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Biomedical subjects

F Fuchs

Publications and source records attributed to F Fuchs.

197 records · Page 11Linked to original sources
PubMed1968

The effect of quinidine on calcium accumulation by isolated sarcoplasmic reticulum of skeletal and cardiac muscle.

Quinidine potentiates twitch tension and (at higher concentrations) causes contracture of skeletal muscle whereas the same drug reduces tension development of cardiac muscle. To gain insight into the possible differences in the excitation-contraction coupling mechanism of the two types of muscle the effect of quinidine on calcium accumulation by isolated sarcoplasmic reticulum from skeletal and cardiac muscle was investigated. In a medium containing ATP, Mg(++), oxalate, and (45)Ca, pharmacologically active concentrations of the drug inhibited calcium accumulation by both skeletal and cardiac sarcoplasmic reticulum. The inhibition of the rates of calcium, uptake by the skeletal muscle preparation ranged from 11% with 10(-4)M quinidine to 90% with 10(-3)M quinidine. With the cardiac muscle preparation the inhibition ranged from 16% with 3 x 10(-6)M quinidine to 100% with 10(-3)M quinidine. With both preparations the inhibition of calcium transport was accompanied by an inhibition of the Ca(++)-activated ATPase activity of the sarcoplasmic reticulum. The effect of quinidine on the skeletal sarcoplasmic reticulum supports the hypothesis that this compound produces twitch potentiation and contracture by interfering with intracellular calcium, sequestration. Its effect on cardiac sarcoplasmic reticulum. has been interpreted in terms of the hypothesis that cardiac contractility is a function of the amount of calcium released from the sarcoplasmic reticulum which is in turn dependent upon the absolute calcium content of the reticulum. Hence, following inhibition of calcium transport there would be less calcium available for coupling.

Adenosine Triphosphatases↗
PubMed1965

Contractility and ultrastructure in glycerol--extracted muscle fibers. I. The relationship of contractility to sarcomere length.

This study was undertaken to determine whether glycerol-extracted rabbit psoas muscle fibers can develop tension and shorten after being stretched to such a length that the primary and secondary filaments no longer overlap. A method was devised to measure the initial sarcomere length and the ATP-induced isotonic shortening in prestretched isolated fibers subjected to a small preload (0.02 to 0.15 P(0)). At all degrees of stretch, the fiber was able to shorten (60 to 75 per cent): to a sarcomere length of 0.7 micro when the initial length was 3.7 micro or less, and to an increasing length of 0.9 to 1.8 micro with increasing initial sarcomere length (3.8 to 4.4 micro). At sarcomere lengths of 3.8 to 4.5 micro, overlap of filaments was lost, as verified by electron microscopy. The variation in sarcomere length within individual fibers has been assessed by both light and electron microscopic measurements. In fibers up to 10 mm in length the stretch was evenly distributed along the fiber, and with sarcomere spacings greater than 4 micro there was only a slight chance of finding sarcomeres with filament overlap. These observations are in apparent contradiction to the assumption that an overlap of A and I filaments is necessary for tension generation and shortening.

Adenosine Triphosphate↗
PubMed1965

Contractility and ultrastructure in glycerol--extracted muscle fibers. II. Ultrastructure in resting and shortened fibers.

Glycerol-extracted rabbit psoas muscle fibers were examined by electron microscopy both before and after ATP-induced isotonic shortening. Ultrastructural changes were correlated with the initial sarcomere length and the degree of shortening. The ultrastructural appearance of the resting fiber at rest length was identical with that described by H. E. Huxley and Hanson. At sarcomere lengths greater than 3.7 to 3.8 micro, the A and I filaments were detached and separated by a gap. The presence of "gap" filaments was confirmed, and evidence is presented which indicates that these filaments form connections between the ends of the A and I filaments. Shortening from initial sarcomere lengths at which the filaments overlapped took place through sliding of the filaments. If shortening was initiated from sarcomere lengths at which there was a gap, a narrowing of the I band was brought about by a curling of the I filaments at the boundary between the A and I bands. No evidence could be found that the I filaments moved into the A band.

Animals↗
PubMedDate not supplied

[cRNA probes (riboprobes) synthesized in vitro for detecting enterovirus by molecular hybridization].

Radioactively labelled RNA transcripts made in vitro of various fragments from cDNA clones of poliovirus type 1 and of hepatitis A virus under the control of bacteriophage T7 or SP6 promoters have been evaluated for diagnostic purposes. The RNA transcripts were 2 orders of magnitude more sensitive as hybridization probes than corresponding cDNA preparations labelled by the nick translation procedure. A combination of hybridization analysis and sequence comparison showed that some regions of the genome of a number of enteroviruses are highly conserved, while others show very little homology; the general order of conservation is: 5'-non-coding greater than 3'-terminal greater than central (2C) greater than VP3 greater than VP1. The 350 bases of the poliovirus VP1 region were highly specific for that virus, while the 450-bases of the 5'NC region showed extensive cross-reaction with other enteroviruses. However, these probes did not hybridize with HAV, which was detected only by HAV-specific riboprobes. The transcripts have been successfully applied as hybridization probes in diagnostic tests on supernatants of infected cell culture lysates and in clinical samples, mainly in stool extracts.

Animals↗
PubMedDate not supplied

[Acute peripheral circulatory disorders with gangrene in infancy].

Two cases of acute venous circulation disorders of the lower extremity are reported. During shock treatment including rehydration and additional application of heparin the circulation disorders were quickly resolved. As etiological factors, difficult delivery due to incomplete breech-footling presentation (case 1) and hypersodium dehydration (case 2) are discussed. Compared with older children infants might have a better prognosis when acute circulation disorders occur.

Acute Disease↗
PubMedDate not supplied

Use of ultraviolet (UV) absorption for control of adsorption processes.

Summarizing all the available experience from different types of investigations, the following conclusions can be made: 1. UV-absorbance has proved useful as a control parameter for granular activated carbon filter performance. It is very easy to measure and very often runs parallel with other more significant but more difficult-to-measure criteria, such as dissolved organic chlorine. 2. Generally speaking, UV-absorbance can be used in those cases where parallel tests using other parameters and analytical methods have shown that the UV data correlate sufficiently well with other more important criteria. This is often, although not always, the case. There may be exceptions, for instance if the removal of pure substances like haloforms in small concentration is crucial for the carbon filter operation. 3. In most cases, carbon filter control can best be done by using a convenient method, such as UV-absorbance, for routine control of the filters and by comparing these data from time to time with the results of other more sophisticated methods. This will allow conclusions from easily obtainable data and will give information in such a short time that special tests could be made in case of unusual values and relationships. In this respect, UV-absorbance measurements can be worthwhile and helpful for carbon filter control.

Adsorption↗
PubMedDate not supplied

[The influence of oxytocin on the production of prostaglandins in vitro and in vivo].

In order to test the hypothesis that oxytocin not only leads to myometrial contractions but also to an increase of prostaglandin synthesis in decidua, human decidua, myometrium and amnion were incubated with and without oxytocin in a modified Krebs-bicarbonate-solution. The addition of oxytocin led to a significant increase of PG E- and PG F-synthesis in decidua and to a significant increase in PG-synthesis in amnion. In 15 women in whom labor was induced by intravenous infusion of oxytocin PGFM concentrations were measured before and during induction. PGFM levels rose in all women in whom induction was successful, whereas they stayed unchanged in those women in whom induction failed. These results support the hypothesis that oxytocin leads to an increase in prostaglandin production through specific receptors in decidua.

Amnion↗