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Biomedical subjects

N Ogata

Publications and source records attributed to N Ogata.

At least 181 records · Page 10Linked to original sources
PubMed1992

Antioxidant effect on renal scarring following infection of mannose-sensitive-piliated bacteria.

Renal scars have been considered to occur in later stages of chronic pyelonephritis. In our experimental pyelonephritis model, bacteria which possessed mannose-sensitive (MS) pili on the surface promoted renal scarring following inoculation to the renal parenchyma. Polyethylene glycol-modified superoxide dismutase (PEG-SOD) and 2-O-octadecylascorbic acid (CV3611) significantly suppressed scarring when administered orally or parenterally during the early stage of kidney infection with MS-piliated bacteria. These findings suggest that the superoxide and other active oxygens play an important role in renal scarring following infection and that PEG-SOD and CV3611 may be agents capable of preventing renal scarring following bacterial pyelonephritis.

Administration, Oral↗
PubMed1992

Changes in major phospholipids of mitochondria during postischemic reperfusion in rat brain.

Major mitochondrial phospholipids were examined in rat brain after 30 minutes of reperfusion following 30- or 60-minute periods of ischemia to examine their changes and explore their relationship to mitochondrial dysfunction during postischemic reperfusion. The amount of phospholipids and the percentage of polyunsaturated fatty acid chains, which tended to decrease during 30 minutes of ischemia, recovered after reperfusion. However, after ischemia lasting for 60 minutes, these parameters did not recover but decreased further, suggesting progressive disruption of phospholipids by phospholipase A2 after reperfusion. These changes were particularly notable in cardiolipin, which is contained specifically in mitochondria. The changes were also closely associated with mitochondrial respiration and respiratory enzyme (cytochrome c oxidase and F0F1-adenosine triphosphatase) activities, which have been known to correlate with the amount of cardiolipin. These results suggest that phospholipid metabolism in mitochondrial membranes is an important factor bearing on the integrity of energy metabolism during postischemic reperfusion.

Adenosine Triphosphatases↗
PubMed1992

Suppression of intestinal smooth muscle contraction by phenolic compounds.

Wood creosote, a mixture of guaiacol, creosol, and other related phenolic compounds, suppresses the spontaneous longitudinal phasic contractions of an isolated rat ileal segment. Thirty-two phenolic compounds were screened for this activity to identify the active substances in wood creosote. Of the 32 compounds tested, 2,3,6-trimethylphenol, 2,4,6-trimethylphenol, and 4-ethylguaiacol were most effective and their respective IC50 values were 0.035, 0.037, and 0.043 mM. Guaiacol and creosol, the chief constituents of wood creosote, were moderately effective and their respective IC50 values were 0.18 and 0.13 mM. Other phenolic compounds in wood creosote also suppressed the ileal contraction although their IC50 values differed markedly from each other. These results suggest that practically all of its constituent phenolic compounds contribute to wood creosote's capacity to suppress ileal contraction.

Animals↗
PubMed1992

[Histological changes in the retinal pigment epithelium and Bruch's membrane in senescence accelerated mouse].

Senescence associated changes of the retinal pigmented epithelium (RPE) and Bruch's membrane were investigated in senescence accelerated mouse (SAM), which is an aging model mouse, by light and electron microscopy. The most characteristic changes in RPE were swelling of basal infoldings, extension of intercellular space and accumulation of lipofuscin granules. In Bruch's membrane, discontinuation of elastic layer and abnormal increase of fine fibrils in the outer collagenous layer were observed. The aging changes in SAM were severer in the posterior retina than in the peripheral one. Moreover, these changes were seen younger age than in those of the normal BALB/c mouse.

Aging↗
PubMed1991

Nucleotide sequence and mutation rate of the H strain of hepatitis C virus.

Patient H is an American patient who was infected with hepatitis C virus (HCV) in 1977. The patient became chronically infected and has remained so for the past 13 years. In this study, we compared the nucleotide and predicted amino acid sequences of the HCV genome obtained from plasma collected in 1977 with that collected in 1990. We find that the two HCV isolates differ at 123 of the 4923 (2.50%) nucleotides sequenced. We estimate that the mutation rate of the H strain of HCV is approximately 1.92 x 10(-3) base substitutions per genome site per year. The nucleotide changes were exclusively base substitutions and were unevenly distributed throughout the genome. A relatively high rate of change was observed in the region of the HCV genome that corresponds to the non-structural protein 1 gene region of flaviviruses, where 44 of 960 (4.6%) nucleotides were different. Within this region there was a 39-nucleotide domain in which 28.2% of the nucleotides differed between the two isolates. In contrast, relatively few nucleotide substitutions were observed in the 5' noncoding region, where only 2 of 276 (0.7%) nucleotides were different. Our results suggest that the mutation rate of the HCV genome is similar to that of other RNA viruses and that genes appear to be evolving at different rates within the virus genome.

Amino Acid Sequence↗
PubMed1991

[Effect of nizofenone on the symptomatic vasospasm after aneurysmal subarachnoid hemorrhage and its relationship to the levels of serum complements (CH50, C3 and C4)].

Serum complements (CH50, C3 and C4) after aneurysmal subarachnoid hemorrhage were measured in 42 patients over 2 to 3-week period. Nizofenone, an anti-vasospasmotic agent, was administered to 11 patients. In the nizofenone-treated group, 8 patients showed decreased serum C4 levels 5 days after the onset of subarachnoid hemorrhage, but among them, only 2 patients showed symptomatic vasospasm. Considering our previous data (majority of patients who showed decreased serum C4 levels presented with symptomatic vasospasm), these results suggest a favorable effect of nizofenone on the symptomatic vasospasm after aneurysmal subarachnoid hemorrhage.

Adult↗
PubMed1991

Significance of urinary endotoxin concentration in patients with urinary tract infection.

Endotoxin is a component of the outer membrane of gram-negative rods (GNR). Since GNR are responsible for the majority of urinary tract infection (UTI), we measured the concentration of endotoxin in urine using chromogenic endotoxin-specific assay and examined its diagnostic utility in patients with suspected UTI. In all 18 urine samples with an endotoxin concentration exceeding 350 pg/ml and 2 samples with 10-350 pg/ml of endotoxin concentration, GNR were detected at a count of 10(4) cfu/ml. Negative for endotoxin were 3 samples of culture positive for gram-positive cocci (GPC), 2 samples containing various bacterial contaminants and all 37 samples with no growth on culture. Two urine samples collected 5 h after antibiotic dosage showed negative culture for GNR but a significant concentration of endotoxin. In an in vitro experiment, a residual concentration of antibiotic in urine inhibited bacterial growth, leading to a false-negative culture. These results suggest that chromogenic endotoxin assay is a reliable method for diagnosing UTI caused by GNR and detecting false-negative culture of GNR.

Adult↗
PubMed1991

Neutrophil function in hyperosmotic NaCl is preserved by phosphoenol pyruvate.

Hyperosmolarity in the urinary tract inhibits the host defense against bacterial infection. NaCl contributes most to osmolarity in the renal medulla and urine. Therefore, we studied the effect of hyperosmolar NaCl on neutrophil function. When osmolarity was increased by NaCl, polymorphonuclear leukocytes (PMNL) became defective in phagocytosis, intracellular killing of bacteria, chemotactic activity, and superoxide production. This coincided with a decrease in the intracellular adenosine triphosphate (ATP) content of PMNL. Both the inhibition of superoxide production and the reduction in ATP content did not occur at 4 degrees C. By increasing ATP content, phosphoenol pyruvic acid (PEP) protected against the decrease in superoxide production. These results suggest that leukocyte function is inhibited by high concentrations of NaCl due to the activation of the Na(+)-K+ pump. PEP, an ATP precursor, can protect PMNL against osmotic stress by raising the intracellular concentration of ATP.

Adenosine Triphosphate↗
PubMed1991

Role of superoxide in renal scarring following infection by mannose-sensitive piliated bacteria.

The role of superoxide in scar formation following renal infection caused by mannose-sensitive (MS) piliated strains of bacteria was studied in the experimental pyelonephritis model using female Sprague-Dawley rats. The MS piliated strain stimulated renal scarring to a significantly greater extent than either the non-piliated or MR-piliated strain. Modulation of leukocytes by administering cyclophosphamide to induce neutropenia and colchicine to inhibit leukocyte migration was effective in preventing renal scarring. Treatment with superoxide dismutase during the early stage of infection was also effective in preventing scar formation. Finally, the production of superoxide by rat leukocytes was significantly larger following stimulation by MS piliated than either the non-piliated or MR piliated strains. These observations suggest that superoxide released from leukocytes plays a critical role in the development of renal scarring following a bacterial infection, especially by MS piliated strains.

Animals↗
PubMed1991

A simple and multi-purpose "concentration-clamp" method for rapid superfusion.

A simple method for the rapid exchange of the medium used for a variety of electrophysiological experiments including patch-clamp experiments on cultured cells is described. The advantages of this method over the conventional ones are that this solution exchange system has a very simple structure and thus is inexpensive and can be easily installed in already existing experimental setups. The method involves the use of a fine double-barrelled polyethylene needle placed near the cell or other isolated preparations under recording. Electromagnetic valves are used to switch the solutions in the polyethylene tubes which enable a rapid and localized application of test solutions as well as their rapid washout. The latency of solution exchange, as measured by a change in the holding current under voltage-clamp experiments was fairly rapid (about 120 ms). Neither was the recording interrupted nor the sealing resistance affected during repeated exposure to test solutions. This method is proving to be useful, particularly for electrophysiological and pharmacological studies on immovable cells such as those in culture.

Animals↗
PubMed1991

Primary culture of neurons derived from the adult mammalian brain.

A method is described for the isolation and culture of neurons in the adult mammalian brain. The cell could be maintained in primary culture for more than several weeks. Whereas the neurons freshly dissociated from the adult brain did not respond to any of the neurotransmitter substances applied, the neurons regained the ability to respond to a variety of neurotransmitters when cultured. The cultured neurons of the adult mammalian brain may be an excellent model for physiological as well as pharmacological investigations of the central nervous system.

Animals↗
PubMed1991

Degradation of mitochondrial phospholipids during experimental cerebral ischemia in rats.

Changes in content of brain mitochondrial phospholipids were examined in rats after 30 and 60 min of decapitation ischemia compared with controls, to explore the degradation of the mitochondrial membrane and its relation to dysfunction of mitochondria. Activities of respiratory functions and respiratory enzymes (cytochrome c oxidase; F0F1-ATPase) decreased significantly during ischemia. Considerable decreases in cardiolipin and phosphatidylinositol content were observed after 60 min, and other phospholipids showed similar but nonsignificant decreases in content. The amount of polyunsaturated fatty acids chains, such as arachidonic and docosahexaenoic acids, was reduced in each phospholipid, in some cases significantly, after 30 and 60 min of ischemia in time-dependent manners. Degradation of mitochondrial phospholipids during ischemia associated with the deterioration of mitochondrial respiratory functions suggested the significance of such changes in phospholipid content in disintegration of cellular energy metabolism during cerebral ischemia.

Animals↗
PubMed1991

Preoperative oral and postoperative parenteral antibiotic prophylaxis of wound infection in total cystectomy with ileal urinary diversion.

We describe an investigation of postoperative abdominal infectious complications and discuss two regimens for preoperative antibiotic bowel preparation in cases who underwent total cystectomy with ileal urinary diversion. Ten cases (28.6%) of 35 who had been operated developed abdominal infectious complications. Six showed abdominal wound infection, 2 showed intrapelvic abscess and 2 showed abdominal wound infection with intrapelvic abscess. Of the 19 strains of organisms isolated from the postoperative infections, 11 (57.9%) were anaerobic bacteria and the most commonly isolated bacteria was Bacteroides. A significantly lower incidence of postoperative infection was found in cases who had received tobramycin and vancomycin (0%) than in those who had received kanamycin alone (41.7%). These results indicate that anaerobic bacteria are the major contributors to postoperative infections following total cystectomy with ileal urinary diversion and that tobramycin-vancomycin prophylaxis greatly reduces the incidence of postoperative infections.

Abdomen↗
PubMed1991

Inhibition of chemiluminescent response of human polymorphonuclear leukocytes by hyperosmolality comparable to renal medulla and preservation by ofloxacin.

Hyperosmolality of the urine and renal medulla inhibits polymorphonuclear leukocyte (PMN) functions such as phagocytosis, intracellular killing and superoxide generation. The main factors of hyperosmolality in the urinary tract are urea and NaCl. We studied the chemiluminescent (CL) functions of PMNs in hypersomotic urea and NaCl solutions and the effects of ofloxacin, a new quinolone antimicrobial, for inhibiting the functions of PMNs subjected to hyperosmolality. When PMNs were incubated with hypersomotic urea and NaCl solutions, the CL response was significantly reduced. The reduced CL response was significantly preserved by supplementation with ofloxacin (OFLX). The CL response of PMNs may thus also be reduced in the urinary tract and OFLX may exert strong antimicrobial and preservative effects on PMN.

Culture Media↗
PubMed1991

[Pharmacology and physiological function of gamma-aminobutyric acid B type receptor].

Baclofen, a beta-chlorophenyl derivative of gamma-aminobutyric acid (GABA), depresses neuronal excitability in various parts of the central nervous system. The site of action for this drug had once been considered to be distinct from GABA recognition sites. In addition to the classical GABA recognition site (GABAA site), a new class of GABA receptor (GABAB site) has been characterized. GABAB sites are mainly present on nerve terminals and, when activated, result in diminished transmitter release, probably through a reduction in Ca2+ influx. Baclofen was shown to be a selective agonist for this novel GABAB recognition. Baclofen also directly hyperpolarizes the membrane of mammalian brain neurons, in addition to its presynaptic action. This postsynaptic action of baclofen was shown to result from an increase in K+ conductance when studied in hippocampal pyramidal neurons through postsynaptic GABAB receptors. Thus, the inhibitory neurotransmitter GABA activates two receptor subtypes that can be distinguished by their physiological and pharmacological properties. GABAA receptors mediate rapid alterations in the distribution of Cl- across the membrane. GABAA receptors are linked directly to an ion channel, thus contributing to the prompt inhibition of cellular excitability. On the contrary, the GABAB receptor does not contain an integral ion channel and is thus responsible for slower responses through receptor-G-protein-effector complexes. G-protein may be directly coupled to K+ or Ca2+ channels. In addition, G-protein may modulate a variety of regulatory proteins or second messengers, thus contributing to the slower alteration of cellular excitability or to the modulation of neurotransmitter release.

Animals↗