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Results for “directed evolution”

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At least 1,261 records · Page 70Linked to original sources
PubMed2001

The molecular genetics of therapeutic resistance in malignant astrocytomas.

The adverse prognosis associated with malignant astrocytomas (MA) is due in part to the development of resistance by the tumor to chemo- and radiotherapy-induced cytotoxic damage. The mechanisms of resistance are poorly understood but function at the level of the endothelial cell, the blood-brain barrier and the neoplastic cell itself. The classic examples of drug resistance proteins, such as the p-glycoprotein/multidrug resistance protein 1, have been identified within MA biopsy specimens. However, it is questionable to what degree, if at all, these proteins contribute directly to the evolution and prognosis of the MA. Surprisingly, there are specific genes, not traditionally associated with resistance, which appear increasingly relevant to both tumor progression and insensitivity to cytotoxic damage. These genes are involved in cell cycle regulation, and include the retinoblastoma susceptibility gene (Rb), the tumor suppressor gene p53, as well as those encoding the cyclins, their kinases and inhibitors. The interaction between the products of these genes and intratumoral environmental factors appears to involve a dynamic and prognostically adverse selection process. It is from this perspective that the mechanism(s) of hypoxic-ischaemic selection for resistance and its therapeutic repercussions will be analyzed.

Animals↗
PubMedDate not supplied

From chaos to a structured therapeutic community: treatment programme on Emiliehoeve, a farm for young addicts.

Within two years a centre for young addicts emerged; from a chaotic situation where drug use was frequent a drug-free therapeutic community developed with a solid structure; encounter group techniques were the major therapeutic tool. The community is located on a farm providing a great variety of work situations. The evolution in this direction is described, pointing out the failings of several approaches attempted during the different phases of the programme.

Adult↗
PubMed2001

Pollinator-mediated selection on a flower color polymorphism in experimental populations of Antirrhinum (Scrophulariaceae).

We quantified pollinator visit behavior, pollen receipt and export, and changes in allele and genotype frequencies from initial Hardy- Weinberg conditions in experimental arrays of two color morphs of snapdragons (Antirrhinum majus) visited by freely foraging bumble bees (Bombus appositus and B. flavifrons). The number of pollen grains received by a flower depended most on the number of pollinator visits to the flower, whereas the number of grains exported was best predicted by the total time pollinators spent inside the flower. The pattern of mating generally was assortative with respect to color, as bees tended to overvisit one color or the other within a foraging bout. In arrays where nectar was augmented in one color, the augmented color received both more visits and longer visits. Allele and genotype frequencies in offspring samples were in accord with qualitative expectations based on the pollinator observations, demonstrating that pollinators can directly influence the evolution of single-locus floral traits, at least under simplified experimental conditions.

Journal Article↗
PubMed2001

[Exercise in children with chronic disease].

Regular physical exercise is gaining acceptance as a prescription for the prevention, management and rehabilitation of diseases occurring in the pediatric and adolescent age group. Exercise is generally used to increase the physical capabilities of these young patients, but, at times, it can directly influence the evolution of the condition. However, in children with chronic diseases, enhanced physical activity can also be deleterious. A well structured exercise program should be implemented. This paper will focus on the role of exercise in different diseases including cardiovascular, pulmonary, neuromuscular disease, diabetes and obesity.

Adolescent↗
PubMed2001

[Formation of medical-demographic processes in the Russian Federation].

The authors analyze the specific features of the present medical and demographic situation in the Russian Federation, the naturally research regularities determining the evolution and development direction of population processes in the 20th century by using the populational advance to the demographic transition to the present-day reproduction as an example. Socioeconomic factors affecting the demographic structure of society are considered.

Adolescent↗
PubMedDate not supplied

[Comparative analysis of vestibular system development in various groups of mammals living under different environmental conditions].

We have conducted for the first time a comparative study of the prenatal development of the vestibular system in representatives of pinnipeds (Phocidae, Otariidae, Odobenidae) and cetaceans (Odontoceti, Mysticeti) in comparison with terrestrial mammals. This allowed us to perform a detailed study of the structural organization of the inner ear in species with different ecological specialization, to find out adaptive aspects and stages of the formation of cochlear and vestibular structures in each of the studied species, and to correlate it with the properties of the environment. Studies on early embryogenesis of the labyrinth in cetaceans and pinnipeds, which represent a special direction in the evolution of placentates, give a significant contribution to the solution of problem about the evolutionary origin of the labyrinth in mammals studied. Sensory systems clearly demonstrate the scope of evolutionary and adaptive transformations, which appear in mammals during the transition from the terrestrial to the aquatic mode of life. At the same time, these results may provide help in understanding the general trends of the development of structure and function of the inner ear in mammals as a whole.

Animals↗
PubMed2002

Germline engineering: the moral challenges.

Not only is the use of germline genetic engineering likely in the long run to be inevitable, there are also no convincing secular moral grounds to forbid this technology in principle. Instead, the general secular moral constraints on the use of germline genetic engineering are either procedural or without predetermined content. Nor can one develop a coherent distinction between eliminating disease and enhancing human abilities. At best, in secular morality one can establish the principle to proceed with care, though the invocation of the precautionary principle argues as much in favor of the development of germline genetic engineering as against its use. Because germline genetic engineering, by eliminating certain genetic defects, offers the prospect of decreasing human suffering and decreasing the use of prenatal diagnosis and abortion, there is an obligation, all else being equal, to change the human genome. In a post-modern world, humans face the challenge of directing their own evolution, although they share no common understanding of human destiny and purpose. Such understandings, though available within religious contexts, are not available to secular bioethics.

Bioethics↗
PubMedDate not supplied

Relationships between specialized cells, capillaries and intermediary cytofibrillary elements. Xth Note. Biological evolution of the emonctory subsystem and stereotype in invertebrates.

The paper points out the importance of homeostasis as the most general system of the organism (Ist order system) and the 2nd order subsystem which composes it, discussing the relations between them and the biological evolution of the emonctory subsystem in protists and invertebrates. The emonctory structures, functions and stereotype and their component parts are studied in protists, spongia, coelenterata and coelomata: lower worms, annelids, their hyponeurian descendents (arthropods, molluses) and epineurian descedents echinoderms and protochordates (Stomochordata, Tunicata, Cephalochordata). The structure, functions and stereotypes of protonephridia and metanephridia and of substitutive (vicarious) emonctory organs (nephrocytes and peritoneal cells) are studied in coelomatic invertebrates. Their evolution appears to be directioned to localize within the limits of the emonctory subsystem. During their evolution, some nephridial functions are performed by the vicarious emonctory organs. The evolution of the subsystem in invertebrates appears to be based on stable characters and their relationships with variable features.

Animals↗
PubMed2004

The effectiveness of wellness programs as a strategy for cost containment in acute care hospitals.

This study examines the effectiveness of hospital-based wellness programs in lowering both the acuity of illness of patients and the total expenses of acute care hospitals from a strategic management perspective. The subjects for this cross-sectional study were 164 community hospitals in 27 urban areas of Texas. The findings show that, after controlling for size, the number of wellness programs was significantly and negatively related to both the acuity of illness and total expenses. Further, the number of wellness programs offered did not vary significantly by type of ownership. The study concludes that reimbursement policies designed to provide financial incentives to promote wellness have been effective and suggests future directions for the evolution of health care management.

Acute Disease↗
PubMed1990

[The shaping of the clinical anatomical thinking of the pathological anatomist in a specialization lecture cycle in an institute for physician advanced training].

The directions of the evolution of clinico-anatomical approach by young pathologists during the specialization in the above institute are summarized. The work of pathologists consists of the disease history reading, making its written summary, autopsy with writing the protocol, histological examination, establishing the pathology diagnosis and epicrisis. All these stages should be an active thinking aiming at the comparison of clinical data with the results of macro- and microscopical examination and literature data.

Autopsy↗
PubMedDate not supplied

[Evolutionary study of 81 children with celiac disease].

A review of 81 children with celiac disease over a period of 5 years is presented. These cases were seen at the Gastroenterological Unit of the Hospital de Nińos Roberto del Río, during years 1970 through 1972. 62% of the patients (50) were placed under control of their disease, the rest were studied and diagnosed only for other centers. The short term evolution was good in 48 children (96%), while the medium and long term evolution, 2 to 5 years, was good only in 56% of the patients. This evolution was in direct relationship to the fulfillment of the dietary indications. The therapeutic test was positive among the studied group. A delay was observed in 80% of the cases that lasted from 1 to 6 months. The clinical and laboratory features of the group are analyzed, and the working method is described.

Biopsy↗
PubMedDate not supplied

[Hormones and development of sexual behaviour in the domestic sheep (author's transl)].

All motor patterns of male sexual behaviour can be observed in young lambs from the first days of the life. They considerably increase on weeks 2 to 5 when they decrease dramatically and remain stable up to over 6 months of age. This evolution has no direct relation with that of the physiological events. The adult female has a complete bisexual potentiality. The development of the sexual behaviour during ontogeny appears as a continuous process rather than to be limited to the period of puberty or sexual differentiation.

Animals↗
PubMed1993

[The genetic language: grammar, semantics, evolution].

The genetic language is a collection of rules and regularities of genetic information coding for genetic texts. It is defined by alphabet, grammar, collection of punctuation marks and regulatory sites, semantics. There is a review of these general attributes of genetic language, including also the problems of synonymy and evolution. The main directions of theoretical investigations of genetic language and neighbouring questions are formulated: (1) cryptographic problems, (2) analysis of genetic texts, (3) theoretical-linguistic problems, (4) evolutionary linguistic questions. The problem of genetic language becomes one of the key ones of molecular genetics, molecular biology and gene engineering.

Codon↗
PubMedDate not supplied

[The duration of surgical procedures as a factor in the development of postoperative osteomyelitis].

In the period from January 1st, 1969, to December 31st, 1988, 585 osteosyntheses of the closed bone fractures of lower limbs were performed at the Orthopedic department at the Military Hospital in Nis. At the same period 25 postoperative osteomyelitis were registered, i.e., 4.27%. The average duration of osteosynthesis in the tested group of patients was 84.6 minutes, and 54 minutes in control group. The difference of the average duration of osteosynthesis between groups was significant. The type and size of metal implants did not directly affect the evolution of postoperative bone infection unless the correct implantation was done and unless they were made of standardized leaguers.

Adolescent↗
PubMed1996

Extended-coverage-bladder G-suits can provide improved G-tolerance and high Gz foot pain.

METHOD: An extended coverage bladder (ECB) G-suit was evaluated on the DCIEM centrifuge against the current service G-suit (CSU-15/P) in two separate series of experiments. The ECB G-suit covered approximately 85% of the lower body measuring from the umbilicus and all five bladders completely encircled each leg and the lower trunk. The CSU-15/P G-suit covered approximately 30% of the lower body and its five bladders were located only over the frontal aspect of each leg and the lower trunk. The first series of experiments involved five subjects from the highly experienced DCIEM A-team. A standard gradual onset rate (GOR) run was used and suit testing order was counterbalanced across subjects. RESULTS: The test condition G-tolerances are listed as mean +/- SEM; relaxed uninflated tolerances were 4.0 +/- 0.14 for the CSU-15/P suit vs. 4.1 +/- 0.09 for the ECB suit (ns, single tailed, paired t-test) while relaxed inflated tolerances were 4.7 +/- 0.19 for the CSU-15/P suit and 5.5 +/- 0.37 for the ECB suit (p = 0.02, single tailed, paired t-test). The straining tolerances were 8.1 +/- 0.44 for the CSU-15/P suit and 9.0 +/- 0.56 for the ECB suit (p = 0.01, single tailed, paired t-test). The second series involved nine subjects for the following three G-suit conditions; CSU-15/P, ECB with inflation limiters, and ECB with inflation limiters and foot bladders. Relaxed uninflated tolerances were 4.0 +/- 0.13, 4.0 +/- 0.08, and 3.9 +/- 0.10 (ns) while straining inflated tolerances were 9.4 +/- 0.48, 10.1 +/- 0.38 and 10.6 +/- 0.42, respectively (p = 0.01 between all three straining conditions, ANOVA with Scheffé F-test). The ECB G-suit with inflation limiters eliminated abdominal pain and discomfort. CONCLUSION: The ECB G-suit provides improved G-tolerance for both inflated relaxed and straining exposures. Foot bladders eliminated high Gz foot pain and improved straining G-tolerance by about half a Gz. The efficacy of ECB G-suits should be evaluated when used in conjunction with positive pressure breathing. While the ultimate G-suit has yet to be conceived and will no doubt be part of an integrated life support system, ECB G-suits are a step in the right direction in the evolution of life support garmentry.

Abdominal Pain↗
PubMed1976

[Direction of the clinical pathomorphosis of alcoholic delirium].

An examination of 348 patients with alcoholic delirium permitted to detect the main directions in the evolutional variability of the clinical picture. The authors distinguished 3 types in the development of a delirium: short-term with a complete and incomplete (abortive) variant; typical delirium with mono-and polymorphic structure of the syndrome; a protracted development in the form of a severe psychoses of a complex structure and a sluggish protracted variant with an obliviated symptomatology.

Alcohol Withdrawal Delirium↗
PubMed1993

Examples of evolution of microstructure in ceramics and composites.

In this article we describe a number of studies involving the direct observation of microstructural evolution. In general these investigations were carried out to establish the mechanistic paths involved. The materials studied range from fibers being evaluated for use in high-temperature ceramic composites to energetic materials used as propellants. In particular we discuss the room temperature imaging of materials difficult to image by conventional means and the use of the chamber atmosphere to influence microstructural evolution. Imaging of hydroxyapatite formed by chemical means is briefly described as an example of a difficult microstructure. Microstructural evolution during calcium aluminate cement hydration relies on the chamber atmosphere to control moisture loss from the hydrating specimens. In some instances microstructural evolution with heating occurred independently of the chamber atmosphere. Grain growth in PZT films formed by sol-gel processes depends strongly on temperature but does not appear to depend on the chamber atmosphere. This is also the case for the combustion of nitroamine propellants in that their combustion does not depend on access to an external source of oxygen. In other studies, the chamber atmosphere played an indirect role in determining microstructure. However, the mechanistic path driving microstructural evolution in copper-based inks used as conductive paths on electronic substrates is atmosphere dependent. These inks are formulated from copper powder, glass, and an organic binder, and the interaction of the binder with an oxidizing atmosphere allows it to be burned out before significant interaction occurs between the copper powder and the glass. Finally, the microstructural variations during the oxidation of structural composites at high temperature were used to allow assessments of their likely failure mechanisms.

Animals↗
PubMed1998

Evolution of dendritic patterns during alloy solidification: onset of the initial instability.

The evolution of a dendritic pattern from a planar solid-liquid interface during directional solidification of a binary alloy was investigated experimentally. The model alloy used was the transparent organic crystal succinonitrile doped with the laser dye coumarin 152. The buildup of solute ahead of the initially stable planar interface and the subsequent instability of the planar front were measured in detail and compared with recent theoretical calculations by Warren and Langer [Warren, J. A. & Langer, J. S. (1993) Phys. Rev. E 47, 2702- 2712]. The fluorescence of coumarin 152 was used for direct observations of the evolution of the solute concentration profile ahead of the initially planar solid-liquid interface. UV absorption was used to produce thermal perturbations of the sample that generated spatially periodic modulations of the planar interface. This technique allows for measurement of both positive and negative linear growth coefficients (determined from the growth or decay rate of the modulation after the perturbation is switched off) for a large range of wave vectors. Measurements of the evolution of the concentration profile and the linear growth coefficients, and the occurrence of the initial instability, were in good agreement with the Warren-Langer predictions.

Journal Article↗