Rayleigh matches in carriers of inherited color vision defects: The contribution from the third L/M photopigment

The mother or daughter of a male with an X-chromosome-linked red/green color defect is an obligate carrier of the color deficient gene array. According to the Lyonization hypothesis, a female carrier's defective gene is expressed and thus carriers may have more than two types of pigments in the L/M photopigment range. An open question is how a carrier's third cone pigment in the L/M range affects the postreceptoral neural signals encoding color. Here, a model considered how the signal from the third pigment pools with signals from the normal's two pigments in the L/M range. Three alternative assumptions were considered for the signal from the third cone pigment: it pools with the signal from (1) L cones, (2) M cones, or (3) both types of cones. Spectral-sensitivity peak, optical density, and the relative number of each cone type were factors in the model. The model showed that differences in Rayleigh matches among carriers can be due to individual differences in the number of the third type of L/M cone, and the spectral sensitivity peak and optical density of the third L/M pigment; surprisingly, however, individual differences in the cone ratio of the other two cone types (one L and the other M) did not affect the match. The predicted matches were compared to Schmidt's (1934/1955) report of carriers' Rayleigh matches. For carriers of either protanomaly or deuteranomaly, these matches were not consistent with the signal from the third L/M pigment combining with only the signal from M cones. The matches could be accounted for by pooling the third-pigment's response with L-cone signals, either exclusively or randomly with M-cone responses as well.

Background and First Results from the New AAO/UKST Hα Survey

The UK Schmidt Telescope (UKST) of the Anglo-Australian Observatory (AAO) has just embarked on a new Hα survey of the Southern Galactic Plane, Magellanic Clouds and selected regions using a specially designed, high-specification, monolithic, interference filter. It is probably the largest of its kind for astronomy. It is being used in combination with Kodak Tech Pan film-based emulsion. This emulsion not only has a useful sensitivity peak at Hα but also possesses extremely fine grain and an exceptionally high DQE for the hypersensitised product (∼10%). This leads to excellent imaging, sensitivity and low noise. It is clear that CCDs cannot yet match the wide-area coverage, uniformity and resolution of the UKST/Tech Pan combination for undertaking such a survey. The survey will initially include about 233 Galactic Plane and 40 Magellanic Cloud fields on 4-degree centres and will take about 3 years to complete. Some preliminary images from the new survey are presented and compared with the best previously available from the UKST. Examples of the first survey discoveries, new resolved Galactic planetary nebulae, are also given. This survey will have an unprecedented combination of area coverage, depth and resolution, superior to those of any previous optical survey of ionised gas in the Galaxy. Many new discoveries and research avenues are expected.

The polyomavirus enhancer activates chromatin accessibility on integration into the HPRT gene

Recent studies suggest that enhancers may increase the accessibility of chromatin to transcription factors. To test the effects of a viral enhancer on chromatin accessibility, we have inserted minigenes with or without the polyomavirus enhancer into the third exon of the hypoxanthine phosphoribosyltransferase (HPRT) gene by homologous recombination and have prepared high-resolution maps of gene accessibility by using a novel polymerase chain reaction assay for DNase I sensitivity. In its native state, we find that the HPRT gene has low sensitivity to DNase I in fibrosarcoma cells. Insertion of the polyomavirus enhancer and neo reporter gene into exon 3 confers altered HPRT DNase I sensitivity for several kilobases on either side of the enhancer. The changes in DNase I sensitivity peak near the enhancer and decline with distance from the enhancer. The increase in HPRT DNase I sensitivity persisted when the tk promoter was deleted from the inserted construct but disappeared when the enhancer was deleted. These experiments identify the polyomavirus enhancer as a cis-acting initiator of chromatin accessibility.

The polyomavirus enhancer activates chromatin accessibility on integration into the HPRT gene.

Recent studies suggest that enhancers may increase the accessibility of chromatin to transcription factors. To test the effects of a viral enhancer on chromatin accessibility, we have inserted minigenes with or without the polyomavirus enhancer into the third exon of the hypoxanthine phosphoribosyltransferase (HPRT) gene by homologous recombination and have prepared high-resolution maps of gene accessibility by using a novel polymerase chain reaction assay for DNase I sensitivity. In its native state, we find that the HPRT gene has low sensitivity to DNase I in fibrosarcoma cells. Insertion of the polyomavirus enhancer and neo reporter gene into exon 3 confers altered HPRT DNase I sensitivity for several kilobases on either side of the enhancer. The changes in DNase I sensitivity peak near the enhancer and decline with distance from the enhancer. The increase in HPRT DNase I sensitivity persisted when the tk promoter was deleted from the inserted construct but disappeared when the enhancer was deleted. These experiments identify the polyomavirus enhancer as a cis-acting initiator of chromatin accessibility.

The ontogeny of ultraviolet photosensitivity in rainbow trout (Salmo gairdneri)

The present study examines the changes in ultraviolet (UV) photosensitivity that occur during the growth of rainbow trout (Salmo gairdneri). A comparison of the ocular media transmission of small (n = 3) and large (n = 3) trout eyes did not reveal large changes in the transmission of UV radiation through the eye. We used the heart-rate conditioning technique to measure spectral sensitivity in immobilized trout. Four trout, each weighing less than 30 g, exhibited a UV-sensitivity peak at 360 nm while four additional trout weighing more than 60 g each exhibited no evidence of UV sensitivity. Spectral-sensitivity measurements of two trout weighing 44 g and 60 g revealed UV sensitivity, but when measured one month later (after a 25% increase in body weight) both fish exhibited no UV-sensitivity peak. At this time their sensitivity appeared to conform to the known blue-sensitive cone mechanism.

Comparative aspects of auditory function in Australian anurans

The auditory sensitivity of 17 species of Australian anurans was measured by recording responses of groups of midbrain auditory neurones to sound stimuli of different frequencies. In 14 species there are two peaks of maximal auditory sensitivity and in three species there are three peaks. In all species the sensitivity peak which occurred at the higher frequency corresponded to the frequency of the mating call. There is a significant correlation between the auditory threshold at this higher sensitivity peak and both head width and tympanum width.