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Biomedical subjects

M Imai

Publications and source records attributed to M Imai.

At least 217 records · Page 12Linked to original sources
PubMed1995

Modulation of protein kinase C produces glucose-dependent alterations in hemodynamics and metabolism in the perfused liver in fasted rats.

Protein kinase C (PKC) has been suggested to be involved in the regulation of hepatic blood flow and metabolism. To confirm the role of PKC, we studied the effects of active and inactive PKC modulators on hemodynamics and metabolism in the perfused rat liver. In addition, the influence of glucose concentration in the medium was studied. The liver was isolated from fasted Sprague-Dawley rats and perfused through the portal vein at a constant pressure of 12 cm H2O. 4 alpha-Phorbol 12,13-didecanoate, an inactive phorbol ester for PKC, slightly decreased hepatic flow only when its initial concentration was raised to 20 microM. In contrast, 4 beta-phorbol 12,13-didecanoate, an active phorbol ester for PKC, at initial concentrations of 80 nM to 1.28 microM decreased hepatic flow and oxygen consumption in a dose-dependent manner, and increased lactate production. HA-1004, a relatively inactive PKC inhibitor, at an initial concentration of 33 microM did not modify the effects of phorbol 12-myristate 13-acetate (PMA), a potent PKC activator. However, H-7, a relatively specific PKC inhibitor, at a concentration of 33 microM attenuated the effects of PMA. The effects of PMA were enhanced by an increase in n-glucose concentration from 10 to 25 mM but not by an increase in L-glucose concentration. These results suggest that modulation of PKC exerts glucose-dependent influences on hepatic flow and metabolism.

Animals↗
PubMed1995

[Changes in plasma tissue plasminogen activator (t-PA) and plasminogen activator inhibitor 1 (PAI-1) by the interferon treatment for chronic hepatitis C].

To determine the effects of interferon (IFN) treatment for chronic hepatitis C on vascular endothelium, we measured the concentrations of tissue plasminogen activator (t-PA) and its inhibitor (PAI-1) in the plasma from patients before and after IFN treatment for 14 consecutive days. The plasma t-PA and PAI-1 levels were measured before and after treatment. The plasma t-PA level was significantly increased after IFN treatment (p < 0.01) but no significant difference in plasma PAI-1 level was observed before and after treatment. The ratio of t-PA/PAI-1 was significantly increased after IFN treatment (p < 0.05). These changes may be caused by the effect of IFN on endothelium, leading to an activation of the endothelium derived fibrinolysis factors. Increase in plasma t-PA concentration may induce hyperfibrinolysis which may be one of the causes of suborbital hemorrhage. Further study on the fibrinolysis pathway in the blood is necessary to elucidate the mechanisms of the many side effects observed during IFN treatment.

Adult↗
PubMed1995

[A case of Ebstein's anomaly treated by tricuspid valve replacement].

A 8-year-old girl with Ebstein's anomaly was operated on because of progressive heart failure caused by severe tricuspid regurgitation. At the operation, the tricuspid leaflets were found to be destroyed, and the annulus was very enlarged. The enlarged true tricuspid annulus was constricted using the DeVega method, and the tricuspid valve was replaced on the true annulus using a porcine valve. To avoid injury to the auriculoventricular bundle, the suture line was shifted to the false annulus at the portion close to the course of His' bundle. Postoperative course was uneventful in satisfactory condition. The role of valve replacement in the treatment of Ebstein's anomaly of the tricuspid valve is not only to improve valve formation, but also to secure the function of the right ventricle. It is ideal to replace the tricuspid valve on the true annulus provided that the injury to the His' bundle is safely avoided.

Child↗
PubMed1995

[Role of interstitium in the regulation of renal tubular solute transport].

The physiological significance of the renal interstitium is reviewed with special reference to solute transport. The renal tubules and vasculatures participate in essential parts of the nephron functions. The renal interstitium, interposing among these structures, regulates solute transport across the renal tubules. In the renal cortex, changes in the interstitial pressure modulate the proximal tubular fluid reabsorption via paracellular shunt pathways. In the renal medulla, the interstitium may play an important role in the lateral diffusion of solutes and water, contributing to the mechanisms of urine concentration, as well as, medullary potassium recycling and ammonia excretion.

Animals↗
PubMed1995

[Finding appropriate tube position by the cuff palpation method in children].

The present study was designed to examine whether palpation of the endotracheal tube cuff indicates appropriate positioning in the children. In 59 children, we used a cuffed endotracheal tube (3.5-5 mm ID) to measure the distance from the carina to the distal tip of the endotracheal tube, when we can palpate the endotracheal tube cuff between the cricoid cartilage and the suprasternal notch. Following slow induction of anesthesia and muscle relaxation, each patient was intubated with a cuffed endotracheal tube of size suitable for age. The cuff was inflated with 0.5-1 ml of air, and palpated between the cricoid cartilage and the suprasternal notch. The distance between the carina and the tube tip measured by a fiberscope was more than 1.0 cm, which is thought to be safe to prevent bronchial intubation. The cuff was deflated after measurement. There were no complications attributable to use of cuffed endotracheal tubes. We concluded that the cuff palpation method was a rapid, reliable and simple technique to ensure the proper tube position in children.

Child↗
PubMed1995

[Ultrastructural study of lens fiber cells by quick-freezing and deep-etching].

The ultrastructure of lens fiber cytoskeleton was studied by quick-freezing and deep-etching. Lenses of 5 Wistar male rats were divided into lens cortex and lens nucleus. Filamentous structures were clearly observed in the cortical fiber cells, which had diameters in 10 approximately 15 nm or about 5 nm. They showed a meshwork structure. On the other hand, the filamentous structures showed a linear, dense, and laminar pattern in the nuclear fiber cells. These ultrastructural changes of cytoskeletons may be related to the elongation and differentiation of lens fiber cells and may be important for maintaining transparency of the lens.

Animals↗
PubMed1995

Effects of panretinal photocoagulation on photopic ERG in normal rabbit eyes.

The effects of panretinal photocoagulation (PRP) on photopic ERG were studied in normal pigmented rabbit eyes. Photopic ERGs were recorded before PRP and one day, one week and 4 weeks after PRP. Markedly reduced amplitude and delayed implicit time were observed one day after PRP. Four weeks after PRP, amplitude showed subtotal recovery while implicit time, showing tendency of reduction, was still significantly delayed. The delay in implicit time and the reduction in amplitude after PRP was probably due to serous retinal detachment and/or retinal edema caused by breakdown of the blood-retinal barrier. However, the findings at 4 weeks after PRP might be explained by the reduced number of photoreceptor cells; the mild decrease in the amplitude of photopic ERG might be caused by the reduced number of cones, while significantly delayed implicit time of the photopic ERG might be caused by reduced number of rods.

Adaptation, Ocular↗
PubMed1995

Recovery of photopic ERG from pressure-induced retinal ischemia in rabbit eyes.

Using precise experimental methods, we evaluated the recovery from pressure-induced ischemia in rabbit retina using photopic electroretinography (ERG). The recovery was evaluated and documented in terms of the increasing amplitude and the decreasing delay of implicit time in the photopic ERG after inducing 30-, 60- and 90-minute ischemia. A ganzfeld dome was utilized to stimulate both the experimental and the control fellow eye. The changes in ERG parameters in the ischemic eye were assessed by comparison with the values simultaneously obtained in the fellow eye, which could minimize the effect of anesthesia. One hour after reperfusion, the implicit time returned to almost the same value as that in the fellow eye in eyes with 30-minute ischemia, while it showed significant delay in eyes with 60-minute ischemia. The amplitude was smaller than that in the fellow eye in eyes with both 30- and 60-minute ischemia. Photopic ERG was not recorded one hour after reperfusion in more than half the eyes with 90-minute ischemia.

Anesthesia↗
PubMed1994

Essential residues in V(D)J recombination signals.

Recombination signal sequences for V(D)J joining consist of a conserved heptamer (CACAGTG) and a nonamer (ACAAAAACC) separated by a spacer of a constant length (12 bp or 23 bp). In the present study, we have analyzed various recombination signal mutations for their effects in V(D)J joining. Using a retroviral vector, we introduced mutant substrates stably into pre-B cells, and assayed recombination using the lacZ gene as a reporter. This method allowed us to study recombination in a single copy within the context of the host cell chromosome. Because this assay did not show any detectable background, it was quite useful in the analysis of low level recombinations. In the heptamer, mutations in the first three residues severely dropped the joining rates. Among them, the first residue adjacent to the recombination site was found to be most essential. Although mutations in the heptamer reduced the joining rate to various extents, they did not lower the site-specificity of recombination. With regard to the nonamer, the presence of three consecutive A residues was necessary for efficient recombination. Furthermore, the nucleotides flanking the A-rich core needed to be other than A residues, probably marking the border of the A-stretch. This may be important when the recombinase measures the distance between the heptamer and the nonamer to satisfy the 12/23-bp spacer rule.

Animals↗
PubMed1994

K-ras codon 12 mutations in biliary tract tumors detected by polymerase chain reaction denaturing gradient gel electrophoresis.

BACKGROUND: Although the prevalence of K-ras codon 12 mutations in biliary tract (BT) tumors has been addressed in previous studies, the results have shown large discrepancies in mutation frequency. METHODS: K-ras codon 12 mutations were investigated by polymerase chain reaction (PCR)-denaturing gradient gel electrophoresis (DGGE), a sensitive method for detecting DNA base changes, in a large series of BT tumors. RESULTS: In A-549 cells, which are known to contain a G to A change at the first base of K-ras codon 12, the mutation could be detected by DGGE even after 1:16 dilution with normal DNA. Tumor samples were microdissected from paraffin embedded tissue sections to ensure the presence of the tumor cells. K-ras mutations were detected in 13 of 23 bile duct tumors (56.5%) and in 9 of 23 gallbladder tumors (39.1%) by DGGE. However, no mutations were detected in normal, hyperplastic, and dysplastic BT epithelium or in tumorlike lesions, such as adenomyomatous hyperplasia, cholesterol polyps, and cystitis glandularis proliferans. The samples exhibiting abnormalities on DGGE showed a base change at K-ras codon 12 when examined by oligonucleotide hybridization. CONCLUSIONS: K-ras codon 12 mutations are seen often in BT tumors, and a combination of microdissection and PCR-DGGE is an effective approach for their detection.

Adult↗
PubMed1994

DNA damage-inducible replication of the Escherichia coli chromosome is initiated at separable sites within the minimal oriC.

When Escherichia coli cells are subjected to genetic stress by exposure to agents or conditions that transiently block DNA replication, the mode of DNA replication is profoundly altered. One of the alterations is the induction of inducible stable DNA replication (iSDR) that does not require the initiator protein, DnaA, and occurs despite the presence of rifampin and chloramphenicol, which inhibit the initiation of usual chromosome replication at oriC. It has been demonstrated that iSDR starts primarily from both the oriC and terC regions of the chromosome. To precisely map the iSDR origin (oriM1) located in the oriC region, various oriC fragments were inserted into a plasmid vector derived from pSC101, and the copy number of these plasmid constructs was measured in the presence of rifampin and chloramphenicol after cells were induced for the SOS response by thymine starvation. The results indicated that there are at least two origins for iSDR within the minimal oriC; one (oriM1A) is located between the BamHI (coordinate +1) and the AvaII(155) sites, and the other (oriM1B) between the AvaII(155) and the HindIII(244) sites. Furthermore, a 263 bp fragment containing oriM1, which was placed at the att lambda site of the chromosome, was found to initiate chromosome replication in the presence of the drugs when cells were starved of thymine. Introduction of additional copies of oriM1 into a cell stimulated initiation of iSDR at oriM1 on the chromosome. The result supported the model that iSDR starts from D-loops created between oriM1 sequences and that the amount of D-loops determines the level of the iSDR activity.

Bacterial Proteins↗
PubMed1994

Protective effects of 2,3-dimercaptopropane-1-sulfonate on mercuric chloride-induced acute inhibition of enzymes from rat duodenal mucosa and kidney cortex.

Acute inhibitory effects of mercuric chloride on the activities of several enzymes from rat duodenal mucosa and kidney cortex and the protection provided by 2,3-dimercaptopropane-1-sulfonate (DMPS) were examined. Activities of carbonic anhydrase in homogenate, brush border and cytosol and of Mg(2+)-dependent, HCO3-stimulated ATPase in homogenate and brush border of duodenal mucosa and kidney cortex and activities of kidney microsomal Mg(2+)-dependent, Na(+)-K(+)-stimulated ATPase were all decreased following administration of HgCl2 (1-3 mg Hg/kg body weight s.c. once daily for 3 days). Decreases occurred generally in a dose-dependent manner and went back to near normal or normal levels by the combined administration of 20 and 30 mg DMPS/kg per day for 3 days. The concentration of serum urea nitrogen was increased about 8 times by the administration of 2 mg Hg/kg and restored to normal by the concomitant administration of 30 mg DMPS/kg. After the administration of 2 mg Hg/kg per day for 3 days, about half of the renal cortical proximal tubuli were necrotic. Administration of 30 mg DMPS/kg restored these changes to almost normal. The results suggest that DMPS is useful in mitigating acute Hg poisoning and that part of the protective effect of DMPS on enzyme damage induced by Hg poisoning may be due to its chelating action.

Animals↗
PubMed1994

Propagation of JC virus in human neuroblastoma cell line IMR-32.

JC virus (JCV), the causative agent of a human demyelinating disease, progressive multifocal leukoencephalopathy, has a very narrow host range. Cells permissive for infection by JCV have been essentially limited to primary human fetal glial cells, which are difficult to obtain and maintain. In pilot studies, it was found that JCV can multiply in an established cell line of human neuroblastoma. JCV strains Mad-1 and Tokyo-1 were inoculated, respectively, into two cell lines, IMR-32 (neuroblastoma) and A-172 (glioblastoma). Viral infection with cytopathic effect was observed only in IMR-32 cells, and the most efficient viral proliferation was obtained in cells cultured in medium containing 2% fetal calf serum (FCS). Both Mad-1 and Tokyo-1 strains propagated well, with the former being more efficient than the latter. Viral replication was confirmed by immunofluorescence, electron microscopy, and a hemagglutination assay. Sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis and Western blot analysis of the purified virus revealed the characteristic JCV protein profile. Thus, IMR-32 cells have been found to be permissive for JCV, which should provide a useful system for further studies of virus proliferation and viral tissue tropism.

Blotting, Western↗
PubMed1994

Frequent K-ras mutations and absence of p53 mutations in mucin-producing tumors of the pancreas.

Mucin-producing tumors of the pancreas (MPT) are characterized by the production of much mucin and a benign course after surgical treatment. We examined 16 cases of MPT and 20 cases of "common" pancreatic duct cell carcinomas (DCC) in regard to K-ras and p53 mutations. The mutations were detected by constant denaturant gel electrophoresis in combination with other techniques using PCR products amplified from the samples microdissected from the tissue sections. K-ras codon 12 mutations were identified in all MPT and in 95% of DCC. On the other hand, p53 mutations were found in four of 20 (20%) DCC, and p53 was immunocytochemically overexpressed in 3 of the 4 mutated cases. However, no p53 mutations and no p53 overexpression were identified in the 16 MPT. These results indicate that, although the K-ras codon 12 mutations may be almost essential for the development of both MPT and DCC, p53 mutations seemed to be involved mainly to the latters.

Adenocarcinoma, Mucinous↗
PubMed1994

Pressure- and parathyroid-hormone-dependent Ca2+ transport in rabbit connecting tubule: role of the stretch-activated nonselective cation channel.

To characterize the Ca2+ transport process across the apical membrane of the rabbit connecting tubule (CNT), we examined the effects of luminal pressure on parathyroid hormone (PTH)-dependent apical Ca2+ transport in this segment perfused in vitro. An increase of perfusion pressure (0.2 to 1.2 KPa) caused cytoplasmic free Ca2+ concentration ([Ca2+]i) to increase by 42 +/- 11 nM in Fura-2 loaded perfused CNT. The response was accentuated when 10 nM PTH was added to the bath (101 +/- 30 nM, n = 6). Addition of 0.1 mM chlorphenylthio-cAMP (CPT-cAMP) to the bath also augmented the [Ca2+]i response to pressure from 36 +/- 16 to 84 +/- 26 nM (n = 3). Under steady perfusion pressure at 1.2 KPa, PTH (10 nM) increased [Ca2+]i by 31 +/- 7 nM (n = 5), whereas it did only slightly by 6 +/- 2 nM (n = 12) at 0.2 KPa. The pressure-dependent increase of [Ca2+]i was abolished by removing luminal Ca2+ (n = 3), and was not affected by 0.1 and 10 microM nicardipine (n = 4) in the presence of 10 nM PTH. Cell-attached patch clamp studies on the apical membrane of everted CNT with pipettes filled with either 200 mM CaCl2 or 140 mM NaCl revealed channel activities with conductances of 42 +/- 2 pS (n = 4) or 173 +/- 7 pS (n = 5), respectively. An application of negative pressure (-4.9 KPa) to the patch pipette augmented its mean number of open channels (NPo) from 0.005 +/- 0.001 to 0.022 +/- 0.005 in the Ca(2+)-filled pipette, and was further accelerated to 0.085 +/- 0.014 (n = 3) by 0.1 mM CPT-cAMP. In the Na(+)-filled pipette, similar results were obtained (n = 3), and CPT-cAMP did not activate the stretch-activated channel in the absence of negative pressure (n = 3). These results suggest that a stretch-activated nonselective cation channel exists in the apical membrane of the CNT and that it is activated by PTH in the presence of hydrostatic pressure, allowing entry of Ca2+ transport from the apical membrane.

Animals↗