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PubMed2006

The range of adaptation by collateral vessels after femoral artery occlusion.

Natural adaptation to femoral artery occlusion in animals by collateral artery growth restores only approximately 35% of adenosine-recruitable maximal conductance (C(max)) probably because initially elevated fluid shear stress (FSS) quickly normalizes. We tested the hypothesis whether this deficit can be mended by artificially increasing FSS or whether anatomical restraints prevent complete restitution. We chronically increased FSS by draining the collateral flow directly into the venous system by a side-to-side anastomosis between the distal stump of the occluded femoral artery and the accompanying vein. After reclosure of the shunt collateral flow was measured at maximal vasodilatation. C(max) reached 100% already at day 7 and had, after 4 weeks, surpassed (2-fold) the C(max) of the normal vasculature before occlusion. Expression profiling showed upregulation of members of the Rho-pathway (RhoA, cofilin, focal adhesion kinase, vimentin) and the Rho-antagonist Fasudil markedly inhibited arteriogenesis. The activities of Ras and ERK-1,-2 were markedly increased in collateral vessels of the shunt experiment, and infusions of L-NAME and L-NNA strongly inhibited MAPK activity as well as shunt-induced arteriogenesis. Infusions of the peroxinitrite donor Sin-1 inhibited arteriogenesis. The radical scavengers urate, ebselen, SOD, and catalase had no effect. We conclude that increased FSS can overcome the anatomical restrictions of collateral arteries and is potentially able to completely restore maximal collateral conductance. Increased FSS activates the Ras-ERK-, the Rho-, and the NO- (but not the Akt-) pathway enabling collateral artery growth.

Adaptation, Physiological↗
PubMed1981

[Growth of mumps virus in human lung carcinoma cell lines. I. Host-range variant adapted under the presence of anti-mumps virus antibody (author's transl)].

The wild mumps virus which had been isolated from a patient suffering from mumps meningitis propagated biphasically in human lung cancer cell lines (Pc-3, Pc-10), while attenuated Urabe strain propagated monophasically. The early virus was detected in these cell lines when the cells were inoculated with the wild mumps virus at any multiplicity of infection but rapidly disappeared. The infectious virus, thereafter, could not be detected for about 20 days. However, the infectious virus appeared again and the titer of the virus in the culture fluid gradually increased. The late virus rapidly propagated in Pc-3 cells, while the early virus replicated in the same way as the original wild virus did. All of ten clones obtained from the original wild virus represented the biphasic growth in Pc-3 cells and the late virus was detected on the 25th-30th day after infection. The viral antigens in Pc-3 cells infected with wild virus did not disappear after cultivating under the presence of anti-mumps virus antibody for over 50 days. Furthermore, treatment of anti-mumps virus serum in the early period did not affect the appearance of the late virus. It is quite conceivable that the wild mumps virus might be able to persist in completely latent state and the adaptation of the virus to Pc-3 cells might progress during the latent period.

Adaptation, Biological↗
PubMed2000

Cone electroretinogram amplitude growth with light adaptation in patients with retinitis pigmentosa.

PURPOSE: It has been hypothesized that the increase in the b-wave during light adaptation is directly related to the level of cone malfunction in patients with retinitis pigmentosa (RP). Because this hypothesis has important bearing on the mechanism for the increase in the electroretinogram (ERG), we examined the increase in the amplitude of the cone ERG during light adaptation in patients with typical RP. METHODS: Cone ERGs were recorded to Ganzfeld white flash stimuli in the presence of white background illumination in 51 RP patients and in 27 normal subjects. RESULTS: In the normals, the increase in the b-wave amplitude during light adaptation ranged from 14-92% of the dark-adapted amplitude. All RP patients showed an amplitude increase that ranged from 5 to 100% of the baseline amplitude. This increase was not significantly different from that of the normals (p = 0.71, unpaired t-test). The baseline amplitudes and the increase in the relative amplitude were weakly correlated in the RP patients (r = 0.31; p = 0.029). No significant difference was observed in the amplitude increase between patients with near normal b-wave implicit times and those with delayed times (p = 0.17, unpaired t-test). Changes of the b-wave implicit time were not significantly different from those in the controls. CONCLUSION: These findings that the changes in the cone ERG with light adaptation in the RP patients were very similar to those in normal subjects do not support the proposed hypothesis that the increase in the b-wave amplitude during light adaptation was directly related to the level of cone malfunction.

Adaptation, Ocular↗
PubMed2006

Host range nodulation and adaptation in frenchbean rhizobia.

The host range nodulation efficiency of four genetically marked frenchbean rhizobial strains (HURR-3, Raj-2, Raj-5 and Raj-6) was studied with five legume hosts namely, frenchbean (Phageolus vulgaris L.), pigeonpea [Cajanus cajan (L.) Millsp.], mungbean [Vigna radiata (L.) Wilezek.], urdbean [Vigna mungo (L.) Hepper.] and soybean [Glycine max (L.) Merril.]. Except soybean and pigeonpea, all other legume hosts were nodulated by two or more frenchbean rhizobial strains tested. Rhizobia were isolated from nodules produced by strains, HURR-3 and Raj-5, on main (frenchbean) and different (mungbean and urdbean) hosts. There was marked improvement in host range nodulation and nitrogen fixation efficiency of rhizobial strains, HURR-3 and Raj-5. after their isolation from chance nodules on different hosts. This is clearly evident from the ability of such isolates to form nodules on pigeonpea besides mungbean and urdbean, and higher nodulation in all the above three different hosts. The phage-susceptibility pattern and intrinsic antibiotic resistance (used as markers) of the two strains did not change after their passage through different hosts. The results indicate that frenchbean rhizobia had undergone some modification in symbiotic behaviour to adapt to wide host range during their passage through different (alternate?) hosts.

Adaptation, Biological↗
PubMed1986

Adaptation of tonic accommodation reduces accommodative lag and is masked in darkness.

Tonic aftereffects of accommodation were investigated under three open loop conditions; Maxwellian view (pin hole pupil), empty field, and darkness. Duration of accommodative aftereffects, following 5 sec of adaptation, ranged within several seconds for all three open loop conditions. After adapting for 1 min to a 2-D stimulus, the duration of accommodative aftereffects increased by approximately an order of magnitude for the Maxwellian view and empty field conditions; however, they increased modestly for the dark condition. Tonic aftereffects of accommodation were also stimulated by convergence with base out prism or divergence with base in prism while the accommodative loop was opened. The ratio of open-loop aftereffect amplitude/closed-loop accommodative response to lenses ranged from 0.95 to 0.48, and it became smaller when the accommodative stimulus approached the amplitude of accommodation. The rapid decay of tonic aftereffects of accommodation in darkness was reversable when a visible stimulus was presented while the accommodative loop was opened by Maxwellian view or empty field. Hence, darkness only masked aftereffects that were manifest primarily when there was light stimulation of the retina. The amplitudes of accommodative aftereffects were reciprocally related to the amplitude of the lag of accommodation. During a 2-min adaptation period, accommodative response increased gradually for 30-60 sec as it approached the amplitude of the accommodative stimulus. This resulted in a reduction of accommodative error or lag. Opening the accommodative loop before or after the lag was reduced resulted in a small or large aftereffect of accommodation respectively. Accommodative aftereffects appear to be related to accommodative lag as prism adaptation is related to fixation disparity.

Accommodation, Ocular↗
PubMed2004

Efficient generation of discontinuity-preserving adaptive triangulations from range images.

This paper presents an efficient technique for generating adaptive triangular meshes from range images. The algorithm consists of two stages. First, a user-defined number of points is adaptively sampled from the given range image. Those points are chosen by taking into account the surface shapes represented in the range image in such a way that points tend to group in areas of high curvature and to disperse in low-variation regions. This selection process is done through a noniterative, inherently parallel algorithm in order to gain efficiency. Once the image has been subsampled, the second stage applies a two and one half-dimensional Delaunay triangulation to obtain an initial triangular mesh. To favor the preservation of surface and orientation discontinuities (jump and crease edges) present in the original range image, the aforementioned triangular mesh is iteratively modified by applying an efficient edge flipping technique. Results with real range images show accurate triangular approximations of the given range images with low processing times.

Algorithms↗
PubMed1996

Proliferation markers.

Types of growth include embryonic, fetal, neonatal, juvenile and mature. Until full differentiation is achieved, cells grow through proliferation from progenitor cells. At maturity, the cellular genome is fixed with committed patterns of cell cycle duration and adaptation, ranging from static to renewing type 3. The static cell type cannot proliferate and adapts through hypertrophy. The renewing type continuously proliferates even without stimulus. In all cell types the processes of differentiation and proliferation are mutually exclusive. Cellular kinetics involve (a) the duration of the cell cycle, (b) the birth rate of cells, and (c) the growth rate fractions. The duration of the cell cycle is 2-4 days. All growth factors (GF) exert their influence during G1 phase. Release a GF by one cell type can influence the proliferation of another (= paracrine stimulation). At the end of G1 is the point of highest sensitivity to toxicity. Tumor suppressor genes act here through tyrosine phosphorylation. During S, the cell replicates its chromosomes. During G2 the immune surveillance and DNA damage repair mechanisms operate. Injured cells stay here longer enabling repair of their damaged DNA. Cell division involves both nuclear (mitosis) and cytoplasmic (cytokinesis) phases giving rise to 2 new cells. The cell cycle has 2 checkpoints. The first involves the G1-S transition and the second the G2-M transition. The types of cell cycle inhibition include (a) cycle- and phase-specific inhibition; (b) cycle-and nonphase-specific inhibition; (c) noncycle-and nonphase-specific inhibition, and finally (d) noncycle, nonphase-, and nonorgan-specific inhibition. Proliferation is a circadian process and it is stimulated by a variety of stimuli which include (1) interference with hormonal feedback pathways; (2) inhibition of the tissue trophic activity; (3) sustained presence of antigenic substances; (4) tissue ischemia; (5) changes of conditions luminally or on surfaces of tissues; (6) sustained cytotoxicity; (7) cell death; and (8) surgical resection. Proliferation can be arrested through senescence, apoptosis, injury or even during the development of immune cells. In the past, tissue/cell kinetics have been studied by tritiated thymidine histoautoradiography. Recently, monoclonal antibodies to proliferation-associated antigens, have been successfully employed. These antigens are cycle-associated proteins and include (1) PCNA; (2) p53; (3) Ki67; (4) AGNOR; (5) Statin; and (6) BrdU. Practical examples are given comparing PCNA and BrdU markers from 3 tissues, i.e. liver, glandular stomach, and uterus, across 2 or 3 strains of rats. Mean values of labeling indices are cited. Within the PCNA marker, 2 different clones are compared from the glandular stomach of SD rats of 2 different ages. Gender and across species comparisons are also made. All these comparisons denote that in every study where markers are used (a) there is a need for a concurrent study control group of the same age; (b) there is a need for in-house control data for this particular organ by species, strain, gender and age; (c) there is ancillary assessment of the trophic status of the target tissue; (d) there is a need for at least 2 different time points during assessment; (e) there is a need for such proliferation data prior to commencing the 2 year rodent bioassay; and (f) that PCNA is the most reliable and versatile of all markers used, capable of rendering good results even from archival specimens.

Animals↗
PubMed1979

Nonlinear kernels of the human ERG.

In this paper we examine the use of a symmetric binary random stimulus for eliciting the ERG, and for calculating the first-order and second-order kernels of a nonlinear functional expansion of the response. We show that if the stimulus is represented in a non-dimensional form, then the units in which all kernels are measured are the same as the units used to measure the response, microvolts in the case of the ERG; further, contributions from all kernels to the response can be added without scale factors. We present the first-order and second-order kernels measured for a population of 15 normal subjects in a clinical setting. The measurements were made at various levels of adaptation ranging from photopic to scotopic conditions. The second-order kernels illustrate the processes of rapid adaptation (less than 100 ms) in the retina.

Adult↗
PubMed1991

Short-term nonconjugate adaptation of human saccades to anisometropic spectacles.

It has been demonstrated before that the long-term wearing of anisometropic spectacles may induce nonconjugate adaptations of saccades. Saccades then become different in size in the two eyes. We examined the time-course and the limits of such adaptations of horizontal and vertical saccades during the short-term (1-6 hr) wearing of anisometropic spectacles. After only 1 hr of conditioning to 2 D of anisometropia, the nonconjugate size-adaptations were almost complete along the horizontal meridian. For progressively larger anisometropias (up to 8 D) the adaptative nonconjugacies after 1 hr became also systematically larger. An anisometropia larger than 6 D did not further increase the rate of adaptation during the first 6 hr of conditioning, which suggests that about 6 D of difference in spectacle correction, causing size differences of about 12%, may be the upper limit of the nonconjugate adaptive range of the saccadic subsystem. Post-saccadic drift of horizontal saccades was also adequately changed. In addition, nonconjugate adaptations had developed in smooth-pursuit eye movements. All of these plastic changes persisted during monocular viewing, indicating that the basic programming of these eye movements was changed.

Adaptation, Ocular↗
PubMed2001

Adaptation of distortion product otoacoustic emission in humans.

Previous studies of animals observed a phenomenon of adaptation of distortion product otoacoustic emission (DPOAE) and found that the phenomenon was mediated to a large extent by the medial olivocochlear (MOC) reflex. The present study investigated DPOAE adaptation in humans. The following stimuli were used: f2/f1 = 1.2; f2 = 2, 4, or 5.65 kHz; L2 = 50-65 dB SPL re 20 microPa rms, L1 - L2 = 0-15 dB, where L1 and L2 represent levels of the f1 and f2 tones, respectively; duration of two-tone burst = 5.5 s; interburst gap = 20 or 30 s; number of repetitions = 40 or 64. We analyzed the 2f1 - f2 DPOAE as a function of time using a method of heterodyne envelope detection. The subjects were 20 humans aged from 15 to 54 years (median = 21 years) with normal hearing. We observed that (1) humans exhibited DPOAE adaptation phenomenon; (2) the time course of DPOAE level was characterized by a 2-exponential function; (3) distributions of the fast and slow time constants were well separated with their median values being 69 ms and 1.51 s, respectively; (4) distributions of the magnitudes of the fast and slow adaptation components were largely overlapped with their median values being 0.65 and 0.40 dB, respectively; and (5) the combined magnitude of the adaptation ranged from 0.4 to 3.0 dB with a median of 1.10 dB. To our knowledge, the present study is the first published article to describe adaptation of DPOAE in humans. These results should help advance the basic knowledge of human cochlear mechanics operating under the control of the MOC feedback system and contribute to the development of practical applications such as identifying people at high risk of acoustical injury and a clinical test of the functional status of the MOC system.

Adaptation, Physiological↗
PubMed1987

Chesson strain Plasmodium vivax in Saimiri sciureus boliviensis monkeys.

Nine Saimiri sciureus boliviensis monkeys were inoculated with sporozoites of Plasmodium vivax (Chesson strain) dissected from Anopheles stephensi mosquitoes infected by feeding on blood from infected chimpanzees. The animals were splenectomized 7 days after inoculation. Seven animals developed infections with prepatent periods ranging from 12 to 43 days (mean of 19.6 days). Parasitemias were low during the first 50 days. Maximum parasitemias in 5 animals in which the strain adapted ranged from 10,000 to 46,800 per mm3. Anopheles freeborni mosquitoes were infected by feeding on 4 of the monkeys.

Animals↗
PubMed1995

The dietary adaptations of European Miocene catarrhines.

European Miocene "apes" have been known for nearly a century and a half but their phylogenetic significance is only now becoming apparent with the recent discovery of many relatively complete remains. Some appear to be close in time and morphology to the last common ancestor of modern great apes and humans. The current study is an attempt to reconstruct the diets of these fossils on the basis of quantitative data. Results suggest that these primates varied more greatly in their diets than modern apes, with adaptations ranging from hard-object feeding to soft-object frugivory to folivory.

Adaptation, Physiological↗
PubMed1986

The spatial organization of retinal receptive fields in light and darkness as revealed by the pattern electroretinogram.

The spatial selectivity of the electroretinogram in response to pattern onset-offset stimuli was studied in man at several levels of adaptation ranging from scotopic to photopic levels. Under conditions of rod function the peak of the spatial selectivity based on amplitude measurements of the pattern-onset response occurs at a low spatial frequency. With increasing light adaptation a gradual shift of the selectivity to higher spatial frequencies occurs. This change in the character of the response can be explained by the assumption that antagonistic center-surround retinal receptive fields contribute to the response, which are larger under scotopic than under photopic levels of stimulation.

Darkness↗
PubMed2006

Cerebellar contributions to locomotor adaptations during splitbelt treadmill walking.

Locomotor adaptability ranges from the simple and fast-acting to the complex and long-lasting and is a requirement for successful mobility in an unpredictable environment. Several neural structures, including the spinal cord, brainstem, cerebellum, and motor cortex, have been implicated in the control of various types of locomotor adaptation. However, it is not known which structures control which types of adaptation and the specific mechanisms by which the appropriate adjustments are made. Here, we used a splitbelt treadmill to test cerebellar contributions to two different forms of locomotor adaptation in humans. We found that cerebellar damage does not impair the ability to make reactive feedback-driven motor adaptations, but significantly disrupts predictive feedforward motor adaptations during splitbelt treadmill locomotion. Our results speak to two important aspects of locomotor control. First, we have demonstrated that different levels of locomotor adaptability are clearly dissociable. Second, the cerebellum seems to play an essential role in predictive but not reactive locomotor adjustments. We postulate that reactive adjustments may instead be predominantly controlled by lower neural centers, such as the spinal cord or brainstem.

Adaptation, Physiological↗
PubMed2004

Haematological and biochemical abnormalities in canine blood: frequency and associations in 1022 samples.

Submission of blood samples to referral laboratories is very common in veterinary practice. Internal reference ranges should take into account published ranges adapted to the methods and apparatus used and to the population under consideration. The aim of this study was to examine the results from 1022 consecutive canine blood tests, analysing the frequency and the main associations of abnormalities, and to compare the results in different age groups. Haemograms and serum biochemistry were compared with internal ranges and between age groups: younger than one year, one to eight years and older than eight years. Young dogs exhibited lower numbers of erythrocytes and lower values for haemoglobin concentration and packed cell volume. They also showed higher numbers of lymphocytes and higher concentrations of phosphorus and 71 per cent showed raised alkaline phosphatase. Neutrophilia, hypergammaglobulinaemia andhypoalbuminaemiaoccurred quite frequently in all dogs, and hypoalbuminaemia and hyperphosphataemia were commonly seen in uraemic patients. The simultaneous evaluation of cytolytic and hepatobiliary enzymes allowed better detection of liver damage, since only a very low percentage of dogs had simultaneous increases in all hepatic enzymes.

Animals↗
PubMed1988

Predictive value of screening for different areas of development.

Associations between the results of developmental screening at five ages between 30 weeks and three years and the children's educational and behavioural status in normal primary schools at 6 1/2 to 7 1/2 years were examined in two samples of children living in Dundee and born in 1974 and 1975. In one sample the screening results for 417 children with moderately severe or severe school problems were compared with the screening results for a control group without school problems. Positive associations were found between school problems and motor and adaptive screening test results (from 39-week screening onward), language (from 15 months), preschool behaviour (at 39 weeks and two years) and neurological status (at 39 weeks and three years). In the second sample the questionnaire scores of 570 children known to be suspect on screening were compared with the scores of a control group whose screening results had been considered within the normal range. Adaptive and neurological screening tests provided the best predictors of behaviour problems in school and of educational failure. It is suggested that more thorough developmental and neurological assessments, at less frequent intervals, than is common in most screening programmes would facilitate identification of (and intervention for) preschool neurodevelopmental disability among children at risk of early schooling problems.

Child↗
PubMed2006

Stress dysfunctions as a unifying paradigm for illness: repairing relationships instead of individuals as a new gateway for medicine.

Stress has been implicated as a risk factor for most diseases, but a mechanistic explanation behind such associations remains elusive. As emergent responses to stress, adaptations range from acute responses where extant system capabilities mitigate current stress, to longer-term responses where system plasticity buffers against future stress. The long compendium of human ailments manifests through a much shorter set of symptoms that may operate through the stress axis. We propose a unifying ontology for human illnesses that classifies stress dysfunctions according to types of Darwinian dysfunction - inadequate response with adequate adaptation, inadequate adaptation, inappropriate adaptation, and epiphenomena of adaptation. Examples include cancer as a bystander effect of increased biologic plasticity in response to stress, and infectious illness as a manifestation of mutually escalating stress in an otherwise commensal relationship between hosts and microbes. We explore the contributing role of man-made stresses that have emerged as humans increasingly remodel their environment. Examples include biologic decompensation associated with reliance on technology to buffer stress, and behavioral stress caused by the dislocation of kin networks that promotes illegitimate signaling. Dysfunctional relationships engender stress not only among humans, but also among individual organs; heart failure, renal failure, and carotid stenosis may represent examples of such conditions. If stress dysfunction is the Occam's razor of human illnesses, and derangements in biologic relationships induce stress dysfunctions, then the study of relationships - an incarnation of systems biology - may represent a new gateway for medicine.

Adaptation, Psychological↗
PubMed2000

Treadmill running produces both positive and negative physiological adaptations in Sprague-Dawley rats.

Exercise training produces a vast array of physiological adaptations, ranging from changes in metabolism to muscle mitochondrial biogenesis. Researchers studying the physiological effects of exercise often use animal models that employ forced exercise regimens that include aversive motivation, which could activate the stress response. This study examined the effect of forced treadmill running (8 wk) on several physiological systems that are sensitive to training and stress. Forced treadmill running produced both positive and negative physiological adaptations. Indicative of positive training adaptations, exercised male Sprague-Dawley rats had a decrease in body weight gain and an increase in muscle citrate synthase activity compared with sedentary controls. In contrast, treadmill running also resulted in the potentially negative adaptations of adrenal hypertrophy, thymic involution, decreased serum corticosteroid binding globulin, elevated lymphocyte nitrite concentrations, suppressed lymphocyte proliferation, and suppressed antigen-specific IgM. Such alterations in neuroendocrine tissues and immune responses are commonly associated with chronic stress. Thus treadmill running produces both positive training adaptations and potentially negative adaptations that are indicative of chronic stress. Researchers employing forced activity need to be aware that this type of exercise procedure also produces physiological adaptations indicative of chronic stress and that these changes could potentially impact other measures of interest.

Adaptation, Physiological↗