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PubMed2002

Photogravitropic equilibrium in Avena coleoptiles: fluence rate-response relationships and dependence on dark adaptation and clinostating.

Phototropism of Avena coleoptiles was measured in response to blue-light irradiation lasting between 2 and 24 h. During this time the coleoptiles established a bending angle of photogravitropic equilibrium that was dependent on the time of irradiation and also on the pretreatment in light or darkness prior to stimulation. The absolute threshold for the photogravitropic equilibrium in response to blue light was 10(-8) micromol m(-2) s(-1). Photon fluence rate-response curves, which were generated after several hours of dark adaptation, had a characteristic shape with a prominent optimum in the middle of the dynamic range. Curves which were generated without prior dark adaptation displayed no such optimum. Clinostating dark-adapted coleoptiles caused an increase of sensitivity and responsiveness during a 2-h period of unilateral irradiation. The advantages and the drawbacks of long-term irradiation experiments for the investigation of phototropism and the generation of action spectra are discussed.

Journal Article↗
PubMed1993

Auditory processing in children's speech perception: results of selective adaptation and discrimination tasks.

Five- to six-year-old children and adults participated in discrimination and selective adaptation speech perception tasks using a synthetic consonant-vowel continuum ranging from [ba] to [da]. In one condition of selective adaptation, attention was focused on the adapting stimulus, the continuum-endpoint [ba], with a whispering task. In another condition, attention was focused away from the continuum-endpoint [da] adaptor to contralaterally presented syllables "SHE" and "SEE." Results, compared with two more typical adaptation conditions, indicated that focused attention did not augment selective adaptation effects, particularly for children who showed smaller effects with focused attention on the adaptor. In contrast to adults, children did not significantly change labeling responses after exposure to endpoint-[ba] adaptors, results matching those of Sussman and Carney (1989). However, children did significantly change labeling following exposure to endpoint-[da] adaptors. Discrimination findings with five-formant consonant-vowel and single-formant stimuli supported the importance of acoustic processing for the selective adaptation tasks performed. Together, results support hypotheses of sensory processing differences in younger, normally developing children compared with adults and show that such abilities appear to be related to speech perception skills.

Acoustic Stimulation↗
PubMed1985

The early phase of dark adaptation in human infants.

Two types of thresholds with 8 degrees circular test fields were measured in 7- and 13-week-old human infants and in adults. Increment thresholds were measured against adapting fields of 0.50 and 50 cd/m2. All ages showed Weber's Law for incremental sensitivity over this 2 log unit range of luminance. Thresholds during early dark adaptation were also measured for the 5 sec immediately following the offsets of these adapting fields. The reductions in threshold during the early phase of dark adaptation were quantitatively similar in all age groups at both adapting luminances, despite substantial developmental differences in the absolute values of these thresholds. These data do not reject the hypothesis that the neural processes underlying early dark adaptation are adult-like in early infancy.

Adult↗
PubMed1962

Temperature effects on day old Drosophila pupae.

Day old Drosophila pupae were subjected to a variety of closely controlled temperature shocks. Twenty-five hours after puparium formation (at 23 degrees ), temperatures from 39.5-41.5 degrees (Q(1) = 2.3) differentially disturb the formation of the posterior crossvein. Three other separate treatments disturb posterior crossvein formation: treatments in the range 36.0-37.0 degrees at 25 hours; 37.3-37.8 degrees at 25 hours; and 39.5-41.5 degrees at 19 hours. Certain qualitative effects are associated with certain temperatures: elliptical holes are seen in wings of flies exposed 25 hours after puparium formation to temperatures from 37.3-37.8 degrees . Anterior crossvein defects ensue if animals are similarly exposed to temperatures from 37.9-38.2 degrees . Within the physiological range, animals raised at higher temperatures are more resistant to the effects of temperatures at 39.5-41.5 degrees . An extremely rapid temperature adaptation by exposures to temperatures in the range 31-38 degrees results in markedly greater resistance to heat shock; here resistance to production of crossvein defects increases faster than to death. The association between qualitative effects and treatment temperatures is modified by changing the temperature at which the animals spend their first day of pupal life. Summation experiments support conclusions drawn from the simpler experiments. Genetic variation and interspecific variation are discussed in the present context, as well as implications of the role of protein denaturation in the biological effects of high temperatures and further, more general experiments.

Adaptation, Physiological↗
PubMed2002

Radiation hormesis: challenging LNT theory via ecological and evolutionary considerations.

Ecological and evolutionary considerations suggest that radiation hormesis is made up of two underlying components. The first (a) is background radiation hormesis based upon the background exposure to which all organisms are subjected throughout evolutionary time. The second and much larger component (b) is stress-derived radiation hormesis arising as a protective mechanism derived from metabolic adaptation to environmental stresses throughout evolutionary time especially from climate-based extremes. Since (b) > > (a), hormesis for ionizing radiation becomes an evolutionary expectation at exposures substantially exceeding background. This biological model renders linear no-threshold theory invalid. Accumulating evidence from experimental organisms ranging from protozoa to rodents, and from demographic studies on humans, is consistent with this interpretation. Although hormesis is not universally accepted, the model presented can be subjected to hypothesis-based empirical investigations in a range of organisms. At this stage, however, two consequences follow from this evolutionary model: (1) hormesis does not connote a value judgement usually expressed as a benefit; and (2) there is an emerging and increasingly convincing case for reviewing and relaxing some recommended radiation protection exposure levels in the low range.

Adaptation, Physiological↗
PubMed1998

The morphological basis of increased stiffness of rabbit tibialis anterior muscles during surgical limb-lengthening.

When the tibialis anterior muscle of the rabbit is progressively stretched during surgical limb distraction, the muscle fibres lengthen by addition of new serial sarcomeres, provided that stretch is carried out at an appropriate rate. However, in spite of the apparent adaptation to the new functional length, range of joint movement is greatly decreased. In this study we have first, made measurements of the passive tension developed by distracted muscles over the range of joint movement and secondly made quantitative measurements of endomysial and perimysial connective tissue content. It was found that at all ankle joint angles greater than 90 degrees, the passive tension developed by the distracted muscles was greater than both contralateral and sham-operated controls. Image analysis showed that the ratio of collagen to contractile material was increased in distracted muscles compared with muscles from sham-operated controls, due to increased deposition of collagen type III. Scanning electron microscopy showed the presence of a dense perimysial weave surrounding the distracted muscle fibres. These quantitative and qualitative changes in the connective tissue component could account for the increased stiffness demonstrated by the physiological measurements. It would seem that in distracted muscle the connective tissue element adapts less readily than the contractile component, with prolonged stretch leading to damage to the perimysial and endomysial network, with subsequent fibrosis and loss of muscle compliance. Such changes could help explain the loss of range of movement noted in the distracted limbs of patients undergoing surgical limb-lengthening and in other conditions that result in muscle contractures.

Adaptation, Physiological↗
PubMed1976

Studies on the biodegradation of nonionic surfactants applied in the polyestre fibre industry. III. Effect of adaptation on the respiratory activity of organisms and on the biocenosis of inoculated sludge.

Manometric studies were conducted in 3 series. In the first one the sludge used for inoculation was non adapted to water purification containing surfactants. In the second and third series it was adapted to the sludge load 0.11 and 0.28 mg surfactant/mg d.w./day respectively. Increase in oxygen uptake was proportional to the degree of the adaptation of microorganisms only within limited range of surfactant concentration not exceeding 500 mg/l for Cirrasol FP and 1000 mg/l for Cirrasol SF and Cirrasol TCS. The toxic action of surfactants against Ciliata was noted at concentration above 100 mg/l and for Mastigota and Sarcodina above 500 mg/l, even by using adapted sludge for inoculation.

Adaptation, Physiological↗
PubMed2006

Physiological activity depresses synaptic function through an effect on vesicle priming.

Neurons engage compensatory, homeostatic synaptic changes to maintain their overall firing rate. We examined the induction and expression of a persistent presynaptic adaptation. We explored the effect of mild extracellular potassium elevation to increase hippocampal pyramidal neuron spiking over a physiological range. With several days of mild depolarization, glutamate release adapted, as revealed by an increased mismatch between the number of active, FM1-43-positive, glutamatergic synapses and the total number of synapses defined by vesicular glutamate transporter-1 antibody staining. Surprisingly, the adaptation of glutamate terminals was all-or-none; recycling vesicle pool size at remaining active synapses was not significantly altered by the adaptation. Tetrodotoxin (TTX), but not postsynaptic receptor blockade, reversed depolarization-induced adaptation, and TTX added to normal incubation medium increased the number of active synapses, suggesting that normal spiking activity sustains a steady-state percentage of inactive terminals. Chronic mild depolarization depressed EPSCs and decreased the size of the readily releasable pool of vesicles (RRP). Several hours of 10 Hz electrical stimulation also depressed the RRP size, confirming that spiking alone induces adaptation and that strong stimulation induces more rapid presynaptic adaptation. Despite the importance of RRP alteration to the adaptation, ultrastructural experiments revealed no changes in docked or total synaptic vesicle numbers. Furthermore, alpha-latrotoxin induced vesicle release at adapted synapses, consistent with the idea that adaptation resulted from changes in vesicle priming. These results show that glutamatergic neurotransmission persistently adapts to changes in electrical activity over a wide physiological range.

2-Amino-5-phosphonovalerate↗
PubMed1994

[The development of a research program based on a conceptual model for the discipline of nursing].

The purpose of this article was to illustrate the development of a team's research program based on a conceptual model for the nursing discipline: Roy's Adaptation Model. The ongoing research program includes studies of psychosocial factors, theoretically known for their potential for explaining health. Four groups of people are the focus of these studies: aged spouses in the community, family caregivers of ill elderly people, family caregivers of mentally ill people, and nurses as professional caregivers for elderly people in institutions. The studies are articulated using the three-level structure proposed by Fawcett & Downs (1986) and Fawcett (1991): conceptual-theoretical-empirical. This research program aims to renew understanding of the person's adaptation processes to various environmental stimuli, adaptive responses that influence health, and nursing interventions that promote health (i.e., biopsychosocial integrity). In order to specify the research variables and relations to be studied between these variables in the first phase of the program, each research project is also guided by a middle-range theory compatible with Roy's Adaptation Model. Elaborated within related disciplines, these theories are variations of the Stress and Coping theory of Lazarus & Folkman (1984). The results of these studies will be compared and articulated in a model that integrates the patterns of relations between the variables. The resulting empirical model together with Roy's conceptual model will be used to guide the development of nursing interventions intended to promote adaptive responses and biopsychosocial integrity. The second phase of the research program includes the implementation and evaluation of nursing strategies that promote adaptation among the four groups of people. This research program is a nursing contribution to certain social issues recognized as priorities by the governments of Canada and Québec. This article is an illustration of one of the various ways of developing nursing knowledge.

Adaptation, Psychological↗
PubMed2026

The Jumonji C domain-containing proteins GmJMJ19 and GmJMJ20 link florigen signaling with epigenetic regulation of photoperiodic flowering and post-flowering plant height in soybean.

Soybean (Glycine max) is a photoperiod-sensitive legume whose latitudinal adaptation depends on the precise control of flowering time and plant height. Histone demethylases of the JmjC domain-containing (JMJ) protein family have been implicated in these processes across plant species, but their specific roles in soybean remain largely unexplored. Here, we identify soybean GmJMJ19 and GmJMJ20, two closely related JMJD5/KDM8 orthologs, as master epigenetic regulators that coordinately control both photoperiodic flowering and post-flowering plant height. Both genes exhibit intrinsic, rhythmic expression peaking at ZT12, and their encoded proteins physically interact with the florigen proteins FT2a and FT5a. Loss-of-function mutants display delayed flowering under long days (LDs) and increased plant height under both LDs and short days (SDs), whereas overexpression phenocopies the mutant flowering phenotype, indicating revealing a critical dosage requirement for proper function. Mechanistically, GmJMJ19 and GmJMJ20 are recruited by the FT/FD transcriptional complex to directly activate AP1a and AP1c expression through chromatin modulation. Population genomic analyses reveal distinct selection signatures: GmJMJ19 underwent sustained directional selection during cultivation, whereas GmJMJ20 experienced an early domestication sweep with limited subsequent change. Haplotype analysis identifies coordinated latitudinal clines, with the JMJ19H1/JMJ20H1 combination predominating at high latitudes to promote early flowering and limit height, while JMJ19H2/JMJ20H2 and wild JMJ19H3/JMJ20H3 alleles prevail at low latitudes, conferring later flowering and increased height. Collectively, our findings establish GmJMJ19 and GmJMJ20 as central chromatin regulators linking florigen signaling to downstream target expression and provide valuable allelic resources for breeding regionally adapted soybean varieties across a wide range of latitudinal environments.

Histone modulation↗
PubMed1983

Passive membrane properties, afterpotentials and repetitive firing of superior colliculus neurons studied in the anesthetized cat.

Intracellular recording and staining with HRP were used to characterize cat superior colliculus neurons with identified projection into the tecto-bulbo-spinal tract (TBSNs). TBSNs are large multipolar neurons with heavy stem dendrites. First and second order dendrites bifurcate with an average branch power n of about 3/2. More peripheral branch points have n less than 1.5. Input resistances of TBSNs range from 0.9 to 4.6 M omega. Most TBSNs display 'anomalous rectification'. Based on Rall's steady-state cable equations, input resistances were calculated for 3 TBSNs labelled with HRP. Assuming a specific membrane resistance of 2,300-2,600 omega cm2 the/calculated values agree well with the experimentally determined estimates from another set of non-stained TBSNs. Membrane time constants of TBSNs range from 3.0 to 5.6 ms. The electrotonic length was calculated using the ratio tau 0/tau 1. The respective average value was 1.13. TBSNs respond to orthodromic, antidromic and direct stimulation with action potentials of 60-80 mV, composed of IS- and SD-components. The critical interval for IS-SD-invasion was on average 1.6 ms. Spike decomposition occurs usually at M-level. The postspike conductance increase underlying hyperpolarizing afterpotentials (HAP) decays exponentially, with the time constants tau F = 1.5 ms and tau S = 13 ms. The HAP was equilibrated at membrane potentials of -73 to -90 mV. When tested by antidromic stimuli at varying intervals most TBSNs show very poor "summation" of HAPS. A pronounced depolarizing hump (DD) follows antidromic action potentials. Discharging at short intervals leads to a substantial increase and prolongation of DD. This apparent DD-potentiation is interpreted as a phenomenon secondary to the reduction of hyperpolarizing currents. In response to directly injected currents, TBSNs discharge with frequencies up to 1,100 imp/s. The frequency-current curves of TBSNs are characterized by 3 ranges. The average f-i-slopes of the adapted discharge were 19.2 imp/s/nA and 56.4 imp/s/nA for the 1st and 2nd range, respectively. At intermediate current intensities (2nd range) TBSNs discharge in groups of 2 to 7 action potentials, following each other at intervals of 1.0-2.8 ms. The spike groups are separated by pauses of 3.5-6.3 ms duration. The transition from 1st (low frequency continuous) discharge range to 2nd (grouped) discharge range is related to the appearance of extra-spikes. Extra-spikes are generated from a decreased firing level, from the peak of an enhanced DD.(ABSTRACT TRUNCATED AT 400 WORDS)

Action Potentials↗
PubMed2005

The role of retinal adaptation in night driving.

PURPOSE: Driving is essentially a visuomotor task, and there is now compelling evidence that the disproportionate number of road accidents under night driving conditions is linked to changes in visual performance resulting from reduced lighting. The objective of this article is to establish the extent to which vision is either rod-or cone-dominated under night driving conditions. METHODS: Visual thresholds are measured under lighting conditions that simulate urban lighting. Dark adaptation curves are obtained under three ambient lighting conditions ranging from low (0.1 cd/m) to high (5 cd/m) mesopic levels of retinal adaptation using circular discs of different sizes (1 degree, 2 degrees, 3 degrees, and 5 degrees) presented at retinal eccentricities of 0 degrees, 10 degrees, 20 degrees, 30 degrees, and 40 degrees. RESULTS: The dark adaptation curves exhibit the classic inflection point between rod and cone activity for the lower levels of ambient illumination but a simple monophasic function for the high mesopic levels (>0.5 lux). Adaptation rates are four times faster for the higher compared with the lower illumination level and twice as fast for central compared with peripheral presentation. CONCLUSIONS: The data suggest that vision is mediated by cone pathways at 5 lux and by rod pathways at 0.5/0.1 lux. This shift does not profoundly affect sensitivity, but because rod pathways are known to be slower than cone pathways, it will certainly affect observers' ability to respond to rapidly changing viewing conditions such as are encountered when driving at night.

Adult↗
PubMed1979

Studies of ciliated epithelia of the human genital tract. 3: Mucociliary wave activity in organ cultures of human Fallopian tubes challenged with Neisseria gonorrhoeae and gonococcal endotoxin.

Quantative determinations of the mucociliary activity of human Fallopian tube epithelium maintained as organ cultures were performed using a light beam reflex method. In non-infected organ cultures the mucociliary wave (MCW) frequency slowly decreased during the first 54 hours of culture maintenance. In organ cultures experimentally infected with fresh isolates of Neisseria gonorrhoeae producing T1/T2 colonies the MCW frequency either decreased to subnormal values or completely ceased whereas in organ cultured infected with a laboratory-adapted gonococcal strain the MCW frequencies remained within normal range. In organ cultures exposed to gonococcal endotoxin prepared from the laboratory-adapted strain, as well as in cultures in which cell-free filtrates of medium from organ cultures infected with N. gonorrhoeae (producing T1/T2 colonies) were added to the culture medium, the ciliary activity decreased and subsequently ceased. The same phenomenon occurred when organ cultures were challenged with Escherichia coli endotoxin. The ciliostatic effect appeared before any morphological changes in the surface epithelium, including the cilia, were demonstrable by scanning electron microscopy.

Adult↗
PubMed1989

Radio-adaptive response: characterization of a cytogenetic repair induced by low-level ionizing radiation in cultured Chinese hamster cells.

Pretreatment with low doses of beta-rays from incorporated tritiated thymidine ([3H]dThd) or of Co-60 gamma-rays (1 or 5 cGy) rendered actively growing Chinese hamster V79 cells more resistant to the induction of micronuclei or sister-chromatid exchanges (SCEs) by a subsequent high dose of gamma-rays (1 Gy). This adaptive response to ionizing radiation (radio-adaptive response) can be induced by an optimal range of low doses of 3H beta-rays, but not by much lower or higher adapting doses. Full expression of the adaptive response induced by the exposure to low doses of 60Co gamma-rays occurred 4 h after the adapting dose. The cells pre-exposed to low doses of gamma-rays showed cross-resistance to challenge doses of gamma-rays themselves and also of mitomycin C (MMC) and near ultraviolet light (UV-B, 313 nm), but not to those of ethyl methanesulfonate (EMS) or cis-platinum (II) diammine dichloride (cisplatin) for SCE induction. These results suggest that the radio-adaptive response mechanistically couples to the repair network which copes with chromatin lesions induced by MMC and UV-B.

Animals↗
PubMed1995

Asperger's syndrome and autism: differences in behavior, cognition, and adaptive functioning.

OBJECTIVE: To determine whether subtypes of children with pervasive developmental disorder (PDD) differed on variables that were relatively independent of distinguishing criteria. METHOD: Higher-functioning children with PDD, 4 through 6 years of age, were differentiated into those with autism (n = 47) and those with Asperger's syndrome (n = 21) on the basis of delayed and deviant language development. The groups were then compared on a wide range of measures including PDD symptoms, adaptive behaviors in communication, socialization, and activities of daily living, and an assessment of verbal and nonverbal cognitive skills. RESULTS: Significant differences between the groups existed on many PDD symptoms, adaptive behaviors, and cognitive measures of language competence, but not on aspects of nonverbal communication, nonverbal cognition, or motor development. CONCLUSION: Subtypes of children with PDD can be identified that differ on variables relatively independent of defining characteristics. These findings should provide a firm foundation into research to determine whether children with autism and Asperger's syndrome also differ on outcome, etiology, and response to treatment.

Activities of Daily Living↗
PubMed1996

Thermotolerance and intracellular pH in two Chinese hamster cell lines adapted to growth at low pH.

As an in vitro model for the low extracellular pH (pHe) which has frequently been observed in tumors, cell lines have been grown in a low-pH medium in order to allow cell adaptation to that milieu. Two Chinese hamster cell lines [Chinese hamster ovary (CHO) and Chinese hamster ovarian carcinoma (OvCa)] were compared, both of which acquired thermotolerance during 42 degrees C heating in pHe = 7.3 buffer, but not in pHe = 6.7 medium unless grown at that pH long enough to become adapted. CHO cells, even when acutely acidified, showed higher intracellular pH (pHi) values in a suspension assay than OvCa cells, which confirmed the danger of comparing absolute values of pHi between cell lines. Despite this fundamental difference, relative changes in pHi were similar in that both lines showed a higher pHi in adapted than in unadapted cells, over the range of pHe values tested. The upregulation of pHi was statistically significant, but the two lines differed in the time frame over which adaptation occurred. OvCa cells acquired an enhanced ability to develop tolerance to 42 degrees heat at pHe = 6.7 in 4 days, but the CHO cells acquired this ability more progressively, achieving a maximum ability at approximately 100 days. In contrast, both lines were able to upregulate their pHi within 4 hours of being exposed to pH 6.7 medium. A further indication of different biochemical mechanisms at work was the opposite effects seen on pHi in the two cell lines upon the removal of extracellular CO2/HCO3-. The differential between adapted and unadapted OvCa cells was enhanced by removal of bicarbonate, whereas CHO cells seemed less stable and the data with greater scatter failed to show any difference between adapted and unadapted cells.

Adaptation, Physiological↗
PubMed2005

Antibody-based detection of acid-shocked, acid-adapted, and apple juice-incubated Escherichia coli O157:H7.

Sandwich enzyme-linked immunosorbent assays (sELISA) allow for rapid detection of Escherichia coli (E. coli) O157:H7. Acidic conditions similar to those in certain foods and juices may reduce the ability to detect E. coli O157:H7. Growth of E. coli O157:H7 at pH 4 compared to pH 5-7 reduced fluorescent signal at the lower bacterial concentrations without altering the range of detection. Both acid-adaptation and a subsequent pH 7 incubation reversed sensitivity. Incubation in apple juice was not deleterious to sELISA detection. Exposure to acidic conditions can cause a small reduction in sELISA sensitivity used to detect E. coli O157:H7.

Acids↗
PubMed2002

Prism adaptation with delayed visual error signals in the monkey.

Errors in reaching produced by displacing the visual field with wedge prisms decrease with trials, even when the error is not revealed until the completion of the movement. To examine how much additional delay in visual feed-back the monkey can compensate for, the effects of delaying the visual error signals were studied by presenting the terminal visual images after one of five delays, ranging from 0 to 500 ms. Adaptation was fastest when the delay was 0 or 10 ms, decreased significantly with a delay as small as 50 ms and approached zero when the delay was 500 ms. The size of the after-effect decreased with the delay accordingly. The results indicate that prism adaptation in the monkey critically depends on the availability of visual information within 50 ms of completion of the movement. Comparing the results with those for humans, we suggest that monkey and human share a mechanism of adaptation with a short time window of 50 ms, but the monkey lacks another mechanism of adaptation that allows a visual delay of 500 ms or more in humans.

Adaptation, Ocular↗