Search PubMed⌕ Search

Biomedical subjects

R Nishi

Publications and source records attributed to R Nishi.

At least 37 records · Page 2Linked to original sources
PubMed1996

Does ciliary neurotrophic factor serve a different function in the rat versus the chicken?

Ciliary neurotrophic factor (CNTF) was first identified as a trophic activity that was able to support the survival of chick ciliary ganglion (CG) neurons in vitro. CNTF from rabbit and rat were subsequently purified from sciatic nerve and their cDNA sequences cloned. Another trophic molecule for CG neurons was identified as a growth promoting activity (GPA). GPA was purified from chicken sciatic nerve and cloned from embryonic chicken eye. The rat and rabbit CNTFs have a considerable amount of structural homology and are not secreted in significant quantities, whereas GPA is less similar in that it is only 49% homologous with rabbit and rat CNTF and is secreted by cells. This review discusses other similarities and differences in biological activities, molecular structure, receptor signaling and cellular distribution between CNTF and GPA and suggests that these molecules may have different functions in rodents and birds.

Amino Acid Sequence↗
PubMed1995

Inhibitor of protein synthesis phase-shifts the circadian oscillator and inhibits the light induced-phase shift of the melatonin rhythm in pigeon pineal cells.

Our recent study showed that dissociated pigeon pineal cells expressed a circadian oscillation of melatonin release which entrained to light-dark cycle and persisted under constant darkness in vitro, suggesting that pigeon pineal cells contain the circadian oscillator and photoreceptors. Six-hour pulses of anisomycin, an inhibitor of protein synthesis that acts at hte 80S ribosomal subunit, induced steady state and phase depended phase shifts of the circadian oscillation of melatonin release. The phase advances and delays were produced at CT 7.9 h and between CT 18.6 h and CT 4.5 h, respectively. The magnitudes of phase shifts were dose dependent and correlated with the magnitudes of inhibition of protein synthesis determined at CT 4.5 h. Furthermore, anisomycin blocked the light-induced phase advance. Two dimensional electrophoresis revealed that synthesis of two proteins with Mr of 17,600 and less than 5000 are stimulated by a 3-h light pulse at CT 18.6 h which corresponds to the light-induced phase advance region. These results suggest that 80S ribosomal protein synthesis is involved in normal or light-entrainment functions of the circadian oscillator in pigeon pineal cells.

Animals↗
PubMed1995

Activin A and follistatin expression in developing targets of ciliary ganglion neurons suggests a role in regulating neurotransmitter phenotype.

The avian ciliary ganglion contains choroid neurons that innervate choroid vasculature and express somatostatin as well as ciliary neurons that innervate iris/ciliary body but do not express somatostatin. We have previously shown in culture that activin A induces somatostatin immunoreactivity in both neuron populations. We now show in vivo that both targets contain activin A; however, choroid expressed higher levels of activin A mRNA. In contrast, follistatin, an activin A inhibitor, was higher in iris/ciliary body. Iris cell-conditioned medium also contained an activity that inhibited activin A and could be depleted with anti-follistatin antibodies. These results suggest that development of somatostatin is limited to choroid neurons by differential expression of activin A and follistatin in ciliary ganglion targets.

Activins↗
PubMed1995

Analysis of function and expression of the chick GPA receptor (GPAR alpha) suggests multiple roles in neuronal development.

Growth promoting activity (GPA) is a chick growth factor with low homology to mammalian ciliary neurotrophic factor (CNTF) (47% sequence identity with rat CNTF) but displays similar biological effects on neuronal development. We have isolated a chick cDNA coding for GPA receptor (GPAR alpha), a GPI-anchored protein that is 70% identical to hCNTFR alpha. Functional analysis revealed that GPAR alpha mediates several biological effects of both GPA and CNTF. Soluble GPAR alpha supports GPA- and CNTF-dependent survival of human TF-1 cells. In sympathetic neurons, GPAR alpha mediates effects of both GPA and CNTF on the expression of vasoactive intestinal peptide (VIP) as shown by the inhibition of GPA- and CNTF-mediated VIP induction upon GPAR alpha antisense RNA expression. These results demonstrate that GPAR alpha is able to mediate effects of two neurokines that are only distantly related. GPAR alpha mRNA expression is largely restricted to the nervous system and was detected in all neurons that have been shown to respond to GPA or CNTF by increased survival or differentiation, i.e. ciliary, sympathetic, sensory dorsal root, motoneurons, retinal ganglion cells and amacrine cells. Interestingly, GPAR alpha mRNA was additionally found in neuronal populations and at developmental periods not known to be influenced by GPA or CNTF, suggesting novel functions for GPAR alpha and its ligands during neurogenesis and neuron differentiation.

Amino Acid Sequence↗
PubMed1995

Comparison of agar-gel precipitin responses among strains of fowl adenovirus using antigens prepared from chorioallantoic membranes and chicken kidney cell cultures.

Agar-gel precipitin responses obtained for serologically different strains of fowl adenovirus (FAV) in tests using antigens prepared from FAV-infected chorioallantoic membranes (CAM antigen) and chicken kidney cell cultures (CKC antigen) were compared. Findings showed that both types of antigens exhibited less sensitivity to heterologous than to homologous antisera and that quantitative differences in sensitivity were present between serotypes. CAM antigens were more sensitive than CKC antigens to heterologous antisera. Polyvalent CAM antigens containing 2 or 3 antigens increased sensitivity in testing of field serum samples, resulting in a higher rate of detection.

Adenoviridae Infections↗
PubMed1995

Image forming optics with a common aperture for fast switching between TEM magnified image and selected area diffraction.

Image-forming optics that can switch between a magnified image and its diffraction pattern without any movement of aperture is proposed. Both the images are alternately taken and are simultaneously shown in a monitor. This type of optics is applied to the design of an ultrahigh-voltage electron microscope (H-3000) and is tested at 100 kV TEM.

Image Processing, Computer-Assisted↗
PubMed1994

Comparison of circadian oscillation of melatonin release in pineal cells of house sparrow, pigeon and Japanese quail, using cell perfusion systems.

We compared the circadian oscillation of melatonin release from cultured pineal cells in Japanese quail, pigeon and house sparrow, to determine whether the pineal gland of these species retains the circadian oscillator function in vitro. After dissociated pineal cells have been cultured for 4 days under 12 h: 12 h light-dark (LD) cycle, they were perfused at a flow rate of 0.25 ml/h for 6-7 days under LD or constant darkness (DD). Melatonin release increased during the dark period and low during the light period in all pineal cell cultures. Under DD conditions, the circadian rhythm of melatonin release persisted for up to 3-4 cycles in pigeon and house sparrow pineal cells, but the amplitude of the rhythm decreased gradually. However, in Japanese quail pineal cell culture the circadian oscillation of melatonin release was weak or abolished under DD conditions. These results strengthen the argument that the avian pineal gland's role in circadian organization differs between species. The direct demonstration of species-specific differences in the mechanism of the circadian oscillation of melatonin release from pineal cells should provide a useful model for the analysis of the pineal's circadian system at the cellular level.

Animals↗
PubMed1994

Cellular distribution, subcellular localization and possible functions of basic and acidic fibroblast growth factors.

The distribution in the rat nervous system of acidic and basic fibroblast growth factors (FGFs) was analysed by a combination of biochemical and anatomical methods. Acidic FGF (aFGF) was found to be present exclusively in specific neuronal populations, such as motor neurons and basal forebrain cholinergic neurons. Basic FGF (bFGF) was found in astrocytes and in neurons in hippocampal area CA2. Within labelled astrocytes and CA2-neurons, bFGF was detected in both the cytoplasm and the nucleus. The levels of intracellular bFGF were manipulated by antisense oligonucleotide treatment of cultures of developing neural crest cells. Results indicated that the amount of melanogenesis in the cultures is likely to be regulated by intracellular, possibly nuclear bFGF.

Animals↗
PubMed1994

Target-derived molecules that influence the development of neurons in the avian ciliary ganglion.

The developing avian ciliary ganglion has been a particularly amenable system for the identification, isolation, and characterization of putative target-derived molecules that mediate retrograde interactions. To date a number of biochemically distinct activities that regulate neuronal survival, transmitter phenotype, and chemosensitivity of ciliary ganglion neurons have been identified. Of these, only two survival-promoting molecules have been purified to homogeneity: ciliary neurotrophic factor and a related molecule, growth-promoting activity. A somatostatin-inducing activity found in cultured choroid cells is very likely to be chick activin A. Other molecules that regulate acetylcholine and acetylcholine receptor expression comigrate on a gel filtration column at a molecular weight of 50-60 kD, but they have yet to be isolated. Once molecules that mimic retrograde influences are identified, a number of criteria must be met before their physiological significance can be established. These criteria are (1) availability of the molecule from the target at the appropriate time in development; (2) ability of the neurons to respond to the molecule at the appropriate time in development; (3) demonstration that blocking the activity or availability of the molecule is able to block the target-derived developmental change expressed in the neurons. Of the molecules that are thought to retrogradely influence ciliary neuron development, only growth-promoting activity is known to meet criteria 1 and 2, and experiments are currently underway to test whether inhibition of growth-promoting activity in vivo will exacerbate normal cell death.

Animals↗
PubMed1994

Circadian oscillation of 64-kDa polypeptide in the rat suprachiasmatic nucleus.

In cell suspensions of suprachiasmatic nucleus harvested every 3 hr from rats kept under 12 hr: 12 hr light-dark cycle and constant darkness, we have detected a M(r) 64-kDa protein whose synthesis exhibits two distinct daily peaks in SDS-PAGE. Analysis of densitometer tracings revealed that the synthesis of other proteins was independent of the time of day or not reproducible. Maximum synthesis of the 64-kDa polypeptide occurred at around CT6 and CT21, which are almost coincident with the phase advance regions of circadian activity rhythm induced by anisomycin and light pulses [15], respectively. These results suggest that the 64-kDa protein in SDS-PAGE may be a part of the circadian clock mechanism.

Animals↗
PubMed1993

GPA and CNTF produce similar effects in sympathetic neurones but differ in receptor binding.

The effects of growth promoting activity (GPA) on sympathetic neurone development were investigated in vitro and compared with the effects of ciliary neurotrophic factor (CNTF). GPA interfered with sympathetic neurone proliferation and induced the expression of vasoactive intestinal peptide (VIP) in neurones from 7-day-old (E7) chick embryos. The biological effects observed with saturating levels of GPA are indistinguishable from the effects of CNTF. The effects on VIP expression suggest that GPA may be involved in the specification of sympathetic neurone phenotypes. Whereas half maximal effects are achieved at lower concentrations of GPA than CNTF, GPA competes less efficiently than CNTF for the binding of 125I-labelled CNTF. This suggests similar, but not identical interactions of CNTF and GPA with receptors on chick sympathetic neurones.

Animals↗
PubMed1993

The primary structure of two proteins from the large ribosomal subunit of rice.

We isolated two rice cDNAs which encode an open reading frame of 389 amino acids. Their deduced amino acid sequence corresponded to the ribosomal protein (r-protein). A comparison of amino acid sequence shows that the deduced amino acid sequence of one cDNA is homologous to Arabidopsis, yeast and the rat r-protein L3. Another encoded products with a high degree of homology to the rat r-protein L7A and yeast r-protein L4.

Amino Acid Sequence↗
PubMed1993

The primary structure of two proteins from the small ribosomal subunit of rice.

We isolated two rice cDNAs which encode an open reading frame of 117 amino acids or 82 amino acids. Their deduced amino acid sequence correspond to the ribosomal proteins (r-protein). A comparison of the amino acid sequence shows that the deduced amino acid sequence of one cDNA is homologous to the rat r-protein S20 and Xenopus r-protein S22. Another encoded products with a high degree of homology to the rat r-protein S21 and the yeast r-protein YS25.

Amino Acid Sequence↗
PubMed1993

Isolation and characterization of a rice cDNA which encodes a ubiquitin protein and a 52 amino acid extension protein.

We isolated a rice cDNA clone encoding the ubiquitin protein fused to a ribosomal protein. This clone encodes a single ubiquitin polypeptide and extension protein of 53 amino acids. This extension protein shows a high degree of homology with those of the yeast ubil or ubi2 gene, both of which encode the same protein. Northern blot analysis suggested that the expression pattern of this gene is more similar to other ribosomal protein genes not linked to ubiquitin protein than to the polyubiquitin gene.

Amino Acid Sequence↗
PubMed1993

Isolation and characterization of a rice cDNA clone encoding ATP/ADP translocator.

We isolated a rice cDNA clone which encodes an open reading frame of 382 amino acids. Its deduced amino acid sequence corresponds to an ATP/ADP translocator protein. Its homology with a maize ATP/ADP translocator was 83.9% in nucleotide sequence, and 90.2% of the amino acid level. Expression of this gene is regulated by such external stresses as salinity and low temperature.

Amino Acid Sequence↗
PubMed1993

Induction of somatostatin immunoreactivity in cultured ciliary ganglion neurons by activin in choroid cell-conditioned medium.

We have previously shown that the expression of somatostatin-like immunoreactivity in cultured ciliary ganglion neurons is stimulated by a macromolecule found in choroid cell-conditioned medium (ChCM). Here, we present the following evidence that this somatostatin-stimulating activity (SSA) is activin: human recombinant activin induces somatostatin-like immunoreactivity in CG neurons; ChCM induces hemoglobin synthesis in K562 cells, a biological activity characteristic of activin; activin A-specific antibodies recognize a protein in ChCM; cultured choroid cells contain activin RNA; and SSA is inhibited by follistatin, a specific activin-binding protein. Thus, activin is likely to be a neurodifferentiation factor for CG neurons in vivo.

Activins↗