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Biomedical subjects

W Schempp

Publications and source records attributed to W Schempp.

At least 91 records · Page 5Linked to original sources
PubMed1986

An evolutionary conserved early replicating segment on the sex chromosomes of man and the great apes.

Replication studies on prometaphase chromosomes of man, the chimpanzee, the pygmy chimpanzee, the gorilla, and the orangutan reveal great interspecific homologies between the autosomes. The early replicating X chromosomes clearly show a high degree of conservation of both the pattern and the time course of replication. An early replicating segment on the short arm of the X chromosomes of man (Xp22.3) which escapes inactivation can be found on the X chromosomes of the great apes as well. Furthermore, the most early replicating segment on the Y chromosomes of all species tested appears to be homologous to this segment on the X chromosomes. Therefore, these early replicating segments in the great apes may correspond to the pseudoautosomal segment proposed to exist in man. From further cytogenetic characterization of the Y chromosomes it is evident that structural alterations have resulted in an extreme divergence in both the euchromatic and heterochromatic parts. It is assumed, therefore, that, in contrast to the X chromosomes, the Y chromosomes have undergone a rapid evolution within the higher primates.

Animals↗
PubMed1986

Chromosomal homoeologies in hamster species of the genus Phodopus (Rodentia, Cricetinae).

The karyotypes of the two hamster species Phodopus sungorus and P. roborovskii were analyzed with several banding techniques and compared. The homoeologies found between all chromosomes led to the proposal of the most likely common ancestral karyotype of these two species. The differences in the karyotypes were found to be a result of seven independent centric fusions, three inversions, and one possible telomeric fusion, as well as changes in the quantity and DNA-base pair composition of the constitutive heterochromatin.

Animals↗
PubMed1985

A 45,X male with evidence of a translocation of Y euchromatin onto chromosome 15.

A 19-year-old male with azoospermia was found to have a 45,X karyotype with additional euchromatic material on 15p. The parents' karyotypes are normal. The cytogenetic data, the positive H-Y-typing, and the presence of Yp-specific restriction fragments detected in the proband's genome by molecular DNA probes suggest that the short arm of the Y chromosome, including part of the centromere, is translocated onto the nucleolus organizer region (NOR) of chromosome 15.

Adult↗
PubMed1985

Chromosome banding in Amphibia. IX. The polyploid karyotypes of Odontophrynus americanus and Ceratophrys ornata (Anura, Leptodactylidae).

The somatic and meiotic chromosomes of the South American leptodactylid toads Odontophrynus americanus, Ceratophyrys ornata, and C. cranwelli were analysed both with conventional staining and differential banding techniques. The karyotypes of O. americanus were tetraploid; those of C. ornata octaploid. Ceratophrys cranwelli is a diploid species whose karyotype displays great similarities with that of C. ornata. The high frequency of multivalent pairing configurations in the meioses of O. americanus and C. ornata indicate that these animals were of autopolyploid origin. The conventionally stained somatic chromosomes of O. americanus can be arranged into sets of four similar chromosomes (quartets); those of C. ornata, into sets of eight similar chromosomes (octets). The banding patterns revealed heterogeneity within some quartets of O. americanus, dividing each of them into two pairs of homologous chromosomes. In analogy, some octets of C. ornata can be subdivided into two quartets of chromosomes with homologous bands. These structural heterogeneities within the quartets and octets are interpreted as a "diploidization" of the polyploid karyotypes. Diploidization leads to genomes that are polyploid with respect to the amount of genetic material and diploid with respect to chromosomal characteristics and the level of gene expression. In tetraploid O. americanus, the number of nucleolus organizer regions (NORs) and their DNA content is proportional to the degree of ploidy. In contrast, up to eight NORs have been deleted in the octoploid C. ornata. These NOR losses are discussed as a possible reason for the reduction of genetic activity in polyploid genomes.

Animals↗
PubMed1985

[Familial, structural aberration of the Y chromosome with fertility disorders].

Cytogenetic studies on a patient with Klinefelter's syndrome revealed an inherited, structural aberration of the Y-chromosome which has not been described before. The aberrant Y-chromosome was characterized by eight different banding methods. The value of individual staining techniques in studies on Y-heterochromatin aberrations is emphasized. Analysis of the cytogenetic studies (banding methods, restriction endonuclease of DNA, and measurement of the length of the Y-chromosome) permits an interpretation to be made on how the aberrant Y-chromosome originated. The functions of the Y-chromosome are discussed. The decrease in fertility (cryptozoospermia) in the two brothers with the same aberrant Y-chromosome was striking.

Adolescent↗
PubMed1984

Satellited Y chromosomes: structure, origin, and clinical significance.

Three cases of inherited satellited Y chromosomes (Yqs) were analysed using several cytogenetic techniques. The cytogenetic data of the 14 cases of Yqs chromosomes described to date were reviewed. All Yqs chromosomes carry an active nucleolus organizer region (NOR) in their long arm and must have developed from translocations involving the short arms of the acrocentric autosomes. The structure of the heterochromatic satellite region in the Yqs chromosomes shows conspicuous inter-familial differences; this permits the reconstruction of the translocations from which the various Yqs were derived. Some causal factors leading to the development of Yqs chromosomes are considered: the specific localization of the four satellite DNAs and highly methylated DNA sequences in the karyotype, and some new experimental data on the spatial arrangement of heterochromatic regions in interphase nuclei. These provide distinct evidence for a preferential involvement of the autosomes 15 and 22 in the translocations with the Y heterochromatin. All clinical reports documenting Yqs males born with malformations were reviewed. It appears that the presence of an extra NOR and NOR-associated heterochromatin in the Yqs chromosomes does not cause any phenotypic abnormalities (as long as the Y euchromatin is intact). The possibility that a Yqs chromosome predisposes to non-disjunction and/or to translocations of other chromosomes is discussed.

Adolescent↗
PubMed1983

Cytologic evidence for three human X-chromosomal segments escaping inactivation.

Early replication of prometaphasic human sex chromosomes was studied with the bromodeoxyuridine (BrdU)-replication technique. The studies reveal that two distal segments of Xp, including bands Xp 22.13 and Xp 22.3, replicate early in S-phase and therefore may not be subject to random inactivation. Furthermore, the replication of these distal segments of Xp occurs synchronously with those of the short arm of the Y chromosome including bands Yp 11.2 and Yp 11.32. These segments of Xp and Yp correspond well to the pairing segment of the X and Y chromosomes where a synaptonemal complex forms at early pachytene of human spermatogenesis. The homologous early replication of Yp and the distal portion of Xp may be interpreted as a remnant left untouched by the differentiation of heteromorphic sex chromosomes from originally homomorphic autosomes. A third early replicating segment is situated on the long arm of the X chromosome and corresponds to band Xq 13.1. This segment may be correlated with the X-inactivation center postulated by Therman et al. (1979).

Bromodeoxyuridine↗
PubMed1983

Cytogenetic studies in couples with multiple spontaneous abortions.

Chromosome studies were performed on a series of 117 couples referred for genetic counseling following two or more spontaneous abortions. Of the 222 individuals karyotyped, in five cases a chromosomal aberration was found. Four cases had a balanced translocation, and one revealed to be a 46,XX/45, X mosaic.

Abortion, Habitual↗
PubMed1982

High resolution replication patterns of the human Y chromosome. Intra- and interindividual variation.

Replication studies on prophasic human Y chromosomes reveal 4 early replicating segments in the euchromatic portion. The distal segment of Yp replicates first. After replication of the euchromatic part is almost finished 3 to 5 segments start replication in the heterochromatic portion of Yq. These segments exhibit considerable intraindividual variation with respect to the origin of onset of replication. While the location of these bands--once they are differentiated--is fixed within one individual, the number of these bands varies interindividually.

Cells, Cultured↗
PubMed1982

Homologous early replication patterns of the distal short arms of prometaphasic X and Y chromosomes.

Replication studies on prometaphasic human sex chromosomes reveal a distinct early replicating segment on both distal Xp ad Yp. These segments correspond to high resolution bands Xp22.3 and Yp11.3. The findings demonstrate synchronous replication of these parts of the sex chromosomes and correspond to the comparatively long stretches of Xp and Yp that participate in a synaptonemal complex. Furthermore these observations are compatible with Polani's view that suggests homologous segments with similar genetic information on both sex chromosomes (Polani 1982).

Chromosome Banding↗
PubMed1982

Comparative analysis of karyotypes in European shrew species. II. Constitutive heterochromatin, replication patterns, and sister chromatid exchanges in Sorex araneus and S. gemellus.

The chromosomes of the two closely related species Sorex araneus and S. gemellus were investigated by various methods for the determination of constitutive heterochromatin (C-band techniques, treatment of cell cultures with AT- and GC-base-pair-specific compounds, and analysis of late-replication patterns). With the exception of the Y1 sex chromosomes, no distinct heterochromatic regions like those in other mammals were demonstrated. Although use of a modified C-band technique produced moderately darkly stained bands, these did not have a definite heterochromatic character. Spontaneous sister chromatid exchanges (SCE's) occurred significantly more frequently in the Y1 chromosomes than in other chromosomes. Analysis of intrachromosomal frequencies of SCE's showed no significant deviations from a uniform random distribution.

Animals↗
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

Chromosome banding in Amphibia. VI. BrdU-replication patterns in anura and demonstration of XX/XY sex chromosomes in Rana esculenta.

A modified BrdU-Hoechst-Giemsa technique permitted the demonstration of easily reproducible replication patterns in the somatic chromosomes of Amphibia. These banding patterns allow for the first time a precise identification of all chromosomes and the analysis of the patterns of replication in the various stages of S-phase in Amphibia. Several possibilities for the use of this technique were demonstrated on three frog species of the family Ranidae, all differing greatly in their DNA-content. With this method, the homomorphic chromosome pair No. 4 in Rana esculenta could be identified as sex-specific chromosomes of the XX/XY-type. All male animals exhibit an extremely late replicating region in the Y-chromosome, which is lacking in the X-chromosome in the female animals, both X-chromosomes replicate synchronously. These sex-specific chromosomes cannot be distinguished by other banding techniques. In the highly heteromorphic ZZ/ZW-sex chromosome system of Pyxicephalus adspersus a synchronous replication of the two Z-chromosomes of male animals and a very late replication of the short arm of the W-chromosomes of male animals was demonstrated. These results support the assumption that there is no dosage compensation for Z-linked or X-linked genes by the sex chromosome inactivation mechanism in the sex chromosomes of Amphibia.

Animals↗
PubMed1980

Asynchrony in late replication between homologous autosomes in primary cultures of Chinese hamster fibroblasts.

Asynchronies in late replication of the autosomal chromosome pair No. 5, and to some extent of pair No. 4, were found after thymidine pulse labeling cultures of partially synchronized Chinese hamster lung fibroblasts from nine to nine and a half hours and from nine and a half to ten hours after block removal. In contrast to this, no asynchrony could be detected in the replication of homologous autosomes after continuous labeling for the last two hours of the S-phase. - G-banding and C-banding revealed no differences between the homologous autosomes. - These findings indicate that besides the known form of asynchronous replication in mammalian cells during S-phase on the chromosomal level, there also exists an asynchronous replication between homologous autosomes of the same complement.

Animals↗
PubMed1979

Difference between diploid and aneuploid Chinese hamster cells in replication at mid-S-phase.

Following partial synchronization of the heteroploid Chinese hamster cell line V-79 and of normal diploid lung fibroblasts of the Chinese hamster in culture, their DNA replication during S-phase aws compared by means of a BrdU-incorporation/thymidine pulse technique and Hoechst-Giemsa differential staining of metaphase chromosomes. This comparison indirectly shows the S-phase of the heteroploid cells of V-79 to be 2 h shorter than the diploid cell S-phase. When the thymidine pulse is applied to diploid lung fibroblasts at mid-S-phase, differential staining colours metaphase chromosomes a pale blue. Performing the corresponding experiment with V-79 cells, neither a pale blue nor dark red staining is obtained, but rather an intermediate shade, showing prominently dark staining regions in parts. The pause in DNA synthesis observed at mid-S-phase of the diploid Chinese hamster lung fibroblasts seems to be omitted at mid-S-phase of the V-79 cells.

Aneuploidy↗