Chromatic sensitivity of ganglion cells in the peripheral primate retina

Visual abilities change over the visual field. For example, our ability to detect movement is better in peripheral vision than in foveal vision, but colour discrimination is markedly worse. The deterioration of colour vision has been attributed to reduced colour specificity in cells of the midget, parvocellular (PC) visual pathway in the peripheral retina. We have measured the colour specificity (red-green chromatic modulation sensitivity) of PC cells at eccentricities between 20 and 50 degrees in the macaque retina. Here we show that most peripheral PC cells have red-green modulation sensitivity close to that of foveal PC cells. This result is incompatible with the view that PC pathway cells in peripheral retina make indiscriminate connections ('random wiring') with retinal circuits devoted to different spectral types of cone photoreceptors. We show that selective cone connections can be maintained by dendritic field anisotropy, consistent with the morphology of PC cell dendritic fields in peripheral retina. Our results also imply that postretinal mechanisms contribute to the psychophysically demonstrated deterioration of colour discrimination in the peripheral visual field.     

Melanopsin-expressing ganglion cells in primate retina signal colour and irradiance and project to the LGN

Human vision starts with the activation of rod photoreceptors in dim light and short (S)-, medium (M)-, and long (L)- wavelength-sensitive cone photoreceptors in daylight. Recently a parallel, non-rod, non-cone photoreceptive pathway, arising from a population of retinal ganglion cells, was discovered in nocturnal rodents. These ganglion cells express the putative photopigment melanopsin and by signalling gross changes in light intensity serve the subconscious, 'non-image-forming' functions of circadian photoentrainment and pupil constriction. Here we show an anatomically distinct population of 'giant', melanopsin-expressing ganglion cells in the primate retina that, in addition to being intrinsically photosensitive, are strongly activated by rods and cones, and display a rare, S-Off, (L + M)-On type of colour-opponent receptive field. The intrinsic, rod and (L + M) cone-derived light responses combine in these giant cells to signal irradiance over the full dynamic range of human vision. In accordance with cone-based colour opponency, the giant cells project to the lateral geniculate nucleus, the thalamic relay to primary visual cortex. Thus, in the diurnal trichromatic primate, 'non-image-forming' and conventional 'image-forming' retinal pathways are merged, and the melanopsin-based signal might contribute to conscious visual perception.     

Generation of cat retinal ganglion cells in relation to central pathways

The ganglion cells of the cat retina form classes distinguishable in terms of perikaryal size, dendritic morphology and functional properties. Further, the axons differ in their diameters, patterns of chiasmatic crossing and in their central connections. Here we define, by 3H-thymidine autoradiography, the order of production of cells of each class and relate the order of the 'birthdates' to the known axonal pathways. The ganglion cell classes are produced in broad waves, which overlap as cells are produced first for central then for peripheral retina. Medium-sized cells are produced before the largest cells, and small ganglion cells are produced throughout the period of cell generation. This sequence of cell production relates to the orderly arrangement of axons in the optic tract, and can also be related to the rules of chiasmatic crossing observed for each ganglion cell class.     

Identification of a distinct synaptic glutamate receptor on horizontal cells in mudpuppy retina

The separation of ON and OFF channels and the development of an antagonistic surround occur at the first synapse in the vertebrate retina. This functional differentiation is mediated by the action of the photoreceptor neurotransmitter on the ON bipolar, OFF bipolar and horizontal cells, respectively. Glutamate mimics the action of the photoreceptor transmitter on all second-order neurones in fish, amphibian and mammalian retinas. The diversity of cellular responses produced by one neurotransmitter raises the possibility of multiple postsynaptic receptor-ionophore complexes. We reported previously that one glutamate analogue, 2-amino-4-phosphonobutyrate, reveals that the ON bipolar synaptic receptor is pharmacologically different from those of other second-order neurones. The results presented here demonstrate that another glutamate analogue, D-O-phosphoserine, selectively antagonizes the synaptic responses of horizontal cells. Taken together, these findings indicate that there are three glutamate-like receptor subtypes in the outer retina and suggest a correlation between receptor subtype and the physiological properties of second-order neurones.     

Multiple classes of glutamate receptor on depolarizing bipolar cells in retina

Multiple subtypes of excitatory amino acid receptor have been found on individual dissociated neurones. These findings were obtained from cells without intact synaptic connections, so the functional roles for such receptor subtypes are unknown. We have recorded intracellular responses from depolarizing bipolar cells (DBC) that receive direct synaptic input from two distinct populations of neurones: rods and cones. We report here that 2-amino-4-phosphonobutyrate (APB), a glutamate analogue, reveals two subtypes of glutamate receptors on DBCs. APB acts on the same receptor that mediates synaptic transmission from rods but has no action on the second subtype of glutamate receptor. These results show that the rod and cone inputs to DBCs are mediated by pharmacologically distinct receptors and that subtypes of glutamate receptor existing on single neurones can subserve separate, functionally defined synaptic inputs.     

应用SNaPshot技术对桉树SNP的检测

【目的】SNaPshot是一种单核苷酸多态性(SNP)检测的多重分析技术,具有检测速度快、准确性高、成本低廉等特点。利用多重PCR技术,结合SNaPshot分型方法,在桉树中构建SNP复合分型检测体系,促进SNP技术在桉树遗传图谱构建和无性系鉴定的应用。【方法】利用桉树已有的EST序列设计引物,通过PCR产物直接测序进行SNP标记位点的开发,利用多重PCR技术和SNaPshot分型方法建立SNP复合分型检测体系,并在尾叶桉和细叶桉作图群体的两亲本和6个F₁子代,以及16个国内常用的桉树无性系中进行分型检测。【结果】共设计合成12对SNP引物,分为3组(Ⅰ、Ⅱ、Ⅲ)建立了SNP复合分型检测体系,SNP分型情况与测序结果一致。对桉树作图群体的两个亲本和6个F₁子代的分型结果进行统计,发现12个SNP标记在6个子代中均发生了分离; 对桉树无性系进行多态性的分析,期望杂合度(H_e)为0.11～0.51、观测杂合度(H_o)为0.11～0.56,多态性信息含量(PIC)为0.10～0.37,表现为中度或低度多态性。【结论】利用多重PCR和SNaPshot技术可以快速地对桉树进行基因分型,其结果准确可靠,可以用于桉树遗传图谱的构建以及桉树无性系的鉴定等方面研究。     

血清抗Sm抗体ELISA检测方法的建立

目的：建立血清抗Sm抗体的ELISA检测方法。方法：应用纯化的Sm抗原,采用棋盘滴定等方法确立ELISA方法检测血清抗Sm抗体的最适实验条件。结果：建立了血清抗Sm抗体的ELISA检测方法。SLE患者血清抗Sm抗体的阳性率为29．2％,正常人和其它自身免疫病患者未查到此抗体。结论：本文建立的血清抗Sm抗体检测方法敏感性达到国外进口试剂盒的水平,且操作简便,重复性好,因此临床很有实用价值。