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At least 451 records · Page 25Linked to original sources

PubMed2005

Evidence for the use of reflected self-generated seismic waves for spatial orientation in a blind subterranean mammal.

Subterranean mammals like the blind mole-rat (Rodentia: Spalax ehrenbergi) are functionally blind and possess poor auditory sensitivity, limited to low-frequency sounds. Nevertheless, the mole-rat demonstrates extremely efficient ability to orient spatially. A previous field study has revealed that the mole-rat can assess the location, size and density of an underground obstacle, and accordingly excavates the most efficient bypass tunnel to detour around the obstacles. In the present study we used a multidisciplinary approach to examine the possibility that the mole-rat estimates the location and physical properties of underground obstacles using reflected self-generated seismic waves (seismic 'echolocation'). Our field observations revealed that all the monitored mole-rats produced low-frequency seismic waves (250-300 Hz) at intervals of 8+/-5 s (range: 1-13 s) between head drums while digging a bypass to detour an obstacle. Using a computerized simulation model we demonstrated that it is possible for the mole-rat to determine its distance from an obstacle boundary (open ditch or stone) by evaluating the amplitude (intensity) of the seismic wave reflected back to it from the obstacle interface. By evaluating the polarity of the reflected wave the mole-rat could distinguish between air space and solid obstacles. Further, the model showed that the diffracted waves from the obstacle's corners could give the mole-rat precise information on the obstacle size and its relative spatial position. In a behavioural experiment using a special T-maze setup, we tested whether the mole-rat can perceive seismic waves through the somatosensory system and localize the source. The results revealed that the mole-rat is able to detect low frequency seismic waves using only its paws, and in most cases the mole-rats determined accurately the direction of the vibratory source. In a histological examination of the glabrous skin of the mole-rat's paws we identified lamellate corpuscle mechanoreceptors that might be used to detect low frequency seismic waves. The combined findings from these different approaches lead us to suggest that a specialized seismic 'echolocation' system could be used by subterranean mammals to determine the most energy-conserving strategy with which to bypass an obstacle, as well as to estimate their distance from the surface, keeping their tunnels at the optimal depth.

Adaptation, Physiological↗

PubMed2002

Adaptive control of vergence in humans.

Vergence eye alignment minimizes horizontal, vertical, and cyclodisparities to optimize stereo-depth perception. Only the horizontal component of vergence is under voluntary control. Couplings with voluntary version and horizontal vergence guide vertical vergence and cyclovergence. Can these couplings be modified in response to sensory demands on binocular vision? We have modified vertical vergence and cyclovergence in response to optical changes in disparity. Vertical vergence was stimulated with aniseikonic lenses that exaggerated vertical disparity in tertiary gaze. Vertical vergence adapted in an hour to produce nonconcomitant changes in vertical phoria that varied with vertical eye position in tertiary gaze. Cyclovergence was stimulated with cyclodisparities that varied with gaze elevation and convergence angle. Cyclovergence adapted within 2 hours to produce nonconcomitant changes in cyclophoria that varied with gaze elevation and convergence. The adaptive couplings for vertical vergence and cyclovergence are modeled as a combination of passive orbital mechanics and active gain control of the vertical recti and obliques. Vergence adaptation is a calibration process that adjusts the innervation for horizontal, vertical, and torsion components of vergence to the physical constraints set by the extraocular muscles and orbital connective tissues. Passive orbital mechanics simplify the neural control for precise vertical vergence and cyclovergence that are needed to achieve binocular alignment under open-loop conditions in response to perceived spatial location.

Adaptation, Physiological↗

PubMed2004

Effect of dietary fat on early morphological intestinal adaptation in a rat with short bowel syndrome.

Among factors promoting mucosal hyperplasia after bowel resection, long-chain fatty acids may have a special role. The purpose of the present study was to evaluate the effects of high-fat diet (HFD) on early intestinal adaptation in rats with short bowel syndrome (SBS). Male Sprague-Dawley rats underwent either a bowel transection with re-anastomosis (Sham rats) or 75% small bowel resection (SBS rats). Animals were randomly assigned to one of three groups: Sham rats fed normal chow (Sham-NC); SBS rats fed NC (SBS-NC); and SBS rats fed HFD (SBS-HFD). Rats were killed on days 3 or 14. Body weight and parameters of intestinal adaptation (overall bowel and mucosal weight, mucosal DNA and protein, villus height, and crypt depth) were determined at time of killing. By day 3, SBS-HFD rats demonstrated higher duodenal and jejunal bowel and mucosal weights and ileal villus height and jejunal crypt depth vs SBS-NC rats. By day 14 SBS-HFD rats continued to demonstrate increased duodenal and jejunal bowel weight and duodenal mucosal weight vs SBS-NC animals. We conclude that early exposure to HFD both augmented and accelerated structural bowel adaptation in a rat model of SBS.

Adaptation, Physiological↗

PubMed2003

Psychrophilic enzymes: hot topics in cold adaptation.

More than three-quarters of the Earth's surface is occupied by cold ecosystems, including the ocean depths, and polar and alpine regions. These permanently cold environments have been successfully colonized by a class of extremophilic microorganisms that are known as psychrophiles (which literally means cold-loving). The ability to thrive at temperatures that are close to, or below, the freezing point of water requires a vast array of adaptations to maintain the metabolic rates and sustained growth compatible with life in these severe environmental conditions.

Adaptation, Physiological↗

PubMedDate not supplied

Impaired intestinal cell proliferation and cell death in leptin-deficient obese mice.

BACKGROUND: After massive small-bowel resection and loss of absorptive capacity, residual intestine has compensatory ability to adapt by cellular hyperplasia and increased absorptive function. Growth factors have been shown to enhance intestinal adaptation, but the mechanisms involved are not well defined. Leptin has been shown to function as a trophic factor in the intestine and enhances carbohydrate absorption after small-bowel resection. Therefore, we hypothesized that leptin deficiency may impair the adaptive response by modulating cellular proliferation or cell death after small-bowel resection. METHODS: Twelve-week-old male lean control (C57BL/6J, n = 28) and leptin-deficient (Lep(ob), n = 24) obese mice underwent sham laparotomy, intestinal transection, or 50% proximal small-bowel resection. Mice were killed at 48 hours postresection, and remnant intestine was harvested. Phenotypic analysis to assess adaptation included characterization of cell proliferation (percentage BrdU incorporation), apoptosis (terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nickend labeling assay), and morphometric response (villus height, crypt depth). RESULTS: The percentage S-bromodeoxyuridine (BrdU) incorporation and apoptotic indices of obese transected mice were significantly lower than lean transected mice (7.3 vs 21.9% and 0.70 vs 1.53% respectively, p < .05). In resected animals, the percentage BrdU incorporation and apoptotic indices of obese resected mice were significantly lower than for lean resected (6.1 vs 22.0% and 0.93 vs 1.80% respectively, p < .05). No differences between groups, regardless of surgery, were identified in villus height or crypt depth. CONCLUSIONS: Therefore, we conclude that leptin deficiency impairs both cell proliferation and cell death in the early adaptive period after either small-bowel transection or resection.

Adaptation, Physiological↗

PubMed1984

Temporal frequency discrimination above threshold.

Temporal frequency discrimination was measured above threshold with a two-alternative spatial forced-choice procedure. Stimuli were two 1 deg homogeneous fields modulated around a mean luminance of 3.7 log trolands. Observers determined which of the two stimuli was modulated at a higher frequency. To avoid differences in apparent modulation depth as a cue for discrimination, all stimuli were matched in apparent modulation depth to an 11 Hz standard that was 0.5 log units above its threshold. Adaptation, caused by repeated presentation of suprathreshold stimuli, was avoided by using a 15 sec inter-trial interval. The relative difference thresholds (delta f/f) were a non-monotonic function of frequency. Discrimination was best near 1.5, 4.0 and 30.0 Hz (delta f/f = 0.08) and worst near 20.0 Hz (delta f/f = 0.50). Control experiments showed that the improvement in discrimination beyond 20.0 Hz was not an artifact of mismatches in apparent modulation depth. These results demonstrate the existence of multiple channels sensitive to different ranges of temporal frequency.

Adaptation, Ocular↗

PubMed2004

How do cormorants counter buoyancy during submerged swimming?

Buoyancy is a de-stabilizing force for diving cormorants that forage at shallow depths. Having to counter this force increases the cost of transport underwater. Cormorants are known to be less buoyant than most water birds but are still highly buoyant (rho= approximately 0.8 kg m(-3)) due to their adaptations for aerial flight. Nevertheless, cormorants are known to dive at a wide range of depths, including shallow dives where buoyancy is maximal. We analyzed the kinematics of underwater swimming of the great cormorant (Phalacrocorax carbo sinensis) in a shallow pool to discover and evaluate the mechanisms countering buoyancy while swimming horizontally. The birds maintained a very uniform cyclic paddling pattern. Throughout this cycle, synchronized tilting of the body, controlled by the tail, resulted in only slight vertical drifts of the center of mass around the average swimming path. We suggest that this tilting behavior serves two purposes: (1) the elongated bodies and the long tails of cormorants, tilted at a negative angle of attack relative to the swimming direction, generate downward directed hydrodynamic lift to resist buoyancy and (2) during the propulsive phase, the motion of the feet has a significant vertical component, generating a vertical component of thrust downward, which further helps to offset buoyancy. The added cost of the drag resulting from this tilting behavior may be reduced by the fact that the birds use a burst-and-glide pattern while swimming.

Animals↗

PubMed2004

Latency of adaptive vergence eye movements induced by vergence-vestibular interaction training in monkeys.

Clear vision of objects that move in depth toward or away from an observer requires vergence eye movements. The vergence system must interact with the vestibular system to maintain the object images on the foveae of both eyes during head movement. Previous studies have shown that training with sinusoidal vergence-vestibular interaction improves the frequency response of vergence eye movements during pitch rotation: vergence eye velocity gains increase and phase-lags decrease. To further understand the changes in eye movement responses in this adaptation, we examined latencies of vergence eye movements before and after vergence-vestibular training. Two head-stabilized Japanese monkeys were rewarded for tracking a target spot moving in depth that required vergence eye movements of 10 degrees/s. This target motion was synchronized with pitch rotation at 20 degrees/s. Both target and chair moved in a trapezoidal waveform interspersed with random inter-trial intervals. Before training, pitch rotation in complete darkness without a target did not induce vergence eye movements. Mean latencies of convergence and divergence eye movements induced by vergence target motion alone were 182 and 169 ms, respectively. After training, mean latencies of convergence and divergence eye movements to a target synchronized with pitch rotation shortened to 65 and 53 ms, and vergence eye velocity gains (relative to vergence target velocity) at the normal latencies were 0.68 and 1.53, respectively. Pitch rotation alone without a target induced vergence eye movements with similar latencies after training. These results indicate that vestibular information can be used effectively to initiate vergence eye movements following vergence-vestibular training.

Adaptation, Physiological↗

PubMed2003

Endotoxemia inhibits intestinal adaptation in a rat model of short bowel syndrome.

Sepsis is commonly associated with or complicates short bowel syndrome (SBS). The purpose of the present study was to investigate the effects of endotoxemia on intestinal adaptation in a rat model of SBS. Male Sprague-Dawley rats were divided into three experimental groups: Sham rats underwent bowel transection and re-anastomosis, SBS rats underwent 75% small bowel resection, and SBS-LPS rats underwent bowel resection and were given lipopolysaccharide. Bowel weight, organ weights, and parameters of intestinal adaptation (bowel and mucosal weights, mucosal DNA and protein, villus height, and crypt depth) were determined on day 15 following operation. The results of this study demonstrate that SBS rats showed a significant increase (vs. Sham) in jejunal and ileal bowel and mucosal weight, mucosal DNA and protein, villus height, and crypt depth. SBS-LPS animals demonstrated lower (vs. SBS rats) final body weight (215 +/- 7 vs. 287 +/- 10 g, P < 0.05), overall weight in duodenum (98+/- 2 vs. 119 +/-5 mg/cm, P < 0.05) and jejunum (144 +/- 9 vs. 189 +/- 16 mg/cm, P < 0.05), mucosal weight in jejunum (54 +/- 5 vs. 69 +/- 5 mg/cm, P < 0.05) and ileum (31 +/- 2 vs. 37 +/- 3 mg/cm, P < 0.05), mucosal DNA in jejunum (89 +/- 11 vs. 120 +/- 11 microg/cm, P < 0.05) and ileum (46 +/- 6 vs. 61 +/- 4 microg/cm, P < 0.05), jejunal crypt depth (152 +/- 19 vs. 189 +/- 12 microm, P < 0.05), and ileal villus height (405 +/- 63 vs. 515 +/- 30 pm, P < 0.05). In addition, the SBS group had no late (second week) mortality, whereas the SBS-LPS group had an 17% late mortality rate. In conclusion, in a rat model of SBS-LPS, endotoxemia appears to inhibit structural intestinal adaptation and increase mortality.

Animals↗

PubMed2003

[The male nurses' experiences of adaptation in clinical setting].

PURPOSE: The purpose of this study was to identified the male nurses' encounter in adapting themselves in the hospital settings dominated by the female nurses in number. METHOD: Data were collected through the in-depth interview of 16 male nurses and analysed through the grounded theory methodology. RESULT: The behaviors of male nurses for job-adaptation can be summarized as a series of struggles to consolidate their own ground. They have made tremendous efforts to hold their own ground in the nursing profession composed of a large numbers of female nurses, while they have experienced many difficulties and problems as minorities. They have struggled to adapt themselves professionally through efforts such as; challenging the social and professional barriers, identifying the job identity, empowering themselves through self-development and dedication, expanding their influence among colleagues. In spite of these efforts, they had the perception that nursing is not a lifelong occupation for them. Thus, they had tendency to find outlets of change to occupations. CONCLUSION: A specific strategy is needed to provide an environment that is helpful for males in integrating into and adapting to the nursing profession.

English Abstract↗

PubMed2004

Preventing enterocyte apoptosis after massive small bowel resection does not enhance adaptation of the intestinal mucosa.

BACKGROUND: After massive small bowel resection (SBR), increased rates of enterocyte apoptosis are observed in the remnant bowel via a mechanism requiring bax gene expression. This study tested the hypothesis that adaptive mucosal growth could be enhanced by the novel strategy of preventing postresection enterocyte apoptosis. METHODS: Male bax-null and corresponding wild-type (WT) mice underwent a 50% proximal SBR or sham operation (bowel transaction with reanastomosis alone). Mice were killed after a full adaptation interval of 1 month. Adaptation was measured in the remnant ileum as alterations in villus height, crypt depth, and wet weight. Rates of enterocyte proliferation were derived by immunostaining of crypt enterocytes for Ki-67 and apoptosis by the presence of apoptosis bodies. RESULTS: The expected increase in enterocyte apoptosis after SBR occurred in the WT mice but was unchanged in the bax-null mice. Despite the prevention of postresection apoptosis in the bax-null mice, all parameters of adaptation and proliferation increased equally after SBR in both groups of mice. CONCLUSIONS: Bax deficiency prevents the increase in enterocyte apoptosis that occurs after massive SBR throughout the entire adaptation period. Attenuation of postresection enterocyte apoptosis does not augment mucosal adaptation to massive intestinal loss.

Adaptation, Physiological↗

PubMedDate not supplied

Adaptive strategies of mothers with children with attention deficit hyperactivity disorder: enfolding and unfolding occupations.

OBJECTIVE: To describe adaptive strategies of time use among mothers with children with attention deficit hyperactivity disorder (ADHD) and, in particular, the adaptive strategies of unfolding occupations that were commonly used by these mothers. METHOD: In-depth interviews were conducted with 17 families with children with ADHD. Parents were asked to describe their family's daily schedule, routines, and how occupations were performed. Data were analyzed using the grounded theory approach. FINDINGS: Mothers used three adaptive strategies: enfolding occupations, temporal unfolding of occupations, and unfolding occupations by inclusion. Enfolding occupations means performing more than one occupation at a time. Unfolding occupations means taking chunks of activities or occupations out of previously established sequences of enfolded occupations to be performed at a different time (temporal unfolding) or by a different person (unfolding by inclusion). The child's special needs and the availability of financial and human resources influenced the selection of adaptive strategy. Using these adaptive strategies enabled the mothers to care for their children. However, using enfolding or temporal unfolding meant that mothers had less time for other occupations. CONCLUSION: The benefits and limitations of the adaptive strategies of enfolding and unfolding occupations suggest a need to study time use in different contexts. Before suggesting use of these adaptive strategies by parents of children with special needs, therapists need to be aware of the family's financial and human resources.

Adult↗

PubMed2003

Emotional expression and depth processing of trauma and their relation to long-term survival in patients with HIV/AIDS.

OBJECTIVE: This study examined the relationship between emotional expression and depth processing of trauma and long-term survival of patients living with AIDS. A further purpose was to examine the immune, health behavior and psychosocial correlates of emotional disclosure and depth processing. METHOD: Subjects wrote essays describing their reactions to past traumas; these were scored for emotional expression and depth processing (positive cognitive appraisal change, experiential involvement, self-esteem enhancement and adaptive coping strategies). Two HIV-seropositive groups were recruited for this study; long-term survivors (LTS; n=46) patients who had survived at least 4 years past a Category C (AIDS defining) symptom prior to starting protease inhibitors and an equivalent HIV-seropositive comparison group (ECOMP(LTS); n=89) who had CD4+ cells between 150 and 500, and had no history of Category C symptoms. The groups were equivalent on age, gender, ethnicity, education, employment, income, sexual orientation and route of infection. RESULTS: The group LTS were significantly higher than the ECOMP(LTS) group on emotional expression and depth processing. Depth processing mediated the relationship between emotional expression and long-term survival status. Depth processing was positively related to CD4+ cell number for women. Emotional expression was also significantly related to viral load (negatively) and to CD4+ cell number (positively) for women only. Interestingly, only depth processing (and not emotional expression) was related to medication adherence and to psychosocial variables (perceived stress and social support). CONCLUSIONS: Emotional expression and depth processing were related to long-term survival, however, depth processing was the mediator for this relationship and only depth processing was associated with medication adherence, perceived stress and social support. Our results underscore the importance of depth processing (and not just emotional expression) of traumatic experiences for people living with HIV/AIDS.

Acquired Immunodeficiency Syndrome↗

PubMed2025

Untargeted metabolomics reveals anion and organ-specific metabolic responses of salinity tolerance in willow.

Willows can alleviate soil salinisation while generating sustainable feedstock for biorefinery, yet the metabolomic adaptations underlying their tolerance remain poorly understood. Salix miyabeana was treated with two environmentally abundant salts, NaCl and Na2SO4, in a 12-week pot trial. Willows tolerated salts across all treatments (up to 9.1 dS m-1 soil ECe), maintaining biomass while selectively partitioning ions, confining Na+ to roots and accumulating Cl- andin the canopy and adapting to osmotic stress via reduced stomatal conductance. Untargeted metabolomics captured >5000 putative compounds, including 278 core willow metabolome compounds constitutively produced across organs. Across all treatments, salinity drove widespread metabolic reprogramming, altering 28% of the overall metabolome, with organ-tailored strategies. Comparing salt forms at equimolar sodium, shared differentially abundant metabolites were limited to 3% of the metabolome, representing the generalised salinity response, predominantly in roots. Anion-specific metabolomic responses were extensive. NaCl reduced carbohydrates and tricarboxylic acid cycle intermediates, suggesting potential carbon and energy resource pressure, and accumulated root structuring compounds, antioxidant flavonoids, and fatty acids. Na2SO4 salinity triggered accumulation of sulphur-containing larger peptides, suggesting excess sulphate incorporation leverages ion toxicity to produce specialised salt-tolerance-associated metabolites. This high-depth picture of the willow metabolome underscores the importance of capturing plant adaptations to salt stress at organ scale and considering ion-specific contributions to soil salinity.

Salix↗

PubMed1996

Intestinal adaptation following massive small bowel resection in the mouse.

BACKGROUND: Transgenic mice represent powerful tools for studying the role of genes and their expression under multiple conditions, and they may provide a unique model for studies of intestinal adaptation after massive small bowel resection (SBR). This study characterized a successful model for SBR and intestinal adaptation in the mouse. STUDY DESIGN: Sham operation (bowel transection with reanastomosis) or SBR was performed on male C57BL/6 mice. A solid or liquid diet, various sizes of monofilament suture for the anastomosis, and resection of 50 or 75 percent of the proximal small intestine were studied. In other studies, intestinal adaptation was characterized as changes in intestinal wet weight, DNA, protein, villus height, crypt depth, and crypt cell proliferation rates at 12 hours, 24 hours, three days, and one, two, and four weeks after 50 percent SBR. RESULTS: Survival was significantly improved with a liquid diet (8 percent compared with 88 percent; p < .001) and modestly improved by using the smallest suture for anastomosis (60 percent for 7-0 compared with 88 percent for 9-0; p = not significant). Mice did not tolerate more than 50 percent SBR (16 percent survival rate for 75 percent SBR compared with 85 percent survival rate for 50 percent SBR; p < .01). Small bowel resection augmented ileal wet weight, DNA and protein content, villus height, crypt depth, and crypt-cell proliferation rates. CONCLUSIONS: Provision of a liquid diet, using a small suture for anastomosis, and resection of no more than 50 percent of the proximal small intestine are important for survival. This model will permit researchers using transgenic mice to better understand critical genes during intestinal adaptation after SBR.

Adaptation, Biological↗

PubMed2006

An introduction to coil array design for parallel MRI.

The basic principles of radiofrequency coil array design for parallel MRI are described from both theoretical and practical perspectives. Because parallel MRI techniques rely on coil array sensitivities to provide spatial information about the sample, a careful choice of array design is essential. The concepts of coil array spatial encoding are first discussed from four qualitative perspectives. These qualitative descriptions include using coil arrays to emulate spatial harmonics, choosing coils with selective sensitivities to aliased pixels, using coil sensitivities with broad k-space reception profiles, and relying on detector coils to provide a set of generalized projections of the sample. This qualitative discussion is followed by a quantitative analysis of coil arrays, which is discussed in terms of the baseline SNR of the received images as well as the noise amplifications (g-factor) in the reconstructed data. The complications encountered during the experimental evaluation of coil array SNR are discussed, and solutions are proposed. A series of specific array designs are reviewed, with an emphasis on the general design considerations that motivate each approach. Finally, a set of special topics is discussed, which reflect issues that have become important, especially as arrays are being designed for more high-performance applications of parallel MRI. These topics include concerns about the depth penetration of arrays composed of small elements, the use of adaptive arrays for systems with limited receiver channels, the management of inductive coupling between array elements, and special considerations required at high field strengths. The fundamental limits of spatial encoding using coil arrays are discussed, with a primary emphasis on how the determination of these limits impacts the design of optimized arrays. This review is intended to provide insight into how arrays are currently used for parallel MRI and to place into context the new innovations that are to come.

Algorithms↗

PubMed1996

A combined stereotaxic adaptor and anaesthesia apparatus for microdialysis studies in small rodents.

Intracerebral microdialysis in the bank vole (Clethrionomys glareolus) challenges the accuracy and precision of the stereotaxic implantation technique because of the small brain size. In this paper, a miniaturized stereotaxic head holder is described that allows precise alignment of bone landmarks on the skull and prevents all movement after fixation by clamping the skull symmetrically at the os parietale and at the os nasale. In addition, the head holder is adapted for inhalation anaesthetic delivery in order to ensure stable anaesthetic depth over several hours. The system is not restricted to bank voles but can be readily applied to other small experimental animals, which could lead to a more widespread use of the microdialysis technique in mice.

Anesthesia↗

PubMed1996

The provision of female sterilization in São Paulo, Brazil: a study among low income women.

This paper examines some problems involved in the provision of female sterilization procedures in Brazil, mainly those concerned with the ways in which this operation is offered. Female sterilization provision is analysed by reference to the broader institutional context and from the client's perspectives. These themes are discussed in the light of some recent survey findings. A survey was carried out between March and July, 1992 in two selected poor areas of São Paulo Metropolitan Region. 3149 women were asked about contraceptive use including 407 sterilized women under 40 years old who were also interviewed about their adaptation to sterilization. Further information was also obtained through in-depth interviews with 15 sterilized women who regretted the operation. The findings highlight a complex network of interests and misunderstandings which shape the nature of choice of female sterilization by Brazilian low income women.

Adolescent↗