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The objectives of this study were to describe the lying behavior of primiparous dairy cows under pasture-based systems during the pre- and postcalving period and characterize the association of lying behavior and analytes related to energy metabolism during this period with claw horn disruption lesion development later in lactation. Our convenience sample included 39 primiparous Holstein cows from 3 commercial farms that were assessed for body condition score (BCS; 5-point scale, 0.25-point increments) and had blood collected at wk -3, -2, -1, 1, 2, and 3 relative to calving date. Blood samples were assayed for nonesterified fatty acids, ß-hydroxybutyrate (BHB), and cholesterol concentrations. Electronic data loggers (HOBO Pendant G Acceleration, Onset Computer Corporation, Bourne, MA) recorded lying behavior at 1-min intervals from 3 wk before calving to 3 wk after calving. Starting at 4 wk after calving and until 16 wk after calving, cows were examined for claw lesions at approximately 4-wk intervals. Sole lesions and white line lesions were scored on a 0 to 10 scale. Of the 39 primiparous cows, 19 cows scored 0 at all exams during the entire study period and 20 cows had at least 1 severe lesion (score ≥4) between 8 and 16 wk after calving. Time spent lying before calving averaged 10.3 ± 0.3 h/d, but declined to 7.3 ± 0.3 h/d after calving (least squares means ± standard error). At calving, we noted an increase in the number of lying bouts (12.9 ± 0.45 bouts/d) compared with the pre- and postcalving averages of 11.6 (±0.53) and 9.1 (±0.47) bouts, respectively. Cows that developed claw lesions later in mid lactation spent less time lying down than cows without lesions during wk 3 after calving compared with healthy cows (7.29 ± 0.22 vs. 8.51 ± 0.16 h/d). Lesion cows had fewer lying bouts per day, and these bouts were of longer duration than no-lesion cows after calving. Increased odds of lesion were found to be associated with shorter lying times and fewer number of lying bouts during wk 3 (odds ratio = 1.23). Nonesterified fatty acids (747 ± 58 vs. 990 ± 86.85 µmol/L) and BHB (0.77 ± 0.06 vs. 0.60 ± 0.04 mmol/L) concentrations during wk 1 were greater in cows that developed claw lesions relative to cows that did not develop lesions. The BHB concentrations also remained higher in wk 2 for cows that developed claw lesions (0.63 ± 0.04 vs. 0.46 ± 0.03 mmol/L) compared with cows that did not develop any lesions. Cows that developed lesions experienced greater losses in BCS from wk -3 to 3 than cows without lesions (0.74 ± 0.01 and 0.61 ± 0.01 BCS change, respectively). In summary, changes in lying behavior and energy metabolic status after calving were associated with claw horn disruption lesions in mid-lactation primiparous cows under pasture-based systems.
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Enfermedades de los Bovinos/fisiopatología , Enfermedades del Pie/veterinaria , Pezuñas y Garras/patología , Lactancia/fisiología , Ácido 3-Hidroxibutírico , Animales , Bovinos , Enfermedades de los Bovinos/metabolismo , Metabolismo Energético , Femenino , Enfermedades del Pie/metabolismo , Enfermedades del Pie/fisiopatología , Vivienda para Animales , Cojera Animal/metabolismo , Cojera Animal/fisiopatología , Paridad , EmbarazoRESUMEN
OBJECTIVE: First, to evaluate the outcome of 2 transdiagnostic day treatment programs. A 20-week psychotherapeutic day treatment (PDT) and an activating day treatment (ADT) program delivered in blocks of 4 weeks with a maximum of 24 weeks with respect to depression, anxiety, and hypochondriasis. Second, to explore the impact of cognitive impairment and personality pathology on treatment outcome. METHODS: The course of depression (Inventory of Depressive Symptoms), anxiety (Geriatric Anxiety Inventory), and hypochondriasis (Whitley Index) were evaluated by linear mixed models adjusted for age, sex, level of education, and alcohol usage among 49 patients (mean age 65 years, 67% females) receiving PDT and among 61 patients (mean age 67.1, 61% females) receiving ADT. Pre-post effect-sizes were expressed as Cohen's d. Subsequently, cognitive impairment (no, suspected, established) and personality pathology (DSM-IV criteria as well as the Big Five personality traits) were examined as potential moderators of treatment outcome. RESULTS: Among patients receiving PDT, large improvements were found for depression (d = 1.1) and anxiety (d = 1.2) but not for hypochondriasis (d = 0.0). Patients receiving ADT showed moderate treatment effects for depression (d = 0.6), anxiety (d = 0.6), as well as hypochondriasis (d = 0.6). Personality pathology moderates treatment outcome of neither PDT nor ADT. Cognitive impairment negatively interfered with the course of depressive symptoms among patients receiving PDT. CONCLUSIONS: Transdiagnostic day treatment is promising for older adults with affective disorders with high feasibility.
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Terapia Cognitivo-Conductual/métodos , Trastornos del Humor/terapia , Anciano , Trastornos de Ansiedad/psicología , Trastorno Depresivo/psicología , Femenino , Humanos , Hipocondriasis/psicología , Modelos Lineales , Masculino , Persona de Mediana Edad , Trastornos del Humor/psicología , Personalidad , Factores de RiesgoRESUMEN
Ferroelectric domain walls hold great promise as functional two-dimensional materials because of their unusual electronic properties. Particularly intriguing are the so-called charged walls where a polarity mismatch causes local, diverging electrostatic potentials requiring charge compensation and hence a change in the electronic structure. These walls can exhibit significantly enhanced conductivity and serve as a circuit path. The development of all-domain-wall devices, however, also requires walls with controllable output to emulate electronic nano-components such as diodes and transistors. Here we demonstrate electric-field control of the electronic transport at ferroelectric domain walls. We reversibly switch from resistive to conductive behaviour at charged walls in semiconducting ErMnO3. We relate the transition to the formation-and eventual activation-of an inversion layer that acts as the channel for the charge transport. The findings provide new insight into the domain-wall physics in ferroelectrics and foreshadow the possibility to design elementary digital devices for all-domain-wall circuitry.
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Results of this clinical study on surgical treatment of pressure ulcers at Department of Plastic, Reconstructive and Aesthetic Surgery, Dubrava University Hospital showed that there was no difference between the 2011-2016 and 2003-2008 periods, indicating continuation of good surgical treatment planning and appropriate postoperative care. Despite the smaller number of hospitalized patients in the 2011-2016 period (31 patients and 42 reconstructive procedures), the number of reconstructive procedure was similar to the recent 2003-2008 period (47 patients and 57 reconstructive procedures). The best results of reconstruction of sacral region pressure ulcer were achieved with fasciocutaneous and musculocutaneous flaps. Whenever possible, depending on the extent of the defect, musculocutaneous flaps should be preferred for reconstruction. It is especially suitable for pressure ulcer recurrence. For ischial region reconstruction, good results can be obtained by mobilizing the semimembranosus and/or semitendinosus in defect gap. For trochanteric region, the tensor fascia lata flap is a good choice. For maximal functional and reconstructive results, a multidisciplinary approach in pressure ulcer treatment has the leading role in the modern concept of wound healing. Surgical treatment should always include radical debridement, ostectomy and well planned defect reconstruction. Conservative treatment should be support to surgical treatment with a focus on patient health care and high hygiene measures. In recent years (2011-2016), the usage of better conservative treatment led to reduction of patient hospital stay and surgical treatment of pressure ulcer. Further 'wound care' nurses training in Croatia can lead the trend towards advanced practice nursing in pressure ulcer prevention and conservative treatment.
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Desbridamiento/métodos , Procedimientos de Cirugía Plástica , Úlcera por Presión , Cuidados de la Piel , Cirugía Plástica , Adulto , Croacia/epidemiología , Desbridamiento/estadística & datos numéricos , Femenino , Hospitales Universitarios , Humanos , Masculino , Persona de Mediana Edad , Úlcera por Presión/epidemiología , Úlcera por Presión/cirugía , Mejoramiento de la Calidad , Procedimientos de Cirugía Plástica/métodos , Procedimientos de Cirugía Plástica/estadística & datos numéricos , Procedimientos de Cirugía Plástica/tendencias , Recurrencia , Cuidados de la Piel/métodos , Cuidados de la Piel/normas , Cuidados de la Piel/tendencias , Cirugía Plástica/métodos , Cirugía Plástica/tendencias , Cicatrización de HeridasAsunto(s)
Acidosis/inducido químicamente , Acidosis/patología , Esófago/efectos de los fármacos , Esófago/lesiones , Esófago/patología , Mucosa Gástrica/efectos de los fármacos , Mucosa Gástrica/lesiones , Mucosa Gástrica/patología , Ácido Clorhídrico/envenenamiento , Úlcera Péptica Perforada/inducido químicamente , Úlcera Péptica Perforada/patología , Úlcera Gástrica/inducido químicamente , Úlcera Gástrica/patología , Intento de Suicidio , Abdomen Agudo/inducido químicamente , Abdomen Agudo/patología , Abdomen Agudo/cirugía , Acidosis/cirugía , Quemaduras Químicas , Esofagectomía , Esófago/cirugía , Resultado Fatal , Femenino , Gastrectomía , Mucosa Gástrica/cirugía , Humanos , Persona de Mediana Edad , Necrosis , Úlcera Péptica Perforada/cirugía , Peritonitis/inducido químicamente , Peritonitis/patología , Peritonitis/cirugía , Bazo/efectos de los fármacos , Bazo/patología , Esplenectomía , Úlcera Gástrica/cirugíaRESUMEN
Transport properties of a multiscale carbonate rock are predicted from pore scale models, reconstructed using a continuum geometrical modeling technique. The method combines crystallite information from two-dimensional high-resolution images with sedimentary correlations from a three-dimensional low-resolution microcomputed tomography ( micro-CT) image to produce a rock sample with calibrated porosity, structural correlation, and transport properties at arbitrary resolutions. Synthetic micro-CT images of the reconstructed model match well with experimental micro-CT images at different resolutions, making it possible to predict physical transport parameters at higher resolutions.
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A multiscale model for the diagenesis of carbonate rocks is proposed. It captures important pore scale characteristics of carbonate rocks: wide range of length scales in the pore diameters; large variability in the permeability; and strong dependence of the geometrical and transport parameters on the resolution. A pore scale microstructure of an oolithic dolostone with generic diagenetic features is successfully generated. The continuum representation of a reconstructed cubic sample of side length 2mm contains roughly 42 x 10{6} crystallites and pore diameters varying over many decades. Petrophysical parameters are computed on discretized samples of sizes up to 1000{3}. The model can be easily adapted to represent the multiscale microstructure of a wide variety of carbonate rocks.
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The current-induced dissipation in YBa(2)Cu(3)O(7-delta) grain boundary tunnel junctions has been measured between 4.2 and 300 K. It is found that the resistance of 45 degrees (100)/(110) junctions decreases linearly by a factor of 4 when their temperature is increased from 100 to 300 K. At the superconducting transition temperature T(c) the grain boundary resistance of the normal state and of the superconducting state extrapolates to the same value.
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We measured the influence of gravitoinertial force (GIF) magnitude and direction on head-centric auditory localization to determine whether a true audiogravic illusion exists. In experiment 1, supine subjects adjusted computer-generated dichotic stimuli until they heard a fused sound straight ahead in the midsagittal plane of the head under a variety of GIF conditions generated in a slow-rotation room. The dichotic stimuli were constructed by convolving broadband noise with head-related transfer function pairs that model the acoustic filtering at the listener's ears. These stimuli give rise to the perception of externally localized sounds. When the GIF was increased from 1 to 2 g and rotated 60 degrees rightward relative to the head and body, subjects on average set an acoustic stimulus 7.3 degrees right of their head's median plane to hear it as straight ahead. When the GIF was doubled and rotated 60 degrees leftward, subjects set the sound 6.8 degrees leftward of baseline values to hear it as centered. In experiment 2, increasing the GIF in the median plane of the supine body to 2 g did not influence auditory localization. In experiment 3, tilts up to 75 degrees of the supine body relative to the normal 1 g GIF led to small shifts, 1--2 degrees, of auditory setting toward the up ear to maintain a head-centered sound localization. These results show that head-centric auditory localization is affected by azimuthal rotation and increase in magnitude of the GIF and demonstrate that an audiogravic illusion exists. Sound localization is shifted in the direction opposite GIF rotation by an amount related to the magnitude of the GIF and its angular deviation relative to the median plane.
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Sensación de Gravedad/fisiología , Localización de Sonidos/fisiología , Adulto , Aviación , Femenino , Humanos , Ilusiones/fisiología , Colículos Inferiores/fisiología , Masculino , Persona de Mediana Edad , Orientación/fisiología , RotaciónRESUMEN
A 77-mer RNA with the sequence of Eschlerichia coli tRNA(Asp) has been chemically synthesised using standard automated phosphoramidite chemistry with the coupling reagent 4,5-dicyanoimidazole (DCI). The synthesis was carried out on a 1000 A CPG-column and. after deprotection and gel purification, a yield of about 7 mmol with a purity of > 95% was reproducibly obtained. By comparing automated synthesis of the 77-mer RNA using 1H-tetrazole and DCI as activator, DCI is advantageous in producing longer RNAs. However, for shorter RNAs ( <40 mer) no difference could be observed. In addition to the all-ribo tRNA(Asp) carrying the wild-type sequence, two variants were synthesised, one with a single C to G48 mutation and the second with a 2'-deoxy modification at C48. The three tRNAs were tested for their aminoacylation efficiency and high affinity binding to E. coli RNase P RNA. The results demonstrate that chemically synthesised 77-mer oligoribonucleotides can be successfully used for structure function studies.
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Escherichia coli/genética , Oligorribonucleótidos/síntesis química , ARN de Transferencia de Aspártico/química , ARN de Transferencia/síntesis química , Imidazoles , Cinética , Mutación , Oligorribonucleótidos/genética , ARN de Transferencia de Aspártico/genéticaRESUMEN
While it is now established that astigmatism is more prevalent in infants and young children than in the adult population, little is known about the functional significance of this astigmatism, especially its role, if any, in emmetropization and the development of myopia. Manifest refractions (mean of 16 per subject) were obtained from 245 subjects starting in the first year, with 6-23 years of regular follow-up. Results showed that infantile astigmatism is associated with increased astigmatism and myopia during the school years. Two possible mechanisms underlying this association are discussed: (1) infantile astigmatism disrupts focusing mechanisms; and (2) ocular growth induces astigmatism and myopia.
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Astigmatismo/complicaciones , Miopía/etiología , Adolescente , Envejecimiento/fisiología , Niño , Preescolar , Ojo/crecimiento & desarrollo , Femenino , Estudios de Seguimiento , Humanos , Lactante , Masculino , Refracción Ocular/fisiologíaAsunto(s)
Iluminación , Miopía/etiología , Adolescente , Adulto , Niño , Preescolar , Familia , Humanos , Lactante , Cuidado del Lactante , Estudios Longitudinales , Miopía/genética , PadresRESUMEN
Precursor tRNA (ptRNA) substrates carrying a single Rp or Sp-phosphorothioate modification at the RNase P cleavage site were used as tools to study the cleavage mechanism of RNase P RNA from Bacillus subtilis. Both the Sp and the Rp-diastereomer reduced the rate of processing at least 10(4)-fold under conditions where the chemical step is essentially rate-limiting. Neither the Rp nor the Sp-phosphorothioate modification affected ptRNA ground state binding to B. subtilis RNase P RNA. Processing of the Rp-diastereomeric ptRNA could be restored in the presence of Mn2+or Cd2+, demonstrating direct metal ion coordination to the pro -Rp oxygen during catalysis. With Cd2+, processing required the presence of another metal ion, such as Ca2+or Mg2+, to mediate substrate binding. This is in contrast to Escherichia coli RNase P RNA, which promotes cleavage of Rp-diastereomeric ptRNA in the presence of Cd2+as the sole divalent metal ion. Analysis of [Cd2+]-dependent processing of the Rp-diastereomeric substrate by B. subtilis RNase P RNA was consistent with the involvement of at least two metal ions in catalysis. The presence of two catalytic metal ion binding sites is also supported by the inhibition mode of Ca2+on cleavage of unmodified ptRNA. In the presence of an Sp-phosphorothioate modification at the scissile bond, neither Mn2+nor Cd2+were able to restore significant cleavage at this location. Instead, the ribozyme promotes cleavage at the neighboring unmodified phosphodiester with low efficiency. Unaffected ground state binding of the Sp-diastereomeric ptRNA but a >/=10(4)-fold reduced hydrolysis rate may indicate a crucial role of the pro -Sp oxygen in transition state stabilization or may be attributed to steric exclusion of catalytic metal ions. Based on our comparative analyses of B. subtilis and E. coli RNase P RNA, each representing the main structural subtypes of bacterial RNase P RNA, common features in terms of active site constraints and role of catalytic metal ions can now be formulated for bacterial RNase P RNAs. On the other hand, substantial and unexpected differences with respect to the overall metal ion requirements and tRNA binding modes have been observed for the two catalytic RNAs.
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Bacillus subtilis/enzimología , Endorribonucleasas/metabolismo , Proteínas de Escherichia coli , Metales/farmacología , ARN Catalítico/metabolismo , Bacillus subtilis/genética , Secuencia de Bases , Sitios de Unión , Cadmio/farmacología , Calcio/farmacología , Catálisis/efectos de los fármacos , Endorribonucleasas/genética , Escherichia coli/enzimología , Escherichia coli/genética , Concentración de Iones de Hidrógeno , Hidrólisis/efectos de los fármacos , Magnesio/farmacología , Manganeso/farmacología , Mutación , Precursores del ARN/química , Precursores del ARN/genética , Precursores del ARN/metabolismo , ARN Bacteriano/química , ARN Bacteriano/genética , ARN Bacteriano/metabolismo , ARN Catalítico/genética , Ribonucleasa P , Ribonucleoproteínas/genética , Ribonucleoproteínas/metabolismo , EstereoisomerismoRESUMEN
The literature on myopigenesis suggests an active emmetropization mechanism regulated by optical defocus. The strongest evidence comes from compensatory ocular growth in response to lens-induced defocus in different species of animals. Based on these results, it has been suggested that, however useful, spectacle intervention for the optical correction of human myopia would lead to its exacerbation. The present study seeks to evaluate the progression of juvenile-onset myopia in children differentiated by their lens wear patterns. Data from 43 myopes from our longitudinal study of refraction were evaluated, with myopia defined as a spherical equivalent of at least -0.50 D. Refractions were obtained in the laboratory by noncycloplegic retinoscopy performed by one experienced optometrist at regular intervals. Information regarding the subjects' prescription lens-wearing history was obtained from the subjects and their eye care providers. Based on their wearing patterns, subjects were divided into four categories: (1) full-time wearers; (2) myopes who switched from distance to full-time wear; (3) distance wearers; and (4) nonwearers. Exponential functions were fit to the individual refraction data. The age of onset of myopia, the mean myopia at onset of spectacle wear, and the refractive shift over a period of at least 3 years were derived from these fits. Results show that the 3-year refractive shifts are not significantly different among the four groups. A comparison of the extreme conditions, i.e., full-time vs. nonwear categories, also revealed no significant difference when the data were corrected for age effects despite the fact that the nonwearers exhibited an age-adjusted 3-year progression approximately one-half that of the full-time wearers. In summary, the present study failed to demonstrate any overall effects of spectacle intervention on the progression of human myopia. Further investigation using a larger sample is warranted.
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Anteojos , Miopía/prevención & control , Edad de Inicio , Niño , Progresión de la Enfermedad , Femenino , Estudios de Seguimiento , Humanos , Masculino , Miopía/epidemiología , Miopía/fisiopatología , Prevalencia , Refracción Ocular , Resultado del TratamientoRESUMEN
Head-related transfer functions (HRTFs) were used to create spatialized stimuli for presentation through earphones. Subjects performed forced-choice, identification tests during which allowed response directions were indicated visually. In each experimental session, subjects were first presented with auditory stimuli in which the stimulus HRTFs corresponded to the allowed response directions. The correspondence between the HRTFs used to generate the stimuli and the directions was then changed so that response directions no longer corresponded to the HRTFs in the natural way. Feedback was used to train subjects as to which spatial cues corresponded to which of the allowed responses. Finally, the normal correspondence between direction and HRTFs was reinstated. This basic experimental paradigm was used to explore the effects of the type of feedback provided, the complexity of the stimulated acoustic scene, the number of allowed response positions, and the magnitude of the HRTF transformation subjects had to learn. Data showed that (1) although subjects may not adapt completely to a new relationship between physical stimuli and direction, response bias decreases substantially with training, and (2) the ability to resolve different HRTFs depends both on the stimuli presented and on the state of adaptation of the subject.
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Percepción Auditiva/fisiología , Señales (Psicología) , Localización de Sonidos/fisiología , Adolescente , Adulto , HumanosRESUMEN
A series of experiments was performed in which subjects were trained to interpret auditory localization cues arising from locations different from their normal spatial positions. The exact pattern of mean response to these alterations (as a function of time) was examined in order to begin to develop a quantitative model of adaptation. Mean responses were roughly proportional to the normal position associated with the localization cues presented. As subjects adapted, the best-fit slope (relating mean response and normal position) changed roughly exponentially with time. The exponential rate and adaptation asymptote were found for each subject in each experiment, as well as the rate and asymptote of readaptation to normal cues. The rate of adaptation does not show any statistical dependence on experimental conditions; however, the asymptote of the best-fit slope varied with the strength of the transformation used in each experiment. This result is consistent with the hypothesis that subjects cannot adapt to a nonlinear transformation of auditory localization cues, but instead adapt to a linear approximation of the transformation. Over time, performance changes exponentially towards the best-fit linear approximation for the transformation used in a particular experiment, and the rate of this adaptation does not depend upon the transformation employed.
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Percepción Auditiva/fisiología , Señales (Psicología) , Localización de Sonidos/fisiología , Humanos , Modelos Biológicos , Factores de TiempoRESUMEN
PURPOSE: This study examined changes in contrast sensitivity, the location of the peak of the contrast sensitivity function (CSF), and the shape of the function from infancy to adulthood. METHODS: Contrast thresholds were obtained using behavioral methods, preferential looking for infants, and operant techniques for older children and adults, with the same stimuli for all ages. RESULTS: Contrast sensitivity at the peak improved almost two log units from infancy to adulthood. Much of the shift in the peak to higher spatial frequencies occurred in infancy. Sensitivity was not yet at adult levels at 8 years of age. CONCLUSIONS: The reduction in contrast sensitivity at the lowest frequency between 2 and 4 months of age suggests an increase in lateral inhibition during early infancy. Contrast sensitivity at the peak increased by two log units from then until adulthood.
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Envejecimiento/fisiología , Sensibilidad de Contraste/fisiología , Percepción Espacial/fisiología , Adolescente , Adulto , Niño , Preescolar , Femenino , Humanos , Lactante , Recién Nacido , Masculino , PsicofísicaRESUMEN
PURPOSE: Lessened acuity for oblique contours as compared with horizontal and vertical contours, the oblique effect, is characteristic of humans and animals. The magnitude of the oblique effect in humans varies with ethnic origin. Three experiments were performed to determine the source and extent of this variation in Chinese and Caucasian subjects. METHODS AND RESULTS: Experiment I. Acuity for vertical and oblique gratings was measured in Chinese infants with a preferential looking technique. The development of visual acuity for Chinese infants was found to be strikingly similar to that reported for Caucasian infants. For infants of both races at about 1 year of age, the magnitude of the oblique effect was about 1 octave. Experiment II. Acuity for main-axis (horizontal and vertical) and oblique gratings was measured in Chinese and Caucasian adults. The oblique effect in Chinese subjects was significantly smaller than in Caucasian subjects. The Chinese also had significantly better acuity for oblique gratings, but not for main-axis gratings. Experiment III. To determine whether differential sensitivity to main-axis and oblique-axis gratings extends to suprathreshold spatial frequencies, contrast sensitivity for four orientations at each of five spatial frequencies was assessed in Chinese and Caucasian adults. There were no significant differences in contrast sensitivity between Chinese and Caucasian subjects at any spatial frequency. The differential sensitivity increased with increasing spatial frequency for both ethnic groups. CONCLUSION: The difference in the magnitudes of the oblique effect in Chinese and Caucasian subjects appears in acuity thresholds in adults, and may result solely from the Chinese having better acuity for obliquely oriented gratings.
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Agudeza Visual/fisiología , Adolescente , Adulto , Asiático , China/etnología , Sensibilidad de Contraste/fisiología , Humanos , Lactante , Persona de Mediana Edad , Percepción Visual/fisiología , Población BlancaRESUMEN
Previously we reported that recently myopic children accommodated insufficiently to blur induced by negative lenses. The purpose of the present study was to relate changes in blur-driven accommodation to myopia development in children. Refractive errors and the accommodation response function (ARF) were measured in 23 myopic and 40 emmetropic children on two occasions separated by periods ranging from 6 to 12 months. Repeated measures of accommodation were made with a Canon R-1 autorefractor while negative lenses of increasing power were placed in front of the child's right eye viewing 20/100 letters at 4 m. Concomitant changes in refractive error and in accommodative function over periods of 6-12 months were found to be highly correlated in myopes (r = 0.77) but not in emmetropes (r = 0.09).
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Acomodación Ocular/fisiología , Miopía/fisiopatología , Adolescente , Animales , Niño , Humanos , Lentes , Factores de TiempoRESUMEN
A link between changes in tonic accommodation (TA) produced by sustained near work and the development of adult-onset myopia has been suggested in studies of young adults. Measures of TA before and after near work have been lacking in children of school age, which is the most susceptible period for the development and progression of juvenile-onset myopia. In the present study accommodation was measured in 87 children, aged 7 to 16 years, before and after 15 minutes of video game playing. All children were refracted before testing and wore optical correction during measures of accommodation with a Canon R1 autorefractor. Most children showed initial values of TA (far focus minus dark focus) between 0.0 and 1.0 D, with a mean of 0.68 D. Grouped by refractive status, the myopic children initially showed 0.30 D of TA, while the emmetropic children showed 0.75 D and the hyperopic children showed 0.94 D. After playing the video game, TA of the myopes increased by 1.15 D, compared to smaller increases for the emmetropes (0.68 D) and hyperopes (0.24 D). Comparable values have been obtained from young adults. These results indicate that the smallest initial values of TA and the largest inward shifts in TA are found during the period of acquisition and progression of myopia, regardless of age.