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Biomedical subjects

I Hansmann

Publications and source records attributed to I Hansmann.

At least 109 records · Page 6Linked to original sources
PubMed1979

Fanconi's anaemia developing erythroleukaemia.

A 15-year-old boy with Fanconi's anaemia (FA) for 10 years developed acute erythroleukaemia. During the leukaemic phase, granulopoietic stem cells (CFUc) were absent from his bone marrow and blood, but proliferation and differentiation of bone marrow cells could be seen in semipermeable diffusion chambers in vivo, and globin synthesis of erythroblasts had become imbalanced. Chromosomal lesions of peripheral blood lymphocytes differed in the leukaemic phase from those in the pancytopenic phase. These data indicate that erythro-, myelo-, thrombo-, and lymphocytic cell lines all were involved in both the leukaemic and the pancytopenic process. It is suggested that terminal myeloproliferative disease developed as part of the natural history of FA.

Adolescent↗
PubMed1979

Chromosomal imbalance in ovulated oocytes from Syrian hamsters (Mesocricetus auratus) and Chinese hamsters (Cricetulus griseus).

Chromosomes were studied in ovulated oocytes from Syrian hamsters (Mesocricetus auratus) and Chinese hamster (Cricetulus griseus) to assess the degree of chromosomal imbalance after first meiotic division of oogenesis. Only one hyperploid oocyte among 307 studied was detected in the former, and none in oocytes from the latter species. Structural chromosome alterations, single chromatids due to presegregation, and diploid chromosome sets resulting from meiotic blockage were not observed. The hormones which were used to stimulate ovulation apparently did not enhance first meiotic cleavage errors in these hamster oocytes. The low figures of chromosomal anomalies in hamster oocytes are compared to those from a large sample of mouse oocytes obtained from three different strains and prepared under identical conditions. The relevance of these findings to the obviously higher impact of chromosomal aneuploidy in man is discussed.

Aneuploidy↗
PubMed1979

Incidence of nondisjunction in mouse oocytes.

The chromosomes of more than 3000 ovulated mouse oocytes from strains C3H/Han, NMRI/Han, and (101 X C3H)F1 have been analyzed after spontaneous and hormonally induced ovulation. No significant difference in the incidence of nondisjunction was observed among the three strains with or without hormonal pretreatment. The incidence of nondisjunction was estimated to be 0.47% in NMRI/Han, 0.62% in C3H/Han, and 0.81% in (101 X C3H/F1. The incidence of chromosomal imbalance after the first meiotic division was slightly higher after adding the events following presegregation. Diploidy-spontaneous and hormonally induced-reached a significant leve in NMRI/Han. This may be interpreted as a consequence of hormonal interference with a genetically defined malfunction of gene product(s) during the late phase of oogenesis.

Animals↗
PubMed1979

Detection of nondisjunction in mammals.

Methods have been developed in the past to assess spontaneous and induced chromosomal aneuploidy in germ cells and in early pre- and postimplantation mammalian embryos. Some of these methods yield still more information when combined with chromosome banding techniques. Various chemicals and x-rays have been tested in mammalian oogenesis and x-rays in spermatogenesis. The inference may be drawn from these studies that spontaneous nondisjunction is considered to occur only rarely in mouse and hamster oogenesis and spermatogenesis. X-rays induce nondisjunction during male and femlae meiosis, thus giving rise to significantly more aneuploid oocytes and F1 embryos. The alkylating agents trenimone and cyclophosphamide induce chromosomal missegregation in oocytes; the incidence depends on the dose injected. Hormones used as oral contraceptives did cause aneuploidy in oocytes, but only after daily treatment with high doses. Hormones used for stimulated ovulation did not interfere with chromosome segregation in the mouse and Chinese and Syrian hamsters. The following problems may be considered in futre studies: the problem of a species-specificity for induced nondisjunction; the question of a stage sensitivity (transplacental treatment); what happens after chronic exposure, also at low doses; the presence of a threshold; the existence of a dose-effect relation; the nature of cellular target(s) responsible for induced nondisjunction (spindle, regulatory proteins for polymerization of microtubules and ther depolymerization, centrioles, centromeres, RNA, or gene expression); whether DNA is involved and whether repair capacity plays a role.

Alkylating Agents↗
PubMed1979

Clustering of chromosomal aneuploidy and tracing of nondisjunction in man.

Chromosomal aneuploidy is the most frequent genetic damage observed in newborn children and originates as a rule from nondisjunction during maternal or paternal germ cell development. The error of chromosome segregation could be allocated in the past--at least in cases of 47,XXY--to maternal meiosis I (50%) or meiosis II (10%) and to paternal meiosis I (40%). Recent cytological improvements with various banding techniques enabled a further study on the origin of nondisjunction. Summarizing the published data one can argue that errors in Downs' syndrome are most often due to cleavage errors during maternal meiosis I. Approximately 70% of errors occur in oogenesis and only 30% in spermatogenesis. Maternal meiosis I seems also to be involved in most cases of fetal trisomy 16. Such a preferential missegregation of chromosomes offers the possibility of studying more closely the very mechanisms of nondisjunction in mammalian meiosis and early cleavages.

Aneuploidy↗
PubMed1978

Cri-du-chat syndrome in a child with a 5/15 translocation and interstitial centromeric heterochromatin.

A child is described with most of the typical clinical features of the cri-du-chat syndrome. G- and C-banding studies revealed the karyotype 45,XX, -5, -15, +tdic (5;15) with the loss of short arm material from chromosome 5. Centromeric heterochromatin of the translocated No. 15 is still present in the translocation chromosome. However, no silver precipitation after AgNO3-staining was observed on the translocation chromosome, thus indicating a loss or genetic inactivation of the NOR-region of the translocated No. 15. These cytogenetic results and their possible relationship to the cri-du-chat phenotype are discussed.

Centromere↗
PubMed1977

The RBE of 30 kV X-rays for the induction of dicentric chromosomes in human lymphocytes.

The frequency of dicentric chromosomes induced by the irradiation of human lymphocytes in Go phase was determined with hard (150 kV) and soft (30 kV) X-rays. When a linear-quadratic dose-effect relation was used to fit the experimental data, a significant linear contribution was found for 30 kV X-rays. The RBE of 30 kV compared with 150 kV X-rays approaches the value 3 at a 30 kV X-rays dose of 20 rad and decreases with increasing dose. From the results it may be concluded that chromatids with primary breaks, undergoing second order reactions and thus forming dicentric chromosomes, are produced by traversals of low-energy electrons through chromatin material.

Adult↗
PubMed1976

On the origin of the supernumerary chromosome in autosomal trisomies--with special reference to Down's syndrome. A bias in tracing nondisjunction by chromosomal and biochemical polymorphisms.

The differential staining methods for chromosomes have led to the demonstration of more chromosomal polymorphisms. Not rarely, these polymorphisms allow in autosomal trisomies the detection of parental origin of the supernumerary chromosome. In addition, the malsegregation may be ascribed to 1st or 2nd meiotic division in informative families. This approach of analyzing possible causes of trisomies is subject to a considerable bias. Trisomic phenotypes are twice as frequent for 2nd meiotic errors than for 1st meiotic errors. Also, rare chromosome variants seldom occur in matings where malsegregation in 1st meiotic division can be detected. In the present paper this bias is analyzed mathematically on the family as well as on the population level. From this mathematical analysis and from the data in the literature we conclude that Down's syndrome as a whole is caused about 5-10 times more often by a malsegregation in 1st meiotic than by an error in 2nd meiotic division. Mainly from experimental studies in rodents, causes for errors in 1st and 2nd meiotic division are becoming apparent. They are summarized in the context of the results of the present paper.

Down Syndrome↗
PubMed1976

Structural variability of human chromosome 9 in relation to its evolution.

Human chromosome 9 shows a high susceptibility for structural rearrangements, particularly pericentric inversions, which often are transmitted. Three types of pericentric inversions can be observed on No. 9: 1) Type I, showing the total constitutive heterochromatin in the short arm. 2) Type II with part of the C heterochromatin on the short arm, the rest located on the long arm proximal to the centromere. 3) Type III: a subtelocentric chromosome with part of the C heterochromatin in the very short arm and the rest located interstitially on the long arm. With these inversions as well as with other structural rearrangements, e.g. translocations, the break-points are located preferentially within the C heterochromatin or close to the heterochromatic-euchromatic junctions. These findings are in contrast to the findings in lymphocytes from 5 patients with fancomi's and after irradiation in vitro, reported in the literature. In lymphocytes break-points seem to be distributed more or less by chance. These observations together led us to speculate that human chromosome 9 primarily was an acrocentric chrosome; in morphology and at least in some functions similar to D- and G-group chromosomes. During evolution this acrocentric chromsome changed to a submetacentric one due to a pericentric inversion.

Animals↗
PubMed1975

A subtelocentric chromosome 9 in a dysplastic 18-year-old boy with dissociated mental development.

A subtelocentric C-group chromosome was identified as inv(9) (p24q12) in an 18-year-old young man who shows few dysplastic signs and who suffers from dissociated mental development. Pericentric inversions producing an almost metacentri No. 9 have been reported in several studies. The frequency of which proved to be high. There is an apparent lack, however, of inverted acro- or subtelocentric No. 9 reported in the literature. This obvious difference in the break points on chromosome 9 is most likely due to 1. hot-spots for chromosome breakage i.e. highly susceptible regions such as the euchromatic-heterochromatic junctions. 2. a higher degree of elimination against such acro- or subtelocentric chromosomes from one generation to the other.

Adolescent↗
PubMed1975

Chromosome anomalies in mouse oocytes after irradiation.

We investigated the cytogenetic effects of X-rays on unfertilized mouse oocytes. NMRI females received an irradiation with 0,22.2,66.6,200, and 600 R during the preovulatory phase 3 hrs after HCG (human chorionic gonadotrophin). This is a stage during oogenesis in which the oocytes pass from late dictyotene to diakinesis. Chromosome analysis was performed after ovulation at metaphase II. From these experiments we can draw the following conclusions: 1) X-rays induced during the preovulatory phase a high number of chromosome anomalies. Among these, structural anomalies prevail. 7 out of 144 ovulated oocytes in matched controls carried such an abnormality, whereas after irradiation we observed with 22.2, 66.6, 200, and 600 R, 11 out of 72, 34 out of 108, 89 out of 102, and 122 out of 124, respectively. 2) Irradiation seems also to affect the chromosome segregation during the 1. meiotic division, as we observed after 22.2, 66.6, and 200 R a total of 6 oocytes out of 204 with a supernummary chromosome. In controls, however, no hyperploidy was found in 143 ova. This increase, however, was not significant. 3) Chromosome anomalies, e.g. breaks and deletions that go back to a one-break event increased linearly with increasing dose. Exchanges, however, going back to two-break events fittest best to the linear-quadratic dose-response model. 4) The dose of 600 R seems to represents a kind of borderline in this experiment, because nearly all (122 out 124) carried at least one structural chromosome anomaly. It is also this dose after which the highest frequency of reciprocal translocations was observed in a hump-shaped slope in spermatocytes after irradiation of spermatogonia (Preston and Brewen, 1973). With an increasing dosage up to 1200 R the frequency of translocations decrease again. The elimination of cells, crossing this borderline, might be due to genetic or non-genetic effects. 5) The frequency of radiation-induced translocations per oocyte agrees with the frequency of translocations in human lymphocytes (Dolphin and Lloyd, 1974) after in vitro irradiation. 6) Significant, lower frequencies of structural chromosome anomalies were observed irradiating earlier stages of mouse oogenesis. These stages are dictyotene from females at the age of 3, or 6 weeks and prophase I-stages in female embryos on the 17th day of gestation. This result may be due to a lower sensitivity of these stages or to modifying events during the interval between irradiation and preparations.

Animals↗