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H Yamaguchi

Publications and source records attributed to H Yamaguchi.

At least 847 records · Page 47Linked to original sources
PubMed1993

Effects of seven months' exposure to a static 0.2 T magnetic field on growth and glycolytic activity of human gingival fibroblasts.

Human gingival fibroblasts in confluent cultures were continuously exposed to a static 0.2 T magnetic field for 6 or 8 months. Culture flasks were not changed during the exposure, but culture medium was renewed. After dilution and mixing of the cultures surviving intact, field-exposed and sham-exposed cultures received further field- or sham-exposure on Sm-Co blocks. Rate of cell proliferation, histogram of the nuclear DNA content, rates of lactate production and glucose consumption and the ATP content were determined and cell morphology was investigated by both light- and electron-microscopy. Results show no marked differences between exposed and control cells.

Adenosine Triphosphate↗
PubMed1993

Dextran-conjugated anti-IgD antibodies inhibit T cell-mediated IgE production but augment the synthesis of IgM and IgG.

We previously demonstrated that anti-IgD antibodies conjugated to dextran (alpha delta-dex) were a potent co-stimulus for Ig secretion by resting murine B cells in the presence of cytokines. However, although alpha delta-dex stimulated the secretion of most Ig isotypes it selectively failed to costimulate IgE production even in the presence of high concentrations of IL-4. Earlier reports indicated that unconjugated anti-IgM, which was not an effective costimulus for Ig secretion, in fact inhibited Ig production induced by LPS. We determined the effect of alpha delta-dex, at concentrations that costimulated cytokine-induced Ig secretion, on Ig production by LPS- or T cell-activated B cells, and whether IgE production was affected in a selective manner. We observed that alpha delta-dex inhibited Ig isotype production (IgE > IgG > IgM) by LPS-activated B cells, while further stimulating their proliferation. This effect of alpha delta-dex was mediated directly at the level of the B cell and was accompanied by a comparable inhibition in Ig class switching, as assessed by flow cytometric analysis of membrane Ig isotype-positive cells. The inhibitory effects of alpha delta-dex on LPS-induced Ig secretion and class switching occurred at 1000-fold lower concentrations of anti-IgD than that reported necessary for inhibition by unconjugated anti-IgM. Whereas IL-4 + IL-5 costimulated Ig isotype production by alpha delta-dex-activated cells, the further addition of LPS led to a marked ablation of the Ig secretory response indicating the cross-inhibitory effects of these two modes of B cell activation. By contrast, alpha delta-dex augmented IgM and IgG1 secretion by resting B cells stimulated with either an anti-CD3-activated CD4+ Th2 clone or with activated T cell membranes in combination with IL-4 + IL-5. However, alpha delta-dex potently inhibited T cell-mediated IgE secretion. These findings underscore the existence of, and demonstrate a number of novel interrelationships between, three distinct pathways of B cell differentiation induced by different modes of activation. Further, the observation that pg/ml quantities of alpha delta-dex selectively inhibits T cell-induced IgE production in vitro suggests a novel strategy to down-regulate this Ig isotype in vivo.

Adjuvants, Immunologic↗
PubMed1993

Three-dimensional structure of the glutathione synthetase from Escherichia coli B at 2.0 A resolution.

Glutathione synthetase (gamma-L-glutamyl-L-cysteine: glycine ligase (ADP-forming) EC 6.3.2.3: GSHase) catalyzes the synthesis of glutathione from gamma-L-glutamyl-L-cysteine and Gly in the presence of ATP. The enzyme from Escherichia coli is a tetramer with four identical subunits of 316 amino acid residues. The crystal structure of the enzyme has been determined by isomorphous replacement and refined to a 2.0 A resolution. Two regions, Gly164 to Gly167 and Ile226 to Arg241, are invisible on the electron density map. The refined model of the subunit includes 296 amino acid residues and 107 solvent molecules. The crystallographic R-factor is 18.6% for 17.914 reflections with F > 3 sigma between 6.0 A and 2.0 A. The structure consists of three domains: the N-terminal, central, and C-terminal domains. In the tetrameric molecule, two subunits that are in close contact form a tight dimer, two tight dimers forming a tetramer with two solvent regions. The ATP molecule is located in the cleft between the central and C-terminal domains. The ATP binding site is surrounded by two sets of the structural motif that belong to those respective domains. Each motif consists of an anti-parallel beta-sheet and a glycine-rich loop.

Adenosine Triphosphate↗
PubMed1993

Diagnostic significance of skin immunolabelling with antibody against native cerebral amyloid in Alzheimer's disease.

Skin taken from patients with Alzheimer's disease (AD) and control patient groups were immunolabelled using antisera against either purified native cerebral beta protein or synthetic beta peptide. Native amyloid antiserum frequently labelled vascular walls in AD skin but rarely in control skin. Semi-quantitative analysis of the positive vessels showed a significant difference between the two groups. Sweat glands and dermal nerves were labelled in both groups. However, synthetic beta peptide antiserum showed no significant difference. Vascular wall labelling in skin with native amyloid antiserum is useful in the differential diagnosis of AD.

Aged↗
PubMed1993

Use of adenosine (5')polyphospho(5')pyridoxals to study the substrate-binding region of glutathione synthetase from Escherichia coli B.

Adenosine(5')polyphospho(5')pyridoxals (APn-PLs, n = 2, 3, 4) were examined for affinity labeling of glutathione synthetase (EC 6.3.2.3) from Escherichia coli B. When the enzyme was incubated with an APn-PL or pyridoxal phosphate in the presence of Mg2+ and then reduced with sodium borohydride, it was most rapidly inactivated by AP4-PL. AP4-PL had a high affinity to the enzyme. The dissociation constant of AP4-PL in the inactivation process was 23 microM. The enzyme was almost completely protected from inactivation by addition of either ATP or gamma-glutamylcysteine. Complete inactivation corresponded to the incorporation of 1 mol of AP4-PL/mol of subunit of the tetrameric enzyme. Proteolytic digestion and sequence analysis of the AP4-PL-labeled enzyme revealed that only Lys-18 was modified. In contrast, the less efficient AP3-PL was found attached to Lys-17, Lys-18, Lys-144, and Lys-148. In the three-dimensional structure of the enzyme, Lys-18 is located close to the putative gamma-glutamylcysteine-binding site, but Lys-17, Lys-144, and Lys-148 are in the mouth of the inner-solvent region, at the bottom of which is the active-site cleft. Furthermore, difference Fourier analysis with the AP4-PL-soaked crystal of the enzyme showed that the adenosine moiety of the bound AP4-PL was in the crevice, which is the ATP-binding site of the enzyme. These results demonstrate the bivalent binding of AP4-PL lying across the gamma-glutamylcysteine- and ATP-binding sites.

Adenine Nucleotides↗
PubMed1993

Coronary neovascularity: a possible sign of new and growing mural thrombus.

This is a case report of a coronary artery fistula through a mural thrombus on a left ventricular aneurysm into the left ventricle. Serial coronary arteriography disclosed a vessel exhibiting a "smokelike" appearance originating at the anterior descending artery. This abnormal finding faded away over a period of 10 years with a decrease in size of the mural thrombus. This finding strongly suggests that the abnormal vessel represents an acquired neovascularity related to a newly developed thrombus.

Coronary Angiography↗
PubMed1993

Arrest of cell cycle progression of HeLa cells in the early G1 phase in K(+)-depleted conditions and its recovery upon addition of insulin and LDL.

Cell cycle progression of synchronized HeLa cells was studied by measuring labeling of the nuclei with [3H]thymidine. The progression was arrested in a chemically defined medium in which K+ was replaced by Rb+ (Rb-CDM) but was restored upon addition of insulin and/or low density lipoprotein (LDL). Cells started DNA synthesis 12 hr after addition of insulin and/or LDL, regardless of the time of arrest, suggesting their arrest early in the G1 phase. After incubation of cells in Rb-CDM containing insulin or LDL singly for 3, 6, or 9 hr, replacement of the medium by that without an addition resulted in marked delay in entry of cells into the S phase, but in its replacement by medium containing both agents, the delay was insignificant. Synthesis of bulk protein, estimated as increase in the cell volume, was not strongly inhibited. From these results we conclude that cell cycle progression of HeLa cells in K(+)-depleted CDM is arrested early in the G1 phase and that the arrest is due to lack of some protein(s) required for entry into the S phase that is synthesized in the early G1 phase.

Cell Cycle↗
PubMed1993

Down-regulation of the surface expression of class I MHC antigens by human cytomegalovirus.

Class I major histocompatibility complex (MHC) antigens of higher eukaryotes play a crucial role in the recognition of human cytomegalovirus (HCMV)-infected cells by cytotoxic T lymphocytes. In the present study, we have demonstrated that HCMV infection resulted in a marked reduction in the surface expression of class I MHC antigens on human embryonic lung fibroblasts (HEL). Even when HCMV-infected HEL were cultured in the presence of 9-(1,3-dihydroxy-2-propoxymethyl)-guanine (DHPG), the reduction was observed to the same extent, indicating that HCMV DNA synthesis was not required for this phenomenon. However, immunoprecipitation studies have shown that there was no significant reduction in the synthesis of either the heavy chain or the light chain of class I MHC antigens after HCMV infection. In addition, Western blotting studies have revealed that the total amount of the antigens was almost unaltered after HCMV infection. These results suggest that the reduction in the cell surface expression of class I MHC antigens is due to some defect occurring post-translationally, most likely at the level of the correct complex formation and/or the intracellular transport of class I MHC antigens.

Blotting, Western↗
PubMed1993

Kinetic study on the effects of intracellular K+ and Na+ on Na+, K+, Cl- cotransport of HeLa cells by Rb+ influx determination.

The effects of intracellular K+ and Na+ (K+c, Na+c) on the Na+, K+, Cl- cotransport pathway of HeLa cells were studied by measuring ouabain-insensitive, furosemide-sensitive Rb+ influx (JRb) at various intracellular concentrations of K+ and Na+ ([K+]c, [Na+]c). When [K+]c was increased and [Na+]c was decreased, keeping the sums of their concentrations almost constant, JRb as a function of the extracellular Rb+ or Na+ concentration ([Rb+]e, [Na+]e) was stimulated. However, the apparent K0.5 for Rb+e or Na+e remained unchanged and the ratio of the apparent K0.5 for K+c and the apparent Ki for Na+c was larger than 1. When JRb was increased by hypertonicity by addition of 200 mM mannitol, the apparent maximum JRb increased without change in the apparent K0.5 for Rb+e. These results show that K+c stimulates and Na+c inhibits JRb, without change in the affinities of the pathway for Rb+e and Na+e. The affinity for K+c is slightly lower than that for Na+c. Hypertonicity enhances JRb without any change in the affinity for Rb+e. We derived a kinetic equation for JRb with respect to K+c and Na+c and proposed a general and a special model of the pathway. The special model suggests that, in HeLa cells, JRb takes place when Rb+e binds to the external K+ binding site of the pathway after the binding of K+c to the internal regulatory site.

Biological Transport↗
PubMed1993

Changes in carotid blood flow and electrocardiogram in humans during and after walking on a treadmill.

Blood flow velocity in the common carotid artery and the electrocardiogram were measured simultaneously by telemetry in seven male subjects during 20-min walking on a treadmill at an exercise intensity corresponding to a mean oxygen uptake of 26.0 (SD 2.9) ml.kg-1.min-1. The mean cardiac cycle was shortened from 0.814 (SD 0.103) s to 0.452 (SD 0.054) s during this exercise. Of this shortening, 73% was due to shortening of the diastolic period and 27% to shortening of the systolic period. In the relatively small shortening of the mean systolic period [from 0.377 (SD 0.043) s to 0.268 (SD 0.029) s], the isovolumetric contraction time was shortened by 56%. During exercise, the heart rate (fc) increased by 79.4% [from 74.3 (SD 9.3) beats.min-1 to 133.3 (SD 14.8) beats.min-1], and the peak blood velocity (S1) in the common carotid artery increased by 56.1% [from 0.82 (SD 0.10) m.s-1 to 1.28 (SD 0.11) m.s-1]. After exercise, the S1 decreased rapidly to the resting level. The fc decreased more slowly, still being higher than the initial resting level 5 min after exercise. The diastolic velocity wave and the end-diastolic foot decreased during exercise. The blood flow rate in the carotid artery increased transiently by 13.5% at the beginning of exercise [from 5.62 (SD 0.63) ml.s-1 to 6.38 (SD 0.85) ml.s-1] and by 26.5% at the end of the exercise period [from 5.62 (SD 0.63) ml.s-1 to 7.11 (SD 1.34) ml.s-1].(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

Growth of human tumor xenografts in nude mice and mice with severe combined immunodeficiency (SCID).

Twenty-three fresh tumor specimens obtained at surgery and 5 serially transferable human tumor xenografts were implanted subcutaneously into nude mice and mice with severe combined immunodeficiency (SCID) to compare the take rates of the fresh surgical specimens and the growth rates of the transferable strains. The overall take rates were 65% for the SCID mice and 60% for the nude mice, without any significant difference, although colon carcinoma seemed to have higher acceptance in the SCID mice with a take rate of 6/8. All the serially transferable strains were successfully accepted in the SCID mice, their growth rates being essentially identical to those in the nude mice. These results indicate that the SCID mouse can be used as a human tumor xenograft-mouse system as well as the nude mouse.

Adenocarcinoma, Mucinous↗
PubMed1993

The modulation by L-leucovorin of 5-fluorouracil antitumor activity on human colon carcinoma cells in vitro and in vivo.

We investigated the modulating effect of L-leucovorin (LV) on the antitumor effect of 5-fluorouracil (5-FU) against human colon carcinoma cells (C-1) in vitro and human colon carcinoma xenografts (Co-4) in nude mice. The modulating effect of LV on 5-FU reached an optimal concentration of 40-80 micrograms/ml in vitro which was detected by a colorimetric MTT assay. An optimal dose of 200 mg/kg was also observed in the nude mouse system. The modulating effect of LV increased according to the increment of thymidylate synthetase inhibition in vivo. Since the pharmacokinetic pattern of LV in the nude mice administered LV at 200 mg/kg was similar to that in patients treated with LV at a dose of 100 mg/m2, this clinical method of administration was thought to be adequate for modulating the antitumor activity of 5-FU against clinical colon carcinomas.

Adenocarcinoma↗
PubMed1993

Spike generating smooth muscle cells in mesenteric artery of rats.

Membrane electrical properties of smooth muscle cells at different loci in the vessel wall of rat small mesenteric arteries were studied using glass microelectrodes. Isometric force was measured simultaneously. Penetrations of smooth muscle cells on the adventitial side (outer cells) showed an average resting potential, -43.1 +/- 0.8 mV (n = 24). In outer cells, numerous depolarizing junctional potentials and, to a lesser degree, hyperpolarizing junctional potentials were observed. When current was injected, electrotonic potentials were recorded. Input resistance was 2.2 +/- 0.1 x 10(9) omega (n = 15), suggesting that the low resistance pathways commonly observed in smooth muscle tissue are absent among these cells. Transmural electrical stimulation of nerves elicited spikes and summation of junctional potentials, accompanied by force. TTX virtually abolished these effects of the transmural stimulation. In contrast, cells near the intima (inner cells) had an average resting potential of -65.8 +/- 0.9 mV (n = 37). No spontaneous electrical activity was observed; nor could electrotonic potentials be recorded. Thus, the smooth muscle cells from the outer layer of rat small resistance arteries differ from the inner cells in their lower membrane potentials, generation of spikes, higher input resistance and innervation. Results also suggest that the influence of nerves may be to facilitate opening of voltage-gated Ca2+ channels in innervated cells.

Action Potentials↗
PubMed1993

Changes in cardiac rhythm in man during underwater submersion and swimming studied by ECG telemetry.

A previously reported method for electrocardiographic (ECG) telemetry in water using frequency-modulated current was improved to obtain more stable ECGs. The ECGs of seven healthy men were monitored using the improved method during and after whole-body submersion or underwater swimming. Bradycardia and arrhythmias were observed during the submersion, and transient tachycardia was detected after the start of underwater swimming, followed by bradycardia with arrhythmias. Three different types of arrhythmias were observed: sinus arrhythmia (SA), supraventricular extrasystole (SE) and ventricular extrasystole (VE). SA and SE tended to develop during the latter half of the period of submersion or underwater swimming, and especially after the restart of breathing. VEs were detected in only one subject during submersion, whereas they occurred in most subjects during and after underwater swimming. Individual variations were found in development of arrhythmias, one subject showing no arrhythmia. Bradycardia, SA and SE could depend on vagal suppression in underwater conditions, and VE may be related to the effect of muscular movement on cardiac function in addition to vagal inhibition.

Adult↗
PubMed1993

Ultrastructural localization of amyloid beta/A4 protein precursor in the normal rat brain.

The ultrastructural localization of amyloid beta/A4 protein precursor (APP) was studied immunohistochemically in normal rat brains using antibodies against different portions of APP. In cerebral cortical neurons and Purkinje cells. APP reaction products were located in the cytoplasm and on cell surface membranes. Some Golgi apparatuses and rough endoplasmic reticulum also showed APP immunoreactivity on their membranes and some vesicles near the trans face of the Golgi apparatuses were stained. In the neuropil of the cerebral cortex and the cerebellar molecular layer, many cell processes, which surrounded synapses and were considered to be astrocytic, were APP-positive. Foot processes around capillaries and subpial astrocytic processes were also immuno-positive. At the ultrastructural level, APP-positive astrocytic processes were identified.

Amyloid beta-Peptides↗
PubMed1993

Differential expression of alpha 1-antichymotrypsin in the aged human brain.

The localization of alpha 1-antichymotrypsin (ACT) mRNA and ACT immunoreactivity (ACT-IR) were examined in 12 brains obtained at post-mortem from elderly patients, four of whom had Alzheimer's disease. A biotinylated oligonucleotide probe was used for in situ hybridization histochemistry and the relationship between the expression of both ACT mRNA and ACT-IR and the extent of beta protein or tau deposition were investigated. The extent of beta-plaques, tau-tangles, and ACT-IR were rated from (-) to (++). In brains without plaques and tangles, there were no detectable ACT mRNA signals in the gray matter, and those in the white matter were weak; in these brains, ACT-IR was generally weak. The brains with beta-plaques but no tangles showed weak ACT mRNA expression in astrocytes of both the gray and white matter; they also showed weak ACT-IR in the astrocytes. In the brains from patients with Alzheimer's disease with both plaques and tangles, ACT mRNA was expressed intensely in a majority of the astrocytes in the white and gray matter. Some senile plaques-associated astrocytes expressed ACT mRNA and ACT-IR was strong in the white matter astrocytes. ACT-IR and ACT mRNA expression in astrocytes was correlated with the extent of beta and tau depositions.

Aged↗
PubMed1993

Lumbar epidural anaesthesia prevented prostaglandin E1-induced diuretic effect in enflurane anaesthetized patients.

Prostaglandin E1 (PGE1) is used to induce deliberate hypotension during anaesthesia. The purpose of this study was to compare the PGE1-induced diuretic effect in anaesthetized patients with and without lumbar epidural anaesthesia. The changes in haemodynamic variables, urinary flow, one-hour creatinine clearance (Ccr), and fractional excretion of sodium (FENa) during injection of PGE1 or a vehicle were compared in 42 surgical patients during enflurane anaesthesia with lumbar epidural anaesthesia (EPI group) with those in 44 surgical patients during enflurane anaesthesia alone (GA group). Patients in the GA group demonstrated increases in urinary flow (114 +/- 46%) (mean +/- SE), Ccr (74 +/- 26%), and FENa (54 +/- 23%) during PGE1 infusion, which were not observed in the patients in the EPI group. Mean arterial pressure decreased during PGE1 infusion from 92 +/- 3 to 70 +/- 2 mmHg in the GA group (P < 0.01) and from 85 +/- 2 to 65 +/- 1 mmHg in the EPI group (P < 0.01). Plasma antidiuretic hormone concentration during surgery was 12.5 +/- 2.6 U.L-1 in the GA group and 2.3 +/- 0.8 U.L-1 in the EPI group (P < 0.001). It is concluded that PGE1-induced diuresis was prevented by lumbar epidural anaesthesia.

Alprostadil↗