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Results for “depth adaptation”

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PubMed1989

Effect of brief, repeated hyperbaric exposures on susceptibility to nitrogen narcosis.

We investigated the effect of brief, repetitive exposures to 5.5 ATA (148 fsw) in a hyperbaric chamber on adaptation to nitrogen narcosis. A standing-steadiness task, which measures body sway, was administered to 2 groups of 3 chamber-qualified men at 5.5 ATA and 1.3 ATA [10 fsw (control)] on each of 12 successive days to determine if an initial performance decrement at 5.5 ATA would be ameliorated with time. Standing steadiness was significantly worse at 5.5 ATA than at 1.3 ATA across all 12 exposures. There were also changes in standing steadiness from day to day, but these changes occurred in both the test and control depths. There was no day-x-depth interaction that would have indicated that the initial performance decrement at 5.5 ATA was reduced with repetitive exposures. These results are taken as evidence that there is little or no behavioral adaptation to nitrogen narcosis in response to brief, repetitive exposures to narcosis-inducing hyperbaric air.

Adaptation, Physiological↗

PubMed1983

Tactile receptor discharge and mechanical properties of glabrous skin.

Current knowledge of the functional properties of mammalian cutaneous mechanoreceptors is reviewed with special reference to receptors associated with the glabrous skin of the raccoon and squirrel monkey hand. Four physiologically defined mechanoreceptor types are recognized: Pacinian afferents, rapidly adapting (RA), and slowly adapting type I (SAI), and slowly adapting type II (SAII). The SAI category is divided into moderately slowly adapting and very slowly adapting (VSA) types in terms of the duration of their response to a prolonged mechanical displacement of skin. Although both RA and SA units are capable of signaling displacement ramp velocity, the pattern of discharge during ramp stimulation may vary widely among units. SAI units also code the depth of skin displacement, but there is no best-fitting function describing the relationship. Static discharge is also markedly influenced by prior ramp velocity. Both raccoon and squirrel monkey VSA units show wide variation in the regularity of their discharge during static displacement. The rate of adaptation of SAI units is less when constant force stimuli are applied to the skin than when constant displacement stimuli are applied. This is partly attributable to mechanical properties of the skin. When either constant force or constant displacement stimuli are spaced too closely in time, there is a progressive (trial-to-trial) decrement in response rate, accounted for in part by failure of the skin to recover to its initial resting level.

Afferent Pathways↗

PubMed1994

Optimizing brachytherapy for locally advanced cervical cancer.

PURPOSE: No adequate high dose rate brachytherapy technique exists to cover all known tumor volume by using one type of applicator in patients presenting with a cervix carcinoma extending to the vaginal wall and the parametria. METHODS AND MATERIALS: We adapted the existing high dose rate applicator, existing of two ovoids and one intrauterine tube, to achieve adequate irradiation of the uterus, the parametria, and the vaginal wall in these patients. Using the optimization program of the Nucletron Planning System, isodose curves were obtained to apply a specified dose of 8.5 Gy at point A and at 5 mm depth of the vaginal wall by using a single applicator for both fractions. RESULTS: Fractionated high dose rate brachytherapy can be given with both higher dosimetric accuracy and more adequate irradiation of the vaginal and the parametrial tumor component after adapting the existing high dose rate applicator for brachytherapy in cervical cancer.

Brachytherapy↗

PubMed2002

Distribution of the H+/peptide transporter PepT1 in human intestine: up-regulated expression in the colonic mucosa of patients with short-bowel syndrome.

BACKGROUND: Intestinal adaptation after massive bowel resection in animal models is characterized by increased gut-mucosal growth and expression of nutrient transporters. Few data about these indexes exist in humans with short-bowel syndrome (SBS). OBJECTIVE: The objective was to compare small-bowel and colonic mucosal growth and expression of the peptide transporter PepT1 in adults with or without SBS. DESIGN: Mucosal biopsy specimens were obtained from the small bowel and colon of 33 control subjects with intact intestine and from 13 SBS patients dependent on parenteral nutrition because of chronic malabsorption. Gut-mucosal crypt depth, villus height, and villus width were measured, and expression of PepT1 was determined by Northern blotting, in situ hybridization, and immunohistochemistry. RESULTS: The indexes of small-bowel and colonic mucosal growth were not significantly different between the 2 groups. PepT1 expression was high in the apical region of duodenal, jejunal, and ileal villus epithelial cells; low in absorptive colonocytes; and not significantly different in the distal small intestine of the 2 groups. However, the abundance of PepT1 mRNA in the colon of SBS patients was more than 5-fold that in control subjects (P < 0.01). CONCLUSIONS: Gut adaptation in SBS patients does not appear to involve an increase in gut-mucosal crypt depth or villus size. PepT1 is abundant along the small-bowel brush border in humans; expression in the colon indicates that the large intestine has a mechanism for luminal di- and tripeptide transport. Up-regulation of colonic PepT1 in SBS may adaptively improve accrual of malabsorbed di- and tripeptides, independent of changes in the mucosal surface area.

Adult↗

PubMed1991

Adaptation of family members of brain-injured patients: perceptions of the hospitalization event.

Critical illness is a crisis for the afflicted individual as well as the family. This study was part of a larger study which undertook to add depth to the understanding of the family's experience following neurotrama and to add to the body of knowledge of family-focused nursing care. The focus of this portion of the study was the family's perception of their experience during the first week of the patient's hospitilization. Informal, unstructured interviews were conducted with ten families of patients who had been in a comatose state following a head injury which had occurred within two years of the study. Interviews were analyzed using generic-type and differentiation-type analysis. The family's perceptions of the hospitalization experience included: first hearing the news, first seeing the patient, the roles of nurse and physicians, the hospital culture, the family's physical needs, their time perspective, the ambiguity of the situation, belonging to a community of sufferers and the family's expectations for the patient's recovery. The findings of this study underline the importance of nurses as supporters of these families in their adaptation to a life-threatening event.

Adaptation, Psychological↗

PubMed2025

Temperature and Pressure Shaped the Evolution of Antifreeze Proteins in Polar and Deep Sea Zoarcoid Fishes.

Antifreeze proteins (AFPs) have enabled teleost fishes to repeatedly colonize polar seas. Four AFP types have convergently evolved in several fish lineages. AFPs inhibit ice crystal growth and lower tissue freezing point. In lineages with AFPs, species inhabiting colder environments may possess more AFP copies. Elucidating how differences in AFP copy number evolve is challenging due to the genes' tandem array structure and consequently poor resolution of these repetitive regions. Here, we explore the evolution of type III AFPs (AFP III) in the globally distributed suborder Zoarcoidei, leveraging six new long-read genome assemblies. Zoarcoidei has fewer genomic resources relative to other polar fish clades while it is one of the few groups of fishes adapted to both the Arctic and Southern Oceans. Combining these new assemblies with additional long-read genomes available for Zoarcoidei, we conducted a comprehensive phylogenetic test of AFP III evolution and modeled the effects of thermal habitat and depth on AFP III gene family evolution. We confirm a single origin of AFP III via neofunctionalization of the enzyme sialic acid synthase B. We also show that AFP copy number increased under low temperature but decreased with depth, potentially because pressure lowers freezing point. Associations between the environment and AFP III copy number were driven by duplications of paralogs that were translocated out of the ancestral locus at which AFP III arose. Our results reveal novel environmental effects on AFP evolution and demonstrate the value of high-quality genomic resources for studying how structural genomic variation shapes convergent adaptation.

Animals↗

PubMed1989

Dosimetric evaluation of a variable energy superficial X-ray machine with applications for endocavitary radiotherapy techniques.

This investigation presents the beam characteristics of a newly-marketed variable energy superficial X ray machine for radiotherapy. The X ray system hardware, including a high voltage generator, and console software allow for nine independent operator-selected X ray beams from 10-150 kVp. Filament current values are also independently variable; 1.0-13.0 mA for 90-150 kVp, and 1.0-30.0 mA for 10-90 kVp. The HVL's, effective energies, and radiation outputs for the nine combinations of kVp and mA are presented. In addition, percentage depth dose and beam uniformity results are presented as a function of cone size. Radiation output stability and reproducibility results are included. Discussion of adaptation of this X ray system to the Papillon technique for the treatment of rectal cancers is presented.

Brachytherapy↗

PubMed1994

Diver monitoring by ultrasonic digital data telemetry.

A through-water ultrasonic data telemetry system using burst-mode frequency shift keying (FSK) is described. The system can be adapted for the transmission of data from various sensors, but it has been designed principally for monitoring the respiratory rate, heart rate, temperature and depth of a free-swimming diver over a range of up to 300 metres. This application requires the transmission of low rate digital signals through water from a moving source to a receiver that is either stationary or moving.

Amplifiers, Electronic↗

PubMed2006

Comparison of long-term numerical and experimental total knee replacement wear during simulated gait loading.

Pre-clinical experimental wear testing of total knee replacement (TKR) components is an invaluable tool for evaluating new implant designs and materials. However, wear testing can be a lengthy and expensive process, and hence parametric studies evaluating the effects of geometric, loading, or alignment perturbations may at times be cost-prohibitive. The objectives of this study were to develop an adaptive FE method capable of simulating wear of a polyethylene tibial insert and to compare predicted kinematics, weight loss due to wear, and wear depth contours to results from a force-controlled experimental knee simulator. Finite element-based computational wear predictions were performed to 5 million gait cycles using both force- and displacement-controlled inputs. The displacement-controlled inputs, by accurately matching the experimental tibiofemoral motion, provided an evaluation of the simple wear theory. The force-controlled inputs provided an evaluation of the overall numerical method by simultaneously predicting both kinematics and wear. Analysis of the predicted wear convergence behavior indicated that 10 iterations, each representing 500,000 gait cycles, were required to achieve numerical accuracy. Using a wear factor estimated from the literature, the predicted kinematics, polyethylene wear contours, and weight loss were in reasonable agreement with the experimental data, particularly for the stance phase of gait. Although further development of the simplified wear theory is important, the initial predictions are encouraging for future use in design phase implant evaluation. In contrast to the experimental testing which occurred over approximately 2 months, computational wear predictions required only 2h.

Arthroplasty, Replacement, Knee↗

PubMed2026

Neurocorrelates of nocturnal enuresis in pre-adolescent children.

INTRODUCTION: Nocturnal enuresis (NE) is a common neurodevelopmental condition, yet its underlying neural mechanisms remain unclear. This study leverages the large-scale Adolescent Brain Cognitive Development (ABCD) dataset to identify structural and functional brain correlates associated with active symptoms and the resolution of bedwetting. METHODS: Using cross-sectional data from 3472 participants aged 9-10 years, children were categorized into three groups: active nocturnal enuresis (ANE, n = 225), history of nocturnal enuresis (HNE, n = 1171), and healthy control groups (CG, n = 2076). Multimodal neuroimaging protocol evaluated macrostructural properties via structural MRI (sMRI), microstructural white matter integrity via diffusion MRI (dMRI), and functional connectivity via resting-state fMRI (fMRI). Group differences were evaluated using linear models within an ANCOVA framework, adjusting for intracranial volume and handedness with False Discovery Rate (FDR) correction. RESULTS: Compared to controls, the ANE group exhibited a significant volume deficit in the right caudate, decreased sulcal depth in the left insula, and lower internal correlation within the Cingulo-Opercular Network (CON). Conversely, the dry HNE group demonstrated significant structural adaptations, including bilaterally larger putamen volumes and increased right caudate volume compared to the ANE group. The HNE group also showed increased microstructural density (decreased mean diffusivity) in the bilateral hippocampus and an increased cortical surface area in the left insula. Both NE groups demonstrated persistently reduced functional coupling within the CON. CONCLUSIONS: Nocturnal enuresis appears to be associated with a potential complex central signaling deficits. Reduced internal correlation within the CON across both active and former bedwetters indicates a potential for impairment in processing internal homeostatic bladder signals during sleep.

Humans↗

PubMedDate not supplied

Retinal bipolar cells: contrast encoding for sinusoidal modulation and steps of luminance contrast.

Contrast encoding for sinusoidal modulations of luminance contrast was investigated by intracellular recording in the intact salamander retina. In what appears to be the first study of this kind for vertebrate bipolar cells, responses of the central receptive-field mechanism of cone-driven cells to modulation of 3 Hz were analyzed quantitatively via both signal averaging and a Fast Fourier Transform (FFT) while the retina was light adapted to 20 cd/m2. Depolarizing and hyperpolarizing bipolar cells showed very similar encoding. Both responded with sinusoidal waveforms whose amplitude varied linearly with modulation depths ranging up to 7-8%. The slope of the modulation/response curve was very steep in this range. Thus, the contrast gain was high, reaching values of 6-7, and the half-maximal response was achieved at modulations of 9% or less. At modulations above approximately 15%, the responses typically showed strong compressive nonlinearity and the waveform was increasingly distorted. At maximum modulation, the higher harmonics of the FFT constituted about 30% of the amplitude of the fundamental. Measurements were also made for cones and horizontal cells. Both cell types showed predominantly linear responses and low contrast gain, in marked contrast to bipolar cells. These results suggest that the high contrast gain and strong nonlinearity of bipolar cells largely arise postsynaptic to cone transmitter release. Further experiments were performed to compare responses to contrast steps versus those to sinusoidal modulation. In the linear range, we show that the contrast gains of cones and horizontal cells are low and virtually identical for both steps and sinusoidal modulations. In bipolar cells, on the other hand, the contrast gain is about two times greater for steps than that for the 3-Hz sine waves. These results suggest that mechanisms intrinsic to bipolar cells act like a high-pass filter with a short time constant to selectively emphasize contrast transients over slower changes in contrast.

Ambystoma↗

PubMed2003

Spectroscopic and photochemical characterization of a deep ocean proteorhodopsin.

A second group of proteorhodopsin-encoding genes (blue-absorbing proteorhodopsin, BPR) differing by 20-30% in predicted primary structure from the first-discovered green-absorbing (GPR) group has been detected in picoplankton from Hawaiian deep sea water. Here we compare BPR and GPR absorption spectra, photochemical reactions, and proton transport activity. The photochemical reaction cycle of Hawaiian deep ocean BPR in cells is 10-fold slower than that of GPR with very low accumulation of a deprotonated Schiff base intermediate in cells and exhibits mechanistic differences, some of which are due to its glutamine residue rather than leucine at position 105. In contrast to GPR and other characterized microbial rhodopsins, spectral titrations of BPR indicate that a second titratable group, in addition to the retinylidene Schiff base counterion Asp-97, modulates the absorption spectrum near neutral pH. Mutant analysis confirms that Asp-97 and Glu-108 are proton acceptor and proton donor, respectively, in retinylidene Schiff base proton transfer reactions during the BPR photocycle as previously shown for GPR, but BPR contains an alternative acceptor evident in its D97N mutant, possibly the same as the second titratable group modulating the absorption spectrum. BPR, similar to GPR, carries out outward light-driven proton transport in Escherichia coli vesicles but with a reduced translocation rate attributable to its slower photocycle. In energized E. coli cells at physiological pH, the net effect of BPR photocycling is to generate proton currents dominated by a triggered proton influx, rather than efflux as observed with GPR-containing cells. Reversal of the proton current with the K+-ionophore valinomycin supports that the influx is because of voltage-gated channels in the E. coli cell membrane. These observations demonstrate diversity in photochemistry and mechanism among proteorhodopsins. Calculations of photon fluence rates at different ocean depths show that the difference in photocycle rates between GPR and BPR as well as their different absorption maxima may be explained as an adaptation to the different light intensities available in their respective marine environments. Finally, the results raise the possibility of regulatory (i.e. sensory) rather than energy harvesting functions of some members of the proteorhodopsin family.

Escherichia coli↗

PubMed2000

Rapid cooling aborts seizure-like activity in rodent hippocampal-entorhinal slices.

PURPOSE: As a preliminary step in the development of an implantable Peltier device to abort focal neocortical seizures in vivo, we have examined the effect of rapid cooling on seizures in rodent hippocampal-entorhinal slices. METHODS: Seizure-like discharges were induced by exposing the slices to extracellular saline containing 4-aminopyridine (50 micromol/L). RESULTS: When we manually activated a Peltier device that was in direct contact with the slice, seizures terminated within seconds of the onset of cooling, sometimes preceding a detectable decrease in temperature measured near the top of the slice. However, activation of the Peltier device did not stop seizures when slices were no longer in direct physical contact with the device, indicating that this was not a field effect. When cooling was shut off and temperature returned to 33 degrees C, bursting sometimes returned, but a longer-term suppressive effect on seizure activity could be observed. In two of our experiments, a custom computer program automatically detected seizure discharges and triggered a transistor-transistor logic pulse to activate the Peltier device. In these experiments, the Peltier device automatically terminated the slice bursting in less than 4 seconds. When the Peltier device was placed in contact with the normal, exposed cortex of a newborn pig, we found that the cortical temperature decreased rapidly from 36 degrees C to as low as 26 degrees C at a depth of 1.7 mm below the cooling unit. CONCLUSIONS: These experiments show that local cooling may rapidly terminate focal paroxysmal discharges and might be adapted for clinical practice.

Animals↗

PubMed1990

Modulith SL 10/20--experimental introduction and first clinical experience with a new interdisciplinary lithotriptor.

More than 20 second-generation lithotriptors have been introduced for extracorporeal shock-wave lithotripsy. Despite great technical progress, each machine still has its specific short-comings. In cooperation, Storz Medical (Kreuzlingen, Switzerland) and the Department of Urology (Klinikum Mannheim, FRG), have developed a new lithotriptor designed to overcome these drawbacks. Energy source: Electromagnetic cylinder with paraboloid reflector (40 cm) for focusing, providing a wide range of pressure (190-1,000 bar) and a focal zone of 28 x 6 mm. The focal depth is maximally 15 cm. Coupling and positioning: Water cushion with patient lying on a specially designed 'acoustic cradle' consisting of an impedance-adapted foil. This is integrated in either a manually or automatically operated table. Localization: Coaxial ultrasound probe for real-time scanning and integrated C arm with pulsed fluoroscopy using a virtual focus (moved along x-axis) for stone localization. In 1989, we commenced with the first treatment based on our own in vitro and in vivo studies to determine the range of energy required for safe application. We treated 137 stones (100 caliceal, 19 pelvic and 18 ureteral) in 88 patients. The mean generator voltage was 16 kV (10-18 kV). Successful disintegration was achieved in 83 patients (95%) employing an average of 2,359 impulses (940-3,500). Thirteen percent of the treatments were performed without any anesthesia on lower generator voltage (10-15 kV), whereas the majority of calculi were treated under intravenous analgesia. The 5 failure cases included 2 stones in a caliceal diverticulum. Moreover, 12 patients with biliary calculi (11 gallstones and 1 bile duct stone) were successfully treated; 1 of these cases required a second treatment session.

Animals↗

PubMed1989

Inhibitors of sterol synthesis. Morphological studies in rats after dietary administration of 5 alpha-cholest-8(14)-en-3 beta-ol-15-one, a potent hypocholesterolemic compound.

The morphological effects of short-term (9 days) dietary administration (0.1% in a laboratory chow diet) of 5 alpha-cholest-8(14)-en-3 beta-ol-15-one, a novel regulator of cholesterol metabolism with significant hypocholesterolemic activity, has been studied in young male rats. Control animals included rats fed the basal diet ad libitum and a series of rats pair-fed to the individual experimental animals. At the time of necropsy, the morphological changes in rats which have been observed in rats following treatment with other absorbable hypolipidemic agents (myeloid bodies with triparanol, increased peroxisomes with clofibrate, and proliferation of smooth endoplasmic reticulum with compactin and mevinolin) were not apparent on ultrastructural examination of livers of rats treated with the 15-ketosterol. Two changes were observed in the rats fed the 15-ketosterol: a decrease in adipose tissue and enlargement of the small intestine. Diminished fat was also noted in the pair-fed controls and was presumably due to decreased food consumption. The intestines of rats fed the 15-ketosterol were morphometrically most enlarged in the jejunal region. Morphologically, this increase was distinguished by increased depth of crypts of Lieberkuhn and pseudostratification of epithelium at the base of the villi. These changes were qualitatively and quantitatively similar to the adaptive changes reported in the rat after resection of small bowel or following intestinal bypass (segment of bowel remaining in continuity). The morphological changes induced in the rat by administration of the 15-ketosterol were not observed in 4 baboons which received the compound orally at doses of 50, 75, or 100 mg per kilogram of body weight for up to 3 months.

Animals↗

PubMed2005

New insights into the tonoplast architecture of plant vacuoles and vacuolar dynamics during osmotic stress.

BACKGROUND: The vegetative plant vacuole occupies >90% of the volume in mature plant cells. Vacuoles play fundamental roles in adjusting cellular homeostasis and allowing cell growth. The composition of the vacuole and the regulation of its volume depend on the coordinated activities of the transporters and channels localized in the membrane (named tonoplast) surrounding the vacuole. While the tonoplast protein complexes are well studied, the tonoplast itself is less well described. To extend our knowledge of how the vacuole folds inside the plant cell, we present three-dimensional reconstructions of vacuoles from tobacco suspension cells expressing the tonoplast aquaporin fusion gene BobTIP26-1::gfp. RESULTS: 3-D reconstruction of the cell vacuole made possible an accurate analysis of large spanning folds of the vacuolar membrane under both normal and stressed conditions, and suggested interactions between surrounding plastids. Dynamic, high resolution 3-D pictures of the vacuole in tobacco suspension cells monitored under different growth conditions provide additional details about vacuolar architecture. The GFP-decorated vacuole is a single continuous compartment transected by tubular-like transvacuolar strands and large membrane surfaces. Cell culture under osmotic stress led to a complex vacuolar network with an increased tonoplast surface area. In-depth 3-D realistic inspections showed that the unity of the vacuole is maintained during acclimation to osmotic stress. Vacuolar unity exhibited during stress adaptation, coupled with the intimate associations of vacuoles with other organelles, suggests a physiological role for the vacuole in metabolism, and communication between the vacuole and organelles, respectively, in plant cells. Desiccation stress ensuing from PEG treatment generates "double" membrane structures closely linked to the tonoplast within the vacuole. These membrane structures may serve as membrane reservoirs for membrane reversion when cells are reintroduced to normal growth conditions. CONCLUSION: 3-D processing of a GFP-labeled tonoplast provides compelling visual constructions of the plant cell vacuole and elaborates on the nature of tonoplast folding and architecture. Furthermore, these methods allow real-time determination of membrane rearrangements during stresses.

Aquaporins↗

PubMedDate not supplied

Development of inductive heating equipment using an inductive aperture-type applicator.

We designed an inductive aperture-type applicator, IATA, consisting of a one-turn, square, column-like coil made of a metal strip. In experiments using a phantom, this applicator was seen to have the following characteristics: (1) it does not excessively heat the fat layer; (2) deep portions can be heated effectively; (3) heat can be applied to the subject, without contact with the applicator; (4) excessive generation of heat does not occur in parts of tissue near the edge of the aperture; (5) size of the aperture can be changed for adaptation to size of the site to be heated; (6) the aperture can be modified to fit the shape of the subject and the depth of penetration is influenced by size of the subject being heated; (7) the applicator can be driven at an arbitrary frequency; (8) efficiency of heat generation to the input power is low. The inductive heating equipment, 'Inductron', which we have developed possesses the necessary requirements for adequate clinical application.

Adipose Tissue↗

PubMed1999

Aging and space flight: findings from the University of Pittsburgh.

For more than a decade, the Sleep and Chronobiology Center (SCC) at the University of Pittsburgh has received funding from the National Institute on Aging (NIA), the National Institute of Mental Health (NIMH) and the National Aeronautics and Space Administration (NASA) in order to study the sleep and circadian rhythms of healthy older people, as well as the sleep and circadian rhythms of astronauts and cosmonauts. We have always been struck by the strong synergism between the two endeavors. What happens to the sleep and circadian rhythms of people removed from the terrestrial time cues of Earth is in many ways similar to what happens to people who are advancing in years. Most obviously, sleep is shorter and sleep depth is reduced, but there are also more subtle similarities between the two situations, both in circadian rhythms and in sleep, and in the adaptive strategies needed to enhance 24h zeitgebers.

Adult↗