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Biomedical subjects

N Yamaguchi

Publications and source records attributed to N Yamaguchi.

At least 433 records · Page 24Linked to original sources
PubMed1992

Golgi retention of a trans-Golgi membrane protein, galactosyltransferase, requires cysteine and histidine residues within the membrane-anchoring domain.

Galactosyltransferase (GT; UDPgalactose:beta-D-N-acetylglucosaminide beta-1,4-galactosyltransferase, EC 2.4.1.22) is a type II membrane-anchored protein composed of a short N-terminal cytoplasmic tail, a signal/membrane-anchoring domain, and a stem region followed by a large catalytic domain including the C terminus. To identify the peptide segment and key amino acid residues that are critical for Golgi localization of GT, the expression vector pGT-hCG was designed to encode the entire GT molecule fused to the C-terminal region of human chorionic gonadotropin alpha subunit (hCG alpha) as a reporter. COS-1 cells transfected with pGT-hCG expressed the chimera in the Golgi region, as detected by immunofluorescence microscopy using anti-hCG antibodies. Two deletion mutants, delta tail and delta stem, which are lacking most of the N-terminal cytoplasmic tail or 10 amino acids immediately after the membrane-anchoring domain, were localized in the Golgi. Replacement mutations of the membrane-anchoring domain of GT showed that the second quarter of the transmembrane domain or Cys29-Ala30-Leu31-His32-Leu33 is necessary for GT to be retained in the Golgi. Furthermore, the point mutants Cys29----Ser29 and His32----Leu32 were partially transported to the plasma membrane, whereas an Ala30-Leu31----Phe30-Gly31 mutant was localized in the Golgi. Finally, a double mutant, Cys29/His32----Ser29/Leu32, was found to be transported efficiently to the plasma membrane. The signal-anchoring domain of the transferrin receptor, a type II plasma membrane protein, was then replaced by portions of the GT transmembrane domain. Although the Cys-Xaa-Xaa-His sequence by itself cannot retain the transferrin receptor in the Golgi, the cytoplasmic half of the transmembrane domain of GT was partially capable of retaining the transferrin receptor in the Golgi. These results suggest that the cytoplasmic (or N-terminal) half of the transmembrane domain of GT contributes to the Golgi retention signal and that particularly Cys29 and His32 in this region are critical for GT to be retained in the Golgi.

Amino Acid Sequence↗
PubMed1992

Behavioral and electroencephalographic effects of a serotonin receptor agonist (5-methoxy-N,N-dimethyltryptamine) in a feline model of photosensitive epilepsy.

The effects of a serotonin (5-HT) receptor agonist, 5-methoxy-N,N-dimethyltryptamine (5-MeODMT), on epileptic photosensitivity were studied in the lateral geniculate-kindled cat. 5-MeODMT at 4 mg/kg significantly suppressed photically induced myoclonus, but not paroxysmal EEG activity, at 0.5-1 h after injection. This antiepileptic effect was seen in association with the appearance of behavioral signs similar to those seen in the 5-HT syndrome. The present data provide further evidence that 5-HT plays an important role in photosensitive epilepsy, and suggest that the inhibitory effect of 5-MeODMT on photosensitivity results from its agonist action at 5-HT1 receptors.

Animals↗
PubMed1992

Characterization of 21 newly established esophageal cancer cell lines.

Twenty-one esophageal cancer cell lines (KYSE series) have been established from the resected specimens of patients with esophageal cancer. Three lines, KYSE-30, KYSE-50, and KYSE-70, were derived from the implanted tumor of nude mice (initial passage); others were derived from resected specimens. Each cell line was morphologically distinct. Detailed cytogenetic analysis indicated that each cell line was karyotypically unique, and DNA fingerprint analysis showed no cross-contamination among cells. Doubling time ranged from 13.7 to 75.5 hours, and modal chromosome numbers ranged from 46 to 120. Most cell lines grew in monolayer, but two cell lines (KYSE-50 and KYSE-360) grew as floating cell aggregates. No correlation was demonstrated between the establishment of cell lines and cell differentiation. These cell lines are the first reported to be homogeneous and individually unique and may provide a useful model for the study of human esophageal cancer.

Animals↗
PubMed1992

Deficiency of P62, a putative collagen receptor, in platelets from a patient with defective collagen-induced platelet aggregation.

Recently, we described a platelet antibody against a putative collagen receptor (P62), which was found in a patient with idiopathic thrombocytopenic purpura (ITP) (Blood 69:1712). We now report a deficiency of the P62 receptor in a young man whose platelets showed defective collagen-induced platelet aggregation. He had a mild bleeding tendency and slight thrombocytopenia. The results of coagulation and fibrinolysis studies were normal. The patient's platelets were partially unresponsive to collagen, although aggregation in response to ADP, thrombin, ristocetin, and calcium ionophore (A23187) was almost normal. Adhesion of his platelets to bovine collagen was markedly reduced. Addition of collagen caused no synthesis of thromboxane (TX)B2 in platelet rich plasma (PRP) from this patient. Furthermore, collagen produced no rise of cytosolic free calcium ([Ca2+]i) in fura2-loaded platelets. In contrast, thrombin caused TXB2 formation and an increase of [Ca2+]i in his platelets. These results suggest defective interaction between the platelets and collagen. The IgG from the ITP-patient induced irreversible aggregation in normal PRP, but caused no aggregation of the young man's platelets. Immunoblot studies showed that normal platelets had antigens with a molecular weight of 62 KDa under reducing conditions and of 57 KDa under nonreducing conditions. In contrast, the young man's platelets had no P62 band, although GPIa/IIa and thrombospondin were normally present. These results indicate that impaired collagen-induced aggregation in the patient's platelets was due to a deficiency of P62 and confirm that P62 may play a crucial role as a collagen receptor in platelet activation.

Adenosine Triphosphate↗
PubMed1992

Biodistribution of monoclonal antibody A7 and its F(ab')2 fragment in athymic nude mice bearing human pancreatic carcinoma.

Xenografts of a human pancreatic carcinoma cell line, HPC-YS, which reacted with the monoclonal antibody (MAb) A7, were used to investigate the in vivo localization of radioiodinated MAb A7 after intraperitoneal injection. MAb A7 localized to the tumor 4 days and 8 days after injection with a tissue/blood ratio of 1.45 +/- 0.18 and 2.04 +/- 0.20, respectively. The accumulation of MAb A7 in the tumor was 5%/g and 3.3%/g of the injected dose on day 4 and on day 8, respectively. In contrast, the F(ab')2 fragment of MAb A7 localized to the tumor 4 days after intravenous injection with a tissue/blood ratio of 14.2. The accumulation of the F(ab')2 fragment in the tumor was 1.2%/g of the injected dose. These results suggested that MAb A7 might be a suitable carrier of anticancer drugs for immunotargeting chemotherapy and that the F(ab')2 fragment might be potentially useful for the immunodetection of human pancreatic carcinomas.

Animals↗
PubMed1992

Expression of the cell surface antigen detected by the monoclonal antibody A7 in pancreatic carcinoma cell lines.

In a previous study, we used a murine monoclonal antibody, A7, against human colon carcinoma as a drug-carrier to treat colorectal cancer. In the present study, we found that MAb A7 also reacted immunohistochemically with 73% of human pancreatic carcinoma cell lines, with the A7 antigen mainly being detected on the cell surface. However, the A7 antigen was found in only 9% of the spent media of these human pancreatic carcinoma cell lines by ELISA. On the other hand, the positive incidence of CA19-9, POA, ferritin, CEA, DU-PAN-2 and SLX in those spent media was 100%, 64%, 64%, 55%, 55% and 36%, respectively. These results suggest that the A7 antigen may only rarely be shed into the sera of pancreatic cancer patients, in which case MAb A7 could be a suitable drug-carrier in targeting chemotherapy for pancreatic cancer patients.

Antibodies, Monoclonal↗
PubMed1992

The features of glomerulitis in the acute stage of panarteritis nodosa. Developmental process of glomerulitis and correlation between glomerular and vascular lesions.

In order to determine the morphological characteristics of certain vascular and glomerular lesions and the correlation between them, we attempted three-dimensional observation using serial sections of an autopsy kidney, from a patient with panarteritis nodosa in the acute phase. Fibrinoid necrotizing vasculitis spread from arcuate arteries to arterioles in a segmental, eccentric pattern, especially occurring at bifurcations. Segmental arteriolitis often originated in extraglomerular capsular arteriole and spread into the intraglomerular capsular arteriole and glomerular capillaries, directly leading to necrotizing glomerulitis. Some of the glomerulitis connected directly with extracapsular arteriolitis was segmental and eccentric in distribution. Most of the glomerulitis had a tendency to originate in the hilar arteriole, which was near bifurcations between the arteriole and glomerular capillaries. Segmental glomerulitis was found to consist of four elements: glomerular tuft necrosis with fibrin exudation, crescents, rupture or dissolution of Bowman's capsule, and pericapsulitis. It is suggested that the segmental inflammatory attacks, repeated more than twice, give rise to widespread and almost global necrotizing glomerulitis.

Acute Disease↗
PubMed1992

Regional cerebral blood flow in patients with schizophrenia. A preliminary report.

Regional cerebral blood flow was evaluated using Tc99m-HMPAO SPECT in 10 medicated patients with schizophrenia and 9 healthy volunteers. There were no prefrontal regions in the patient group with lower regional indices than in the control group. However, in the left hippocampal region, relative blood flow was significantly increased in the patient group compared with the control group. Furthermore, there was a relative increase in blood flow in the left basal ganglia of the patient group. A negative correlation coefficient was calculated between the relative blood flow in the left middle prefrontal cortex and the severity of the blunted affect, as well as between the relative blood flow in the left basal ganglia and the severity of the anhedonia-asociality. These findings indicate that prefrontal hypoactivity is not invariably present in all schizophrenics and that left basal ganglial hyperactivity may be associated with the effects of antipsychotic treatment and clinical improvement. Moreover, the left hippocampal hyperactivity may correspond to left limbic dysfunction in schizophrenia.

Adult↗
PubMed1992

Differential regulation of IgA production by TGF-beta and IL-5: TGF-beta induces surface IgA-positive cells bearing IL-5 receptor, whereas IL-5 promotes their survival and maturation into IgA-secreting cells.

Transforming growth factor beta (TGF-beta) and IL-5 have been shown to augment IgA production by LPS-stimulated murine B cells. We investigated the effect of TGF-beta on the expression of surface Ig-isotype and IL-5 receptor on LPS-stimulated B cells. TGF-beta increased the proportion of both surface IgA-positive (sIgA+) B cells and sIgG2b+ B cells and enhanced IgA and IgG2b production by LPS-stimulated B cells. TGF-beta synergized with IL-5 only for IgA production of the seven Ig-isotypes and in combination with IL-5 caused a significant increase in the proportion of sIgA+ B cells up to 17.4%. In contrast, IL-5 decreased the proportion of sIgG2b+ B cells and sIgG3+ B cells and inhibited the production of IgG2b and IgG3 by LPS-stimulated B cells. About 50% of sIgA+ cells induced by TGF-beta expressed IL-5 receptor. They secreted peak levels of IgA and seemed to maintain long viability in the presence of IL-5; whereas TGF-beta had the opposite effects on sIgA+ B cells and down-regulated the IL-5 receptor expression. These results indicate that TGF-beta increases the number of sIgA(+)- and IL-5 receptor-positive B cells which respond to IL-5 giving rise to IgA-secreting cells and also support the notions that TGF-beta preferentially induces switching to sIgA+ B cells and IL-5 induces the maturation of postswitch sIgA+ B cells into IgA-secreting cells in a stepwise fashion.

Animals↗
PubMed1992

Distribution of epidermal growth factor (EGF) receptors in rabbit corneal epithelial cells, keratocytes and endothelial cells, and the changes induced by transforming growth factor-beta 1.

Three kinds of rabbit corneal cells (epithelial cells, keratocytes and endothelial cells) were cultured, and the growth promoting effects of epidermal growth factor (EGF) were examined in these cells. It was found that the sensitivity of the epithelial cells to EGF was the highest, that of the endothelial cells was a little lower, and that of the keratocytes was the lowest. Transforming growth factor-beta 1 (TGF-beta 1) did not influence growth of the three kinds of corneal cells. It was found that TGF-beta 1 enhanced the growth promoting effect of EGF in the keratocytes, but not in the epithelial and endothelial cells. EGF receptors in the corneal cells were labelled with [125I]EGF and analysed by Scatchard plot. In the epithelial and endothelial cells, both high and low affinity receptors were found, while the keratocytes had only low affinity receptor. In the epithelial cells, the number and the association constant of the high affinity receptors were, respectively, 2.79 x 10(4) per cell and 0.034 nM, and those of the low affinity receptors were, respectively, 13.4 x 10(4) per cell and 0.700 nM. In the endothelial cells, the number and the association constant of the high affinity receptors were 1.27 x 10(4) per cell and 0.086 nM, respectively, and those of the low affinity receptors were 8.91 x 10(4) per cell and 1.536 nM. In the keratocytes, the number of receptors and the association constant were 9.49 x 10(4) per cell and 1.535 nM, respectively. The corneal cells were treated with TGF-beta 1 for 24 hr and its influence on EGF receptors was examined. The results showed that TGF-beta 1 induced the high affinity receptors in the keratocytes, although TGF-beta 1 did not influence EGF receptors in the epithelial and endothelial cells. The number of high affinity receptors in keratocytes treated with TGF-beta 1 was 1.02 x 10(4) per cell and the association constant was 0.171 nM (this was approximately tenfold higher than that of the receptor of keratocytes not treated with TGF-beta 1).

Animals↗
PubMed1992

Pathology of the cerebellar dentate and interpositus nuclei in Joseph disease: a morphometric investigation.

Cerebellar dentate and interpositus nuclei pathology was studied morphometrically in 3 patients with Joseph disease compared to 3 control subjects. Size of neurons, number of small neurons (cell body area: 50-199 microns 2) and large neurons (cell body area: 200 microns 2 or greater) at the rostral, medial and caudal levels, neuronal cell density, total volume of the gray bands, and total neuronal cell number were evaluated in the dentate, emboliform, and globose nuclei, using an image analyzer, after making horizontal serial 20-microns thick sections of a unilateral cerebellar hemisphere embedded in celloidin. The number of large neurons in Joseph disease was around 20% of that in the controls at each level in the individual nucleus (P less than 0.05 or P less than 0.01). In contrast, the number of small neurons was significantly reduced only at the caudal level of the dentate nucleus (P less than 0.05). The neuronal cell density was decreased within the nuclei. The total volume of the gray bands was reduced to about 70% within the nuclei (P less than 0.05 or P less than 0.01). The total number of neurons was decreased to about a third, a half, and a third within the dentate (P less than 0.001), emboliform (P less than 0.01), and globose nuclei (P less than 0.001), respectively. The principal pathologic change of the dentate and interpositus nuclei in Joseph disease was severe loss of neurons, with significant loss of the large neurons, indicating that Joseph disease is a type of cerebellar efferent system disorder.

Adult↗
PubMed1992

Facilitative effect of carbamazepine on previously induced hippocampal long-term potentiation.

The effects of carbamazepine (CBZ) on previously induced hippocampal long-term potentiation (LTP) were examined. Acute experiments were performed on 33 adult, male rabbits. Field potentials in the dentate gyrus were elicited by single shocks to the perforant path, and LTP was induced by tetanic stimulation to the pathway without induction of seizure discharge. At a CBZ serum level of about 5 micrograms/ml (value +/- SD = 5.40 +/- 1.28 micrograms/ml), the previously induced LTP in population spikes (PSs) and population excitatory postsynaptic potentials (EPSPs) was facilitated. At a CBZ serum level of about 15 micrograms/ml (value +/- SD = 14.28 +/- 1.29 micrograms/ml), the LTP in PS alone was decreased. The effects of carbamazepine on synaptic inhibition were examined by the paired-pulse test. The inhibition was enhanced with induction of LTP. After administration of CBZ, at a CBZ serum level of about 5 micrograms/ml the inhibition was further enhanced, while it was attenuated at a CBZ serum level of about 15 micrograms/ml. These results suggest that CBZ has a facilitative effect on previously induced LTP.

Animals↗
PubMed1992

Anticonvulsant effect of allopurinol on hippocampal-kindled seizures.

This study assessed the anticonvulsant effect of allopurinol (5 and 50 mg/kg, IP) on seizures kindled from the feline hippocampus. Allopurinol at a higher dose significantly reduced the behavioral seizures stage, but not afterdischarge duration, without producing any behavioral toxicity. The present results lend experimental support to the contention that allopurinol possesses anticonvulsant efficacy in the treatment of human epilepsy.

Allopurinol↗