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PubMed2002

The evolution of fungus-growing termites and their mutualistic fungal symbionts.

We have estimated phylogenies of fungus-growing termites and their associated mutualistic fungi of the genus Termitomyces using Bayesian analyses of DNA sequences. Our study shows that the symbiosis has a single African origin and that secondary domestication of other fungi or reversal of mutualistic fungi to a free-living state has not occurred. Host switching has been frequent, especially at the lower taxonomic levels, and nests of single termite species can have different symbionts. Data are consistent with horizontal transmission of fungal symbionts in both the ancestral state of the mutualism and most of the extant taxa. Clonal vertical transmission of fungi, previously shown to be common in the genus Microtermes (via females) and in the species Macrotermes bellicosus (via males) [Johnson, R. A., Thomas, R. J., Wood, T. G. & Swift, M. J. (1981) J. Nat. Hist. 15, 751-756], is derived with two independent origins. Despite repeated host switching, statistical tests taking phylogenetic uncertainty into account show a significant congruence between the termite and fungal phylogenies, because mutualistic interactions at higher taxonomic levels show considerable specificity. We identify common characteristics of fungus-farming evolution in termites and ants, which apply despite the major differences between these two insect agricultural systems. We hypothesize that biparental colony founding may have constrained the evolution of vertical symbiont transmission in termites but not in ants where males die after mating.

Animals↗
PubMed2005

Oral cancer prevention and the evolution of molecular-targeted drug development.

The multifaceted rationale for molecular-targeted prevention of oral cancer is strong. Oral cancer is a major global threat to public health, causing great morbidity and mortality rates that have not improved in decades. Oral cancer development is a tobacco-related multistep and multifocal process involving field carcinogenesis and intraepithelial clonal spread. Biomarkers of genomic instability, such as aneuploidy and allelic imbalance, can accurately measure the cancer risk of oral premalignant lesions, or intraepithelial neoplasia (IEN). Retinoid-oral IEN studies (eg, of retinoic acid receptor-beta, p53, genetic instability, loss of heterozygosity, and cyclin D1) have advanced the overall understanding of the biology of intraepithelial carcinogenesis and of preventive agent molecular mechanisms and targets-important advances for monitoring preventive interventions and assessing cancer risk and pharmacogenomics. Clinical management of oral IEN varies from watchful waiting to complete resection, although complete resection does not prevent oral cancer in high-risk patients. New approaches, such as interventions with molecular-targeted agents and agent combinations in molecularly defined high-risk oral IEN patients, are urgently needed to reduce the devastating worldwide consequences of oral cancer.

Aneuploidy↗
PubMed1992

DNA ploidy and karyotype in recurrent and metastatic soft tissue sarcomas.

To study mechanisms involved in evolution of soft tissue sarcomas, we compared DNA ploidy and karyotypes at different stages of their disease in two patients with myxoid liposarcomas (MLS), one with a fibrosarcoma (FS), and two with rhabdomyosarcomas (RMS). None of the MLS samples revealed clearcut histologic changes in later samples as compared to their primaries, and the DNA ploidy in all samples was diploid. In one patient karyotypes at four different times during the 19 yr of his disease all revealed a t(11;12) (p15;q13), but additional clonal chromosomal abnormalities occurred only in later recurrences. In another patient the karyotypes obtained in the 26th and 28th yr of his disease were similar and included the t(12;16) (q13;p11), characteristic of MLS. A comparison with karyotypes of six other MLS patients at different disease stages suggests that the presence of a t(12;16) may correlate with less aggressive clinical behavior. The histology of the FS remained low-grade and the DNA ploidy diploid. The karyotype, however, showed evolution. In both MLS and FS, chromosomal changes thus seem to be a more sensitive marker for tumor progression than histologic changes or DNA ploidy. In one embryonal RMS, karyotypes obtained 7 and 11 yr after the primary diagnosis were different but clearly had a common "progenitor." In one alveolar RMS, the primary and the synchronous lung and lymph node metastases all revealed a t(2;13). The findings in RMS suggest that polyploidization is an early event in tumor evolution, especially in the alveolar subtype, which may be followed by additional chromosomal changes. In addition, DNA ploidy was measured in eight other RMSs. Among the RMSs the embryonal subtype was characterized by DNA aneuploidy, whereas three of the alveolar cases were in the tetraploid range and one was peridiploid. In local recurrences and in metastases changes in DNA index were observed in half the cases.

Adolescent↗
PubMed2004

Displaying the relatedness among isolates of bacterial species -- the eBURST approach.

Determining the most appropriate way to represent the relationships between bacterial isolates is complicated by the differing rates of recombination within species. In many cases, a bifurcating tree can be positively misleading. The recently described program eBURST can be used with multilocus data to define groups or clonal complexes of related isolates derived from a common ancestor, the patterns of descent linking them together, and the ancestral genotype. eBURST has recently been extensively updated to include additional tools for exploring the relationships between isolates. We discuss the advantages of this approach and describe its use to explore patterns of descent within clonal complexes identified using multilocus sequence typing.

Algorithms↗
PubMed2000

Molecular insights into the immunopathogenesis of follicular lymphoma.

Follicular lymphoma is caused by the transformation of a germinal-center-derived B cell with a t(14;18) chromosomal translocation. The distribution of somatic mutations within immunoglobulin genes indicates that follicular-lymphoma cells can interact with antigen. In addition, nonimmunoglobulin genes such as BCL6 seem to undergo somatic hypermutation. Here, Kostas Stamatopoulos and colleagues relate the molecular data about immunoglobulin genes and the protooncogenes BCL2 and BCL6 to the pathogenesis and evolution of follicular lymphoma.

B-Lymphocyte Subsets↗
PubMed2001

Management of high-risk myelodysplastic syndromes.

The myelodysplastic syndromes (MDS) are a group of clonal disorders characterized by one or more cytopenias secondary to bone marrow dysfunction. The percentage of bone marrow blasts, the number of cytopenic cell lines and cytogenetics define more precisely clinical risk groups. In the high-risk MDS, the time for evolution to acute myeloid leukemia (AML) is between 0.2 and 1.1 years and the median survival has been evaluated between 0.4 and 1.2 years. Progress in the understanding the biology of MDS and the development of accurate prognostic classification systems have allowed a risk-adapted treatment strategy in individual patients. Some high-risk MDS patient categories may benefit from intensive cytotoxic treatment. Allogeneic stem cell transplantation (alloSCT) from donors remains the treatment of choice for younger patients. Autologous stem cell transplantation (ASCT) may provide a suitable alternative for those patients without a sibling donor or for older patients' categories. New regimens using non-myeloablative stem cell transplantation followed by donor lymphocyte infusions (DLI) are underway and have achieved promising results in HLA-identical transplantation, resulting in reduced morbidity and mortality and confirming that this approach is feasible in patients ineligible for conventional allografting due to age and/or organ toxicity. Other therapeutic strategies include new low-dose treatments, antiapoptotic agents such as amifostine and anticytokine therapy, which are currently under investigation and deserve further evaluation. More insights into the biology of the disease, the discovery of new therapeutic approaches and the search for better ways to use existing strategies may lead to more effective treatments.

Antineoplastic Combined Chemotherapy Protocols↗
PubMedDate not supplied

Mitochondria: potential roles in embryogenesis and nucleocytoplasmic transfer.

This review examines current understanding of mammalian mitochondria and mitochondrial DNA in the light of new reproductive technologies. Mitochondria are central to ageing, apoptosis, metabolism and many diseases. They are controlled by a dual genome system, with cooperation between endogenous mitochondrial genes and mitochondrial genes translocated to the nucleus over the course of evolution. This translocation has been accompanied by extreme compression of the mitochondrial genome, with little tolerance for mutations or heteroplasmy (multiple genomes). The highly compact mitochondrial genome appears to be maintained by a stringent numerical bottleneck in embryogenesis and oogenesis, followed by clonal expansion from a highly selected subset of precursor molecules. The dual nature of control between nucleus and cytoplasm sets up potential conflicts, which are normally resolved by natural selection. Such potentially opposing interests and mechanisms are probably partly to blame for the poor rates of success in cloning animals by nuclear transfer. The ability to construct cell systems and animal embryos with novel combinations and permutations of nuclear and cytoplasmic genes will provide powerful tools for examining these fundamental biological questions. Clinically, attempts to 'rescue' abnormal human oocytes or embryos by cytoplasmic transfer risk complex and unpredictable outcomes emerging from disharmonious nuclear-cytoplasmic interactions.

Aging↗
PubMed1992

Widespread dispersion of neuronal clones across functional regions of the cerebral cortex.

The cerebral cortex of the mammalian brain has expanded rapidly during the course of evolution and acquired structurally distinguishable areas devoted to separate functions. In some brain regions, topographic restrictions to cell intermixing occur during embryonic development. As a means of examining experimentally whether such restrictions occur during formation of functional subdivisions in the rat neocortex, clonally related neocortical cells were marked by retroviral-mediated transfer of a histochemical marker gene. Clonal boundaries were determined by infection of the developing brain with a library of genetically distinct viruses and amplification of single viral genomes by the polymerase chain reaction. Many clonally related neurons in the cerebral cortex became widely dispersed across functional areas of the cortex. Specification of cortical areas therefore occurs after neurogenesis.

Animals↗
PubMed2006

Novel method to identify source-associated phylogenetic clustering shows that Listeria monocytogenes includes niche-adapted clonal groups with distinct ecological preferences.

While phylogenetic and cluster analyses are often used to define clonal groups within bacterial species, the identification of clonal groups that are associated with specific ecological niches or host species remains a challenge. We used Listeria monocytogenes, which causes invasive disease in humans and different animal species and which can be isolated from a number of environments including food, as a model organism to develop and implement a two-step statistical approach to the identification of phylogenetic clades that are significantly associated with different source populations, including humans, animals, and food. If the null hypothesis that the genetic distances for isolates within and between source populations are identical can be rejected (SourceCluster test), then particular clades in the phylogenetic tree with significant overrepresentation of sequences from a given source population are identified (TreeStats test). Analysis of sequence data for 120 L. monocytogenes isolates revealed evidence of clustering between isolates from the same source, based on the phylogenies inferred from actA and inlA (P = 0.02 and P = 0.07, respectively; SourceCluster test). Overall, the TreeStats test identified 10 clades with significant (P < 0.05) or marginally significant (P < 0.10) associations with defined sources, including human-, animal-, and food-associated clusters. Epidemiological and virulence phenotype data supported the fact that the source-associated clonal groups identified here are biologically valid. Overall, our data show that (i) the SourceCluster and TreeStats tests can identify biologically meaningful source-associated phylogenetic clusters and (ii) L. monocytogenes includes clonal groups that have adapted to infect specific host species or colonize nonhost environments.

Biological Evolution↗
PubMed2004

Molecular epidemiology of Serratia marcescens in two hospitals in Gdańsk, Poland, over a 5-year period.

The history of the Serratia marcescens population in two hospitals in Danzig, Poland, over a 5-year period was analyzed in a study that combined MIC evaluation, typing by randomly amplified polymorphic DNA (RAPD) analysis and pulsed-field gel electrophoresis, and analysis of extended-spectrum beta-lactamases (ESBLs). We analyzed 354 isolates collected from 341 patients in two teaching hospitals in Danzig, Poland, from 1996 to 2000. The antimicrobial susceptibility profiles varied greatly, and for resistance to newer beta-lactams, probable AmpC cephalosporinase derepression and ESBL production occurred in about 23 and 19% of the isolates, respectively. RAPD typing, by which 69 types were discerned altogether, revealed a high degree of clonal diversity among the populations. However, the four most prevalent types were highly predominant, grouping approximately 71% of the isolates studied. These clones were observed in the two hospitals and were strong contributors to both outbreaks and the background of endemicity of the S. marcescens infections. Some of the strains that were not so widely spread (12 RAPD types; approximately 14% of the isolates) were responsible for several smaller outbreaks, and the remaining isolates represented unique RAPD types (53 types; approximately 15% of the isolates) and were probably sporadic introductions from other environments. ESBLs were identified in several different clones, and some of these had most likely already been introduced into the hospitals as ESBL producers, whereas the others acquired the ESBL-encoding genes from other enterobacterial strains in these environments. The CTX-M-3 enzyme, which is widely observed in Poland, was the most common ESBL type among the S. marcescens isolates, followed by TEM-47 and SHV-5. The complex epidemiology of ESBLs, especially in 1999 and 2000, must have arisen from the introduction of ESBL producers from other centers, their clonal dissemination, and the constant penetration of the S. marcescens populations with plasmids with ESBL genes. Multiple S. marcescens isolates were obtained from 11 patients, who probably represented both patients with recolonizations and reinfections and patients with recurrences of infections with the evolution of the strain's susceptibility.

Adolescent↗
PubMed1994

Cytogenetic findings in primary non-small cell lung cancer.

Non-small cell lung cancer (NSCLC) shows a complex cytogenetic heterogeneity and up to now no particular chromosomal aberration seems to characterize its malignant evolution. We therefore performed cytogenetic analyses of 20 primary NSCLC, 8 adenocarcinomas and 12 squamous cell carcinomas on direct preparations or short-term cultures. Only 1 case was analyzed after long-term culture. Results were obtained from 11 samples and clonal rearrangements were found in 3 cases, a diploid and a near-triploid clone with several aberrations such as i (9q), rob (14; 15) and rob (21; 21) in 1 case, a near-triploid clone in 1 case, and Y chromosome loss in 1 case. Other aberrations found were sporadic, but +7 aneuploidy and translocations involving 1p were detected in 2 and 3 samples respectively. Although to date it has been very difficult to recognize primary changes in NSCLC, nevertheless a literature review and our results indicate that i(9q) and robertsonian translocations are relevant findings.

Aged↗
PubMed1987

Facilitation of emergence of multidrug-resistant state by alteration of tumor environment: implications from competitive ecology models.

The presence of multidrug-resistant (MDR) cells in a solid tumor constitutes a major problem in cancer therapy. Current thinking suggests that the resistant phenotype arises de novo during the tumor's evolution via somatic mutation mechanisms. The proportion of MDR cells, once established, may be enriched during therapy as a consequence of differential cell kill. Michelson et al have developed mathematical models of these phenomena to gain an insight into the dynamics of clonal subpopulation emergence in general and MDR emergence in particular, and I now show that one unexpected consequence of therapy may be the facilitation of MDR emergence due to damage inflicted on the host. The therapeutic damage to the host is modeled as a decreased ability to carry a specific tumor burden.

Antineoplastic Agents↗
PubMed1994

Self and nonself: duality of immune system.

From the viewpoint of evolution, mammalian immunity has been developed to prevent invasion by foreign bodies including parasites and microorganisms and not to survey oncogenesis. The surveillance system on oncogenesis has been lost in the evolutionary process from amphibians to mammals. The essential duality between developmental antigens and tumor specific antigens is important in explaining what the target of self-defense mechanisms is. This duality between self-defense and defense against foreign bodies originated from invertebrates as shown in insects. Immunity has been developed to survey retrodifferentiation of somatic cells and to drive the developmental process in organogenesis. Under these conditions, the clonal deletion theory of immunocyte differentiation will lose its teleological meaning. Also, the hypothesis explaining self reactivity of immunity by the immune system recognizing only an 'internal image' composed of an idio-antiidio network of immunocytes and antibodies is overly pedantic.

Animals↗
PubMed1995

Acute leukemic transformation of myelodysplastic syndrome--immunophenotypic, genotypic, and cytogenetic studies.

The clinical and biological characteristics of myelodysplastic syndrome (MDS) in acute leukemic transformation were studied in 23 patients. All had myeloid transformation according to FAB criteria, but coexpression of lymphoid-associated antigens was detected in five of the 20 patients who underwent an immunophenotypic study. Rearrangement of the immunoglobulin heavy chain gene was also observed in one of the five patients who coexpressed lymphoid markers and that of the T-cell receptor beta chain gene in another one. None had pure lymphoid transformation. Clonal chromosomal abnormalities were noted in 12 (63%) of the 19 patients who underwent cytogenetic study, most commonly - 7 (six patients or 32%). In the 18 patients who underwent serial analyses both at MDS diagnosis and at acute transformation, seven (39%) underwent karyotypic evolution. The most common new or additional aberrations were +8 and +21. N-ras gene mutation was detected in two of the nine patients at acute leukemic transformation. The median interval from diagnosis of MDS to onset of acute transformation was 10 months (1-36 months). Patients with a normal karyotype at diagnosis had a significantly longer chronic phase duration than those with chromosomal abnormalities (median of 20 months vs. 5 months). However, all had a short survival time after diagnosis of acute leukemia, whether chromosomal anomalies were present or not.

Adolescent↗
PubMed2000

Accelerated appearance of multiple B cell lymphoma types in NFS/N mice congenic for ecotropic murine leukemia viruses.

Spontaneous lymphomas occur at high frequency in NFS x V+ mice, strains congenic for ecotropic murine leukemia virus (MuLV) proviral genes and expressing virus at high titer. In the present study, a total of 703 NFS x V+ lymphomas were studied by histopathology, immunophenotypic analysis, immunoglobulin heavy chain or T cell receptor beta chain rearrangements, and somatic ecotropic MuLV integrations; 90% of the lymphomas tested were of B cell lineage. Low-grade tumors included small lymphocytic, follicular, and splenic marginal zone lymphomas, while high-grade tumors comprised diffuse large-cell (centroblastic and immunoblastic types), splenic marginal zone, and lymphoblastic lymphomas. Comparison of mice of similar genetic background except for presence (NFS x V+) or absence (NFS x V-) of functional ecotropic MuLV genomes showed that NFS x V-clonal lymphomas developed at about one-half the rate of those occurring in NFS x V+ mice, and most were low-grade B cell lymphomas with extended latent periods. In NFS x V+ mice, clonal outgrowth, defined by Ig gene rearrangements, was associated with acquisition of somatic ecotropic proviral integrations, suggesting that, although generation of B cell clones can be virus independent, ecotropic virus may act to increase the rate of generation of clones and speed their evolution to lymphoma. The mechanism remains undefined, because only rare rearrangements were detected in several cellular loci previously associated with MuLV insertional mutagenesis.

Animals↗
PubMed1992

Development of T-cell leukaemia in an ataxia telangiectasia patient following clonal selection in t(X;14)-containing lymphocytes.

Ataxia telangiectasia is a rare inherited and progressive neurological disorder in which patients show an unusual predisposition to T-cell leukaemia. We report here observations on a patient with a large cytogenetically abnormal clone showing a single t(X;14)(q28;q11) translocation which conferred a proliferative advantage on the cells. The further evolution of this clone to cytogenetically more complex clones of lymphocytes was seen in the patient. She subsequently developed a rapidly progressing T-cell leukaemia, with a CD4+CD8+ T-cell phenotype, about five years after the first appearance of additional chromosome translocations in the clone cells.

Ataxia Telangiectasia↗
PubMedDate not supplied

[Angioimmunoblastic lymphadenopathy: a pathogenetic intersection between dysimmune, viral and lymphomatous diseases].

Angioimmunoblastic lymphadenopathy (AIL) still is a clinico-pathological syndrome with little known physiopathology. The advent of molecular biology has improved our understanding of this syndrome by characterization of the clonal cell. With this technique, combined with cytogenetics and immunohistochemistry, three pathological states have been individualized: 1) true AIL without evidence of monoclonal proliferation; 2) transformed AIL, and 3) AIL-like T-cell lymphoma. This clinical complex can be integrated in an evolutive continuum, starting with simple lymphoid hyperplasia and ending with frank malignant T-cell lymphoma.

Antibodies, Monoclonal↗
PubMed2002

Instructive selection and immunological theory.

The turning point of modern immunological theory was the advent of the clonal selection theory (Burnet, Talmage - 1957). A useful heuristic in the classification of theoretical models was the contrast of 'instructive' with 'selective' models of the acquisition of information by biological systems. The neo-Darwinian synthesis of the 1940s had consolidated biologists' model of evolution based on prior random variation and natural selection, viz. differential fecundity. While evolution in the large was by then pretty well settled, controversy remained about examples of cellular adaptation to chemical challenges, like induced drug-resistance, enzyme formation and the antibody response. While instructive theories have been on the decline, some clear cut examples can be found of molecular imprinting in the abiotic world, leading, e.g. to the production of specific sorbents. Template-driven assembly, as in DNA synthesis, has remained a paradigm of instructive specification. Nevertheless, the classification may break down with more microscopic scrutiny of the processes of molecular fit of substrates with enzymes, of monomers to an elongating polymer chain, as the reactants often traverse a state space from with activated components are appropriately selected. The same process may be 'instructive' from a holistic, 'selective' from an atomic perspective.

Allergy and Immunology↗