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At least 163 records · Page 9Linked to original sources
PubMed2000

Solitary tract nuclei in acute heart failure.

BACKGROUND AND PURPOSE: Symmetrical necrosis of the brain stem nuclei has been described as a consequence of severe transitory cerebral hypoxia mainly in neonates or young adults who experienced an episode of acute ischemia due to transitory acute heart failure. We report selective bilateral lesions of the solitary tract nuclei in 5 adults with short survival intervals after acute heart failure. METHODS: In 5 patients who died due to cardiovascular pathology, histological examination was performed on multiple samples of cerebral hemispheres, on transverse sections of the midbrain and pons, and on transverse serial sections of the medulla stained with hematoxylin-eosin, Klüver-Barrera, and Luxol fast blue. The 3-dimensional reconstruction of the extension and topography of the medullary lesions was obtained with computed image analysis. RESULTS: In 4 subjects who died soon after an episode of acute heart failure (range of survival 10 hours to 2 days), the dorsal portion of the solitary tract nuclei showed an eosinophilic roundish aspect bilaterally. In their context, the neurons showed changes characteristic of ischemic coagulation necrosis. In a fifth patient, a 32-year-old man who died 15 days after an episode of cardiac arrest, 2 circumscribed symmetrical infarcts with macrophagic and astrocytic reactions were found at the same level. The topography of the lesions and the inflammatory reaction and gliosis of patient 5 suggest that the findings in the other 4 patients correspond to initial features of selective lesions of the solitary tract nuclei after acute heart failure: the short interval of survival prevented the evolution of the reactive process. The nucleus is localized at the watershed zone between the terminal branches of the medullary collateral vessels of the vertebral arteries, thus representing the last meadow in the case of sudden fall of the systemic blood flow due to acute heart failure. The absence of lesions of other medullary and pontine nuclei accounts for a selective vulnerability of the neurons of the solitary tract nuclei, and the selective dendritic lesions suggest an excitotoxic component to ischemic cell death. CONCLUSIONS: The commonly accepted resistance of the medullary centers to ischemic hypoxia in adults apparently could be due to the rapidity of death, which prevents the evolution of lesions that can be diagnosed. In addition, minor lesions in the medullary tegmentum after acute heart failure could play a role in the prevention of the resumption of autonomous cardiac and respiratory functions despite life-saving procedures.

Adult↗
PubMed1993

Replication of damaged DNA and the molecular mechanism of ultraviolet light mutagenesis.

On UV irradiation of Escherichia coli cells, DNA replication is transiently arrested to allow removal of DNA damage by DNA repair mechanisms. This is followed by a resumption of DNA replication, a major recovery function whose mechanism is poorly understood. During the post-UV irradiation period the SOS stress response is induced, giving rise to a multiplicity of phenomena, including UV mutagenesis. The prevailing model is that UV mutagenesis occurs by the filling in of single-stranded DNA gaps present opposite UV lesions in the irradiated chromosome. These gaps can be formed by the activity of DNA replication or repair on the damaged DNA. The gap filling involves polymerization through UV lesions (also termed bypass synthesis or error-prone repair) by DNA polymerase III. The primary source of mutations is the incorporation of incorrect nucleotides opposite lesions. UV mutagenesis is a genetically regulated process, and it requires the SOS-inducible proteins RecA, UmuD, and UmuC. It may represent a minor repair pathway or a genetic program to accelerate evolution of cells under environmental stress conditions.

DNA Damage↗
PubMedDate not supplied

[Genomic instability in picornaviruses].

Picornaviruses are small animal RNA viruses and include wtiological agents of poliomyelitis, foot and mouse disease, hepatitis A, etc. Replication of their genome results in many mutations, which are close in number to a viability threshold. Hence every virus population contains a great variety of genomes and represents a quasispecies. Covalent rearrangements (deletions, insertions, recombination) also contribute to genome variation and arise by replicative and nonreplicative mechanisms, which are still poorly understood. Only a minor fraction of all new changes is fixed during evolution. The fixation is based on two principally different ways of selection: with (positive and negative selection) and without (random selection of nonrepresentative variants) regard to the phenotype. In natural evolution of picornaviruses, the latter way is prevalent, and most fixed mutations are phenotypically neutral. To understand the mechanisms of evolution, it is necessary to evaluate the biological significance of particular genetic changes. Several new approaches to this problem have recently been proposed.

Biological Evolution↗
PubMed1984

The evolution of ocular onchocerciasis in the Volta River Basin Area over a period of five years of vector control.

The results of an ophthalmological evaluation conducted in seven West African savannah villages before and after 5 years of vector control, were analysed to determine the effect of an interrupted or greatly reduced transmission of Onchocerca volvulus on the evolution of ocular onchocerciasis. Cross-sectional data showed a significant reduction of the prevalence of ocular onchocerciasis in five of the villages, and the rates of irreversible ocular lesions and blindness were generally lower after 5 years of vector control. A longitudinal study of a defined population showed that the ocular status of most patients with ocular onchocerciasis remained stable or improved over the 5 year period, particularly in lightly infected cases. The evolution of ocular onchocerciasis showed a deterioration in a minor proportion, restricted to cases of already existing severe lesions, resulting in blindness. A comparison of ophthalmic data from adjacent areas without vector control, indicates that a five year period of vector control may reduce the risk of developing eye lesions or blindness due to onchocerciasis by 50%.

Adolescent↗
PubMed1994

[Percutaneous endoscopic gastrostomy: study on 35 patients].

BACKGROUND: A review of the technique, indications, complications and follow up of percutaneous endoscopic gastrostomy (PEG) was performed. METHODS: Thirty-five patients in whom a PEG had been placed according to the Ponsky technique from 1991 to 1993 were analyzed 27 of whom had neurologic disease, 6 tumoral diseases and 2 other causes. RESULTS: PEG was carried out in 33 patients with no incidences while the technique could not be performed in 2 since the point could not be identified by transillumination in the gastric wall. No immediate complications were observed. Seven minor early complications were presented as wound infection with the cannula being withdrawn in only one case due to persistence of the infection. Five late complications were reported: 1 severe (gastrocholic fistula) and 4 minor (2 cannula obstructions, 1 displacement and 1 infection). Evolution was followed in 31 patients with the cannula being withdrawn in 4 (2 because of complications and in the other 2 on initiation of oral diet). The cannula was substituted at 120 and 360 days in 2 patients. Sixteen patients died, 5 during the first 30 days due to the primary disease, with only one case (aspirative pneumonia) being related to the PEG. The PEG continues functioning in 11 patients. CONCLUSIONS: Percutaneous endoscopic gastrostomy for feeding is a simple technique which may be carried out in most patients with scarce severe complications, allowing a good nutritional state and improving the quality of life of patients requiring prolonged enteral feeding.

Adult↗
PubMed1975

[Emergency aorto-coronary bypass. Indications and results in a homogenous series of 50 patients].

Emergency myocardial vascularization through an aorta-to-coronary by-pass has been extended recently to acute evolutive accidents of coronary artery disease: either to its minor forms, as the menace syndrome, or its more severe forms, such as complicated myocardial infarction. This study aimed at a retrospective analysis of 50 patients, all operated upon as an emergency, by the same surgical team. The problems peculiar to any group of indications, and the practical and theoretical problems posed by extension of this type of emergency surgery were discussed.

Adult↗
PubMed2004

[Neurodevelopment of extremely low birthweight infants born in Erasmus Hospital between 1992 and 2001].

Survival of extremely low birth weight infants has dramatically improved in the last decade of the twentieth century. The objective of our study was to evaluate the neurological evolution of the surviving infants because frequent motor, sensitive and psychological disturbances are related. Prospective, longitudinal study in a population of newborns, nursed in our neonatal intensive care unit and born between 1992 and 2001 with less than 1.000 g and/or less than 28 weeks of gestational age (GA). Neurological assessment of outcome was made using the neurodevelopmental score (O.M.S. 1988) at 6, 9, 12, 18, 24 and 36 months. Neurological follow-up every year and neuropsychological testing at 3, 5 and 8 years. Only children with at least 2 years of follow-up were included. The children were grouped in 3 categories: M (major neurological handicap), m (minor neurological handicap), N (normal neurological outcome). To evaluate the evolution with time, we compared the results from the first period (1992 to 1996) to the second part of this decade (1997 to 2001). Mortality fell from 38% (27/70) in the first period (1992-1996) to 18% (8/44) in the second one (1997-2001) (p = 0.02) including neonates of less than 25 weeks GA. Neurodevelopmental status improved and severe brain lesions decreased (25% with intraventricular haemorrhage III & IV and cystic periventricular leukomalacia versus 6% in the second period) (p = 0.017). Major handicap fell from 26% (9/34) to 16% (5/31) and normal neurological evolution raised from 15% (5/34) to 48% (15/31) (p = 0.013). With the survival of newborns less than 28 weeks, the severe ocular complications increased: 6% (5/79). In conclusion, mortality and quality of life have significantly improved in the past 10 years in our service. Severe brain lesions have decreased under a better multifactorial management. Nevertheless when the gestational age of the surviving babies diminishes, ocular sequelae increase. We still think that prematurity remains a burden for the child, his family and the society.

Brain↗
PubMed1989

Crystallite orientation discontinuities and the evolution of mammalian enamel--or, when is a prism?

The nature and relationship of crystallite domains have been explored in fossil and extant enamels spanning an evolutionary period of 200 x 10(6) years. Minor crystallite orientation discontinuities, either linear or planar, were found to be consistent characteristics of all specimens examined. The earliest minor discontinuity is linear (convergence line), shown here in Oligokyphus and Eozostrodon. The convergence line would be the result of the occasional development of a conical Tomes' process to the parent ameloblast. An increase in number and regularity of convergence lines, shown here in Haldanodon, marks the appearance of a regular pseudoprismatic enamel structure. The second minor discontinuity to appear is planar (seam), shown here in a dryolestid eupantothere. The seam has previously been deduced to relate developmentally to a central groove on the sloping floor-wall of the Tomes' process pit. Coincident with the appearance of the seam is that of a rudimentary major planar discontinuity which does not enclose a domain to constitute what would normally be acknowledged as a prism. Its developmental basis would be the establishment of a steep wall and floor (however partial in circumference) to the Tomes' process pit. The extent of the major planar discontinuities was found to increase subsequently to enclose a classically recognizable prismatic domain, shown here in Amphiperatherium, Hassianycteris, Smilodon and Felis. This would be consistent with the further development of a definitive floor and wall to the Tomes' process pit. The sequential appearance of minor linear, minor planar and major planar discontinuities in crystallite orientation is seen as fundamental to the evolution of mammalian enamel structure.

Animals↗
PubMed2006

Impacts of gene essentiality, expression pattern, and gene compactness on the evolutionary rate of mammalian proteins.

Understanding the determinants of the rate of protein sequence evolution is of fundamental importance in evolutionary biology. Many recent studies have focused on the yeast because of the availability of many genome-wide expressional and functional data. Yeast studies revealed a predominant role of gene expression level and a minor role of gene essentiality in determining the rate of protein sequence evolution. Whether these rules apply to complex organisms such as mammals is unclear. Here we assemble a list of 1,138 essential and 2,341 nonessential mouse genes based on targeted gene deletion experiments and report a significant impact of gene essentiality on the rate of mammalian protein evolution. Gene expression level has virtually no effect, although tissue specificity in expression pattern has a strong influence. Unexpectedly, gene compactness, measured by average intron size and untranslated region length, has the greatest influence. Hence, the relative importance of the various factors in determining the rate of mammalian protein evolution is gene compactness > gene essentiality approximately tissue specificity > expression level. Our results suggest a considerable variation in rate determinants between unicellular organisms such as the yeast and multicellular organisms such as mammals.

Animals↗
PubMed1998

[Physiopathology of iodine deficiency].

The process of goitrogenesis is likely to be the consequence of an increased TSH stimulation linked to an initial reduction of circulating thyroid hormone caused by iodine deficiency (ID). Other growth factors associated to TSH may have a role in the pathogenesis of goiter. Natural history of goiter is the evolution towards nodularity and functional autonomy. This phenomenon is due to the heterogeneity of thyroid follicular cells, some of which, with an intrinsic elevated growth rate, under the stimulation of ID progress to nodule formation and hyperfunction. In multinodular goiter TSH receptor mutations activating adenylate cyclase-cAMP pathway were found. In a recent epidemiological survey it was shown that nodular goiter increased with the age, being about 1% in schoolchildren and 23% in the adults (56-75 years). Also nodular autonomy and hyperthyroidism were more frequent in the 36-75 year age group. Severe ID is also cause of endemic cretinism. In Europe minor neuropsychological impairments and cognitive deficits were described in areas of moderate ID. The exposure to a mild ID during fetal life causes minor neuropsychological damage. In conclusion, ID is responsible of goiter and its evolution towards nodularity and functional autonomy. Severe ID is also cause of endemic cretinism, while cognitive deficits and minor neuropsychological impairments were found in mild to moderate ID.

Adult↗
PubMed2004

Diminishing returns in social evolution: the not-so-tragic commons.

A challenge for evolutionary theory is to understand how cooperation can occur in the presence of competition and cheating, a problem known as the tragedy of commons. Here I examine how varying the fitness returns from reproductive competition or cooperation affects the negative impact of competition on a social group. Varying linear returns does not affect the impact of competition. However, diminishing returns, where additional investments in either competition or cooperation give smaller and smaller rewards, reduce the effects of competition on the group. I show that diminishing returns are common in many systems, including social vertebrates, microbes, social insects and mutualisms among species. This suggests that the tragedy of the commons is not so tragic and that the disruptive effects of competition upon social life will often be minor.

Animals↗
PubMed1996

[Comparative study of the stability of oral anticoagulant treatments (warfarin vs acenocoumarol)].

PURPOSE: To compare the stability of the effect of two oral anticoagulants, one of them (acenocoumarol) with a short half life and the other one with a long half life (warfarin) in patients in the stable phase of treatment (at least 2 months with treatment before entering the study). PATIENTS AND METHODS: During a year period (January-December 1993) a comparative study of two groups of 53 patients each was performed: group 1 patients were treated with warfarin and group 2 with acenocoumarol. Both groups were paired with respect to age, sex, diagnosis for anticoagulant therapy and desired therapeutic range (INR 3-4.5). The mean value of controls per patient, the dosage changes, the evolutive controls and the incidence of haemorrhagic and thromboembolic episodes were studied. RESULTS: The controls performed in group 1 were 728 in total with a mean value of 13.74 per patient and 800 in group 2 with a mean value of 15.09 per patient. A change in the dosage was performed in 214 controls in patients of group 1 and in 269 of group 2. Seventeen patients had 38 haemorrhagic episodes (2 major and 36 minor) in group 1, and 6 of group 2 had 20 episodes (2 major and 18 minor). Significant differences were observed in the mean value of controls (p = 0.04), the evolutive controls (p < 0.001), the global incidence of haemorrhages (p = 0.008) and incidence of minor ones (p = 0.006). No significant differences in dosage were observed. In both groups no thromboembolic episodes during the period of study were reported. CONCLUSIONS: Anticoagulant treatment with warfarin is more stable than with acenocoumarol. The total controls and the mean value of controls per patient are decreased. Nevertheless with warfarin we have observed a greater incidence of haemorrhagic episodes.

Adult↗
PubMed1999

[Functional dynamics of impending overt hypothyroidism: spontaneous evolution in patients in the years before the beginning of treatment].

The syndrome of subclinical hypothyroidism, with its clinical and metabolic consequences, is frequent. Only a minority of these patients will eventually become overtly hypothyroid. It was the aim of the present study to analyse the spontaneous evolution over 10 years of 27 patients with subclinical hypothyroidism who became overtly hypothyroid (group A). For comparison, 27 patients remaining subclinically hypothyroid and matched for their TSH concentrations were characterised (group B). In group A, continuous increase of TSH concentrations was observed over the whole observation period (p = 0.002; ANOVA). The concentrations of fT4 remained initially stable, and only fell at a late stage in the three years before overt hypothyroidism (p = 0.0001; ANOVA). The concentrations of total T3 remained normal throughout the observation period. Thyroid reserve was already impaired at the beginning and during the whole study period. In contrast, these thyroid parameters of patients of group B remained unchanged over 10 years, and thyroid reserve remained normal. The pathogenesis of overt hypothyroidism is a graded process. Increasing concentrations of TSH, a decrease of fT4 and impaired thyroid reserve are predictors of overt thyroid failure.

Analysis of Variance↗
PubMed2003

Alternative splicing and evolution.

Alternative splicing is a critical post-transcriptional event leading to an increase in the transcriptome diversity. Recent bioinformatics studies revealed a high frequency of alternative splicing. Although the extent of AS conservation among mammals is still being discussed, it has been argued that major forms of alternatively spliced transcripts are much better conserved than minor forms. It suggests that alternative splicing plays a major role in genome evolution allowing new exons to evolve with less constraint.

Alternative Splicing↗
PubMed2002

Genomic analysis of the terpenoid synthase ( AtTPS) gene family of Arabidopsis thaliana.

A family of 40 terpenoid synthase genes ( AtTPS) was discovered by genome sequence analysis in Arabidopsis thaliana. This is the largest and most diverse group of TPS genes currently known for any species. AtTPS genes cluster into five phylogenetic subfamilies of the plant TPS superfamily. Surprisingly, thirty AtTPS closely resemble, in all aspects of gene architecture, sequence relatedness and phylogenetic placement, the genes for plant monoterpene synthases, sesquiterpene synthases or diterpene synthases of secondary metabolism. Rapid evolution of these AtTPS resulted from repeated gene duplication and sequence divergence with minor changes in gene architecture. In contrast, only two AtTPS genes have known functions in basic (primary) metabolism, namely gibberellin biosynthesis. This striking difference in rates of gene diversification in primary and secondary metabolism is relevant for an understanding of the evolution of terpenoid natural product diversity. Eight AtTPS genes are interrupted and are likely to be inactive pseudogenes. The localization of AtTPS genes on all five chromosomes reflects the dynamics of the Arabidopsis genome; however, several AtTPS genes are clustered and organized in tandem repeats. Furthermore, some AtTPS genes are localized with prenyltransferase genes ( AtGGPPS, geranylgeranyl diphosphate synthase) in contiguous genomic clusters encoding consecutive steps in terpenoid biosynthesis. The clustered organization may have implications for TPS gene evolution and the evolution of pathway segments for the synthesis of terpenoid natural products. Phylogenetic analyses highlight events in the divergence of the TPS paralogs and suggest orthologous genes and a model for the evolution of the TPS gene family.

Alkyl and Aryl Transferases↗
PubMed2006

Assessing computational amino acid beta-turn propensities with a phage-displayed combinatorial library and directed evolution.

Structure propensities of amino acids are important determinants in guiding proteins' local and global structure formation. We constructed a phage display library--a hexa-HIS tag upstream of a CXXC (X stands for any of the 20 natural amino acids) motif appending N-terminal to the minor capsid protein pIII of M13KE filamentous phage--and developed a novel directed-evolution procedure to select for amino acid sequences forming increasingly stable beta-turns in the disulfide-bridged CXXC motif. The sequences that emerged from the directed-evolution cycles were in good agreement with type II beta-turn propensities derived from surveys of known protein structures, in particular, Pro-Gly forming a type II beta-turn. The agreement strongly supported the notion that beta-turn formation plays an active role in initiating local structure folding in proteins.

Amino Acid Sequence↗
PubMed2004

Cancer in U.S. ethnic and racial minority populations.

Discoveries, breakthroughs, and advances made in the area of cancer prevention and cancer control over the last 2 decades have led to declines in the rates of cancer incidence and mortality and increases in life expectancy and survival for many cancer patients. However, although the trends relative to cancer incidence, mortality, and 5-year survival for the nation as a whole have significantly improved, data reveal that there are significant disparities in the degree to which the burden of cancer that remains is borne by racial and ethnic minority population groups. As a practice-oriented discipline grounded in research, nursing could have a dominant role in efforts aimed toward eliminating the cancer disparities experienced by racial and ethnic population groups. Several reports of nursing studies have been published in the peer-reviewed literature that address factors associated with the cancer disparities experienced between and among U.S. racial and ethnic minority groups. However, given that few efforts have been undertaken to comprehensively review and critique this body of research, little is known about the scope, quality, and potential impact of this body of nursing science. This report presents the results of one of the first comprehensive reviews of nursing research undertaken to explore and address factors associated with the evolution of the cancer-related health disparities in ethnic and racial minority population groups within the United States. The findings reveal that, while the body of nursing research has contributed much to the identification and understanding of factors associated with the excess cancer morbidity and mortality of minority populations, in order for the profession to more fully contribute to the elimination of cancer-related disparities, there is a need for nurses to further expand and strengthen this base of knowledge.

Attitude to Health↗
PubMed1993

Dynamics of genome change in the E2/NS1 region of hepatitis C virus in vivo.

To substantiate and extend the quasispecies model of hepatitis C virus (HCV), we made a pairwise comparison in the nucleotide and deduced amino acid sequences for multiple recombinant clones of the E2/NS1 region, which derived from each blood sample taken from five patients of subtype II or subtype III infection at different stages. Sequence heterogeneity among the clones was generally high. The heterogeneity, however, changed temporally and appeared to be significantly lowered after interferon therapy. The temporal fluctuation involved selection of particular amino acids at particular positions, which had represented only a minor fraction or had been absent in the previous clones. Evolution of defective viruses was featured by most of the cases, the proportion of which also fluctuated temporally and was extremely high at a certain stage in one of the patients. A comparison was also made among the clones from different stages of each patient and revealed highly divergent clones. An extreme case of subtype III infection showed sequence differences well beyond those among chronologically and geographically different isolates of subtype I or subtype II, which were defined by the same calculation of available sequence data. These features of HCV genome suggest that the virus could circulate as an extremely heterogeneous population including defective viruses and that this heterogeneity lends itself to selection pressures including interferon therapy and host immune response. Our results also indicate an absolute need of population based approach in HCV genetics.

Aged↗