Fucosylated protein of retinal cone photoreceptor outer segments: morphological and biochemical analyses

Cone outer segments (OS) of the goldfish retina are diffusely labeled after intravitreal injection of [(3)H]fucose while rod OS remain unlabeled. By electron microscopic radioautography, the OS of red- and blue-sensitive cones are heavily labeled while green- sensitive cone OS are lightly labeled. The time-course and pattern of OS labeling in all cone types from 30 min to 24 h resemble that of incorporation of other sugars into rhodopsin in rod OS. The nature of the cone OS-specific fucosylated component(s) was examined using biochemical techniques. Cone OS were prelabeled by intravitreal injection of [(3)H]fucose 24 h before sacrifice. Photoreceptor OS were isolated using a discontinuous sucrose density gradient and it was verified by electron microscopic radioautography that the only source of radioactivity in the preparations was cone OS. The different cone types could be recognized by the heaviness of labeling, characteristic membrane spacing, and 'staining' of green cone OS in vitro with horseradish peroxidase. After acid hydrolysis of prelabeled photoreceptor membranes, 90 percent of the counts were in the neutral sugar fraction which was analyzed by thin-layer chromatography. Approximately 70 percent of the radioactivity co-chromatographed with authentic fucose. SDS-PAGE/fluorography of prelabeled photoreceptor membranes revealed a single radioactive component that was lightly stained with coomassie blue and showed an apparent molecular weight of 33,000. This cone-derived band was separated from unlabeled rod opsin which was well stained and showed an apparent mol wt of 38,000. Isoelectric focusing under denaturing conditions produced two major and one minor band of radioactivity with isoelectric points of 8.2, 8.6, and 8.8 respectively. No radioactivity was found in association with a stained band corresponding in isoelectric point to that of bovine opsin (pl, 6.2). The fucosylated component was readily digested by pronase, indicating its protein nature. Washing of the isolated OS with isotonic and hypotonic buffers failed to extract major amounts of the radioactivity, suggesting that the fucosylated component is an integral membrane protein. The presence of a fucosylated protein thus represents a major difference between cone and rod OS in the goldfish and has enabled us to identify cone OS in preparations of isolated photoreceptor membranes and to demonstrate the separation of a cone-derived glycoprotein from rod opsin.     

Structure and organization of the bovine beta-globin genes

Genomic clones spanning the entire cow beta-globin gene locus have been isolated and characterized. These clones demonstrate that the linkage of embryonic-like (epsilon) genes and pseudogenes (psi) to the previously described fetal (gamma) and adult (beta) genes is as follows: 5'-epsilon 3-epsilon 4-psi 3-beta-epsilon 1-epsilon 2-psi 1- psi 2-gamma-3'. Present data indicate that, like that of the goat, the fetal and adult genes arose via block duplication of an ancestral four- gene set: epsilon-epsilon-psi-beta. This duplication event preceded the divergence of cows and goats, which occurred greater than or equal to 18-20 Myr ago. However, cows do not have the additional four-gene block containing a preadult/stress globin gene (beta C). Furthermore, the cow fetal cluster contains an extra beta-like pseudogene, which apparently arose by a small-scale duplication. The fixation of this duplication may indicate a possible evolutionary role for pseudogenes.      

New Data on the Taxonomy of the Weevil Subgenus <Emphasis Type="Italic">Caucasoplinthus</Emphasis>, Genus <Emphasis Type="Italic">Plinthus</Emphasis> (Coleoptera,Curculionidae)

The taxonomic composition of the subgenus Caucasoplinthus Davidian, 1995 is revised. The immunis and granulosus groups are downgraded to subgroups of the silphoides and fallax groups, respectively; the voriseki subgroup is transferred from the fallax to the fausti group. Plinthus attilai Davidian et Savitsky, sp. n. and P. ljudae Davidian et Savitsky, sp. n. are described from Turkey and Abkhazia, respectively. New data on the taxonomy, distribution, and ecology of some little-known species are presented. The following new synonymy is established: Molytes vittatus Motschulsky, 1839 (= Meleus irroratus Reitter, 1884, syn. n., = Meleus faldermanni Faust, 1884, syn. n., = Meleus difficilis Faust, 1884, syn. n.).     

A new species of the weevil genus <Emphasis Type="Italic">Otiorhynchus</Emphasis> germ., subgenus <Emphasis Type="Italic">Dibredus</Emphasis> Rtt. (Coleoptera,Curculionidae: Entiminae), from Southeastern Turkey

Otiorhynchus schuberti sp. n. (subgenus Dibredus Reitter, 1912) is described from Kahramanmara? Province in Southeastern Turkey. It is closely related to O. nudiformis Reitter, 1914 and, less closely, to O. rufimanus Hochhuth, 1847, but differs from both in a small bidentate tooth on the fore femur.