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Y Toh

Publications and source records attributed to Y Toh.

At least 91 records · Page 5Linked to original sources
PubMed1991

Glycoprotein C of herpes simplex virus type 1 is essential for the virus to evade antibody-independent complement-mediated virus inactivation and lysis of virus-infected cells.

Glycoprotein C (gC) of herpes simplex virus type 1 (HSV-1) is a receptor for the complement component C3b. We have previously isolated HSV-1 gC- strains (TN1, TN2 and TN3) from a patient with recurrent keratitis at three different times. These are very rare isolates because gC was thought to be essential for the virus in vivo. To determine whether gC modifies the interaction of complement with cell-free virus or virus-infected cells, we constructed gC+ recombinant viruses in which the intact gC gene of strain KOS was inserted into the TN1 virus genome. TN1 virus was inactivated by complement and TN1 virus-infected cells were lysed by complement; however, gC+ recombinant viruses became resistant to these effects of complement. These results suggest a role for gC in protection of both the virion envelope and the infected cell surface against damage by complement. TN1 virus was inactivated by complement from rats (Wistar, WKA, F344 and SD), guinea-pigs (Hartley) and humans, but not by complement from mice (C3H, DDD and BALB/c), which indicates that mice seem to be inappropriate as an experimental model for the study of HSV infection in which complement factors need to be considered.

Animals↗
PubMed1990

Proclotting enzyme from horseshoe crab hemocytes. cDNA cloning, disulfide locations, and subcellular localization.

Proclotting enzyme is an intracellular serine protease zymogen closely associated with an endotoxin-sensitive hemolymph coagulation system in limulus. Its active form, clotting enzyme, catalyzes conversion of coagulogen to insoluble coagulin gel. We present here the cDNA and amino acid sequences, disulfide locations, and subcellular localization of proclotting enzyme. The isolated cDNA for proclotting enzyme consists of 1,501 base pairs. The open reading frame of 1,125 base pairs encodes a sequence comprising 29 amino acid residues of prepro-sequence and 346 residues of the mature protein with a molecular mass of 38,194 Da. Three potential glycosylation sites for N-linked carbohydrate chains were confirmed to be glycosylated. Moreover, the zymogen contains six O-linked carbohydrate chains in the amino-terminal light chain generated after activation. The cleavage site that accompanies activation catalyzed by trypsin-like active factor B, proved to be an Arg-Ile bond. The resulting carboxyl-terminal heavy chain is composed of a typical serine protease domain, with a sequence similar to that of human coagulation factor XIa (34.5%) or factor Xa (34.1%). The light chain has a unique disulfide-knotted domain which shows no significant homology with any other known proteins. Thus, this proclotting enzyme has a mammalian serine protease domain and a structural domain not heretofore identified in coagulation and complement factors. Immunohistochemical studies showed that the proclotting enzyme is localized in large granules of hemocytes.

Amino Acid Sequence↗
PubMed1990

Antimicrobial tachyplesin peptide precursor. cDNA cloning and cellular localization in the horseshoe crab (Tachypleus tridentatus).

The hemocytes of the horseshoe crab have been found to contain a new family of Arthropodous antibiotics, termed the "tachyplesin family." These peptides are composed of 17-18 amino acid residues with a carboxyl-terminal arginine alpha-amide. We report here the entire cDNA sequence coding for the tachyplesin precursors and their distribution in various tissues of the horseshoe crab. Sequence analysis of the cloned cDNAs revealed that the tachyplesin precursors consist of 77 amino acids with 23 residues in a presegment, and that there are two types of mRNAs corresponding to the isopeptides tachyplesins I and II. Both precursors contain a putative signal peptide, a processing peptide sequence and a carboxyl-terminal amidation signal "Gly-Lys-Arg" connected to the mature tachyplesin peptide. Moreover, an unusual acidic amino acid cluster, Asp-Glu-Asp-Glu-Asp-Asp-Asp-Glu-Glu-COOH, is present in the carboxyl-terminal portions of both precursors. These results suggest that the two types of tachyplesin precursors are first synthesized as preproproteins and are then incorporated into the intracellular organelle, accompanied by various processing events. Northern blot analysis on a total RNA from various tissues of the horseshoe crab revealed that the tachyplesin precursors are expressed mainly in hemocytes and cardiac and brain tissues. Tachyplesin was immunohistochemically localized in the smaller dense granules rather than the typical large granules present in abundance in the hemocytes.

Amino Acid Sequence↗
PubMed1990

Morphological and physiological characterization of small multimodal ocellar interneurons in the American cockroach.

The morphology and physiology of small multimodal ocellar interneurons (SM-neurons) have been examined in the cockroach Periplaneta americana. The SM-neuron is monopolar with its cell body in the tritocerebrum near the esophagus. Its axon ascends to the protocerebrum and extends into the ocellar neuropil through the ocellar tract and the ocellar nerve. The axon sends a long collateral process towards the optic tract. The SM-neuron responded with spike discharges to various sensory stimuli. The collateral and many side branches along the axon in the deutocerebrum appear to be input regions from those sensory afferents. Cercal stimulation triggered most effectively a train of spikes in the SM-neuron: some of seven giant axons in the ventral nerve cord were involved in this pathway. Cercal stimulation also evoked depolarization in the large second order ocellar neurons (L-neurons). A possible neural connection between SM-neurons and L-neurons was examined pharmacologically. Interaction of ocellar illumination and cercal stimulation in the L-neuron was also examined. These data are discussed in relation to the ocellar function of cockroaches and in comparison with data obtained in other insects.

Animals↗
PubMed1990

Morphological and physiological characterization of descending ocellar interneurons in the American cockroach.

In the present study two types of descending ocellar neurons have been morphologically and physiologically identified in the cockroach Periplaneta americana: a descending ipsilateral ocellar neuron (DIO-neuron) and a descending contralateral ocellar neuron (DCO-neuron). Both DIO- and DCO-neurons possess a cell body near the ocellar tract in the protocerebrum and extend dendritic processes into the ipsilateral ocellar nerve. An axon of the DIO-neuron descends to the metathoracic ganglion, and its entire course is ipsilateral to the cell body. An axon of the DCO-neuron crosses the median plane of the protocerebrum and descends through the contralateral ventral nerve cord to the second abdominal ganglion. Both axons possess masses of branches in each ganglion as well as in the brain. Both DIO- and DCO-neurons showed no spontaneous spike discharges, and responded with a few off-spikes to ocellar illumination. They responded to various mechanical stimuli, like cercal stimulation with a train of spikes which was suppressed by ocellar illumination. Spikes of DCO-neurons caused postsynaptic potentials and spikes in some interganglionic metathoracic interneurons, and spikes in motor nerves. These data are discussed in relation to the ocellar function of the cockroach as well as in comparison with that of other insects.

Animals↗
PubMed1990

Duplicate leader exons in the mouse liver-type alkaline phosphatase gene.

A mouse genomic region corresponding to that containing the E2 exon of the rat liver alkaline phosphatase gene was isolated and characterized. A sequence comparison of these two regions showed homology of about 85% and complete conservation of sequence stretchs around the splicing-donor site. This sequence was proved to be transcribed in the mouse liver as poly(A)+RNA. These data suggest that, together with the E1-type transcript, the mouse liver-type alkaline phosphatase gene is provided with at least two alternative leader exons.

Alkaline Phosphatase↗
PubMed1989

Isolation and characterization of a rat liver alkaline phosphatase gene. A single gene with two promoters.

Structural analysis of 55 nearly full-length cDNA clones revealed heterogeneity in the 5'-untranslated regions of rat liver alkaline phosphatase mRNAs. The 5' extremities diverged into two totally unrelated sequence stretches at the position 88 nucleotides upstream of the initiation codon ATG. These two sequences, referred to as E1 and E2, were assigned on the genome about 36,000 base pairs (36 kbp) and 10 kbp upstream, respectively, of the exon coding for the 5'-most part of the common region. The gene consisted of 13 exons, including E1 and E2, and spanned about 56 kbp. The 11 exons (E3 to E13) following E1 and E2 were shared in common by the E1-type and the E2-type mRNAs. Analyses by S1 nuclease mapping and primer extension revealed the presence of two independent transcription-initiation sites specific to each of the E1 and E2 sequences. These results are interpreted as indicating a possible alternative usage of two leader exons, hence the presence of two independent promoters. Structural features of these putative promoters are described in the context of transcriptional fundamental and regulatory cis-elements.

Alkaline Phosphatase↗
PubMed1989

Sequence divergence of 5' extremities in rat liver alkaline phosphatase mRNAs.

Structural analysis of 55 nearly full-length cDNA clones of rat liver alkaline phosphatase mRNAs revealed the presence of two totally different sequence stretches at the 5'-distal region starting from the position 88 nucleotides upstream of the initiation codon ATG. Since each of these two sequences, E1 and E2, was assigned on the rat genome about 36 kilobase pairs (kbp) and 10 kbp upstream of the common exon E3, respectively, they are presumably used as alternatively spliced exons. The distances between these sequences and E3 were unusually long, as compared with other intronic distances (0.4-4 kbp) observed between successive pairs of the eleven exons which are common to both types of mRNAs. The relative ratio of E1-containing mRNA to E2-mRNA was about three in the liver after bile-duct ligation and colchicine treatment.

Alkaline Phosphatase↗
PubMed1988

Postembryonic development of the dorsal ocellus of the American cockroach.

Postembryonic development of the dorsal ocellus of the cockroach Periplaneta americana was examined. Small ocelli (20 micron in diameter) with less than 100 cells in the newly hatched nymph become adult ocelli (more than 500 micron in diameter) with more than 10,000 retinular cells, through ten to 11 nymphal stages. Thus, sequential steps of morphogenesis of rhabdomeres from loose interdigitations of apposed cell membranes to regularly arranged microvilli can be seen in the nymphal ocelli. Some retinular axons appear to extend into the brain as a bundle in the first-instar nymph. Retinular axons differentiated later also extend toward the brain, but there is no evidence that they enter it. The ultrastructure of the ocellus and component analysis of the ocellar electroretinogram suggest that functional connections between retinular axons and ocellar interneurons do not occur in the ocellar capsule until mid (the fifth or sixth)-instar nymphs. The ocellar diameter increases linearly with increase in body length during the nymphal stages, but it increases by a factor of 1.5-2.0 during the final molting: the body length of the adult is almost the same as that of the last-instar nymph. These data suggest that the function of the dorsal ocelli may be closely related to specific adult behavior such as flight.

Animals↗
PubMed1988

Retinyl and 3-dehydroretinyl esters in the crayfish retina.

We have studied chemical nature and localization of retinyl esters stored in the retina of the crayfish, Procambarus clarkii, which has a rhodopsin-porphyropsin visual pigment system. The crayfish kept at 10 degrees C in the constant dark had 3-dehydroretinal along with retinal in the retina as the chromophore of visual pigment. Both retinyl and 3-dehydroretinyl esters were found in the retina, more than 95% of them in the 11-cis configuration. Of three kinds of fatty acid detected in the esters, the major component (about 80%) was the polyunsaturated fatty acid, docosahexaenoic acid (C22 = 6). Observations with electron and fluorescence microscopy and the results of fractionation experiments showed that the esters were stored in photoreceptor cells as oil droplets. The ratio of 3-dehydroretinal/retinal as visual pigment chromophore was always higher than that of 3-dehydroretinol/retinol in the stored esters. This result suggests a mechanism of selective utilization of 3-dehydroretinol for the chromophore of visual pigment in the crayfish retina.

Animals↗
PubMed1988

Roles of bacteriochlorophyll and carotenoid synthesis in formation of intracytoplasmic membrane systems and pigment-protein complexes in an aerobic photosynthetic bacterium, Erythrobacter sp. strain OCh114.

Synthesis of bacteriochlorophyll and carotenoids was inhibited in an aerobic photosynthetic bacterium, Erythrobacter sp. strain OCh114, by alpha, alpha'-dipyridyl and diphenylamine. Formation of two pigment-protein complexes, reaction center-B870 (RC-B870) and B806, and development of the intracytoplasmic membranes of the cells were studied by spectral analysis and electron microscopy. Inhibition of bacteriochlorophyll synthesis by alpha, alpha'-dipyridyl, which was accompanied by a decrease in carotenoid synthesis, suppressed formation of intracytoplasmic membranes in the cells. Growth under illumination had a similar effect on formation of pigments and membranes. On the other hand, inhibition of carotenoid synthesis by diphenylamine did not suppress either development of the membrane system or bacteriochlorophyll synthesis. Formation of RC-B870 and B806 complexes, however, was differentially affected by blockage of carotenoid synthesis. In the presence of diphenylamine, the B806 complex was formed in a much smaller amount than the RC-B870 complex. These results suggest that, in Erythrobacter sp. strain OCh114, bacteriochlorophyll plays an essential role in intracytoplasmic membrane development, and carotenoids are important for assembly of pigment-protein complexes.

Aerobiosis↗
PubMed1986

[Gastric diverticulum invaded by carcinoma].

Diverticulum of the gastric body is uncommon and the coexistence of this lesion and gastric carcinoma much more. The authors report a case of diverticulum and carcinoma of the gastric body in a 66-year-old woman. The partially resected stomach exhibited a diverticulum, 3 X 3 X 2 cm in size, on the lesser curvature and a carcinoma of the depressed type on the posterior wall. The latter was IIc + III-like advanced carcinoma showing poor differentiation histologically and partly invading the diverticular wall, which had no muscular layer (i.e., pseudo-diverticulum). As for pseudodiverticulum, carcinoma cells invading the submucosa will reach the serosa easily. It is important not to overlook carcinomas in or around the diverticulum.

Adenocarcinoma↗
PubMed1984

Transmembrane orientation of reaction centers in proteoliposomes from Rhodopseudomonas sphaeroides.

The photochemical reaction centers from Rhodopseudomonas sphaeroides were reconstituted with soybean phospholipids into liposomes by the cholate-dialysis method. The transmembrane orientation of the reaction centers in the proteoliposomes and the morphology of the vesicles were investigated. The orientation was determined by the reduction of externally added cytochrome c after its photooxidation by a flash. The structure of the vesicles was examined by electron microscope. Discontinuous sucrose density gradient centrifugation yielded several proteoliposome fractions with different vesicular sizes and reaction-center orientations. The proportion of the reaction centers that exposed their cytochrome c reacting sites to the outside of the vesicles increased from 45 to 85% with an increase of the vesicular size. The proportion also depended on the ionic composition of the dialysis buffer. The optimal ionic environment during the dialysis (100 mM NaCl or 2.5 mM MgSO4) gave a liposome yield of 25-30% with a highly asymmetric orientation (greater than 60%). Entrapping of cytochrome c molecules into the phospholipid vesicles had little effect on the orientation of the reaction centers.

Bacterial Proteins↗
PubMed1983

Ocellar system of the insect: comparison of dorsal ocellus and lateral ocellus.

The ocellar receptor and neuropil in the dorsal ocellar system of the cockroach and the lateral ocellar system of the swallowtail butterfly larva have been compared. In the dorsal ocellus of the cockroach more than 10,000 retinular cells each with a rhabdomere are piled up one upon another without a specific pattern in the ocellar capsule. Retinular axons synapse exclusively with branches of four thick second order neurons in the lower region of the capsule. Dark granule-containing neurons, originating in the brain, also synapse with the second order neurons in the ocellar neuropil. The ocellar nerve is comprised of four thick second order processes (ca. 6-16 micron) and 20-40 thin processes (ca. 1-5 micron), which include retinular axons, collaterals of thick processes, possible third order processes and unidentified processes. Synapses occur against these processes in the ocellar nerve and in the extreme proximal region of the ocellar neuropil. Six lateral ocelli occur on both sides of head in the butterfly larva. Each ocellus contains seven retinular cells, which are grouped into three distal cells and four proximal cells, or four distal cells, two peripheral cells and one central cell by the position of their rhabdomeres. Retinular axons extend to the brain, and enter the distal optic neuropil. There are six neuropils, each of which contains the seven axons from one ocellus and a dozen or so second order processes. Of seven retinular axons, four occur peripherally and the remaining three occur centrally in the neuropil. All axons synapse with fine branches of interneurons. Second order processes together with at least three central retinular axons extend to the second optic neuropil, but the peripheral axons could not be followed there. The highly organized receptors and the neuropil in the lateral ocellar system suggest a complexly integrated function. An ocellar nerve and proximal ocellar neuropil appear like an extension of the CNS, and direct connections of retinular axons with interneurons in the CNS appear characteristic of the dorsal ocellus. This difference may be related to the distribution of the two ocellar systems: the dorsal ocelli co-exist with the compound eyes of the adult, whereas the lateral ocelli are the only photoreceptor organs of the larval insect.

Animals↗