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PubMedDate not supplied

[The direction and motivation for an evolution in methods of antiulcer surgery].

A 23-year retroactive analysis of a heterogeneous series of observations with unfavourable tardy results after antiulcer surgeries showed that the most failures requiring a second surgery appear after large resections with gastrojejunal or gastroduodenal anastomosis and after vagotomies associated with gastric drainage. The most favourable tardy results followed the vagotomy associated with limited gastric resection (hemigastrectomy). This kind of intervention prevents the appearance of the ulcerous relapses and lowers significantly the incidence of the other type of post-surgical iatrogenic complications. The optimal protection against the ulcerous relapse given by vagotomy associated with hemigastrectomy permits a tactical adaptation of the intervention to the lesional and physiopathological characteristics of each case.

Anastomosis, Surgical↗
PubMed1984

Effects of 2,4-dinitrophenol and other metabolic inhibitors on the thermograms of Ehrlich ascites carcinoma cells registered with a microcalorimeter.

The heat produced by Ehrlich ascites carcinoma cells was measured microcalorimetrically to investigate the characteristics of the energetics of these cells. 2,4-Dinitrophenol and other inhibitors were used to obtain the standard thermograms. The heat level of starved Ehrlich ascites carcinoma cells (endogenous) was almost constant and linear and depended on the cell number used in the experiments (about 1 cal/1 X 10(8) cells/hr). The endogenous heat generation was suppressed strongly by potassium cyanide but not by iodoacetic acid or 2,4-dinitrophenol. On the other hand, heat evolution was directly related to the amount of glucose added to the medium but not to the number of cells (19 cal/mmol of glucose). The addition of iodoacetic acid markedly suppressed heat generation, but potassium cyanide did not. In contrast, glucose with dinitrophenol increased heat production markedly to about 10% higher than that of the control, possibly due to the uncoupled energy from oxidative phosphorylation. Malonic acid (1 mM) suppressed slightly the endogenous heat but caused a 15% reduction in exogenous heat. The amount of heat produced by the addition of glucose (19 cal/mmol) was equivalent to 40% of the theoretical value of energy released through glycolysis (47 cal/mmol). Thus, the heat produced by exogenous glucose appears to be mainly dependent on glycolysis.

2,4-Dinitrophenol↗
PubMed1980

Ureteric hemorrhage in hemophilia with rapid healing.

A rapidly regressing ureteric hemorrhage, probably intramural, in a 14-year-old hemophiliac, is demonstrated by two closely sequential intravenous urograms. In the presence of hematuria, the intravenous urogrom outlines both the complications of hemophilia and their evolution, often directing therapy, and identifies concurrent disease.

Adolescent↗
PubMed1987

Directional fixation of mutations in vertebrate evolution.

We have made pairwise comparisons between the coding sequences of 21 genes from cold-blooded vertebrates and 41 homologous sequences from warm-blooded vertebrates. In the case of 12 genes, GC levels were higher, especially in third codon positions, in warm-blooded vertebrates compared to cold-blooded vertebrates. Six genes showed no remarkable difference in GC level and three showed a lower level. In the first case, higher GC levels appear to be due to a directional fixation of mutations, presumably under the influence of body temperature (see Bernardi and Bernardi 1986b). These GC-richer genes of warm-blooded vertebrates were located, in all cases studied, in isochores higher in GC than those comprising the homologous genes of cold-blooded vertebrates. In the third case, increases appear to be due to a limited formation of GC-rich isochores which took place in some cold-blooded vertebrates after the divergence of warm-blooded vertebrates. The directional changes in the GC content of coding sequences and the evolutionary conservation of both increased and unchanged GC levels are in keeping with the existence of compositional constraints on the genome.

Animals↗
PubMed1981

Turnover of mouse intestinal brush border membrane proteins and enzymes in organ culture. A direct evaluation from studies on the evolution of enzyme activities during the culture.

The turnover of mouse intestinal brush border membrane enzymes has been studied by kinetic analysis of the evolution of enzyme activities during organ culture. By comparing the results obtained in these studies with the predictions from a mathematical model of enzyme synthesis and degradation in organ cultures, it has been possible to reach the following conclusions: (1) There is no degradation of brush border membrane enzymes during culture and the rate of synthesis of each enzyme is directly measurable from the kinetics of total enzyme accumulation (tissue + media). (2) Brush border membrane enzymes are released in culture media by two complementary processes. The first one involves a differential solubilization of enzymes but its exact nature cannot be exactly stated. The second one involves a microvesiculation of brush border membranes, the importance of which in vivo is seen in the possible conciliation between urinary membrane synthesis and heterogeneous turnover of membrane components.

Alkaline Phosphatase↗
PubMed1990

[Evolution of the locomotor-sensory systems].

Among directing physical factors of evolution of the locomotor-sensory system (LSS) gravitation, photons energy, oscillations of water and air media, ligands play the main role. At the molecular level the LSS elements are formed on the base of synthesizing genes that bring about development of protein molecules of tubulin and specific protonizing proteins in composition of the locomotor apparatus in Procariota flagellas. Tubulin and dinein with ATPh-ase activity are included in the flagella composition of LSS in Eukaryota, actin and miozin--with a high ATPh-ase activity--in composition of LSS myofilaments in ameboid Eukaryota and locomotor musculature in Metazoa. Simultaneously, in Pro- and Eukaryota in the same cell sensory molecules of rhodopsin, mechanoreceptors, chemoreceptors and so on can be synthesized. As a rule they localize in the flagellar membranes. In Metazoa single receptory flagellar cells are differentiated; they realize conservatively some receptive molecules that are already prepared by their ancessors--Eukaryota. The molecules also preserve their localization in the flagellar membranes. In Metazoa two types of locomotion take place according to the function of regulatory genes: initial flagellar and muscular definitive apparatus. Both types of locomotion are directed and regulated by the organs of sense and CNS; they form a strict spatial model of fixated synaptic connections of LSS. For the first time it was discovered in Ctenophora. This model, despite a complicated organization, is conservatively preserved in its general form in all Proto- and Denterostomia.

Animals↗
PubMed1975

A theory of evolution above the species level.

Gradual evolutionary change by natural selection operates so slowly within established species that it cannot account for the major features of evolution. Evolutionary change tends to be concentrated within speciation events. The direction of transpecific evolution is determined by the process of species selection, which is analogous to natural selection but acts upon species within higher taxa rather than upon individuals within populations. Species selection operates on variation provided by the largely random process of speciation and favors species that speciate at high rates or survive for long periods and therefore tend to leave many daughter species. Rates of speciation can be estimated for living taxa by means of the equation for exponential increase, and are clearly higher for mammals than for bivalve mollusks.

Adaptation, Biological↗
PubMedDate not supplied

[Reverse transcriptase and its biological role].

Elements with open-reading translation frames homologous to retroviral RNA-dependent DNA polymerases (reverse transcriptases) were found in eukaryotic cell genomes. Expression of endogenous reverse transcriptases in prokaryotic and eukaryotic cells is confirmed directly and indirectly. Evolution and function of reverse transcriptases are analyzed, and their phylogenetic and ontogenetic role is evaluated.

Biological Evolution↗
PubMed1992

Evolution of major histocompatibility complex class II allelic diversity: direct descent in mice and humans.

The high degree of polymorphism seen at major histocompatibility complex (MHC) class II loci is a feature unique to the MHC. Most of the beta-chain polymorphism is localized in "hypervariable" regions (HVRs). HVR amino acid sequence similarity between distantly related species has recently been found. We have employed a Monte-Carlo statistic to show that shared HVR polymorphism between beta-chain genes of humans and mice represents direct descent of ancestral sequences rather than convergent evolution. Furthermore, half the sequence polymorphism seen in class II beta-chain genes of mice persists in evolution and is encoded by the same DNA sequence in humans. No evidence for increased mutation rate within the HVR was found. We postulate that the HVR can be considered the genetic unit of recombination, with selection for HVR sequences and combinations of HVRs constrained by functional considerations.

Alleles↗
PubMed2026

Dissecting contributions of directional and balancing selection to trajectories of mitochondrial haplotype evolution in Drosophila melanogaster.

Emerging evidence suggests mtDNA haplotypes contribute to fitness variation and local adaptation, with directional thermal selection and negative frequency-dependent selection shaping haplotype diversity. However, their interplay remains unexplored. We conducted experimental evolution using Drosophila melanogaster populations from opposite ends of an Australian latitudinal cline (Melbourne and Townsville), exposing them to contrasting temperatures (17°C versus 27°C) and varying starting frequencies of two mtDNA haplotypes (A1 and B1) that occur at appreciable frequencies in these populations. We paired this with population genetic simulations to estimate selection and its influence on haplotype trajectories. Haplotype frequencies were influenced by interactions involving temperature, starting frequency, and nuclear genomic background (Melbourne, Townsville, or admixed). Although prior work predicted A1 should be favoured at the warmer temperature and B1 at the cooler temperature, A1 was generally favoured across both temperatures. Simulations supported directional selection in populations evolving at 17°C in the Melbourne background; otherwise dynamics were best explained by balancing selection shaped by negative frequency-dependent fitness effects. Patterns also varied across nuclear backgrounds, suggestive of mito-nuclear epistasis. These findings challenge a simple thermal adaptation model of mtDNA dynamics, suggesting that mtDNA evolution is shaped by interacting effects of temperature, frequency-dependence, nuclear background and experimental environment.

adaptation↗
PubMed1976

Controlling protein evolution.

A method is presented for selecting, with a high degree of specificity, mutants for the enzyme alcohol dehydrogenase (ADH) of Saccharomyces cerevisiae having altered kinetics. The method depends on the facts that a) petite yeast strains (those unable to respire aerobically) have an absolute dependence on the presence of cytoplasmic alcohol dehydrogenase, and b) allyl alcohol is readily oxidized by yeast ADH to the highly poisonous product acrolein. If petite yeast are grown in the presence of allyl alcohol surviving mutants show alterations that can be traced to the ADH structural gene. Eight out of nine spontaneous mutant enzymes and five out of five mutants enzymes induced by nitrosoguanidine exhibited a slower electrophoresis mobility than wild type. There may therefore be some correlation between electrophoretic mobility and function. Of three mutant enzymes purified, one of spontaneous origin and two induced by nitrosoguanidine, each showed a different pattern of altered kinetics and a different specific activity. This strongly suggests that, despite the considerable specificity of the selective procedure, there are many ways in which an enzyme can be altered in response to an environmental stimulus. The implications of these results for the study of protein evolution and some directions for future research are briefly discussed.

Alcohol Oxidoreductases↗