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1.
Artigo em Inglês | MEDLINE | ID: mdl-38717285

RESUMO

BACKGROUND: Response to biologics in psoriasis varies in real-world settings. Serum biomarkers could aid biologic selection and dose modifications to improve patient outcomes while encouraging cost-effective care. OBJECTIVES: To explore the exposure-response relationship for guselkumab (GUS), to define a GUS concentration target for optimal response and to evaluate the potential of serum protein levels as predictive biomarker candidates. METHODS: This is a prospective, multicentric, cohort study in psoriasis patients treated with GUS. Serum GUS trough concentrations (TCs) collected at multiple timepoints were measured using an in-house immunoassay. Next, proximity extension assay technology (Target 96 Inflammation Panel Olink®) was used to measure serum protein levels in a subcohort including 38 GUS patients (week 0 and week 4), six psoriasis patients naive for systemic treatment and four healthy controls. RESULTS: Seventy-five patients participated and 400 samples were collected. Guselkumab TCs and clinical response were correlated at week 4, week 12 and in steady-state (≥20 weeks). Optimal responders (Psoriasis Area and Severity Index [PASI] ≤ 2) had significantly higher TCs than suboptimal responders from week 4 onwards in treatment. An optimal steady-state TC of 1.6 µg/mL was defined. Although TC and absolute PASI were lower and worse, respectively, in patients weighing ≥90 kg, clinical outcomes referred to desirable to excellent PASI ranges. Therefore, we do not recommend systematically higher GUS doses in obese patients. We could not reveal early differentially expressed proteins to distinguish future optimal from suboptimal responders. CONCLUSIONS: We demonstrated an exposure-response relationship for GUS and an optimal steady-state TC of 1.6 µg/mL in real-world psoriasis patients. Hereby, we deliver more evidence that therapeutic drug monitoring poses a promising strategy in optimizing GUS treatment. No biomarker candidates were identified through serum proteomics. We propose protein screening should be repeated in larger cohorts to continue the quest for predictive biomarkers.

2.
J Eur Acad Dermatol Venereol ; 38(1): 31-41, 2024 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-37818828

RESUMO

Treating atopic dermatitis (AD) in pregnant or breastfeeding women, and in women and men with AD aspiring to be parents is difficult and characterized by uncertainty, as evidence to inform decision-making on systemic anti-inflammatory treatment is limited. This project mapped consensus across dermatologists, obstetricians and patients in Northwestern Europe to build practical advice for managing AD with systemic anti-inflammatory treatment in men and women of reproductive age. Twenty-one individuals (sixteen dermatologists, two obstetricians and three patients) participated in a two-round Delphi process. Full consensus was reached on 32 statements, partial consensus on four statements and no consensus on four statements. Cyclosporine A was the first-choice long-term systemic AD treatment for women preconception, during pregnancy and when breastfeeding, with short-course prednisolone for flare management. No consensus was reached on second-choice systemics preconception or during pregnancy, although during breastfeeding dupilumab and azathioprine were deemed suitable. It may be appropriate to discuss continuing an existing systemic AD medication with a woman if it provides good disease control and its benefits in pregnancy outweigh its risks. Janus kinase (JAK) inhibitors, methotrexate and mycophenolate mofetil should be avoided by women during preconception, pregnancy and breastfeeding, with medication-specific washout periods advised. For men preconception: cyclosporine A, azathioprine, dupilumab and corticosteroids are appropriate; a 3-month washout prior to conception is desirable for methotrexate and mycophenolate mofetil; there was no consensus on JAK inhibitors. Patient and clinician education on appropriate (and inappropriate) AD treatments for use in pregnancy is vital. A shared-care framework for interdisciplinary management of AD patients is advocated and outlined. This consensus provides interdisciplinary clinical guidance to clinicians who care for patients with AD before, during and after pregnancy. While systemic AD medications are used uncommonly in this patient group, considerations in this article may help patients with severe refractory AD.


Assuntos
Ciclosporina , Dermatite Atópica , Gravidez , Masculino , Humanos , Feminino , Ciclosporina/uso terapêutico , Metotrexato/uso terapêutico , Aleitamento Materno , Dermatite Atópica/tratamento farmacológico , Azatioprina/uso terapêutico , Ácido Micofenólico/uso terapêutico , Consenso , Anti-Inflamatórios/uso terapêutico
3.
J Eur Acad Dermatol Venereol ; 36 Suppl 4: 3-11, 2022 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-35174562

RESUMO

BACKGROUND: Chronic cutaneous pain has a substantial negative impact on quality of life (QoL). Dermo-cosmetics can support therapies for treatment of chronic skin diseases, providing symptomatic relief from chronic cutaneous pain and improved QoL. OBJECTIVES: To assess the global tolerance and efficacy of a dermo-cosmetic spray containing Rhealba® Oat Plantlet and Uncaria tomentosa extracts in reducing cutaneous pain when used as a monotherapy or in association with drug or dermo-cosmetic treatments in patients with an underlying skin pathology. METHODS: Patients aged ≥1 month with a cutaneous pain level ≥3 and an underlying skin pathology were provided with the spray to use up to six times daily for 6-8 weeks. Immediate effect on cutaneous pain and patient satisfaction were assessed after the first application. Global efficacy and tolerance, reduction in symptoms, improvement in QoL, pain reduction and patient overall satisfaction were assessed after 6-8 weeks. RESULTS: Immediately after the first application, significant reductions in cutaneous pain were observed across all age groups (P < 0.0001), with 94% of patients reporting a reduction in pain. After 6-8 weeks, global tolerance was rated 'very good' or 'good' for 97% of patients, and the spray was efficacious in 95% of patients. Patient satisfaction with the efficacy of the spray was 95%. QoL scores improved in 86% and 94% of patients aged ≥12 and <12 years, respectively. Findings were similar across underlying pathology and therapy types (monotherapy or in association with another therapy). CONCLUSIONS: The spray was well-tolerated and efficacious in providing symptom relief in patients with mild-to-moderate cutaneous pain, irrespective of the underlying pathology or therapy type.


Assuntos
Unha-de-Gato , Cosméticos , Avena , Criança , Humanos , Recém-Nascido , Dor/tratamento farmacológico , Extratos Vegetais/uso terapêutico , Qualidade de Vida
4.
J Eur Acad Dermatol Venereol ; 34(1): 127-134, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31099916

RESUMO

BACKGROUND: Chronic spontaneous urticaria (CSU) is characterized by the repeated occurrence of persistent hives and/or angioedema for ≥6 weeks, without specific external stimuli. H1 -antihistamines have long been the standard of care of CSU, but many patients remain uncontrolled even at 4× the approved dose. Add-on therapy with omalizumab has proven effective in clinical trials, but little is known about omalizumab treatment in Belgium. OBJECTIVE: To collect real-world clinical data on omalizumab treatment in adults with CSU in Belgium. METHODS: This was an observational, retrospective chart review of adults with CSU, who initiated omalizumab treatment between August 2014 and December 2016 (maximum 28 months follow-up). RESULTS: In total, 235 patients were included (median time from symptom onset to diagnosis, 5.4 months; median time from diagnosis to commencing omalizumab, 6.7 months). Treatments used before/after commencing omalizumab did not always adhere to guidelines; many patients (26.4%/11.1%) received first-generation H1 -antihistamines, while 20.4% used omalizumab monotherapy after initiating treatment. The mean interval between omalizumab administrations was 4.8 (SD 1.7) weeks; 67.8% of patients had ≥1 interval prolongation and/or shortening. Mean baseline 7-day Urticaria Activity Score (UAS7) was 32.0 (SD 6.05); this improved to 12.6 (SD 11.2) after 1 month of omalizumab. About 67.2% of patients reached UAS7 ≤ 6 (well controlled) during the study. A total of 87 patients stopped omalizumab and never restarted before the end of the observation period; the most prevalent reason was remission of symptoms (49.4% of patients), followed by lack of effect (12.6%), lost to follow-up (6.9%) and adverse events (3.4%). Headache was the most common adverse event (n = 8/82). No anaphylaxis was reported. CONCLUSIONS: This study revealed that patients initiated on omalizumab in Belgium had severe CSU at baseline, and showed substantial improvements after 1 month of treatment. Greater adherence to the prescription of guideline-recommended medications is needed for the treatment of CSU.


Assuntos
Antialérgicos/uso terapêutico , Urticária Crônica/tratamento farmacológico , Omalizumab/uso terapêutico , Adulto , Bélgica , Esquema de Medicação , Feminino , Antagonistas dos Receptores Histamínicos/uso terapêutico , Humanos , Masculino , Adesão à Medicação , Pessoa de Meia-Idade , Estudos Retrospectivos , Resultado do Tratamento
5.
Acta Chir Belg ; 114(3): 212-4, 2014.
Artigo em Inglês | MEDLINE | ID: mdl-25102714

RESUMO

A 74-year-old woman with known euthyroid multinodular retrosternal goiter necessitated an urgent intubation at home, due to acute respiratory distress evoked by tracheal compression. Extubation after a few days failed, and she underwent an urgent total thyroidectomy. During postoperative extubation the patient developed suddenly unilateral facial flushing and sweating at the left side, without ptosis of the left levator palpebrae superioris. These symptoms persisted during the next 24 hours. The skin at the right side of the face remained uninvolved. In the early postoperative period this appearance recurred at moments of emotions, exercise or heat. Beside this, the patient had a normal recovery. Six weeks later this reaction couldn't be provoked anymore. 'Harlequin' syndrome (unilateral facial flushing and sweating) is caused by a lesion of the controlateral sympathetic chain at the levels T2 and T3. It is unknown if the sweating and vasodilation at the "healthy" side is normal or if it is a reaction of hyperactivity.


Assuntos
Rubor/etiologia , Bócio Nodular/cirurgia , Complicações Pós-Operatórias , Sudorese , Tireoidectomia , Idoso , Extubação , Obstrução das Vias Respiratórias/etiologia , Obstrução das Vias Respiratórias/terapia , Emoções , Exercício Físico , Feminino , Bócio Nodular/complicações , Temperatura Alta , Humanos , Intubação Gastrointestinal , Síndrome
6.
Acta Gastroenterol Belg ; 86(3): 499-501, 2023.
Artigo em Inglês | MEDLINE | ID: mdl-37814569

RESUMO

Adenocarcinomas of the ampulla of Vater represent only 0.2% of all gastrointestinal cancers. Due to the low incidence no large clinical trials evaluating efficacy of treatments are available. Adjuvant therapy is often administered in patients with stage IB or higher. Oxaliplatin is considered as an effective and well tolerated therapeutic option. Adverse events associated with this therapy include cardio-, neuro-, nephrotoxicity and myelosuppression. Previously granulomatous pulmonary and liver manifestations have been described in oxaliplatin-based chemotherapy. In this report peritoneal manifestation of granulomatous disease associated with oxaliplatin is described for the first time. Sarcoidlike reactions may be misinterpreted as tumour progression or metastatic disease, and may consequently result in over-treatment.


Assuntos
Adenocarcinoma , Ampola Hepatopancreática , Neoplasias do Ducto Colédoco , Doenças Peritoneais , Humanos , Oxaliplatina/efeitos adversos , Ampola Hepatopancreática/patologia , Adenocarcinoma/patologia , Neoplasias do Ducto Colédoco/tratamento farmacológico , Neoplasias do Ducto Colédoco/etiologia , Neoplasias do Ducto Colédoco/patologia , Protocolos de Quimioterapia Combinada Antineoplásica/efeitos adversos
7.
Science ; 244(4902): 354-6, 1989 Apr 21.
Artigo em Inglês | MEDLINE | ID: mdl-2711186

RESUMO

The incremental threshold of the isolated rod visual system is believed, under certain conditions, to obey Weber's law (that is, to increase in direct proportion to the intensity of the background). This relation was tested at several background wavelengths, over an intensity range for which the target was seen only by the rods. Although the slope on long-wavelength background approximates unity (that is, Weber's law on log-log coordinates), it averages less than 0.8 on short- and middle-wavelength backgrounds. This is the same value as that found for the thresholds of a typical, complete achromat--who lacks cone vision--regardless of background wavelength. These results force the conclusion that Weber's law for incremental threshold detection is achieved not by the rods alone but only by the rods acting together with the cones.


Assuntos
Células Fotorreceptoras/fisiologia , Visão Ocular/fisiologia , Adaptação à Escuridão , Humanos , Luz
8.
Mitochondrion ; 36: 138-149, 2017 09.
Artigo em Inglês | MEDLINE | ID: mdl-28729193

RESUMO

Leber inherited optic neuropathy (LHON) is characterized by subacute bilateral loss of central vision due to dysfunction and loss of retinal ganglion cells (RGCs). Comprehensive visual electrophysiological investigations (including pattern reversal visual evoked potentials, pattern electroretinography and the photopic negative response) performed on 13 patients with acute and chronic LHON indicate early impairment of RGC cell body function and severe axonal dysfunction. Temporal, spatial and chromatic psychophysical tests performed on 7 patients with acute LHON and 4 patients with chronic LHON suggest severe involvement or loss of the midget, parasol and bistratified RGCs associated with all three principal visual pathways.


Assuntos
Atrofia Óptica Hereditária de Leber/patologia , Células Ganglionares da Retina/patologia , Vias Visuais/patologia , Adolescente , Adulto , Criança , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Estudos Prospectivos , Adulto Jovem
9.
Trends Neurosci ; 22(11): 497-504, 1999 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-10529817

RESUMO

Anatomical and physiological studies of the mammalian retina have revealed two primary pathways available for the transmission of rod signals to the ganglion cells: one via ON rod bipolars, amacrine II cells, and ON and OFF cone bipolars, which is exquisitely designed for the transmission of single-photon absorption events; and a second via rod-cone gap junctions, and ON and OFF cone bipolars, which is designed for the transmission of multiple photon-absorption events at higher light levels. Psychophysical and electroretinographic (ERG) studies in normal observers and in two rare types of observer, who are devoid of either rod or cone function, support an analogous duality in the human visual system, the clearest signature of which is a loss of flicker visibility and ERG amplitude at frequencies near 15 Hz that results from destructive interference between sensitive 'slow' and insensitive 'fast' rod signals. The slow rod signal is most probably derived from the ON rod bipolar pathway and the fast signal from the rod-cone gap junction and cone pathways. Evidence has emerged recently for a third, insensitive rod pathway between rods and OFF cone bipolars, but it has so far only been observed clearly in rodents.


Assuntos
Células Fotorreceptoras Retinianas Bastonetes/fisiologia , Visão Ocular/fisiologia , Vias Visuais/fisiologia , Eletrofisiologia , Humanos , Psicofísica/métodos
10.
Hum Immunol ; 51(1): 32-40, 1996 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-8911995

RESUMO

The polygenic predisposition to RA is conferred particularly by disease susceptibility sequences in the HVR3 of HLA DRB1 present in those subtypes of DR4 and DR1 that are associated with RA. The aim of this study was to examine predisposing interactions between genes encoding HLA and immunoglobulin molecules. Accordingly, we compared the genetic background of 114 Australian patients with RA with that of Australian controls of similar ethnic background. We identified HLA-A, B, and DR phenotypes serologically, HLA-DR, DQ alleles, and subtypes of DR4 by DNA typing, and Gm allogenotypes and immunoglobulin switch region polymorphisms by RFLP. For the subjects with RA, we confirmed previously reported observations that included an excess of females, 71%, a high frequency of HLA types DR4 or DR1 of 77% versus controls 47%, and a high frequency of the HVR3 susceptibility sequences of 76%, with 24% homozygous, and 52% heterozygous for the sequences. We observed other genetic correlations in RA that included increases in frequencies of DR4 in males, DR1 in females, the class I specificity HLA-B27 overall but more particularly in females, 24% in females, versus 5% of controls, HLA-DQB1*0302 (DQ8) in DR4*0401-positive patients, and the Gm allogenotype 1,2,3;23 +/- ; 5,10, 15% of patients versus 4% of controls. Examination of switch region genes gave no evidence of differences in the polymorphisms distributions. Thus, the major genetic risks for RA that are conferred by female gender and the HVR3 of HLA DRB1 are modulated by interactions between gender and HLA class I and class II alleles, and the Gm allogenotype.


Assuntos
Artrite Reumatoide/genética , Genes de Imunoglobulinas , Genes MHC Classe I , Antígenos HLA-DR/genética , Adulto , Idoso , Idoso de 80 Anos ou mais , Alelos , Artrite Reumatoide/imunologia , Feminino , Genótipo , Antígenos HLA-DQ/genética , Cadeias HLA-DRB1 , Humanos , Masculino , Pessoa de Meia-Idade , Fatores Sexuais
11.
Curr Med Res Opin ; 6(7): 445-8, 1980.
Artigo em Inglês | MEDLINE | ID: mdl-6988172

RESUMO

A double-blind trial was carried out in 24 patients with acute gout to compare the efficacy and tolerance of feprazone, a non-steroidal anti-inflammatory drug, with that of phenylbutazone. Patients received 800 mg of either drug daily for 2 days and then 600 mg daily for up to 8 days. The results of patient assessment showed there was no significant difference between the two groups in time taken either to significant improvement or to final resolution of the gout attack. No side-effects were reported with either drug.


Assuntos
Feprazona/uso terapêutico , Gota/tratamento farmacológico , Fenilbutazona/análogos & derivados , Fenilbutazona/uso terapêutico , Doença Aguda , Adulto , Idoso , Ensaios Clínicos como Assunto , Método Duplo-Cego , Feminino , Humanos , Masculino , Pessoa de Meia-Idade
12.
Vision Res ; 40(13): 1711-37, 2000.
Artigo em Inglês | MEDLINE | ID: mdl-10814758

RESUMO

The spectral sensitivities of middle- (M-) and long- (L-) wavelength-sensitive cones have been measured in dichromats of known genotype: M-cone sensitivities in nine protanopes, and L-cone sensitivities in 20 deuteranopes. We have used these dichromat cone spectral sensitivities, along with new luminous efficiency determinations, and existing spectral sensitivity and color matching data from normal trichromats, to derive estimates of the human M- and L-cone spectral sensitivities for 2 and 10 degrees dia. central targets, and an estimate of the photopic luminosity function [V(lambda)] for 2 degrees dia. targets, which we refer to as V(2)*(lambda). These new estimates are consistent with dichromatic and trichromatic spectral sensitivities and color matches.


Assuntos
Percepção de Cores/genética , Defeitos da Visão Cromática/genética , Células Fotorreceptoras Retinianas Cones/fisiopatologia , Adulto , Algoritmos , Estudos de Casos e Controles , Defeitos da Visão Cromática/fisiopatologia , Genótipo , Humanos , Fotometria , Pigmentos da Retina/genética , Pigmentos da Retina/fisiologia , Cromossomo X/genética
13.
Vision Res ; 40(13): 1739-50, 2000.
Artigo em Inglês | MEDLINE | ID: mdl-10814759

RESUMO

Tritanopic color matches (i.e. matches that depend on the middle- (M) and long- (L), but not short- (S) wavelength-sensitive cones) were made between two half-fields: one illuminated by either a 405 or a 436 nm Hg spectral line; the other by a light of variable wavelength and radiance. Our purpose was to test between rival M- and L-cone spectral sensitivities, which should predict the tritanopic matches. The observers were tritanopes, in whom functioning S-cones are lacking, or normal trichromats, in whom artificial tritanopia was induced by a strong, violet adapting field. The wavelengths found to match the 405 and 436 nm lights agreed poorly with those predicted by the cone spectral sensitivities of Smith and Pokorny (1975) [Vision Research, 15, 161], while the 405 nm matching wavelength agreed poorly with that predicted by Stockman, MacLeod and Johnson (1993) [Journal of the Optical Society of America, A10, 2491]. Both matching wavelengths agreed well, however, with the predictions of the Stockman and Sharpe (2000) [Vision Research] M- and L-cone spectral sensitivities, which lie within the range of measured matches.


Assuntos
Percepção de Cores/fisiologia , Defeitos da Visão Cromática/fisiopatologia , Células Fotorreceptoras Retinianas Cones/fisiologia , Defeitos da Visão Cromática/genética , Feminino , Genótipo , Humanos , Masculino , Pigmentos da Retina/fisiologia
14.
Vision Res ; 38(23): 3703-28, 1998 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-9893801

RESUMO

The Talbot-Plateau law fails for flicker detected by the short-wavelength-sensitive (S) cones: a 30-40 Hz target, flickering too fast for the flicker to be resolved, looks more yellow than a steady target of the same average intensity. The color change, which is produced by distortion at an early compressive nonlinearity, was used to reveal a slightly bandpass S-cone temporal response before the distortion site and a lowpass response after it. The nonlinearity is probably a 'hard' nonlinearity that arises because the S-cone signal is limited by a response ceiling, which the mean signal level approaches and exceeds as the S-cone adaptation level increases. The nonlinearity precedes the combination of flicker signals from all three cone types.


Assuntos
Percepção de Cores/fisiologia , Fusão Flicker/fisiologia , Adaptação Ocular , Feminino , Humanos , Masculino , Células Fotorreceptoras Retinianas Cones/fisiologia , Limiar Sensorial/fisiologia , Fatores de Tempo
15.
Vision Res ; 38(21): 3193-206, 1998 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-9893826

RESUMO

The spectral sensitivities of the short (S-), middle (M-) and long (L-) wave-sensitive cones have been measured in normal trichromats and in dichromats and monochromats of known genotype. For the S-cone sensitivities, three blue-cone monochromats and five normals were used; for the M-cone sensitivities, nine protanopes (three with a single L1M2 gene, three with a single L2M3 gene, one with both an L1M2 and an M gene, and two with both an L2M3 and an M gene); and for the L-cone sensitivities, 22 deuteranopes (five with a single L(ala180) gene and 17 with a single L(ser180) gene). We compare existing cone spectral sensitivity estimates with these results and with tritanopic color matches. The new findings are more consistent with the cone fundamentals of Stockman et al. (JOSA 1993(A10), 2491) than with those of Smith and Pokorny (Vision Research 1975(15), 161). The discrepancies that we find, however, are sufficient to warrant the replacement of both sets.


Assuntos
Percepção de Cores/fisiologia , Células Fotorreceptoras Retinianas Cones/fisiologia , Testes de Percepção de Cores , Defeitos da Visão Cromática/fisiopatologia , Humanos , Matemática , Pigmentos da Retina/genética , Espectrofotometria
16.
Vision Res ; 31(2): 189-208, 1991.
Artigo em Inglês | MEDLINE | ID: mdl-2017881

RESUMO

Flicker modulation sensitivity measurements made on high intensity orange steady backgrounds indicate that signals from short-wavelength sensitive cones (S-cones) have access to two pathways. At low S-cone adaptation levels the frequency response falls quickly with increasing frequency, but at higher adaptation levels it extends to much higher frequencies. At these higher S-cone adaptation levels, the following procedures can selectively expose either a process sensitive to low frequencies or one more sensitive to higher frequencies: (1) at high flicker frequencies, the S-cone signal can be nulled by a long-wavelength sensitive cone (L-cone) signal of suitable amplitude and phase, but at low frequencies a residual flicker persists; the modulation sensitivity for the residual flicker is lowpass in shape with a rapid decline in sensitivity with increasing flicker frequency; (2) sensitivity to flicker in the presence of a 17 Hz S- or L-cone mask is also lowpass with a similarly steep loss of high frequency sensitivity; yet (3) sensitivity to flicker during transient stimulation of the S-cones at 0.5 Hz is comparatively wideband (and slightly bandpass) in shape. The S-cone signal produced by the high frequency process is almost as well-maintained towards high frequencies as M- and L-cone signals. Furthermore, it is capable of participating in flicker photometric nulls with M- and L-cone signals. At low frequencies, however, when the low frequency S-cone signal is also present, satisfactory nulls can not be found. From these and phenomenological considerations, we identify the low and high frequency S-cone processes as S-cone inputs to the chromatic and luminance pathways, respectively. The phase adjustments needed to optimize flicker photometric nulls reveal that the S-cone input to the luminance pathway is actually inverted, but this is demonstrable only at relatively low frequencies: at medium or high frequencies the S-cone influence can be synergistic with that of the other cone types because of a delay in the transmission of S-cone signals.


Assuntos
Fusão Flicker/fisiologia , Células Fotorreceptoras/fisiopatologia , Adaptação Ocular/fisiologia , Humanos , Masculino , Vias Neurais/fisiologia , Mascaramento Perceptivo/fisiologia , Limiar Sensorial/fisiologia , Espectrofotometria , Fatores de Tempo
17.
Vision Res ; 27(4): 637-50, 1987.
Artigo em Inglês | MEDLINE | ID: mdl-3660624

RESUMO

Using a psychophysical method that allows the tracking of very rapid changes in sensitivity, we demonstrate an anomaly in the time-course of light adaptation for the short-wave mechanism: after the onset of a yellow (581 nm) field of approximately 10(5.3) td the threshold for short-wave targets does not recover monotonically but continues to rise for several seconds before falling to its equilibrium value. The phenomenon is absent when the adapting field has a wavelength of 511 nm and has been adjusted to give a similar equilibrium value for the short-wave threshold.


Assuntos
Adaptação Ocular , Percepção de Cores/fisiologia , Humanos , Masculino , Limiar Sensorial/fisiologia , Espectrofotometria , Fatores de Tempo
18.
Vision Res ; 33(18): 2705-20, 1993 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-8296467

RESUMO

Psychophysical and electroretinographic observations in normal and achromat observers suggest that rod flicker signals have access to at least two retinal pathways: one (pi 0), slow and sensitive, predominating at scotopic luminance levels; the other (pi'0), fast and insensitive, predominating at mesopic ones. We have measured steady-state flicker detection sensitivities on background fields ranging from 430 to 640 nm in normal observers. Our results suggest that cone signals can reduce the sensitivity of pi'0, but have comparatively little effect on pi 0. The pi'0 field sensitivities derived from these measurements have been fitted with linear combinations of the scotopic luminosity function, V' lambda, the M-cone spectral sensitivity function, M lambda, and the L-cone function, L lambda. These fits demonstrate a clear cone influence on pi'0, but they cannot tell us unequivocally whether the influence is from the M-cones, from the L-cones or from both. Accordingly, we made similar measurements in dichromats, who lack one of the two longer wavelength cone types. These measurements revealed an L-cone influence on pi'0 in the deuteranope and an M-cone influence in the protanope. This suggests that both cone types can affect the sensitivity of pi'0. The finding that the steady-state cone signals reduce the sensitivity of pi'0 but have little effect on pi 0 could suggest that pi'0 signals travel through a faster cone pathway (with its own gain control at which both rod and cone signals can reduce rod threshold), while pi 0 signals travel through a separate rod pathway. However, it could simply reflect the fact that pi'0 predominates at higher luminances than pi 0 where the cone excitation level is inevitably greater. To examine the influence of the cones on pi 0 more closely, we: (i) produced transient cone excitation by alternating rod-equated 480 and 679 nm fields; and (ii) extended our steady-state measurements to include deep-red backgrounds of 650 and 680 nm. Both experiments revealed a small, but measurable influence of the cones on pi 0.


Assuntos
Células Fotorreceptoras Retinianas Bastonetes/fisiologia , Vias Visuais/fisiologia , Defeitos da Visão Cromática/fisiopatologia , Fusão Flicker/fisiologia , Humanos , Limiar Sensorial/fisiologia , Campos Visuais/fisiologia
19.
Vision Res ; 29(11): 1539-59, 1989.
Artigo em Inglês | MEDLINE | ID: mdl-2635479

RESUMO

Rod vision has a duality of organization: at mesopic luminances rod signals have access to a slow, sensitive pathway (which we refer to, following Stiles, as pi 0) and a fast, insensitive pathway (pi' 0). The phase lag between the two rod signals increases with frequency until at 15-Hz the rod signals transmitted through the two pathways emerge out-of-phase, so that destructive interference produces a nulling of the apparent flicker. Relative to the cones, the phase lag of pi' 0 is roughly half that of pi 0. Thus at 15-Hz pi' 0 signals can be out-of-phase with cone signals, so that the signals from the slower pathway, pi 0, are actually in phase with cone signals. We have investigated the frequency response, adaptation behavior and phase characteristics of the two rod processes. The slower process, pi 0 is more sensitive than pi' 0, and dominates from absolute threshold up to low mesopic levels. The adaptation of pi 0 seems not to be associated with a change in time constant, but rather with simple response compression or sensitivity scaling. The time constant of pi' 0, however, does change with adaptation. There are large differences in the way that light adaptation changes the sensitivity of the two processes: signals from pi'0 may evade part of the postreceptoral sensitivity regulating mechanism normally associated with rod vision. The ability of signals from pi 0 and pi' 0 to reinforce or cancel each other, however, suggests that they are later reunited in a common pathway.


Assuntos
Adaptação à Escuridão/fisiologia , Fusão Flicker/fisiologia , Células Fotorreceptoras/fisiologia , Humanos , Masculino , Estimulação Luminosa/instrumentação , Psicofísica , Testes Visuais , Vias Visuais/fisiologia
20.
Vision Res ; 39(17): 2901-27, 1999 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-10492818

RESUMO

We used two methods to estimate short-wave (S) cone spectral sensitivity. Firstly, we measured S-cone thresholds centrally and peripherally in five trichromats, and in three blue-cone monochromats, who lack functioning middle-wave (M) and long-wave (L) cones. Secondly, we analyzed standard color-matching data. Both methods yielded equivalent results, on the basis of which we propose new S-cone spectral sensitivity functions. At short and middle-wavelengths, our measurements are consistent with the color matching data of Stiles and Burch (1955, Optica Acta, 2, 168-181; 1959, Optica Acta, 6, 1-26), and other psychophysically measured functions, such as pi 3 (Stiles, 1953, Coloquio sobre problemas opticos de la vision, 1, 65-103). At longer wavelengths, S-cone sensitivity has previously been over-estimated.


Assuntos
Percepção de Cores/fisiologia , Células Fotorreceptoras Retinianas Cones/fisiologia , Humanos , Macula Lutea , Masculino , Psicofísica , Pigmentos da Retina/análise , Limiar Sensorial/fisiologia , Espectrofotometria
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