys used for porcelain veneering. All three alloys filled the sieve pattern to a 100%, whereas they performed differently when cast as thin, solid squares. The most continuous results were achieved with a Ni-Cr-alloy whose melting temperature can be recognized since the ingots flow together when this point is reached. Since the plate pattern is most difficult to cast due to surface to bulk ratio it is assumed that a complete casting can only be achieved when the performance of the alloy is good and all required conditions match. Thus, this type of test seems to be suitable to determine the castability of a dental alloy. The sieve test should be used to investigate and to improve the influence of the different factors as for example burnout time and temperature of the mold and sprue size.

Chromium

[Documentation of arrhythmias - the value of long-term ECG monitoring].

Computer-supported long-term ECG-analysis, must be considered as complementary to other methods of documentation concerning arrhythmias. With the introduction of computers in the last several years, exact quantification and qualification of arrhythmias, over long monitoring periods, has become possible. With this method diverse forms of documentation and data presentation enhance its value of information and increase plausibility. Major indications for long-term ECG-monitoring of ambulatory patients are detection of occult arrhythmias, evaluation of subjective symptoms such as dizziness or syncope, recognition of pacemaker dysfunctions, selection of patients with coronary heart disease at high risk and evaluation as well as control of the efficacy of antiarrhythmic therapy.

Arrhythmias, Cardiac

[Arteriomesenteric duodenal compression].

Arteriomesenteric obstruction of the duodenum is a rare lesion seen in abdominal surgery. By vascular compression passage is blocked in the lower part of the duodenum. Two forms are described, an inborn and an acquired one, both of which result from a decrease in the aortomesenterial angle. While the acute form of disease causes a complete occlusion, clinically shown as ileus, the chronic intermittent form presents an uncharacteristic upper abdominal complex of symptoms. The diagnostic procedure is an X-ray passage series of the upper gastrointestinal tract. Final diagnostic assurance should be assumed by angiographical determination of the superior mesenteric artery and its angle of branching from the aorta. Retrocolic duodenojejunostomy has proved to be the most satisfactory surgical treatment for this lesion. Our studies demonstrate the value of surgical treatment of arteriomesenteric obstruction of the duodenum in 14 cases.

Adolescent