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Results for “ADAPTATION, BIOLOGICAL”

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At least 271 records · Page 15Linked to original sources
PubMed2005

The evolutionary value of recombination is constrained by genome modularity.

Genetic recombination is a fundamental evolutionary mechanism promoting biological adaptation. Using engineered recombinants of the small single-stranded DNA plant virus, Maize streak virus (MSV), we experimentally demonstrate that fragments of genetic material only function optimally if they reside within genomes similar to those in which they evolved. The degree of similarity necessary for optimal functionality is correlated with the complexity of intragenomic interaction networks within which genome fragments must function. There is a striking correlation between our experimental results and the types of MSV recombinants that are detectable in nature, indicating that obligatory maintenance of intragenome interaction networks strongly constrains the evolutionary value of recombination for this virus and probably for genomes in general.

Evolution, Molecular↗
PubMed2004

Biochemical and enzymological aspects of the symbiosis between the deep-sea tubeworm Riftia pachyptila and its bacterial endosymbiont.

Riftia pachyptila (Vestimentifera) is a giant tubeworm living around the volcanic deep-sea vents of the East Pacific Rise. This animal is devoid of a digestive tract and lives in an intimate symbiosis with a sulfur-oxidizing chemoautotrophic bacterium. This bacterial endosymbiont is localized in the cells of a richly vascularized organ of the worm: the trophosome. These organisms are adapted to their extreme environment and take advantage of the particular composition of the mixed volcanic and sea waters to extract and assimilate inorganic metabolites, especially carbon, nitrogen, oxygen and sulfur. The high molecular mass hemoglobin of the worm is the transporter for both oxygen and sulfide. This last compound is delivered to the bacterium which possesses the sulfur oxidizing respiratory system, which produces the metabolic energy for the two partners. CO2 is also delivered to the bacterium where it enters the Calvin-Benson cycle. Some of the resulting small carbonated organic molecules are thus provided to the worm for its own metabolism. As far as nitrogen assimilation is concerned, NH3 can be used by the two partners but nitrate can be used only by the bacterium. This very intimate symbiosis applies also to the organization of metabolic pathways such as those of pyrimidine nucleotides and arginine. In particular, the worm lacks the first three enzymes of the de novo pyrimidine biosynthetic pathways as well as some enzymes involved in the biosynthesis of polyamines. The bacterium lacks the enzymes of the pyrimidine salvage pathway. This symbiotic organization constitutes a very interesting system to study the molecular and metabolic basis of biological adaptation.

Animals↗
PubMed1998

In vivo knee joint loading and kinematics before and after ACL transection in an animal model.

Osteoarthritis (OA) is typically diagnosed in humans in its final stage when joint movement becomes painful. Clinical information about the onset and the mechanisms triggering the degenerative responses are virtually non-existent. However, research on animal models of experimental OA shows that joint adaptations associated with the onset of OA can be detected as early as two to four weeks following disruption of the normal joint mechanics. Transection of the anterior cruciate ligament (ACL) has been shown to cause OA-like symptoms in various animal models including the cat. However. the changes in joint loading responsible for the early tissue responses have not been quantified in vivo. Consequently, the relationship between abnormal joint loading and the onset of OA remains unknown. The purpose of this study was to quantify knee loading before and early after ACL transection in the cat. Knee mechanics were assessed by measuring patellar tendon forces, gastrocnemius forces, knee flexor and extensor EMGs, and hindlimb kinematics before and 5, 7, and 9 days following ACL transection in six experimental and two sham-operated animals. The knee mechanics were not affected by sham-surgery but the muscular forces. knee extensor EMGs, and knee range of motion were reduced following ACL transection compared to corresponding pre-intervention values. These results suggest that ACL transection causes a general unloading and changed kinematics of the knee. We speculate that the decrease in loading and the altered kinematics are responsible for the onset of biologic adaptations of the knee. Precise data about the local joint contact mechanics before and after ACL transection are now required to further relate the detailed changes in the knee mechanics to the early joint changes.

Animals↗
PubMed1998

The relevance of hydroxyapatite and spongious titanium coatings in fixation of cementless stems. An experimental comparative study in rat femur employing histological and microangiographic techniques.

Pure titanium rods plasma-spray coated with hydroxyapatite (HA) or porous titanium (Ti) of controlled roughness were implanted bilaterally in the distal femur of Sprague-Dawley rats to compare the extent of bone growth on the two types of coating. The relevance of other factors, like mechanical stability and biological adaptation of the bone to the insertion of a foreign body implant, were investigated in femora which were over-reamed (absence of primary fit) or reamed without insertion of the rod. Continuous tetracycline labeling for the first 30 days and for the last 2 weeks in the 90-day group was performed; histological/histometric, fluorescence and microangiographic studies were carried out on serial sections of the implanted and control femora. In the group of stable implants, HA-coated rods showed 90% integration versus 53% with Ti-coated implants (P < 0.001); in over-reamed implants neither surface bone growth nor endosteal fixation occurred, and both types of rods were surrounded by a thick layer of connective tissue. The study documented early adhesion of osteoblasts and direct deposition of bone matrix on the substrate, while on spongious titanium osteogenesis was observed only in proximity to the surface. Remodeling of the reactive, primary bone to mature, lamellar bone took the form of a capsule surrounding the implants and radial bridges connecting the latter to the endosteal surface. The number, height and thickness of these bridges appeared to be the factors determining implant stability, rather than the extent of the bony capsule on the perimeter of the implant. Integration was a function not only of mechanical conditions and surface geometry, but also of the biological response of the whole bone to changes in the vascularization pattern. The reported phenomena can be seen more easily in experimental models involving small rodents because of their fast bone turnover and revascularization, but it is expected that they take place, even at a lower speed, in clinical situations like cementless stems of total hip replacement.

Angiography↗
PubMed1979

Psychological aspects of anorexia: areas for study.

Anorexia and weight loss are frequently the first manifestations of cancer. Although psychological reasons are frequently included as a partial explanation for loss of appetite and weight in the cancer patient, there have been no systematic studies which establish the nature of this relationship. It is proposed that anorexia and cachexia are at times somatic consequences of the cancer patient's beliefs and attitudes about their disease and its treatments. The inability to overcome a sense of hopelessness leads to an adaptive biological reaction called conservation-withdrawal. The effects of the reaction of disengagement and inactivity in relation to the external world which includes external nutriment may be constructive or destructive depending on when it is experienced and the length of time the reaction continues. How this reaction is initiated and mediated biologically and how it may be related to and can be reversed by a shift in motivation are questions of great importance.

Adjustment Disorders↗
PubMed1976

Two concepts of adaptation: Darwin's and psychology's.

The paper takes issue with the traditional view of Darwin's influence on psychology; namely, that it is he who passed on to psychology the concept of individual adaptation. Three arguments are presented: a) that Darwin, qua scientist, was only interested in species adaptation, an entirely different concept from that of individual adaptation, b) that Darwin's writings on individual adaptation are so unexceptional that it is inconceivable that psychologists should have been influenced by them and c) that the two concepts are logically incompatible since species adaptation presupposes a strict hereditary determinism, while individual adaptation conceives of the organism either as free and undetermined or else as determined by the environment.

Adaptation, Biological↗
PubMed1995

Structural adaptations for gliding in mammals with implications for locomotor behavior in paromomyids.

The gliding abilities of paromomyid plesiadapiforms are evaluated through a functional analysis of long bone morphology in a comparative sample of modern gliders and related nongliders. Relationships between body mass, long bone lengths, and long bone midshaft cross-sectional areas are explored. Theory suggests that gliders should have long humeri and femora to improve aspect ratio, and that larger gliders should have relatively longer limb bones than smaller gliders to minimize drag and patagial loading at greater body masses. Comparisons between extant taxa support these predictions: gliders have relatively longer humeri and femora than those of nongliders, and glider long bone lengths scale with positive allometry, while the scaling of nonglider long bones does not differ from isometry. Preliminary analysis of distal to proximal limb segment proportions further suggests that bone lengthening is, to some extent, related to patagial attachment site, although humeri and femora are relatively long in all of the gliders, regardless of attachment site. The proportions of paromomyids relative to those of extant mammals do not support a gliding interpretation for these fossils.

Adaptation, Biological↗
PubMed2006

Neural activity related to self- versus externally generated painful stimuli reveals distinct differences in the lateral pain system in a parametric fMRI study.

Self-generated sensory stimulation can be distinguished from externally generated stimulation that is otherwise identical. To determine how the brain differentiates external from self-generated noxious stimulation and which structures of the lateral pain system use neural signals to predict the sensory consequences of self-generated painful stimulation, we used functional magnetic resonance imaging to examine healthy human subjects who received thermal-contact stimuli with noxious and non-noxious temperatures on the resting right hand in random order. These stimuli were internally (self-generated) or externally generated. Two additional conditions served as control conditions: to account for stimulus onset uncertainty, acoustic stimuli preceding the same thermal stimuli were used with variable or fixed delays but without any stimulus-eliciting movements. Whereas graded pain-related activity in the insula and secondary somatosensory cortex (SII) was independent of how the stimulus was generated, it was attenuated in the primary somatosensory cortex (SI) during self-generated stimulation. These data agree with recent concepts of the parallel processing of nociceptive signals to the primary and secondary somatosensory cortices. They also suggest that brain areas that encode pain intensity do not distinguish between internally or externally applied noxious stimuli, i.e., this adaptive biological mechanism prevents harm to the individual. The attenuated activation of SI during self-generated painful stimulation might be a result of the predictability of the sensory consequences of the pain-related action.

Adult↗
PubMed1993

Determination of metabolites by 1H NMR and GC: analysis for organic osmolytes in crude tissue extracts.

World-wide salinity and drought problems necessitate the understanding of biological adaptation to water deficit. Osmotic adjustment via organic solutes is a common strategy for organisms to deal with water deficit problems. Numerous water-soluble organic metabolites across several chemical classes are commonly utilized as osmolytes, including betaines, sulfonium and sulfonate compounds, amino acids, carbohydrates, and polyols. To deal with the complexity and variability in osmolyte composition, we have devised an analytical approach that combines high-resolution 1H NMR and GLC to provide both structure identification and quantification of a broad spectrum of compounds. This combined approach also facilitated direct analyses of crude tissue extracts without extensive sample preparation, making it well-suited for a convenient screening of potential osmolytes. The structures of known osmolytes were confirmed from two-dimensional total correlation 1H NMR spectra, which also yielded structural information about unknown compounds. Five each terrestrial plant and marine animal species were examined for 41 metabolites, including osmolyte candidates glycinebetaine, dimethylsulfoniopropionate, taurine, proline, glycine, asparagine, alanine, glutamine, glucose, and sucrose. The osmotic function of glycinebetaine, proline, asparagine, glutamine, glucose, and sucrose was also demonstrated in leaves of Distichlis spicata under different salinity treatments.

Amino Acids↗
PubMed1987

Cannibalism and autotomy as predator-prey relationship for monoxenous Sarcosporidia.

In search for the final host of Sarcocystis gallotiae, sarcocysts of naturally infected Canarian lizards, Gallotia galloti, were fed to vertebrate predators of the lizard. Repeated transmission experiments remained negative. Routine check of the feces of the wild G. galloti revealed shedding of sporocysts. The sporocysts were administered to small vertebrates, which may function as prey for G. galloti. The transmission experiments remained negative. The observation of a high intraspecific aggression of G. galloti, including cannibalism and autotomy, seemed to support the hypothesis that this behavior might be the base of a an unexpected predator-prey relationship. Sarcocysts of S. gallotiae, fed to two laboratory-bred G. galloti resulted in excretion of sporulated sporocysts measuring 9.7 (9.2-12.2) X 7.7 (6.6-9.2) microns. Oral inoculation of two laboratory-bred G. galloti with experimentally gained sporocysts, led to the development of sarcocysts of 150-200 microns in length and 80-110 microns in width in the musculature of the lizards 153 days p.i. The sarcocysts were identified as S. gallotiae by light and electron microscopy. In epithelial cells of the intestine of G. galloti, which had experimentally been infected with sarcocysts of S. gallotiae, stages of gamogony and sporogony were found. We suggest that the life cycle of S. gallotiae is monoxenous and not obligatorily heteroxenous. The genus Sarcocystis seems to be more flexible in its biologic adaptability to utilize autotomy and cannibalism for completing its cycle than had heretofore been assumed.

Animals↗
PubMed2004

Spectacular Batesian mimicry in ants.

The mechanism by which palatable species take advantage of their similarity in appearance to those that are unpalatable, in order to avoid predation, is called Batesian mimicry. Several arthropods are thought to be Batesian mimics of social insects; however, social insects that are Batesian mimics among themselves are rare. In Malaysia we found a possible Batesian mimic in an arboreal ant species, Camponotus sp., which was exclusively observed on foraging trails of the myrmicine ant Crematogaster inflata. The bright yellow and black colouring pattern, as well as the walking behaviour, were very similar in both species. We observed general interactions between the two species, and tested their palatability and the significance of the remarkably similar visual colour patterns for predator avoidance. Prey offered to C. inflata was also eaten by Camponotus workers in spite of their being attacked by C. inflata, indicating that Camponotus sp. is a commensal of C. inflata. An experiment with chicks as potential predators suggests that Camponotus sp. is palatable whereas C. inflata is unpalatable. After tasting C. inflata, the chicks no longer attacked Camponotus sp., indicating that Camponotus sp. is a Batesian mimic of Crematogaster inflata.

Adaptation, Biological↗