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Biomedical subjects

H Kikuchi

Publications and source records attributed to H Kikuchi.

At least 307 records · Page 17Linked to original sources
PubMed1996

Expression of somatostatin receptor (SSTR) subtypes in pituitary adenomas: quantitative analysis of SSTR2 mRNA by reverse transcription-polymerase chain reaction.

The expression of somatostatin receptor (SSTR) subtypes and relative abundance of SSTR2 mRNA were examined in 18 pituitary adenomas using the reverse transcription-polymerase chain reaction (RT-PCR) method. SSTR1 and SSTR2 were expressed in all pituitary adenomas examined. Six of 9 somatotroph adenomas, 1 of 4 lactotroph adenomas and 1 of 2 thyrotroph adenomas also expressed SSTR5. SSTR3 and SSTR4 mRNAs were detected in 1 and 2 cases of somatotroph adenoma, respectively. SSTR2 mRNA expression was quantified by comparison with the PCR cycle-dependent amplification of beta-actin or cyclophilin. The relative abundance of SSTR2 mRNA varied greatly among adenomas with more than a 1000-fold difference. SSTR2 mRNAs in lactotroph adenomas were less abundant (P < 0.01) than those in somatotroph adenomas. No significant correlation was found between the relative abundance of SSTR2 mRNA levels and GH sensitivity to octreotide administration. However, one of the thyrotroph adenomas exhibited marked shrinkage in tumor size after octreotide therapy, in which SSTR2 mRNA was the most abundant among the adenomas examined. GH sensitivity to octreotide was not significantly different between SSTR5 mRNA positive and negative adenomas. In conclusion, SSTR2 mRNA levels varied greatly among pituitary adenomas but were not correlated with GH sensitivity to octreotide. Further investigations of functional SSTR subtype proteins and of postreceptor signal transductions are required to clarify the molecular mechanisms of octreotide action.

Adenoma↗
PubMed1995

Activation of heat shock factor 1 in rat brain during cerebral ischemia or after heat shock.

Recently, many studies have demonstrated the induction of stress proteins in the mammalian nervous system under various pathological conditions. These altered genetic programs may function to protect individual cells against stressful conditions. However, little is known about the molecular mechanisms regulating these stress responses in animals. We report here the activation of a heat shock factor (HSF) in the rat brain during cerebral ischemia or after heat shock. Gel mobility shift assays revealed an increase in DNA binding activity to the heat shock element (HSE) during the early phases of ischemia. Supershift experiments using specific antisera against HSF1 and HSF2 showed that the ischemia-induced HSE-binding activity was mainly due to HSF1. In the heat-shocked brain, HSF1 was also activated, and the HSE-binding activity was higher in the cerebellum than in the cerebral cortex or hippocampus; Western blot analysis also showed that HSF1 was more abundant in the cerebellum than in the other two brain regions. Our results indicate that heat shock gene transcription is regulated by the activation of HSF1 in both cerebral ischemia and heat shock, and that different brain regions display differential sensitivities in their stress response. The cellular signals for heat shock gene transcription under in vivo pathological conditions will also be discussed.

Animals↗
PubMed1995

Lactacystin, a specific inhibitor of the proteasome, induces apoptosis in human monoblast U937 cells.

Lactacystin, originally isolated from a microbe as an inducer of neuritogenesis, targets the catalytic beta-subunit of the proteasome, and arrests the cell cycle. Here we report for the first time that lactacystin induces apoptotic cell death in human monoblastic U937 cells. When U937 cells were cultured with lactacystin, their nuclei were shrunken, a morphological change typical of apoptosis, and cell viability was decreased. Electrophoretic analysis revealed that chromosomal DNAs from lactacystin-treated cells were cleaved in an internucleosomal ladder-like pattern, indicating that cell death occurs through an apoptotic process, which was also confirmed by DNA fragmentation analysis using flow cytometry. These findings suggest that inhibition of the proteasome during proliferation results in apoptotic cell death, and that the proteasome is a key enzyme in the course of the cell cycle that destines the cell to proliferate, differentiate or die.

Acetylcysteine↗
PubMed1995

Antibodies specific for proteolyzed forms of protein kinase C alpha.

The activation of protein kinase C (PKC) is irreversibly regulated by limited proteolysis catalyzed by a calcium-activated neutral cysteine protease, calpain. Calpain cleaves PKC alpha at specific sites in the hinge region between the catalytic and the regulatory domains of this kinase. Here we show a novel method for production of antibodies that bind specifically to the catalytic fragment of PKC alpha but not to the unproteolyzed protein. To detect proteolyzed PKC alpha 'cleavage site-directed antibodies,' which recognize amino-terminal regions in the nascent catalytic fragments and do not cross-react with the unproteolyzed enzymes, were raised using synthetic peptides corresponding to the amino-terminal sequences. The synthetic peptides used in this study were the sequences of human PKC alpha at the cleavage sites by m- and mu-types of calpains (LGPAGNKV and VISPSEDRKQPSNNLDRVKLT, respectively) and they are designated as CF alpha 2, CF alpha 4, in this order. Each synthetic peptide was injected into rabbit after conjugation with a carrier protein. The antibodies thus obtained (anti-CF alpha 2 or -CF alpha 4) specifically reacted with either the 46- or 45-kDa catalytic fragment of PKC alpha, respectively, whereas they did not cross-react with other fragments. Furthermore, the antibodies did not bind to the unproteolyzed enzyme nor fragments of PKC alpha obtained by treatment with other proteinases unless the fragment carried the same amino-terminal sequence. When human platelets were treated with calcium ionophore, the catalytic fragments of PKC alpha (45- and 46-kDa) were detected in the cytosol by immunoblotting with the antibodies. However, these antibodies did not bind unproteolyzed 80-kDa PKC alpha, although this form was dominant in the cytosol of the calcium ionophore-treated human platelets. In addition, the 45-kDa catalytic fragment of PKC alpha was detected in an apoptotic human fibroblast TIG-3 cells cultured in serum-free medium. Our method is applicable for analysis of proteolysis in various cellular states.

Amino Acid Sequence↗
PubMed1995

Ultrastructural localization and translocation of nitric oxide synthase in the endothelium of the human cerebral artery.

An electron microscopic immunocytochemical study was undertaken to clarify ultrastructural localization and translocation of nitric oxide synthase (NOS) in endothelial cells (EC) of the human cerebral and superficial temporal arteries (STA) employing antibody against endothelial NOS (EC-NOS). NOS immunoreactivity was found in all EC examined, in association with the plasma membrane and cytoplasmic organelles such as endoplasmic reticulum, Weibel-Palade body and subplasmalemmal vesicles, and in the cytoplasm devoid of organelles and extracellular regions, irrespective of arteries. The immunoreactivity in subplasmalemmal vesicles was, however, demonstrated only in human cerebral arteries. In the human STA exposed to bradykinin which induces EC-NOS phosphorylation, the gold particles significantly increased in the cytosol and decreased in the areas associated with cytoplasmic organelles; however, the number of particles did not change significantly in the plasma membrane. The results implicate that NOS may be translocated from the area associated with cytoplasmic organelles to cytosol following EC exposure to bradykinin.

Adult↗
PubMed1995

Identification of cellular protein that can interact specifically with the basic helix-loop-helix domain of the aromatic hydrocarbon receptor.

The Ah receptor is a basic helix-loop-helix (bHLH)-PAS protein and functions as a ligand-activated DNA binding protein directly interacting with target genes by binding to xenobiotic responsive elements. We have sought to identify possible cellular proteins that can interact with the Ah receptor. The bHLH domain of the Ah receptor was fused to glutathione-S-transferase (GST), and the resulting fusion protein was used as a probe to help us to identify receptor associated protein(s). At least one such protein, 45kDa (p45), was detected in mouse liver extracts, but it does not bind to the bHLH domain of the Ah receptor nuclear translocator, nor to the transactivation domain of Ah receptor or GST alone.

Animals↗
PubMed1995

Identification of a 120-kDa protein associated with aromatic hydrocarbon receptor nuclear translocator.

The aromatic hydrocarbon receptor nuclear translocator (ARNT) is a basic helix-loop-helix-PAS protein which forms a heterodimer with aromatic hydrocarbon receptor (AHR), this heterodimer mediating the signal transduction in response to the various xenobiotics such as 2,3,7,8-tetrachlorodibenzo-p-dioxin and directly interacting with target genes by binding to xenobiotic responsive elements. An anti-ARNT antibody was raised in rabbits against the bacterially expressed ARNT of amino acids 21-328 from the N-terminal. Using this antibody, besides ARNT itself, we detected at least one protein, 120 kDa, in the immunoprecipitate of anti-ARNT antibodies in HepG2 cells as well as in Hepa-1 cells. However, this protein is not present in the immunoprecipitate of the anti-AHR antisera nor in that of the preimmune sera of the rabbits used for the immunization.

Animals↗
PubMed1995

Effect of cyclic AMP on urokinase-type plasminogen activator receptor and fibrinolytic factors in a human osteoblast-like cell line.

We investigated the effect of cyclic AMP (cAMP) on the pericellular fibrinolytic system in NY cells. Dibutyryl cAMP (dbcAMP) or forskolin increased the level of urokinase-type plasminogen activator (u-PA) mRNA and enhanced the secretion of u-PA antigen into the conditioned medium. These agents also increased u-PA antigen on the cell surface. PA inhibitor-1 (PAI-1) antigen was inhibited by dbcAMP or forskolin. Butyrate had no effect on the production and secretion of u-PA and PAI-1. A binding assay of 125I-DFP-u-PA to NY cells revealed a single class of binding sites with a Kd of 3.85 nM and Bmax of 0.89.10(5) binding sites/cell. The Bmax was increased by dbcAMP (1 mM or 10 mM), forskolin (2 microM or 20 microM) of 1.0-, 1.4-, 1.2- and 1.8-fold, respectively. However, the Kd value was not changed. Furthermore, the level of mRNA for the u-PA receptor (u-PAR) was increased by these agents 1.2-, 1.7-, 1.8- and 2.5-fold, respectively. However, butyrate did not alter either the Bmax or the u-PAR mRNA level. These results indicated that the pericellular fibrinolytic activity induced by u-PA/u-PAR is modulated by cAMP in osteoblast-like cells.

Bucladesine↗
PubMed1995

A critical mutation in both WT1 alleles is not sufficient to cause Wilms' tumor.

The WT1 gene is a tumor suppressor gene for Wilms' tumor (WT). Inactivation of both alleles has been proposed as the cause of WT. We encountered a patient with Denys-Drash syndrome associated with WT whose WT1 gene had a homozygous point mutation not only in WT but also in renal tissue adjacent to the WT and in the germline. These findings indicate that factor(s) other than the loss of WT1 are required for WT to develop.

Alleles↗
PubMed1995

Localization of trkB and low-affinity nerve growth factor receptor mRNA in the developing rat retina.

The localization of trkB and low-affinity nerve growth factor receptor (LNGFR) mRNAs in the developing rat retina was examined by in situ hybridization. TrkB mRNA was expressed in the ganglion cell layer (GCL), in the inner border of the neuroblastic layer (NBL), and the inner border of the inner nuclear layer (INL). LNGFR mRNA was expressed in the GCL, in almost full thickness of the NBL, and in the intermediate part of the INL. Although both trkB mRNA and LNGFR mRNA were expressed in the GCL, the expression pattern was different between these mRNAs; trkB mRNA was expressed in almost all cells in the GCL uniformly and the expression of LNGFR mRNA varied greatly from cell to cell. In addition, the expression of both mRNAs, especially LNGFR mRNA seemed to be down-regulated at P7, when programmed cell death of the RGCs was prominent. These observations indicate that LNGFR may modulate the function of trkB and that trkB and LNGFR play important roles in the development and maintenance of the RGCs.

Animals↗
PubMed1995

Pharmaceutical and biological properties of doxorubicin encapsulated in liposomes (L-ADM): the effect of repeated administration on the systemic phagocytic activity and pharmacokinetics.

We investigated the biodistribution and antitumour activity of doxorubicin (ADM) encapsulated in liposomes (L-ADM) after two administrations in tumour bearing mice. The effect of the first administration on phagocytic activity was also examined. The biodistribution of L-ADM after the second dosing at an interval of 4d was remarkably different from that after the first. The concentration of ADM in plasma and tumour after the second injection was higher, but that in the liver was lower than after the first administration. This decrease in distribution to the liver is thought to have contributed to the difference in the biodistribution characteristics of L-ADM. With regard to antitumour effect, the activity was similar between L-ADM and a solution of ADM (F-ADM). To investigate the effect of the first administration of L-ADM on biodistribution, systemic phagocytic activity was measured after the injection of F-ADM, L-ADM, or 'empty' liposomes not containing ADM. F-ADM and L-ADM (7.5 mg ADM/kg body weight) reduced phagocytic activity to approximately 50% and 30% of control, respectively. This finding suggests that entrapment of ADM in liposomes enhances both the distribution of the drug to the reticuloendothelial system (RES) and its suppressive effect on RES activity. These results indicate that the decrease in RES activity by L-ADM must be considered in estimation of the pharmacokinetics, antitumour activity, and toxicity of L-ADM in clinical use when given by repeat administration or used in combination with other antitumour agents.

Animals↗
PubMed1995

Steatorrhea in Japanese patients with chronic pancreatitis.

Fecal fat excretion, fecal mass, fecal fat concentration, and the coefficient of fat absorption were evaluated in 31 normal Japanese subjects with a mean fat consumption of 61.8 g and compared with the values in 43 Japanese patients with chronic pancreatitis (CP) with a fat consumption of 40.2 g. Fecal fatty acids were analyzed by the gas chromatographic method. Fecal fat excretion by normal individuals was 1.7 +/- 1.0 (Mean +/- SD) g/day (range, 0.4-4.9 g/day). Steatorrhea was therefore defined as fecal fat excretion that exceeded 5.0 g/day. The patients with CP were divided into three groups: non-steatorrhea (fecal fat < 5.0 g/day), chemical steatorrhea (fecal fat > or = 5 g/day and no appearance of fatty stool), and manifest steatorrhea (evaluated from the appearance of fatty stool). In addition, we investigated the correlation between fecal fat excretion and pancreatic exocrine function, obtained by the pancreozymin-secretin (or secretin) test in 24 controls and 30 CP patients. Fecal fat excretion by CP patients was 9.1 +/- 8.8 g/day, which was significantly higher (P < 0.01) than that of controls. There were 28 (65%) CP patients with steatorrhea. Of these, 15 (35%) showed chemical steatorrhea and 13 (30%) manifest steatorrhea. In CP patients, the fecal mass (250.5 +/- 133.6 g vs control, 125.6 +/- 52.5 g), fecal fat concentration (3.40 +/- 2.16 g% vs control, 1.48 +/- 0.89 g%), and coefficient of fat absorption (77.3 +/- 20.2% vs control, 97.2 +/- 1.7%) all showed significant differences from the controls.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1995

Simulation study on bypass and therapeutic occlusion in the posterior circulation.

A hydraulic vascular model of the vertebrobasilar artery with an autoregulatory mechanism was constructed. The haemodynamic effect of superficial temporal artery (STA)-posterior cerebral artery (PCA) bypass was investigated in cases of bilateral vertebral artery (VA) occlusion and basilar artery (BA) occlusion. Assuming therapeutic BA occlusion for basilar bifurcation aneurysms, the flow volume through the P1 segment of the PCA was determined in relation to diameters of the posterior communicating artery (PCom). The bypass increases both flow volume and intraluminal pressure in the presence range below 60 mm Hg, while it increases only pressure in the autoregulatory range above 60 mm Hg. Its haemodynamic effect is more marked in BA occlusion than in VA occlusion. The averaged values of the increase in flow volume are 29.0 +/- 4.3% (mean +/- SD) and 16.5 + 1.0%, respectively. The total flow volume increase of the vertebrobasilar system is usually lower than the flow volume measured at the bypassed STA. The difference between the two is equal to the simultaneous decrease in flow volume through the PComs. Flow volume through the P1 segment can be expressed as a function of the PComs diameter ratio squared. A hydraulic simulation study will be useful for speculating on the haemodynamic effects of these operative procedures.

Basilar Artery↗