Biomedical subjects

K Sekiya

Publications and source records attributed to K Sekiya.

At least 37 records · Page 2Linked to original sources

PubMed1994

Pancreastatin-like immunoreactivity of cerebrospinal fluid in patients with Alzheimer type dementia: evidence of aberrant processing of pancreastatin in Alzheimer type dementia.

The concentrations of pancreastatin-like immunoreactivity (PST-LI) of the cerebrospinal fluid (CSF) were measured in the patients with Alzheimer type dementia (ATD) and in age-matched normal subjects. The mean PST-LI concentration in the CSF of ATD patients was significantly lower than that of normal subjects. Gel chromatographic analysis revealed that the main PST-LI peak of ATD's CSF eluted at molecular weight (MW) 13.5 kDa. However, the age-related change of the molecular forms of PST-LI in CSF was observed in normal subjects as following; PST-LI in neonatal CSF showed one peak at MW 13.5 kDa, that of 16-64-year-old showed two peaks at MW 13.5 and 5.4 kDa, however, only one main peak was shown at MW 5.4 kDa in the CSFs of 72-85-year-old. These findings suggest that the production of PST-LI was decreased and the proteolytic cleavage, which should process big PST to PST (1-52) in normal subjects, was altered to that of neonatal type in the CNS of the patients with ATD.

Aged↗

PubMed1994

Unique change of pancreastatin-like immunoreactivity in cerebrospinal fluid by aging.

Using a specific antiserum for the C-terminal glycine amide region of human pancreastatin (PST), pancreastatin-like immunoreactivity (PST-LI) was measured in cerebrospinal fluid (CSF) from 447 subjects (368 +/- 10.8 pmol/l, mean +/- S.E.M.) free from endocrine diseases. The CSF contents of PST-LI showed a mountain-shape type change which peaked at 40 years of age. The highest concentration was found in the group of ages 40-49 years old (412 +/- 22.9 pmol/l) and the lowest concentration was found in the group of ages 80-89 years old (293.2 +/- 45.2 pmol/l) among various age groups. Gel chromatographic examination revealed the presence of two major forms (MW 13,500 and 5,400) of PST-LI in CSF. Because of the character of this antibody, the large molecular form is possibly an N-terminally elongated PST and the other may be PST-52. This may be the first report on the unique age-related change of PST concentration in CSF.

Adolescent↗

PubMed1994

Preclinical evaluation of MKC-442, a highly potent and specific inhibitor of human immunodeficiency virus type 1 in vitro.

MKC-442 (6-benzyl-1-ethoxymethyl-5-isopropyluracil or I-EBU) has recently been identified as a highly potent and specific inhibitor of human immunodeficiency virus type 1 (HIV-1) reverse transcriptase. Since the compound has favorable pharmacokinetic and toxicity profiles in vivo, we have evaluated MKC-442 for its inhibitory effect on the replication of HIV-1 in various cell cultures, including human peripheral blood lymphocytes and monocyte-macrophages. The 50 and 90% effective concentrations for HIV-1 (HTLV-IIIB strain) replication in MT-4 cells were 15 and 98 nM, respectively. MKC-442 was also inhibitory to HIV-1 replication in peripheral blood lymphocytes and monocyte-macrophages as determined by the production of p24 antigens in the culture supernatant. Fluorescence-activated cell sorter analysis revealed that MKC-442 was equally active against zidovudine-resistant mutants and zidovudine-susceptible strains. Furthermore, combinations of MKC-442 with either 3'-azido-3'-deoxythymidine, 2',3'-dideoxycytidine, or 2',3'-dideoxyinosine synergistically inhibited the replication of HIV-1. Thus, MKC-442 has been considered as a candidate for clinical efficacy studies.

Antiviral Agents↗

PubMed1994

The cell envelope structure of the lipopolysaccharide-lacking gram-negative bacterium Sphingomonas paucimobilis.

From the cell envelope preparation of Sphingomonas paucimobilis two membrane fractions with different densities were separated by sucrose density gradient ultracentrifugation. The high-density fraction contained several major proteins, phospholipids, and glycosphingolipids, which are the only glycolipids of this lipopolysaccharide-lacking gram-negative bacterium. The low-density fraction showed many minor bands of proteins by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and NADH oxidase activity was localized in this fraction. Combined with morphological data of vesicles formed by these membrane fractions, the high-density and low-density fractions were proposed to be an outer membrane and a cytoplasmic membrane, respectively. The localization of the glycosphingolipid was investigated also by means of immunoelectron microscopic analysis using a glycosphingolipid-specific antibody. The glycosphingolipid was shown to localize at the cell envelope, and the antigenic sugar portion was exposed to the bacterial cell surface. From these results the glycosphingolipid was assumed to have a function similar to that of the lipopolysaccharide of other gram-negative bacteria.

Antibodies, Bacterial↗

PubMed1994

In vivo wear pattern of experimental composite resins containing different filler components.

Using a scanning electron microscope (SEM) and an electron probe surface roughness analyzer (ERA), we conducted the in vivo study of the effect of various filler components on the wear of composite resins. Experimental light-cured composite resins were prepared employing three different filler components; -(1) Silica type, (2) Strontium type, and (3) Barium type. The filler content for all three types was 80 wt%, with the mean particlesize being 2.6 microns in diameter. The resin monomers consisted of 40 wt% Bis-GMA, 40 wt% TEGDMA and 20 wt% UTMA. These materials were placed in 2 mm diameter cylindrical cavities located in the OCA (occlusal contact area) or the CFA (contact free area) of cast crowns temporarily set in a volunteer patient's mouth. The crowns were removed at monthly intervals for longitudinal SEM observation. After two months, worn surfaces were also analyzed by ERA. The result showed that the wear patterns of the composites were characterized by the filler components, especially in the OCA.

Adult↗

PubMed1993

Comparison of plasma pancreastatin and GAWK concentrations, presumed processing products of chromogranin A and B, in plasma of patients with pancreatic islet cell tumors.

Plasma pancreastatin (PST) and GAWK, peptides processed from chromogranin A and B, were elevated in patients with various neuroendocrine tumors. In the present study, we measured plasma PST- and GAWK-like immunoreactivity (LI) concentrations in 12 patients with pancreatic islet cell tumors and evaluated them as a marker for these tumors. We also performed the gel filtration of the plasma from a gastrinoma patient and investigated the processing of PST and GAWK in plasma. Elevation of plasma PST-LI was found in 4 of 12 patients (33%) and elevation of plasma GAWK-LI was found in 6 of 12 patients (50%). A significant correlation was not found between plasma PST- and GAWK-LI concentrations of the patients. In the gel permeation chromatography of the plasma from a gastrinoma patient, PST-LI composed of a single peak but GAWK-LI composed of several components with wide range molecular weights.

Adenoma, Islet Cell↗

PubMed1993

[Mechanism of pore formation on erythrocyte membrane by streptolysin-O].

The erythrocyte membrane damaged by streptolysin-O (SLO) was observed in negative staining electron microscopy. It was confirmed that rings took arc (c-ring), sigmoidal (s-ring) or circular (o-ring) structures, and had electron-dense centers of a diameter of 24 nm and 4.9 nm width. We found a crown structure on top of the ring in view of side projection. The ring structure was constructed by three layers of the electron lucent top which was the crown, the second dark layer, and the third, base part which embedded in the erythrocyte membrane, and the heights were 3.2, 1.6, 5.0 nm, respectively. When the ghost membrane of erythrocyte was treated with SLO, the double of the inner and outer layers of a ring were observed by the negative-staining images. The figures of rings taken by under focus showed that one ring might be constituted between the 22 and 24 pair of inner and outer molecules. Totally 44 or 48 toxin molecules might be required for one O-ring.

Animals↗

PubMed1993

A ring-shaped structure with a crown formed by streptolysin O on the erythrocyte membrane.

Streptolysin O (SLO) is a membrane-damaging toxin produced by most strains of group A beta-hemolytic streptococci. We performed ultrastructural analysis of SLO-derived lesions on erythrocyte membranes by examining electron micrographs of negatively stained preparations. SLO formed numerous arc- and ring-shaped structures with or without holes on membranes. Rings formed on intact cell membranes had an inner diameter of ca. 24 nm and had distinct borders of ca. 4.9 nm in width, but the diameter of rings varied from 24 to 30 nm on membranes of erythrocyte ghosts. Image analysis of electron micrographs demonstrated that each ring was composed of an inner and an outer layer. Each layer contained an array of 22 to 24 SLO molecules. On the top of the ring, we found a characteristic crown that projected from the cell membrane. The crown was separated by an electron-dense layer from the basal part of the ring that was embedded in the lipid bilayer of the erythrocyte membrane. Heights of the three parts, namely, the crown (head), the space (neck), and the basal portion (base), were ca. 3.2, 1.6, and 5.0 nm, respectively, and we postulated that these parts are the constituents of a single SLO molecule. The volumes of SLO molecules in the inner and outer layers were calculated to be 77 and 88 nm3. On the basis of a model of the structure of SLO, we propose some new details of the mechanisms of hemolysis by SLO toxin.

Animals↗

PubMed1993

In vivo wear pattern of experimental composite resins based on different resin monomers.

This study investigated the effects of various monomer systems on composite resin wear in vivo. Experimental light-cured composite resins were prepared employing four different monomer systems: (1) Bis-GMA type, (2) D-2. 6E type, (3) UDMA type, (4) UTMA type. The resin monomers consisted of 70wt% main monomer and 30wt% TEGDMA. These composites contained 80wt% fine quartz. The resins were placed in 2 mm diameter cylindrical cavities located in the occlusal contact area or the contact free area in cast crowns, temporarily set in a mouth. The crowns were removed at monthly intervals, for longitudinal SEM observation. Two months after setting, wear was analyzed, using an electron probe surface roughness analyzer. Microabrasion of the resin matrix and loss of filler particles were observed for all types of monomer systems. The effect of matrix resin systems on occlusal wear was smaller than that of filler systems.

Bisphenol A-Glycidyl Methacrylate↗

PubMed1993

In vivo wear pattern of experimental light-cured hybrid composite resins.

This study evaluated the effect of various types of microfiller on the in vivo wear resistance of composite resins. Experimental light-cured composites with two different microfiller systems were prepared: (1) 56 wt % fine quartz filler, 21 wt% organic filler and 3 wt% colloidal silica filler (Hybrid type 1), and (2) 64 wt% fine quartz filler and 21 wt% colloidal silica filler (Hybrid type 2). The resin monomer consisted of 50 wt % Bis-GMA and 50 wt% TEGDMA. These materials were placed in 2 mm diameter cylindrical cavities located in the OCA (occlusal contact area) or the CFA (contact free area) in cast gold-silver-palladium alloy full coverage crowns, which were temporarily set in a volunteer patient's mouth. The crowns were removed at monthly intervals for SEM observation. Hybrid type 1, which contained organic fillers, showed bulk fractures in the OCA, by the second month of the experiment. However, reinforcement of the resin matrix by dispersion of microfiller provided Hybrid type 2 with superior wear resistance for up to two months.

Adult↗

PubMed1993

Direct observation of in vivo wear of composite resins.

This study developed a simple method for in vivo evaluation of wear on composite resins and examined the role of filler particles in this process. Experimental light-cured composite resins with two different filler systems were prepared: (1) 81 wt% fine quartz filler (Conventional type) and (2) 73 wt% organic filler (Microfilled type). The resin monomer consisted of 50 wt% Bis-GMA and 50 wt% TEGMA. These materials were placed in cylindrical cavities 2 mm in diameter located in the OCA (occlusal contact area) or the CFA (contact free area) in Au-Pd crowns, temporarily set in a volunteer's mouth. The crowns were removed at monthly intervals for longitudinal SEM observation. Results showed that the newly developed method was useful for observing the in vivo wear-patterns of composite resins. The two experimental composite resins with different filler systems showed quite different wear-patterns.

Adult↗

PubMed1993

Selective and synergistic inhibition of human immunodeficiency virus type 1 reverse transcriptase by a non-nucleoside inhibitor, MKC-442.

In the search for 1-[(2-hydroxyethoxy)methyl]-6-(phenylthio)thymine derivatives, we have found 6-benzyl-1-(ethoxymethyl)-5-isopropyl-uracil (MKC-442) to be a highly potent and selective inhibitor of human immunodeficiency virus type 1 (HIV-1) reverse transcriptase (RT). The IC50 value of MKC-442 for HIV-1 RT was 8 nM. MKC-442 did not inhibit HIV-1 RNase H, other RTs, or DNA polymerase alpha. Because its inhibitory pattern showed noncompetitive inhibition with regard to nucleotide substrates, its mode of action was considered to be allosteric inhibition. From the results of combination studies, MKC-442 was found to produce synergistic inhibition of HIV-1 RT with 3'-azido-2',3'-dideoxythymidine (AZT) 5'-triphosphate (AZT.TP). The dose of AZT.TP required for 50% inhibition was reduced to one tenth of control in the presence of a half dose of MKC-442. Although other allosteric inhibitors (Nevirapine, L-696,229, and R82,913) had the same specificity for enzyme inhibition, they did not show synergism with AZT.TP in the combination index and synergy plot analyses. Synergistic inhibition of HIV-1 replication by MKC-442 and AZT has also been observed in HIV-1-infected MT-4 cells. These results suggest that MKC-442 is a unique inhibitor of HIV-1 RT, and combination therapy with MKC-442 and AZT could be advantageous in the treatment of acquired immune deficiency syndrome.

Antiviral Agents↗

PubMed1993

Effect of cisapride on gastric emptying of indigestible solids and plasma motilin concentration in diabetic autonomic neuropathy.

To investigate the role of motilin in diabetic gastroparesis, we evaluated gastric emptying and plasma concentrations of motilin in diabetic patients. Gastric emptying of radiopaque marker was significantly delayed in the diabetics with autonomic neuropathy (n = 14) compared with the healthy controls (n = 6) (p < 0.01). Mean plasma motilin concentrations were significantly higher in the diabetics with autonomic neuropathy compared with the healthy controls (p < 0.01). A positive correlation was observed between gastric emptying and plasma motilin concentrations in the healthy controls (r = 0.955, p < 0.01), whereas these values were inversely correlated in the diabetics (r = 0.620, p < 0.01). Oral administration of cisapride (15 mg/day.14 day) significantly accelerated gastric emptying without an effect on plasma motilin concentration (p = 0.03). These observations suggest that gastric emptying in the diabetics with autonomic neuropathy is delayed despite elevated levels of motilin, and that cisapride accelerates gastric emptying, independent of the plasma motilin concentration.

Autonomic Nervous System Diseases↗

PubMed1992

Synthesis and antiviral activity of deoxy analogs of 1-[(2-hydroxyethoxy)methyl]-6-(phenylthio)thymine (HEPT) as potent and selective anti-HIV-1 agents.

The effect of substitution in the acyclic structure of 1-[(2-hydroxyethoxy)methyl]-6-(phenylthio)-thymine (HEPT) on anti-HIV-1 activity was investigated by synthesizing a series of deoxy analogs and related compounds. Preparation of 1-[(2-alkyloxyethoxy)methyl]-6- (phenylthio)thymine (2-4) derivatives was carried out based on alkylation of HEPT with primary alkyl halides. Preparation of the 1-[(alkyloxy)methyl]-6-(phenylthio)thymine (26-31) and 1-[(alkyloxy)methyl]-6-(arylthio)-2-thiouracil (32-45) derivatives was carried out on the basis of LDA lithiation of 1-[(alkyloxy)-methyl]thymine (9-14) and 1-[(alkyloxy)methyl]-2-thiouracil (15-25) followed by reaction with diaryl disulfides. The oxidative hydrolysis of the 2-thiouracil derivatives gave 1-[(alkyloxy)methyl]-6-(arylthio)uracil derivatives (46-57). 1-Alkyl-6-(phenylthio)thymine (59-61) derivatives were prepared on the basis of alkylation of 6-(phenylthio)thymine (58). Methylation of the hydroxyl group of HEPT did not affect the anti-HIV-1 activity of HEPT. Substitution of the 1-(2-hydroxyethoxy)methyl group by ethyl, butyl, methoxymethyl, (propyloxy)methyl, and (butyloxy)-methyl groups somewhat improved the original anti-HIV-1 activity of HEPT. Substitution with ethoxymethyl and (benzyloxy)methyl groups further potentiated the activity [EC50: 1-(ethoxy-methyl)-6-(phenylthio)thymine (27), 0.33 microM; 1-[(benzyloxy)methyl]-6-(phenylthio)thymine (31), 0.088 microM]. When the 5-methyl group of 27 and 31 was replaced by an ethyl or an isopropyl group, the anti-HIV-1 activity was improved remarkably [EC50: 5-ethyl-1-(ethoxymethyl)-6-(phenylthio)-uracil (46), 0.019 microM; 5-ethyl-1-[(benzyloxy)methyl]-6-(phenylthio)uracil (52), 0.0059 microM; 5-isopropyl-1-(ethoxymethyl)-6-(phenylthio)uracil (55), 0.012 microM; 5-isopropyl-1-[(benzyloxy)methyl]-6-(phenylthio)uracil (56), 0.0027 microM]. Introduction of two m-methyl groups into the phenylthio ring also potentiated the activity.

Antiviral Agents↗

PubMed1992

Structure-activity relationships of 1-[(2-hydroxyethoxy)methyl]-6-(phenylthio)thymine analogues: effect of substitutions at the C-6 phenyl ring and at the C-5 position on anti-HIV-1 activity.

The effect of substitution on the pyrimidine moiety of 1-[(2-hydroxyethoxy)methyl]-6-(phenylthio)thymine (HEPT) and 1-[(2-hydroxyethoxy)methyl]-6-(phenylthio)-2-thiothymine (HEPT-S) on anti-HIV-1 activity was investigated by synthesizing a series of 5-methyl-6-(arylthio) and 5-substituted-6-(phenylthio) derivatives. Preparation of the 5-methyl-6-(arylthio) derivatives was carried out based on either LDA lithiation of 1-[[2-(tert-butyldimethylsiloxy)ethoxy]methyl]thymine (3) and 1-[[2-(tert-butyldimethylsiloxy)ethoxy]methyl]-2-thiothymine (4) followed by reaction with diaryl disulfides or an addition-elimination reaction of 1-[[2-(tert-butyldimethylsiloxy)ethoxy]-methyl]-6- (phenylsulfinyl)thymine (31) with aromatic thiols. Preparation of the 5-substituted-6-(phenylthio) derivatives was carried out based on either C-5 lithiation of the 1-[[2-(tert-butyldimethylsiloxy)ethoxy]methyl]-6-(phenylthio)uraci l (41) with LTMP or the LDA lithiation of 5-alkyl-1-[[2-(tert-butyldimethylsiloxy)ethoxy]methyl]-2-thiouraci l derivatives 45-47. Substitution at the meta position of the C-6-(phenylthio) ring by the methyl group improved the original anti-HIV-1 activity of HEPT, and introduction of two m-methyl groups to the phenylthio ring further potentiated the activity [EC50: 6-[(3,5-dimethylphenyl)thio]-1-[(2-hydroxyethoxy)methyl]thymine (28), 0.26 microM; 6-[(3,5-dimethylphenyl)thio]-1-[(2-hydroxyethoxy)methyl]-2-thiothymin e (30), 0.22 microM]. When the 5-methyl group was replaced by an ethyl or an isopropyl group, the anti-HIV-1 activity of HEPT was also improved remarkably [EC50: 5-ethyl-1-[(2-hydroxyethoxy)methyl]-6-(phenylthio)-2-thiouracil (48), 0.11 microM; 5-isopropyl-1-[(2-hydroxyethoxy)-methyl]-6-(phenylthio)-2-thiouracil (50), 0.059 microM; 5-ethyl-1-[(2-hydroxyethoxy)methyl]-6-(phenylthio)-2-thiouracil (54), 0.12 microM; 5-isopropyl-1-[(2-hydroxyethoxy)methyl]-6-(phenylthio)-2-thiouracil (56), 0.063 microM]. 6-[(3,5-Dimethylphenyl)thio]-5-ethyl-1-[(2-hydroxyethoxy)methyl]thymine derivatives 51 and 57 and 6-[(3,5-dimethylphenyl)thio]-5-isopropyl-1-[(2- hydroxyethoxy)methyl]thymine derivatives 52 and 58 inhibited the replication of HIV-1 in the nanomolar concentration range.

Antiviral Agents↗

PubMed1992

Segmental gut transit in diabetes mellitus: effect of cisapride.

Gut transit using radiopaque markers was assessed in 5 healthy subjects and 24 diabetic patients. In the diabetics, various parameters including duration of the disease and diabetic complications, such as neuropathy, retinopathy and nephropathy, were determined, and the relationships between gut transit times and these complications were evaluated. The effect of cisapride on gut transit was studied in 10 diabetic patients. Large intestinal, descending colon, distal colon, and whole gut transit times were delayed in diabetics with autonomic neuropathy compared to controls and to diabetics without autonomic neuropathy (P less than 0.01). There was no difference in proximal colon transit times among them. An inverse correlation was observed between CVRR and the transit times for descending colon, distal colon, large intestine and whole gut. Large intestinal and whole-gut transit times were delayed in diabetics with retinopathy or with nephropathy compared to diabetics without those complications (P less than 0.01). In the diabetics, oral administration of 7.5 mg/day of cisapride for 2 weeks significantly accelerated descending colon transit (P less than 0.05) and partially accelerated distal colon, large intestinal and whole-gut transit. It is concluded that diabetics with autonomic neuropathy have delayed transits for the whole gut and that this finding is apparent to some extent in the distal colon but not in the proximal colon. Chronic oral administration of cisapride, a gastrointestinal prokinetic drug, was effective to improve these gastrointestinal motility disorders in diabetics with autonomic neuropathy.

Administration, Oral↗

PubMed1992

Biological potency of a fluorinated vitamin D analogue in hypoparathyroidism.

Several in vivo experiments have revealed that a synthesized fluorinated analogue of vitamin D, 26,26,26,27,27,27-hexafluoro-1,25-dihydroxyvitamin D3 (26,27-F6-1,25(OH)2D3) has a higher and longer-lasting biological activity than 1,25(OH)2D3 in calcium regulating actions. We evaluated the biological potency and the availability for clinical use of this compound in hypocalcemia associated with hypoparathyroidism. In an experimental setting, daily administration of 650 pmol/kg of 26,27-F6-1,25(OH)2D3 showed an equivalent effect to that of 3250 pmol/kg of 1,25(OH)2D3 in elevating whole blood ionized calcium levels in parathyroidectomized rats. Furthermore, an additional clinical study demonstrated that 0.5-1.5 micrograms/day of 26,27-F6-1,25(OH)2D3 were considered adequate maintenance doses in various types of hypoparathyroidism and that changes of medication to the same doses of 1,25(OH)2D3 resulted in prompt decline of urinary calcium excretion and of whole blood ionized calcium levels, and in recurrence of symptoms related to hypocalcemia. Although the mechanism responsible for the high potency of this analogue remains unclear, our experience confirms that 26,27-F6-1,25(OH)2D3 has higher biological activities in bone calcium mobilization and is more potent than 1,25(OH)2D3 in correcting hypocalcemia of hypoparathyroidism in a hospital setting.

Animals↗

PubMed1992

Transport of 1,5-anhydro-D-glucitol into human polymorphonuclear leukocytes.

1,5-Anhydro-D-glucitol (AG) is one of the main polyols and its structure resembles glucose. It has been proposed that decreased serum AG concentrations in diabetic patients are a novel indicator of diabetic metabolic derangement. However, the pathway of AG metabolism still remains to be clarified. In this study we investigated the transport of AG into human polymorphonuclear leukocytes (PMNLs) isolated from healthy volunteers and found that 0.1 mM 3-O-methy-D-glucose (3OMG) was equilibrated with a half saturation time of 10 s, while the uptake rate of AG was much slower. The concentration dependence of AG uptake revealed that the AG transport velocity reached a plateau, with a Km of about 50 mM and Vmax of about 25 nmol/min/10(7) cells. Transport of 14C-labeled 3OMG was inhibited by unlabeled D-glucose or AG in a dose-dependent manner. The mean inhibition constant (Ki) for D-glucose and for AG were 1.06 and 4.93 mM, respectively. Cytochalasin B (20 microM) inhibited 3OMG transport by 90% but AG transport by only 50%. S/V for 14C-labeled AG transport plotted against the concentration of unlabeled 3OMG showed a non-linear and biphasic pattern. These results suggest that AG influx into PMNLs is mediated not only by the cytochalasin B-sensitive glucose transport system but also via another facilitated transport system.

3-O-Methylglucose↗