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PubMed1998

An adaptive noise reduction stethoscope for auscultation in high noise environments.

Auscultation of lung sounds in patient transport vehicles such as an ambulance or aircraft is unachievable because of high ambient noise levels. Aircraft noise levels of 90-100 dB SPL are common, while lung sounds have been measured in the 22-30 dB SPL range in free space and 65-70 dB SPL within a stethoscope coupler. Also, the bandwidth of lung sounds and vehicle noise typically has significant overlap, limiting the utility of traditional band-pass filtering. In this study, a passively shielded stethoscope coupler that contains one microphone to measure the (noise-corrupted) lung sound and another to measure the ambient noise was constructed. Lung sound measurements were made on a healthy subject in a simulated USAF C-130 aircraft environment within an acoustic chamber at noise levels ranging from 80 to 100 dB SPL. Adaptive filtering schemes using a least-mean-squares (LMS) and a normalized least-mean-squares (NLMS) approach were employed to extract the lung sounds from the noise-corrupted signal. Approximately 15 dB of noise reduction over the 100-600 Hz frequency range was achieved with the LMS algorithm, with the more complex NLMS algorithm providing faster convergence and up to 5 dB of additional noise reduction. These findings indicate that a combination of active and passive noise reduction can be used to measure lung sounds in high noise environments.

Auscultation↗

PubMed1996

Oxygen sensing and molecular adaptation to hypoxia.

This review focuses on the molecular stratagems utilized by bacteria, yeast, and mammals in their adaptation to hypoxia. Among this broad range of organisms, changes in oxygen tension appear to be sensed by heme proteins, with subsequent transfer of electrons along a signal transduction pathway which may depend on reactive oxygen species. These heme-based sensors are generally two-domain proteins. Some are hemokinases, while others are flavohemoproteins [flavohemoglobins and NAD(P)H oxidases]. Hypoxia-dependent kinase activation of transcription factors in nitrogen-fixing bacteria bears a striking analogy to the phosphorylation of hypoxia inducible factor-1 (HIF-1) in mammalian cells. Moreover, redox chemistry appears to play a critical role both in the trans-activation of oxygen-responsive genes in unicellular organisms as well as in the activation of HIF-1. In yeast and bacteria, regulatory operons coordinate expression of genes responsible for adaptive responses to hypoxia and hyperoxia. Similarly, in mammals, combinatorial interactions of HIF-1 with other identified transcription factors are required for the hypoxic induction of physiologically important genes.

Animals↗

PubMed2005

Phagocytosis: the convoluted way from nutrition to adaptive immunity.

Phagocytosis, the process by which cells internalize large particulate materials from their milieu and sequester them in phagosomes, plays a role in a variety of cell functions ranging from nutrition in ameba to innate and adaptive immunity in mammals. Recent findings revealed unexpected characteristics of phagosomes, highlighting how this complex organelle may have evolved, from Dictyostelium to human, to become a key player in our ability to mount an efficient immune response against a variety of intracellular pathogens.

Animals↗

PubMed1999

Adaptive plasticity in the naso-occipital linear vestibulo-ocular reflex.

The linear vestibulo-ocular reflex (LVOR) during motion along the naso-occipital (NO) axis is governed by eye position and viewing distance. These influences are necessary for the LVOR to maintain stable foveal images during head translation. The response to NO translation must be large when eye position is eccentric from the axis of head motion (i.e., during lateral gaze) and must diminish as eye position approaches straight-ahead, eventually reaching zero when the eye is aligned with the NO axis of motion (the "null point"). As eye position crosses to the opposite side, the LVOR response must reappear, but in the opposite direction, and must grow in magnitude as eccentricity increases. To determine whether the NO-LVOR is subject to adaptive plastic mechanisms, squirrel monkeys were conditioned during NO translation while they binocularly viewed a rich visual field through parallel base-right or base-left wedge prisms. This optical method effectively shifted the visual world 9 degrees leftward or rightward, respectively, thus inducing a mismatch between vision and the NO-LVOR during head movements. To restore compensatory function, the relationship between LVOR sensitivity and horizontal eye position must shift by 9 degrees in the same direction as the visual image shift, effectively shifting the null point. After 2 h of adaptive conditioning, all monkeys exhibited an adaptive shift in the appropriate direction by an average of 3.0 degrees (range 0.7-5.0 degrees), corresponding to 33% of the geometrically required adaptation.

Adaptation, Physiological↗

PubMed1991

Separate processing of "color" and "brightness" in goldfish.

Spectral sensitivity was measured under different adaptation levels using a behavioral training technique in which the fish had to discriminate between a dark test field and a test field illuminated with monochromatic light. Depending on which of the two test fields was used as training test field, two functions were obtained which differ (1) in absolute sensitivity and (2) in shape. When trained on the dark test field, the fish seems to discriminate on the basis of a "color" cue, but it uses a "brightness" cue when trained on the illuminated test field. This was concluded from measurements of wavelength discrimination. Under low levels of the adaptation light (1.5 and 0.2 lx instead of 20 lx), the L-cone type contributes to perception of "brightness" but not to color vision. This difference in the adaptation behavior in the long-wavelength range was used to identify the ganglion cells which may represent channels for "brightness" and "color" in the retina. Action spectra were recorded extracellularly at different levels of dark- and light-adaptation.

Animals↗

PubMed1996

Adaptive changes in saccade amplitude: oculocentric or orbitocentric mapping?

The saccadic system rapidly adjusts the amplitude of refixation movements to visual targets when abnormal postsaccadic errors occur. This is called rapid saccadic adaptation. It is not yet clear whether this form of adaptation produces changes related to oculocentric mechanisms, such as retinal error or motor error, or orbitocentric mechanisms, such as eye or gaze position. These experiments were designed to test whether rapid saccadic adaptation was orbitocentric, oculocentric, or both by creating a precise sensory motor mismatch between the visual target and the required saccade. Measurements were made to determine adaptive changes as function of (1) saccade direction; (2) eye position; and (3) saccade amplitude. Changes were found to be amplitude- and direction-specific but changes were generalized across a broad range of orbital positions. Two conditions of adaptation: increasing and decreasing amplitude, produced quantitatively similar results, indicating that similar mechanisms underlie both processes. Thus, these data support the view that changes during rapid saccadic adaptation are organized principally in a retina-referenced (oculocentric) map, but only broadly, if at all, in a head-referenced (orbitocentric) map. The changes are consistent with a mechanism represented in a spatial mapping of either retinal or motor error.

Adaptation, Ocular↗

PubMed1976

Measured intelligence in offspring of oral and nonoral contraceptive users.

A study has been made of measures of intelligence of 210 children (5 to 8 years of age) born to mothers who used oral and nonoral contraceptives pregestationally. Ninety-six of these children were born to mothers who used oral contraceptives, and one hundred and fourteen were born to mothers who used vaginal contraceptive methods. The intelligence of the children was measured in the form of the full-scale I.Q. score by the Wechsler Intelligence Scale for Children (WISC) adapted and normalized for Puerto Rico by the Puerto Rico Department of Education. A three-factor analysis of variance was performed on the data collected for comparison of the two groups. It was observed that there was no significant difference between the average I.Q. scores of children born to mothers using oral contraceptives and those born to the mothers using nonoral contraceptives. The average I.Q. in children of the oral contraceptive group was 85.04 and that in children of the nonoral contraceptive group was 85.54. Distributions for both groups were also found to be similar. No significant differences between means were observed for sex, age, and interacitons with the exception of the age and sex interaction, where, again, no specific, meaningful trend could be established. The average I.Q. in the sample fell very close to the center of the "normal" range of the WISC, Puerto Rican adaptation. The results of the study do not offer any evidence as to the effect of the use of oral contraceptives on the intelligence measure (by the WISC) of the offspring born to mothers using them pregestationally. The children under study, on an average, are of "normal" intelligence as measured by the Puerto Rican intelligence standards.

Adult↗

PubMed1985

Enzyme linked immunosorbent assay for lactoferrin. Plasma and tissue measurements.

Highly purified lactoferrin was obtained from human breast milk by sequential use of affinity chromatography and isoelectric focusing. IgG antibody to purified lactoferrin was used to develop a sensitive and reproducible enzyme linked immunosorbent assay. Characteristics of the assay included linearity over a wide range of lactoferrin concentration (3.125-200 micrograms/l) and sensitivity (lower range less than 1 microgram/l). The assay can be adapted for use on tissue cytosol as well as plasma. Healthy subjects showed plasma lactoferrin levels ranging from 187.5-450.1 micrograms/l. Pulmonary tuberculosis and acute pneumonia are associated with a 2-3-fold increase in plasma lactoferrin content while neutropenic subjects have markedly depressed lactoferrin concentrations. The assay will be useful for further delineation of lactoferrin and neutrophil function and turnover.

Antibodies↗

PubMed2004

Longitudinal assessment of adaptive behavior in infants and young children with newly diagnosed epilepsy: influences of etiology, syndrome, and seizure control.

OBJECTIVES: The outcomes of childhood-onset epilepsy are highly varied and have several potential determinants. We examined the independent effects of syndrome type, seizure control, and etiology over time on adaptive behavior as measured by the Vineland Scales of Adaptive Behavior. METHODS: As part of a prospective community-based study of newly diagnosed epilepsy, parents of children who were younger than 3 years at the time of initial onset of epilepsy completed the Vineland Adaptive Behavior Scales screener version at entry into the study and once a year thereafter for up to 3 years. Longitudinal analyses were performed on the composite score as the primary outcome and on the 4 domain scores (communication, socialization, motor, and daily living) as confirmatory/secondary outcomes to determine the effects of syndrome (epileptic encephalopathy or other), seizure control (intractable or not), and etiology (symptomatic or not) on adaptive behavior at the time of initial diagnosis and over time. RESULTS: A total of 613 children were enrolled in the study, and 191 (31%) of these children met the age criterion for this analysis. Of these, 172 (90%) had adequate follow-up and had completed baseline and at least 1 subsequent Vineland assessment. Overall, Vineland scores (composite and individual domains) were somewhat below average at baseline (initial diagnosis). All declined significantly over time. All of the effects at baseline, however, were limited to children with epileptic encephalopathies and symptomatic etiology. Substantial declines over time occurred in these children, and there was an independent effect of intractable seizures as well. In children with none of these factors ( approximately 75% of the study group), baseline scores were consistent with average performance for the test norms and there was no evidence of any decline over time. CONCLUSIONS: Children with an underlying symptomatic etiology or a syndrome that can be characterized as 1 of the epileptic encephalopathies demonstrate impaired adaptive behavior at the time of initial diagnosis and experience additional declines in assessments of age-adjusted performance over time. Our results suggest that future seizure outcome is not strongly reflected in adaptive behavior at initial diagnosis but that it takes its toll on the child over time. Understanding how each of these factors affects development and how they interact with each other is the next step in designing effective interventions for lessening the impact of these disorders on the child. In the majority of children with onset of epilepsy during infancy or early childhood, adaptive behavior is within the normal range and does not show any evidence of declining over time. Although this is encouraging, it does not contradict other studies that have demonstrated behavioral and relatively subtle cognitive difficulties in school-aged children with epilepsy. Long-term follow-up in this cohort will permit us to examine the predictive value of the Vineland for later behavioral and cognitive difficulties in this group that, so far, seems to be doing well.

Activities of Daily Living↗

PubMed1985

Adenine nucleotide and P-creatine levels in layers of frog retina as a function of dark and light adaptation.

Eight layers of frog retina were analyzed for ATP, P-creatine, ATP + ADP, and AMP under conditions of dark, 2 sec, 2 min, and in the case of AMP, 2 hr of light adaptation. Samples of each layer, usually ranging between 5 and 50 ng, were dissected from lyophilized frozen sections. After brief light exposure, ATP dropped while ADP rose sharply in the pigment epithelium, outer segments, and inner segments; ADP was too low to be measured accurately in the inner retina. The profile of ATP, P-creatine, and ATP + ADP concentrations showed peaks in the inner nuclear and ganglion layers. AMP, by contrast, was highest in the two plexiform layers. Levels in the inner retina dropped after only 2 sec of light but rose after 2 hr to levels that were higher than dark values in all retinal layers. AMP was often characterized by a non-uniform distribution: adjacent areas of a layer agreed very closely in value to each other but could vary several-fold from a different section of the same frog or from another frog exposed to the same conditions. This distribution produced clusters of values, particularly prominent in dark-adapted animals, something not observed with the other metabolites measured. The peaks of AMP in the plexiform layers suggest that AMP may be a by-product of dopamine-stimulated adenylate cyclase which also has peaks in these same layers.

Adenine Nucleotides↗

PubMed1997

The selectivity of the hair cell's mechanoelectrical-transduction channel promotes Ca2+ flux at low Ca2+ concentrations.

The mechanoelectrical-transduction channel of the hair cell is permeable to both monovalent and divalent cations. Because Ca2+ entering through the transduction channel serves as a feedback signal in the adaptation process that sets the channel's open probability, an understanding of adaptation requires estimation of the magnitude of Ca2+ influx. To determine the Ca2+ current through the transduction channel, we measured extracellular receptor currents with transepithelial voltage-clamp recordings while the apical surface of a saccular macula was bathed with solutions containing various concentrations of K+, Na+, or Ca2+. For modest concentrations of a single permeant cation, Ca2+ carried much more receptor current than did either K+ or Na+. For higher cation concentrations, however, the flux of Na+ or K+ through the transduction channel exceeded that of Ca2+. For mixtures of Ca2+ and monovalent cations, the receptor current displayed an anomalous mole-fraction effect, which indicates that ions interact while traversing the channel's pore. These results demonstrate not only that the hair cell's transduction channel is selective for Ca2+ over monovalent cations but also that Ca2+ carries substantial current even at low Ca2+ concentrations. At physiological cation concentrations, Ca2+ flux through transduction channels can change the local Ca2+ concentration in stereocilia in a range relevant for the control of adaptation.

Animals↗

PubMedDate not supplied

Contrast adaptation in striate cortical neurons of the nocturnal primate bush baby (Galago crassicaudatus).

It has been argued that in order for the visual system to detect edges accurately under a range of conditions, the visual system needs to adapt to the local contrast level to preserve sensitivity (Blakemore & Campbell, 1969). Cells in the primary visual cortex of cats adapt to stimuli with low to moderate contrast. Curiously, macaque monkey neurons in primary visual cortex (V1) do not show evidence for similar adaptation. To address the question of whether this differential sensitivity in contrast adaptation might be due to phylogenetic variation between cats and primates or to specializations for visual niche (e.g. nocturnal vs. diurnal), contrast adaptation to temporally and spatially optimized gratings was examined in 30 V1 cells of three nocturnal primate bush babies (Galago crassicaudatus). A second objective was to examine the relationship between the degree of contrast adaptation and cell classification or cell location relative to cortical layers or compartments [i.e. cytochrome-oxidase (CO) blobs and interblobs]. All cells were classified (simple vs. complex) and anatomically localized relative to cortical layers and cytochrome-oxidase (CO) blob and interblob compartments. Two independent measures of contrast adaptation were used. In the first test, contrast was sequentially increased from 3-56% and then decreased. The contrast required to maintain a half-maximum response amplitude in the 30 cells tested increased an average of 0.24 (+/- 0.12) log units during the sequential decrements in contrast. For the second test, four sets of five interleaved contrasts within +/- 1 octave of a central adapting contrast (10%, 14%, 20%, and 28%, respectively) were presented. The cells produced a mean adaptation index of 0.57 (+/- 0.47) which is very similar to that exhibited by cat cortical neurons (0.54 +/- 0.41). Interestingly, cells in interblobs showed a trend toward greater adaptation than did blob cells. Moreover, cells in the supragranular layers exhibited greater adaptation than cells in the infragranular layers. No significant differences in adaptation were found to correlate with other cell classification indices. Taken together, our results suggest that contrast adaptation may be more important for maintaining sensitivity in nocturnal species (primates or cats) than in diurnal species (macaque monkeys), and that in the nocturnal bush baby, cells in cortical layers and compartments may be differentially specialized for contrast adaptation.

Adaptation, Ocular↗

PubMed2006

[The blood system and the adaptation of the organism to extreme factors].

Study of hemopoesis under extremal conditions has revealed a range of new mechanisms providing the participation of the blood system in adaptive reactions, such as the reconstruction of the microcirculation bed of hemopoetic tissue; the involvement of large erythrocytes containing acid-resistant hemoglobin fractions; qualitative and quantitative changes in the content of erythroblastic islands, depending on the functional condition of macrophages; gaining of morphogenic properties by macrophages and lymphocytes; increased secretion of glycosaminoglicans, which play the role of local hemopoetic regulators, by mastocytes and adipose cells. The correlation between blood cells and angiogenesis allowed proposing a new method of creating auto prostheses for angioplasty by growing them on plastic basis implanted subcutaneously.

Adaptation, Physiological↗

PubMed2004

Adventures in oxygen metabolism.

Peter W. Hochachka led a grand life of science adventure and left as his legacy a whole new field--biochemical adaptation. Oxygen was at the core of Peter's career and his laboratory made major contributions to our understanding of how animals deal with variation in oxygen availability in many forms. He analyzed the molecular mechanisms that support facultative anaerobiosis, studied muscle exercise metabolism for high speed flight, swimming and running, investigated mammalian diving on many trips to the Antarctic to study Weddell seals, and probed the metabolic and genetic adaptations that provide optimal hypoxia tolerance for humans residing at high altitudes. His work illuminated both biochemical and physiological mechanisms that are used to optimize aerobic metabolism, to compensate for hypoxic insults, and to conserve energy by strong metabolic rate depression under anoxia. His articles, books and lectures galvanized the field with leading-edge insights and theories and he consistently challenged comparative biochemists to use their unique model systems to explore the range and breadth of animal strategies of biochemical adaptation. Lessons drawn from my training in Peter's laboratory have led me on continuing explorations of adaptations in enzyme function, signal transduction, gene expression, and antioxidant defenses ranging over systems of anoxia tolerance, freezing survival, estivation, and mammalian hibernation.

Adaptation, Physiological↗

PubMed1990

Adaptive behavioral responses to potential infertility among survivors of testis cancer.

In a retrospective study of 153 testis cancer survivors, we examined the sociodemographic and clinical determinants of attitudes and behaviors toward illness-induced infertility. Five fertility adjustment responses were identified: sperm-banking awareness (SBA); adoption awareness (AA); fertility testing (FT); trying to father children (TFC); and fertility distress (FD). Although responses to infertility are multidetermined, these data demonstrate there is a distinct sociodemographic and clinical profile for the subgroups of men who engage in different fertility-related behaviors. Multivariate analysis results show that men most likely to be concerned with banking sperm are those who at diagnosis are younger (less than 35 years), childless, college educated, and whose relationships have become strained. Men who sought fertility tests were childless, college graduates, and able to ejaculate. The only factor predicting adoption was childlessness. Those married men attempting to father children were also less than 35 years of age at diagnosis and without ejaculatory dysfunction. The men at greatest risk for continued distress about infertility were those who remained childless and had posttreatment ejaculatory dysfunction. Residual infertility distress also was significantly associated with treatments that included extensive retroperitoneal lymph node dissection (RPLND) surgery, indicating that the latter is a "risk factor" in survivors' long-term distress. These data, while not definitive, show that the prerogative to have children is very important to men and that losing it sets into motion a range of both adverse emotions and adaptive responses. Adjustment to infertility is a complex process that begins at diagnosis and extends long after treatment is completed.

Adolescent↗

PubMed1992

Biochemical mechanism of light adaptation in vertebrate photoreceptors.

Vertebrate photoreceptors can adjust their sensitivity to a wide range of light intensities spanning several orders of magnitude, the phenomenon of which is called light adaptation. Electrophysiological and biochemical studies have revealed that calcium can serve as an intracellular transmitter of light adaptation under the control of cGMP metabolism. After illumination, the cytoplasmic calcium concentration of a photoreceptor decreases, which in turn strongly activates photoreceptor guanylate cyclase. This calcium-dependent effect is mediated by a novel calcium-binding protein (recoverin) and leads to the restoration of the depleted cGMP pool after illumination.

Adaptation, Ocular↗

PubMed1992

Subtractive and divisive adaptation in the human visual system.

Sensory systems can adapt to the conditions imposed on them. In the visual system, adapting to a pattern increases the threshold of the ability to see that pattern, and reduces the perceived contrast of the pattern above threshold. Most neurons of the striate cortex reduce their responsiveness after being stimulated for some time by a high-contrast pattern. Such an effect may lie behind these psychophysical adaptation phenomena. These adaptation effects have been reported to be confined to patterns of similar orientation, which is understandable in that the visual neurons that adapt are only excited by a small range of orientations. Neurophysiological evidence suggests that neurons with different orientation preferences have inhibitory interconnections. It is therefore of interest to explore the possible effects of these connections on perception. Here we show that adapting to a horizontal pattern can reduce the perceived contrast of a vertical test pattern more than a horizontal test pattern. These 'cross-orientation' effects are modelled by a division-like process, whereas the more normal 'similar-orientation' effects are modelled by a subtractive process.

Adaptation, Ocular↗

PubMed1998

Neural constraints on eye motion in human eye-head saccades.

We examined two ways in which the neural control system for eye-head saccades constrains the motion of the eye in the head. The first constraint involves Listing's law, which holds ocular torsion at zero during head-fixed saccades. During eye-head saccades, does this law govern the eye's motion in space or in the head? Our subjects, instructed to saccade between space-fixed targets with the head held still in different positions, systematically violated Listing's law of the eye in space in a way that approximately, but not perfectly, preserved Listing's law of the eye in head. This finding implies that the brain does not compute desired eye position based on the desired gaze direction alone but also considers head position. The second constraint we studied was saturation, the process where desired-eye-position commands in the brain are "clipped" to keep them within an effective oculomotor range (EOMR), which is smaller than the mechanical range of eye motion. We studied the adaptability of the EOMR by asking subjects to make head-only saccades. As predicted by current eye-head models, subjects failed to hold their eyes still in their orbits. Unexpectedly, though, the range of eye-in-head motion in the horizontal-vertical plane was on average 31% smaller in area than during normal eye-head saccades, suggesting that the EOMR had been reduced by effort of will. Larger reductions were possible with altered visual input: when subjects donned pinhole glasses, the EOMR immediately shrank by 80%. But even with its reduced EOMR, the eye still moved into the "blind" region beyond the pinhole aperture during eye-head saccades. Then, as the head movement brought the saccade target toward the pinhole, the eyes reversed their motion, anticipating or roughly matching the target's motion even though it was still outside the pinhole and therefore invisible. This finding shows that the backward rotation of the eye is timed by internal computations, not by vision. When subjects wore slit glasses, their EOMRs shrank mostly in the direction perpendicular to the slit, showing that altered vision can change the shape as well as the size of the EOMR. A recent, three-dimensional model of eye-head coordination can explain all these findings if we add to it a mechanism for adjusting the EOMR.

Adult↗