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Biomedical subjects

N Miki

Publications and source records attributed to N Miki.

At least 127 records · Page 7Linked to original sources
PubMed1989

Developmental changes of MEKA protein and opsin in normal and rd mice.

Antisera raised against photoreceptor-specific MEKA and opsin proteins were provided for immunohistochemical studies on the retinas of normal (BJ57BL/6) and retinal degeneration (rd, C3H/He) mice. The expression of MEKA protein began at postnatal day 6 (P6) in the photoreceptor cells and gradually increased until P10 in both normal and rd mice. Thereafter the MEKA proteins in the photoreceptor cells of rd mice gradually decreased and disappeared at P18, whereas those of normal mice were increasing until P18. The time course of MEKA proteins in the photoreceptor cells of normal and rd mice was almost similar to that of opsin protein, except that the MEKA protein disappeared earlier than opsin.

Aging↗
PubMed1989

Identification of a retina-specific MEKA protein as a 33 K protein.

A photoreceptor-specific MEKA protein was purified from bovine retinal soluble fraction. The purified sample was eluted as a single peak of 74 kDa protein from a Superose column, which was dissolved into three components, MEKA protein (32 kDa), beta-(36 kDa) and gamma-(10 kDa) subunits of transducin on a SDS-PAGE. From several lines of evidence, we concluded that MEKA protein is identical with a 33k phosphoprotein reported by Lee et al (1).

Animals↗
PubMed1989

Translocation of a photoreceptor-specific MEKA protein by light.

Light-or dark-adapted retinal sections from bovine chick and mouse were provided for immunohistochemistry with antiserum against a MEKA protein which is specific to photoreceptor cells. In dark-adapted retinal sections, the anti-MEKA serum heavily stained outer segments of photoreceptor cells and lightly stained inner segments. The reverse staining pattern was observed in light-adapted retinal sections. These results indicate that the translocation of MEKA protein in a photoreceptor cell is regulated by light dark.

Animals↗
PubMed1989

Hypothalamic growth hormone-releasing factor (GRF) participates in the negative feedback regulation of growth hormone secretion.

Effects of growth hormone (GH) excess on immunoreactive hypothalamic GH-releasing factor (GRF) and somatostatin (SRIF) were studied in rats. Hypothalamic GRF content significantly reduced after 7-day daily treatment with 160 micrograms of rat GH or after inoculation of GH-secreting rat pituitary tumors, MtT-F4 for 9 or 13 days and GH3 for 3 months. Basal and 59 mM K+-evoked release of GRF from incubated hypothalami diminished, more than the content, by 43-51% in MtT-F4 tumor- or by 67-83% in GH3 tumor-bearing rats. In contrast, there was a small but significant increase in content or release of SRIF in rats harboring the GH3 or MtT-F4 tumor, respectively. These results indicate the existence of a negative feedback loop via hypothalamic GRF as well as SRIF in control of GH secretion.

Animals↗
PubMed1989

Isolation of a novel retina-specific clone (MEKA cDNA) encoding a photoreceptor soluble protein.

We have reported the isolation of clones which are candidates for retina-specific cDNAs. One of the cDNA clones, pCR-470, was further characterized. We found that mRNA corresponding to the pCR-470 was expressed only in the retina and encodes an unknown soluble protein whose molecular weight and pI are calculated to be 26,935 and 5.35, respectively. We designated it as a MEKA protein, because its amino acid sequence starts from M-E-K-A. It was found by in situ hybridization that MEKA mRNA was transcribed only in the photoreceptor cells and accumulated in the inner segments just like opsin mRNA. The MEKA cDNA was ligated with expression vector PEX 1, and a MEKA-fusion protein synthesized in E. coli was purified and used as an antigen. By the Western blot analysis anti-MEKA protein serum reacted with a soluble 32 kDa protein from bovine retina and 33 kDa for chick, but not with proteins from other tissues. Immunohistochemical study showed that anti-MEKA stained only the photoreceptor cells in bovine, chick, rat and mouse retinas.

Amino Acid Sequence↗
PubMed1989

A longitudinal study on the expression of the opsin gene in the degenerating retina of C3H/He mice.

By a combination of immunohistochemistry and in situ hybridization using a 35S-labeled opsin cDNA probe, it was revealed in rd mutant C3H/He mice that opsin mRNA is not detectable in photoreceptor cells which still exhibit opsin-immunoreactivity at later stages of retinal degeneration. This indicates that the photoreceptor cells of rd mutant mice cease to express the opsin gene at earlier stages of retinal degeneration.

Animals↗
PubMed1989

An immunohistochemical study of pinealocytes of chicks and some other lower vertebrates by means of visinin (retinal cone-specific protein)-immunoreactivity.

Visinin-like immunoreactivity was recognized in a large population of cells in the pineal organs of submammals including goldfish, frogs, turtles and chicks. In the chick pineal organ two discrete immunoreactive cells--follicular and parafollicular cells--were identified at young stages of development. Judging from the detailed morphology of the individual cells revealed by visinin-immunoreactivity and a morphological comparison with the retina and brain, it is supposed that the former represents an intermediate form closer to the photoreceptor cell and the latter yet another intermediate form closer to the neuroendocrine type. At older stages of the development both cell types assume a morphology similar to the neuroendocrine type. This finding infers that the developmental change in the morphology of the chick pinealocytes represents a condensed expression of the phylogenic development in the ontogeny.

Animals↗
PubMed1988

Presence of retina-specific proteins in the lamprey pineal complex.

The pineal complex of river lamprey reacted with the antisera raised against retina specific proteins including bovine opsin, chick visinin and frog light-sensitive cyclic GMP phosphodiesterase (PDE). Immunoreactive materials stained with anti-opsin were evenly located at the outer segment of photoreceptor cells in the pineal organ and also found in the parapineal organ. Although anti-visinin stained the pineal and parapineal photoreceptor cells, the immunopositive photoreceptor cells were observed only at the lateral portion and not at the medial portion of the pineal organ. No immunoreactive materials were found in the pineal complex by the anti-PDE, whereas the anti-PDE reacted with photoreceptor cells of the retinal tissue. The data suggest that the pineal and parapineal retinas of lamprey contain opsin- and visinin-like proteins with different distribution in their photoreceptor cell layer as found in the lamprey retinal tissue.

3',5'-Cyclic-GMP Phosphodiesterases↗
PubMed1988

Cytotoxicity of acrylamide and related compounds to mouse neuroblastoma and rat schwannoma cells.

Cytotoxicity of acrylamide and related compounds to mouse neuroblastoma N18TG-2 and rat Schwannoma RT4 cells was studied. Of nine test chemicals, acrylamide and N-hydroxymethylacrylamide were most toxic compared with others on the basis of ED50 value. Observation under phase-contrast microscopy revealed that in N18TG-2 acrylamide produced both degeneration of the cells and inhibition of cell growth, and that in RT4 it produced only inhibition of cell growth without causing any marked morphological changes. Dibutyryl cyclic AMP (dBcAMP) reduced the cytotoxicity of acrylamide to both types of cells on the basis of the dose-effect curve. Studies on the subcellular distribution of 14C-acrylamide incorporated showed that more than 90% of the total radioactivity was incorporated in the 15,000 g supernant fraction. Kinetics of acrylamide uptake by N18TG-2 cells showed that in the cells untreated with dBcAMP there were two binding sites with high and low affinity, and that after treatment with dBcAMP the site of high affinity disappeared. The situation was true for RT4 cells, the results indicating that the immature cells are more vulnerable to acrylamide than the mature cells.

Acrylamides↗
PubMed1988

Left ventricular filling characteristics in sodium-depleted and sodium-loaded patients with mild essential hypertension.

To determine left ventricular early diastolic function and transmitral blood-flow characteristics during periods of sodium depletion (50 mmol/day) and sodium loading (300 mmol/day), Doppler and standard echocardiography were performed in 13 patients with untreated mild hypertension. A high sodium intake for 7 days significantly increased (P less than 0.05) the ratio of Doppler atrial contraction phase peak velocity A to rapid filling phase peak velocity R. The isovolumic relaxation time was prolonged (P less than 0.001) and the left atrial emptying index was reduced (P less than 0.05). During sodium loading the changes in isovolumic relaxation time and the atrial emptying index were correlated with the increase in mean wall stress (r = 0.600, P less than 0.05 and r = -0.695, P less than 0.01, respectively), but not with the increase in end-diastolic volume. These results suggest that during excess salt intake, left ventricular relaxation and filling may be impaired due to a salt-induced increase in afterload in patients with mild hypertension.

Echocardiography, Doppler↗
PubMed1988

An 82-kilodalton membrane protein that inhibits the activity of neurite outgrowth factor.

Neurite outgrowth factor (NOF), an extracellular matrix glycoprotein of 700 kilodaltons (kDa), promoted neurite outgrowth from cultured ciliary ganglion (CG) neurons of chicken embryo. A fraction solubilized with Nonidet P-40 of chicken gizzard muscle membranes inhibited the neurite-promoting activity of NOF in a dose-dependent manner, but not that of laminin. Binding of CG neurons to the substratum and their survival were not affected by the extract. The inhibitory activity of the extract was abolished by treatment with trypsin or heat. The molecular size was determined to be about 82 kDa by ligand blotting. The active component was partially purified by column chromatography. It is suggested that this molecule interacts with the domain of NOF responsible for its neurite-promoting activity and may modulate NOF activity during development in vivo.

Animals↗
PubMed1988

Withdrawal of endogenous somatostatin induces secretion of growth hormone-releasing factor in rats.

Secretion of GH occurs in episodic bursts under the dual control of two hypothalamic peptides, GH-releasing factor (GRF) and GH-inhibiting factor (somatostatin, SRIF). Recent studies in rats suggest that episodic GH secretion is generated by the periodic release of GRF, which is associated with the simultaneous withdrawal of SRIF secretion. To test the possibility that GRF discharge is functionally coupled with the withdrawal of SRIF, we investigated whether acute withdrawal of SRIF can induce GRF release by the rat hypothalamus using highly specific antisera against SRIF and rat GRF. In conscious unrestrained rats, i.v. administration of SRIF antiserum at the period of the GH trough induced a rapid onset of the GH secretory surge with a peak value of 309 +/- 67 micrograms/l (mean +/- S.E.M.) 30 min after injection. Pretreatment with antiserum to rat GRF resulted in a approximately 83% suppression of the GH surge induced by SRIF antiserum without affecting the trough GH values. GRF antiserum also significantly inhibited the spontaneous GH surge. In urethane-anaesthetized rats, as in conscious rats, an acute phasic GH release was caused by SRIF antiserum despite the interference of anaesthesia with spontaneous GH secretion. A further surge-like GH secretion was not restored during the next several hours, however, with the GH secretory profile being characterized by a tonic increase in the baseline levels of GH. In the anaesthetized rat antiserum to rat GRF, having no effect on basal GH levels, similarly inhibited by approximately 66% the acute GH surge induced by SRIF antiserum and decreased by about 30% the later sustained rise in GH.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1987

A proteolytic 140-kDa fragment of neurite outgrowth factor and its cell-binding activity.

A neurite outgrowth factor (NOF) from chicken gizzard was treated with elastase, and a protease-resistant fragment of 140 kDa (F-140) with heparin-binding activity, was isolated from the digested mixture. Although F-140 showed no neurite outgrowth activity, it could bind dissociated cells from the dorsal root ganglia of chick embryos. The antiserum to F-140 inhibited the cell binding activity of native NOF in a dose-dependent manner, but not the neurite outgrowth activity. When membrane proteins from whole chick embryos were incubated with NOF or F-140, a protein band of 41 kDa was detected as a major NOF-binding component.

Animals↗
PubMed1987

Immunohistochemical cross-reactivity and electrophoretic comigration between calbindin D-27 kDa and visinin.

Calbindin D-27 kDa (previously named vitamin D-CaBP or cholecalcin) and visinin present similitude both for their purification procedure and histochemical localization. We systematically compared by histochemistry calbindin and visinin immunoreactive structures in chick and pigeon retina, in rat cerebellum and kidney and in pigeon cerebellum. The calbindin and visinin immunoreactive structures were identical except in the retina. Preabsorption of anti-visinin with purified chick or rat calbindin suppresses the labelling in every organ studied except in the photoreceptor layer of pigeon and chick retina. Such a persistence of labelling was explained by Western blotting analysis of chick-retina soluble proteins showing a pattern of 7 different proteins recognized by anti-visinin even though only one protein was recognized in rat kidney and cerebellum. Anti-visinin is thus a polyclonal antibody reacting with more than one antigen of the chick retina, one of those antigens being calbindin. Calbindin is the single antigen recognized by anti-visinin in the other tested organs. In conclusion, we present evidence that visinin is a calbindin.

Animals↗
PubMed1987

Two types of lamprey retina photoreceptors immunoreactive to rod- or cone-specific antibodies.

The localization of structures immunoreactive to antisera against opsin (OPS; a specific marker for rods) and against visinin (VIS; a specific marker for cones in the vertebrate retina) was investigated in the retina of the river lamprey (Lampetra japonica) by means of fluorescence microscopy. Different immunoreactive structures were found with the two antisera. A vitreadly located structure in the outer nuclear layer displayed OPS-like immunoreactivity, while a scleradly located one exhibited VIS-like reactivity. Thus, the two antisera applied to the retina of the river lamprey permit the distinguishing of rod and cone immunoreactive photoreceptors such as occurs typically in all vertebrate classes. The former appears in the outer segments of a type of rod cells, and the latter in the cell bodies and axons of cones.

Animals↗