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At least 397 records · Page 22Linked to original sources
PubMed1997

Map integration at human chromosome 10: molecular and cytogenetic analysis of a chromosome-specific somatic cell hybrid panel and genomic clones, based on a well-supported genetic map.

Well-characterized, chromosome-specific somatic cell hybrid panels are powerful tools for the analysis of the human genome. We have characterized a panel of human x hamster somatic cell hybrids retaining fragments of human chromosome 10 by fluorescence in situ hybridization and associated them to genetic markers. Most of the hybrids were generated by the radiation-reduction method, starting from a chromosome 10-specific monochromosomal hybrid, whereas some were collected from hybrids retaining chromosome 10-specific fragments as a result of spontaneous in vitro rearrangements. PCR was used to score the retention of 57 microsatellite markers evenly distributed along a well-supported framework genetic map containing 149 loci uniquely placed at 69 anchor points (odds exceeding 1,000:1), with an average spacing of 2.8 cM. As an additional resource for genomic studies involving human chromosome 10, we report the cytogenetic localization of a series of YAC and PAC clones recognized by at least one genetic marker. Somatic cell hybrids provide a powerful source of partial chromosome paints useful for detailed clinical cytogenetic and primate chromosome evolution investigations. Furthermore, correlation of the above physical, genetic, and cytogenetic data contribute to an emerging consensus map of human chromosome 10.

Animals↗
PubMed2005

Karyotype of Brazilian Anopheles albitarsis sensu lato (Diptera:Culicidae).

Anopheles (Nyssorhynchus) albitarsis sensu lato is an important malaria vector in Brazil, especially in the Brazilian Amazon region. Chromosome preparations of fourth-instar larvae of A. albitarsis from Iranduba and Coari (AM) and Ilha Comprida (SP) were analyzed for karyotype determination and to improve cytogenetic identification of this species. Anopheles albitarsis possesses 2n = 6 chromosomes, with two pairs (submetacentric and metacentric) of autosomes and one pair of sex chromosomes, with X-Y dimorphism. The sex pair is homomorphic and acrocentric in females and heteromorphic in males, with a punctiform Y chromosome. Somatic pairing was detected in the prometaphase and metaphase chromosomes of the three A. albitarsis populations. Apparently, sex chromosome evolution in the Culicidae does not function as does evolution in the Culicidae, since it occurs in the subfamily Anophelinae, which possesses heteromorphic sex chromosomes and is regarded as primitive, based on several criteria. These karyotype data on the albitarsis complex reinforce the hypothesis that sex chromosome evolution in the subfamily Anophelinae is conserved, and the variation revealed in the mean size of chromosomes in three populations indicates that selective pressure in these populations is occurring only at a genetic level.

Animals↗
PubMed1980

[Psychic and psychosomatic symptom in pediatrics (author's transl)].

From the intimate relationship between somatic and psychic aspects, certain characteristics of the psychic or psychosomatic symptom in the child are sketched and the evolution from the psychic conflict to the elaboration of an specific symptom. The meaning of the symptom as a language or a means of expression of the child is pointed out, as well as the individual significance of the symptom in each clinical case, avoiding mechanical and reducing schemes. The importance of the "language of the body" in the infant and the symptom as a sign, signifies or symbol or as a unconscious fantasy related to the organ function in the school child. The importance of the first affective contacts in the child as etiopathogenic formations. Some anamnestic guidelines and practical evaluations are developed in each infantile functional disorder. Finally, the need for a deep study of the psychosomatic sphere is emphasized, looking for a balance between an attitude of underevaluation and one of hypertrophy, goal attainable by means of the integration of pediatrician infantile psychiatrists in an interdisciplinary team.

Child↗
PubMedDate not supplied

The canine p53 gene is subject to somatic mutations in thypoid carcinoma.

In many different types of tumors in man and mouse, p53 is the tumor suppressor gene most frequently affected by a combination of somatic mutation and loss of the wildtype allele. In order to develop a molecular tool to study the genetic evolution of tumors in the dog, we have cloned an evolutionary conserved part of the canine homologue of p53. The isolated genomic segment, 534 bp in length, contains the 3' half of exon 5, the complete exon 6 and the 5' half of exon 7, as well as the intronic intervening sequences. The gene organization of this segment shows strong homology to that published earlier for a number of other species, including man, mouse, and Xenopus laevis. This conservation is apparent at the DNA sequence level, as well as at the deduced aminoacid sequence level. mRNA expression can be detected at low levels in normal tissues with increased mitotic activity, and in the Madin-Darby canine kidney cell line. A-->G T transversion was found in 1 out of 23 investigated primary thyroid carcinomas at a position corresponding to codon 174 in the human p53, and was predicted to give rise to an aminoacid substitution in the protein. These results suggest that p53 plays a role in the development of malignancy in the dog, in a way comparable to that in man.

Amino Acid Sequence↗
PubMed1996

The evolution of clinical peripheral blood stem cell transplantation.

Our growing physiological understanding of hematopoietic progenitor cells has led to the clinical use of circulating progenitor cells, including stem cells, for either reconstitution of hematopoietic function, up to the transduction of functional genes into a self-renewing cell system. In the following, an attempt has been made to recollect the major steps in the evolution of clinical blood stem transplantation, from the morphological description of small lymphocytes circulating in the blood up to somatic gene therapy covering a time period of 87 years.

Animals↗
PubMed2005

The evolutionary origin of a complex scrambled gene.

Some species of ciliates undergo massive DNA elimination and genome rearrangement to construct gene-sized "chromosomes" in their somatic nucleus. An example is the extensively scrambled DNA polymerase alpha gene that is broken into 48 pieces and distributed over two unlinked loci in Stylonychia. To understand the emergence of this complex phenomenon during evolution, we examined DNA polymerase alpha genes in several earlier diverging species, representing evolutionary intermediates. Mapping these data onto an evolutionary tree suggests that this gene became extensively fragmented and scrambled over evolutionary time through a series of steps, each leading to greater complexity. Our results also suggest a possible mechanism for intron loss by deletion of intron sequences as DNA during development of the somatic nucleus.

Animals↗
PubMed1985

Characterization and evolution of a single-copy sequence from the human Y chromosome.

To study the evolution and organization of DNA from the human Y chromosome, we constructed a recombinant library of human Y DNA by using a somatic cell hybrid in which the only cytologically detectable human chromosome is the Y. One recombinant (4B2) contained a 3.3-kilobase EcoRI single-copy fragment which was localized to the proximal portion of the Y long arm. Sequences homologous to this human DNA are present in male gorilla, chimpanzee, and orangutan DNAs but not in female ape DNAs. Under stringent hybridization conditions, the homologous sequence is either a single-copy or a low-order repeat in humans and in the apes. With relaxed hybridization conditions, this human Y probe detected several homologous DNA fragments which are all derived from the Y in that they occur in male DNAs from humans and the apes but not in female DNAs. In contrast, this probe hybridized to highly repeated sequences in both male and female DNAs from old world monkeys. Thus, sequences homologous to this probe underwent a change in copy number and chromosomal distribution during primate evolution.

Adult↗
PubMed2005

AID from bony fish catalyzes class switch recombination.

Class switch recombination was the last of the lymphocyte-specific DNA modification reactions to appear in the evolution of the adaptive immune system. It is absent in cartilaginous and bony fish, and it is common to all tetrapods. Class switching is initiated by activation-induced cytidine deaminase (AID), an enzyme expressed in cartilaginous and bony fish that is also required for somatic hypermutation. Fish AID differs from orthologs found in tetrapods in several respects, including its catalytic domain and carboxy-terminal region, both of which are essential for the switching reaction. To determine whether evolution of class switch recombination required alterations in AID, we assayed AID from Japanese puffer and zebra fish for class-switching activity in mouse B cells. We find that fish AID catalyzes class switch recombination in mammalian B cells. Thus, AID had the potential to catalyze this reaction before the teleost and tetrapod lineages diverged, suggesting that the later appearance of a class-switching reaction was dependent on the evolution of switch regions and multiple constant regions in the IgH locus.

Animals↗
PubMed1993

The occurrence, role and evolution of chromatin diminution in nematodes.

Chromatin diminution takes place in presomatic cells of some parasitic nematodes during early development. This phenomenon may play an important role in somatic cell differentiation, since the somatic cells of these species undergo an extensive genome reorganization during development via chromatin diminution and polyploidization, as explained here by Clara Goday and Sergio Pimpinelli.

Journal Article↗
PubMed2000

Genome gymnastics: unique modes of DNA evolution and processing in ciliates.

In some ciliates, the DNA sequences of the germline genomes have been profoundly modified during evolution, providing unprecedented examples of germline DNA malleability. Although the significance of the modifications and malleability is unclear, they may reflect the evolution of mechanisms that facilitate evolution. Because of the modifications, these ciliates must perform remarkable feats of cutting, splicing, rearrangement and elimination of DNA sequences to convert the chromosomal DNA in the germline genome (micronuclear genome) into gene-sized DNA molecules in the somatic genome (macronuclear genome). How these manipulations of DNA are guided and carried out is largely unknown. However, the organization and manipulation of ciliate DNA sequences are new phenomena that expand a general appreciation for the flexibility of DNA in evolution and development.

Animals↗
PubMed2003

Intrathecal B-cell clonal expansion, an early sign of humoral immunity, in the cerebrospinal fluid of patients with clinically isolated syndrome suggestive of multiple sclerosis.

The development of somatically mutated memory and plasma B cells is a consequence of T cell-dependent antigen-challenged humoral immunity. To investigate the role of B cell-mediated humoral immunity in the initiation and evolution of multiple sclerosis (MS), we analyzed Ig variable heavy chain genes of intrathecal B cells derived from patients with a first clinical manifestation suggestive of MS. Sequences of Ig variable regions showed that B cells in the cerebrospinal fluid from most of these patients were clonally expanded and carried somatic hypermutated variable heavy chain genes. The mutations showed a high replacement-to-silent ratio and were distributed in a way suggesting that these clonally expanded B cells had been positively selected through their antigen receptor. In comparison, intrathecal B-cell clonal expansion often precedes both oligoclonal IgG bands and multiple magnetic resonance imaging lesions. Clinical follow-up study showed that patients with clonally expanded intrathecal B cells had a high rate of conversion to clinically definite MS. The findings provide direct evidence of recruitment of germinal center differentiated B lymphocytes into the central nervous system during the initiation of MS. These results indicate B cell-mediated immune response in the cerebrospinal fluid is an early event of inflammatory reaction in the central nervous system of MS. This procedure also provides a more sensitive method to evaluate the association of humoral immunity in the evolution of MS.

Adult↗
PubMed2001

Point mutation in essential genes with loss or mutation of the second allele: relevance to the retention of tumor-specific antigens.

Antigens that are tumor specific yet retained by tumor cells despite tumor progression offer stable and specific targets for immunologic and possibly other therapeutic interventions. Therefore, we have studied two CD4(+) T cell-recognized tumor-specific antigens that were retained during evolution of two ultraviolet-light-induced murine cancers to more aggressive growth. The antigens are ribosomal proteins altered by somatic tumor-specific point mutations, and the progressor (PRO) variants lack the corresponding normal alleles. In the first tumor, 6132A-PRO, the antigen is encoded by a point-mutated L9 ribosomal protein gene. The tumor lacks the normal L9 allele because of an interstitial deletion from chromosome 5. In the second tumor, 6139B-PRO, both alleles of the L26 gene have point mutations, and each encodes a different tumor-specific CD4(+) T cell-recognized antigen. Thus, for both L9 and L26 genes, we observe "two hit" kinetics commonly observed in genes suppressing tumor growth. Indeed, reintroduction of the lost wild-type L9 allele into the 6132A-PRO variant suppressed the growth of the tumor cells in vivo. Since both L9 and L26 encode proteins essential for ribosomal biogenesis, complete loss of the tumor-specific target antigens in the absence of a normal allele would abrogate tumor growth.

Alleles↗
PubMedDate not supplied

Possible effect of a sex chromosome on reproductive performance in Columbidae.

In comparison with the reproductive performance of matings within Streptopelia risoria, the species hybrid males, from matings to S. risoria of males of S. chinensis or S. senegalensis, displayed increased infertility, but not an increase of embryo mortality. Previous findings of a high percentage of sperm abnormalities provide a basis that explains in part the infertility of the species hybrid males. The infertility and embryo mortality of both kinds of species hybrid females, the heterogametic sex, was much higher than in the S. risoria X S. risoria matings. The reproductive performance of the backcross females of the first, second and third backcross generations, having either species hybrid or backcross hybrid males as parents, could be divided into two classes, differing significantly either in percentage of infertility or embryo mortality, or in both categories. The backcross females producing the lower reproductive performance presumably carried the X chromosome of the wild parental species. Limited date obtained following a mating between a S. senegalensis female and a S. chinensis male showed a very low percentage of infertility of eggs from two species hybrid females and a backcross female (1/4-S. chinensis), indicating that the adverse effect of changes affecting infertility, presumably on the X-chromosome of these two wild species, towards S. risoria, had occurred in parallel during their evolution. The genetic changes affecting embryo mortality, and particularly the death of the squabs before becoming adults, are located on somatic chromosomes.

Animals↗
PubMed2005

Innate immunity: New approaches to understanding its clinical significance.

Immunologists view innate immunity as evolution's ancient host response to infectious agents. Unlike vertebrates, in which antibodies and T-cell subsets rely on somatic mutations, molecular participants of innate immunity are encoded in the genome. Despite its heritage, many of innate immunity's sentinel molecules, intracellular transcriptional controls, and effector molecules participate in the pathogenesis of numerous complex human diseases. Toll-like receptors (TLRs), an important starting point, contact the environment and provide specific sensing for an important component of innate immunity. TLRs, found on macrophages, dendritic cells, and endothelial cells, recognize specific microbial molecular patterns. Beginning with these sentinel molecules, the process leads through intracytoplasmic mediators of transcription control and culminates with an array of host immune responses. Effector molecules include cytokines and the complement system. Polymorphisms within TLR genes might contribute to the pathogenesis of complex diseases. Disease associations linked to single nucleotide polymorphisms are in the early stage of experimental discovery; important clinical insights are emerging. Along these lines, studies of asthma provide an excellent example of how ancient ligand-receptor interactions and TLR polymorphisms provide new understanding of a common disease. New knowledge could facilitate the development of novel therapies.

Asthma↗
PubMed1997

Alteration of testicular response to long photoperiod by transient exposure to short photoperiod in collared lemmings (Dicrostonyx groenlandicus).

The reproductive response of collared lemmings (Dicrostonyx groenlandicus) to photoperiod is unique for rodents. Whereas most reproductively photoresponsive rodents show maximal gonadal growth when exposed to long photoperiod (long day), collared lemmings show delayed maturation when born and maintained under this condition. However, transfer of lemmings from short photoperiod (short day) to long day results in maximal gonadal growth, indicating that the response to long day depends upon photoperiod history. We hypothesized that the slowing of maturation observed in animals born and maintained on long day reflects an inability to respond fully to long day, resulting from the absence of previous exposure to short day. To determine whether young lemmings born in long day are capable of being stimulated by long day, we exposed them at weaning (19 days of age) to 1, 6 or 10 weeks of short day, and then challenged them with a second exposure to long day. Relative to animals transferred permanently to short day at weaning, lemmings exposed to 6 weeks of short day showed accelerated gonadal growth after both 5 and 10 weeks of subsequent exposure to long day, and those exposed to 10 weeks of short day had larger testes after 6 weeks of long day. Thus, during transient exposure to short day, the animals acquired sensitivity to the stimulatory effects of long day. The responses of body mass, bifid claw width and pelage colour to the photoperiod manipulations did not parallel that of the gonads, indicating independent regulation of somatic and reproductive parameters. The unique way in which the reproductive system of collared lemmings responds to photoperiod may reflect evolution in an environment where the production of offspring during periods of unchanging long day (for example, the Arctic summer) is not selectively advantageous.

Animals↗
PubMed2006

Two unlinked double-strand breaks can induce reciprocal exchanges in plant genomes via homologous recombination and nonhomologous end joining.

Using the rare-cutting endonuclease I-SceI we were able to demonstrate before that the repair of a single double-strand break (DSB) in a plant genome can be mutagenic due to insertions and deletions. However, during replication or due to irradiation several breaks might be induced simultaneously. To analyze the mutagenic potential of such a situation we established an experimental system in tobacco harboring two unlinked transgenes, each carrying an I-SceI site. After transient expression of I-SceI a kanamycin-resistance marker could be restored by joining two previously unlinked broken ends, either by homologous recombination (HR) or by nonhomologous end joining (NHEJ). Indeed, we were able to recover HR and NHEJ events with similar frequencies. Despite the fact that no selection was applied for joining the two other ends, the respective linkage could be detected in most cases tested, demonstrating that the respective exchanges were reciprocal. The frequencies obtained indicate that DSB-induced translocation is up to two orders of magnitude more frequent in somatic cells than ectopic gene conversion. Thus, DSB-induced reciprocal exchanges might play a significant role in plant genome evolution. The technique applied in this study may also be useful for the controlled exchange of unlinked sequences in plant genomes.

Base Sequence↗
PubMedDate not supplied

The late complications of diabetes mellitus.

Late complications of diabetes mellitus include a variety of clinical pictures, mainly related to the involvement of the arterial wall both of large vessels (macroangiopathy) and small vessels (microangiopathy), and of the peripheral nervous system (neuropathy). Their presence in almost all types of diabetes indicates that there is a common pathogenetic mechanism, which can be substantially identified in high blood glucose levels and related alterations. Hyperglycemia, in fact, leads to some metabolic abnormalities, i.e. non-enzymatic glycosylation of proteins and polyol pathway activity; moreover it can negatively affect the pattern of some hormones, especially GH and sex steroids, and normal rheological and clotting properties of blood. These abnormalities, confirmed by experimental models, play a key role in the development of late diabetic complications. However some evidence indicates that a genetic background may predispose to their development or protect from their onset. The two main forms of diabetic retinopathy, non-proliferative and proliferative, show an incidence which increases with age and duration of diabetes, reaching 100% when diabetes lasts for more than 20 years. The risk of blindness, which is very high for the proliferative form, has been dramatically reduced by laser-photocoagulation. Diabetic nephropathy affects a lesser number of diabetics but, after a silent or preclinical stage, leads to renal failure and subsequent replacement therapy. Strict metabolic control in the silent stage and later rigid anti-hypertensive treatment can prevent or retard the evolution of this complication. A close association has been observed between diabetes and hypertension, which can directly affect the onset and evolution of diabetic nephropathy, probably through a common genetic mechanism. Diabetic neuropathy has a wide variety of clinical manifestations, at somatic, autonomic and central levels and can greatly modify the quality and expectancy of life. However, the major cause of death in diabetic subjects is large vessel disease or macroangiopathy, which is similar to non-diabetic atherosclerosis regarding the main histopathological and clinical manifestations but has a much higher prevalence and severity. Finally, a specific cardiomyopathy has also been described in diabetes mellitus and can account for the high rate of heart failure observed in these patients.

Aged↗
PubMed1994

Genomic instability of microsatellite repeats and its association with the evolution of chronic myelogenous leukemia.

Tumorigenesis has been shown to proceed through a series of genetic alterations involving protooncogenes and tumor-suppressor genes. Investigation of genomic instability of microsatellites has indicated a new mechanism for human carcinogenesis in hereditary nonpolyposis colorectal cancer and sporadic cancer and this instability has been shown to be related to inherited predisposition to cancer. This study was conducted to determine whether such microsatellite instability is associated with the evolution of chronic myelogenous leukemia (CML) to the blast crisis. Nineteen CML patients clinically progressing from the chronic phase to accelerated phase or blast crisis and 20 other patients in the CML chronic phase were studied. By polymerase chain reaction assay, DNAs for genomic instability in five separate microsatellites in chromosome arms 5q (Mfd27), 17p (Mfd41), 18q (DCC), 3p (CI3-9), and 8p (LPL) were examined. Differences in unrelated microsatellites of chronic and blastic phase DNAs in 14 of 19 patients (73.7%) were demonstrated. Somatic instability in five microsatellites, Mfd27, Mfd41, DCC, CI3-9, and LPL, was detected in 2 of 19 (10.5%), 8 of 19 (42.1%), 11 of 19 (57.9%), 4 of 17 (23.5%), and 4 of 17 (23.5%) cases. In 10 of 19 cases (52.6%), genetic instability in at least two of five microsatellites was observed and was categorized as replication error (RER+) phenotype. CML evolution cases with myeloid, lymphoid, and mixed phenotypes and the blast crisis and accelerated phase showed somatic instability in a number of microsatellites. No alterations in leukemic cells at the chronic phase could be detected in any microsatellites. These data indicate instability of microsatellites (RER+) but not familial predisposition to possibly be a late genetic event in the evolution of CML to blast crisis. In the microsatellite of the DCC gene, complicated alterations in band patterns caused by instability as well as loss of heterozygosity (LOH) were observed in 13 of 19 cases (68.4%): instability in 9 cases, instability plus LOH in 2 cases, and only LOH in 2 cases. These highly frequent alterations in microsatellites, including instability and LOH, suggesting that secondary events due possibly to loss of fidelity in replication and repair machinery may be significantly associated with CML evolution.

Adult↗