bluuebunny/crossref_metadata_2025 huggingface dataset:
Regional mapping of the gene for human UDPGal 4-epimerase on chromosome 1 in mouse-human hybrids
Authors: Lin M.S. , Oizumi J. , Ng W.G. , Alfi O.S. , Donnell G.N.
Published: May 2008

Somatic cell hybrids between mouse and human cells containing two different reciprocal translocations involving human chromosome 1, 46, X, t(l;X)(ql2;q26) and 47, XX, + 21, t(l;17)(p32;pl3), were studied for the expression of human uridine diphosphate galactose 4-epimerase (UDPGal 4-epimerase, E.C. 5.1.3.2) by starch-gel electrophoresis. Analysis of the hybrid clones for the expression of the enzyme and the presence of the translocation chromosome 1 has permitted the assignment of the gene for human UDPGal 4-epimerase to the pter→p32 region of chromosome 1.
Chromosomal evolution in Malagasy lemurs
Authors: Rumpler Y. , Dutrillaux B.
Published: May 2008

The karyotypes of five species of Malagasy lemurs are described and compared with those of 12 previously studied species or subspecies. Based on these studies, phylogenetic relationships among nearly all the species of Cheirogaleidae and Lemuridae are proposed. The karyotype of the common ancestor is identical or very similar to that of Microcebus. Nearly 60 chromosomal changes, including five intrachromosomal rearrangements of the X chromosome, have been detected during the evolution of these two families. The possible evolutionary role of the different chromosomal rearrangements is discussed.
An examination of chromosomes in the stallion (Equus caballus) during meiosis
Authors: Scott I.S. , Long S.E.
Published: May 2008

Meiotic preparations were made from testicular material obtained after surgical castration of eight stallions (Equus caballus) with normal spermatogenesis. The material was examined after conventional Giemsa staining and C-banding. C-banding demonstrated that the Y chromosome at diakinesis associated with the short arm of the X chromosome. In 315 cells at diplotene or diakinesis, 56 (17.7%) had univalents and 51 (16.1%) of these involved the sex chromosomes. The overall mean chiasma number was 54.4 ± 1.8 sd, and the mean calculated nondisjunction (ND) frequency was 3.4%. These results are discussed in relation to other domestic species.
Nucleolus organizer regions in translocations involving acrocentric chromosomes
Authors: Mikkelsen M. , Basli A. , Poulsen H.
Published: May 2008

Twenty-seven Robertsonian translocations and five translocations involving one acrocentric and one nonacrocentric chromosome were examined with the aid of three staining methods. The chromosomes were identified by Q-banding, and the slides were then destained and restained with a silver impregnation method for nucleolus organizing regions (NORs). Replicate slides were C-banded. The centromeric region of one familial (15q21q) translocation chromosome had a large silver block and two widely separated blocks of C chromatin. Also, the centromeric region of the small translocation chromosomes in a de novo (13;15) translocation was heavily stained with silver. This was the only case where both reciprocal products of a Robertsonian translocation were found. In the other 25 Robertsonian translocations examined, no NOR staining regions could be identified, although five chromosomes each had two centromeric heterochromatic blocks. In the (1;13), the (7;13), and the (12;21) translocations, one of the two chromosomes involved in the translocation retained the NOR region. This was not true for two other cases, one a t(6;15) and the other a t(9;15). An evaluation of the number of NOR regions revealed that in the cells of balanced carriers there was a maximum of six to eight NOR sites, whereas in the unbalanced state the maximum number was six to nine. In the t(13ql4q) the silver-stained sites on other acrocentric chromosomes were larger. This was rarely found to be the case in the other types of Robertsonian translocations.
Regional mapping of ADA and ITP on human chromosome 20: cytogenetic and somatic cell studies in an X/20 translocation
Authors: Mohandas T. , Sparkes R.S. , Passage M.B. , Sparkes M.C. , Miles J.H. , Kaback M.M.
Published: May 2008

An apparently balanced de novo translocation between chromosomes X and 20, 46, X, t(X;20)(Xp20q;Xq20p), was identified in a severely retarded 13-year-old female with macrocephaly, bilateral overfolded pinnae, elbow contractures, clinodactyly, and seizures. BudR-pulse studies show the normal X chromosome to be late replicating in both lymphocytes (50 cells) and skin fibroblasts (25 cells). An HPRT deficient Chinese hamster line was fused with lymphocytes from the patient, and hybrid lines were derived in HAT medium. Cytogenetic and biochemical analyses of these hybrid lines show that the locus for adenosine deaminase is in the cen→qter region and that the locus for inosine tri-phosphatase is in the pter→cen region of human chromosome 20.
The induction of host cell mitoses in a transplantable ascites tumor
Authors: Levan A. , Levan G.
Published: May 2008

The implantation intraperitoneally of in vitro cell lines of the SEWA mouse ascites tumor into syngeneic mice and into allogeneic thymusless nude mice stimulated mitotic activity in the host component of the ascites cell population. The mitoses were found almost exclusively during the first month after the change in environment, while the tumor cells gradually readapted to in vivo growth. Normal mitoses appeared immediately after the transfer in vivo, reached a maximum at days 10 to 20, then decreased in frequency and disappeared completely after day 33. At that time, the tumor cells had recovered viability and started growing with full vigor. The ascites samples in which normal cells were undergoing mitotic division often contained a low proportion of tumor cells and a high proportion of small inflammatory cells. The chromosomes of the normal mitoses differed from those of the tumor mitoses by being smaller and more crowded. Their relative uniformity in type was also accentuated by the fact that they were all characterized by a low but ubiquitous incidence of chromatid breaks. These features suggested that the normal mitoses belonged to the lymphocytic population and represented a defense mechanism of the host towards the tumor. Since normal mitoses were especially frequent in the ascites cell population of the thymusless mice, it may be speculated that T-lymphocytes were not the main target cells for the mitotic induction.
Cytogenetic toxicity of cyclophosphamide and its metabolites in vitro
Authors: Au W. , Sokova O.I. , Kopnin B. , Arrighi F.E.
Published: May 2008

The effects of cyclophosphamide and three of its known metabolites (nitrogen mustard, acrolein, and nor-nitrogen mustard on chromosome breakage and sister chromatid exchange (SCE) were analyzed in vitro with and without the presence of a metabolic activating system (liver S9). We confirmed that cyclophosphamide induced chromosome breakage and SCE only in the presence of S9. After metabolism, cyclophosphamide was more active than the other agents in inducing SCE. Thus, the agent(s) directly responsible for this induction of a high SCE rate was not analyzed in this study. On the other hand, acrolein was most toxic to cell proliferation and most active in inducing chromosome breakage. The cytogenetic toxicity of these agents in comparison with their mutagenic and therapeutic activities is discussed.
Structure of the mitotic apparatus and chromosomes after hypotonic treatment of mammalian cells in vitro
Authors: Brinkley B.R. , Cox S.M. , Pepper D.A.
Published: May 2008

Cultured mammalian cells were exposed briefly to culture media made hypotonic with various dilutions of distilled water. Electron microscopic observations and tubulin immunofluorescence were carried out on mitotic cells that had been briefly exposed to hypotonic conditions. Similar observations were made on cells that had been exposed to hypotonic medium and then returned to isotonic conditions. These experiments provided new insight into the structure and physical properties of the mitotic apparatus and chromosomes. Spindle micro tubules were reversibly depolymerized by hypotonic treatments. Spindle fibers disappeared after a 15-min exposure to hypotonic medium, leaving only two brightly fluorescent spindle poles. When hypotonically swollen cells were returned to isotonic medium for 15 min prior to fixation, the spindle was reassembled. Several types of spindle aberrations were noted in cells recovering from hypotonic treatment. Chromosomes were greatly expanded by hypotonic treatment, and the kinetochores were disrupted. When treated cells were returned to isotonic culture medium, the chromosomes recondensed and the kinetochores reappeared. Brief hypotonic treatments, described herein, had no adverse effect on cell viability and may prove useful in investigations of the structure and physical properties of the mitotic apparatus.
Investigation of the determinants of nuclear pore number
Authors: Maul G.G. , Deaven L.L. , Freed J.J. , Campbell Le M. , Beçak W.
Published: May 2008

To assess the functional significance of nuclear pore complexes, we have investigated whether the number of pores per nucleus is determined by such factors as the nuclear volume, nuclear surface area, DNA content, or aspects of nuclear activity. Comparisons were made between cell types chosen to permit observation of differences in nuclear pore number as a function of differences in the other qualities measured. The number of nuclear pores was determined by freeze-etching and measurements of nuclear surface and nuclear volume by electron and light microscopy. Pairs of cell strains in culture that contained different numbers of chromosome sets were investigated to examine the relation of pore number to total DNA content. Tetraploid cells of the rat kangaroo (Potorous tridactylus) have almost exactly twice the number of pores found in the parental diploid strain. However, the pore number in diploid grassfrog (Rana pipiens) cells was only 65% greater than in the parental haploid cells. In addition, a polyploid series of nucleated RBC had a 62% pore number increase with each successive increase in ploidy. Diploid cell strains from the canyon mouse (Peromyscus crinitus) and from the cactus mouse (P. eremicus) were compared to test whether a difference reflecting the 36% additional DNA in cells of the latter, associated with extra heterochromatin, existed. Although both were found to have the same number of pores and nuclear surface area, the cells differed in nuclear volume. These observations suggest that the number of nuclear pores is independent of the total amount of nuclear DNA, the nuclear surface area (and, thus, presumably the fraction of DNA that is bound to the nuclear membrane), the nuclear volume, and the size of the genome. Rather, the number of nuclear pores appears to be associated with some aspect of nuclear metabolic activity, e.g., transcriptional capacity or release of products to the cytoplasm. Further evidence for such a view comes from studies of chick embryo erythroblasts. In these, nuclear pore number was found to be lower in association with the decreasing nuclear transcriptional activity and longer generation times that characterize the successive cell divisions leading to the fully differentiated state. The number of pore complexes reconstructed in the last cell cycles declined in a manner consistent with reutilization of previously formed pores in the absence of new pore synthesis. Challenging this interpretation is the increase in pore number at lower metabolic activity when Xenopus laevis cells are grown at different temperatures. The speculation that pore complexes have a longer half-life in cooler grown Xenopus cells could resolve the discrepancy.
A new chromosome region possibly derived from double minutes in an in vitro transformed epithelial cell line
Authors: Cowell J.K.
Published: May 2008

Double minute chromosomes (DMs) are reported for the first time in in vitro transformed mouse epithelial cells. In one cell line, CSG 122/17, DMs persisted through numerous passages. A subpopulation appeared in this line at passage 23, in which the DMs had disappeared but were replaced by a finely banded chromosome region possibly associated with the distal end of chromosome 5. In a second cell line, CSG 120/7, there was no evidence of DMs in the earliest frozen stock available. However, a finely banded region similar to that found in CSG 122/17 was present and was again associated with chromosome 5, in this case with the proximal end. The possible evolution of these new chromosome regions from DMs is discussed.
Regional chromosome mapping of the human skin type I procollagen gene using adenovirus 12-fragmentation of human-mouse somatic cell hybrids
Authors: Church R.L. , SundarRaj N. , McDougall J.K.
Published: May 2008

Previous work, using human-mouse somatic cell hybrids, has localized the structural gene for human skin type I procollagen (COL 1) to chromosome 17. One of these hybrids contained only the long arm of human chromosome 17, translocated onto a mouse chromosome, as human chromosomal material. This hybrid was treated with adenovirus 12, and various clones were picked which contained different-sized fragments of human chromosome 17 that were still translocated onto a mouse chromosome. Measurements of these fragments, combined with assays for human COL 1 production and galactose kinase (GAK) activity (also localized on the long arm of human chromosome 17), has allowed us to regionally map the structural gene for human COL 1 to an area just distal to the thymidine kinase (TK) and GAK genes within bands q21 and q22 on human chromosome 17.
Light microscopic observations on the behavior of silver-stained trivalents in pachytene cells of Sigmodon fulviventer (Rodentia, Muridae) heterozygous for centric fusion
Authors: Elder F.F.B. , Pathak S.
Published: May 2008

Silver-stained pachytene cells of male cotton rats, Sigmodon julviventer, heterozygous for a naturally occurring Robertsonian fusion, were examined by light microscopy. Silver staining clearly revealed synaptonemal complexes of all autosomal bivalents and of the translocation trivalent, as well as X-Y conformations within the sex vesicle. The synaptonemal complex of the trivalent conforms closely in morphology to that observed by electron microscopy in hybrids of other species. In all cases, the proximal telomeric knobs of the two acrocentric elements were paired and projected in the same direction from the metacentric element. The geometry of trivalent pairing in pachytene may predispose to normal disjunction and, therefore, account for the high fertility observed in 5. julviventer heterozygotes.
rDNA levels in infertile male carriers of Robertsonian translocations
Authors: Guanti G. , Zuffardi O. , Tiepolo L.
Published: May 2008

The amount of ribosomal DNA in 12 infertile male carriers of Robertsonian translocations and in some of their fertile relatives with the same translocation or with a normal karyotype was determined by RNA/DNA hybridization. This was done to test the hypothesis that infertility results from the loss of ribosomal cistrons at the chromosome breaks and mendelian segregation of the remaining acrocentrics such that these subjects do not have threshold amount of rDNA. The mean saturation value for the infertile patients (0.0258%) was similar to that of the fertile carriers of the translocation (0.0262%) and of the relatives with a normal karyotype (0.0277%). The data do not support this hypothesis.
Evidence of similar organization of the chromosomes carrying the major histocompatibility complex in man and other primates
Authors: Garver J.J. , Estop A.M. , Meera Khan P. , Balner H. , Pearson P.L.
Published: May 2008

The chromosome localization and gene synteny of the major histocompatibility complex (MHC) of the great apes and rhesus monkey were investigated using somatic cell hybrids. The presence of the MHC antigens was determined either with a microadsorption technique employing primate alloantisera, or with a radioimmune assay. The enzymes phosphoglucomutase 3 (PGM3), glyoxalase 1 (GLOl), mitochondrial superoxide dismutase (SOD2), and soluble maleic enzyme (ME1) were assayed in those hybrids where electrophoretic separations could be achieved. A chromosome homologous to the human No. 6 was found in the chimpanzee, gorilla, orangutan and rhesus monkey, and its genomic organization is similar to that of man.
Suppression of tumorigenicity in somatic cell hybrids
Authors: Klinger H.P.
Published: May 2008

Cell hybrids between nontumorigenic human diploid and tumorigenic heteroploid cells of the D98AH2 strain initially contain a complete or nearly complete chromosome complement of both parental lines. Of 35 such independent isolates all failed to form tumors when inoculated at 146 different sites in nude mice, even at cell doses 40 fold greater than those at which D98AH2 cells produce tumors. This agrees with observations of others in similar intraspecific systems. These hybrids remained nontumorigenic after subcloning and prolonged culture. However, they had not lost their tumorigenic potential since tumorigenic isolates could be recovered at a low incidence either by selecting in semisolid medium or by backselecting in 6-thioguanine supplemented medium. These tumorigenic isolates had lost chromosomes, primarily those of the diploid parent, suggesting that these chromosomes convey the suppressor information. Only specific chromosomes can carry such information, since other isolates with equally low chromosome numbers were not tumorigenic. A series of cell phenotypes often found in tumorigenic cells, such as infinite life span, anchorage independence, loss of contact inhibition, decreased fibronectin production, and ability to grow at low serum concentration, were found to segregate independently of tumorigenicity, clearly indicating that they are under separate control and that they are not cell properties that by themselves, or in concert, are essential for the tumorigenic phenotype. This agrees with observations of others. However, there was some indication that these characters may potentiate tumorigenicity.
Effect of Different Biomedical Membranes on Alkali-Burned Cornea
Authors: Du Li-Qun , Wu Xin-Yi , Li Ming-Chun , Wang Shen-Guo , Pang Kun-Peng
Published: May 2008

Objective: To evaluate the effects of different biomedical membranes on alkali-burned cornea in vivo. Methods: 12 New Zealand rabbits were chosen and randomly divided into four groups. The right cornea of each rabbit was made into an alkali-burned model with 1 mmol/l NaOH. Poly-D,L-lactic acid (PDLLA), PDLLA modified with collagen (PDLLA/collagen) and PDLLA modified with chitosan (PDLLA/chitosan) membranes were transplanted onto the alkali-burned corneas for evaluation. Clinical evaluations were performed daily with a slit lamp. On the 12th day after surgery, the progress in wound healing was compared by clinical and histological examination. The reepithelialization of each cornea was evaluated with fluorescein staining and 3 corneas of each group were excised to observe histological changes such as corneal wound healing, inflammation and collagen synthesis. Results: The wound healing rate of the PDLLA/chitosan group was higher than in the other groups. A more orderly arrangement of collagen and mild inflammation was observed. The control group had the next best performance, while the PDLLA/collagen and PDLLA alone treatment groups showed the worst results. Conclusion: PDLLA/chitosan promoted wound healing of alkali-burned corneas in vivo and decreased scar tissue formation, while the effect of the PDLLA/collagen and PDLLA membranes was to promote corneal ulcers, which suggests that PDLLA/chitosan membrane transplantation is a potential effective strategy for treatment of alkali-burned cornea.
Chromosomal interrelationship of hamster species of the genus Mesocricetus
Authors: Popescu N.C. , DiPaolo J.A.
Published: May 2008

The similarity of chromosomes and the mode by which differences occurred in the chromosomes of the species comprising the genus Mesocricetus, M. auratus (2n = 44), two “cryptic” species of M. brandti (2n = 44 and 2n = 42) and M. newtoni (2n = 38) were determined. Most of the autosomes and the sex chromosomes have either complete or partial G-band correspondence and thus provide definitive evidence for the taxonomic relationship of these species. The karyotypic differences occurred primarily as a result of deletion of sex chromosome heterochromatin and of autosomal translocations that frequently involved chromosomes with heterochromatic short arms or chromosomes bearing NOR’s. Only one Robertsonian centric fusion occurred. Despite the conservatism of arrangement of the genetic material, the chromosomal distribution of heterochromatin diverged during the evolution of these species. M. brandti and newtoni each have a metacentric chromosome with a common long arm matching a submetacentric M. auratus autosome, but a short arm corresponding to two different M. auratus chromosomes. These translocations are crucial for explaining the direction of chromosomal evolution of these species and indicate that M. auratus was the common ancestral species and that M. brandti and newtoni subsequently evolved independently.
Location of the 18S and 28S rRNA cistrons in the genome of the domestic rabbit (Oryctolagus cuniculus L.)
Authors: Martin-DeLeon P.A.
Published: May 2008

The genomic location of rDNA in the rabbit was determined by in situ hybridization with 125I-labeled ribosomal RNA (rRNA). The results demonstrate the presence of rRNA genes on chromosomes 13, 16, and 20, all of which have secondary constrictions, and on the telomere of the long arm of 21. The number of genes, as assessed by grain counts, was not equally distributed among the chromosomes. Chromosome 20 had the most copies and along with 13 and 16 carried significantly more genes than 21.
Banding studies on six killer whales: an account of C-band polymorphism and G-band patterns
Authors: Árnason Ú. , Sandholt B. , Lutley R.
Published: May 2008

The karyotypes of six killer whales were studied by banding techniques. A striking accumulation of C-heterochromatin has occurred in the Orcinus karyotype. The four telocentric pairs characteristic of the 2n = 44 cetacean karyotypes have become masked due to the accumulation of heterochromatin in the short arms. Conspicuous C-band polymorphism occurred in the materials studied, rendering each specimen karyotypically unique. Owing to the amount and variation of C-heterochromatin in the Orcinus karyotype, access to C-banded karyotypes was essential for the evaluation of the G-band pattern. The G-band pattern of Orcinus was found to be closely similar to that of Stenella. The results indicate an evolution of the Orcinus karyotype from the karyotypes characterizing other delphinids.
Assignment of PGM3 to the long arm of human chromosome 6
Authors: Mohandas T. , Sparkes R.S. , Shulkin J.D. , Sparkes M.C. , Moedjono S.
Published: May 2008

Hybrids derived from the fusion of thymidine kinase deficient Chinese hamster cells and human cells carrying a 6/15 translocation, 46, XX, t(6;15)(cen;pl3), were analyzed for the expression of human PGM3, GLO and ME1. The results show that PGM3 and ME1 are on the long arm and GLO is on the short arm of human chromosome 6.
Ring chromosome 12 and latent centromeres
Authors: Zuffardi O. , Danesino C. , Poloni L. , Pavesi F. , Bianchi C. , Gargantini L.
Published: May 2008

A ring 12 chromosome was found in a male child with minor phenotypic alterations. No obvious loss of chromosome material was detected. Since there is no other case of a ring 12 in the literature, it was not possible to determine whether the phenotype was due to (invisible) terminal deletions or to karyotypic variation. In lymphocyte cultures 9% of the cells had either no or two rings, but the patient’s RBC had normal activities of the enzymes lactate dehydrogenase B and peptidase B, whose loci are located on the proximal portions of 12p and 12q, respectively. Dicentric rings were found in 37 cells, and all had two active centromeres, in contrast with the relatively frequent finding of latent centromeres in translocated dicentric autosomes. Two latent centromeres were found in one tricentric “rod-shaped” open ring 12, probably derived from a tetracentric ring. It is postulated that latent centromeres are rare in ring chromosomes because, if consistent suppression of centromeres in excess of one took place at each duplication, rings with four, eight, or more centromeres would be formed rather frequently, which is not the case.
Induction of sister chromatid exchanges in mouse fetuses resulting from maternal alcohol consumption during pregnancy
Authors: Alvarez M.R. , Cimino, Jr. L.E. , Pusateri T.J.
Published: May 2008

Mice were force-fed ethyl alcohol at different doses, administration rates, and durations during pregnancy. A tablet of 5-bromodeoxyuridine (BrdU) was implanted sub-cutaneously in the animals between the 16th and 18th day of gestation. Twenty-one hours later, the animals were killed, the fetuses removed, and the fetal liver cells treated to exhibit sister chromatid exchanges (SCE’s). The following conclusions were drawn: Ingestion of alcohol by pregnant mice induced SCE’s in the liver cells of their fetuses. The number of exchanges in the fetal cells was directly proportional to the amount of alcohol consumed by the dam in the period when BrdU was present in her blood. (3) The induction of exchanges above control level was due entirely to alcohol ingestion and was independent of exposure to BrdU, any other drug, or any dietary deficiency. There is an association between maternal alcohol consuption during pregnancy and birth defects, both in children and in experimental animals (Hansen et al., 1976; for review of animal experiments, see Sandor and Elias, 1968; Green, 1974; Warner and Rosett, 1975). While there is no direct evidence to date that any of these defects result from chromosomal damage, some
Chromosomal assignment of the gene for folylpolyglutamate synthetase to human chromosome 9
Authors: Jones C. , Kao F.-T. , Taylor R.T.
Published: May 2008

An auxotrophic mutant, GAT-, derived from the Chinese hamster cell line CHO-K1 and exhibiting multiple growth requirements for glycine, adenine, and thymidine, has been shown to be deficient in one of the folate-dependent enzymes, folylpolyglutamate synthetase (FPGS). This mutant was fused with normal human lymphocytes and human lymphoblasts and 41 GAT + primary hybrid clones were isolated in medium lacking glycine, adenine, and thymidine. In addition, 71 secondary clones were isolated after growth of four primary hybrid clones in enriched medium, which allows losing the complementing human chromosome without losing cell viability. Analysis of human isozyme markers in the 112 primary and secondary clones established a syntenic relationship between the GAT marker and AK1, an isozyme marker for human chromosome 9. Enzyme studies of the parental and hybrid cells not only showed restored enzyme activities of FPGS in the hybrids, but also demonstrated that several enzyme characteristics of FPGS in the hybrids are consistent with those of the human enzyme. Thus, it is concluded that the human gene coding for the enzyme FPGS which complements the auxotrophic mutant GAT- in the CHO-K1 cells can be assigned to human chromosome 9. This assignment provides an additional selective marker for mammalian cell genetic analysis in which human chromosome 9 can be selectively and stably retained in the cell hybrids.
Immunogenetics of sex determination in the polled goat
Authors: Shalev A. , Short R.V. , Hamerton J.L.
Published: May 2008

Using the protein A rosette technique, it was found that the gene for polledness (P) in goats is associated with the presence of H-Y antigen on the cell surface of cultured fibroblasts. Two XX intersex goats (PIP) were found to be H-Y+, and one heterozygous (P/+) normal XX female was also found to express H-Y antigen at a low level. The expression of H-Y antigen by intersex goats was found to be lower than that of normal XY males. The statistical analysis suggests that animals of the same genotype and sex might differ in the density of H-Y antigen on their cell surface, which might explain the variability in primary sex determination among intersex goats. The association between the gene for sex reversal and H-Y antigen is discussed in relation to the location of the H-Y gene(s).
Cytological evidence for an inactive X chromosome in murine oogonia
Authors: Gartler S.M. , Rivest M. , Cole R.E.
Published: May 2008

Purified fetal mouse germ cell preparations have been analyzed for the presence of a heterochromatic X chromosome at cell division. A single large heterochromatic chromosome is found in oogonia stage germ cells, but such a chromosome is not present in 16-day fetal oocytes. These results support the idea that mitotic stage germ cells are subject to X-chromosome inactivation and that they go through a reactivation step at meiosis.
Chromosome-specific patterns of mitomycin C-induced rearrangements in human lymphocytes
Authors: Schaap T. , Sagi M. , Cohen M.M.
Published: May 2008

A total of 1,319 chromosomal breaks and rearrangements, induced in human lymphocytes by mitomycin C, was investigated. Patterns of “preference” and “avoidance” among the partners of chromosomal rearrangements were easily discerned. The centromeric regions of chromosomes 1, 9, and 16 were most frequently involved in rearrangements that tended to occur between homologs. The acrocentric chromosomes prefer rearrangements within their own group, including homologs, and avoid involvement with the centromeric region of chromosome No. 9 (9c). Regions designated as “rarely rearranging” avoid the centromeres of 1 and 9 and prefer rearrangements within their own groups. No correlation could be demonstrated between the frequency of open breaks and rearrangements in the same chromosomal region.
Successful cryopreservation of tissue and skin fibroblast cultures from patients with mucolipidosis II (I-cell disease)
Authors: Buck D.W. , Hanssens L.K. , Kennett R.H. , Mellman W.J.
Published: May 2008

Freeze-induced injury is a commonly observed phenomenon with cultured fibroblasts from patients with I-cell disease (ICD). Cells from these patients have therefore not been widely available to investigators, which has inhibited the study of this complex disorder. Skin biopsies from three ICD patients, as well as fibroblast cultures derived from these biopsies, have been subjected to a series of freezing experiments. The results show that when standard freezing protocols are employed, skin biopsies from these patients, in contrast to cultured fibroblasts, tolerate freezing well. In addition, when subjected to prolonged incubation in the confluent state, fibroblast cultures will consistently withstand frozen storage and, upon thawing, will yield actively growing cultures, biochemically and morphologically indistinguishable from the cultures that were frozen. There was a direct correlation between incubation time at confluence and subsequent cell survival after freezing.
The chromosomes of a V79 Chinese hamster line and a mutant subline lacking HPRT activity
Authors: Thacker J.
Published: May 2008

Cells of the V79–4 Chinese hamster line were found to have a consistent set of 20 chromosomes. G- and C-band analysis showed that, compared to the standard 22 chromosome set of freshly isolated Chinese hamster cells, the V79–4 chromosomes had various characteristic deletions and rearrangements. However, it is probable that at least one copy of each autosome was still present, and three pairs of autosomes appeared unchanged from those in the freshly isolated cells. The establishment of this karyotype for V79–4 allows mutant sublines to be screened for chromosomal changes associated with the altered phenotype, and an example is given of a radiation-induced mutant lacking HPRT activity that had a clear X-chromosome rearrangement.
Flow-cytogenetics
Authors: Rabinovitch P.S. , O’Brien K. , Simpson M. , Callis J.B. , Hoehn H.
Published: May 2008

High-resolution flow-cytometric measurements of ethidium bromide/mithramycin-stained human fibroblast cultures reveal discrepancies between fluorescence pulse-height distributions and genome size as a function of cell strain, culture conditions, culture age, and proliferative stage. These discrepancies were quantitatively assessed by (1) evaluation of the variation of the widths of the 2c fluorescence pulse-height histogram peaks, (2) comparisons between sample to standard fluorescence ratios of 45, XO and 49, XXXXY cell strains, and (3) comparison of fluorescence intensities among cell populations of identical genome size but differing degrees of chromatin condensation (mitotic vs. nonmitotic cells of diploid and tetraploid cell strains). As in our previous studies with lymphocytes, our results suggest caution in equating fluorescence intensity with “DNA content” in flow measurements of nonhomogeneous cell populations. Conditions of cell culture and sample preparation must be standardized in order to compare “DNA content” differences by flow techniques. Remaining sources of variation presently limit detection to differences in DNA content of greater than 2%.
The location of chromosome breaks in Bloom’s syndrome
Authors: Lindgren V.
Published: May 2008

The lymphocytes of a patient with Bloom’s syndrome were examined for chromosome abnormalities. The break points involved in the abnormalities in this patient were found to be nonrandom in their distribution, as was previously described in the literature in another case. It is preliminarily proposed that, in both cases, many more breaks occur in chromosomal areas which replicate their DNA late in the S phase of the cell cycle than would be expected by chance. The particularly severe manifestations of the disease in this patient, including an unusually high percentage of cells with chromosome abnormalities, tend to confirm the suggestion that Bloom’s syndrome may not simply be the result of one structural mutation.
Mapping a marsupial X chromosome using kangaroo-mouse somatic cell hybrids
Authors: Donald J.A. , Hope R.M.
Published: May 2008

A series of marsupial-eutherian somatic cell hybrids was produced by fusion between lymphocytes from the red kangaroo (Macropus rufus) and HPRT-deficient mouse cells. The hybrids lost marsupial chromosomes and could therefore be used to map marsupial genes. Several of the hybrids contained a complete red kangaroo X chromosome and expressed the kangaroo form of the enzymes HPRT, G6PD, and PGKA. A number of HPRT-deficient revertant cell lines were derived from the hybrids. These possessed a variety of partially deleted X chromosomes. With these cell lines, it has been possible to establish the X-linkage of the genes for HPRT, G6PD, and PGKA in this marsupial and to localize these three genes to the terminal portion of the euchromatic arm of the red kangaroo X chromosome.
Heteromorphic sex chromosomes in three species of the genus Leporinus (Pisces, Anostomidae)
Authors: Galetti, Jr. P.M. , Foresti F. , Bertollo L.A.C. , Moreira Filho O.
Published: May 2008

The present paper describes three cases of heteromorphic sex chromosomes in fishes of the genus Leporinus (Anostomidae). An XX/XY type was found in Leporinus lacustris and a ZZ/ZW type in L. silvestrii and L. obtusidens. These facts agree with the observations of Ebeling and Chen (1970), who suggested that heterogamety evolved not once but many times among the teleosts.
Karyotypic analysis of methotrexate-resistant and sensitive mouse L5178Y cells
Authors: Berenson R.J. , Francke U. , Dolnick B.J. , Bertino J.R.
Published: May 2008

A lymphoblastic leukemia cell line, L5178YR, that is over 100,000-fold resistant to methotrexate (MTX) has been developed. Previous work has demonstrated that the resistant line has dihydrofolate reductase (DHFR) levels 300-fold higher than the sensitive parental cells, L5178Y. Resistant cells grown in the absence of MTX (L5178YR–) showed a similar level of DHFR activity. The increase in DHFR could be entirely accounted for by a corresponding increase in DHFR-specific mRNA and gene copies. Studies were carried out to determine whether these changes in the resistant cells were accompanied by karyotypic alterations. A detailed karyotypic analysis of the sensitive parental line (L5178YS) and the two resistant cell lines (L5178YR+ and L5178YR-) was performed. Although certain abnormal marker chromosomes were present in all three cell lines, the most striking consistent difference between the resistant and sensitive cells was the presence of a large, faintly banded region of intermediate staining intensity, termed a “homogeneously staining region” (HSR), inserted within a reduplicated part of chromosome 2. It was present in approximately 90% of resistant cells, and no more than one HSR was ever present in a cell. Hybridization in situ was performed to determine the chromosomal locations of DHFR genes. Utilizing a purified complementary DNA probe made from messenger RNA of the L5178YR+ cells, the genes were shown to be localized exclusively to the HSR.
Karyotype analysis and quantitation of viral transforming genes in Rous sarcoma virus transformed, revertant, and retransformed field vole cells
Authors: Woods W.G. , Lau A.F. , Krzyzek R.A. , Cervenka J. , Faras A.J.
Published: May 2008

Comparative studies of the number of cellular chromosomes and viral genes, including the gene required for malignant transformation, were performed on several clones of Rous sarcoma virus-transformed, revertant, and spontaneously retransformed field vole cells. The results of these studies indicate that no appreciable differences in either total viral gene equivalents or transforming gene sequences can be detected between transformed and revertant cell types, even though considerable differences in the number of certain chromosomes exist among the clones tested. Furthermore, no increase in the amount of total genes or transforming gene sequences accompanies retransformation of revertant clones, including clones that exhibited significant increases in chromosome number following retransformation.
High frequency of X-Y chromosome dissociation in primary spermatocytes of F1 hybrids between Japanese wild mice (Mus musculus molossinus) and inbred laboratory mice
Authors: Imai H.T. , Matsuda Y. , Shiroishi T. , Moriwaki K.
Published: May 2008

In the hybrids between Japanese wild mice (Mus musculus molossinus) and inbred laboratory mice (BALB/c and B10.BR, which were probably derived from M. m. domesticus), the X and Y chromosomes dissociated precociously at the first meiotic metaphase in some 70% of spermatocytes; that percentage was only 8.9% in inbred laboratory mice and 21.1% in wild mice. X-Y dissociation began at least at early diakinesis and continued during metaphase I (MI). Some autosomes of the hybrid (10.1%) and BALB/c (10.6%) mice also dissociated precociously, but there was no distinctive correlation between X-Y and autosomal dissociation. In BIO or B6 congenic lines with a Y chromosome from wild M. m. molossinus, there was an apparent tendency for the percentage of precocious X-Y dissociation to decrease with an increasing number of back cross generations. Based on these observations we concluded that: 1. the X-Y dissociation found is genetically controlled, perhaps by multiple genes; 2. these genes are located on autosomes and are active only when they are heterozygous; 3. the frequent dissociation of the sex chromosomes neither affects male fertility nor induces non-disjunction of the X and Y chromosomes, though it significantly reduces testes weight.
Lateral asymmetry in human chromosomes 1, 3, 4, 15, and 16
Authors: Brito-Babapulle V.
Published: May 2008

Chromosomes 1, 3, 4, 15, and 16 show lateral asymmetry after replication in the presence of BrdU and staining with Giemsa at pH 10.4. Lateral asymmetry is thought to result from an unequal interstrand distribution of thymine in regions of repetitive DNA. Compound lateral asymmetry in 1 may be due to the presence of two segments of DNA differing in base composition and with different strands rich in thymine. Polymorphism for lateral asymmetry is observed in the AT-rich quinacrine-positive centromeric regions of 3 and 4, even though none of the four satellite DNAs are demonstrable by in situ hybridization there. Other workers have shown that a satellite fraction isolated using Hoechst 33258 and an EcoRl restriction fragment of human satellite DNA map on 3. There is no evidence for the presence of satellite DNA on 4. Since 20% of the DNA in the human genome reassociates at a C₀t of ≤ 1 and only 4% is satellite DNA, 4 may have repetitive nonsatellite sequences; on the other hand the lack of an appropriate satellite probe may be the limiting factor. Lateral asymmetry in the Y has been demonstrated using the Hoechst method by other workers but cannot be observed with BrdU-Giemsa staining at pH 10.4.
Specific karyotypic alterations in colchicine-resistant cells
Authors: Kopnin B.P.
Published: May 2008

Djungarian hamster and mouse L-53 cell lines with 150–200-fold increases in resistance to colchicine contained marker chromosomes with a long homogeneously staining region (HSR). In two clones of Djungarian hamster cells, an HSR was located in the long arm of chromosome 4; in another Djungarian hamster cell line and in mouse L-53 cells, an HSR was located in unidentified marker chromosomes. During cultivation in colchicine free medium these cells lost their resistance at the rate of 2–3 x 10–2 cells per population doubling. The loss of resistance was accompanied by the disappearance of the HSR and emergence of possible double minutes (dmins). These observations suggest that colchicine-resistance is the result of gene amplification and support the idea that dmins may be derived from the HSR in these systems.
Factors affecting the sensitivity of rabbit lymphoid and bone marrow cells to Streptonigrin-induced chromosome aberrations
Authors: Huff V. , Littlefield L.G. , DuFrain R.J. , Wilmer J.L.
Published: May 2008

In previous cytogenetic studies of rabbits injected with the clastogen, streptonigrin (SN), we observed a higher incidence of chromosome aberrations in lymph node cells than in marrow cells recovered 6 h after treatment. In this study we examined several factors that may be responsible for this difference in the incidence of lesions. Results from SN pulse-treated lymphoid and marrow cultures demonstrated that the responses were different in vitro also. In addition, at higher doses of SN, lymphoid cells displayed a greater sensitivity to the drug when treated during DNA synthesis; marrow cells showed no differences in sensitivity throughout the cell cycle. Analysis of the percentage of lymph node and marrow metaphases labeled following 2, 4, or 6 h of culture in the presence of tritiated thymidine indicated that G2 was less than 2 h in lymph node cells and approximately 4 h in marrow cells. From these data we conclude that the difference in the length of G2 in the two cell types is partially responsible for the difference in the incidence of lesions 6 h after an in vivo SN exposure. However, our data also indicate that lymph node cells are innately more sensitive to the induction of lesions than are marrow cells.
Localization and metabolic activity of ribosomal genes in Chinese hamster meiotic and mitotic chromosomes
Authors: Jhanwar S.C. , Prensky W. , Chaganti R.S.K.
Published: May 2008

In situ hybridization of pachytene bivalents of a male Chinese hamster with 125Ilabeled rRNA permitted localization of rDNA. An analysis of the regional distribution of autoradiographic grains from 39 cells showed that rDNA sites were localized in the telomeric regions of chromosome arms 3q, 4q, 5q, 7q, 8p, and 9q. Of these, the sites on 3q, 4q, 5q, and 9q hybridized more frequently and also had significantly more autoradiographic grains than those on 7q and 8p, suggesting that the former four chromosomes had more rDNA than the latter two. The sex chromosomes did not exhibit specific labeling. Silver staining of pachytene chromosomes and sequential silver and quinacrine staining of somatic chromosomes of a second male animal permitted detection of metabolically active ribosomal genes at meiosis and at mitosis. All 12 sites were found to be potentially able to express nucleolus organizing function at meiosis, while expression by individual chromosomes was found to be variable at mitosis in this animal. Chromosomes 3, 4, and 9 showed a high degree of expression (91–97’% of cells with Ag-NORs). Chromosome 8 showed expression to a lesser degree (60% of cells with Ag-NORs), while chromosome 7 showed the weakest expression (29% of cells with Ag-NORs) of all chromosomes that had NORs. Expression by chromosome 5, while high (83% of cells with Ag-NORs), was probably restricted to one homolog. These results permitted two conclusions to be drawn: (1) the amount of rDNA present probably determined the frequency with which its metabolic activity was expressed, and (2) the two animals probably varied with respect to either the amount of rDNA present or its ability to express rDNA function on chromosome 5.
Leukocyte chromosomes from parents of cytogenetically abnormal offspring: preliminary observations
Authors: Stallard R. , Haney N.R. , Frank P.A. , Styron P. , Juberg R.C.
Published: May 2008

The frequency of sporadic, hypermodal chromosomal spreads in cultures of leukocytes taken from the parents of aneuploids significantly exceeds that in comparison populations. Elimination of other possibilities suggests mitotic nondisjunction as the ultimate determinant for such spreads. This possibility requires that more attention be paid to the occurrence of hypermodal spreads, especially relative to the etiology of aneuploid concepti.
A 53, X female sheep (Ovis aries)
Authors: Zartman D.L. , Hinesley L.L. , Gnatkowski M.W.
Published: May 2008

A female sheep with a 53, X karyotype was discovered while screening barren ewes at a commercial sheep ranch in New Mexico. She was physically normal in phenotype, in very good flesh due to freedom from nursing offspring, and her external genitalia were normal. This is the first case of monosomy X to be documented in sheep.
Effect of superoxide dismutase on the chromosomal instability of New Zealand black mice
Authors: Emerit I. , Levy A. , Michelson A.M.
Published: May 2008

The high chromosomal instability in New Zealand black mice was greatly reduced (to normal values) in vivo by repeated injections of bovine superoxide dismutase (Cu-SOD) over a period of 3 wk. The decrease in aberrations occurred in all the mice treated, and the SOD appeared to be effective for all types of aberrations, including chromatid gaps, telomeric constrictions, chromatid breaks, telomeric extrusions, and fragments.
Characterization of the Philadelphia chromosome by gene mapping
Authors: Geurts van Kessel A.H.M. , ten Brinke H. , Boere W.A.M. , den Boer W.C. , de Groot P.G. , Hagemeijer A. , Meera Khan P. , Pearson P.L.
Published: May 2008

Chinese hamster × human and mouse × human somatic cell hybrid lines were obtained using circulating leucocytes from six chronic myeloid leukemia patients. All six patients carried the Ph1 translocation, t(9q+;22q–), characteristic of chronic myeloid leukemia, in their dividing immature granulocytes. Analysis of independent hybrid clones yielded the following results: 1. The chromosome 9 markers, soluble aconitase and adenylate kinase-1, segregated with the 9q+ derivative. The latter marker has previously been localized to 9q34. 2. The chromosome 22 markers, mitochondrial aconitase, N-acetyl-α-D-galactosaminidase, and arylsulfatase-A, also segregated with the 9q+ derivative. Mitochondrial aconitase has recently been assigned to 22q11→22q13. No evidence was obtained either for reciprocity of the translocation or for variations in breakpoints in different patients. The results reported in this paper provisionally assign the gene for mitochondrial aconitase to a region distal to the breakpoint in 22qll.