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Biomedical subjects

R Yamamoto

Publications and source records attributed to R Yamamoto.

At least 163 records · Page 9Linked to original sources
PubMed1997

Different responsiveness to nitric oxide-cyclic guanosine monophosphate pathway in cholinergic and tachykinergic contractions of the rabbit iris sphincter muscle.

PURPOSE: In the rabbit iris sphincter muscle, sodium nitroprusside (SNP), a nitric oxide (NO) donor, inhibits cholinergic contraction but does not affect tachykinergic contraction in vitro. The objectives of the current study were to clarify the mechanism for the different responsiveness to NO in cholinergic and tachykinergic muscular contractions, and to examine whether the mechanism for NO-induced inhibition of cholinergic muscular contraction is operative in vivo. METHODS: Iris sphincter muscle was dissected from the rabbit eye pretreated with or without endotoxin (lipopolysaccharide, LPS) in vivo. Cyclic guanosine monophosphate (cGMP) content in the iris sphincter muscle was determined by radioimmunoassay. The motor activity of the ring-shaped iris sphincter muscle was measured isometrically. Sodium nitroprusside, carboxy-2-phenyl-4,4,5,5,-tetramethyl-imidazoline-1-oxyl-3-oxide (C-PTIO, a scavenger of NO radicals), and 8-bromo cGMP (a permeable cGMP analogue) were administered between the first and second administrations of carbachol and neurokinin A, both of which had caused sustained contraction in the iris sphincter muscle. RESULTS: Sodium nitroprusside inhibited the contraction of the iris sphincter muscle caused by carbachol but had no effect on the contraction caused by neurokinin A. Application of C-PTIO significantly reduced SNP-induced cGMP accumulation in the muscle, as well as the SNP-induced inhibition of muscular contraction caused by carbachol. Neither carbachol nor neurokinin A influenced SNP-induced cGMP accumulation in the muscle. Induction of 8-bromo-cGMP significantly diminished the muscular contraction caused by carbachol but not that caused by neurokinin A. In vivo pretreatment of the eye with LPS increased, in a time-dependent manner, the cGMP accumulation in the iris sphincter muscle, which was significantly inhibited by pretreatment of NG-nitro-L-arginine methyl ester (an inhibitor of NO synthesis) in vivo. CONCLUSIONS: These results demonstrate that in rabbits the increase in cGMP accumulation induced by NO in the iris sphincter muscle is involved in the cholinergic contraction but not in the tachykinergic contraction, suggesting that different sensitivities to cGMP are essential for the different responsiveness to NO. Furthermore, the results of this study showed that the NO-cGMP pathway is operative in vivo and regulates iris sphincter muscle tone, at least when the eyes are infected with bacteria.

Animals↗
PubMed1997

Valve repair with chordal replacement for traumatic tricuspid regurgitation.

A 70-year-old woman who had fatiguability due to right heart failure seven years after receiving blunt chest trauma in a road traffic accident presented to our hospital. Preoperative echocardiography revealed severe tricuspid regurgitation resulting from prolapse of the anterior leaflet. The valve was repaired by chordal replacement with expanded polytetrafluoroethylene sutures and DeVega annuloplasty. At three months after surgery, the patient is in good clinical condition, and repeat echocardiography revealed only mild tricuspid regurgitation.

Accidents, Traffic↗
PubMed1996

Selective biochemical modification of functional residues in recombinant human macrophage colony-stimulating factor beta (rhM-CSF beta): identification by mass spectrometry.

A rapid method combining classical chemical modification with mass spectrometry was developed to identify amino acids in the recombinant human macrophage colony-stimulating factor (rhM-CSF) protein of potential import to the ligand-receptor interaction. Diethyl pyrocarbonate modification of rhM-CSF beta (under nondenaturing conditions) results in a time- and concentration-dependent loss in receptor binding and biological activity. Peptide mapping of the reaction products by mass spectrometry showed that, with low DEP:M-CSF ratios (< 50:1), there was selective modification of histidine residues, whereas at higher ratios (> 50:1), Tyr and Lys residues were also modified. The loss in rhM-CSF beta activity was directly correlated with the extent of carbethoxylation of His9 and His15, as determined by matrix-assisted laser desorption/ionization mass spectrometric molecular weight determinations (MALDIMS). For these residues mono-modification was observed. By contrast, C-terminal histidine residues His176 and His210 showed bis-modifications, the extent of which had no correlation to losses in biological activity. These data suggest the importance of residues in the A-helix (His9 and His15) to ligand-receptor binding.

Amino Acid Sequence↗
PubMed1996

Newly developed ST-T abnormalities on the electrocardiogram and chronologic changes in cardiovascular risk factors.

An ST-T abnormality on an electrocardiogram (ECG) is known to independently predict subsequent morbidity and mortality from cardiovascular diseases. But how ST-T abnormality develops in relation to chronologic changes in cardiovascular risk factors has not been fully discussed. Sixty-eight men whose ECG had been initially normal but who exhibited ST-T abnormality later (ST-T subjects) were identified among 21,579 apparently healthy adults who had undergone comprehensive health examinations for > 10 years. Echocardiography proved that 26 of 29 examinees among ST-T subjects had left ventricular hypertrophy. Antihypertensive drugs were given to 26 of the ST-T subjects. Their cardiovascular risk factors were chronologically reviewed from 10 years before the onset of definite ST-T abnormality, and were compared with those of 68 men whose ECG had remained consistently normal for 10 years (controls). Mean values of systolic and diastolic blood pressure gradually increased over 10 years (from 127/78 to 144/84 mm Hg) among ST-T subjects, but showed little change (from 122/76 to 124/77 mm Hg) during the same period in controls. The time course of blood pressure over 10 years was similar in ST-T subjects, irrespective of final blood pressure level. Mean serum cholesterol and glucose increased over 10 years in both ST-T and control subjects. Uric acid decreased over 10 years (from 6.1 to 5.6 mg/dl) only in ST-T subjects. Multivariate analysis revealed that blood pressure and uric acid before onset of ST-T abnormality were chronologically changed independent of other risk factors. The time course of risk factors may be of great importance in the development of cardiovascular disorders.

Blood Pressure↗
PubMed1996

Receptors for atrial natriuretic peptide in adrenal chromaffin cells.

Receptors for atrial natriuretic peptide (ANP) in isolated bovine adrenal chromaffin cells were characterized. 125 I-ANP specifically bound to the cells with a Kd of 103 pM and a Bmax of 5.6 fmol/10(6) cells (16.5 fmol/mg of cell protein). C-ANF, a highly selective ligand for ANP-C receptors of natriuretic peptides, did not compete for 125 I-ANP binding at concentrations up to 10nM. Chemical cross-linking of 125I-ANP to the cells showed a single molecular size of the 120 kDa binding site on SDS gel electrophoresis under reducing conditions. CNP, a specific peptide for the ANP-B receptor, was much less potent than ANP in inhibiting 125 I-ANP binding and in displacing 125 I-ANP from the 120 kDa band. These results suggest that ANP specifically binds to the ANP-A receptor of 120 kDa and that there is no ANP-C receptor in bovine adrenal chromaffin cells.

Amino Acid Sequence↗
PubMed1996

Distribution and subcellular localization of a growth inhibitory factor in hamster liver and its intracellular partner(s).

The subcellular, intralobular distributions and intracellular partner(s) of a factor which inhibits the proliferation of cell growth (Hashimoto C. et al. (1994) Biochim. Biophys. Acta 1221, 107-117) were determined in hamster livers, using a combination of immunological and biochemical techniques. The IgG fraction from an antiserum raised against the growth inhibitory factor with 37 kDa was shown to be highly specific for the antigen. The nuclear and cytosolic fractions demonstrated inhibitory effects on cell growth and Western blot analysis revealed that both fractions contained the immunoreactive 37 kDa protein with the anti-inhibitory factor IgG but microsomal and mitochondrial fractions did not. The nuclear and cytoplasmic localization of the inhibitory factor were further confirmed by immunochemical staining mediated through the immune IgG and an avidin-biotinylated horseradish peroxidase complex, the parenchymal liver cells were clearly stained, but endothelial and connective tissue cells were not. Although some staining was evident throughout the liver parenchyma, the hepatocytes with most intensively stained nuclei were located in the periportal region. In the liver from hamsters 6 days old or the regenerating hamster livers 3 days after partial hepatectomy, the staining intensity was low and the number of hepatocytes with the inhibitory factor positive nuclei was very few compared with the adult hamster livers. In primary cultures of the isolated hepatocytes from adult hamster the inhibitory factor disappeared from nuclei after incubation for 24-48 h. The extracts of hepatic nuclei from adult hamsters were immunoprecipitated with either the anti-growth inhibitory factor IgG or a monoclonal antibody to the RM protein. The growth inhibitory factor and the RB protein coprecipitated in each case, implying that the proteins were complexed with each other in the nuclei. The RB protein family is composed of two sets of species, an un- or underphosphorylated species and a hyperphosphorylated one. It was suggested that the factor bound preferentially to the un- or underphosphorylated member of the family.

Animals↗
PubMed1996

The later administration of progesterone more rapidly activates dormant mouse mammary tumor cells initiated by 3'-methyl-4-dimethylaminoazobenzene.

Implantation of progesterone at 1 month of age induced the development of mammary tumors in female C57BL/6 x DS-F1 mice that had been treated with 3'-methyl-4-dimethylaminoazobenzene (3'-Me-DAB) neonatally, and that had undergone ovariectomy and received implants of estradiol-17beta (E2) pellets at 1 month of age, and the incidence of mammary tumors became 100% at 15 months of age. On the other hand, no mammary tumors developed in these mice with implants of E2 pellets alone. Implantation of progesterone alone also induced no mammary tumors in mice that had been treated with 3'-Me-DAB neonatally, and had undergone ovariectomy at 1 month of age. Implantation of progesterone at 4, 6, 8, and 10 months of age also caused the prompt development of mammary tumors as implantation of progesterone at 1 month of age. When ages at which the incidence became 50% were estimated on curves of the incidences, these ages on implantation of progesterone at 1, 4, 6, 8, and 10 were about 11, 13, 14, 14, and 14 months of age. These results suggest that progesterone together with estrogen promotes the development of mammary tumors induced by 3'-Me-DAB, and that the later progesterone is administered, the more rapidly it activates dormant mammary tumor cells initiated by 3'-Me-DAB.

Aging↗
PubMed1996

Up-regulation of functional voltage-dependent sodium channels by cyclic AMP-dependent protein kinase in adrenal medulla.

Treatment of cultured bovine adrenal chromaffin cells with dbcAMP increased [3H]STX binding with an EC50 of 126 microM and a half-effective time of 12 h; dbcAMP (1 mM x 18 h) raised the Bmax approximately 1.5-fold without altering the Kd value. Forskolin (0.1 mM) or IBMX (0.3 mM) also increased [3H]STX binding, while dbcGMP had no effect. Effects of dbcAMP and forskolin were abolished by H-89, an inhibitor of cAMP-dependent protein kinase. Cycloheximide (10 microgram/ml) and actinomycin D (10 microgram/ml), inhibitors of protein synthesis, nullified the stimulatory effect of dbcAMP, whereas tunicamycin, an inhibitor of protein glycosylation, had no effect. Treatment with dbcAMP augmented veratridine-induced 22Na influx, 45Ca influx via voltage-dependent Ca channels and catecholamine secretion, while the same treatment did not alter 45Ca influx and catecholamine secretion caused by high K (a direct activation of voltage-dependent Ca channels) [25]. Na influx via single Na channel calculated from 22Na influx and [3H]STX binding was quantitatively similar between non-treated and dbcAMP-treated cells. Brevetoxin allosterically enhanced veratridine-induced 22Na influx approximately 3-fold in dbcAMP-treated cells as in non-treated cells. These results suggest that cAMP-dependent protein kinase is involved in the modulation of Na channel expression in adrenal medulla.

Adrenal Medulla↗
PubMed1996

Phenylethanoid glycosides from Stachys officinalis.

From the aerial parts of Stachys officinalis, six new phenylethanoid glycosides, named betonyosides A-F, and six known phenylethanoid glycosides, acetoside, acetoside isomer, campneosides II, forsythoside B and leucosceptoside B, were isolated and their structures were elucidated from spectroscopic and chemical evidence. Campneosides II were separated into two epimers.

Carbohydrate Conformation↗
PubMed1996

Erythropoietin, granulocyte-colony stimulating factor, interleukin-1 beta and interleukin-6 during the normal menstrual cycle.

OBJECTIVE: Menstruation and ovulation are the main events during the menstrual cycle. Menstruation may influence the complete blood count because of its blood loss. Since ovulation is an inflammatory-like phenomenon, white blood cell count may change during ovulation. For these reasons, we have investigated the complete blood count and peripheral serum concentrations of associated cytokines during the normal menstrual cycle. MATERIALS AND METHODS: Normal healthy female volunteers (N = 9; age, 21-33 years) with menstrual cycles of 25-33 days recorded basal body temperature every day and venous blood samples were collected three times per week. Complete blood count was performed and erythropoietin, granulocyte-colony, stimulating factor, interleukin-1 beta, interleukin-1 beta, interleukin-6 and hormones (FSH, LH, estradiol and progesterone) were measured. RESULTS: The red blood cell, total white blood cell, granulocyte and platelet counts showed no statistically significant changes during the menstrual cycle when using analysis of variance with the Scheffe F-test. No changes in erythropoietin, interleukin-1 beta and interleukin-6 were seen throughout the menstrual cycle. In contrast, serum granulocyte-colony stimulating factor concentrations increased significantly to 28.0 +/- 3.1 pg/ml (mean +/- S.E.M.) during the ovulatory phase, compared to 10.7 +/- 0.6 pg/ml in other phases. CONCLUSION: These results indicate that menstrual blood loss does not affect the complete blood count and suggest that granulocyte-colony stimulating factor plays and important role in the mechanism of ovulation.

Adult↗
PubMed1996

Protein kinase C-mediated down-regulation of voltage-dependent sodium channels in adrenal chromaffin cells.

Treatment of cultured bovine adrenal chromaffin cells with 12-O-tetradecanoylphorbol 13-acetate (TPA), an activator of protein kinase C (PKC), decreased [3H]saxitoxin ([3H]STX) binding in a concentration (IC50 = 19 nM)- and time (t1/2 = 4.5 h)-dependent manner. TPA (100 nM for 15 h) lowered the Bmax of [3H]STX binding by 53% without altering the KD value. Phorbol 12,13-dibutyrate (PDBu) also reduced [3H]STX binding, whereas 4 alpha-TPA, an inactive analogue, had no effect. The inhibitory effect of TPA was abolished when H-7 (an inhibitor of PKC), but not H-89 (an inhibitor of cyclic AMP-dependent protein kinase), was included in the culture medium for 1 h before and during TPA treatment. Simultaneous treatment with TPA in combination with either actinomycin D or cycloheximide, an inhibitor of protein synthesis, nullified the effect of TPA. TPA treatment also attenuated veratridine-induced 22Na+ influx but did not alter the affinity of veratridine for Na channels as well as an allosteric potentiation of veratridine-induced 22Na+ influx by brevetoxin. These results suggest that an activation of PKC down-regulates the density of Na channels without altering their pharmacological features; this down-regulation is mediated via the de novo synthesis of an as yet unidentified protein(s), rather than an immediate effect of Na channel phosphorylation.

Adrenal Glands↗
PubMed1996

Up-regulation of functional voltage-dependent sodium channels by insulin in cultured bovine adrenal chromaffin cells.

Treatment of cultured bovine adrenal chromaffin cells with 100 nM insulin raised [3H]saxitoxin ([3H]-STX) binding in a time-dependent manner (t1/2 = 26 h). Insulin (100 nM for 4 days) increased the Bmax of [3H]STX binding by 49% without changing the KD value and also augmented the maximal influx of 22Na+ due to 560 microM veratridine by 39% without altering the EC50 value of veratridine. The stimulatory effect of insulin on 22Na+ influx was concentration-dependent with an EC50 of 3 nM, whereas insulin-like growth factor (IGF)-I had little effect at 1 nM. Ptychodiscus brevis toxin-3 allosterically potentiated veratridine (100 microM)-induced 22Na+ influx by approximately twofold in both insulin-treated cells and untreated cells. Veratridine-induced 45Ca2+ influx via voltage-dependent Ca2+ channels and catecholamine secretion were also enhanced by insulin treatment, whereas insulin did not alter nicotine-induced 22Na+ influx via the nicotinic receptor-ion channel complex and high-K+ (direct activation of voltage-dependent Ca2+ channels)-induced 45Ca2+ influx. Stimulatory effects of insulin on [3H]-STX binding and veratridine-induced 22Na+ influx were nullified by simultaneous treatment with either 5,6-dichlorobenzimidazole riboside, an inhibitor of RNA synthesis, or cycloheximide, an inhibitor of protein synthesis, whereas insulin treatment did not appreciably increase the level of mRNA encoding the Na+ channel alpha-subunit. These results suggest that the binding of insulin to insulin (but not IGF-I) receptors mediates the up-regulation of functional Na+ channel expression at plasma membranes; this up-regulation may be due, at least in part, to the de novo synthesis of an as yet unidentified protein(s).

Adrenal Medulla↗
PubMed1996

Effects of hypergravity on growth and cell wall properties of cress hypocotyls.

Elongation growth of etiolated hypocotyls of cress (Lepidium sativum L.) was suppressed when they were exposed to basipetal hypergravity at 35 x g and above. Acceleration at 135 x g caused a decrease in the mechanical extensibility and an increase in the minimum stress-relaxation time of the cell wall. Such changes in the mechanical properties of the cell wall were prominent in the lower regions of hypocotyls. The amounts of cell wall polysaccharides per unit length of hypocotyls increased under the hypergravity condition and, in particular, the increase in the amount of cellulose in the lower regions was conspicuous. Hypergravity did not influence the neutral sugar composition of either the pectin or the hemicellulose fraction. The amount of lignin was also increased by hypergravity treatment, although the level was low. The data suggest that hypergravity modifies the metabolism of cell wall components and thus makes the cell wall thick and rigid, thereby inhibiting elongation growth of cress hypocotyls. These changes may contribute to the plants' ability to sustain their structures against hypergravity.

Acceleration↗
PubMed1996

Surgical treatment of complex fracture of the proximal humerus.

Sixteen patients aged 19 to 63 years (average, 52 years) were observed from 1.8 to 5.6 years (average, 3.8 years) after open reduction and internal fixation with or without external fixation of 3- and 4-part displaced fractures of the proximal humerus. There were 12, 3-part displaced greater tuberosity and surgical neck fractures with 6 concomitant dislocations. Four cases were 4-part fractures with 3 concomitant dislocations. Fixation was achieved with heavy sutures or wire that incorporated the rotator cuff tendon, tuberosities, and shaft combined with threaded pins or Hoffmann external fixation to enhanced stability for early rehabilitation. According to Neer's criteria, 14 (87%) of the 16 patients had satisfactory or excellent results. Two (13%) of the 16 had unsatisfactory results. The use of a technique of limited soft tissue dissection and internal fixation with or without external fixation achieved good fracture stability and a high percentage of satisfactory results. The limitations of the procedure include (1) patients who could not tolerate anesthesia, (2) complex displaced fractures in older patients with osteoporotic bone that cannot hold pins or external fixation, (3) older patients with 4-part fracture dislocations in which avascular necrosis of the humeral head occurs frequently and in which a subsequent endoprosthesis insertion is inappropriate if osteosynthesis fails, and (4) head splitting fractures. The described approach provides an alternative method for the treatment of complex displaced fractures of the proximal humerus.

Adult↗
PubMed1996

Biochemical characterization of alpha-fetoprotein and other serum proteins produced by a uterine endometrial adenocarcinoma.

A high serum alpha-fetoprotein (AFP) level was found in a patient with endometrial adenocarcinoma of the uterus, which appeared to be hepatoid on histological examination. The AFP of this unusual patient was purified by immunoaffinity chromatography and characterized. The electrophoretic profiles on sodium dodecyl sulfate-polyacrylamide get electrophoresis both before and after glycopeptidase F treatment were indistinguishable from those of a hepatoma AFP. This indicates that the patient's AFP was also composed of a single polypeptide chain of Mr 67,000 and an N-linked sugar chain of Mr 3,000. Amino acid sequence analyses of this AFP, and of AFP from hepatoma and umbilical cord serum indicated that the N-terminal sequences were essentially the same. The sequence, Arg-Thr-Leu-His-Arg-Asn-Glu-Tyr-Gly-Ile, was slightly different from previous reports, but matched that deduced from the cDNA sequence. AFP isoforms due to microheterogeneity of the sugar chain were analyzed by lectin affinity electrophoresis using a series of lectins. The AFP isoform profiles were distinct from those of proteins derived from cord serum, hepatoma, yolk sac tumor and gastric cancer. The reverse-transcription of RNA from the tumor tissue followed by a polymerase chain reaction using primers with AFP-specific sequences gave a product of the size and nucleotide sequence expected for AFP. mRNAs possessing the requisite sequences for albumin and transferrin syntheses were also detected in the tumor. The expression of these hepatocyte-specific proteins supported the hepatoid nature of this tumor.

Adenocarcinoma↗
PubMed1996

Alpha-fetoprotein production by a hepatoid adenocarcinoma of the uterus.

A case of a 62 year old Japanese woman with an endometrial adenocarcinoma producing alpha-fetoprotein (AFP) is described. Microscopically, the tumour was composed of a major medullary portion and a minor tubular adenocarcinoma which had invaded the myometrium, the myometrial lymphatics and blood vessels. Neoplastic cells in the medullary portion were polygonal with glycogen-rich cytoplasm. Vascular permeation by neoplastic cells was prominent. Extensive hepatoma-like features were observed. The tumour cells lacked features suggestive of a diagnosis of embryonal carcinoma or endodermal sinus tumour. The production of AFP by the tumour cells was demonstrated immunohistochemically using the PAP technique. Only two cases of AFP producing endometrial adenocarcinomas have been reported previously.

Adenocarcinoma↗