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Biomedical subjects

Darren Behn

Publications and source records attributed to Darren Behn.

4 recordsLinked to original sources
PubMed2003

Dark adaptation is faster in pigmented than albino rats.

PURPOSE: Previous reports have raised the possibility that, compared to pigmented rats, albino rats might be night blind. The purpose of this study was to reinvestigate this issue by comparing the dark-adaptation process of the pigmented Long-Evans (LE) and albino Sprague Dawley (SD) rats. METHODS: Scotopic ERGs obtained from LE and SD rats were recorded following periods of dark adaptation 0.5, 3 and 12 h. Intensity response functions were generated with flashes of white light spanning over a 7 log-unit range with a maximal intensity of 8 cd x s x m(-2) in energy. RESULTS: SD rats showed a gradual increase in the amplitude of the scotopic b-wave Vmax (maximal 'saturated' rod b-wave amplitude) and retinal sensitivity (k) as the duration of the dark-adaptation period increased. In contrast, LE rats did not demonstrate any further significant gain in retinal function (Vmax or k) beyond 30 min of dark-adaptation. Thus for periods of dark-adaptation of 30 min or less, the rod function of the LE rats is superior to that of the SD rats while both strains have comparable retinal functions following 3 h or more of dark-adaptation. CONCLUSIONS: Our results indicate that LE and SD rats differ in their rapidity to dark-adapt, a finding that could explain the previous claim that SD rats were night blind. The reduced bio-availability of calcium ions in eyes lacking melanin could explain this difference. Calcium was previously shown to play a key role in retinal adaptation processes.

Albinism, Oculocutaneous↗
PubMed2003

Spontaneous occurrence of a potentially night blinding disorder in guinea pigs.

Several hereditary retinal disorders such as retinitis pigmentosa and congenital stationary night blindness compromise, sometimes exclusively, the activity of the rod pathway. Unfortunately, there are few animal models of these disorders that could help us better understand the pathophysiological processes involved. The purpose of this report is to present a pedigree of guinea pigs where, as a result of a consanguineous mating and subsequent selective breeding, we developed a new and naturally occurring animal model of a rod disorder. Analysis of the retinal function with the electroretinogram reveals that the threshold for rod-mediated electroretinograms (ERGs) is significantly increased by more than 2 log-units compared to that of normal guinea pigs. Furthermore, in response to a suprathreshold stimulus, also delivered under scotopic condition, which yield a mixed cone-rod response in normal guinea pigs, the ERG waveform in our mutant guinea pigs is almost identical (amplitude and timing of a- and b-waves) to that evoked in photopic condition. The above would thus suggest either a structural (abnormal development or absence) or a functional deficiency of the rod photoreceptors. We believe that our pedigree possibly represents a new animal model of a night blinding disorder, and that this condition is inherited as anautosomal recessive trait in the guinea pig population.

Animals↗
PubMed2002

Autoantibodies to transducin in a patient with melanoma-associated retinopathy.

PURPOSE: To report novel immunoreactivity in a patient with melanoma-associated retinopathy. DESIGN: Retrospective case report and experimental study. METHODS: A 32-year-old woman with a history of metastatic melanoma presented with bilateral decreased visual acuity. Electroretinography, Goldmann perimetry, immunohistochemistry, and Western blotting of her serum were performed. RESULTS: Electroretinography showed a "negative" B-wave. Paracentral and central scotomas were observed on Goldmann perimetry. Antibodies to a retinal transducin were demonstrated by Western blotting. No immunoreactivity to retinal bipolar cells was detected by immunohistochemistry. CONCLUSION: Melanoma-associated retinopathy can be related to a variety of antiretinal antibodies. Recognition of transducin, a novel melanoma-associated retinopathy antigen, may be important for identifying and treating patients with night blindness and melanoma.

Adult↗