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J Schmidtke

Publications and source records attributed to J Schmidtke.

At least 163 records · Page 9Linked to original sources
PubMed1982

Patterns of cyclic AMP phosphodiesterases in the rat pineal gland: sex differences in diurnal rhythmicity.

Rat pineal cyclic AMP (cAMP) phosphodiesterases (PDEs) were studied during male development and in adult females by means of gel electrophoresis, kinetic analysis, and diurnal activity measurements. In both male and female rats, two molecular forms of PDE coexisted. In neonatal-infantile males (birth to day 20 of age) a third isozyme was detected. The kinetic properties of PDEs were essentially similar in infantile and adult male rats with respect to the Kms; however, a minimal Vmax was observed at 10.00 a.m. in adults, but not in neonatal animals. PDE activity in male rats was maximal between 2.00 a.m. and 4.00 a.m., and also at 4.00 p.m., and was minimal at 10.00 a.m. This pattern appeared to develop during the infantile period of life. The pattern of activity observed in adult female rats was similar to that of adult males, except that it lacked a pronounced afternoon peak. The diurnal PDE activity profile of castrated male adult rats was similar to female adults and testosterone substitution in male castrated rats resulted in a pattern which resembled that of adult male controls. In addition to the above measurements, testosterone serum levels have been determined during all of these experiments.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1981

Characterization of a new aberration of the human Y chromosome by banding methods and DNA restriction endonuclease analysis.

Comparative cytogenetic analyses were performed with ten different banding methods on a previously undescribed, inherited structural aberration of a Y chromosome, and the results compared with those of normal Y chromosomes occurring in the same family. The value of the individual staining techniques in investigations of Y chromosomal aberrations is emphasized. The aberrant Y chromosome analyzed can be formally derived from an isodicentric Y chromosome for the short arm with a very terminal long-arm breakpoint, in which the centromere, an entire short arm, and the proximal region on one long arm was lost. This interpretation was confirmed by determining the amount of the two Y-specific DNA sequences (2.1 and 3.4 kb in length) by means of Hae III restriction endonuclease analysis. The karyotype-phenotype correlations in the men with this aberrant Y chromosome, especially the fertility dysfunctions (oligoasthenoteratozoospermia, cryptozoospermia), are discussed. The possibility of the existence of fertility factors involved in the control of spermatogenesis within the quinacrine-bright heterochromatic region of the Y long arm is presented.

Adult↗
PubMed1981

Single-copy DNA relationships between diploid and tetraploid teleostean fish species.

The degree of single-copy DNA relatedness among nine Salmonid, Osmerid, and Clupeid species (teleosts, order Isospondyli) was explored by interspecific DNA hybridization and the determination of the thermal stability of these hybrids. It is shown that the extent of base substitution and the amount of shared sequences is largely consistent with the systematic interrelationship of the species compared. A tentative estimate of the average base substitution rate is about 0.1-0.25% per million years, which is in the range typical for animal and plant nuclear genomes. The results are also discussed in view of the phylogenetically tetraploid state of the Salmonid genomes. A comparison of the amount of intra-genomic and inter-genomic divergence in the tetraploids suggests that a polyploidization event occurred recently in Salmonid evolution.

Animals↗
PubMed1981

Evolution of muntjac DNA.

The extent of nuclear single-copy DNA divergence between Muntiacus reevesi and Muntiacus muntjak vaginalis (Cervidae), a species pair showing extreme karyotype differences but striking morphological similarity, is 2%, as judged from the thermal stability of interspecific DNA-DNA hybrids. A comparison of the total nuclear DNA reassociation kinetics of the two species indicates a reduction of lowly repetitive sequences in M. m. vaginalis.

Animals↗
PubMed1981

Cyclic AMP phosphodiesterase in Leydig cell preparations of the rat testis.

Enzymatic digestion of the interstitial tissue of early juvenile and adult rat testes resulted in an enrichment of the Leydig cell population. The cells of the intertubular preparation from adult testes were separated by centrifugal elutriation, according to differences in sedimentation velocity, a counter-flow centrifugation technique leading to 70% Leydig cell purity. Using this approach, it was possible to demonstrate that Leydig cells from adult testes contain only low affinity isoenzymes of cyclic AMP phosphodiesterase (PDE; E.C.: 3.1.4.17), an intracellular regulator of cAMP. Starch gel electrophoresis showed that the isozyme of cAMP PDe of Leydig cells is masked in crude testis homogenates due to the relatively low level of these cells in the total population. In Leydig cells, there are two different electrophoretic forms expressed which resemble two of eleven different molecular forms of cAMP PDE demonstrated for comparison in 21 different organs of the adult rat. An interstitial cell preparation from early juvenile testes, with a Leydig cell content of up to 20%, was also investigated electrophoretically with regard to molecular forms of cAMP PDE, the properties of which were characterized by kinetics analysis of cAMP hydrolysis. The results presented are discussed in relation to the onset of testosterone synthesis in Leydig cells of prepubertal rats leading to the initiation of male puberty.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1980

Patterns of cyclic AMP phosphodiesterases during rat testis development.

Cyclic AMP phosphodiesterase (PDE; E.C.: 3.1.4.17) plays a crucial role in the regulation of intracellular cAMP levels arising from the hormonal activation of membrane-bound adenylcyclase in the target cell. In the present study, we revealed a complex sequence of appearance and disappearance of individual molecular electrophoretic forms of PDE during the development of the rat testis. Kinetic analysis of cAMP hydrolysis in crude testis homogenates of developmental stages where multiple PDE isozymes are expressed revealed complex kinetic behavior of PDE. After separation of individual isozymes by elution from starch gel blocks, several enzymatic forms still act with complex kinetics, indicating negatively cooperative behavior. The stage specificity of the kinetic properties of PDE appears to be related to the hormonally regulated events leading to the initiation of male puberty.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1980

Sequence organization of animal nuclear DNA.

Animal nuclear genomes contain DNA sequences of various degrees of repetition. These sequences are organized in highly ordered fashions; repetitive and nonrepetitive sequences either alternate in short periods, i.e., short [0.2-0.4 kilobases (kb) long] repeats are flanked by nonrepetitive sequences less than 2 kb long, or in longer periods, with repetitive and/or nonrepetitive sequences extending for several kilobases. There are two main categories of genome organization, namely those exhibiting short-period interspersion and those that do not. There are arguments for and against a regulatory role of short interspersed repetitive sequences. Besides the merely 'statistical' kinetic approach by conventional reassociation kinetics, sequence organization has been studied by restriction endonuclease mapping and nucleotide sequencing. Such studies have revealed some general features of the organization of the eukaryotic gene and its transcripts, namely possible 'promoters', 'leaders', 'introns', 'exons', 'flanking sequences', 'caps', ribosome-binding sites, and poly(A) sequences. This paper discusses how these elements of a gene might serve regulatory roles in its expression.

Animals↗
PubMed1980

Gene diversity in tunicate populations.

Populations of the tunicate species Ciona intestinalis and Ascidiella aspersa were screened for electrophoretic polymorphism at various enzyme loci. Average heterozygosities are clearly related to population size as predicted by the neutral mutation hypothesis.

Alleles↗
PubMed1980

Cyclic AMP phosphodiesterases of the rat ovary. Oestrous cycle dependent activity change of high affinity form.

In the rat ovary, from prenatal to adult stages, two electrophoretically distinct forms of cyclic AMP phosphodiesterase (E.C.: 3.1.4.17) occur. These forms were analysed for their affinity towards cAMP in both crude and partially purified preparations. Whereas the slow electrophoretic form, which has a low affinity towards cAMP, shows a linear Lineweaver-Burk plot, the fast electromorph exhibits anomalous kinetic behaviour in that cAMP affinity appears to increase with decreasing cAMP-concentration. This form shows dramatic alteration of maximum velocity during the oestrous cycle, attaining maximum activity at metoestrus. This rise of activity is sensitive to inhibition of protein synthesis.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1979

Non-repetitive DNA sequence divergence in phylogenetically diploid and tetraploid teleostean species of the family cyprinidae and the order isospondyli.

Non-repetitive DNA of anciently tetraploid teleostean species was analysed for the presence of duplicated sequences. Closely related diploid species were investigated in comparison. From the reassociation kinetics of total nuclear DNA, rate constants and fraction sizes of classes of repetitive and non-repetitive sequences were determined. DNA fractions enriched in the slowest renaturing sequence class were determined. DNA fractions enriched in the slowest renaturing sequence class were prepared and subjected to reassociation. The rate constants of these reactions were compared with the values expected for single-copy DNA from analytical genome size determinations. From reassociated DNA enriched in non-repetitive sequences also the melting temperatures were determined as a measure of internal base sequence heterogeneity. It has been shown that the two ancient tetraploids Cyprinus carpio and Thymallus thymallus are, with regard to the thermal stability of reassociated non-repetitive DNA, and with regard to the correspondence of reaction rates with the values expected for single copy DNA, indistinguishable from diploid controls (Rutilus rutilus, Clupea harengus and Sprattus sprattus). The tetraploid species Salmo irideus, Salvelinus fontinalis and Coregonus lavaretus appear as very recent tetraploids with regard to these criteria. The significance of the results for estimating the time of occurrence of polyploidisation events in these taxa is discussed.

Animals↗
PubMed1979

Contrasting DNA sequence organisation patterns in sauropsidian genomes.

The genomic DNA organisation patterns of four sauropsidian species, namely Python reticularis, Caiman crocodilus, Terrapene carolina triungius and Columba livia domestica were investigated by reassociation of short and long DNA fragments, by hyperchromicity measurements of reannealed fragments and by length estimations of S1-nuclease resistant repetitive duplexes. While the genomic DNA of the three reptilian species shows a short period interspersion pattern, the genome of the avian species is organised in a long period interspersion pattern apparently typical for birds. These findings are discussed in view of the close phylogenetic relationships of birds and reptiles, and also with regard to a possible relationship between the extent of sequence interspersion and genome size.

Alligators and Crocodiles↗
PubMed1979

Genome analysis of Amphioxus and speculation as to the origin of contrasting vertebrate genome organization patterns.

1. The genome of Amphioxus was investigated by DNA reassociation techniques for the amount of repetitive and non-repetitive sequences and its pattern of organization. 2. A comparison of the amount of non-repetitive DNA between Amphioxus and the tunicate Ciona intestinalis does not support the hypothesis that the Cephalochordates have arisen from the Tunicates by polyploidy. 3. In the Amphioxus genome repetitive and non-repetitive elements are predominantly arranged in a short period interspersion pattern. Conclusions are presented as to the evolution of contrasting genome organization patterns among vertebrates.

Animals↗
PubMed1979

Amount of repeated and non-repeated DNA in the genomes of closely related fish species with varying genome sizes.

1. Within the teleostean family Cyprinidae, diploid species occur with wide variation in genome size. There also exist species which were anciently tetraploid. 2. The quantitative changes of DNA content in the diploids are primarily due to differences in the amount of intermediately repeated DNA. DNA sequence composition of the ancient tetraploid genomes suggests that the species derived from diploid ancestors of small genome size. 3. The average base composition and the base compositional heterogeneity are similar in all the species examined.

Animals↗
PubMed1978

DNA sequence organisation in avian genomes.

By means of renaturation kinetics of DNA of the three avian species Cairina domestica, Gallus domesticus and Columba livia domestica the following major DNA repetition classes were observed: a very fast reannealing fraction comprising about 15% of the DNA, a fast or intermediate reannealing fraction that makes up 10%, and a slow reannealing fraction of about 70%, which apparently renatures with single copy properties. --Comparing the reassociation behaviour of short (0.3 kb) and long (greater than 2 kb) DNA fragments of duck and chicken it becomes apparent that only 12% (duck) and 28% (chicken) of the single copy DNA are interspersed with repetitive elements on 2 to 3 kb long fragments. The lengths of the repetitive sequences were estimated by optical hyperchromicity measurements, by agarose A-50 chromatography of S1 nuclease resistant duplexes and by electron microscopic measurements of the S1 nuclease resistant duplexes. It was found that in the case of the chicken DNA the single copy sequences alternating with middle repetitive ones are at least 2.3 kb long; the interspersed moderate repeats have a length average of at least 1.5 kb. The sequence length of the moderate repeats in duck DNA is smaller. The results show that the duck and the chicken genomes do not follow the short period interspersion pattern of genome organisation, characteristic of the eucaryotic organisms studied so far.

Animals↗