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At least 289 records · Page 16Linked to original sources
PubMed2004

Cancer cryotherapy: evolution and biology.

Since the inception of cryosurgery in the 1850s, landmark advances in chemistry, physics, materials science, and biology have culminated in the sophisticated cryosurgical devices currently in use. Effective cryosurgical tissue injury depends on four criteria: 1) excellent monitoring of the process; 2) fast cooling to a lethal temperature; 3) slow thawing; and 4) repetition of the freeze-thaw cycle. Meeting these criteria depends on understanding the imaging technology used to visualize the iceball, the type of cryogen used, the size of the probe, and probe arrangement. Third-generation cryosurgical equipment offers advantages over previous designs. These machines rely on argon for freezing but also use helium to warm probes and accelerate the treatment process, and they offer additional safety by being able to rapidly arrest iceball formation. Metallurgic advances have led to the development of thinner probes, which have been easily adapted to perineal templates similar to those used for prostate brachytherapy.

Journal Article↗
PubMedDate not supplied

[Hairy cell leukemia. I.--Clinical, biological and evolutive study on twenty-eight cases (author's transl)].

A clinical and laboratory evaluation of 28 patients with hairy cells leukemia is performed. Twenty-two had splenomegaly and all but one had a pancytopenia with 5 to 70% of hairy cells in blood. A tartrate-resistant acid phosphatase activity was positive in the hairy cells of 11 patients of 14 studied. In all patients a myelofibrosis and a leukemic infiltration were found in a bone-marrow biopsy of iliac crest. Hemodilution by splenomegaly, mild hemolysis and dyshematopoiesis were observed in 10 patients by a 51Cr or 59Fe isotopic exploration. In seven cases an immunological study of the hairy cells was performed, a high percentage of the leukemic cells of these 7 patients had polyclonal surface Ig but without resynthesis of monoclonal S Ig which is a feature usually associated with B lymphocytes. In the blood of these patients normal T and B lymphocytes were decreased. A splenectomy was done in 12 patients (43%) always for severe pancytopenia Splenectomy was not randomised. Spleen weights ranged from 1 085 to 3 600 g. In splenectomised patients the level of hemoglobin, segmented cells and thrombocytes was significantly higher after surgery. The survival rate is better in the splenectomised group (median survival 57 months) than in the non-splenectomised group (median survival 19 months). Infectious diseases were frequent in all patients but less after splenectomy. Fourteen patients died, 8 owing to pancytopenia.

Adult↗
PubMed2006

[Uncontrolled genetic processes in artificial populations: proving the leading role of selection in evolution].

The review considers studies examining artificially maintained populations as models for understanding biological evolution. The key factors of gene pool evolution-random processes, interspecific hybridization, migration, mutation, and selection--are analyzed. We present evidence indicating that selection is the leading evolutionary factor that regulates the operation of other factors, directly or through genetic systems.

Animals↗
PubMed1980

Experiments in microbial evolution: new enzymes, new metabolic activities.

Biological evolution has resulted in a richness and diversity of species. Among microorganisms this is most evident in the wealth and diversity of biochemical transformations. Evidence for evolutionary relationships may be obtained from comparative studies, but with microorganisms it is also possible to follow evolution in action. Microbial populations adapt rapidly to changes in the environment and the evolution of new metabolic activities can be observed in laboratory experiments. The enzymes of many catabolic pathways are synthesized in response to the presence of inducing substrates. New catabolic activities may be acquired by mutations in regulatory genes resulting in alterations in the specificity of induction, or in enzyme synthesis in the absence of inducer. Mutations in structural genes may given rise to enzymes with altered substrate specificities. In bacteria, catabolic genes may be carried on plasmids and the exchange of plasmids among bacterial populations increases the evolutionary potential. Experiments in microbial evolution have produced strains with novel catabolic activities involving regulatory or structural gene mutations, gene duplications and plasmid exchange. Enzymes studied in this way include amidase, ribitol dehydrogenase, evolved beta-galactosidase, and enzymes of the catabolic pathways for pentoses and pentitols and haloaromatic compounds.

Amidohydrolases↗
PubMed1999

Phylogeny and evolution of chemical communication: an endocrine approach.

The present review assesses the phylogenetic history of information molecules (bioregulators pheromones, hormones, neuroactive compounds), receptors, transducers, second messengers) in uni- and multicellular organisms. Transitional stages between contemporary endocrine secretions including hormones and neuroactive materials, and primogenial exocrine compounds (pheromones) are proposed. Severalhypotheses have been developed to explain the origin and evolution of bioregulator/receptor units. Finally, how these primordial information molecules have either been co-opted or have changed their function during the course of biological evolution is analysed.

Amino Acid Sequence↗
PubMedDate not supplied

[Methodological problems of the relation of thermodynamics and biology].

Methodological problems are considered on the relation of thermodynamic principles in systems far from being equilibrium and processes of biological evolution. Attention is paid that these problems are sometimes erroneously interpreted from the standpoint of reducing biology to physics and chemistry. The analysis of the theories under study shows that they reveal concretely the dialectics of biology reducibility and irreducibility to physics and chemistry. A conclusion is made that the notion of "submission of lower forms of the matter to higher ones" which is insufficiently studied in dialectics may be revealed by means of notions of lower forms regulation and control by higher ones.

Animals↗
PubMed1986

Interaction, functional relations and evolution of large and small subunits in Rubisco from prokaryota and eukaryota.

In early biological evolution anoxygenic photosynthetic bacteria may have been established through the acquisition of ribulose bisphosphate carboxylase-oxygenase (Rubisco). The establishment of cyanobacteria may have followed and led to the production of atmospheric oxygen. It has been postulated that a unicellular cyanobacterium evolved to cyanelles which were evolutionary precursors of chloroplasts of both green and non-green algae. The latter probably diverged from ancestors of green algae as evidenced by the occurrence of large (L) and small (S) subunit genes for Rubisco in the chloroplast genome of the chromophytic algae Olisthodiscus luteus. In contrast, the gene for the S subunit was integrated into the nucleus in the evolution of green algae and higher plants. The evolutionary advantages of this integration are uncertain because the function of S subunits is unknown. Recently, two forms of Rubisco (L8 and L8S8) of almost equivalent carboxylase and oxygenase activity have been isolated from the photosynthetic bacterium Chromatium vinosum. This observation perpetuates the enigma of S subunit function. Current breakthroughs are imminent, however, in our understanding of the function of catalytic L subunits because of the application of deoxyoligonucleotide-directed mutagenesis. Especially interesting mutated Rubisco molecules may have either enhanced carboxylase activity or higher carboxylase:oxygenase ratios. Tests of expression, however, must await the insertion of modified genes into the nucleus and chloroplasts. Methodology to accomplish chloroplast transformation is as yet unavailable. Recently, we have obtained the first transformation of cyanobacteria by a colE1 plasmid. We regard this transformation as an appropriate model for chloroplast transformation.

Bacteria↗