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PubMed2000

Y chromosome sequence variation and the history of human populations.

Binary polymorphisms associated with the non-recombining region of the human Y chromosome (NRY) preserve the paternal genetic legacy of our species that has persisted to the present, permitting inference of human evolution, population affinity and demographic history. We used denaturing high-performance liquid chromatography (DHPLC; ref. 2) to identify 160 of the 166 bi-allelic and 1 tri-allelic site that formed a parsimonious genealogy of 116 haplotypes, several of which display distinct population affinities based on the analysis of 1062 globally representative individuals. A minority of contemporary East Africans and Khoisan represent the descendants of the most ancestral patrilineages of anatomically modern humans that left Africa between 35,000 and 89,000 years ago.

Africa↗
PubMed2001

Developmental structure in brain evolution.

How does evolution grow bigger brains? It has been widely assumed that growth of individual structures and functional systems in response to niche-specific cognitive challenges is the most plausible mechanism for brain expansion in mammals. Comparison of multiple regressions on allometric data for 131 mammalian species, however, suggests that for 9 of 11 brain structures taxonomic and body size factors are less important than covariance of these major structures with each other. Which structure grows biggest is largely predicted by a conserved order of neurogenesis that can be derived from the basic axial structure of the developing brain. This conserved order of neurogenesis predicts the relative scaling not only of gross brain regions like the isocortex or mesencephalon, but also the level of detail of individual thalamic nuclei. Special selection of particular areas for specific functions does occur, but it is a minor factor compared to the large-scale covariance of the whole brain. The idea that enlarged isocortex could be a "spandrel," a by-product of structural constraints later adapted for various behaviors, contrasts with approaches to selection of particular brain regions for cognitively advanced uses, as is commonly assumed in the case of hominid brain evolution.

Animals↗
PubMed1994

The evolution of brain size and organization in vertebrates. A program for research.

In vertebrates, brain size variability relates to two main parameters: body size and ecological factors (in particular diet and foraging strategy). It has been considered by many authors that evolutionary brain growth is a unitary phenomenon whose main effect is to increase processing capacity. Alternatively, in this paper it is considered that brain growth is significantly associated with higher processing capacity only when it occurs associated with ecological circumstances (selection of behavioral or perceptual skills). This process is referred to as "active" growth. When the brain scales on body size, there is little change in processing capacity, and this will be referred to as "passive" growth. I propose that these two modes of phylogenetic brain growth relate to different developmental/evolutionary processes and are distinguishable at the level of adult and developing structure. Shortly, growth due to selection of behavioral capacities is associated with more differentiated brains in terms of number of areas, connectional rearrangements and cell types. Growth due to scaling of body mass produces little brain rearrangements, and many of those that occur relate to the maintenance of functions in a larger brain. In addition, active selection of brain size is triggered by plastic, ontogenic rearrangements of connectivity in the organisms, while passive growth produces the minor rearrangements that take place. Finally, I propose a research program oriented to test this model by separating the effects of body size and ecological variables in brain organization across species.

Adaptation, Physiological↗
PubMed1997

[Primary Sjögren's syndrome: clinical and immunologic study of 80 patients].

BACKGROUND: To determine the clinical and immunologic characteristics of a large cohort of patients with primary Sjörgen's syndrome (SS) and to asses if the sex, the age at onset, the time of evolution and the immunologic pattern define different subsets with specific characteristics. PATIENTS AND METHODS: We included 80 patients (76 female and 4 male) that were prospectively studied at our Unit. All patients fulfilled the European Community criteria proposed in 1993 for the diagnosis of SS. RESULTS: Mean age of patients was 62 years with a mean disease duration of 8 years. The most frequently observed clinical manifestations were xerostomia (96%), xerophthalmia (94%) and parotidomegaly (46%). The main extraglandular manifestations were arthritis (45%), Raynaud's phenomenon (20%) and liver involvement (19%). The immunologic study showed antinuclear antibodies in 82% of patients, rheumatoid factor in 45%, anti-Ro/SS-A in 40% and anti-La/SS-B in 20%. In patients with an onset of disease before the age of 40 years, a higher prevalence of parotidomegaly, peripheral neuropathy, cutaneous vasculitis, rheumatoid factor, anti-Ro/SS-A and anti-La/SS-B antibodies was observed. A disease duration longer than 10 years was associated with a higher prevalence of pulmonary involvement and more focus of mononuclear cells in the minor salivary glands. Clinical manifestations associated to any one or more immunologic marker (rheumatoid factor, anti-Ro/SS-A and/or anti-La/SS-B) were Raynaud's phenomenon, arthritis, thyroid disease, cutaneous vasculitis and peripheral neuropathy. CONCLUSIONS: Primary SS is an autoimmune disease characterized by a marked heterogeneity in the clinical presentation and evolution, thus allowing the definition of several subsets of patients with their own clinical and immunological characteristics.

Adult↗
PubMed2004

The inheritance and evolution of leaf pigmentation and pubescence in teosinte.

To investigate the genetic mechanisms that underlie morphological evolution in natural populations, we employed QTL mapping to dissect the inheritance of leaf sheath characters that distinguish Chalco from Balsas teosinte. Abundant macrohairs (trichomes) and intense anthocyanin accumulation are found in Chalco teosinte sheaths whereas Balsas teosinte leaf sheaths are green and glabrous. These character states may represent adaptations to the cooler highland (Chalco) vs. warmer middle-elevation (Balsas) climates. QTL mapping in multiple populations revealed a mix of major- and minor-effect QTL affecting both sheath color (anthocyanin) and macrohair abundance. The major QTL for macrohairs accounts for 52% of the parental difference. Epistatic interactions were detected between the major-effect QTL and multiple other QTL for both traits, accounting for substantial portions of phenotypic variance. Developmental analyses suggest that regulatory program changes underlie the phenotypic differences. Sheath anthocyanin QTL are clearly associated with b1 and a3, both of which are regulators of anthocyanin biosynthesis. Our findings suggest that changes in a small number of QTL can lead to morphological evolution by modulating existing developmental programs.

Chlorophyll↗
PubMed2006

Variation within and among species in gene expression: raw material for evolution.

Heritable variation in regulatory or coding regions is the raw material for evolutionary processes. The advent of microarrays has recently promoted examination of the extent of variation in gene expression within and among taxa and examination of the evolutionary processes affecting variation. This review examines these issues. We find: (i) microarray-based measures of gene expression are precise given appropriate experimental design; (ii) there is large inter-individual variation, which is composed of a minor nongenetic component and a large heritable component; (iii) variation among populations and species appears to be affected primarily by neutral drift and stabilizing selection, and to a lesser degree by directional selection; and (iv) neutral evolutionary divergence in gene expression becomes nonlinear with greater divergence times due to functional constraint. Evolutionary analyses of gene expression reviewed here provide unique insights into partitioning of regulatory variation in nature. However, common limitations of these studies include the tendency to assume a linear relationship between expression divergence and species divergence, and failure to test explicit hypotheses that involve the ecological context of evolutionary divergence.

Animals↗
PubMed1995

[Treatment of corticodependent systemic lupus erythematosus with low-dose methotrexate].

The authors report an open prospective study in a group of 16 patients who presented systemic lupus erythematosus with cutaneous and articular symptoms, and who required treatment with a minimum dose of 15 mg per day of prednisone. Methotrexate was given at a dose of 7.5 mg IM per week. Efficacy was demonstrated at the third month with a statistical analysis of four evolution parameters. Improvement was observed in 13 patients out of 16 and permitted the reduction of the amount of prednisone required. Secondary relapse occurred in four cases in spite of an increase in the dose of methotrexate (10 mg per week). Minor side effects were observed in four cases, and methotrexate was discontinued in only two cases. This study suggests that treatment by low doses of methotrexate is beneficial to patients with articular and cutaneous manifestations of corticodependent systemic lupus erythematosus and this therapy could be corticosteroid-sparing.

Adolescent↗
PubMed2005

[The use of implants in ptosis, hypertrophic and breast deformities].

Breast precise analysis, due to a partial or global diformity, total or minor tuberous breast allows an interesting appreciation of the skin and gland importance in breast modifications. This same analysis enables us to consider the ptosis and hypertrophies under a different angle. Thus, the relative proportions in between the various segments, their evolution in the time and especially the glandular distribution mode, sometimes leads to a different technical approach. To ensure a better glandular distribution, an important factor of the breast stability, the use of a mastopexy, which everyone knows the limits, appears under a new light and, more often than one thought, the use of a breast implant ensures homogeneity of consistency and a more long term result. Concerning the various skin modifications, their specific analysis permit to establish the type of incision used for a better-adapted scar result. The approach we suggest, (detailed analytic study of the breast, glandular distribution, relative proportion of the different breast levels and a more frequent use of an implant) which in any case should not be systematic, can obviously in certain situation optimize the quality of the result (long term projection and a better stability of the mammary shape).

Breast↗
PubMed2000

Electron microscopy of life-tested semiconductor laser diodes

Electron Microscopy on life-tested 980 nm SL SQW InGaAs/AlGaAs laser diodes is able to find and analyze lattice defects responsible for the detected failures. Anyway, the origin and evolution of those defects remains questionable. Only the comparative analysis of life-test measurements, EBIC-FIB/TEM images, and charge-transport physics is able to point out a coherent framework for complete decoding of the failure kinetics. Minority-carrier diffusion and their enhanced recombination at defective lattice points are indicated, as the energy supply required for defect reaction and growth. The rules of charge diffusion drive both the reaction model, the interpretation of EBIC images and the expected electrical and optical effects. Strain release at the ultimate propagation of defects into the strained InGaAs quantum layer is then easily related to the final state of the failed devices.

Journal Article↗
PubMed2001

Recurrent flu-like illness with migrating pulmonary infiltrates of unknown aetiology.

Migrating pulmonary infiltrates present a difficult diagnostic and therapeutic challenge. We report on eight patients (mean age 51 years, range 32-78 years, with a prolonged history of migrating pulmonary infiltrates of unknown aetiology despite a very elaborate search for infectious causes, hypersensitivity pneumonitis or inhalation fever due to occupational or domestic exposure to fungi, or to other environmental causes, and for humoral or cellular immunological incompetence. These patients (one male, seven females) presented with recurrent episodes (mean 6, range 2-13) of a flu-like illness, often with cough, wheezing and pleuritic chest pain, but without systemic involvement. Previous medical histories were unremarkable. There was no relation with smoking habits, occupation, drug use or other possible exposures. Biochemical data were non-specific. There was no peripheral nor pulmonary eosinophilia; total IgE was normal, with negative RASTs and precipitins to a variety of antigens. Cultures and serological tests for bacteria, viruses, fungi, etc were non-contributory. Chest X-ray and computed tomography (CT) scan showed bilateral migratory pulmonary infiltrates, with a predilection for the middle and lower lung zones, often with a minor-to-moderate pleural effusion. Lung function tests were usually normal; at the most a slight decrease in diffusing capacity was noted in some patients. There was no or only a slight response to antimicrobials; systemic corticosteroids were not given. Further evolution was benign with patients being asymptomatic between the episodes. Despite elaborate investigations, the cause of these 'pneumonias' remains frustratingly unknown.

Adult↗
PubMed1999

Part I. "Behind every problem lies an opportunity": meeting the challenge of diversity in medical schools.

The authors describe the historical evolution and present status of affirmative action in medical school admission policies. The demographic transformation of the medical student body between 1965 and 1998 from a homogeneous white and male group to one that includes a significant number of women and minority students is presented. Challenges to affirmative action are outlined. In addition, the authors note the increasing diversity of the general population and discuss the benefits of diversity to medical practice, research, and education. However, the upper ranks of professors and administrators remain white and male. The rationale for an innovative course on the history of bias in medicine and the benefits that diversity brings to the medical enterprise are presented.

Curriculum↗
PubMed2006

Infectious molecular clones from a simian immunodeficiency virus-infected rapid-progressor (RP) macaque: evidence of differential selection of RP-specific envelope mutations in vitro and in vivo.

A minor fraction of simian immunodeficiency virus (SIV)-infected macaques progress rapidly to AIDS in the absence of SIV-specific immune responses. Common mutations in conserved residues of env in three SIVsmE543-3-infected rapid-progressor (RP) macaques suggest the evolution of a common viral variant in RP macaques. The goal of the present study was to analyze the biological properties of these variants in vitro and in vivo through the derivation of infectious molecular clones. Virus isolated from a SIVsmE543-3-infected RP macaque, H445 was used to inoculate six naive rhesus macaques. Although RP-specific mutations dominated in H445 tissues, they represented only 10% of the population of the virus stock, suggesting a selective disadvantage in vitro. Only one of these macaques (H635) progressed rapidly to AIDS. Plasma virus during primary infection of H635 was similar to the inoculum. However, RP-specific mutations were apparently rapidly reselected by 4 to 9 weeks postinfection. Terminal plasma from H635 was used as a source of viral RNA to generate seven full-length, infectious molecular clones. With the exception of one clone, which was similar to SIVsmE543-3, clones with RP-specific mutations replicated with delayed kinetics in rhesus peripheral blood mononuclear cells and human T-cell lines. None of the clones replicated in monocyte-derived or alveolar macrophages, and all used CCR5 as their major coreceptor. RP variants appear to be well adapted to replicate in vivo in RP macaques but are at a disadvantage in tissue culture compared to their parent, SIVsmE543-3. Therefore, tissue culture may not provide a good surrogate for replication of RP variants in macaques. These infectious clones will provide a valuable reagent to study the roles of specific viral variants in rapid progression in vivo.

Amino Acid Sequence↗
PubMed1990

Use of oligonucleotide probes directed against T cell antigen receptor gamma delta variable-(diversity)-joining junctional sequences as a general method for detecting minimal residual disease in acute lymphoblastic leukemias.

To provide a sensitive and generally applicable method to detect clonal cells in acute lymphoblastic leukemias (ALL), we have designed a new strategy based on the polymerase chain reaction (PCR) amplification of the T cell receptor gamma delta gene rearrangements found in most T and B lineage ALLs. PCR allows rapid sequencing of variable-(diversity)-joining (V-[D]-J) junctions from tumor DNA and construction of anti-junctional oligonucleotides (AJOs) used as probes to detect clonal cells in the same patient. We have defined oligonucleotides suitable for all T cell receptor (TCR) rearrangements involving functional V gamma segments. Oligonucleotides corresponding to preferential TCR delta rearrangements in T and B lineage ALLs were also used. By analysis of the nucleotide sequence of 52 V gamma-V gamma junctions from 30 cases of B and T ALLs, we demonstrate that V-J junctional sequences are clone specific in both lineages and at all stages of differentiation examined despite the frequent presence of the recently described P nucleotides. Experiments performed with TCR gamma delta AJOs on DNA from tumor cells and polyclonal T cells show that AJOs can be used to differentiate clonal cells from polyclonal T cells, distinguish between different T cell clones, and detect residual clonal populations at 10(-4)/10(-5) dilution. AJOs were also used to detect residual disease in samples from patients in clinical and morphological complete remission. Finally, rearrangement patterns were studied by classical Southern analysis in selected cases at both presentation and subsequent relapse showing absence of clonal evolution in most cases. V-(D)-J nucleotide sequences of rearrangements with an identical pattern of rearrangement at presentation and relapse were identical in all cases analyzed. We therefore describe a new, specific, and clinically useful strategy for the detection of minor clonal populations applicable in the majority of cases of ALL.

Alleles↗
PubMed1990

US health care policy in 1990: looking back, looking ahead.

Health policy in the United States is best understood as a policy of incrementalism with major interventions occurring only in response to crisis, as in the case of the Medicare legislation that profoundly altered our historic financing of health care. The characteristically minor, unplanned, adjustments that are made often have major unanticipated consequences, and these serve to explain the radical transformation of the nation's health system in the half-century since World War II. The main elements in this change--the evolution of employment-tied private insurance for the majority of the population, the predominance of specialism and superspecialism in medical practice, the expansion of the voluntary hospital system with capital liberally raised through tax-exempt bond issues, advancing technology and medical capability are reviewed. The major persistent policy issues--uncontrolled expenditures and the increasing numbers of uninsured--will ultimately precipitate change, perhaps by the end of the decade, very likely a minimum benefit, universal federal-state insurance system, supplemented by the private market--hardly radical systemic reform.

Forecasting↗
PubMed2000

[Better understanding of the biology of cancer cells].

Most forms of cancer arise through a Darwinian evolutionary process. The natural selection that ultimately leads to cancer takes place in somatic tissues although it may be triggered by inherited mutations in a small but significant minority. It favors the growth of clones and subclones that are less and less responsive to normal intra- and extracellular growth control mechanisms. The development of molecular biology has led to the identification of many genes that participate in this somatic evolution. They belong to the following groups: Oncogenes, constitutively activated by structural and/or regulatory changes that drive the cell to continuous proliferation; Tumor suppressor genes, that can inhibit the illegitimately activated cell cycle. They contribute to tumor development by loss mutations or permanent down-regulation, e.g. by methylation; Apoptosis inhibitory genes that can contribute to tumor development by raising the apoptotic threshold, and apoptosis promoting genes that can favor the growth of apoptosis prone tumor cells by their loss or inactivation; DNA repair genes whose inactivation can counteract the normal elimination of cells that carry potentially cancer promoting mutations. Inherited mutations in DNA repair genes can lead to familial cancer syndromes. Immortalizing genes that counteract cellular senescence; Angiogenesis promoting genes whose products may stimulate the vascular supply of tumors; Genes whose structural or functional changes may facilitate the escape of tumor cells from immune rejection; The multi-step development of individual tumors can encompass changes in most or all of these genes. They occur independently of each other and without any fixed order or timing. Tumor emancipation from growth control can therefore proceed along various pathways. It follows that each tumor must be regarded as a biologically unique individual.

Apoptosis↗
PubMed2000

[Better understanding of the biology of cancer cells].

Most forms of cancer arise through a Darwinian evolutionary process. The natural selection that ultimately leads to cancer takes place in somatic tissues although it may be triggered by inherited mutations in a small but significant minority. It favors the growth of clones and subclones that are less and less responsive to normal intra- and extracellular growth control mechanisms. The development of molecular biology has led to the identification of many genes that participate in this somatic evolution. They belong to the following groups: Oncogenes, constitutively activated by structural and/or regulatory changes that drive the cell to continuous proliferation; Tumor suppressor genes, that can inhibit the illegitimately activated cell cycle. They contribute to tumor development by loss mutations or permanent down-regulation, e.g. by methylation; Apoptosis inhibitory genes that can contribute to tumor development by raising the apoptotic threshold, and apoptosis promoting genes that can favor the growth of apoptosis prone tumor cells by their loss or inactivation; DNA repair genes whose inactivation can counteract the normal elimination of cells that carry potentially cancer promoting mutations. Inherited mutations in DNA repair genes can lead to familial cancer syndromes. Immortalizing genes that counteract cellular senescence; Angiogenesis promoting genes whose products may stimulate the vascular supply of tumors; Genes whose structural or functional changes may facilitate the escape of tumor cells from immune rejection; The multi-step development of individual tumors can encompass changes in most or all of these genes. They occur independently of each other and without any fixed order or timing. Tumor emancipation from growth control can therefore proceed along various pathways. It follows that each tumor must be regarded as a biologically unique individual.

Apoptosis↗
PubMed1987

Flow cytometric lymphocyte immunophenotyping in homosexual men with the persistent generalized lymphadenopathy syndrome: a longitudinal study of lymph nodes and blood.

We have performed lymphocyte phenotypic analysis on serial lymph node biopsies and peripheral blood samples from 11 patients with the persistent generalized lymphadenopathy (PGL) syndrome and correlated the findings with histologic and clinical findings (median follow-up 18 months) in a search for factors that may predict evolution to acquired immunodeficiency syndrome (AIDS). Follow-up lymph node biopsies showed higher percentages of T-cells, both OKT4+ and OKT8+ phenotypes, and lower percentages of Slg+ B-cells and OKla+ cells. The lymph node changes were relatively minor in degree compared to the progressive peripheral blood OKT4+ lymphocytopenia observed over a similar time interval. The one patient who developed a malignant lymphoma had a high percentage of nodal T-cells and low peripheral blood T-cell counts. We conclude that serial lymph node studies contribute to an understanding of the natural history of PGL, but that peripheral blood counts are a more sensitive indicator of immune status in individual patients.

AIDS-Related Complex↗
PubMed1992

The evolution of coexisting highly divergent LINE-1 subfamilies within the rodent genus Peromyscus.

Two distinct members of the LINE-1 (L1) family in Peromyscus were characterized. The two clones, denoted L1Pm55 and L1Pm62, were 1.5 kb and 1.8 kb in length, respectively, and align to the identical region of the L1 sequence of Mus domesticus. Sequence similarity was on the order of 70% between L1Pm55 and L1Pm62, which approximates that between either Peromyscus sequence and Mus L1. L1Pm62 represents a more prevalent subfamily than L1Pm55. L1Pm62 exists in about 500 copies per haploid genome, while L1Pm55 exists in about 100 copies. The existence of major and minor subpopulations of L1 within Peromyscus is in contrast to murine rodents and higher primates, where L1 copy number is on the order of 20,000 to 100,000, and where levels of intraspecific divergence among L1 elements are typically less than 15-20%. Additional Peromyscus clones are similarly divergent from both L1Pm62 and L1Pm55, implying the existence of more than two distinct L1 subfamilies. The highly divergent L1 subfamilies in Peromyscus apparently have been evolving independently for more than 25 million years, preceding the divergence of cricetine and murine rodents. Investigations of the evolution of L1 within Peromyscus by restriction and Southern analysis was performed using species groups represented by the partially interfertile species pairs P. maniculatus-P. polionotus, P. leucopus-P. gossypinus, and P. truei-P. difficilis of the nominate subgenus and P. californicus of the Haplomylomys subgenus. Changes in L1 and species group taxonomic boundaries frequently coincided. The implications for phylogeny are discussed.

Animals↗