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Results for “evolutionary potentiation”

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At least 253 records · Page 14Linked to original sources
PubMed2005

Reproduction and hybrid load in all-hybrid populations of Rana esculenta water frogs in Denmark.

All-hybrid populations of the water frog, Rana esculenta, are exceptional in consisting of independently and to some extent sexually reproducing interspecific hybrids. In most of its range R. esculenta reproduces hemiclonally with one of the parental species, R. lessonae or R. ridibunda, but viable populations of diploid and triploid hybrids, in which no individuals of the parental species have been found, exist in the northern part of the range. We test the hypothesis that nonhybrids arise every year in these all-hybrid populations, but die during larval development. Microsatellite markers were used to determine the genotypes of adults and abnormal and healthy offspring in three all-hybrid populations of R. esculenta in Denmark. Of all eggs and larvae, 63% developed abnormally or died, with some being nonhybrid (genomes matching one of the parental species), many being aneuploid (with noninteger chromosome sets), a few being tetraploid, and many eggs possibly being unfertilized. The 37% surviving and apparently healthy froglets were all diploid or triploid hybrids. In all three populations, gametogenesis matched the pattern previously described for all-hybrid R. esculenta populations in which most triploid adults have two R. lessonae genomes. This pattern was surprising for the one population in which triploid adults had two R. ridibunda genomes, because here it leads to a deficiency of gametes with an R. lessonae genome and should compromise the stability of this population. We conclude that faulty gametogenesis and mating between frogs with incompatible gametes induce a significant hybrid load in all-hybrid populations of R. esculenta, and we discuss compensating advantages and potential evolutionary trajectories to reduce this hybrid load.

Animals↗
PubMed1990

Primary structure of the gene coding for the haemagglutinin of influenza virus A/Leningrad/385/80(H3N2): detection of a point mutation responsible for the antigenic drift.

Primary structure of the gene coding for haemagglutinin (HA-gene) of influenza virus A/Leningrad/385/80(H2N2) isolated during the epidemics of influenza in Leningrad in 1980 was determined. The close relationship of HA gene of this virus to the corresponding gene of the virus A/Bangkok/1/79(H3N2) was confirmed. It was shown that a single mutation in an antigenic site (the change from isoleucine to leucine at position 51 of HA1 gene) caused an antigenic drift. One silent mutation was detected (nucleotide 428 of HA1 gene) which points at the relatedness of strains A/Leningrad/385/80 with A/Bangkok/2/79 and with other more recent strains. These data allowed to determine the position of the strain A/Leningrad/385/80 HA gene regarding to the evolutionary relationships of HA genes of influenza A (H3N2 subtype) viruses. The branch leading to the above-mentioned strain is supposed to start from a point common for strains isolated following A/Bangkok/1/79. The mutations of HA genes presented in this subgroup were analysed supporting the notion on limited evolutionary potential of the subtype H3N2 influenza viruses.

Amino Acid Sequence↗
PubMed1988

[Histopathology and prognosis of thymomas. Statistical analysis of 200 cases].

200 cases of thymoma operated on at the surgical centre of Marie-Lannelongue between 1955 and 1982 were reviewed and analysed statistically; their histology was compared and their evolutionary potential. Based on their degree of differentiation of the epithelial tumour component and on the proportion of non tumour associated lymphocytes, 4 histological types were defined: 1) Spindle-or-oval-cell thymomas where tumour cells reminiscent of normal involutive thymic cells were of small size with a tendency to form clusters, whorls or a glandular appearance; 2) Lymphocyte-rich thymomas where normal epithelial cells, few in number, reproduce the appearance of normal thymic cells; 3) Differentiated epithelial thymomas, comprised of large epithelial cells with abundant cytoplasm and clearly demarcated and often less numerous lymphocytes; 4) Undifferentiated epithelial thymomas, characterised by a poverty of lymphocytes and anaplastic epithelial cells with a raised nuclear cytoplasmic ratio, nuclear irregularity and mitosis. Statistically, there was a significant correlation between the degree of differentiation of the tumor and prognosis. Spindle-or-oval cell thymomas (type 1) and lymphocyte-rich thymomas (type 2) have an 80% survival at 5 years and a 75% survival at 10 years. Well differentiated epithelial thymomas of type 3 have a 75% survival at 5 years and a 50% survival at 10 years, finally undifferentiated epithelial thymomas (type 4); the survival rate was nil at 5 years.(ABSTRACT TRUNCATED AT 250 WORDS)

Anaplasia↗
PubMed1988

[Epilepsy from the pediatric and adolescent psychiatric viewpoint].

For epileptic children and their families, the development during the past two decades of drug treatment and social, educational and professional integration as well as psychological support has led to better help and comprehension. The traditional psychiatric concepts of an epileptic constitution or of a specific epileptic psychopathology in childhood and adolescence are nowadays subject of doubt. The idea of a linear relationship between organic and mental disease, postulating that symptoms are direct consequences of a brain dysfunction or lesion had to be abandoned. The physician has to deal with symptoms not only as organic dysfunctions but also as senseful in a psychodynamic context. Modern concepts are based on the idea of a structurally and functionally integrated psychophysical level of maturity, taking account of the individual psyche as well as of family and social relationships. This model allows to prevent social atrophy and to better understand and use the insufficiently exploited evolutionary potential in therapy and educational measures. Epileptic seizures are a particular and manifold charge for the child, not only on the social level, but very deeply in his inner life.

Adolescent↗
PubMedDate not supplied

Predictive value of phenotypic cytologic characteristics in early dysplastic cervical lesions.

Four phenotypic cytologic parameters (koilocytotic changes, binucleation, multinucleation and the presence of metaplastic dysplastic cells) were evaluated in the initial cervical smears from 89 women who presented with slight or moderate dysplastic changes and had an adequate follow-up. The cases were divided in two groups according to their evolution: the 51 cases constituting group I showed persistence or progression of the lesions while the 38 cases in group II showed regression. Koilocytosis in 40% or more of the cells in a smear proved to have the greatest predictive value as an indicator of a lesion with less risk of progression. Multinucleation may have a similar value, but to a lesser degree. Binucleation and metaplastic dysplastic cells showed no statistical differences between persistence cases and regression cases. A fifth parameter, positivity to human papillomavirus capsid antigen by the immunoperoxidase technique, doubled its frequency in the regression group. The evaluation of these variables may provide a means of assessing the evolutionary potential of precursor cervical lesions, based on these lesions' cytologic phenotypic profiles.

Cervix Uteri↗
PubMed1987

[Role and significance of the branchial system in cervico-facial morphogenesis].

The so-called "branchial" embryonic organization is in fact that of the part of the embryo subjacent to the anterior, encephalic portion of neural tube. It presents, in addition to its typical aspects, historically of importance, other more pertinent aspects related to its segmental character, its mode of development and its morphologic limits. Synthesis of all data is now possible due to recent precision of the origin of branchial muscles and the participation of ectomesochyme in its development. Findings indicate the predominant place and deep significant of this organization in overall embryonic development, for which it represents a determinant phase in itself, independent of evolutionary potential that can be possibly attributed to its vascular components.

Biological Evolution↗
PubMed1986

[Castelman's angiofollicular hyperplasia of multifocal form Apropos of 2 cases].

Castelman described as angiofollicular hyperplasia (AFH) a benign lymphovascular hyperplasia forming a single tumour, classically situated in the mediastinum. A multifocal lymph node form of AFH was individualised by Leibetseder and Turner about 10 years ago (MAFH). This is a rare syndrome, the clinical and biological characteristics of which are almost identical to angioimmunoblastic lymphadenopathy (AIL). The only difference is in the histology of the ganglia which shows changes of AFH. We report two cases of MAFH. In one patient with histological confirmation of splenic involvement the evolution was subacute. In the second case, the histological features of the lesions were observed to change during successive biopsies: appearances of AFH changed to typical AIL. This observation suggests that MAFH may be a disorder of the immune system. Usually considered as benign lymphatic hyperplasia with a chronic evolution, the long-term development of lymphoma poses the problem of the evolutionary potential of this condition, which may be likened to AIL in which lymphomatous transformation is also recognised.

Aged↗
PubMed1985

Physiological adaptations and the concepts of optimal reproductive strategy and physiological constraint in marine invertebrates.

The dominant 'demographic' theory of life history evolution supposes that different lifetime patterns of reproduction are the result of selection of alternative optimal solutions for the allocation of limited resources between somatic and reproductive functions. A number of trade-off possibilities have been recognized--those between current reproductive output and residual reproductive value and between fecundity and initial offspring size being considered especially important. Many theoretical studies assume that natural selection will favour the adoption of optimal solutions, but it has been pointed out that such solutions may not be obtainable due to design constraints and the development of physiological adaptations to specific reproductive traits which limit subsequent evolutionary potential. The validity of this idea is examined in this paper through a review of the major reproductive strategies available to marine invertebrates and the physiological adaptations associated with them. The ecologically important distinction between planktotrophic and lecithotrophic development is not necessarily associated with major physiological adaptations in the adults, but the distinction between strictly semelparous and iteroparous life histories is. This is demonstrated in a survey of the endocrinological and environmental control of reproductive processes in related organisms with contrasting modes or reproduction. Particular reference is made to the Polychaeta, in which the contrast between semelparous and iteroparous life histories is particularly marked. A similar contrast is found between cephalopoda and other mollusca, and the discussion of physiological adaptations is extended to include these groups and the Echinodermata.

Adaptation, Physiological↗
PubMedDate not supplied

[Fatigue fractures of the femoral neck. Retrospective study of 12 cases].

The authors are performing a retrospective analysis of 12 femoral neck stress fractures gathered between 1977 and 1984 at the "Hôpital Regional des Armées de Toulouse". These fractures, localised at the femoral neck, occur after the beginning of training course, latter than by the other localisations. This shift can be explained by the acceleration of training level at the end of the instruction and by the importance of the muscle strain as a releasing factor of this pathology. The clinical is stereotyped, the X ray photographs often point out a fracture mark or a osseous condensation in strips perpendicular to the forces lines. However, the evolutionary potential of this fracture is high and the authors find out three displaced fractures. So they suggest a usual practice towards this pathology including a osseous radiography and scintigraphy the diagnostic should be done during the useful phase of this affection which is the stress prefracture state: stereotyped clinical frame, normal radiography and positive osseous scintigraphy.

Adaptation, Physiological↗
PubMed1994

Transference: erotised, erotic, loving, affectionate.

Within a set of phenomena traditionally problematic for psychoanalysis, four types of erotic transference are outlined with a description of their dynamic genesis and related case histories (transference and countertransference developments, fundamental treatment procedures): erotised, erotic, loving, and affectionate transference. The first type is based mostly on psychotic modalities, the second on neurotic modalities. Both the loving and the affectionate transference, on the other hand, turn out to be clinical forms corresponding to a normal substantially same development, different from each other by virtue of a diverse level of maturation in the Oedipus complex: they often provoke--in analysts--a defensive stiffening which is harmful and--from the theoretical point of view--not above reproach. The work is particularly focused on the analytic evolution of a female patient who develops an amorous transference in which the defensive aspects prove to be less important than the potentially evolutionary ones. The treatment has been based--in particular--on the analytic utilisation of this transference. The last part of the contribution is devoted to the analysts' 'guarantee factors', which permit them to work in psychoanalysis with the 'highly explosive forces' of these transference configurations, maintaining a useful, rigorous, sensitive and sufficiently creative framework.

Adult↗
PubMed1996

Function of the Evx-2 gene in the morphogenesis of vertebrate limbs.

Vertebrate gene members of the HoxD complex are essential for proper development of the appendicular skeletons. Inactivation of these genes induces severe alterations in the size and number of bony elements. Evx-2, a gene related to the Drosophila even-skipped (eve) gene, is located close to Hoxd-13 and is expressed in limbs like the neighbouring Hoxd genes. To investigate whether this tight linkage reflects a functional similarity, we produced a null allele of Evx-2. Furthermore, and because Hoxd-13 function is prevalent over that of nearby Hoxd genes, we generated two different double mutant loci wherein both Evx-2 and Hoxd-13 were inactivated in cis. The analysis of these various genetic configurations revealed the important function of Evx-2 during the development of the autopod as well as its genetic interaction with Hoxd-13. These results show that, in limbs, Evx-2 functions like a Hoxd gene. A potential evolutionary scenario is discussed, in which Evx-2 was recruited by the HoxD complex in conjunction with the emergence of digits in an ancestral tetrapod.

Amino Acid Sequence↗
PubMed1997

Aging is a specific biological function rather than the result of a disorder in complex living systems: biochemical evidence in support of Weismann's hypothesis.

A concept postulating that aging is a specific biological function that promotes the progressive evolution of sexually reproducing species is reviewed. Death caused by aging clears the population of ancestors and frees space for progeny carrying new useful traits. Like any other important function, aging is mediated by several molecular mechanisms working simultaneously. At least three such mechanisms have been postulated thus far: 1) telomere shortening due to suppression of telomerase at early stages of embryogenesis; 2) age-related activation of a mechanism that induces the synthesis of heat shock proteins in response to denaturing stimuli; and 3) incomplete suppression of generation and scavenging of reactive oxygen species (ROS). None of these phenomena can kill the organism, but only weaken it, which becomes crucial under extreme conditions. This mechanism of age-induced death can be compensated for (within certain time limits) by several positive traits that greatly increase the evolutionary potential of species capable of performing this function. Similarly to apoptosis (programmed cell death), the programmed death of the body can be called "phenoptosis". Aging presumably belongs to the category of "soft" (extended in time and allowing a certain degree of compensation) phenoptosis, in contrast to "acute" phenoptosis; the death of salmon females immediately after spawning is a good example of the latter.

Aging↗
PubMed1997

[Arbovirus infections. From virus, mosquitoes, animals and humans].

Arboviruses occur throughout the world in plants and animals: reptiles, birds and mammals including man. These relatively recent RNA-containing viruses have great evolutionary potential and are a major cause of epidemics. Arboviruses exhibit a dual life cycle involving continual transmission to and from the vertebrate host and arthropod vector which ingests or inoculates the agent during blood meals. Agents belong to many different viral families and represent an important source of emerging diseases. Because of the mode of transmission is vectorial, spread can enhanced by man-made changes in the ecosystem. This risk is often underestimated. The population explosion provides a great opportunity for the progression of these arboviruses.

Animals↗
PubMed2006

Functionalization of carbon nanomaterials by evolutionary molecular engineering: potential application in drug delivery systems.

By virtue of the progress made in evolutionary molecular engineering, peptide aptamers that specifically recognize target molecules are now routinely created using a peptide phage display system. The system was originally developed for isolating peptides that specifically recognized biomacromolecules (e.g. proteinous receptors), but are now also being used to acquire peptide motifs that bind to inorganic materials, such as semiconductors, metals and carbon nanomaterials. We have created the peptide aptamer against carbon nanohorns, a vesicular carbon nanomaterial whose size is 80-100 nm in diameter. By combining the peptide motif that has affinity to the surfaces of carbon nanohorns with peptide aptamers that can target specific organs, we can functionalize the carbon nanomaterial to provide novel types of carriers for drug delivery systems.

Biomedical Engineering↗
PubMed1997

Phylogeny of cyanobacterial nifH genes: evolutionary implications and potential applications to natural assemblages.

DNA sequences of a fragment of nifH from diverse cyanobacteria were amplified, cloned and sequenced to determine the evolutionary relationship of nitrogenase within the cyanobacteria as a group, and to provide a basis for the identification of uncultivated strains of cyanobacteria in the environment. Analysis of 30 nitrogenase DNA and deduced amino acid sequences from cyanobacteria representing five major taxonomic subdivisions showed great variation in phylogenetic distances between the sequences. Sequences from heterocystous cyanobacteria formed a coherent cluster, in which branching forms did not form a clade distinct from the non-branching forms. Nitrogenase sequences from the unicellular cyanobacteria Gloeothece and Synechococcus sp. RF-1 formed a cluster, as did sequences from the genera Xenococcus and Myxosarcina. The nifH sequences of filamentous nonheterocystous cyanobacteria were not closely related to each other, forming deep branches with respect to the heterocystous cyanobacterial nifH sequences. The phylogeny of nifH based on amino acid sequences was consistent with taxonomic relationships among the strains; for example, a sequence obtained form a natural assemblage believed to be dominated by 'Lyngbya' clustered with nifH from Lyngbya lagerheimii. Results also indicate that the phylogeny of nifH among the cyanobacteria is largely consistent with the phylogeny of 16S rRNA, and furthermore that the nifH sequence can be used to identify uncultivated strains of nitrogen-fixing cyanobacteria.

Amino Acid Sequence↗
PubMed2006

Systematic analysis of head-to-head gene organization: evolutionary conservation and potential biological relevance.

Several "head-to-head" (or "bidirectional") gene pairs have been studied in individual experiments, but genome-wide analysis of this gene organization, especially in terms of transcriptional correlation and functional association, is still insufficient. We conducted a systematic investigation of head-to-head gene organization focusing on structural features, evolutionary conservation, expression correlation and functional association. Of the present 1,262, 1,071, and 491 head-to-head pairs identified in human, mouse, and rat genomes, respectively, pairs with 1- to 400-base pair distance between transcription start sites form the majority (62.36%, 64.15%, and 55.19% for human, mouse, and rat,respectively) of each dataset, and the largest group is always the one with a transcription start site distance of 101 to 200 base pairs. The phylogenetic analysis among Fugu, chicken, and human indicates a negative selection on the separation of head-to-head genes across vertebrate evolution, and thus the ancestral existence of this gene organization. The expression analysis shows that most of the human head-to-head genes are significantly correlated,and the correlation could be positive, negative, or alternative depending on the experimental conditions. Finally, head to-head genes statistically tend to perform similar functions, and gene pairs associated with the significant cofunctions seem to have stronger expression correlations. The findings indicate that the head-to-head gene organization is ancient and conserved, which subjects functionally related genes to correlated transcriptional regulation and thus provides an exquisite mechanism of transcriptional regulation based on gene organization. These results have significantly expanded the knowledge about head-to-head gene organization. Supplementary materials for this study are available at http://www.scbit.org/h2h.

Animals↗