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PubMed1994

The sesamoid bone of musculus abductor pollicis longus (os radiale externum or prepollex) in primates.

The sesamoid bone of the musculus abductor pollicis longus has been investigated in a series of 276 nonhuman primates representative of 37 genera, and in a series of 300 radiographs of human subjects. The presence of this ossicle in primates is a primitive characteristic. It is present in all nonhuman primates, and is generally articulated with both the scaphoid and trapezium. Modifications of the general mammalian pattern exist only in Gorilla gorilla, where the sesamoid bone is observed in about half of the individuals, and in Homo, where this ossicle is normally absent.

Animals↗
PubMed1986

A hybrid model of the CO2 geochemical cycle and its application to large impact events.

A hybrid model of the carbonate-silicate geochemical cycle is presented which is capable of calculating the partitioning of carbon dioxide between the atmosphere, ocean, and sedimentary rocks. The ocean is subdivided into a shallow, mixed layer, which remains in equilibrium with the atmosphere, and a massive, deep layer which does not. Gradients in dissolved carbon content are established between the mixed layer and the deep ocean as a consequence of downward fluxes of fecal matter and of dead planktonic organisms. The dissolved carbon content and alkalinity of the ocean as a whole are controlled by weathering and metamorphism of sedimentary rocks. Equilibrium solutions are derived for the preindustrial atmosphere/ocean system and for a system that may be similar to that existing during the Late Cretaceous Period. The model is then used to determine how the modern and ancient marine biospheres might be affected by an oceanic impact of a large asteroid or comet. Such an event could perturb the carbon cycle in several different ways. Global darkening caused by stratospheric dust veil could destroy most of the existing phytoplankton in a period of several weeks to several months. At the same time, dissolution of atmospheric NOx compounds synthesized during the impact would lower the pH of ocean surface waters and release CO2 into the atmosphere. Both effects might be enhanced by an influx of CO2 released from upwelling of deep ocean water near the hot impact site, from oxidation of dead organic matter, and from the comet itself. The net result could be to raise surface temperatures by several degrees and to make the surface ocean uninhabitable by calcareous organisms for as much as 20 yrs (the time scale for mixing with deep ocean). It appears unlikely, however, that an impact could create a "Strangelove ocean," in which surface waters remained corrosive to calcium carbonate for thousands or tens of thousands of years. Thus, disruption of the carbon cycle by an impact event cannot by itself explain the scarcity of calcium carbonate in sediments found within the first few centimeters above the K/T boundary.

Atmosphere↗
PubMed2002

Origins of the machinery of recombination and sex.

Mutation plays the primary role in evolution that Weismann mistakenly attributed to sex. Homologous recombination, as in sex, is important for population genetics--shuffling of minor variants, but relatively insignificant for large-scale evolution. Major evolutionary innovations depend much more on illegitimate recombination, which makes novel genes by gene duplication and by gene chimaerisation--essentially mutational forces. The machinery of recombination and sex evolved in two distinct bouts of quantum evolution separated by nearly 3 Gy of stasis; I discuss their nature and causes. The dominant selective force in the evolution of recombination and sex has been selection for replicational fidelity and viability; without the recombination machinery, accurate reproduction, stasis, resistance to radical deleterious evolutionary change and preservation of evolutionary innovations would be impossible. Recombination proteins betray in their phylogeny and domain structure a key role for gene duplication and chimaerisation in their own origin. They arose about 3.8 Gy ago to enable faithful replication and segregation of the first circular DNA genomes in precellular ancestors of Gram-negative eubacteria. Then they were recruited and modified by selfish genetic parasites (viruses; transposons) to help them spread from host to host. Bacteria differ fundamentally from eukaryotes in that gene transfer between cells, whether incidental to their absorptive feeding on DNA and virus infection or directly by plasmids, involves only genomic fragments. This was radically changed by the neomuran revolution about 850 million years ago when a posibacterium evolved into the thermophilic cenancestor of eukaryotes and archaebacteria (jointly called neomurans), radically modifying or substituting its DNA-handling enzymes (those responsible for transcription as well as for replication, repair and recombination) as a coadaptive consequence of the origin of core histones to stabilise its chromosome. Substitution of glycoprotein for peptidoglycan walls in the neomuran ancestor and the evolution of an endoskeleton and endomembrane system in eukaryotes alone required the origin of nuclei, mitosis and novel cell cycle controls and enabled them to evolve cell fusion and thereby the combination of whole genomes from different cells. Meiosis evolved because of resulting selection for periodic ploidy reduction, with incidental consequences for intrapopulation genetic exchange. Little modification was needed to recombination enzymes or to the ancient bacterial catalysts of homology search by spontaneous base pairing to mediate chromosome pairing. The key innovation was the origin of meiotic cohesins delaying centromere splitting to allow two successive divisions before reversion to vegetative growth and replication, necessarily yielding two-step meiosis. Also significant was the evolution of synaptonemal complexes to stabilise bivalents and of monopolins to orient sister centromeres to one spindle pole. The primary significance of sex was not to promote evolutionary change but to limit it by facilitating ploidy cycles to balance the conflicting selective forces acting on rapidly growing phagotrophic protozoa and starved dormant cysts subject to radiation and other damage.

Animals↗
PubMed2003

Lichtenstein tension-free hernioplasty: its inception, evolution, and principles.

To circumvent the degenerative nature of inguinal hernias and adverse effect of suture line tension, the Lichtenstein tension-free hernioplasty began in 1984 and evolved (between 1984 and 1988) to a procedure that is now considered the gold standard of hernia repair by the American College of Surgeons. The objective of this paper is to outline the reasons behind the minor changes made during the short, 4-year evolution of the technique, describe the key principles of the operation, and introduce a new mesh that, if elected to be used, automatically satisfies all the key principles of the procedure and guides the surgeon to perform the operation correctly. The worldwide reported result of the operation by experts and nonexperts alike is a recurrence and complication rate of less than 1%. When the key principles of the procedure, which, as reported by many authors, are easy to learn, perform, and teach, are respected, the operation results in an effectiveness (external validation) that is virtually the same as its efficacy (results of the experts), attesting to the simplicity of the procedure.

Abdomen↗
PubMedDate not supplied

Evolution of the vertical reduction mammaplasty: the S approach.

The vertical reduction mammaplasty has been popularized over recent years. It always produces marked puckering of the excess skin and requires revision surgery for the persistent dog-ears that develop. Minor complications are often common. As a result, the evolution with S approach is developed. A series of 36 consecutive patients who underwent the S approach reduction mammaplasty is presented. The S approach can be described as having 1) superior dermoglandular pedicle, 2) simple and safe S-shaped skin marking, 3) suspension of the residual glandular tissues transversely to the periosteum of the 5th rib, and 4) short-scar closure. The surgical techniques are described in a step-by-step fashion. An analysis is made of the results obtained from these patients. The mean follow-up period of this study is 21 months. As a result of surgical operation, the symptoms of breast hypertrophy were markedly improved. According to patient assessment, neck, back, or chest pain decreased from 64% to 25%, shoulder grooving improved from 56% to 25%, stooped posture decreased from 42% to 14%, intetrigo improved from 36% to 8%, psychological embarrassment decreased from 33% to 8%. The postoperative complications included minimal areolar epidermolysis (11%), hypertrophic scar (8%), etc. All mammograms revealed hypertrophic patterns of the breast. The glandular tissues removed had a mean of 480 g from each breast. Two breasts (3%) had fibroadenomas. The sternal notch-nipple distance changed from a mean of 30.5 cm preoperatively to 20.5 cm, the length of infraareolar scar was 9 cm in average. Eighty-one percent of patients had minimal postoperative ptosis, and the sensitivity of nipple-areola complex was unchanged in 75% of patients. Nine patients (24%) retained the ability to lactate for more than 1 month postoperatively. Twenty-two patients (61%) were very satisfied with their operation, and eight (22%) were adequately satisfied. The technique presented is a simple and safe procedure that provides satisfactory results for patients with breast hypertrophy.

Female↗
PubMed1993

Hippocampus minor and man's place in nature: a case study in the social construction of neuroanatomy.

In mid-19th century Britain the possibility of evolution and particularly the evolution of man from apes was vigorously contested. Among the leading antievolutionists was the celebrated anatomist and paleontologist Richard Owen and among the leading defenders of evolution was Thomas Henry Huxley. The central dispute between them on human evolution was whether or not man's brain was fundamentally unique in having a hippocampus minor (known today as the calcar avis), a posterior horn in the lateral ventricle, and a posterior lobe. The author considers the background of this controversy, the origin and fate of the term hippocampus minor, why this structure became central to the question of human evolution, and how Huxley used it to support both Darwinism and the political ascendancy of Darwinians. The use of ventricular structures to distinguish humans from other animals appears to reflect an importance given to the ventricles that stretches back to ancient Greek medicine. This account illustrates both the extraordinary persistence of ideas in biology and the role of the political and social matrix in the study of the brain.

Anatomy, Comparative↗
PubMed1982

The decline of official language minorities in Quebec and English Canada.

"This paper considers the evolution of French outside of Quebec and the English in Quebec.... The total historical set of national data on ethnicity, mother tongue, knowledge of official languages and home language [is first presented]. The 120 year stability showing French at around 30 percent of the national total is a function of compensating factors including high French fertility and high English immigration. During the 1960s both of these demographic supports disappeared and thus mobility across linguistic lines has become a particularly sensitive issue. "The picture with regard to French outside of Quebec has changed rather radically in the last thirty-five years. For instance, there was one French child to every nine in 1941 and one to every twenty-one children in 1976. While the English of Quebec were once represented in various parts of the province, their strength is now largely limited to the Montreal metropolitan area which includes 76 percent of the English mother tongue group. Outside of Montreal, the English amounted to 7.9 percent of Quebec's population in 1941 and 5.6 percent in 1976. The paper concludes with a discussion of the social factors that underlie these trends and their relevance to the models of institutional and territorial bilingualism." (summary in FRE)

Africa↗
PubMed2000

Variability and immunogenicity of human immunodeficiency virus type 1 p24 gene quasispecies.

Despite the conserved nature of the human immunodeficiency virus type 1 (HIV-1) gag gene, multiple quasispecies of the p24 gene coexist in HIV-1-infected patients. We cloned and sequenced 31 p24 genes from four HIV-1-infected patients. The intrapatient homology between the p24 genes ranged from 97.1 to 99.1%, whereas the interpatient homology ranged from 91.5 to 93.8%, suggesting a host-specific evolution. Synonymous and nonsynonymous nucleotide changes were evenly distributed in the p24 gene, with 27 and 28%, respectively, located within host human leukocyte antigen class I recognition sites. This would suggest only a minor influence from the host cytotoxic T-cell response on the evolution of the p24 gene. The importance of minor variations within p24 was analyzed by designing DNA-based immunogens from two distinct p24 quasispecies genes simultaneously derived from one patient. In plasmid-immunized H-2(b), H-2(d), and H-2(k) haplotype mice, a clear influence from the host major histocompatibility complex was noted on the immune responses, fully consistent with those noted when a recombinant p24 protein is used as the immunogen. The two p24 DNA immunogens did not differ in their immunogenicity, indicating that the limited genetic variability (<1%) had little influence on the immune responses.

Acquired Immunodeficiency Syndrome↗
PubMed2002

Bcl-6 p53 mutations in lymphomas carrying the bcl-2/Jh rearrangement.

BACKGROUND AND OBJECTIVES: The t(14;18)(q32;q21) chromosomal translocation is the hallmark of follicular lymphomas (FL). The translocation induces the overexpression of the Bcl-2 protein and prolongs the survival of clonogenic cells. Tumor cells may acquire additional molecular alterations that may be associated with histologic progression or with chemo-resistance. DESIGN AND METHODS: We analyzed the distribution and association of bcl-6 and p53 mutations in 55 consecutive bcl-2/Jh+ lymphoma samples derived from 43 patients obtained at the time of diagnosis and, in 5 of these patients, during follow-up. A total of 29 bcl-6 point mutations were detected in seventeen patients (40%) associated with major or minor breakpoints of the bcl-2/Jh fusion gene. In seven cases a p53 mutation was detected. Three cases corresponded to FL with the minor breakpoint in the bcl-2 gene and these patients had a favorable clinical evolution, whereas the 4 patients with p53 mutations and the major breakpoint had a bad clinical outcome with morphologic transformation to high-grade lymphoma in three cases. The sequential analysis of 5 patients showed a different timing in the acquisition of mutations: one patient showed bcl-6 and p53 mutations at diagnosis, another patient showed bcl-6 mutations at diagnosis and acquired a p53 mutation later whereas the third patient had a p53 mutation before the appearance of the bcl-6 mutation. RESULTS: We did not find significant differences in survival between patients with FL who showed exclusively bcl-6 mutations and those without bcl-6 mutations, but those patients with a high International Progostic Index score and p53 mutations showed the lowest overall survival (p = 0.002). INTERPRETATION AND CONCLUSIONS: These findings suggest that bcl-2/Jh lymphomas show molecular heterogeneity and that bcl-6 and p53 mutations may be acquired during the evolution of such lymphomas. Bcl-6 mutations, by themselves, do not seem to be associated with a bad prognosis. Rearrangements at the minor bcl-2 locus may have a different molecular evolution.

Adult↗
PubMed1983

Iodide-dependent catalatic activity of thyroid peroxidase and lactoperoxidase.

Thyroid peroxidase (TPO) and lactoperoxidase (LPO) display significant catalatic activity at pH 7.0 in the presence of low concentrations of iodide, based both on measurements of H2O2 disappearance and O2 evolution. In the absence of iodide only minor catalatic activity was detected. The stimulatory effect of iodide could not be explained by protection of the enzymes against inactivation by H2O2. A mechanism is suggested involving an enzyme-hypoiodite complex as an intermediate.

Catalysis↗
PubMed1994

The evolutionary expansion of the trypanosomatid flagellates.

The trypanosomatids combine a relatively uniform morphology with ability to parasitise a very diverse range of hosts including animals, plants and other protists. Along with their sister family, the biflagellate bodonids, they are set apart from other eukaryotes by distinctive organisational features, such as the kinetoplast-mitochondrion and RNA editing, isolation of glycolysis enzymes in the glycosome, use of the flagellar pocket for molecular traffic into and out of the cell, a unique method of generating cortical microtubules, and bizarre nuclear organisation. These features testify to the antiquity and isolation of the kinetoplast-bearing flagellates (Kinetoplastida). Molecular sequencing techniques (especially small subunit ribosomal RNA gene sequencing) are now radically reshaping previous ideas on the phylogeny of these organisms. The idea that the monogenetic (MG) trypanosomatids gave rise to the digenetic (DG) genera is losing ground to a view that, after the bodonids, the African trypanosomes (DG) represent the most ancient lineage, followed by Trypanosoma cruzi (DG), then Blastocrithidia (MG), Herpetomonas (MG) and Phytomonas (DG), with Leptomonas (MG), Crithidia (MG), Leishmania (DG) and Endotrypanum (DG) forming the crown of the evolutionary tree. Vast genetic distances (12% divergence) separate T. brucei and T. cruzi, while the Leishmania species are separated by very short distances (less than 1% divergence). These phylogenetic conclusions are supported by studies on RNA editing and on the nature of the parasite surface. The trypanosomatids seem to be able to adapt with ease their energy metabolism to the availability of substrates and oxygen, and this may give them the ability to institute new life cycles if host behaviour patterns allow. Sexual processes, though present in at least some trypanosomatids, may have played only a minor part in generating diversity during trypanosomatid evolution. On the other hand, the development of altruistic behaviour on the part of some life cycle stages may be a hitherto unconsidered way of maximising fitness in this group. It is concluded that, owing to organisational constraints, the trypanosomatids can undergo substantial molecular variation while registering very little in the way of morphological change.

Animal Population Groups↗
PubMed1987

Chromosomal progression of malignant human gliomas from biopsy to establishment as permanent lines in vitro.

Karyotypes of four malignant human gliomas were followed from direct preparation and/or short-term culture through their establishment in vitro to determine whether the cultured cells maintained the original karyotypes, or were the products of selection, progression, or alteration in vitro. The karyotypes of these four human glioma-derived cell lines showed the same evolutionary pattern consisting of a doubling of the stem line or a closely related population; one line changed ploidy again to near-pentaploid. Marker types seen originally were generally retained, but new markers were acquired in the later passages. We concluded that the eventual chromosomal compositions of these four human glioma-derived cell lines were the products of karyotypic evolution, rather than simple selection of a minor population of polyploid cells.

Cell Line↗
PubMed1999

Microsatellite and morphological analysis of population structure in the parthenogenetic freshwater snail Melanoides tuberculata: insights into the creation of clonal variability.

The distribution of variability was studied at various geographical scales in the tropical freshwater snail Melanoides tuberculata, in order to analyse the role of factors shaping this distribution, including the mating system and population dynamics. This parthenogenetic polyploid species reproduces mainly asexually, with males occurring at low frequency. About 800 individuals (38 sites) were sampled from Africa and the Middle East, where the species originated, and from recently colonized habitats in South and Central America, and especially the island of Martinique. We first described variation of general aspects and ornamentation of the shells. This analysis confirms the existence of discrete morphs. Second, individuals were studied at three microsatellite loci, showing that each morph is a genetic clone with some minor variation compatible with models of microsatellite evolution. The genetic analysis also showed much more variation within than between clones. However, two populations from Africa exhibited a large amount of variability, and a mixture of sexual and asexual reproduction might explain these genetic patterns. The worldwide distribution of variability is, therefore, compatible with the African origin of the species, and the introduction of a few clones in other parts of the world. These results also suggest that the distribution of variability in Martinique is influenced by flooding events, and that two morphs from Martinique can be interpreted as hybrids between two pre-existing morphs, based on morphological, genetic and geographical arguments.

Journal Article↗
PubMed2005

Temperature-induced dynamical conformational disorder in 4-vinyl benzoic acid molecular crystals: a molecular simulation study.

Extensive molecular simulations are carried out as a function of temperature to understand and quantify the conformational disorder in molecular crystals of 4-vinyl benzoic acid. The conformational disorder is found to be dynamic and associated with a flip-flop motion of vinyl groups. The population of minor conformer is less than 3% up to 300 K and is 13.2% at 350 K and these results are consistent with the experimental observations. At still higher temperatures, the population of minor conformer increases up to 25%. The evolution of structure at both molecular and unit-cell level of the molecular crystal as a function of temperature has been characterized by various quantities such as radial distribution functions, average cell parameters, volume, and interaction energies. The van't Hoff plot shows a nonlinear behavior at lower temperatures as it has been reported recently by Ogawa and co-workers in the case of stilbene, azobenzene, and N-(4-methylbenzylidene)-4-methylaniline molecular crystals. A set of rigid body simulations were also carried out to quantify the effect of conformational disorder on structural quantities such as unit-cell volume and interaction energy. The anomalous shrinkage of vinyl C=C bond length as a function of temperature has been explained by combining the results of simulations and a set of constrained optimizations using ab initio electronic structure calculations for various molecular structures differing in torsional angle.

Journal Article↗
PubMed2001

Multichoice minority game.

The generalization of the problem of adaptive competition, known as the minority game, to the case of K possible choices for each player, is addressed, and applied to a system of interacting perceptrons with input and output units of a type of K-state Potts spins. An optimal solution of this minority game, as well as the dynamic evolution of the adaptive strategies of the players, are solved analytically for a general K and compared with numerical simulations.

Journal Article↗
PubMed1968

Photosynthetic Enhancement in the Diatom Phaeodactylum tricornutum.

Enhancement phenomena in photosynthesis of the diatom Phaeodactylum tricornutum Lewin were studied by means of a Haxo oxygen electrode and 2 monochromatic light beams. It was necessary to correct for a minor non-linearity in rate oxygen evolution vs. intensity similar to that reported for Chlorella. Action spectra on complementary backgrounds and derived enhancement spectra were compared to in vivo absorption spectra in identifying the character of pigment systems 1 and 2. Fucoxanthin, chlorophyll c, and chlorophyll a-670 are clearly assignable to pigment system 2 which absorbs in excess at wavelengths 400 to 678 mmu. Chlorophyll a-1 (and a portion of the fucoxanthin) are assignable to pigment system 1 which absorbs in excess at wavelengths 678 to 750 mmu. Enhancement values were generally lower than those observed in Chlorella or Anacystis and lead to conclusion that diatom pigmentation provides an effective light harvesting apparatus.

Journal Article↗
PubMed1997

Contributions to the history of psychology: CIX. Note on an oral history of C. Kermit Phelps: an 89-year-old African American clinical psychologist.

During late 1996 and early 1997, the authors conducted four structured interviews with C. Kermit Phelps, an 89-year-old black psychologist who spent his professional career at the Veterans Administration Hospital in Kansas City, Missouri. Interview topics cover Dr. Phelps' personal and professional history, the evolution of clinical psychology, and issues surrounding minorities in the profession of psychology. This brief article provides an overview of some findings as a comprehensive account of the interviews will require considerable time to prepare.

Black or African American↗
PubMed1990

[Antenatal diagnosis and ethical problems].

The fast development of techniques detecting diseases or malformations of the fetus during the 2nd third of pregnancy has led to a real evolution in our knowledge. We can recognize minor or major abnormalities, as well as many hereditary or acquired diseases. This revolution raises considerable ethical problems because, at the same time, our ability to receive and operate the children with malformations as early as birth is ever improving. And yet the mothers often ask for induced abortion. What are we supposed to do? What are the acceptable limits?

Abortion, Therapeutic↗