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PubMed1989

Genetic and molecular characterization of a-mrh-Mrh, a new mutable system of Zea mays.

A new allele of the maize A1 gene, a gene required for anthocyanin pigment biosynthesis, was identified in a genetic stock exhibiting a high frequency of chromosome breakage at the second microspore mitosis. This allele, a-mrh, is unstable in both somatic and germinal tissue when an independent locus, Mrh, is present in the genome. a-mrh was molecularly cloned, and a 246 bp DNA insertion with characteristics of a transposable element was identified within the fourth exon of the gene. Southern blot analysis of germinal derivatives of a-mrh suggests that the DNA insert rMrh is excised from the locus when a wild-type phenotype is restored. Genetic crosses with components of other two-element mutable systems of maize failed to induce mutability. We therefore conclude that rMrh is a member of a new, two-element transposon system of maize. The genetic and molecular characteristics of the elements involved are discussed with respect to stress-activated transposition, response of an element to developmental signals, and a possible new role of plant transposons in gene evolution.

Alleles↗
PubMed1993

Conservation and divergence of patterns of expression and lineage-specific transcripts in orthologues and paralogues of the mouse Hox-1.4 gene.

A possible correlation between the structural organization of homeobox-containing genes and their cell-specific expression was examined in studies determining similarities and differences in the expression patterns of orthologues and paralogues of the murine Hox-1.4 gene. We first compared the expression pattern of members of the Hox-1.4 subfamily, Hox-2.6 and Hox-4.2, in the adult mouse testis. Although these three evolutionarily related genes exhibited similar anterior limits of expression in the embryonic central nervous system, their cellular specificity of expression was very different in the adult testis. Hox-1.4 was abundantly expressed only in the germ cells; Hox-2.6 was expressed at very low levels in both spermatogenic cells and somatic cells; and Hox-4.2 transcripts appeared to be restricted to the somatic cells. We next analyzed the expression of several of the Hox-1.4 orthologues in the mouse testis to determine if other members of the Hox-1 cluster are involved in the male germ cell differentiation pathway. We showed that the two adjacent genes of Hox-1.4, Hox-1.3 and Hox-1.5, are expressed in the germ line but at lower levels. Further, both Hox-1.3 and Hox-1.4 produced unique, germ line-specific transcripts as compared to other adult tissues and the Day 12.5 embryo.

Animals↗
PubMed1990

Genomic analysis of sequence variation in tandemly repeated DNA. Evidence for localized homogeneous sequence domains within arrays of alpha-satellite DNA.

As a model to examine the local distribution of sequence variation within large arrays of tandemly repeated DNA in complex genomes, the long-range organization of alpha-satellite DNA from human chromosome 17 was investigated. Three individual chromosomes, representing different alpha-satellite haplotypes, were segregated into mouse and human somatic cell hybrids and their arrays sized by pulse-field gel electrophoresis. An inventory of the higher-order repeat units found in multiple separate regions of these megabase arrays was obtained using cosmid mapping and two-dimensional gel electrophoresis, a technique that combines the large-scale resolution of pulsed-field gel electrophoresis with the small-scale resolution of conventional gel electrophoresis. These analyses show that alpha-satellite arrays are characterized by the presence of localized homogeneous domains containing only one distinct type of repeat unit. These domains, which consist of sequence variants and/or higher-order repeat length variants, can be up to at least several hundred thousands of bases in length. Both abundant and rare variant repeat units can be localized in these distinct domains, which may correspond to transition states in the evolution of tandem multicopy DNA families. This description of the organization of large arrays of tandem repeats provides insight into mechanisms involved in their homogenization.

Amino Acid Sequence↗
PubMed1989

Human and mouse amelogenin gene loci are on the sex chromosomes.

Enamel is the outermost covering of teeth and is the hardest tissue in the vertebrate body. The enamel matrix is composed of enamelin and amelogenin classes of protein. We have determined the chromosomal locations for the human and mouse amelogenin (AMEL) loci using Southern blot analyses of DNA from human, mouse, or somatic cell hybrids by hybridization to a characterized mouse amelogenin cDNA. We have determined that human AMEL sequences are located on the distal short arm of the X chromosome in the p22.1----p22.3 region and near the centromere on the Y chromosome, possibly at the proximal long arm (Yq11) region. These chromosomal assignments are consistent with the hypothesis that perturbation of the amelogenin gene is involved in X-linked types of amelogenesis imperfecta, as well as with the Y-chromosomal locations for genes that participate in regulating tooth size and shape. Unlike the locus in humans, the mouse AMEL locus appears to be assigned solely to the X chromosome. Finally, together with the data on other X and Y chromosome sequences, these data for AMEL mapping support the notion of a pericentric inversion occurring in the human Y chromosome during primate evolution.

Amelogenin↗
PubMed1989

The "psychosomatic family" model: an empirical and theoretical analysis.

Evolution of the Family Systems Paradigm has been constrained by the dichotomy between theory building and empirical research. This article integrates these two domains by presenting a theoretical analysis of the "psychosomatic family" model as it informs and is informed by an empirical research project. Forty families of children with Crohn's disease (CD), ulcerative colitis (UC), and functional recurrent abdominal pain syndrome (RAP) were rated during standard, videotaped family interaction tasks, lunch, and interview. Laboratory scores of disease activity were associated with triangulation, marital dysfunction, and total "psychosomatic family" scores. Disease activity was not significantly correlated with enmeshment, overprotection, rigidity, conflict avoidance, or poor conflict resolution. Thus, the marital/triangulation and enmeshment/overprotection/conflict clusters may be subcomplexes of the "psychosomatic family" complex. CD, UC, and RAP groups differed in the relations among particular family patterns and disease activity. A heuristic family-psycho-somatic model is presented to facilitate future research.

Abdominal Pain↗
PubMed1992

Interrelating B cell subpopulations and environmental regulation with the expression of three tiers of repertoire diversity.

The B cell repertoire consists of three tiers of clonotype diversity. One tier, which is the product of H chain V region rearrangements in the absence of N additions, is of limited diversity (less than 10(8) clonotypes) so that clonotypes of this tier would be expected to recur within and among B cells of individuals of an inbred strain. These clonotypes, therefore, could be subjected to, and conserved by, evolutionary selective pressures such as those imposed by ubiquitous bacterial pathogens. The second tier of clonotypes is created by H chain V region rearrangements that include N additions, and is, therefore, exceedingly diverse. Clonotypes of this tier would be unlikely to recur; however, by providing maximal diversity they would ensure protection against a wide spectrum of pathogens. The third tier of diversity is that which is generated by the superimposition of somatic mutations on clonotypes of the other two tiers. This tier of clonotypes is reflective of the refinement of specificities that are destined for expression in memory B cells. B cells exists as three distinct subpopulations, Ly-1 B cells, conventional primary B cells and memory B cells. These subpopulations differ functionally, developmentally, and by the extent to which they are impacted by immunoregulatory processes. Furthermore, B cells of these subpopulations differentially express the three tiers of clonotype diversity.

Animals↗
PubMed2004

Distribution of choline acetyltransferase and NADPH diaphorase in the spinal cord of the pigeon.

Acetylcholine is the neurotransmitter of somatic and autonomic motor systems of the spinal cord. However, there are also intrinsic cholinergic systems which have modulatory functions. Modulatory functions have also been assigned to nitric oxide (NO). Acetylcholine is synthesized by choline acetyltransferase and NO by nitric oxide synthase, which is a NADPH diaphorase. The distribution of both enzymes in the mammalian spinal cord is well known. However, there is a lack of comparative data in avian species. Therefore, the distribution of both enzymes in the spinal cord of the pigeon was studied using histochemical and immunohistochemical methods. Aside from somatic motor neurons and autonomic preganglionic neurons choline acetyltransferase-immunoreactivity was found throughout the spinal cord in lamina III of the superficial dorsal horn and near the central canal. The location of choline acetyltransferase-positive preganglionic neurons in the centrally located column of Terni and the lack of an intermediolateral column typical of the mammalian spinal cord can be confirmed. In lumbosacral segments the axons of centrally located cholinergic neurons crossed to the contralateral side to form a tract in the ventral funiculus, which then innervates the contralateral grey substance. A dense band of NADPH diaphorase staining was found in lamina II and in centrally located neurons of all segments. Part of the centrally located neurons double-labelled for choline acetyltransferase and NADPH diaphorase. In contrast to mammals, preganglionic neurons labelled only weakly for NADPH diaphorase. Altogether, despite the divergent evolution of both classes of vertebrate intrinsic modulatory choline acetyltransferase and NADPH diaphorase systems of birds seem to be largely similar to those of the mammalian spinal cord.

Animals↗
PubMed1982

Cytogerontology since 1881: a reappraisal of August Weismann and a review of modern progress.

Cytogerontology, the science of cellular ageing, originated in 1881 with the prediction by August Weismann that the somatic cells of higher animals have limited division potential. Weismann's prediction was derived by considering the role of natural selection in regulating the duration of an organism's life. For various reasons, Weismann's ideas on ageing fell into neglect following his death in 1914, and cytogerontology has only reappeared as a major research area following the demonstration by Hayflick and Moorhead in the early 1960s that diploid human fibroblasts are restricted to a finite number of divisions in vitro. In this review we give a detailed account of Weismann's theory, and we reveal that his ideas were both more extensive in their scope and more pertinent to current research than is generally recognised. We also appraise the progress which has been made over the past hundred years in investigating the causes of ageing, with particular emphasis being given to (i) the evolution of ageing, and (ii) ageing at the cellular level. We critically assess the current state of knowledge in these areas and recommend a series of points as primary targets for future research.

Adaptation, Biological↗
PubMed2003

Genomic analysis of immunity in a Urochordate and the emergence of the vertebrate immune system: "waiting for Godot".

Genome-wide sequence analysis in the invertebrate chordate, Ciona intestinalis, has provided a comprehensive picture of immune-related genes in an organism that occupies a key phylogenetic position in vertebrate evolution. The pivotal genes for adaptive immunity, such as the major histocompatibility complex (MHC) class I and II genes, T-cell receptors, or dimeric immunoglobulin molecules, have not been identified in the Ciona genome. Many genes involved in innate immunity have been identified, including complement components, Toll-like receptors, and the genes involved in intracellular signal transduction of immune responses, and show both expansion and unexpected diversity in comparison with the vertebrates. In addition, a number of genes were identified which predicted integral membrane proteins with extracellular C-type lectin or immunoglobulin domains and intracellular immunoreceptor tyrosine-based inhibitory motifs (ITIMs) and immunoreceptor tyrosine-based activation motifs (ITAMs) (plus their associated signal transduction molecules), suggesting that activating and inhibitory receptors have an MHC-independent function and an early evolutionary origin. A crucial component of vertebrate adaptive immunity is somatic diversification, and the recombination activating genes (RAG) and activation-induced cytidine deaminase (AID) genes responsible for the Generation of diversity are not present in Ciona. However, there are key V regions, the essential feature of an immunoglobulin superfamily VC1-like core, and possible proto-MHC regions scattered throughout the genome waiting for Godot.

Animals↗
PubMed1991

An X-linked zinc finger gene mapping to Xq21.1-q21.3 closely related to ZFX and ZFY: possible origins from a common ancestral gene.

We describe a new zinc finger gene sequence (CMPX1 or HGM symbol ZNF6; isolated by cross-hybridization of ZFY to clones in a testis cDNA library) which possesses a zinc finger domain closely related to the transcriptional activator gene ZFX. The putative acidic activation domain is only 11.5% homologous with ZFX, whereas the putative DNA binding domain shares 75% homology and shows the same organisation composed of a basic two fingered repeat unit. ZNF6 has an unusually large 5' untranslated region (UTR) of 1.2 Kb which contains 26 potential ATG initiation codons, only one of which is associated with a long open reading frame. Southern and Northern blot analysis has shown that this 5' UTR is shared with many other sequences in the genome and transcribed associated with a large range of mRNA species. In situ hybridisation, analysis of somatic cell hybrids and male individuals carrying deleted X chromosomes have mapped the gene to Xq21.1-q21.3. The gene is highly conserved amongst the primates, in the mouse and can be detected weakly in the genome of a metatherian mammal (possum). Dosage in male and female mice indicates that it is also X-linked in this species. Possible origins of ZFX, ZFY and CMPX1 from a common ancestral gene are discussed.

Amino Acid Sequence↗
PubMed1995

A panel of subchromosomal painting libraries representing over 300 regions of the human genome.

DNA samples from about 100 human-hamster somatic cell hybrids, previously characterized by conventional banding techniques, were amplified with dual-Alu PCR. The products were then used as probes in FISH experiments on normal human metaphases for an accurate cytogenetic characterization of the human material retained in each hybrid. In addition to entire chromosomes, most hybrids were found to contain one or a few chromosome fragments, as a result of rearrangements that had occurred in vitro. Forty additional primary hybrids, in which conventional cytogenetic analysis failed to reveal any complete human chromosome, contained many human chromosome fragments. More than 300 chromosome fragments were scored and their precise chromosomal location recorded. We show data indicating that subchromosomal painting libraries generated from these hybrids can be favorably used in the fine characterization of chromosomal rearrangements encountered in clinical cytogenetics or in tumor cytogenetics, and in tracking chromosomal changes that occurred in primate evolution.

Animals↗
PubMed1995

Genetic alterations associated with the evolution and progression of astrocytic brain tumours.

Diffusely infiltrating low-grade astrocytomas (WHO grade II) have an intrinsic tendency for progression to anaplastic astrocytoma (WHO grade III) and glioblastoma (WHO grade IV). This change is due to the sequential acquisition of genetic alterations, several of which have recently been identified. In low-grade astrocytomas, p53 mutations with or without loss of heterozygosity on chromosome 17p are the principal detectable change. Anaplastic astrocytomas contain p53 mutations at an overall incidence of 34% and, in addition, loss of heterozygosity on chromosome 19q and frequent homozygous deletion of the p16 tumor suppressor (MTS-1) gene. The most malignant astrocytic neoplasms, the glioblastoma, further shows loss of chromosome 10 and amplification of the epidermal growth factor receptor (EGF-R) gene at overall incidences of 66% and 34%, respectively. The type and distribution of p53 mutations in astrocytic brain tumours are not suggestive of specific environmental carcinogens operative in their aetiology. Analysis of 91 families with p53 germline mutations reported to date show that tumours of the nervous system account to 12% of all neoplasms. Of a total of 57 brain tumours reported, 30 were classified histologically and of these, 73% were of astrocytic origin. The observation that somatic p53 mutations in sporadic brain tumours are largely restricted to those of astrocytic origin and that astrocytomas also prevail among CNS neoplasms associated with p53 germline mutation strongly suggests, that p53 mutations are capable of initiating neoplastic transformation in astrocytes of the human nervous system.

Adult↗
PubMed2006

Caspase function in programmed cell death.

The first proapoptotic caspase, CED-3, was cloned from Caenorhabditis elegans in 1993 and shown to be essential for the developmental death of all somatic cells. Following the discovery of CED-3, caspases have been cloned from several vertebrate and invertebrate species. As reviewed in other articles in this issue of Cell Death and Differentiation, many caspases function in nonapoptotic pathways. However, as is clear from the worm studies, the evolutionarily conserved role of caspases is to execute programmed cell death. In this article, I will specifically focus on caspases that function primarily in cell death execution. In particular, the physiological function of caspases in apoptosis is discussed using examples from the worm, fly and mammals.

Animals↗
PubMed1995

Evolution of cortical responsiveness subsequent to multiple forelimb nerve transections: an electrophysiological study in adult cat somatosensory cortex.

Multiunit recordings along mediolateral rows in the primary somatosensory cortex of the animals described by C. Avendaño, D. Umbriaco, R.W. Dykes, and L. Descarries (1995, J. Comp. Neurol. 354:321-332) provided information about the functional status of the regions in and near the deafferented cortex. Responses changed along this axis from normally organized receptive fields in the hindlimb representation through a transition zone of unusually small receptive fields into the clearly deafferented forelimb representation, where receptive fields were uncommon and often had unusual characteristics. The most abrupt change along this axis was the appearance of a repetitive, bursting discharge pattern in the multiunit activity near the border of the deprived cortex. The appearance of this pattern was used as a reference to describe differences between normal and deprived cortices. The nature of these differences evolved with time. Much of the deprived cortex lacked identifiable receptive fields for months after the nerve transections and, 1 year later, still only about half of the recording sites within the deprived region displayed organized receptive fields. Some sites within the deprived region lacking definable receptive fields could be excited at long latencies by somatic stimuli anywhere on the body. With time, regions of normal cortex near the border with the deprived zone became more involved in these processes. Spontaneous activity and thresholds also changed with time in both normal and deprived cortices.(ABSTRACT TRUNCATED AT 250 WORDS)

Afferent Pathways↗
PubMed2000

Natural antibodies and the host immune responses to xenografts.

Natural antibodies are present in the serum of individuals in the absence of known antigenic stimulation. These antibodies are primarily IgM, polyreactive, and encoded by immunoglobulin V genes in germline configuration. Natural antibodies are produced by B-1 lymphocytes, cells that form the primary cell of the fetal and newborn B cell repertoire and may represent the basic foundation upon which the adult repertoire of B cell antibodies is based. Natural antibodies react with a variety of endogenous and exogenous antigens, including xenoantigens expressed by tissues between unrelated species. These antibodies are capable of causing the immediate rejection of grafts exchanged across species barriers. One of the central issues related to our understanding of the immunopathologic mechanisms responsible for rejection of xenografts is whether pre-formed natural antibodies and new antibodies induced following xenotransplantation are produced by the same pathways of B cell antibody production. We have established in studies conducted in rodents and humans that the initial phases of antibody production xenogeneic tissues involves the use of a restricted population of Ig germline genes to encode xenoantibody binding. As the humoral xenoantibody response matures, the same closely-related groups of Ig V genes are used to encode antibody binding and there is evidence for an isotype switch to IgG antibody production and the appearance of somatic mutations consistent with antigen-driven affinity maturation. Our findings in both rodent and human studies form the basis for our proposal that the xenograft response reflects the use of B cell natural antibody repertoires originally intended to provide protection against infection. The host humoral response is inadvertently recruited to mount antibody responses against foreign grafts because they display carbohydrate antigens that are shared by common environmental microbes. This model of xenoantibody responses is being tested in our laboratory through the analysis of the binding of xenoantibodies in their original non-mutated configuration, and the examination of the effect of specific point mutations and gene shuffling have on xenoantibody binding activity. Establishment of the relationships between Ig structural changes and subsequent changes in binding affinity should provide important insights into the role that, natural antibodies and the cells that produce them play in the evolution of the host's humoral responses to xenografts.

Animals↗
PubMed1989

Alterations in immunoglobulin genes reveal the origin and evolution of monotypic and bitypic B cell lymphomas.

During progression of B-lymphoproliferative disorders (B-LPD), increasing divergence can be detected in histology, cytogenetics, and clinical behavior. To investigate genomic tumor cell heterogeneity, 50 biopsies of 21 patients with B-LPD of different histogenetic origin were studied for changes in the immunoglobulin gene structure during follow-up study. Ig-heavy chain (IgH) gene alterations were analyzed by Southern blotting using a panel of eight endonucleases. Ig-light chain (IgL) genes and the translocation of the bc 1-2 gene involved in t(14;18) were also studied. In seven of nine follicular lymphomas, most alterations suggested mutations in the IgH genes. Conservation of most restriction sites and of the t(14; 18) breakpoint confirmed the monoclonal origin in these tumors. Also, in two of three diffuse follicle center cell lymphomas (CLL) and in each of four immunocytomas, IgH alterations were found. In contrast, clonal changes were absent in three centrocytic lymphomas and two cases of CLL. In two follicular lymphomas with bitypic IgL expression, a common origin with subsequent divergence of the two constituents, rather than true biclonality, was indicated by the Ig gene structures. No relation was found between the frequency of somatic mutations and histologic signs of progression. These data indicate that somatic hypermutation in IgH genes is related to the histogenesis of the B-LPD and reflect the physiology of their benign counterparts in normal B cell development.

B-Lymphocytes↗
PubMed2005

High genetic diversity and clonal growth in relict populations of Olea europaea subsp. laperrinei (Oleaceae) from Hoggar, Algeria.

BACKGROUND AND AIMS: The Laperrine's olive (Olea europaea subsp. laperrinei) is an endemic tree from Saharan massifs. Its populations have substantially regressed since the Pleistocene and are presently distributed in a fragmented habitat. Long-term persistence of this taxon is uncertain and programmes of preservation have to be urgently implemented. To define a conservation strategy, the genetic diversity and breeding system of this tree have to be investigated. METHODS: One hundred and eleven ramets were prospected in the laperrinei populations from the Tamanrasset region, southern Algeria. Genetic polymorphism was revealed at nuclear and chloroplast DNA (cpDNA) microsatellite loci allowing a comparative assessment of the genetic diversity of laperrinei and Mediterranean populations based on bi-parental and maternal markers. Additionally, nuclear microsatellite markers enabled the genotypes to be identified unambiguously. KEY RESULTS: Based on nuclear microsatellite data, the total diversity was high (Ht=0.61) in laperrinei populations and similar to that observed in western Mediterranean populations. A substantial cpDNA diversity (Ht=0.19) was also observed. Genetically identical ramets originated from the same stump (which can cover >80 m2) were identified in each population. Sixteen per cent of genets exhibited more than one ramet. In addition, several cases of somatic mutations were unambiguously revealed in distinct ramets stemming from the same stump. CONCLUSIONS: These data show that highly isolated and small laperrinei populations are able to maintain a high genetic diversity. This supports the existence of relict trees persisting for a very long time (probably since the last humid transition, 3000 years ago). It is proposed that the very long persistence associated with an asexual multiplication of highly adapted trees could be a strategy of survival in extreme conditions avoiding a mutational meltdown due to reproduction in reduced populations.

Algeria↗
PubMedDate not supplied

The concept of somatization as a cultural and historical product of Western medicine.

Somatization is handled as a concept that plays an important role in the contemporary clinical theory and practice of psychiatry and general medicine. A distinct biomedical epistemology and model of illness underlies use of the concept and gives it meaning. First, the nature of the assumptions about the medical problems described by the concept are outlined. Then, some of the cultural and historical aspects of Western medical history that shaped the concept and its epistemology are reviewed. The concept is seen to arise as a consequence of the development of the modern ontological view of disease, the shift in the role ascribed to the nervous system and theoretical developments involving the explanation of psychoses through a descriptive language of psychopathology and bodily states. A discussion of non-Western perspectives of illness is pursued in order to highlight the differences in the conditions that led to the evolution of the concept in Western medicine. Some of the theoretical quandaries associated with the concept are briefly reviewed.

Cross-Cultural Comparison↗