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Results for “depth adaptation”

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At least 307 records · Page 17Linked to original sources

PubMed1999

Ecological parallelism and cryptic species in the genus Ophiothrix derived from mitochondrial DNA sequences.

We addressed the long-standing problem of species assignment of two nominal species of the genus Ophiothrix (Echinodermata, Ophiuroidea) by phylogenetic analysis of a segment of the mitochondrial 16S rDNA. Our phylogeny identified two distinct mitochondrial lineages that do not correspond to the present species assignments. Individuals of the endemic Mediterranean species O. quinquemaculata were clustered with individuals of O. fragilis in both mitochondrial lineages. We thus suggest that these taxa are not biological species but ecotypes. Differences between the two ecotypes in morphological and physiological characteristics may be explained by adaptation to environmental conditions at different water depths. Despite the observed ecomorphological variability within each of the two major mitochondrial lineages, the large genetic distance (9.0-12.0%) between them does suggest the existence of two distinct biological species. Their reproductive isolation could result from differences in reproductive strategy rather than by ecological and/or morphological differentiation.

Animals↗

PubMed2005

What the paediatricians need--the launch of paediatric research in Europe.

UNLABELLED: Most parents and many paediatricians are not aware that medicines for children are often not tested, labelled, or approved for their prescribed use. In 1997, the Food and Drug Administration developed incentives for pharmaceutical companies to perform paediatric research in medications. The European Commission brought out its proposal for paediatric incentives after in-depth internal reflection. Now it should be adapted quickly to boost pharmaceutical paediatric research in the EU as soon as possible. CONCLUSION: The proposal must be balanced and aware that both incentives and requirements are mandatory in order to maintain and stimulate paediatric research on medicines in Europe.

Child↗

PubMed1981

Quantitation of lipid profiles from isolated serum lipoproteins using small volumes of human serum.

Methodology is described that isolates the individual serum lipoproteins, VLDL, LDL and HDL and quantitates the free cholesterol, esterified cholesterol, triglycerides and phospholipid classes in each fraction using 2-3 mL of serum. The determination of the methyl esters of fatty acids from the various lipid classes is described. The lipoproteins are isolated by non-linear density ultracentrifugation using 1 mL of serum per swinging bucket. The lipids are obtained by solvent extraction. The cholesterol, cholesterol esters and triglycerides are separated by TLC using a petroleum ether:diethyl ether system and the phospholipids are separated using a chloroform:methanol system. All lipid classes are quantitatively determined and recovery data are presented. Analysis of the fatty acid profiles of the lipid classes using GLC is described. The methodology can be adapted to partial determination if in-depth studies are not required.

Aged↗

PubMed1999

Patient management and decision making in complete denture fabrication using a duplicate denture procedure: a clinical report.

A patient may have difficulty adapting to a new prosthesis for either physical or psychological reasons. This article describes a procedure for duplicating an existing denture and gives the practitioner an alternative to the traditional denture fabrication techniques. The duplicated denture fabrication technique minimizes the changes to the new denture, making it easier for the patient to adapt to new dentures. However, in-depth communication with the patient is necessary for successful denture therapy.

Aged↗

PubMedDate not supplied

Mechanisms counteracting swelling in brain cells during hyponatremia.

Water gain in the brain consequent to hyponatremia is counteracted by mechanisms that initially include a compensatory displacement of liquid from the interstitial space to cerebrospinal fluid and systemic circulation and subsequently an active reduction in cell water accomplished by extrusion of intracellular osmolytes to reach osmotic equilibrium. Potassium (K+), chloride (Cl-), amino acids, polyalcohols, and methylamines all contribute to volume regulation, with a major contribution of ions at the early phase and of organic osmolytes at the late phase of the regulatory process. Experimental models in vitro show that osmolyte fluxes occur via leak pathways for organic osmolytes and separate channels for Cl- and K+. Osmotransduction signaling cascades for Cl- and taurine efflux pathways involve tyrosine kinases and phosphoinositide kinases, while Ca2+ and serine-threonine kinases modulate K+ pathways. In-depth knowledge of the cellular and molecular adaptive mechanisms of brain cells during hyponatremia contributes to a better understanding of the associated complications, including the risks of inappropriate correction of the hyponatremic condition.

Animals↗

PubMed2002

Fish at high pressure: a hundred year history.

Two main periods can be considered in the history of fish metabolism under pressure. The first period (roughly from 1870 to 1970) was mainly descriptive: survival times and behavior were studied and some authors described an increase in oxygen consumption under pressure; later, the counteracting effects of high temperature on pressure were mentioned. The second period (from 1970 onwards) was more integrative and two major ways were explored. The first was to use shallow-water fish, experimentally exposed to hydrostatic pressure, which can induce a metabolic state resembling histotoxic hypoxia. The second way was to use deep-living fish which have, when compared to surface fish, muscle enzymes with higher structural stability, lower activity (in relationship with habitat depth) and kinetics that are less sensitive to pressure increase. Using this approach, it was also shown that muscle composition and function were somewhat different at depth and that deep fish are well adapted to pressure partly by maintaining membrane fluidity (homeoviscous theory). Since about 1990, the two above-mentioned approaches have still been pursued but by fewer researchers. Studies on deep-living fish are mainly concerned with enzyme kinetics whereas shallow water fish are used mainly for cellular energetic studies. Regarding this topic, it has been shown that yellow freshwater eels are able to acclimate to high-pressure effects, by optimizing membrane fluidity and composition (as achieved by deep-living fish), by improving oxidative phosphorylation (increase of P/O ratio) and the glycolytic pathway.

Adaptation, Physiological↗

PubMedDate not supplied

Data collection methods in prospective economic evaluations: how accurate are the results?

OBJECTIVES: Often in economic evaluations a division is made between those studies that have a high level of accuracy versus those that are easily generalized. This interstudy dichotomy is often translated into prospective, randomized controlled trials with high internal validity and observational and modeling studies with a high level of external validity. This article challenges this conventional view and examines intrastudy effects on validity. METHOD: A review and summary of the literature was conducted in order to assess the impact that data collection strategies will have on internal validity. Two scenario models were created in order to gain a preliminary understanding of the magnitude of the problem. RESULTS: Data collection strategies have an impact on the level of internal validity found in an economic evaluation. Comparisons of studies that are prospective in nature is misleading as data collection strategy can lead to different resource and cost estimates even when all other relevant factors are similar. It is possible to shift and improve the level of validity by combining different collection methods. CONCLUSIONS: Instead of viewing internal and external validity as polar opposites, validity should be considered in terms of a continuum within a particular study. The use of proxies to collect resource utilization estimates, the reliance on patient self-reported data, and the method of collecting this type of data all impact the validity of study results. National guidelines for the economic evaluation of agents and devices should consider this issue in more depth, and existing evidence rankings should be adapted to be more appropriate to pharmacoeconomic studies.

Journal Article↗

PubMed1996

Cytokinetic and structural responses of the rat small intestine to riboflavin depletion.

The impaired absorption and metabolism of Fe seen in riboflavin deficiency is attributed, at least in part, to a hyperproliferative response in the small intestine, associated with an altered morphology. Studies were conducted in female weanling Wistar rats to explore further the effect of riboflavin deficiency on the cytokinetics and structure of the small intestine. Feeding a riboflavin-deficient diet for 8 weeks from weaning resulted in a significantly lower villus number, a significant increase in villus length and an increased rate of transit of enterocytes along the villi, compared with weight-matched controls. A second experiment focused on the 3 weeks after weaning and showed that riboflavin deficiency inhibits the increase in villus number observed in control animals over this period. We suggest that riboflavin deficiency induced at weaning impairs the normal increase in villus number and that prolonged deficiency leads to an adaptive increase in length of villi and depth of crypts.

Analysis of Variance↗

PubMedDate not supplied

Correcting interperspective aliasing in autostereoscopic displays.

An image presented on an autostereoscopic system should not contain discontinuities between adjacent views. A viewer should experience a continuous scene when moving from one view to the next. If corresponding points in two perspectives do not spatially abut, a viewer will experience jumps in the scene. This is known as interperspective aliasing. Interperspective aliasing is caused by object features far away from the stereoscopic screen being too small, which results in visual artifacts. By modeling a 3D point as a defocused image point, we can adapt Fourier analysis to devise a depth-dependent filter kernel that allows filtering of a stereoscopic 3D image. For synthetic 3D data, we use a simpler approach, which is to smear the data by a distance proportional to its depth.

Algorithms↗

PubMedDate not supplied

The effect of enteral glutamine deprivation and supplementation on the structure of rat small-intestine mucosa during a systemic injury response.

BACKGROUND: An aseptic model of tissue injury (the induction of abscesses by subcutaneous injections of turpentine) was used to examine the proposal that changes in glutamine metabolism lead to structural damage in the epithelium of the small intestine during the systemic response to injury and to investigate the role of dietary glutamine in the maintenance of mucosal structure in the small intestine of control and injured rats. METHODS: Glutamine-free and glutamine-rich (3.6% glutamine by weight) diets were fed to rats before and during an acute-phase response to injury. Pair-fed groups of animals enabled an independent assessment to be made of the effects of the associated dietary restriction on the mucosal epithelium. RESULTS: Adaptive increases in villus height and crypt depth were seen in response to 4 days of feeding of the glutamine diet. Pair-feeding (30% dietary restriction) of either diet induced mucosal atrophy (loss of wet weight and nitrogen) without changes in villus height or crypt depth in the proximal tercile of the small intestine. Systemic injury, however, had no effect on the weight or nitrogen content of the mucosa (relative to pair-feeding). Gross histologic appearance, villus height, and crypt depth were also unchanged by the response to injury. CONCLUSIONS: The study provided no evidence to support the proposal that alterations in the availability of dietary glutamine during systemic injury (induced by turpentine injections) lead to structural damage to the epithelium.

Animals↗

PubMed1979

Microleakage of amalgam restorations with high-copper content.

An in vitro study of microleakage of the margins of Class II restorations of several high-copper-content amalgams found that in general, leakage increased between 24 hours and a month, but decreased below the 24-hour values after six months; there were some differences in leakage among the products at 24 hours, but not aftersix months: the depth of leakage was not correlated with adaptation of the cavosurface margins; and the high-copper-content amalgams were similar to the conventional composition amalgam tested in regard to microleakage.

Copper↗

PubMed2004

Analgesia and sedation in critically ill patients.

In critically ill patients, adequate analgesia and sedation increase comfort, reduce stress response and facilitate diagnostic and therapeutic procedures. Analgesia and sedation may also have a beneficial impact on morbidity, particularly by reducing pulmonary complications such as atelectasis and pneumonia, and delirium or agitation with subsequent accidental extubation. The method and depth of analgesia and sedation should be adapted to the needs of the individual patient. While evaluation of analgesia and sedation is important, technical tools for assessment are generally unreliable. Accordingly, management of these patients is best guided by simple clinical scores, though there is no consensus on how frequently pain and sedation should be evaluated. While there is some degree of consensus on what constitutes an acceptable level of pain relief, the same is not true of sedation, with the attendant risk of over-sedation. Analgesia and sedation are performed chiefly by pharmacological means. The first step includes adequate analgesia, usually with opioids. There is no evidence of a difference in efficacy between opioids as far as clinically relevant outcomes are concerned. However, there is some evidence that more sophisticated methods of opioid administration, such as patient-controlled analgesia, may improve pulmonary outcomes. In Europe, midazolam and propofol are most frequently used for sedation of the critically ill. Regular evaluation of the effect of these drugs and subsequent adaptation of dosage are more important than the choice of specific analgesics and hypnotics. Implementation of guidelines for rational analgesia and sedation would help to reduce patients' length of stay in the intensive care unit.

Algorithms↗

PubMed1999

Physical and occupational therapy.

Occupational and physical therapists are concerned with an infant's ability to perform in object play and manipulation, self-care, mobility, and social function. Within the realm of child psychiatry, occupational and physical therapists contribute to a comprehensive assessment by providing in-depth neuromotor, sensory processing, and functional or adaptive skill analyses. The three theoretic approaches presented in this article represent the current trends within infant and young child assessment in the fields of occupational and physical therapy. In the past, therapists primarily used neuromotor or developmental assessments. Although these assessments have proven to be adequate for discrimination between children with developmental delays and those who are typically developing, they have not been as useful in documentation of progress in treatment or in providing an understanding of qualitative aspects of movement. Qualitative assessments that are more sensitive to change and to the complexity of functional skills have grown with the development of more sophisticated early-intervention strategies. Assessments based on dynamic systems theory allow therapists to quantify abilities, document subtle changes over time, and provide information on the qualitative aspects of movement. Therapists, however, continue to regularly employ assessments from multiple theoretic approaches to complete comprehensive evaluations.

Child, Preschool↗

PubMed2004

Elucidation of cardiac physiology in aortic valve replacement: what should we know?

Over the past 50 years, aortic valve surgery has achieved enormous progress towards restoring durable and physiological performance of aortic valve prostheses, physiological coronary circulation, and thus the normal structure and function of the left ventricle. Throughout the entire history of aortic valve surgery, it has been clear that interactions between surgeons and physicians have not only led to improvements in operative techniques and results, but have also facilitated a better understanding of left ventricupathophysiology underlying the surgery. Embracing genetic technology with classical cardiac physiology will create a new platform to yield a more in-depth understanding of the nature of myocardial adaptation to pressure and volume changes associated with valve disease, and myocardial responses to heart valve surgery. Ultimately, this new knowledge will have a significant impact on heart valve surgery and cardiac medicine.

Aortic Valve↗

PubMed1991

High altitude dives from 7000 to 14,200 feet in the Himalayas.

Indian Navy divers carried out no-decompression dives at altitudes of 7000 to 14,200 ft (2134-4328 m) in the Nilgiris and Himalayas from May to July 1988. Seventy-eight dives on air and 22 dives on oxygen were carried out at various altitudes. The final dives were at Lake Pangong Tso (4328 m) in Ladakh, Himalayas, to a maximum of 140 feet of sea water (fsw) [42.6 meters of sea water (msw)] equivalent ocean depth in minimum water temperature of 2 degrees C. Oxygen diving at 14,200 ft (4328 m) was not successful. Aspects considered were altitude adaptation, diminished air pressure diving, hypothermia, and remote area survival. Depths at altitude were converted to depths at sea level and were applied to the Royal Navy air tables. Altitude-related manifestations, hypoxia, hypothermia, suspected oxygen toxicity, and equipment failure were observed. It is concluded that stress is due to effects of altitude and cold on man and equipment, as well as changes in diving procedures when diving at high altitudes. Equivalent air depths when applied to Royal Navy tables could be considered a safe method for diving at altitudes.

Acclimatization↗

PubMed2002

Communication arising. Is coral bleaching really adaptive?

From an experiment in which corals are transplanted between two depths on a Panamanian coral reef, Baker infers that bleaching may sometimes help reef corals to survive environmental change. Although Baker's results hint at further mechanisms by which reef-building corals may acclimatize to changing light conditions, we do not consider that the evidence supports his inference.

Adaptation, Physiological↗

PubMed2002

Adapting to psychiatric disability and needs for home- and community-based care.

The objective of the study was to describe adaptation strategies and use of formal and informal support by individuals with psychiatric disabilities, to delineate remaining needs, and to determine how home- and community-based services might address those needs. Using in-depth interviews and structured questionnaires, we examined functional status, adaptation, and needs for home- and community-based care among 33 severely mentally ill members of a large health maintenance organization. Despite success in community living, participants had significant functional deficits (physical and emotional), relied heavily on only one or two key informal caregivers, and often needed significant support from mental health professionals. Limited numbers of caregivers and social isolation placed participants at risk of negative outcomes if informal support resources were to be lost. Home- and community-based care interventions that attempt to increase informal support networks and provide instrumental help (cooking, cleaning, transport) on short notice during flare-ups could augment existing (but limited) informal caregiving, help severely mentally ill individuals remain independent, and reduce the likelihood that loss of an informal caregiver would result in unwanted outcomes.

Activities of Daily Living↗

PubMed1999

Real-time adaptive functional MRI.

Adaptively limiting image acquisition to areas of interest will allow more efficient data acquisition time for in-depth characterization of areas of brain activation. We designed and implemented an adaptive image acquisition scheme that uses a multiresolution-based strategy to zoom into the regions of cortical activity. Real-time pulse prescription and data processing capabilities were combined with spatially selective radiofrequency encoding. The method was successfully demonstrated in volunteers performing simple sensorimotor paradigms for simultaneous activation of primary motor and cerebellar areas. We believe that real-time adaptation of spatial and temporal sampling to task-related changes will increase the efficiency and flexibility of functional mapping experiments. Contrast-to-noise analysis in selected regions-of-interest was performed to quantitatively assess the multiresolution adaptive approach.

Adult↗