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At least 253 records · Page 14Linked to original sources
PubMed1996

Heart rate variability after cardiac transplantation in humans.

The reappearance of cardiac innervation after cardiac transplantation remains a matter of debate. We evaluated the ability of heart rate variability (HRV) analysis to detect the extent and time course of functional cardiac allograft reinnervation. Time- and frequency-domain analysis of heart rate was performed on Holter recordings of 120 heart transplant and four heart-lung transplant recipients. A high frequency (HF) component was clearly distinguished on visual inspection of power spectral density in 42 patients. In eight patients an HF component of normal magnitude was detected. The other 34 patients in this group, including all four heart-lung transplants, presented with a very small HF component. The other 82 patients showed a flat spectrum. The group with an HF component of normal amplitude was significantly different, compared to the other groups, for all HRV parameters. Serial plotting of HRV parameters of the patients with an HF component of normal amplitude against time posttransplant, revealed, from 12 months onwards, a progressive increase of parameters denoting HF variability. In five heart transplant patients with acute allograft rejection, the use of HRV analysis for rejection monitoring was unsuccessful. These results suggest that, inasmuch as the HF component of HRV is caused by parasympathetic cardiac innervation, the HF component of normal amplitude, observed in only a minority of cardiac transplant recipients (6%), is a marker for parasympathetic reinnervation. The evolution over time of this HF component is compatible with a biological phenomenon as gradual parasympathetic reinnervation of the sinus node.

Autonomic Nervous System↗
PubMed1997

Novel metabolites in phenanthrene and pyrene transformation by Aspergillus niger.

Aspergillus niger, isolated from hydrocarbon-contaminated soil, was examined for its potential to degrade phenanthrene and pyrene. Two novel metabolites, 1-methoxyphenanthrene and 1-methoxypyrene, were identified by conventional chemical techniques. Minor metabolites identified were 1- and 2-phenanthrol and 1-pyrenol. No 14CO2 evolution was observed in either [14C]phenanthrene or [14C]pyrene cultures.

Alkaloids↗
PubMed1994

[Isolation and characterization of three rat adult type beta-globin genes].

In order to clarify the molecular basis of the heterogeneity of rat hemoglobins, two DNA clones containing the genes for adult type beta-globins were isolated from a rat genomic DNA library. The results obtained in the present experiments are summarized as follows. 1) Clone lambda Rg beta 59 contained the gene for an adult rat beta-major globin, II beta, while clone lambda Rg beta 45 contained the genes for two adult rat beta-minor globins, III beta, and O beta, respectively. 2) The entire nucleotide sequences of these genes were determined, indicating that the genes are all composed of 3 exons and 2 introns, and code for 146 amino acid residues. The genes exhibited structural features typical to known expressed beta-like globin genes, implying that they are all functional. 3) The predicted amino acid sequences completely agreed with the amino acid sequences of II beta, III beta and O beta globins, respectively, which we isolated in a separate experiment. 4) Sequence comparisons of three rat globin genes with one another and with the known mouse beta-major and beta-minor globin genes showed the occurrence of interesting homologies between two species from evolutional aspects. 5) Southern hybridization analysis of the genomic DNA implies that a number of beta-like globin genes other than the present ones exist in the rat genome.

Amino Acid Sequence↗
PubMed1990

[Combined treatment of gaseous gangrene with hyperbaric oxygen therapy, surgery and antibiotics. A national cooperative multicenter study].

85 confirmed gas gangrene cases from general hospitals where hyperbaric oxygen chambers with single or multiple places are available were reviewed. The diagnosis was made on the basic of muscle necrosis with the characteristic color and odor of the wound, and suggestive clinical and bacteriological findings. The treatment consisted on surgical excision, multiple antibiotic therapy, and hyperbaric oxygen at 3 absolute atmospheres. There was a male predominance (76.5%); 49.4% of them had previous risk factors; the origin of the disease was spontaneous in 18.8% of cases, after trauma in 37.6%, and after surgery in 43.5%. The surgery had been orthopedic in 18.8%, vascular in 16.5% and other in 1.2%. The lesion was in the lower limbs in 71.8%, with abdominal origin of propagation in 18.8% and perineal propagation in 8.2%. 44.7% of patients had shock on admission. The outcome was good in 50.6% of patients, who had a full recovery, and fair in 16.5%, who had minor sequelae or small re-amputations; this amounts to 67.1% of satisfactory evolutions. Outcome was poor in 20% in whom amputation or other major surgical procedures were required (p less than 0.05). Overall mortality rate was 20%, although only in 12.9% death directly related with gas gangrene. Mortality was significantly higher in women, in abdominal localization, and in patients with shock. It was 37.5% in spontaneous and 29.7% in postsurgical cases. There was no death in traumatic cases (p less than 0.005). Death directly related with the disease occurred in the first three days and nonrelated death after two weeks. More severe cases could be cared for in hospitals where multiple place hyperbaric oxygen chambers were available than in those with single place chambers, with a definite outcome towards cure or death with less intermediate situations. The relevant literature is reviewed. It is concluded that this combined therapeutic schedule has the best efficacy to treat gas gangrene, particularly in the more severe forms.

Adolescent↗
PubMed1996

Random important alterations in HIV-1 viral quasispecies after antiviral treatment.

The evolution of HIV-1 viral populations was studied in a set of MT-2-co-cultured viruses isolated from five patients at the beginning of treatment with zidovudine and after 11-36 months of drug therapy. We first characterized the HIV-1 pol gene to detect the zidovudine-resistance mutations at codons 215 and 219. To analyse the effect that the selective pressure of zidovudine on pol exerted on other genomic regions, we also studied the env gene. The env gene sequence of virus isolated from one individual was unchanged, whereas three other sample pairs had minor alterations in env. In one individual, we detected a significant change in the env gene sequence, and so performed a clonal analysis on viruses isolated before and after treatment. In this individual, the zidovudine-resistant variant that became predominant in the resistant virus population was an undetected minority variant of the viral population before treatment was initiated. These results indicate that the evolution of quasispecies produced by selective pressure on the pol gene from zidovudine treatment could select, in a random process, important changes in other genomic regions; in particular, we describe alterations in the env gene.

Anti-HIV Agents↗
PubMed2003

On the relative roles of faster-X evolution and dominance in the establishment of intrinsic postzygotic isolating barriers.

The modern theory of speciation assigns a prominent role to the recessivity of genetic incompatibilities in the two rules of speciation, namely Haldane's rule and the 'large X effect', and considers that the contribution of faster evolution of the X versus the autosomes to those patterns is generally of relatively minor importance. By extending Turelli and Orr's previous analysis of the model of two-locus Dobzhansky-Muller incompatibilities, I first show that when the X and the autosomes evolve at the same rate, the two dominance parameters involved in that model are not equally important for the declaration of a large X effect, but that the degree of recessivity of homozygous-homozygous incompatibilities is the major determinant for such a declaration. When the X evolves faster than the autosomes, the model obviously predicts that the importance of both dominance parameters will progressively vanish. It is then of importance to obtain estimates of the relative evolutionary rate of X-linked incompatibility loci. Several different procedures to obtain such estimates from the perspective of the large X effect are suggested. The application of the appropriate test to the only suitable data from Drosophila hybridizations so far available leads to the conclusion that the X actually evolves at least 2.5 times faster than the autosomes, as far as hybrid male sterility determinants are concerned, thus making dominance considerations absolutely irrelevant. Notwithstanding the necessity of further tests, the relative roles currently assigned to faster-X evolution and dominance in the theory of speciation should be revised, giving due prominence to faster-X evolution, at least for hybrid male sterility in the genus Drosophila.

Animals↗
PubMed1995

[Regulatory selection as an alternative to the neutrality theory].

Regulatory selection is the most typical mode of natural selection responsible for the optimization of the regulatory systems of an organism. In addition to regulatory selection, stringent selection of pleiotropic mutants or recombinant forms with altered ecological potential operates in successful species during vertical evolution. Regulatory selection stabilizes alterations in the ecological potential, acting at intervals between larger regulatory genome alterations occurring at the boundaries between evolutionary phases. Fisher's adaptive model can be applied to regulatory selection. At each separate evolutionary phase, the selection coefficients in selected mutants decline gradually. At the final stage of the evolutionary phase, mutations with a minor selective advantage are selected. Hence, regulatory selection may be regarded as an alternative to the neutral evolution theory.

Animals↗
PubMed1997

[Analysis of intensity of post-stroke depression and its relationship with the cerebral lesion location].

BACKGROUND: Several studies have suggested a close relationship between intensity of poststroke depression and lesion location, but the relationships are not clear for some authors. In this study we try to test the hypothesis that the intensity of depression in an early stage (4th week) of cerebral vascular accidents (CVA) in related to lesion location and type of lesion. PATIENTS AND METHODS: In a sample of one hundred and thirty patients in the fourth week of the evolution of an unilateral CVA, 48 patients fulfilled research diagnostic criteria (RDC) of post-stroke depression (34 major depression; 14 minor depression). Schedule for Affective Disorders and Schizophrenia (SADS) and standard measures of intensity of depression (Hamilton's HRDS, Montgomery-Asberg's MADRS and Beck's BDI) were used. RESULTS: In the fourth week of the evolution of CVA's, depression intensity measures (HRDS and BDI) were significantly higher in anterior lesion when compared to posterior lesions. No significant differences were found between right and left lesions, but both were higher than in non-hemispheric lesions. No significant differences of prevalence or intensity of depression were found in relation to lesion type (hemorrhagic/ischaemic). CONCLUSION: The results confirm a relationship between intensity mood disorders after a cerebral vascular accident and the topography of the lesion.

Aged↗
PubMed1995

The electrolytical processes in dirty ices: implications for origin and chemistry of minor bodies and related objects.

Many moonlike bodies (M approximately or = 1 Moon) beyond the Martian orbit contain large amounts of dirty ice (approximately 50%) forming thick mantle with the solid phase thermal convection. When a body moves through the inter- or nearplanetary magnetized plasma, electric current is generated in the body and its environment. The current passing through a dirty ice containing up to 10% of organic admixtures produces a lot of electrochemical effects which have a profound impact on its composition. At this stage one can hardly say something definite concerning changes experienced by organics. The changes must occur inevitably and can be of a rather unexpected and far-reaching nature, so deserving a close study. Another obvious effect is a volumetric electrolysis of ice containing alien inclusions. The electrolysis products accumulate in ice in the form of a solid solution which is capable of detonation at 15-20 wt.% of 2H2 + O2. If M > or = 1 Moon (Galilean satellites, Titan), the body loses in explosion a part of its mass in the form of vapor and ice fragments (=short-period comet nuclei), whereas if M < or = 0.2 Moon, the body breaks up totally (the Main Belt asteroids origin approximately 3.9 Byr ago). 2H2 + O2 containing cometary nuclei are capable of burning or suffer new explosions when receiving an additional energy. The combustion in the sublimation products containing also light organics and 2H2 + O2 explains unexpected energetics and nearnuclear chemistry of Comet P/Halley (e.g. great abundances of negative and positive ions, atomic carbon, CO over CO2, origin of CHON particles etc) and its distant outbursts correlated, possibly, with the Solar activity. Thus the electrochemical processes in the dirty ice with organics, along with its subsequent thermal, radiative etc. processing, open up new potentials for explanation and prediction of quite unexpected discoveries.

Electric Conductivity↗
PubMed1975

Effect of vacuum infiltration on photosynthetic gas exchange in leaf tissue.

Using a manometric method, photosynthetic oxygen evolution and (14)CO(2) fixation have been determined for leaf tissue of Triticum aestivum L., Hordeum vulgare L., Phaseolus vulgaris L., and Lemna minor L. Approximately similar values in the range 0.2 to 0.4 millimoles grams fresh weight(-1) hour(-1) were obtained for both gases. In tissue subjected to vacuum infiltration, O(2) evolution and (14)CO(2) fixation were barely measurable. It is considered that the elimination of photosynthetic gas exchange results from a decreased supply of CO(2) to the chloroplasts. Chopping wheat laminae also leads to a reduction in photosynthetic gas exchange, slices 1 millimeter or less giving only 10 to 20% of the value for whole tissue. Respiration is unaffected by either treatment. Carbonic anhydrase did not improve photosynthetic gas exchange in infiltrated tissue. The use of sliced or vacuum-infiltrated leaf tissue in photosynthetic studies is discussed.

Journal Article↗
PubMed1996

A network of specific minor-groove contacts is a common characteristic of paired-domain-DNA interactions.

Pax proteins are a family of transcription factors conserved during evolution and able to bind specific DNA sequences through a domain called a "paired domain'. The DNA-binding specificity of the Pax-8 paired domain was investigated. Site-selection experiments indicate that Pax-8 binds to a consensus sequence similar to those bound by Pax-2 and Pax-5. When consensus sequences of various paired domains are observed in light of recent structural studies describing paired-domain-DNA interaction [Xu, Rould, Jun, Desplan and Pabo (1995) Cell 80, 639-650], it appears that base-pairs contacted in the minor groove are conserved, while most of the base-pairs contacted in the major groove are not. Therefore a network of specific minor groove contacts is a common characteristic of paired-domain-DNA interactions. The functional importance of such a network was successfully tested by analysing the effect of consensus-based mutations on the Pax-8 binding site of the thyroglobulin promoter.

Animals↗
PubMed2003

Palaeoclimatic changes explain Anatolian mountain frog evolution: a test for alternating vicariance and dispersal events.

Holarctic biodiversity has been influenced by climatic fluctuations since the Pliocene. Asia Minor was one of the major corridors for postglacial invasions in the Palearctic. Today this area is characterized by an extraordinarily rich fauna with close affiliation to European, Asian and Indo-African biota. However, exact scenarios of range expansion and contraction are lacking. Using a phylogeographical approach we (i). identify monophyletic lineages among Anatolian mountain frogs and (ii). derive a spatio-temporal hypothesis for the invasion process in Anatolia. We sequenced 540 bp of the mitochondrial 16S rRNA gene from 40 populations of mountain frogs from Anatolia, the Elburz Mountains and the Caucasus. Our samples comprise all known species and subspecies: Rana macrocnemis macrocnemis, R. m. tavasensis, R. m. pseudodalmatina, R. camerani and R. holtzi. They include the type localities of four of these taxa. We used a nested clade analysis (NCA) to infer historical and recurrent events that account for the observed geographical distribution of haplotypes. None of the extant species is monophyletic. Based on a molecular clock calibration using homologous sequences of Western Palearctic water frogs of the same genus, we estimated that a basic radiation into three lineages c. 2 Mya was followed by several dispersal and fragmentation events. The geographical distribution of resident and widespread haplotypes allows us to infer and date scenarios of range expansion and fragmentation that are aligned with dramatic climatic oscillations that have occurred during the last 600000 years. Consequently, Pliocene and Pleistocene climatic oscillations triggered the evolution of Anatolian mountain frogs through an interplay of vicariance and dispersal events.

Animals↗
PubMed1998

Characterization of genes encoding translation initiation factor eIF-2gamma in mouse and human: sex chromosome localization, escape from X-inactivation and evolution.

The Delta Sxrb interval of the mouse Y chromosome is critical for spermatogenesis and expression of the male-specific minor transplantation antigen H-Y. Several genes have been mapped to this interval and each has a homologue on the X chromosome. Four, Zfy1 , Zfy2 , Ube1y and Dffry , are expressed specifically in the testis and their X homologues are not transcribed from the inactive X chromosome. A further two, Smcy and Uty , are ubiquitously expressed and their X homologues escape X-inactivation. Here we report the identification of another gene from this region of the mouse Y chromosome. It encodes the highly conserved eukaryotic translation initiation factor eIF-2gamma. In the mouse this gene is ubiquitously expressed, has an X chromosome homologue which maps close to Dmd and escapes X-inactivation. The coding regions of the X and Y genes show 86% nucleotide identity and encode putative products with 98% amino acid identity. In humans, the eIF-2gamma structural gene is located on the X chromosome at Xp21 and this also escapes X-inactivation. However, there is no evidence of a Y copy of this gene in humans. We have identified autosomal retroposons of eIF-2gamma in both humans and mice and an additional retroposon on the X chromosome in some mouse strains. Ark blot analysis of eutherian and metatherian genomic DNA indicates that X-Y homologues are present in all species tested except simian primates and kangaroo and that retroposons are common to a wide range of mammals. These results shed light on the evolution of X-Y homologous genes.

Amino Acid Sequence↗
PubMed1994

Primary care by desire or default? Specialty choices of minority graduates of US medical schools in 1983.

This study was undertaken to determine if US medical school students of different racial/ethnic backgrounds demonstrate similar patterns of evolution of specialty choice between their senior year of medical school and their third postgraduate year. The study identified the specialty choices of US medical school seniors in 1983 through their responses to the Association of American Medical Colleges Graduating Medical Student Questionnaire (GQ). The cohort was classified into three groups: underrepresented minorities, non-underrepresented minorities, and whites. Using these AAMC data as baseline, each racial/ethnic background group was tracked through their third residency year. Comparisons were made between anticipated specialty choices as senior medical students and actual specialties as revealed through residency tracking. The study found that more than 95% of the cohort began residencies in specialties compatible with their GQ choices. Unexpectedly, almost 20% of blacks, Commonwealth Puerto Ricans, and other Hispanics were not in graduate medical education in their third postgraduate year. This group needs to be studied further in order to learn the proportion of these physicians who subsequently completed residency training and the reason(s) for attrition in physicians who did not fulfill minimum training requirements for board certification.

Black or African American↗
PubMed1993

What can meteorites tell us about nebular conditions and processes during planetesimal accretion?

Analysis of the most primitive meteorites can yield detailed information about environmental conditions and physical/chemical processes in the earliest Solar System, including the nebular stage during which planetesimals were accreted. Such information pertains to time scales, thermal and chemical evolution, inhomogeneity and mixing, magnetic fields, and grain growth in the solar nebula. Nebular processes identified include evaporation, condensation, localized melting, and fractionation both of solids from gas and among different solids. Little direct evidence remains even in primitive meteorites of the actual accretion process. The absence of intrinsic factors capable of enhancing accretion among meteoritic constituents suggests that gravitational instabilities might have been important in promoting planetesimal accretion.

Chemical Phenomena↗
PubMed1996

The delivery of organic matter from asteroids and comets to the early surface of Mars.

Carbon delivered to the Earth by interplanetary dust particles may have been an important source of pre-biotic organic matter (Anders, 1989). Interplanetary dust is shown to deliver an order-of-magnitude higher surface concentration of carbon onto Mars than onto Earth, suggesting interplanetary dust may be an important source of carbon on Mars as well.

Carbon↗