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K Hayashi

Publications and source records attributed to K Hayashi.

At least 361 records · Page 20Linked to original sources
PubMed2000

Role of protein kinase C in angiotensin II-induced constriction of renal microvessels.

UNLABELLED: Role of protein kinase C in angiotensin II-induced constriction of renal microvessels. BACKGROUND: Although angiotensin II (Ang II) exerts its action through multiple vasomotor mechanisms, the contribution of phosphoinositol hydrolysis products to Ang II-induced renal vasoconstriction remains undetermined. METHODS: The role of protein kinase C (PKC) in Ang II-induced afferent (AFF) and efferent (EFF) arteriolar constriction was examined using the isolated perfused hydronephrotic rat kidney. RESULTS: Ang II (0.3 nmol/L)-induced EFF constriction was refractory to inhibition of voltage-dependent calcium channels by pranidipine (1 micromol/L, 19 +/- 2% reversal) but was completely reversed by a PKC inhibitor, chelerythrine (1 micromol/L, 96 +/- 2% reversal). Furthermore, direct PKC activation by phorbol myristate acetate (PMA; 1 micromol/L) caused prominent EFF constriction, and this constriction was inhibited by manganese and free calcium medium. In contrast, Ang II-induced AFF constriction was completely abolished by pranidipine (98 +/- 4% reversal) and was partially inhibited by chelerythrine (55 +/- 3% reversal). Although PMA elicited marked AFF constriction, this constriction was insensitive to the calcium antagonist, but was totally inhibited by manganese or free calcium medium. CONCLUSIONS: PKC plays an obligatory role in Ang II-induced EFF constriction that requires extracellular calcium entry through nonselective cation channels. In contrast, in concert with our recent findings demonstrating a complete dilation by thapsigargin, Ang II-induced AFF constriction is mainly mediated by inositol trisphosphate (IP3) and voltage-dependent calcium channel pathways, but could not be attributed to the PKC-activated calcium entry pathway (for example, nonselective cation channels). Rather, Ang II-stimulated PKC may cross-talk to the IP3/voltage-dependent calcium channel pathway and could modulate the vasoconstrictor mechanism of the AFF. Thus, the role of PKC during Ang II stimulation differs in AFF and EFF, which may constitute segmental heterogeneity in the renal microvasculature.

Angiotensin II↗
PubMed2000

Renal protective effect of troglitazone in Wistar fatty rats.

Although it is known that renal injury develops in obesity and diabetes mellitus, there have been no investigations examining the impact of insulin resistance per se on the development of renal injury. The present study was undertaken to examine whether insulin resistance and obesity influence urinary protein excretion (UPE) in female heminephrectomized Wistar fatty rats (WFRs). After 24 weeks of heminephrectomy in WFRs, the body weight ([BW], 465+/-18 g; n = 6), blood pressure (155+/-5 mm Hg), serum insulin to glucose ratio (1.31+/-0.39 microU/mg), and daily UPE (24+/-7 mg/d) were greater versus Wistar lean rats ([WLRs] 258+/-8 g, 134+/-1 mm Hg, 0.19+/-0.06 microU/mg, and 5+/-1 mg/d, respectively; n = 6), whereas blood glucose levels did not increase significantly. In WFRs, long-term (ie, 24 weeks) treatment with troglitazone, an insulin-sensitizing agent, improved the serum insulin to glucose ratio (0.17+/-0.09 microU/mg), reduced blood pressure (to 140+/-4 mm Hg), and decreased UPE (to 7+/-1 mg/d), although it had no effect on BW. Of note, with troglitazone treatment, the reduction in proteinuria preceded the correction of hypertension (ie, at week 12). In conclusion, our study suggests that insulin resistance per se causes proteinuria that does not appear to depend on blood pressure. Furthermore, long-term therapy with troglitazone may be a useful tool for the treatment of renal injury in the insulin-resistant condition.

Animals↗
PubMed2000

Characterization of the renal action of pranidipine in the rat.

Although calcium antagonists elicit predominant dilation of afferent arterioles that might be associated with glomerular hypertension, there have been reported diverse observations demonstrating the effect of calcium antagonists on the progression of renal injury. The present study examined the effect of pranidipine (CAS 99522-79-9) on the renal microvascular tone in the isolated perfused hydronephrotic rat kidney, and the progression of renal insufficiency in subtotally nephrectomized spontaneously hypertensive rats. In the hydronephrotic kidney, angiotensin II caused marked constriction of both afferent and efferent arterioles. The subsequent addition of pranidipine (10 nmol/l, 100 nmol/l, 1 mumol/l) elicited dose-dependent afferent arteriolar dilation, with 97 +/- 3% reversal at 1 mumol/l. In contrast, efferent arterioles were resistant to pranidipine, with only 20 +/- 4% reversal at 1 mumol/l. In subtotally nephrectomized rats, 10-week treatment with pranidipine (3.0 mg/kg/day) markedly decreased blood pressure (from 270 +/- 6 to 158 +/- 8 mmHg) and improved renal histopathological changes, including glomerular and arteriolar sclerosis. Proteinuria was also less than than in the control rats (233 +/- 5 vs. 305 +/- 26 mg/day). Thus, although glomerular hypertension might develop as a consequence of preferential afferent arteriolar dilation, pranidipine actually improved the renal injury in subtotally nephrectomized SHR. These ostensibly discrepant observations could be attributed to the simultaneous reduction in blood pressure and the salutary actions of this agent mediated by non-hemodynamic mechanisms.

Animals↗
PubMed2000

Endoscopic decompression procedure in acute obstructing colorectal cancer.

BACKGROUND AND STUDY AIMS: In the treatment of acute obstructing colorectal cancer, a nasoenteric ileus tube is not capable of providing sufficient decompression of the enlarged intestine immediately, and it may cause the patients throat pain. We therefore assessed the effectiveness of an endoscopic decompression procedure using a transanal ileus tube for acute obstructing colorectal cancer. PATIENTS AND METHODS: Five patients (five women, mean age 62) with colorectal cancer ileus underwent endoscopic decompression procedures between July 1994 and March 1999. The stricture was first negotiated using a guide wire 300 cm in length, and was then dilated using 8 Fr and 26 Fr dilating catheters. Immediately after a transanal ileus tube 120 cm in length with an outside diameter of 22 Fr was inserted, the intestinal tract was cleaned. RESULTS: No leakage from a colorectal anastomosis occurred during this endoscopic decompression procedure. Immediately after insertion of a decompression procedure tube, radical surgery could be performed after adequate preoperative examination and colorectal preparation. CONCLUSIONS: This procedure may be helpful in allowing immediate preoperative examination and scheduling of a radical operation for acute obstructing colorectal disease.

Acute Disease↗
PubMed2000

Lack of association between TTV viral load and aminotransferase levels in patients with hepatitis C or non-B-C.

TT virus (TTV) is a newly identified un-enveloped single-stranded DNA virus. Although TTV was initially thought to be a new hepatitis virus, it is still unclear whether it causes hepatitis. To clarify the natural history and pathogenesis of TTV infection, serial serum samples from patients with chronic hepatitis were analysed. TTV DNA was quantified by real-time detection polymerase chain reaction assay (RTD-PCR), which was adapted for TTV. Five patients with chronic hepatitis, 4 with hepatitis C and 1 with non-B-C, were studied. The study period ranged from 9 to 50 months. In 3 patients there were frequent increases in TTV DNA titres, but no concomitant elevation of the aminotransferase (ALT) levels. In 2 patients who were treated with interferon, the changes in TTV titres were not synchronized with those of the ALT levels. Thus, in cases of chronic hepatitis, no correlation was observed between the serum TTV DNA titres and the ALT levels.

Adult↗
PubMed2000

Elevation of mRNA levels of tissue-type plasminogen activator and urokinase-type plasminogen activator in hippocampus and cerebral cortex following middle cerebral artery occlusion in rats.

Tissue-type plasminogen activator (tPA) and urokinase-type plasminogen activator (uPA) have been used for thrombolitic therapy. In contrast, it is suggested that these compounds might be involved in neuronal cell damage. The activation and the function of tPA and uPA are less understood in ischemic brain tissue. Therefore, changes in tPA and uPA mRNA in rat brain tissue after MCA occlusion and in the neuronal cell line, PC12 cells, during the hypoxic stimulation were examined. Permanent middle cerebral artery (MCA) occlusion was induced by advancing a filament into the internal carotid artery in 36 adult male Sprague-Dawley rats. The ischemic cerebral cortex and contralateral cortex of MCA area, and bilateral hippocampus were collected at 0 (controls), 1, 3, 6, 12 and 24 h after occlusion. Hypoxia was induced in PC12 cells with a multigas incubator (set to 1% O2). The quantitative reverse transcription-polymerase chain reaction acted as a measurement of alteration in mRNA levels. The mRNA levels of tPA and uPA were significantly increased after MCA occlusion in the ischemic cerebral cortex. The magnitude of the increase in tPA and uPA mRNA in 24 h after occlusion was twice the value in sham-operated rat (0 h). The increases of tPA mRNA were time-dependent in insult and contralateral hippocampus. The increase of uPA mRNA was also seen in the hippocampus bilaterally, although the increase was more significant on the ipsilateral side. In PC12 cells, necrotic (approximately 35%) and apoptotic cells (approximately 65%) could be distinguished by hypoxic stimulus for 24 h, and the mRNA for tPA was significantly increased for 6 h-12 h, while the mRNA for uPA was not detected at any point in the study. Our results suggest that focal ischemia might result in the activation of these proteases not only in the insult but also in the contralateral brain tissue.

Animals↗
PubMed2000

Symptomatic peripheral vascular tree stenosis. Comparison of subtracted and nonsubtracted 3D contrast-enhanced MR angiography with fat suppression.

OBJECTIVE: To determine the clinical feasibility of contrast-enhanced three-dimensional (3D) MR angiography (MRA) with fat suppression spectral inversion at lipids and to compare subtracted and nonsubtracted images. MATERIAL AND METHODS: In 13 patients suspected of having lower extremity ischemia, 3D dynamic contrast-enhanced MRA of the iliac and femoral arteries was performed using the fat suppression technique. The validity of the MRA interpretations of the degree of stenoses was evaluated by comparing with conventional angiography as the gold standard. The contrast-to-noise (C/N) ratios of both subtracted and nonsubtracted maximum-intensity-projection (MIP) images were calculated. RESULTS: In the arteries with stenosis of 50% or greater, the sensitivity and specificity of the subtracted MR angiograms were 100% and 96.5%, respectively, not significantly different from the corresponding values in nonsubtracted MRAs (100% and 94.1%, respectively). The C/N ratios of the subtracted images were significantly higher than those of the nonsubtracted images (p<0.001). CONCLUSION: With this technique, fat suppression can be performed with only a slight increase in the examination time. A lower dose of contrast material can be used in MRA with fat suppression than without it. Subtracted MRA improves the ease of interpretation compared to nonsubtracted MRA.

Aged↗
PubMed2000

A BASH/SLP-76-related adaptor protein MIST/Clnk involved in IgE receptor-mediated mast cell degranulation.

Cross-linking of the high-affinity IgE receptor (FcepsilonRI) on mast cells by IgE-antigen complex triggers signal transduction cascades leading to the release of inflammatory mediators and production of cytokines, which are critical for the development of allergic reactions. We have identified a novel member of the BASH/SLP-76 immunoreceptor-coupled adaptor family expressed in mast cells, termed MIST (for mast cell immunoreceptor signal transducer), which has later been found to be identical to a recently reported cytokine-dependent hemopoietic cell linker, Clnk. Upon FcepsilonRI cross-linking, MIST/Clnk is tyrosine phosphorylated and associates with signaling proteins, phospholipase Cgamma, Vav, Grb2 and linker for activation of T cells (LAT). Overexpression of a mutant form of MIST/Clnk inhibited FcepsilonRI-mediated degranulation, increase in intracellular Ca(2+), NF-AT activation and phosphorylation of LAT. As a crucial signaling component for FcepsilonRI-induced mast cell degranulation, MIST/Clnk might serve as a target for anti-allergic therapy.

Adaptor Proteins, Signal Transducing↗
PubMed2000

Evaluation of (1R,2R)-1-(5'-methylfur-3'-yl)propane-1,2,3-triol, a sphydrofuran derivative isolated from a Streptomyces species, as an anti-herpesvirus drug.

(1R,2R)-1-(5'-Methylfur-3'-yl)propane-1,2,3-triol (MFPT), a stable anhydro derivative of sphydrofuran, was obtained from the culture broth of STREPTOMYCES: sp. strain FV60 as an inhibitor of herpes simplex virus type 1 (HSV-1). The compound showed antiherpetic activity with a 50% inhibitory concentration of 1.2 IM in an in vitro assay system. Although the binding of virus to host cells was not inhibited, the penetration of virus into cells was moderately blocked by MFPT. Some of the viruses, once they had penetrated cells, failed to form plaques in the presence of MFPT. When added to the late stages of HSV-1 replication, MFPT also inhibited virus production. Sodium dodecyl sulphate-polyacrylamide gel electrophoresis analysis of isotope-labelled HSV-specific proteins revealed that a protein or proteins with reduced molecular weight (about 120 kDa) was clearly detected in cells treated with MFPT. Western blot analysis with antibodies against three HSV-specific glycoproteins (gB, gC and gD) showed a significant difference in gC synthesis between untreated and MFPT-treated cells. Release of progeny viruses was suppressed by MFPT. Syncytium formation by HSV-1 strain HF was inhibited and small plaques with rounded cells were formed in MFPT-treated cell cultures. When wild-type HSV-1 was serially propagated under the selective pressure of MFPT, resistant virus emerged. MFPT-resistant progeny were accompanied by the formation of plaques with rounded cells. These results, taken together, suggest that MFPT might act by limiting the maturation of HSV-specific glycoproteins, particularly of HSV-1 gC.

Adsorption↗
PubMed2000

Chloroplast tubules visualized in transplastomic plants expressing green fluorescent protein.

A fusion between the plastid psbA promoter and the green fluorescent protein gene (gfp) was introduced into the tobacco chloroplast genome by stable plastid transformation. GFP was synthesized actively and exclusively in the chloroplasts. Tubular projections filled with GFP but containing no chlorophyll were visualized for the first time in chloroplasts of these transplastomic plants. Occasionally, the tubules connect chloroplasts with each other, suggesting the possibility of the exchange of endogenous proteins. However, the fusion of protoplasts between the transplastomic and wild-type plants showed that such chloroplast connections might be rare in mesophyll protoplasts.

Chloroplasts↗
PubMed2000

Module shuffling of a family F/10 xylanase: replacement of modules M4 and M5 of the FXYN of Streptomyces olivaceoviridis E-86 with those of the Cex of Cellulomonas fimi.

To facilitate an understanding of structure-function relationships, chimeric xylanases were constructed by module shuffling between the catalytic domains of the FXYN from Streptomyces olivaceoviridis E-86 and the Cex from Cellulomonas fimi. In the family F/10 xylanases, the modules M4 and M5 relate to substrate binding so that modules M4 and M5 of the FXYN were replaced with those of the Cex and the chimeric enzymes denoted FCF-C4, FCF-C5 and FCF-C4,5 were constructed. The k(cat) value of FCF-C5 for p-nitrophenyl-beta-D-cellobioside was similar to that of the FXYN (2.2 s(-1)); however, the k(cat) value of FCF-C4 for p-nitrophenyl-beta-D-cellobioside was significantly higher (7.0 s(-1)). The loss of the hydrogen bond between E46 and S22 or the presence of the I49W mutation would be expected to change the position of Q88, which plays a pivotal role in discriminating between glucose and xylose, resulting in the increased k(cat) value observed for FCF-C4 acting on p-nitrophenyl-beta-D-cellobioside since module M4 directly interacts with Q88. To investigate the synergistic effects of the different modules, module M10 of the FCF-C4 chimera was replaced with that of the Cex. The effects of replacement of module M4 and M10 were almost additive with regard to the K:(m) and k(cat) values.

Amino Acid Sequence↗
PubMed2000

Analysis of p53 tumour suppressor gene somatic mutations in rheumatoid arthritis synovium.

OBJECTIVE: In order to study the role of the p53 tumour suppressor gene in the proliferation of rheumatoid arthritis (RA) synovium, we analysed the mutation of p53 in the synovial fibroblast-like type B synoviocyte from RA patients. METHODS: Synovial fibroblast-like type B synoviocytes were prepared from the synovial tissues from nine Japanese patients with RA. The p53 cDNA region from exons 4-11 was screened for mutations by the streamlined mutation detection method in which polymerase chain reaction (PCR) products are post-labelled and are analysed by automated capillary electrophoresis using single-strand conformation polymorphism conditions, followed by direct sequencing of the subclones of the PCR products. RESULTS: p53 mutation with possible functional alteration was detected in four of the nine RA patients (44.4%). Of a total of 262 p53 cDNA subclones, 10 subclones were carrying 10 p53 mutations, eight of which were associated with amino acid alterations or protein truncation. Of the p53 functional mutations, a substitution of Gly at amino acid residue 245 to Asp (G245D) was identified in two patients in three subclones. G245D was the first mutation that was recurrently identified in different RA individuals. G245D is also one of the relatively common mutations in human cancers. CONCLUSIONS: In some patients with RA, dysfunction of p53 might play a role in the proliferation of the synovial tissue. G245D mutation might especially need further study as it is the first recurrently identified p53 mutation in RA and is also one of the frequently identified mutations in human cancers.

Arthritis, Rheumatoid↗
PubMed2000

Regulation of angiotensin II production and angiotensin receptors in microvascular endothelial cells from bovine corpus luteum.

Recent findings suggest that the ovarian renin-angiotensin system regulates ovarian function through the paracrine/autocrine actions of angiotensin (Ang) II. The aims of this study were to investigate 1) the endothelial cell capacity to convert Ang I to Ang II, 2) the effects of endocrine and paracrine/autocrine factors on Ang II production in microvascular endothelial cells (MVE) derived from the developing corpora lutea (CL), and 3) the relationship between Ang II peptide concentration and expression of mRNA for angiotensin type 1 and 2 receptors (ATR1 and AT2R) in the bovine CL at different stages of the estrous cycle. When Ang I was added to the MVE at a concentration of 10(-9) M, it was converted to Ang II (21%). The production of Ang II from Ang I time-dependently rose for 24 h. Addition of captopril (an inhibitor of Ang-converting enzyme [ACE]) to the MVE cultures significantly inhibited Ang II production from 6 h to 24 h (P < 0.05). Addition of estradiol-17beta (E(2)) + vascular endothelial growth factor and E(2) + basic fibroblast growth factor to MVE cultures increased Ang II production, whereas E(2) or growth factors alone had no effect. Specific transcription for AT1R and AT2R was detected in bovine CL and MVE. There were no significant changes in Ang II tissue concentration or AT1R mRNA expression using reverse transcription-polymerase chain reaction during the estrous cycle. In contrast, AT2R mRNA expression decreased during the midluteal phase (P < 0.05) and increased to the highest level during the late luteal phase (P < 0.05). Results demonstrated that Ang II is generated from Ang I in MVE isolated from the developing bovine CL, indicating that MVE have ACE activity. In addition, mRNA expression for Ang II receptors was detected in the bovine CL and the luteal MVE. These results suggest that Ang II is produced by actions of the local renin-angiotensin system, at least in part, on MVE in the bovine CL, and that this peptide may be involved in the regulation of luteal function during early development and luteolysis.

Angiotensin I↗
PubMed2000

Periovulatory changes in the local release of vasoactive peptides, prostaglandin f(2alpha), and steroid hormones from bovine mature follicles in vivo.

We previously proposed that an endothelin-angiotensin-atrial natriuretic peptide system may contribute to inducing ovulation of mature bovine follicles by modulating follicular secretion of steroids and prostaglandins (PGs). Thus, this study aimed to determine the real-time changes in the local release of angiotensin II (Ang II), endothelin (ET), atrial natriuretic peptide (ANP), PGF(2alpha), and steroid hormones from bovine mature follicles during the periovulatory period in vivo. Seven cows were treated for superovulation using FSH and PGF(2alpha) injections. Two dialysis capillary membranes per follicle were surgically implanted into the theca layer of mature follicles and connected to a microdialysis system (MDS). Fractions of the perfusate were collected from Day -1 (Day 0 = LH surge) to Day 3. Five out of seven treated cows were normally ovulated, and the newly formed corpora lutea were observed at the end of the experiment. In these five ovulated cows, the release of estradiol, androstenedione, and progesterone in the theca layer increased (P < 0.05) synchronously with the LH surge. Acute increases in PGF(2alpha) and Ang II concentrations in the ovarian venous plasma (OVP) were observed at 24-48 h after the peak of the LH surge, when multiple ovulations were expected to occur. The follicular Ang II release was low during the pre-LH surge period and rose (P < 0.05) at the beginning of the increase in the LH surge. On the other hand, ET-1 release dropped (P < 0.05) when plasma LH started to increase. However, no clear changes in ANP concentration in the MDS perfusate and plasma were observed. The above local changes in Ang II, PGF(2alpha), as well as steroid hormones were not observed in cows (n = 2) that did not show an LH surge and ovulation. The present results demonstrate for the first time the local release of Ang II, ET-1, and ANP from the bovine mature follicle in real-time in vivo and show that Ang II and PGF(2alpha) concentrations in the OVP acutely increase around the time of ovulation. The overall results support the concept of a local functional ET-Ang-ANP system in the bovine mature follicle that may be involved in the ovulatory process.

Angiotensin II↗
PubMed2000

Single-beat estimation of ventricular end-systolic elastance-effective arterial elastance as an index of ventricular mechanoenergetic performance.

BACKGROUND: The ratio of ventricular end-systolic elastance (Ees) to effective arterial elastance (Ea) is known to reflect not only ventricular mechanical performance but also energetic performance. Despite these useful features, technical difficulties associated with estimating Ees make the clinical application of Ees/Ea impractical. We developed a framework to estimate Ees/Ea without measuring ventricular volume or altering the loading condition. METHODS: To achieve this goal, we approximated the ventricular time-varying elastance curve with two straight lines, one for the isovolumic phase and the other for the ejection phase, and characterized the curve with the slope ratio, k, of these two straight lines. Using the concept of the pressure-volume relationship, Ees/Ea is algebraically expressed as Ees/Ea = Pad/Pes (1 + k. ET/PEP) - 1, where Pes is end-systolic pressure, Pad is aortic diastolic pressure, ET is ejection time, and PEP is pre-ejection period. In 11 anesthetized dogs, we recorded arterial and ventricular pressures and ventricular volume and estimated Ees and Ea under various contractile states and loading conditions. RESULTS: An empirical relation between k and Ees/Ea was found as k = 0.53 (Ees/Ea)0.51. Simultaneous solution of these two equations yielded Ees/Ea as a function of Pad/Pes and ET/PEP. The estimated Ees/Ea values correlated well with the measured Ees/Ea values ([Measured Ees/Ea] = 0.96 [Estimated Ees/Ea] + 0.098, r = 0.925, SEE = 0.051). CONCLUSIONS: The proposed framework is capable of estimating Ees/Ea from ventricular and aortic pressure.

Animals↗
PubMed2000

The mechanism of joint capsule thermal modification in an in-vitro sheep model.

The purpose of this study was to understand the mechanism responsible for joint capsule shrinkage after nonablative laser application in an in-vitro sheep model. Femoropatellar joint capsular tissue specimens harvested from 20 adult sheep were treated with one of three power settings of a holmium:yttrium-aluminum-garnet laser or served as a control. Laser treatment significantly shortened the tissue and decreased tissue stiffness in all three laser groups, whereas failure strength was not altered significantly by laser treatment. Transmission electron microscopic examination showed swollen collagen fibrils and loss of membrane integrity of fibroblasts. A thermometric study revealed nonablative laser energy caused tissue temperature to rise in the range of 64 degrees C to 100 degrees C. Electrophoresis after trypsin digestion of the tissue revealed significant loss of distinct alpha bands of Type I collagen in laser treated samples, whereas alpha bands were present in laser treated tissue without trypsin digestion. The results of this study support the concept that the primary mechanism responsible for the effect of nonablative laser energy is thermal denaturation of collagen in joint capsular tissue associated with unwinding of the triple helical structure of the collagen molecule.

Analysis of Variance↗