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PubMed1982

[Responses of cat visual cortex neurons to local stimulation of the center of the receptive field with varying intensity].

The on-responses of striate cortical neurons in paralyzed cats were examined at dark adaptation by local stimulation of the receptive centre with stimuli of scotopic and mesopic range of intensity. The responses of 16% of the total amount of cells involved included phasic activation (type I). The responses of 68% of cells consisted of phasic and sluggish activation with phasic inhibition between them (type II). The responses of 16% of cells showed only slow inhibition (type III). The thresholds of phasic activation covered the range of 0.7-2200 td and were the same as those for the activation of cat cones. The thresholds of sluggish activation covered the range of 0.02-9 td, and coincided with those for rod inputs. The inhibitory effects were observed as phasic inhibition, breakdown of the monotony of the stimulus-response curve and as slow inhibition in on-responses as well. All inhibition effect occurred in mesopic range (0.7-2200 td).

Animals↗
PubMed2006

The population genetics of adaptation on correlated fitness landscapes: the block model.

Several recent theoretical studies of the genetics of adaptation have focused on the mutational landscape model, which considers evolution on rugged fitness landscapes (i.e., ones having many local optima). Adaptation in this model is characterized by several simple results. Here I ask whether these results also hold on correlated fitness landscapes, which are smoother than those considered in the mutational landscape model. In particular, I study the genetics of adaptation in the block model, a tunably rugged model of fitness landscapes. Considering the scenario in which adaptation begins from a high fitness wild-type DNA sequence, I use extreme value theory and computer simulations to study both single adaptive steps and entire adaptive walks. I show that all previous results characterizing single steps in adaptation in the mutational landscape model hold at least approximately on correlated landscapes in the block model; many entire-walk results, however, do not.

Adaptation, Physiological↗
PubMed2007

Absence of population structure of turbot (Psetta maxima) in the Baltic Sea.

We found low, albeit significant, genetic differentiation among turbot (Psetta maxima) in the Baltic Sea but in contrast to earlier findings we found no evidence of isolation by distance. In fact temporal variation among years in one locality exceeded spatial variation among localities. This is an unexpected result since adult turbot are sedentary and eggs are demersal at the salinities occurring in the Baltic. Our findings are most likely explained by the fact that we sampled fish that were born after/during a large influx of water to the Baltic Sea, which may have had the consequence that previously locally and relatively sedentary populations became admixed. These results suggest that populations that colonize relatively variable habitats, like the Baltic, face problems. Any adaptations to local conditions that may build up during stable periods may quickly become eroded when conditions change and/or when populations become admixed. Our results indicate that the ability of turbot to survive and reproduce at the low salinity in the Baltic is more likely due to phenotypic plasticity than a strict genetic adaptation to low salinity.

Adaptation, Biological↗
PubMed1994

Variations in the monocular components of fixation disparity.

Measurements of the monocular components of fixation disparity through small amounts of lateral prism show changes in the proportional contribution of each eye with changing vergence stimuli. Prism does not usually alter the independence of the activity of each eye during binocular viewing. This independence allows the monocular shares to fluctuate from moment to moment. Responses to prism include fixating with one eye or the other, shifting both eyes laterally in the same direction, and distributing the deviations between the two eyes. Some of these strategies reduce the deviation and are therefore adaptive. Others appear to maintain a fairly stable state which frequently involves resorting to the equivalence of a monocular form of localization. Prism adaptation follows decidedly different time courses and occurs to differing extents for the different subjects and for the different conditions tested. It is not uncommon for many of these changes to occur unilaterally. Voluntary activity seems to be an important factor in the processes associated with adaptation to prism.

Fixation, Ocular↗
PubMed2005

Thermal, cardiac and adrenergic responses to repeated local cooling.

The aim of this study was to ascertain whether repeated local cooling induces the same or different adaptational responses as repeated whole body cooling. Repeated cooling of the legs (immersion into 12 degrees C water up to the knees for 30 min, 20 times during 4 weeks = local cold adaptation - LCA) attenuated the initial increase in heart rate and blood pressure currently observed in control subjects immersed in cold water up to the knees. After LCA the initial skin temperature decrease tended to be lower, indicating reduced vasoconstriction. Heart rate and systolic blood pressure appeared to be generally lower during rest and during the time course of cooling in LCA humans, when compared to controls. All these changes seem to indicate attenuation of the sympathetic tone. In contrast, the sustained skin temperature in different areas of the body (finger, palm, forearm, thigh, chest) appeared to be generally lower in LCA subjects than in controls (except for temperatures on the forehead). Plasma levels of catecholamines (measured 20 and 40 min after the onset of cooling) were also not influenced by local cold adaptation. Locally cold adapted subjects, when exposed to whole body cold water immersion test, showed no change in the threshold temperature for induction of cold thermogenesis. This indicates that the hypothermic type of cold adaptation, typically occurring after systemic cold adaptation, does not appear after local cold adaptation of the intensity used. It is concluded that in humans the cold adaptation due to repeated local cooling of legs induces different physiological changes than systemic cold adaptation.

Adaptation, Physiological↗
PubMed1983

Sensory adaptation of Dictyostelium discoideum cells to chemotactic signals.

Postvegetative Dictyostelium discoideum cells react chemotactically to gradients of cAMP, folic acid, and pterin. In the presence of a constant concentration of 10(-5) M cAMP cells move at random. They still are able to respond to superimposed gradients of cAMP, although the response is less efficient than without the high background level of cAMP. Cells which are accommodated to 10(-5) M cAMP do not react to a gradient of cAMP if the mean cAMP concentration is decreasing with time. This indicates the involvement of adaptation in the detection of chemotactic gradients: cells adapt to the mean concentration of chemoattractant and respond to positive deviations from the mean concentration. Cells adapted to high cAMP concentrations react normally to gradients of folic acid or pterin. Adaptation to one of these compounds does not affect the response to the other attractants. This suggests that cAMP, folic acid, and pterin are detected by different receptors, and that adaptation is localized at a step in the transduction process before the signals from these receptors coincide into one pathway. I discuss the implications of adaptation for chemotaxis and cell aggregation.

Chemotaxis↗
PubMed1998

The role of NHERF and E3KARP in the cAMP-mediated inhibition of NHE3.

NHE3 is the apically located Na+/H+ exchanger in the gut and in the renal proximal tubule. Acute inhibition of this transporter by cAMP requires the presence of either of two NHE3-associated proteins, NHERF or E3KARP. It has been suggested that these proteins either directly regulate NHE3 activity after being phosphorylated by protein kinase A (PKA) or that they may serve as adapters that localize PKA near NHE3. We studied the role of NHERF and E3KARP in opossum kidney cells, which endogenously express NHE3, NHERF, and ezrin and display cAMP-dependent inhibition of NHE3. In vivo phosphorylation studies showed that NHERF is a phosphoprotein under basal conditions, but does not change its phosphorylation state after 8-bromo-cAMP treatment, and that E3KARP is not phosphorylated at all. Co-immunoprecipitation showed that NHERF and E3KARP bind both NHE3 and ezrin. Using cAMP analogs it was demonstrated that NHE3 activity, measured as sodium-dependent recovery of the intracellular pH after intracellular acidification, is inhibited by PKA type II. Because others have shown that ezrin binds PKA type II and that NHE3 is phosphorylated by PKA we suggest that NHERF and E3KARP are adapters that link NHE3 to ezrin, thereby localizing PKA near NHE3 to allow NHE3 phosphorylation.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed1993

An adaptation-induced pop-out in visual search.

The present study demonstrates that an object embedded in an array of identical objects can pop-out. Dependent on the stimuli preceding the search display, local (chromatic) adaptation causes an identical object to pop-out because it appears to have a colour (Expt 1) or brightness (Expt 2) that is slightly different from the colour and brightness of the other objects in the display. Experiment 3 shows that this pop-out even occurs when the stimulus preceding the search display is presented for only 100 msec.

Adaptation, Ocular↗
PubMed2004

Evolutionary biology: adaptive developmental plasticity in snakes.

The morphology of organisms is generally well matched to their environment, presumably because expression of their genes is tailored either at the population or the individual level to suit local conditions: for example, snake populations that persistently encounter large prey may accumulate gene mutations that specify a large head size, or head growth may be increased in individual snakes to meet local demands (adaptive developmental plasticity). Here we test the relative contributions of genetics and environment to the jaw sizes of two tiger snake populations: one that consumes small prey on the mainland, and an island population that relies on larger prey and has a larger jaw size. Although the idea of adaptive plasticity in response to environmental pressures is controversial, we find that both factors influence the difference in jaw size between the two populations, and the influence of developmental plasticity is greater in the island population.

Adaptation, Physiological↗
PubMed2002

Adaptations in arm movements for added mass to wrist or ankle during walking.

The aim of the present study was to answer the question whether adaptations to local perturbations are restricted to the perturbed limb or whether they induce a reorganization of all co-moving limbs. Specifically, we studied the adaptations in arm movements to mass perturbations in seven healthy adults during walking on a treadmill. Four different perturbation conditions were employed in random order (no perturbation, mass added to both wrists, to the right wrist, and to the right ankle). During each experimental condition ten different belt speeds (0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0 km/h) were successively offered, while the arm movements and the electromyographic activity of the musculus deltoid posterior and anterior were measured. The results indicated that cadence was not affected by adding mass to the wrist or ankle. However, adding mass to a wrist not only resulted in an increase in muscle activity and a decrease of movement amplitude of the perturbed arm, but also in alterations in the non-perturbed arm. Notably, adding mass to one ankle induced adaptive changes in both arms, in that both muscle activity and arm movement increased. The present results indicate that during walking the loading of one of the limbs induces a general reorganization, involving all participating bodily segments, presumably to maintain balance while providing rhythm constancy.

Adaptation, Physiological↗
PubMed2006

Dissemination of the hospital elder life program: implementation, adaptation, and successes.

OBJECTIVES: To describe the Hospital Elder Life Program (HELP) across dissemination sites, to detail adaptations, and to summarize advantages across sites. DESIGN: Cross-sectional survey. SETTING: HELP sites in acute care hospitals. PARTICIPANTS: Thirteen sites that enrolled 11,344 patients. MEASUREMENTS: Seventy-five closed- and open-ended questions describing details of the HELP site, procedures, staffing, outcomes tracked, and advantages. RESULTS: As of July 1, 2005, HELP had been fully implemented in 13 sites, with a median duration of 24 months (range 6.0-38.0). Although a high degree of fidelity to the original model was maintained, variations existed in staffing patterns, outcome tracking, and recommended HELP procedures. Adaptations were made across multiple domains, including enrollment criteria at 15.4% of sites, screening and assessment tools at 61.5%, and individual intervention protocols at 15.4% to 30.8%. Local circumstances drove these adaptations, with the most common reasons being lack of adequate staffing and logistical constraints. All sites conducted regular HELP staff meetings; other recommended quality assurance procedures were conducted at 46.2% to 92.3% of sites. Reported advantages of HELP included providing an educational resource at 100% of sites, improving hospital outcomes (e.g., delirium and functional decline) at 100%, providing nursing education and improving retention at 100%, enhancing patient and family satisfaction with care at 92.3%, raising visibility for geriatrics at 92.3%, and improving quality of care at 84.6%. CONCLUSION: This report describes the real-world implementation of HELP across 13 sites, documents their local adaptations and successes, and provides insight into how motivated institutions can create change to improve quality of care for older persons.

Aged↗
PubMed1998

Karyological, biochemical, and physiological aspects of Callophysus macropterus (Siluriformes, Pimelodidae) from the Solimões and Negro Rivers (central Amazon).

Karyological characteristics, i.e., diploid number, chromosome morphology and nucleolus organizer regions (NORs), biochemical characteristics, i.e., electrophoretic analysis of blood hemoglobin and the tissue enzymes lactate dehydrogenase (LDH), malate dehydrogenase (MDH), alcohol dehydrogenase (ADH), and phosphoglucose isomerase (PGI), and physiological characteristics, i.e., relative concentration of hemoglobin and intraerythrocytic concentrations of organic phosphates were analyzed for the species Callophysus macropterus collected from Marchantaria Island (white water system--Solimões River) and Anavilhanas Archipelago (black water system--Negro River). Karyological and biochemical data did not reveal significant differences between specimens collected at the two sites. However, the relative distribution of hemoglobin bands I and III (I = 16.33 +/- 1.05 and III = 37.20 +/- 1.32 for Marchantaria specimens and I = 6.33 +/- 1.32 and III = 48.05 +/- 1.55 for Anavilhanas specimens) and levels of intraerythrocytic GTP (1.32 +/- 0.16 and 2.76 +/- 0.18 for Marchantaria and Anavilhanas specimens, respectively), but not ATP or total phosphate, were significantly different, indicating a physiological adaptation to the environmental conditions of these habitats. It is suggested that C. macropterus specimens from the two collecting sites belong to a single population, and that they adjusted some physiological characteristics to adapt to local environmental conditions.

Adaptation, Biological↗
PubMed1996

Gene localization and syntenic mapping by FISH in the dog.

To begin development of a canine gene map and to define syntenic regions between the canine and human genomes, the technique of fluorescence in situ hybridization (FISH) was adapted to localize specific DNA sequences in canine metaphases. Genomic clones of canine origin as well as human yeast artificial chromosome clones were used to map canine loci. The immunoglobulin heavy-chain region was localized to canine chromosome 4qtel; the canine major histocompatibility locus, DLA, was found to be on chromosome 12qtel. Of particular interest, the canine X chromosome, which morphologically is highly similar to the human X, also showed syntenic localization of the clotting factor VIII (F8C) and factor IX (F9) genes to Xq28 and Xq26.3-->q27.1, respectively.

Animals↗
PubMed1999

Transmural microcirculatory blood flow distribution in right and left ventricular free walls of rabbits.

Within-layer regional myocardial flows in the left and right ventricles (LV, RV) and in LV with increased myocardial workload (beta(1)-adrenoceptor stimulation) were studied transmurally in anesthetized rabbits. Myocardial flow distribution was visualized with resolutions between 0.1 x 0.1- and 1 x 1-mm(2) pixels, using digital radiography combined with the (3)H-labeled desmethylimipramine deposition technique. The spatial pattern of flow distribution was quantitated by the coefficient of variation of regional flows (CV, related to global flow heterogeneity) and the correlation between adjacent regional flows (CA, inversely related to local flow randomness). CV was lower in LV than in RV [P < 0.05, nonparametric 2-way analysis of variance (NANOVA)]. When resolution was lowered from 0.1 x 0.1- to 1 x 1-mm(2) pixels, CV decreased by 70% in both LV and RV. CA was higher in LV than in RV (P < 0.05, NANOVA); the interventricular difference in CA was large over the resolutions between 0.4 x 0.4- and 1 x 1-mm(2) pixels. In LV, both CV and CA increased with depth of myocardium (P < 0.05, NANOVA); in subendocardium CV was high comparable with CV in RV (P = 0.47, NANOVA). The enhancement of myocardial workload decreased CV and tended to decrease CA in LV subendocardium (P < 0.05, P = 0.06, respectively; NANOVA). We conclude that 1) microregional flow distribution is less heterogeneous and less random in LV than in RV; 2) transmurally, in LV subendocardium global flow heterogeneity was the highest whereas local flow randomness was the lowest, so that clusters of low- or high-flow regions exist in this LV layer; and 3) global flow heterogeneity decreased and local flow randomness tended to increase (flow homogenizing occurred) in LV subendocardium with increasing myocardial workload. Thus the distributed pattern of myocardial microregional flows may be adaptable to local myocardial metabolic change.

Animals↗
PubMed2005

Adaptation of pulmonary O2 uptake kinetics and muscle deoxygenation at the onset of heavy-intensity exercise in young and older adults.

The purpose was to examine the adaptation of pulmonary O(2) uptake (Vo(2p)) and deoxygenation of the vastus lateralis muscle at the onset of heavy-intensity, constant-load cycling exercise in young (Y; 24 +/- 4 yr; mean +/- SD; n = 5) and older (O; 68 +/- 3 yr; n = 6) adults. Subjects performed repeated transitions on 4 separate days from 20 W to a work rate corresponding to heavy-intensity exercise. Vo(2p) was measured breath by breath. The concentration changes in oxyhemoglobin, deoxyhemoglobin (HHb), and total hemoglobin/myoglobin were determined by near-infrared spectroscopy (Hamamatsu NIRO-300). Vo(2p) data were filtered, interpolated to 1 s, and averaged to 5-s bins. HHb-near-infrared spectroscopy data were filtered and averaged to 5-s bins. A monoexponential model was used to fit Vo(2p) [phase 2, time constant (tau) of Vo(2p)] and HHb [following the time delay (TD) from exercise onset to the start of an increase in HHb] data. The tauVo(2p) was slower (P < 0.001) in O (49 +/- 8 s) than Y (29 +/- 4 s). The HHb TD was similar in O (8 +/- 3 s) and Y (7 +/- 1 s); however, the tau HHb following TD was faster (P < 0.05) in O (8 +/- 2 s) than Y (14 +/- 2 s). The slower Vo(2p) kinetics and faster muscle deoxygenation in O compared with Y during heavy-intensity exercise imply that the kinetics of muscle perfusion are slowed relatively more than those of Vo(2p) in O. This suggests that the slowed Vo(2p) kinetics in O may be a consequence of a slower adaptation of local muscle blood flow relative to that in Y.

Adaptation, Physiological↗
PubMed1984

Chromosomal sites of integration of simian virus 40 DNA sequences mapped by in situ hybridization in two transformed hybrid cell lines.

Simian virus 40 DNA sequences, integrated on human chromosome 7 in two transformed human-mouse hybrid somatic cell lines, were mapped to a specific chromosomal locus by in situ hybridization. To detect the integrated viral DNA by in situ hybridization, we increased the sensitivity of the technique by using as a probe 125I-labeled simian virus 40 cRNA (2 X 10(9) to 3 X 10(9) dpm/micrograms) prepared by in vitro transcription of simian virus 40 DNA with high-specific-radioactivity [125I]CTP. Although the viral nucleic acid was shown by blot hybridization in the two cell lines to be integrated in different restriction fragments, it was shown by in situ hybridization in the two cell lines to map to the same position, q31, on the long arm of human chromosome 7. The viral DNA integration sites were localized with a precision of +/- 1 silver grain diameter, equivalent to about 6.2 X 10(7) nucleotide pairs in the human genome. The procedures we describe may be adapted for localization of any gene on diploid chromosomes that can be cloned in a recombinant DNA vector.

Animals↗
PubMed1996

Medical outreach to Armenia by telemedicine linkage.

Telemedicine, an electronic mode of transmitting medical information interactively between remote sites, was launched as an educational support for a 3-year-old medical partnership between Boston University School of Medicine and Emergency Hospital, of Yerevan, Armenia. Emergency Hospital is the first site in Armenia to have an audiographic teleconference capability linking it to a major medical center. Emergency Hospital and Boston University School of Medicine share the remote connection in order to allow educational conferences, peer consultations, and distance learning to take place, thus enhancing the partnership's aims to improve the emergency and trauma care system of Yerevan. To date, eight teleconferences have been transmitted linking 100 physicians, nurses and hospital administrators. The teleconference program provides, in effect, a formal continuing medical education program for Emergency Hospital. It is a key tool of low-cost technology transfer with the potential of broadening resources over the wide territory of the 15 republics of the former Soviet Union. The telemedicine system is comprised of Optel Communications' Remote Viewing System computer hardware and software plus two dedicated AT&T telephone lines. The system has been in use at Boston University School of Medicine for live voice and still image transmission between international sites since 1987. This level of technology suited environmental conditions in Armenia, marked by frequent power outages and unreliability of local telephone connections. A protocol for presentations was established governing length of time, number of visuals per session, visual format, compatibility with interpretive services, congruence with project mission, and adaptability to local conditions that was shown to provide clear and concise delivery of the information necessary. This paper reports the process of development, installation, and initial use of the technology in one nation of the post-Soviet world.

Armenia↗