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An experimental model of human african trypanosomiasis is realized in sheep with Trypanosoma brucei brucei. Clinical and biological evolution is comparable to human disease. This model is useful to test efficient drugs and to get a better knowledge about sleeping sickness physiopathology.
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Alkaline phosphatase activity allows a certain discrimination between lympho-inhibition following a direct action on the lymphoid stem cells or a modification of mesenchyme/epithelium interactions; in this study we have compared the evolution of this activity in untreated chick embryos and in chick embryos following graft-versus-host-reactions. The important decrease of mesenchyme alkaline phosphatase activity induced here, involves a localisation of allograft reaction in this tissue; this result does not agree with the former explanations about a direct action on the lymphoid stem cells.
By comparing the evolution of chrysotile and amosite fibres in rat lungs, more rapid clearance was found in the case of chrysotile. The rate of chrysotile clearance is strongly influenced by the size factor. The two varieties of asbestos also differ in their chemical behaviour in the lung. The evolution of chrysotile fibers in vivo is characterized by progressive decrease in magnesium content, while silicium retained in the fibre skeleton is practically not eliminated. Transport of fibers from the lungs to the lymph-nodes, the parietal pleura and the diaphragm also differs with the two asbestos varieties. From fibre counts with the electron microscope, chrysotile was more rapidly eliminated from the lungs than amosite. The concentration is higher with amosite in the lymph-nodes, and with chrysotile in the diaphragm. This last result confirms observations made on human lungs.
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The injection in vivo of red alizarin S. in young mice during the post-natal period, enabled to show the mechanisms that were modeling the mandible during its development (by apposition-resorption). So it was possible to study : the processes of ossification involved in the eruption of the teeth, the modifications of the bony relief and the alterations of the mandibular angle. It has been attempted to find the links between these phenomena and muscular excitation, function and behaviour. The study of the osseous - muscular - mandibular anatomical set provided a good example of the principle described in Evolutionary morphology: "The comparatively free evolution of the elements in the anatomical set that they constitute (Sakka, 1973)."
The authors compared the evolution of the pregnancy, of the labour and of the post-partum period in 75 patients who had cerclage for cervico-isthmial incompetence and in 68 mothers who had no pathology in the cervix (the control group). A state of infection developed more often in the mother and in the fetus and/or the newborn in the group that had cerclage than in the control group. The perinatal death of 7 infants in the group that had cerclage, of which 5 were due to infection, is to be deplored. The only perinatal death in the control group was due to an infection.
Eighteen patients received CP substituting AZ after renal transplantation following evidence of hepatitis. We have compared graft evolution before and after treatment with CP. Twelve patients showed no modification in graft evolution. In four patients the renal function decreased but it did not seem attributable to the change of the drug. Two patients showed intolerance attributable to the change of the drug. In one patient who received CP instead of AZ since the data of the transplant onwards, with no evidence of hepatic lesion, renal function decreased but this did not seem attributable to the use of the drug. The dose of CP in renal transplantation is discussed. We conclude that CP is a good substitute for AZ in renal transplanted patients. Adequate doses seemed to range between 0.7 and 1 mg/kg/day.
A pilot project for the prevention of substance abuse in schools (PASE) has been developed in 1988-90 in sixth and seventh grades (12-14 years-old) in 11 primary schools in the city of Barcelona (Spain). Data on consumption smoking, alcohol and drugs were obtained before the implementation of the project, shortly afterwards, and in the next school year. These results are presented, comparing the evolution of attitudes, beliefs and behavior of these school children with a control group composed of students from reference schools. The results suggest a modest but significant effect of the program, which seems to decrease over time for smoking, suggesting the need for booster interventions to maintain its effects.
As a part of a larger, multidimensional study on secretory otitis media (SOM) and its relation to children's development, the effects of ventilation tube (VT) placement on hearing, speech, language, cognition and behaviour were studied over a six month period. Children with a clear and persistent picture of SOM were examined just before tubes were inserted and again, with the same measures, six months later. Their evolution was compared to that of a control group. The results indicate, as was expected, that the hearing of the children with SOM normalized very quickly after surgery. Speech and expressive language functions were comparable for both groups at the two moments of examination. Only verbal comprehension of the SOM-group was found to be slightly improved in the course of a six month period. No differences in general cognitive functioning and in behaviour were found between both groups.
The potential of comparative studies on histones for use in protistan evolution is discussed, using algal histones as specific examples. A basic premise for the importance of histones in protistan evolution is the observation that these proteins are completely absent in prokaryotes (and cytoplasmic organelles), but with few exceptions, the same five major histone types are found in all higher plants and animals. Since the histone content of the algae and other protists is not constant, some of these organisms may represent transition forms between the prokaryotic and eukaryotic modes of packaging the genetic material. Comparative studies of protistan histones may thus be of help in determining evolutionary relationships. However, several problems are encounter with protistan histones, including difficulties in isolating nuclei, proteolytic degradation, anomalous gel migration of histones, and difficulties in histone identification. Because of the above problems, and the observed variability in protistan histones, it is suggested that several criteria be employed for histone identification in protists.
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Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
The maintenance of a proper distribution of charged amino acid residues might be expected to be an important factor in protein evolution. We therefore compared the inferred changes in charge during the evolution of 43 protein families with the changes expected on the basis of random base substitutions. It was found that certain proteins, like the eye lens crystallins and most histones, display an extreme avoidance of changes in charge. Other proteins, like phospholipase A2 and ferredoxin, apparently have sustained more charged replacements than expected, suggesting a positive selection for changes in charge. Depending on function and structure of a protein, charged residues apparently can be important targets for selective forces in protein evolution. It appears that actual biased codon usage tends to decrease the proportion of charged amino acid replacements. The influence of nonrandomness of mutations is more equivocal. Genes that use the mitochondrial instead of the universal code lower the probability that charge changes will occur in the encoded proteins.
The concept of nucleic acid sequence base alternations is presented. The number of base alterations for the sequences of different length is established. The definition of "enlarged similarity" of nucleic acids sequences on the basis of sequence base alterations is introduced. Mutual information between sequences is used as a quantitative measure of enlarged similarity for two compared sequences. The method of mutual information calculation is developed considering the correlation of bases in compared sequences. The definitions of correlated similarity and evolution similarity between compared sequences are given. Results of the use of enlarged similarity approach for DNA sequences analysis are discussed.
A model for the study of experimental evolution is provided by the novel metabolic system responsible for the progressive utilization of L-1,2-propane-diol by mutants of Escherichia coli (strains 3 and 430). In these mutant strains, propanediol oxidoreductase, which serves as L-lactaldehyde reductase in fucose fermentation by wild-type cells, became a key enzyme for aerobic catabolism of propanediol. In the wild-type strain (strain 1), the enzyme is inducible only anaerobically; in strains 3 and 430, the enzyme is synthesized constitutively even in the presence of air. The propanediol oxidoreductase from all three strains was purified to homogeneity by the same procedure. The enzyme of strain 3 clearly differed from that of strain 1 in several respects: Km and V in both directions of the reaction, energy of activation, thermal stability, pH optimum and substrate specificity. However, no difference in any of the above characteristics was found between the enzymes of strains 3 and 430. All three enzymes presented the same electrophoretic mobility. According to immunological data, all three strains differed in their intracellular enzyme level.