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Biomedical subjects

K Wolf

Publications and source records attributed to K Wolf.

At least 217 records · Page 12Linked to original sources
PubMed1978

Circular molecules of heterogeneous size from mitochondrial fractions of the petite-negative yeast Schizosaccharomyces pombe.

Size and shape of mitochondrial DNA molecules of Schizosaccharomyces pombe were analyzed by electron microscopy. Besides numerous linear molecules, circular molecules ranging from 0.83 micron to 12.81 micron were found. Depending on the method of preparation, both closed and open circular molecules were found. Most of the circular molecules could be assigned to five major size classes of 0.83 +/- 0.05 micron, 1.7 +/- 0.05 micron, 4.74 +/- 0.04 micron, 5.74 +/- 0.04 micron, and 8.32 +/- 0.07 micron. Possible explanations for the different size classes of mitochondrial DNA molecules are discussed.

Ascomycota↗
PubMed1978

Extrachromosomal inheritance in Schizosaccharomyces pombe. VII. Studies by zygote clone analysis on transmission, segregation, recombination, and uniparental inheritance of mitochondrial markers conferring resistance to antimycin, chloramphenicol, and erythromycin.

Crosses involving mitochondrial markers conferring resistance to antimycin (anar, AR), chloramphenicol (capr, CR), and erythromycin (eryr, ER) in cis- and trans-configuration were studied by zygote clone analysis. Mutant anar-8, from which all other drug--resistant isolates were derived, exhibits a highly biased transmission (6.8% anar) in an analysis of 100 individual zygote clones. Important results of zygote clone analyses were:--Zygote clones may contain one, two, three, or four mitochondrial genotypes.--The proportion of the two parental and the two recombinant genotypes in individual zygote clones can vary almost over the entire range of percentages.--Proportions of the two corresponding recombinant types in individual clones are usually unequal.--Transmission rates of markers are higher in trans- than in cis-crosses, indicating additivity of bias by two mutated alleles in coupling.--Transmission rates are different for the three markers both in cis- and trans-crosses, being lowest for CR and highest for ER.--Up to more than 80% uniform clones, expressing only one genotype, can be produced in cis- and trans-crosses. In cis-crosses always the double-sensitive parental type becomes uniform, in trans-crosses this may be the case for parental and/or recombinant genotypes. A tentative map is presented using data from cis- and trans-crosses, including a correction by omission of uniform clones. Phenomena of transmission, segregation, and formation of uniform clones are discussed with special regard to the difference brought about by fission versus budding. A comparison with relevant data from Saccharomyces cerevisiae and other organisms is presented.

Anti-Bacterial Agents↗
PubMed1978

Herpesvirus salmonis: Characterization of a New Pathogen of Rainbow Trout.

A new agent, provisionally designated Herpesvirus salmonis, was isolated from post-spawning rainbow trout (Salmo gairdneri) and studied primarily in the RTG-2 rainbow trout cell line. Infection of RTG-2 cells resulted in the formation of syncytia and Cowdry type A intranuclear inclusions. Replication occurred regularly at 5 and 10 degrees C, but was inconsistent at 15 degrees C, largely inhibited at 0 degrees C, and completely inhibited at 20 degrees C or higher. The virus was acid, heat, ether, and chloroform labile, but stable to freezing and thawing. It did not hemagglutinate. Viral DNA had a buoyant density of 1.709 g/cm(3) and a guanine-cytosine value of 50%. Hexagonal nucleocapsids had a diameter of 90 nm and were first seen in nuclei at 36 h. Enveloped forms measured about 150 nm and occurred both cytoplasmically and extracellularly. At 10 degrees C, a one-step growth culture required about 96 h; cell-associated virus peaked at about 10(5) PFU/ml and exceeded released virus by a factor of about 10.

Journal Article↗
PubMed1978

The effect of verapamil, isoproterenol, and dexamethasone on enzyme release and viability of coronary obstructed guinea-pig hearts.

In isolated perfused guinea-pig hearts decrease of coronary flow, release of creatine kinase (CK), severe arrhythmias and early standstill were produced by intracoronary application of plastic microspheres. 1 X 10(-9) g verapamil/ml perfusion fluid significantly decreased the CK release from these "ischemic" hearts. With 1 X 10(-8) g/ml a significant increase of the survival times was obtained. Dexamethasone strongly depressed the enzyme release from the coronary obstructed hearts. The survival times, however, were not prolonged. Isoproterenol significantly shortened the survival times. Very low concentrations decreased the CK release, whereas higher concentrations themselves provoked an enzyme release.

Animals↗
PubMed1977

Extrachromosomal inheritance in Schizosaccharomyces pombe. IV. Isolation and genetic characterization of mutants resistant to chloramphenicol and erythromycin using the mutator properties of mutant anar-8.

Spontaneous chloramphenicol (capr)- and erythromycin (eryr)-resistant mutants were isolated from strain ade7-50 h- and the antimycin-resistant mutant anar-8 ade 7-50 h- of Schizosaccharomyces pombe (Sch. p.). By mitotic segregation analysis all 154 capr- and 120 eryr-mutants derived from ade 7-50 h- proved to be recessive chromosomal, whereas all 108 capr- and 200 eryr-mutants originating from anar-8 were extrachromosomally inherited. The rate of spontaneous capr- and eryr-mutants was about hundredfold in anar-8 compared to ade 7-50 h-. Growth of capr- and eryr-mutants was not inhibited by chloramphenicol or erythromycin, respectively, in glucose-medium and only slightly in glycerol-medium at concentrations which completely inhibited anar-8. By mitotic segregation-, tetrad-, and mitotic haploidization-analysis the extrachromosomal inheritance of mutants derived from anar-8 was established. Segregational patterns of capr- and eryr-determinants during mitosis, meiosis, and mitotic haploidization of diploids are discussed.

Ascomycota↗
PubMed1977

Extrachromosomal inheritance in Schizosaccharomyces pombe. III. Isolation and characterization of paromomycin-resistant mutants.

In the antimycin--resistant mutant anar-8 of the fission yeast Schizosaccharomyces pombe (Sch.p.) spontaneous mutants were isolated showing high resistance to the aminoglycoside antibiotic paromomycin. All mutants were resistant to the structurally related antibiotic neomycin. Tetrad analysis, mitotic segregation analysis, and mitotic haploidization revealed extrachromosomal, very likely mitochondrial inheritance. In contrast to the rapid segregation of mitochondrial markers in zygotic clones of Saccharomyces cerevisiae (S.c.) the heteroplasmic state of diploids proved to persist for at least 50 generations after zygote formation. Stationary cultures of the paromomycin-resistant mutants parr-106 and parr-112 contain up to 6% respiratory-deficient mutants, but no reversion to paromomycin-sensitivity was observed among 1700-1800 colonies tested. The ability of mutant anar-8 to produce spontaneously respiratory-deficient mutants could be separated from the antimycin-resistant phenotype of anar-8.

Ascomycota↗
PubMed1977

The acoustic reflex and temporary threshold shift: temporal characteristics.

One ear of each of seven normal-hearing subjects was exposed to a continuous 1000-Hz tone at 110 dB SPL for three minutes. During exposure, a broad-band noise at 100 dB SPL was presented to the contralateral ear. The noise was either continuous or pulsed. Four pulsed conditions employed repetition periods of 360, 180, 90, or 9 msec with a 50% duty cycle. A control condition in which no noise was presented was also included. Temporary threshold shift was measured at selected postexposure times at the frequency one-half octave above the exposure frequency. TTS2 was greatest for the control condition and least for the 360- and 180-msec conditions. Results are discussed in relation to the dynamics of the acoustic reflex, particularly reflex relaxation, reflex adaptation, and reflex temporal summation.

Acoustic Stimulation↗
PubMed1976

Effect of caffeine on the rho- -induction with ethidium bromide in Saccharomyces cerevisiae.

It is shown that caffeine antagonizes petite-induction with ethidium bromide under non-growth conditions when administered during or after mutagenic treatment. Caffeine itself is shown to be a petite-inducing agent when cells are grown in liquid glucose-complete-medium in the presence of the drug. A possible mode of action of caffeine in the ethidium bromide induced petite-mutagenesis is discussed.

Caffeine↗
PubMed1976

Extrachromosomal inheritance in Schizosaccharomyces pombe. I. Evidence for an extrakaryotically inherited mutation conferring resistance to antimycin.

In crosses of [ANTr8] with auxotrophic strains, resistance to antimycin segregates almost 50:50 in random spore analysis with a slight preponderance for the sensitivity allele. Tetrad analysis, however, shows all possible types of tetrads (2:2; 3:1; 1:3; 4:0; 0:4 resistant versus sensitive) with an excess of 2:2 segregations and sectoring of colonies on antimycin medium indicating an extrachromosomal mode of inheritance. The overall ratio of resistant versus sensitive spores is the same as compared with random spore data. Using a mutant blocked in meiosis (mei 1) mitotic segregation of stable diploids is achieved, leading to a ratio of 20% resistant to 80% sensitive clones. Possible reasons for the bias in transmission of the resistance determinant is discussed.

Antimycin A↗
PubMed1976

Extrachromosomal inheritance in Schizosaccharomyces pombe. II. Evidence for extrakaryotically inherited respiratory deficient mutants.

In contrast to the wild-type, mutant [ANTr8] is able spontaneously to throw off stable respiratory deficient mutants. The frequency of these mutants is considerably enhanced by treatment with ethidium bromide (EB) or the azo-dye Janus green (JG). An unstable cell state with a petite-like phenotype is found in both mutant [ANTr8] and wild-type after EB-treatment. However, only in the mutant is this unstable cell state followed by the appearance of stable respiratory deficient (RD) mutants. Formation of microcolonies is observed both in [ANTr8] and wild-type. RD mutants were isolated after EB treatment. Three of them (mit-12, mit-25, and mit-30) were analyzed and mit-25 characterized in more detail.

Ascomycota↗
PubMed1975

Fish health--some concepts, constraints, and comparisons.

This has been an overview of fish health, a comparison of some aspects of fish husbandry with other animal husbandry, and comments concerning fish health research--especially where it is going. The 1972 disease survey identified current problems; it ranked the problems according to priority. More important, research effort has been redirected. Problems of highest priority are receiving the greatest attention; those of lesser priority are receiving the appropriately lesser attention. Just as veterinary and human medical research have become more mission-oriented, fish health research has also become much more of a problem-solving activity. There are fewer dollars; they must be used wisely and they must produce. Research in fish health is expected to yield usable information that will be of significant help in producing better fishes. If destined for the table, such fishes should convert feeds rapidly and efficiently, and they should not suffer losses from diseases. If intended for stocking, such fishes should be capable of thriving in the environment and of surviving to fulfill their destiny.

Animal Husbandry↗
PubMed1975

Studies on the mechanism of electron trasport in the bc1-segment of the respiratory chain in yeast. III. Isolation and characterization of an antimycin resistant mutant ANT 8 in Schizosaccharomyces pombe.

1. A mutant (ANT 8) of Schizosaccharomyces pombe which shows resistance to antimycin both in vivo and in vitro is characterized biochemically and genetically. 2. In crosses of ANT 8 with auxotrophic strains, resistance to antimycin segregates 2:2 indicating that resistance is conferred by a single nuclear gene. Diploids heterozygous for the resistance gene, however, show segregation of the resistance and sensitivity during mitosis. Possible reasons for this segregation are discussed. 3. Compared with the wild type, the NADH oxidase of ANT 8 requires 13 times as much antimycin for 95% inhibition. After addition of ubiquinone-3, electron transport which is less sensitive to antimycin is found only in the mutant. 4. The resistance of the mutant ANT 8 si due to the much weaker binding of antimycin to mitochondria. As in the wild type, two antimycin binding sites can be separated by binding studies. From the inhibition curves it is evident that binding of antimycin to oxidized mitochondrial particles does not correspond with its inhibitory effect on the partly reduced enzyme in kinetic studies. 5. The peak of the b-cytochrome absorbing at 560.2 nm at 77 degrees K in the wild type is shifted to 561 nm in the mutant. 6. A special preparation method for mutant mitochondrial particles is described, yielding highly active enzymes and CO-insensitive cytochromes. 7. The results are discussed with reference to the components in our model of the respiratory chain, which may be responsible for this type of resistance.

Antimycin A↗