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At least 469 records · Page 26Linked to original sources
PubMed1982

[Biology of myocardial adaptation to mechanical overload].

Chronic mechanical cardiac overload induces several adaptational processes, such as that provided by the Starling's law, which, allow the heart to function normally during a given period of time. Compensatory hypertrophy is, from a myocardial point of view, characterized by two main adaptational factors: hypertrophy due to a stimulation of protein synthesis and the slowing of the shortening velocity. This drop in contractility has undoubtedly been demonstrated in some experimental models, it is due to an isoenzymatic shift of myosin which is responsible for a depressed myosin ATPase activity. It has been clearly shown that this improves the efficiency of contraction, since for a given tension, the hypertrophied fiber produces less heat. Such a change does in fact exist in human heart but seems to have a limited physiological significance and in, any case, cannot explained the striking decrease in contractility which characterizes the final step of heart failure.

Adaptation, Physiological↗
PubMed2006

[Biological responses to low dose radiation--hormesis and adaptive responses].

"Hormesis" is defined, originally in the field of toxicology, as a phenomenon in which a harmful substance gives stimulating effects to living organisms when the quantity is small. The concept was extended and applied to ionizing radiation, high doses of which are harmful. Although radiation has been thought to be, based on findings in high dose ranges, harmful no matter low the dose is, recent investigation revealed that living organisms possess the ability to respond to low-dose radiation in very sophisticated ways. A good example of such responses is the so-called radiation adaptive response, a process in which acquired radioresistance is induced by low-dose radiation given in advance. The stimulation of certain bioprotective functions, including antioxidative capacity, DNA repair functions, apoptosis, and immune functions are thought to underly the adaptive response. The adaptive response is effective for chromosome induction, acute death, and tumorigenesis induced by high doses of radiation. Radiation hormesis and adaptive response provide a new scope in the risk assessment and medical application of ionizing radiation.

Adaptation, Biological↗
PubMed2004

[Biological characteristics of the adapted rabies virus 3aG-V in Vero cell].

OBJECTIVE: To study the biological features of the adapted rabies virus 3aG-V in Vero cell. METHODS: The virus structure, culture condition, pathogenicity, immunocompetence, toxicity and protective efficiency were studied. RESULTS: The rabies virus 3aG-V strain could well adapt to Vero cell, the pathogenicity was very weak and the immunogenicity was very good. CONCLUSION: The Vero cell-adapted rabies virus strain may possibly be used as a vaccine strain.

Animals↗
PubMed1967

Humanistic biology.

Explore the source record for details and available documents.

Adaptation, Biological↗
PubMed1983

Ethanol and biological membranes: injury and adaptation.

Ethanol intoxication affects the protein and lipid constituents of biological membranes. Mitochondria exhibit specific decreases in components of the electron transport chain and in protein synthesis. In vitro ethanol reduces the transition temperatures of membrane-bound enzyme activities and decreases the order parameter. On the other hand, both are increased after chronic ethanol administration. After chronic ethanol treatment membranes are resistant to disordering by ethanol, possibly owing to an increased saturation of mitochondrial phospholipids, particularly cardiolipin. The increased rigidity of mitochondrial and synaptosomal membranes is associated with reduced binding of ethanol and of the general anesthetic halothane. The data suggest that initially ethanol increases the fluidity of all biological membranes. If continued chronically, this effect is balanced by a change in the lipid composition of the membranes, which increases their rigidity and makes them resistant to disordering by ethanol (homeoviscous adaptation). The change in molecular order reduces the binding of ethanol and other compounds, but also impairs a variety of membrane-bound functions. These changes may play a role in tolerance to ethanol and cross-tolerance to anesthetics, and in the pathogenesis of maladies associated with alcohol abuse.

Adenosine Triphosphatases↗
PubMed1983

Light and dark adaptation in Phycomyces light-growth response.

Sporangiophores of the fungus Phycomyces exhibit adaptation to light stimuli over a dynamic range of 10(10). This range applies to both phototropism and the closely related light-growth response; in the latter response, the elongation rate is modulated transiently by changes in the light intensity. We have performed light- and dark-adaptation experiments on growing sporangiophores using an automated tracking machine that allows a continuous measurement of growth velocity under controlled conditions. The results are examined in terms of the adaptation model of Delbrück and Reichardt (1956, Cellular Mechanisms in Differentiation and Growth, 3-44). The "level of adaptation," A, was inferred from responses to test pulses of light by means of a series of intensity-response curves. For dark adaptation to steps down in the normal intensity range (10(-6)-10(-2) W/m2), A decays exponentially with a time constant b = 6.1 +/- 0.3 min. This result is in agreement with the model. Higher-order kinetics are indicated, however, for dark adaptation in the high-intensity range (10(-2)-1 W/m2). Adaptation in this range is compared with predictions of a model relating changes in A to the inactivation and recovery of a receptor pigment. In response to steps up in intensity in the normal range, A was found to increase rapidly, overshoot the applied intensity level, and then relax to that level within 40 min. These results are incompatible with the Delbrück-Reichardt model or any simple generalizations of it. The asymmetry and overshoot are similar to adaptation phenomena observed in systems as diverse as bacterial chemotaxis and human vision. It appears likely that light and dark adaptation in Phycomyces are mediated by altogether different processes.

Adaptation, Biological↗
PubMed1999

Identification of Grb4/Nckbeta, a src homology 2 and 3 domain-containing adapter protein having similar binding and biological properties to Nck.

Adapter proteins made up of Src homology (SH) domains mediate multiple cellular signaling events initiated by receptor protein tyrosine kinases. Here we report that Grb4 is an adapter protein closely related to but distinct from Nck that is made up of three SH3 domains and one SH2 domain. Northern analysis indicated that both genes are expressed in multiple tissues. Both Nck and Grb4 proteins could associate with receptor tyrosine kinases and the SH3-binding proteins PAK, Sos1, and PRK2, and they synergized with v-Abl and Sos to induce gene expression via the transcription factor Elk-1. Although neither protein was transforming on its own, both Nck and Grb4 cooperated with v-Abl to transform NIH 3T3 cells and influenced the morphology and anchorage-dependent growth of wild type Ras-transformed cells. Nck and Grb4 therefore appear to be functionally redundant.

Adaptor Proteins, Signal Transducing↗