Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “clonal evolution”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,549 records · Page 86Linked to original sources
PubMed1999

Evolution of antigen-specific T cell receptors in vivo: preimmune and antigen-driven selection of preferred complementarity-determining region 3 (CDR3) motifs.

Antigen (Ag)-driven selection of helper T cells (Th) in normal animals has been difficult to study and remains poorly understood. Using the major histocompatibility complex class II- restricted murine response to pigeon cytochrome c (PCC), we provide evidence for both preimmune and Ag-driven selection in the evolution of Ag-specific immunity in vivo. Before antigenic challenge, most Valpha11(+)Vbeta3(+) Th (70%) express a critical complementarity-determining region 3 (CDR3) residue (glutamic acid at TCR-alpha93) associated with PCC peptide contact. Over the first 5 d of the primary response, PCC-responsive Valpha11(+)Vbeta3(+) Th expressing eight preferred CDR3 features are rapidly selected in vivo. Clonal dominance is further propagated through selective expansion of the PCC-specific cells with T cell receptor (TCR) of the "best fit." Ag-driven selection is complete before significant emergence of the germinal center reaction. These data argue that thymic selection shapes TCR-alpha V region bias in the preimmune repertoire; however, Ag itself and the nongerminal center microenvironment drive the selective expansion of clones with preferred TCR that dominate the response to Ag in vivo.

Animals↗
PubMed1980

Hodgkin's disease: unfolding concepts concerning its nature, management and prognosis.

The evolution of our concepts concerning the fundamental nature and natural history of Hodgkin's disease is reviewed. Recent evidence establishes that it is indeed a malignant neoplasm, albeit a curious one, the giant cells of which display aneuploid karyotypes, often with marker chromosomes indicating their clonal derivation, and the functional and surface marker properties of cells of the mononuclear phagocyte series. The disease tends initially to spread by contiguity from one lymph node chain to others with which direct lymphatic channel communications exist. Essentially all patients, even those with limited disease, have some degree of impairment of cell-mediated immunity, apparently due to inhibition of T-lymphocyte function. Lymphangiography, computed tomography, and laparotomy with splenectomy have greatly improved the accuracy of clinical staging. Total lymphoid megavoltage radiotherapy and/or multidrug combination chemotherapy now permit the eradiction of disease of all stages, resulting in a dramatic improvement in prognosis and an increasing frequency of permanent cure of this once inevitably fatal condition.

Aneuploidy↗
PubMed1989

Cytogenetic and quantitative DNA analysis of primary and xenografted human osteosarcomas.

We have analyzed, cytogenetically and by flow DNA cytometry, three human osteosarcomas. From one case, both the primary tumor (T9) and three of its serial passages in nude mice were analyzed. From the two other tumors (T1, T4), nude mouse xenografts were examined. Complex karyotypic rearrangements were invariably found in the short-term culture preparations. The major clones were hypodiploid in T1 but near-triploid in all other tumor samples. No rearrangement common to all tumors could be identified. The DNA indexes were 1.0/2.0 (T1), 1.4 (T4), 0.9/1.8 (T9 primary), and 1.7 (all T9 xenografts). Thus, there was good correlation between the DNA indexes and the chromosome numbers. Chromosomal evolution could be studied in one case, in which both the primary tumor (T9) and its xenograft passages (1, 4, and 7), obtained 1, 7, and 11 months after the first transplantation of T9 cells to nude mice, were analyzed. All but one of the clonal marker chromosomes found in the primary tumor were retained in all passages. On the other hand, several new clonal markers developed.

Animals↗
PubMed1999

Spontaneous heterosis in larval life-history traits of hemiclonal frog hybrids.

European water frog hybrids Rana esculenta (Rana ridibunda x Rana lessonae) reproduce hemiclonally, transmitting only their ridibunda genome to gametes. We compared fitness-related larval life-history traits of natural R. esculenta from Poland with those of the two sympatric parental species and of newly generated F1 hybrids. Compared with either parental species, F1 hybrid offspring had higher survival, higher early growth rates, a more advanced developmental stage by day 49, and earlier metamorphosis, but similar mass at metamorphosis. R. esculenta from natural lineages had trait values intermediate between those of F1 offspring and of the two parental species. The data support earlier observations on natural R. esculenta that had faster larval growth, earlier metamorphosis, and higher resistance to hypoxic conditions compared with either parental species. Observing larval heterosis in F1 hybrids in survival, growth rate, and time to metamorphosis, however, at an even higher degree than in hybrids from natural lineages, demonstrates that heterosis is spontaneous and results from hybridity per se rather than from subsequent interclonal selection; in natural lineages the effects of hybridity and of clonal history are confounded. This is compelling evidence for spontaneous heterosis in hybrid clonals. Results on hemiclonal fish hybrids (Poeciliopsis) showed no spontaneous heterosis; thus, our frog data are not applicable to all hybrid clonals. Our data do show, however, that heterosis is an important potential source for the extensively observed ecological success of hybrid clonals. We suggest that heterosis and interclonal selection together shape fitness of natural R. esculenta lineages.

Animals↗
PubMed1994

Clonal spread of serogroup A meningococci: a paradigm for the analysis of microevolution in bacteria.

Extensive epidemiological analyses of epidemics of meningococcal meningitis have resulted in large, well-defined strain collections which represent the local diversity and global spread of serogroup A bacteria. Several genes for cell surface proteins are conserved during spread, with a few exceptions: analysis of these exceptions has revealed some of the phenomena which can lead to microevolution. Microevolution is so rapid with serogroup A meningococci that several independent recombination events have been documented within the last few decades. In a few cases, the recombinant bacteria have become established by clonal replacement plus epidemic spread. Comparison with other bacteria indicates that serogroup A meningococci provide a number of advantages for analysis of microevolution.

Bacterial Outer Membrane Proteins↗
PubMed1994

Microevolution within a clonal population of pathogenic bacteria: recombination, gene duplication and horizontal genetic exchange in the opa gene family of Neisseria meningitidis.

Opacity (Opa) proteins are a family of antigenically variable outer-membrane proteins of Neisseria meningitidis. Even among clonally related epidemic meningococcal isolates, there is greater variation of Opa protein expression than can be accounted for by the opa gene repertoire of any individual strain. We characterized the opa genes of eight closely related isolates of serogroup A N. meningitidis (subgroup IV-1) from a recent meningitis epidemic in West Africa. DNA sequence analysis and Southern blot experiments indicated that changes occurred in the opa genes of these bacteria as they spread through the human population, over a relatively short period of time. Such changes in one or a few loci within a clonal population are referred to as microevolution. The distribution of sequences present in hypervariable (HV) regions of the opa genes suggests that duplication of all or part of opa genes into other opa loci changed the repertoire of Opa proteins that could be expressed. Additional variability in this gene family appears to have been introduced by horizontal exchange of opa sequences from other meningococcal strains and from Neisseria gonorrhoeae. These results indicate that processes of recombination and genetic exchange contributed to variability in major surface antigens of this clonal population of pathogenic bacteria.

Antibodies, Bacterial↗
PubMed1992

Granulocyte-macrophage colony-stimulating factor (GM-CSF): preclinical and clinical investigations.

In conclusion, hematopoietic growth factors have been shown to enhance the recovery and function of circulating WBCs after standard-dose cancer therapy or high-dose cancer therapy with ABMT, and preliminary data strongly suggests that these agents may have the ability to restore leukocyte numbers and competence in AIDS, myelodysplastic syndromes, and other marrow failure states. Phase I and II trials of GM-CSF in patients with AIDS, cancer, marrow failure states, and following bone marrow transplantation have been published, and limited phase III randomized trial experiences have been reported as well. Overall, GM-CSF represents a fascinating molecule with which to modulate human hematopoiesis in vivo. The multilineage stimulatory effects of GM-CSF that are evident in vitro have not been striking or consistent in clinical trials. However, the effects of GM-CSF on the production and function of mature neutrophils, monocytes, and eosinophils have been noted in the vast majority of clinical scenarios in which this cytokine has been tested. The clinical benefits of GM-CSF have, to date, only been proven in large-scale randomized studies of recovery from ABMT for lymphoid neoplasms. However, further data regarding the use of GM-CSF in other clinical settings have been generated, and the final results are eagerly anticipated by the oncology community. The beneficial effects of GM-CSF following ABMT consisted not only of a shorter period of absolute neutropenia, but also fewer significant infections, a diminished requirement for intravenous antibiotic administration, and a shorter overall duration of inpatient hospitalization. The use of GM-CSF in clonal disorders of hematopoiesis, such as myelodysplasia or myeloid leukemias, requires caution before such applications can be routinely recommended, and the demonstration of safety in this setting from large randomized trials will be needed. Preliminary data from small randomized trials suggests that the incidence of evolution to leukemia in patients with myelodysplasia and the number of patients with regrowth of leukemia after induction treatment in relapsed patients with AML may not be significantly different than in patients who do not receive GM-CSF. Various neutropenic conditions (eg, idiopathic or congenital) may respond clinically to hematopoietic growth factors such as GM-CSF. Patients treated for 3 to 15 months continue to respond with significantly increased granulocytes and resolution of prior infection. The subcutaneous route of administration is convenient and patients seem to accept it readily. It is difficult to determine the extent to which adjunctive therapy with GM-CSF will be cost effective.(ABSTRACT TRUNCATED AT 400 WORDS)

Acquired Immunodeficiency Syndrome↗
PubMed2004

Long-term experimental evolution in Escherichia coli. XII. DNA topology as a key target of selection.

The genetic bases of adaptation are being investigated in 12 populations of Escherichia coli, founded from a common ancestor and serially propagated for 20,000 generations, during which time they achieved substantial fitness gains. Each day, populations alternated between active growth and nutrient exhaustion. DNA supercoiling in bacteria is influenced by nutritional state, and DNA topology helps coordinate the overall pattern of gene expression in response to environmental changes. We therefore examined whether the genetic controls over supercoiling might have changed during the evolution experiment. Parallel changes in topology occurred in most populations, with the level of DNA supercoiling increasing, usually in the first 2000 generations. Two mutations in the topA and fis genes that control supercoiling were discovered in a population that served as the focus for further investigation. Moving the mutations, alone and in combination, into the ancestral background had an additive effect on supercoiling, and together they reproduced the net change in DNA topology observed in this population. Moreover, both mutations were beneficial in competition experiments. Clonal interference involving other beneficial DNA topology mutations was also detected. These findings define a new class of fitness-enhancing mutations and indicate that the control of DNA supercoiling can be a key target of selection in evolving bacterial populations.

Adaptation, Physiological↗
PubMed1997

Molecular evolution and host adaptation of Bordetella spp.: phylogenetic analysis using multilocus enzyme electrophoresis and typing with three insertion sequences.

A total of 188 Bordetella strains were characterized by the electrophoretic mobilities of 15 metabolic enzymes and the distribution and variation in positions and copy numbers of three insertion sequences (IS). The presence or absence of IS elements within certain lineages was congruent with estimates of overall genetic relationships as revealed by multilocus enzyme electrophoresis. Bordetella pertussis and ovine B. parapertussis each formed separate clusters, while human B. parapertussis was most closely related to IS1001-containing B. bronchiseptica isolates. The results of the analysis provide support for the hypothesis that the population structure of Bordetella is predominantly clonal, with relatively little effective horizontal gene flow. Only a few examples of putative recombinational exchange of an IS element were detected. Based on the results of this study, we tried to reconstruct the evolutionary history of different host-adapted lineages.

Adaptation, Biological↗
PubMed1999

Towards understanding the evolution of the human commensal yeast Candida albicans.

Allelic frequencies and relationships for one dimorphic locus and three unlinked polymorphic loci have been determined for 114 unrelated isolates of Candida albicans, including 14 laboratory reference strains and 50 strains from each of two geographic regions. Although there was no indication of geographical partitioning, there were significant correlations for specific allelic pairs among loci and little evidence that any alleles were in Hardy-Weinberg equilibrium. This gives additional support for the concept that the primary mode of genetic inheritance in this species is clonal, with other intracellular genetic events playing a lesser role in the creation of genomic diversity. Through inference of this and other known attributes of closely related Candida species, such as sequence analysis of IS1 and the ITS2 (internal transcribed spacer 2) region of the rDNA cistron, the deduced phylogeny suggests an evolutionarily recent origin for many frequently isolated strains. This finding will be of interest in the context of understanding pathogenicity and drug resistance in this human commensal yeast.

Alleles↗
PubMedDate not supplied

Characterization of subpopulations (clones and subclones) of the 21 SF strain of Trypanosoma cruzi after long lasting maintenance in the laboratory.

Several studies have shown a clonal structure of Trypanosoma cruzi and its possible correlation with the behavioral heterogeneity of the parasite strains. In the present study, the 21 SF strain, that have been maintained in laboratory by successive passages in mice, for more than 15 years, showing a stability of biological and isoenzymic characteristics has been cloned, with the objective of establishing the characters of its clones and subclones. With the technique of isolation of a single parasite from the blood of infected mice, 5 clones and 14 subclones have been obtained. After four passages into mice, inoculum of 10(5) was obtained for each clone and subclone and inoculated into mice weighing 10 to 12 g. These were used for the study of the biological behavior of the clones: evolution of parasitemia, morphology of blood forms and host mortality. For isoenzymic characterization, the clones and subclones were analyzed for ALAT, ASAT, GPI and PGM enzymes. Results have shown that the 5 clones and the 14 subclones disclosed a biological behavior similar to the parental strain, with minor variability of the parasitemic profiles and also the same isoenzymic patterns. These results confirm the stability of the 21 SF strain and indicate a clonal homogeneity of its populations. This is compatible with the hypothesis that the T. cruzi strains represent an equilibrium of either homogenous or heterogeneous populations.

Animals↗
PubMed1988

Stability of cytogenetic alterations in a human melanoma cell line and five clonal derivatives.

A cytogenetic study was done on a human malignant melanoma cell line and its 5 clones. Chromosome banding analysis indicated the presence of 7 "shared" markers (M) and 9 unique markers (m) that were present only in the clones. Chromosomes 1, 5, 9, 12, 17 and 21 were involved in M-markers and chromosomes 1, 2, 4, 6, 8, 9, 11, 16, 17, 18 and 21 were involved in m-marker formation. Both parental and clonal lines had near-triploid chromosome numbers. A number of M-markers were isochromosomes of the short (p) and long (q) arms of chromosome 1. Our cytogenetic data indicate that the parental line contained subpopulations of cells that were in different stages of karyotypic evolution.

Cell Line↗
PubMed2002

Sequence polymorphism of dotA and mip alleles mediating invasion and intracellular replication of Legionella pneumophila.

Legionella pneumophila inhabit a variety of natural and man-made aquatic environments, where they live primarily as intracellular parasites of protozoans. Given the proper exposure, however, they can cause opportunistic pneumonic infections in humans. The products of two L. pneumophila genes, dotA and mip, are part of the mechanism mediating the initial invasion of eukaryotic cells, and subsequent intracellular survival and multiplication. In this study, DNA polymorphism of the dotA and mip genes was assessed for 17 clinical and environmental isolates by nucleotide sequencing to determine the level of sequence variation, rates of molecular evolution, and history of gene divergence. The mip gene is highly conserved, whereas dotA is extremely variable, with an average level of nucleotide diversity four times greater than that of mip. Gene trees for each locus support a division of the L. pneumophila isolates into two clonal lineages. There are several disagreements between the gene trees suggesting that although L. pneumophila has a clonal population structure, genetic exchange has contributed to genotypic variation among strains in nature.

Alleles↗
PubMedDate not supplied

Pityriasis lichenoides in children: clinicopathologic review of 22 patients.

Pityriasis lichenoides (PL) is a cutaneous disease of unknown origin, with an autoinvolutive course, that can occur in pediatric patients. Traditionally, acute and chronic variants have been described, but other special forms of presentation have been reported. We reviewed the clinical records and histopathologic specimens of all pediatric patients diagnosed with PL in our hospital from 1980 to 1995 to assess the clinicopathologic features of this disorder in our environment. Twenty-two of the 118 cases reviewed were pediatric patients less than 15 years old (12 males and 10 females, 18.6% of all patients). Their ages ranged from 3 to 15 years, with a mean of 9.3 years. Most of the patients (72%) had the chronic variant of the disease, while the remainder had an acute course. One patient suffered from acute ulceronecrotic PL. Systemic treatments prescribed were erythromycin in eight patients, PUVA in five patients, and methotrexate in one patient. Three patients had a prolonged course with more than two episodes. Acute and chronic PL are polar extremes, but individual cases cannot be classified only on the basis of histopathologic data, since coexistence of lesions in different stages of evolution can lead to sampling bias. Acute ulceronecrotic forms and the presence of a variable degree of cellular atypia in the infiltrate are liable to cause differential diagnostic problems with lymphomatoid papulosis (LP), which cannot be completely resolved on the basis of T-cell receptor clonal rearrangement detection.

Acute Disease↗
PubMed1993

Clonal chromosomal abnormalities in Fanconi's anaemia: what do they really mean?

Patients with Fanconi's anaemia (FA) have aplastic anaemia, leukaemia, myelodysplasia and tumours. Since leukaemia has a very poor prognosis, it is desirable to identify high-risk patients. To determine the significance of clonal marrow chromosomal abnormalities we began a prospective study in 17 patients: five were normal, eight aplastic, and four myelodysplastic. Three of 11 with adequate cytogenetics had transient abnormal clones. None had leukaemia at 3-24 months. Changing cytogenetic patterns may not be related to leukaemic evolution in patients with a DNA repair defect.

Chromosome Aberrations↗
PubMedDate not supplied

[Persistent polyclonal B-cell lymphocytosis].

Persistent polyclonal B-cell lymphocytosis (PPBL) is a rare and recently described entity. PPBL is diagnosed predominantly but not exclusively in women, usually smokers and is characterized by a moderate, chronic and absolute lymphocytosis (> 4 x 109/L). Peripheral blood examination show in all cases atypical binucleated lymphocytes. A polyclonal serum IgM is also associated and HLA-DR7 expression is present in most cases. The B cells are polyclonal with kappa and lambda light-chain expression. No clonal rearrangement of immunoglobulin heavy chain genes is observed. Finally, +i(3q) is a recurrent chromosomal abnormality and detected in 77% of cases with premature chromosome condensation in 50% and both abnormalities in 41% of cases. The benign clinical course of PPBL and lack of biological evolution in the majority of cases suggest that recognition is so important that aggressive therapy could be avoided.

B-Lymphocytes↗
PubMed2003

[Molecular genetic characteristics of rifampicin-resistant Mycobacterium tuberculosis isolates in Novosibirsk].

Forty rifampicin-resistant clinical isolates from patients living in Novosibirsk were studied. Six alleles earlier described in the literature were identified by the sequencing technique. The frequency of mutations in the studied samples slightly differs from that earlier reported for other geographic regions: 21 (52.5%) strains carried the mutated codon TTG in position 531 (Ser-->Leu), 7 (17.5%) had GTC in position 516 (Asp-->Val) and 2 (5%) had the GAC substitution in position 526 (His-->Asp), which is prevalent elsewhere. Sequence analysis revealed no mitations in 5 (12.5%) of the 40 isolates although this isolate was repeatedly resistant to rifampicin. VNTR-typing targeted to tandem repeats (ETR A, B, C, D, and E) was carried out to establish a genetic relationship for rifampicin-resistant isolates. Nine genetic types with VNTR-profiles termed as 12322, 32122, 32123, 32124, 32125, 32522, 23524, 12223, 22222, 33433 were revealed. There was no strict correlation between the type of mutation in the rpoB gene and the VNTR-type, which reflects different rates of evolution and the level of selective pressure on these genetic targets. The isolates of VNTR-types 32123 and 32125 with mutations in codon 531, and type 32122 in codons 531, 526, 516 showed a high clustering. This is likely to reflect the recent transmission and clonal dissemination of the epidemic strains of Mycobacterium tuberculosis. Thus, mutations in the rpoB gene did not reduce the virulence and transmissivity of these clones. Twenty-six of 27 clinical isolates selected by rifampicin-resistance were also resistant to isoniazid, which confirms the known fact that rifampicin-resistance may be used as a marker of isoniazid-resistance.

Antitubercular Agents↗
PubMed2004

Host resistance and the evolution of kin recognition in polyembryonic wasps.

Recognition of relatives is considered a key factor in the evolution of sociality as it ensures that the benefits of altruism flow to those who share the altruist's genes. However, theory predicts that genetically based recognition systems will not persist if the only selection maintaining them derives from the recognition system itself. Kin-recognition systems, therefore, are hypothesized to involve genetic variation maintained by other functions. Polyembryonic wasps are parasites of moth larvae that clonally produce large numbers of offspring and two morphologically distinct castes. Some embryos develop into reproductive larvae that mature into adult wasps, whereas others develop into soldier larvae whose function is defence. Soldiers from Copidosoma floridanum distinguish relatives from non-relatives on the basis of relatedness. Here, we report that the recognition cues used by soldiers derive from the extraembryonic membrane, which also protects these parasites from the host's immune response. This suggests that the kin-recognition system used by C. floridanum may be maintained in part by selection for resistance against the host.

Animals↗