Cholinesterase activity in the chondrocranium of normal and exencephalic mouse fetus with trisomy 12.

Cholinesterase (ChE) activity in the chondrocranium of normal and exencephalic trisomy 12 mouse fetuses was studied. Non-specific cholinesterase activity was found strongly in the developing bone cells at the central zone and weakly in the more maturely developed bone cells at the peripheral zone of the chondrocranium of both normal and exencephalic trisomy 12 mouse fetuses. In exencephalic mouse fetuses, the ChE-activity was lesser than in the normal ones which corresponded to hypoplastic chondrocranium. The centrifugal direction of the maturity of individual bone cells could be demonstrated by the activity of cholinesterase. The young bone cells showed strong ChE-activity while the more matured cells showed weak ChE-activity. The enzyme activity disappeared when the definite tissue structure was well developed. From this study, it may be concluded that ChE plays a role in chondrocranium development which is different from its known function in the adult tissue.

Restriction fragment polymorphism in the sex-determining region of the Y chromosomal DNA of European wild mice.

Using 32P-labeled probe consisting mainly of (GATA)n we have shown that a male specific Alu1 DNA blot pattern which defines the Y chromosome sex-determining locus in inbred mice is highly polymorphic in wild mice, indicating substantial sequence evolution in this region under field conditions. In all cases examined by in situ hybridization, the region concerned is paracentromeric. In contrast, the blot pattern of another probe (M 34) which detects repeated sequences specific to the mouse Y chromosome but outside the sex-determining locus, remains constant between different isolates.

Drug-induced liver injury in liver biopsies of the years 1981 and 1983, their prevalence and type of presentation.

Based on the histological picture of liver biopsies examined in the years 1981 and 1983, drug-induced liver injury has been suspected in 131 and 170 cases. In relation to the total number of the examined liver biopsies this accounted for 6 and 9.6%, respectively. In only 20 (i.e. 15%), respectively 17 (i.e. 10%) of the cases, a drug-induced injury could be clinically excluded. However, a drug-induced injury was doubtlessly secured in 21 (16%) and 28 (16.5%) of the cases. The histological phenotype seen in association with the incriminated drug is presented. In 90 (68.7%) and 125 (73.5%) of the cases it was neither possible to secure nor to exclude the drug as cause of this damage, either because in 32/72 cases the clinical work-up was incomplete or because the drug-induced damage was clinically suspected, but not sufficiently documented by follow-up examinations after drug-withdrawal.

Quantitative histology of human fetal testes in chromosomal disease.

Morphometric studies on male gonads were performed in 35 midterm fetuses aborted after prenatal diagnosis of a chromosome anomaly and in 11 chromosomally normal controls. A significant reduction of the number and volume percentage of premeiotic germ cells was observed in the chromosomally abnormal cases. Germ cell depletion was correlated with the severity of the chromosomal disease. It was least expressed in the XYY condition. In trisomy 13 and 18, depletion lead to values of less than a half or even a fourth the values of controls. Complex anomalies with XXY or XYY in addition to an autosomal disorder showed a moderate effect on germ cell reduction. No morphological differences were observed in germ cells or in Sertoli cells in a comparative electron microscopic study. Paucity of fetal germ cells can result from impaired colonization of the gonadal ridge, from low mitotic activity, or from increased premeiotic cell loss. All three factors seem to contribute to the above findings.

Susceptibility of mice reconstituted with trisomy 19 hematopoietic cells to infection with Rauscher leukemia virus.

Radiation chimeras with trisomy 19 hematopoietic cells were constructed to test the sensitivity of the trisomic hematopoietic system to infection with Rauscher leukemia virus: Hematopoietic cells from livers of trisomic fetuses were rescued by transplantation into lethally irradiated adult mice. These Ts 19 radiation chimeras show a stable and sufficiently long-lived trisomic hematopoiesis to allow experimental induction of Rauscher leukemia. Rauscher leukemia virus (RLV) induced a marked proliferation of erythroblasts in the spleens of Ts 19 mice and control chimeras within 3 weeks. The onset of erythroblast proliferation was significantly delayed in the Ts 19 mice, suggesting a smaller number of target cells for the RLV and/or reduced susceptibility of the target cells to RLV. Both Ts 19 and control chimeras developed nonlymphocytic leukemia 2-4 months after RLV injection. The course of leukemogenesis was similar in the two experimental groups. No numerical chromosome abnormalities associated with leukemogenesis were detectable in Ts 19 or control cells. The numbers of chromosomal sister chromatid exchanges 2 weeks after RLV injection were elevated to the same degree in both Ts 19 and control cells. Thus, cells with constitutional trisomy do not show increased chromosomal instability due to leukemogenesis.

Murine trisomy: developmental profiles of the embryo, and isolation of trisomic cellular systems.

Many questions related to the development and the phenotypic expression of trisomy (Ts) are amenable to systematic investigation in a mouse model that allows the induction of Ts 1 to 19 by a breeding design of mice heterozygous for Robertsonian metacentric chromosomes. Some Ts do not survive the first critical phase of organogenesis on days 11 to 12 of fetal development; others as Ts 12, 14, 16, 18, and 19, have a life span until or beyond birth. Model type studies of the morphogenesis of developmental anomalies (e.g. craniocerebral, cardiovascular, or placental) are possible in Ts with a longer developmental span, and Ts 16 of the mouse is considered as a natural model of human trisomy 21. The eventual breakdown and death of the trisomic organism are inevitable. There is considerable interest to find ways for rescue and longer survival of Ts in competitive developmental systems, as e.g., in Ts in equilibrium with 2n blastocyst chimeras, or by isolation of trisomic cellular or tissue systems. Thus, the transfer of Ts hemopoietic stem cells of the fetal liver to irradiated adult recipients is a means of studying the functional capacities and maturation of trisomic hemopoiesis and lymphopoiesis. Both are almost completely restored by Ts 12, 14, 18, and 19 stem cell transplantation with survival periods of more than 6 months. But in other Ts, as of chromosomes 13 or 16, such capacity of reconstitution is impaired. The stepwise analysis of the effects of chromosome triplication on the cell level, in isolated functional systems and in the embryonic organism, is a promising way to understand the phenotypic expression of genome anomalies in complex developmental processes.

Down's syndrome in the male. Reproductive pathology and meiotic studies.

Studies on testicular histology and meiosis were carried out by the use of light and electron microscopy in an 18-year-old Down's syndrome male in an attempt to follow the fate of the extra chromosome 21 and to evaluate the effects of this condition on spermatogenesis and the reproductive functions. The histological changes in the testes corresponded to spermatogenic arrest. Electron microscopic whole-mount spreadings of meiotic cells in the pachytene stage showed that in most nuclei an extra chromosome 21 was not detectable. Only in a small number of nuclei, univalents or trivalents with segmental pairing structures of an extra chromosome could be discovered. In contrast, the great majority of (C-banded) diakinesis figures showed the presence of a supernumerary G (no. 21) chromosome. The absence of a traceable extra chromosome 21 in most pachytene cells is explained by the assumption that it is intimately connected with and hidden in the sex vesicle, whose complex structure does not allow the identification of single elements. Strong support for this assumption is seen (a) in the general tendency of narrow spatial association of unpaired segments with the XY complex and (b) in close structural similarities occurring between univalents or nonsynapsed segments of trivalents and the nonpaired segments of the sex chromosomes. It is suggested that the association or connection of an extra chromosome with the XY complex during pachytene interferes with the phenomenon of X inactivation. In animal systems such abnormal interference is related with spermatogenic breakdown and, in a general way, with male hybrid type sterility. So far, the range of sterility vs. fertility in cases of male Down's syndrome is not yet fully clear, but it appears that impairment of fertility, and sterility are most frequent. If so, it is proposed that the effect of the trisomy 21 condition on spermatogenesis (and fertility) is a consequence of the behavior of the extra chromosome in the meiotic prophase.

Trisomy 13 in the mouse.

The fetal development of mice trisomic for chromosome 13 (Ts 13) was investigated. Trisomic fetuses were obtained from the progeny of male mice heterozygous for the two Robertsonian translocation chromosomes Rb (11.13)4Bnr and Rb (6.13)3Rma mated to "all acrocentric" NMRI females. Trisomic fetuses were found at all stages between days 12 and 19 of gestation (vaginal plug day counted as day 1). The frequency of trisomy was 24.8% of all surviving implants. The frequency of Ts decreased slightly but not significantly with progressing pregnancy. In eight newborn litters, two dead and four living trisomic newborns (13.6%) were found. The latter died within a few hours after birth. The most conspicuous features of Ts 13 fetuses were their small size and a marked hypoplasia as compared with their normal euploid in utero mates. The weight of the the trisomic fetuses and that of their placentas was significantly lower than of the normal controls at all stages studied. The general developmental delay and the delay of the ossification of Ts 13 fetuses were about 1 to 11/2 days. Cleft palate was observed in 86% of the Ts 13 fetuses. Edema developed in the neck and back of the trisomic fetuses from day 14 on; this disappeared after day 17. It is suggested that the hypoplasia and general retardation of growth found in trisomy 13 and in other autosomal trisomies, as well as the more or less specific palatal and cardiovascular malformations in this disorder, may be caused by impaired proliferation of trisomic cells. This postulated impairment of cell growth may also affect the fetal part of the placenta.

Trisomy 16 in the mouse fetus associated with generalized edema and cardiovascular and urinary tract anomalies.

Murine trisomy (Ts) 16 occurs in the fetal and neonatal progeny of males doubly heterozygous for the Robertsonian metacentric chromosomes Rb(16.17)7Bnr/Rb(9.16)9Rma and "all acrocentric" females. The developmental aspects of this trisomy were studied between day 12 of gestation and birth. So far, postnatal survival longer than a few hours after birth has not been observed. The frequency of Ts 16 among all implants decreased from more than 20% on day 14 to values between 4% and 7% shortly before term. Main features of Ts 16 are moderate general hypoplasia, slight developmental retardation, and cardiovascular anomalies. These latter were found in 96% of the trisomies, the great majority belonging to the transposition type, i.e., riding aorta, double outlet right ventricle (DORV) and transposition of the great arteries (TGA). Association with common atrio ventricular (AV)-canal was frequent. Other anomalies as "open eyelid", hydronephrosis, and hydroureter seem to be attributable to the effects of retardation. Generalized transient edema was frequent in the later gestational stages of Ts 16. Severe cardiovascular malformation is possible one of the factors responsible for late fetal or neonatal death in some cases. Another factor probably contributing to Ts 16 fetal mortality is insufficiency of placental function due to hypoplasia of the fetal vasculature of this organ. The teratological study of Ts 16 demands interest since evidence has been forwarded to consider this trisomy as an animal model of human trisomy 21.

Relevance of trisomy 15 and other chromosome abnormalities in spontaneous AKR leukemia of mice with and without Robertsonian rearrangement.

The types and frequencies of chromosomal abnormalities in spontaneous AKR leukemia are presented: 45% to 58% of leukemic animals exhibit chromosome abnormalities; trisomy of chromosome 15 (Ts 15) occurs as the predominant chromosome abnormality not only in AKR/J but also in two AKR sublines characterized by the presence of two or one Robertsonian biarmed translocation Rb (6.15) of the chromosomes 6 and 15. Most often a triplication of the whole Rb (6.15) is found in Rb (6.15) homozygotes corresponding to combined Ts 6 + Ts 15. In the Rb (6.15) heterozygotes both trisomy of the biarmed (6.15) and of the acrocentric 15 is observed. Centric fission of the (6.15) chromosome is also possible in Rb (6.15) homozygotes resulting in Ts 15 without simultaneous Ts 6. Trisomies of other chromosomes are found either in addition to Ts 15 or as the only abnormality. If the data of Dofuku et al. (1975) are considered, abnormal karyotypes in AKR leukemia show Ts 15 in 90%, Ts 12 and Ts 17 in 18%-20%, and Ts 3, Ts 10 and Ts 14 in 8%-10% of the cases.

Robertsonian karyotype variation in wild house mice from Rhaeto-Lombardia.

The European longtailed house mouse (M. m. brevirostris and domesticus) in the Rhaetian Alps and Lombardia presents a complex system of Robertsonian (Rb) variation and karyotype diversity, several adjoining populations homozygous for multiple Rb metacentric chromosomes, sites of coexistence of different Rb types, and zones of hybridization with non-Rb populations. The original "tobacco mouse" is just one of many local Rb variants, such as those from other Alpine areas (e.g., Orobian Alps) or from Central Lombardia, where a relatively large region within which the population is homogeneous for multi-Rb metacentrics is found. The present study is based strictly on material in which the chromosome arms were identified by G-banding, so that karyotypes within the areas under investigation could be compared. Altogether 111 mice were studied.

Chromosome rearrangements involved in the origin of trisomy 15 in spontaneous leukemia of AKR mice.

Trisomy 15, known to be the predominant chromosome abnormality in leukemic cells of the AKR strain, develops even in animals of the subline AKR/Rb1Ald with two constitutive Robertsonian translocation chromosomes (6.15). Among 10 leukemic animals of this subline exhibiting chromosomal anomalies, 6 showed trisomy of the whole Robertsonian translocation chromosome with the expression of combined trisomy 6 and 15 as the most frequent abnormality. Besides this, rearrangements were observed in five animals, most of them resulting from centric fission of the Rb(6.15) translocation chromosome. Trisomy 15 with two Rb(6.15) and an extra acrocentric 15 was found in 44% of spleen cells in one animal, and a new Rb translocation of chromosomes 11 and 15 was seen in 50% of spleen and thymus cells of another animal. In both cases trisomy 15 without simultaneous trisomy 6 resulted. Thus, the triplication of a whole Rb(6.15) is frequent in leukemic AKR/Rb(6.15)1Ald, and ensuing double trisomy 6 + 15 is tolerated by the leukemic cell. But the development of trisomy 15 combined with centric fission of Rb(6.15) without simultaneous trisomy 6 is another principle realized in leukemogenesis.