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Biomedical subjects

N Naito

Publications and source records attributed to N Naito.

53 records · Page 3Linked to original sources
PubMed1987

Characterization of melanin concentrating hormone in teleost hypothalamus.

Melanin concentrating hormone (MCH) is a heptadecapeptide isolated from chum salmon (Oncorhynchus keta) pituitaries. The peptide has been isolated from whole brain extract at a low yield of 1.2 micrograms/1300 brains. MCH activity in the hypothalamus was characterised by in vitro scale bioassay and radioimmunoassay. Specificity of these assay systems was examined with neurotransmitters such as epinephrine, norepinephrine, and dopamine, hypothalamic hormones such as somatostatin, isotocin, Arg-vasotocin, oxytocin, and Arg-vasopressin, and salmon prolactin and its chymotryptic peptide or salmon PRL176-187. Among them only salmon PRL176-187 exhibited weak activities in both assays. The neurotransmitters were 10(4) to 10(5) times less potent than MCH in the bioassay. MCH concentrations in a pituitary and a hypothalamus were estimated as 5300 +/- 750 ng (ca. 106 micrograms/g) and 48 +/- 9.5 ng (ca. 1.6 micrograms/g), respectively, by radioimmunoassay. Lysyl endopeptidase digestion of the hypothalamic extract resulted in a significant increase of biological activity as well as of immunoreactivity. Gel filtration of the hypothalamic extract and subsequent enzymatic digestion revealed that the fractions at higher molecular weight were contributory to the increase in the activities.

Animals↗
PubMed1987

Structure-activity relationships of melanin-concentrating hormone.

Melanin-concentrating hormone (MCH) is a cyclic heptadecapeptide (H-Asp-Thr-Met-Arg-Cys-Met-Val-Gly-Arg-Val-Tyr-Arg-Pro-Cys-Trp-Glu-Val-O H) that induces aggregation of melanin granules within the melanophores of teleost fishes. Chemical and enzymatic modifications of MCH were conducted in order to deduce the structure-activity relationship using an in vitro bioassay with fish scales, and a radioimmunoassay using a specific antiserum to synthetic MCH. Micro-modification of MCH was employed with the natural peptide, and the modified form was purified by reverse-phase HPLC. MCH1-14 and NPS-Trp15-MCH were equipotent to MCH. Reduction and carboxamidomethylation of MCH caused complete loss of biological activity. Modification of the Tyr residue with tetranitromethane and Arg residues with 1,2-cyclohexadione significantly reduced activity, while oxidation with hydrogen peroxide caused only partial loss (10%) of activity. These results suggest that the configuration of the S-S loop is essential for activity, and Arg and Tyr may play an important role in the biological activity. In the radioimmunoassay, MCH1-14, MCH5-14 and CAM-Cys5,14-MCH showed no cross-reactivity, whereas MCH5-17 and other derivatives gave inhibition slopes parallel to the MCH standard, suggesting that the antigenic determinant of the antiserum is located in the carboxy-terminal.

Animals↗
PubMed1986

Coexistence of immunoreactivity for melanin-concentrating hormone and alpha-melanocyte-stimulating hormone in the hypothalamus of the rat.

Coexistence of immunoreactivity for melanin-concentrating hormone (MCH) and alpha-melanocyte-stimulating hormone (alpha-MSH) within rat hypothalamic neurons has been examined by the unlabeled antibody enzyme method. Neurons exhibiting both MCH- and alpha-MSH-like immunoreactivities were found in the dorsolateral hypothalamus, whereas no MCH-like immunoreactive perikarya were seen in the arcuate nucleus, where some neurons were stained with alpha-MSH antiserum. There seem to be two distinct alpha-MSH-like immunoreactive neurons in the rat hypothalamus, one exhibiting coexistence with MCH-like immunoreactivity and the other not showing any cross-reaction with MCH antiserum.

Animals↗
PubMed1984

Immunocytochemical identification of the proopiocortin-producing cells in the chum salmon pituitary with antisera to endorphin and NH2-terminal peptide of salmon proopiocortin.

The proopiocortin-containing cells were identified immunocytochemically in the chum salmon pituitary using specific antibodies raised against NH2-terminal peptide (sNPP) and COOH-terminal peptide, endorphin (sEP), of salmon proopiocortin. Immunoreactivity for both sNPP and sEP was observed in the same cells, melanotrops, in the pars intermedia. In the pars distalis, on the other hand, corticotrops were stained only with antibody to sNPP but not with that to sEP. The present results indicate that proopiocortin or a precursor molecule for NH2-terminal peptide and endorphin is biosynthesized in both melanotrops of the pars intermedia and corticotrops of the pars distalis. However, the absence of immunoreactivity of corticotrops with sEP antibody suggests that the processing of the precursor molecule in the pars distalis differs significantly from that in the pars intermedia in the chum salmon pituitary as the processings established in the two lobes in the mammalian pituitaries.

Animals↗
PubMed1983

Isolation and properties of chum salmon prolactin.

A highly purified prolactin (PRL) was isolated from the chum salmon pituitary by extraction with acid acetone, gel filtration on Sephadex G-25 and ion-exchange chromatography on CM-Sephadex C-25 with a yield of 1 mg/g of wet tissue. It was 10-15 times more potent than ovine PRL in sodium-retaining activity for juvenile rainbow trout adapted to 50% seawater. The salmon PRL emerged as a single and symmetrical peak on Sephadex G-100 with Ve/Vo = 2.0. Polyacrylamide gel electrophoresis revealed only one band at pH 4.3, whereas no band was seen at pH 7.5. The isoelectric point was estimated to be 10.3 by gel electric focusing. The circular dichroism spectrum of the salmon PRL was similar to that of tilapia PRL, showing an alpha-helix content of 50%. The salmon PRL had a molecular weight of 23,400 daltons by gel filtration and 22,300 daltons by sodium dodecyl sulfate gel electrophoresis, with a single NH2-terminal residue, isoleucine, and a single COOH-terminal residue, half-cystine. In the sequence comparison with those of mammalian PRLs and growth hormones, the clusters of invariant residues were found in both terminal regions, although the disulfide at NH2-terminal of mammalian PRLs was missing. Specific salmon PRL antisera were prepared in rabbits giving a precipitin reaction against the salmon PRL and a pituitary extract of tilapia in agar diffusion but no cross reaction with purified mammalian PRLs. The antibody was localized specifically in PRL cells of the chum salmon pituitary.

Amino Acid Sequence↗
PubMed1983

Immunocytochemical identification of the prolactin-secreting cells in the teleost pituitary with an antiserum to chum salmon prolactin.

An antiserum raised to highly purified chum salmon (Oncorhynchus keta) prolactin (sPRL) was used to identify prolactin-producing cells in the adenohypophysis of 15 species of teleosts by the immunocytochemical peroxidase-antiperoxidase method. In the chum salmon, the only pituitary cells that reacted with sPRL antibody were the PRL cells organized as follicular structures in the rostral pars distalis. When the antiserum was absorbed with sPRL, on the other hand, no immunoreactive cell was observed in the pituitary, indicating the specificity of the antiserum. Furthermore, the antibody to sPRL reacted only with PRL cells in the pituitaries of three species of salmonids, a plecoglossid, eel, carp, goldfish, killifish, tilapia, and five species of marine fishes, thus showing no species specificity of the antibody among the teleosts tested. The PRL cells of the eel decreased in number and also in immunoreactivity after adaptation to seawater for 1 month. On the other hand, highly immunoreactive PRL cells were observed in the pituitaries of marine fishes, although the cells were much fewer in number than in eels and in other fishes in fresh water.

Animals↗
PubMed1983

Clinical comparison of the AutoMicrobic system gram-positive identification card, API Staph-Ident, and conventional methods in the identification of coagulase-negative Staphylococcus spp.

In an effort to rapidly identify coagulase-negative staphylococci (CNS), a clinical comparison was conducted with the AutoMicrobic system Gram-Positive Identification Card (GPI) (Vitek Systems, Inc.), the API Staph-Ident (Analytab Products), and the conventional methods of W. E. Kloos and K. H. Schleifer (W. E. Kloos and K. H. Schleifer, J. Clin. Microbiol. 1:82-88, 1975). CNS isolates tested included 157 from blood and 33 from urine in pure culture at greater than 10(5) CFU/ml. S. epidermidis accounted for 79.6 and 60.6% of the isolates from blood and urine, respectively. S. saprophyticus was the next most frequent urine isolate (27.4%). Other CNS species were isolated from blood and urine specimens with frequencies of less than 5%. Overall, the GPI correctly identified 158 (83.2%) of the 190 CNS, whereas the Staph-Ident identified 124 (65.3%) without further testing. This resulted in the GPI and Staph-Ident correctly identifying 95.9 and 74.5% of the S. epidermidis and 100 and 33% of the S. saprophyticus, respectively. The GPI misidentified 8 (47%) of the S. hominis and S. warneri isolates as S. saprophyticus, indicating the need for novobiocin testing. These data suggest that the GPI is a more definitive method for the rapid identification of S. epidermidis than the Staph-Ident and that both systems require additional testing to identify S. saprophyticus.

Bacteriological Techniques↗
PubMed1981

In vitro induction of HLA-restricted cytotoxic T lymphocytes against autologous Epstein-Barr Virus transformed B lymphoblastoid cell line.

Cytotoxic T lymphocytes (CTL) against autologous EBV-transformed B lymphoblastoid cell line (LCL) were induced in vitro by culturing peripheral blood lymphocytes (PBL) of healthy donors together with mitomycin C-treated autologous LCL for 6 days. The cytotoxic cells developed only from the E-rosette-positive fraction but not from the negative fraction of PBL. These CTL killed autologous LCL but not PWM-stimulated autologous PBL. In addition, the CTL killed allogeneic LCL when at least 1 of the HLA-A antigens was identical with that of the LCL of CTL donor. However, identity of HLA-B and HLA-C antigens was not enough for a significant killing of allogeneic LCL. The specificity of the CTL was also confirmed by a cold target inhibition test. These results indicated that the CTL induced specifically recognized EBV-transformed cells with HLA restriction.

Animals↗
PubMed1981

Pancreatic arteriovenous malformation in a patient with gastrointestinal hemorrhage.

A 39-year old woman, with a pancreatic arteriovenous malformation (AVM) which ruptured into the pancreatic duct, was treated successfully with distal pancreatectomy and splenectomy. Histological examinations revealed an AVM with extravasation into the pancreatic ducts. A review of the cases reported to date emphasizes the importance of physical signs, individual histories and angiographic studies for early diagnosis and surgery.

Adult↗
PubMed1980

Reconstruction of the gill from single-cell suspensions of the eel, Anguilla japonica.

Minute gill arches, about 2 mm in length and with 17-20 pairs of filaments, were reconstructed from single-cell suspensions of the adult eel gill. Mixed populations of the dissociated cells were cultured with growth medium (pH 7.2-7.4) either in a Rose chamber or in a roller tube at 20 degrees C. Single cells began to aggregate within 1 h into small cell clusters, which increase in size with selective adhesion of free cells. Melanin cells were frequently observed in the aggregates. Cell aggregates containing melanin cells transformed progressively into a gill barlike structure, and then, filamentlike structures grew from the bar. Secondary lammelalike structures were observed on the filaments. With growth of the gill bar, the filaments increased in both number and length, and after about 1-2 wk minute gill arches were reconstructed with original histological properties and circulatory system.

Anguilla↗
PubMed1977

Fine-structural and functional aspects of the cerebrospinal fluid-contacting subependymal cells in the anuran hypothalamus.

Cytological characteristics of the cerebrospinal fluid (CSF)-contacting subependymal cells in the frog hypothalamus were investigated to decide whether they should be classified as neurons, sensory cells or secretory (endocrine) cells. The CSF-contacting subependymal cells exhibited morphological characteristics similar to neurons or sensory cells, which are usually supplied with axo-somatic and -dendoritic synapses from other neurons and possess somato-dendritic synapses to other neurons. Furthermore, they were provided with so-called sensory cilia. The CSF-contacting subependymal cells also exhibited several cytological secretory cell characteristics: the presence of numerous secretory granules, well-developed granular endoplasmic reticulum and Golgi apparatus in the perikaryon as well as intraventricular processes, and some figures which may be regarded as microapocrine or diacrine secretions of the secretory granules. Furthermore, the CSF-contacting subependymal cells probably sent basal cell processes to the area around the blood vessels in the neurohypophysis and, perhaps, in the infundibulum. It seemed likely that CSF-contacting subependymal cells had two or three functions of a paraneuronic nature. They were sensory to chemical or physical stimuli frmones just as endocrine cells do.

Animals↗