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Biomedical subjects

K Omata

Publications and source records attributed to K Omata.

At least 73 records · Page 4Linked to original sources
PubMed1993

A case of secondary aldosteronism similar to Bartter's syndrome with no abnormality in renal chloride reabsorption.

We had a 20-year-old male patient of secondary aldosteronism similar to Bartter's syndrome, which had proved to be evident after the remission of nephrotic syndrome. In the patient, hypokalemic alkalosis and hyperreninemic hyperaldosteronemia were observed, although the blood pressure was normal. Hyperplasia of juxtaglomerular cells was observed and no abnormalities indicating either glomerulonephritis or renal artery stenosis were found; the pressor response to intravenously infused angiotensin (ang) II was markedly decreased; urinary prostaglandin (PG) E2, kallikrein and kinin excretion were elevated. The inhibition of PG synthesis with indomethacin decreased renal PG production and partially corrected both hypokalemia and pressor responsiveness to ang II. Thus, this case is considered to be a case of Bartter's syndrome. Contrary to the previously reported observations, the effective fractional chloride reabsorption rate in the renal distal tubules was normal (> 80%) and not changed by PG inhibition. Plasma atrial natriuretic peptide level was normal. An interaction between renin-angiotensin and PG systems appears to play a prior role in this case. To explain the pathophysiology, we have hypothesized an abnormal function of ang II receptor signal transduction which excessively stimulates PLA2, resulting in overproduction of PG synthesis in tissues.

Adult↗
PubMed1993

Urinary active kallikrein excretion and diabetic renal impairments in streptozotocin-treated rats.

To assess possible roles of the renal kallikrein-kinin system in the development of renal impairments in diabetes mellitus, we determined daily excretion of urinary total and active kallikrein in uninephrectomized Wistar-Kyoto rats made diabetic by streptozotocin (45 mg/kg) as a bolus injection. We also evaluated the effect of captopril (50 mg/kg/day) administered orally on the development of diabetic renal impairments in the streptozotocin-treated rats. Active kallikrein was determined by its kininogenase activity, and generated kinins were radioimmunologically measured. Total kallikrein was also determined by measuring kininogenase activity after inactive kallikrein had been activated with trypsin (200 micrograms/ml). Urinary active kallikrein excretion was significantly reduced in streptozotocin-treated rats whereas urinary total kallikrein excretion was unchanged, resulting in the decreased ratio of active to total kallikrein compared to that in the controls. These reductions were preceded by the increased excretion of urine protein measured as an index of renal impairments. The administration of captopril for 12 weeks attenuated the development of diabetic renal impairments evaluated by urine protein excretion in streptozotocin-treated rats, although it did not induce significant changes in urinary total and active kallikrein excretion, and the ratio of active to total kallikrein. Thus the results of this study indicate that the renal kallikrein-kinin system might not play major roles in the development of diabetic renal impairments in the rat, although the pathophysiological relevance of impaired activation of renal kallikrein system to the development of diabetic renal impairments remains to be determined. In addition, they suggest that the renoprotective effects of captopril may be independent of the activation of renal kallikrein system in streptozotocin-treated rats.

Animals↗
PubMed1993

[UV-microspectrophotometric and flow cytometric analysis of the same samples using DAPI/HP staining].

A simple one-step double staining with DAPI and hematoporphyrin (HP) was used for UV-microspectrophotometric (UV-MSPM) and flow cytometry (FCM) analysis of the same samples. The specimens analyzed included fresh biopsy and/or surgical materials, trimmed 50 microns-thick paraffin sections and smears (with the latter not available for FCM). We provided the special technology for preserving the cytoplasm as far as possible to permit measurement of cell size and N/C ratio. DAPI indicates DNA content under 365 nm and HP of total protein content under 670 nm UV-MSPM. The DAPI can measure the nuclear size and the latter the cell size. DAPI/HP staining yielded much more accurate measurements than staining with FITC and PI. The use of both MSPM and FCM with cell sorting on the same samples is very helpful in cytology and histopathology for evaluating and differentiating borderline lesions and grade of malignancy, as well as oncostatic effectivity. Our goal is to combine this technology with the automated cytologic screening system CYBEST, which was developed by Tanaka et al, based on a morphometric device.

Adenocarcinoma↗
PubMed1993

[The effects of intrarenal infusion of recombinant human erythropoietin on renal hemodynamics and renal function in anesthesized rabbits].

To determine whether recombinant human erythropoietin (rHuEPO) has direct effect on mean arterial pressure or renal function, rHuEPO was infused intrarenally at a rate of 100 U min-1 for 30 min in anesthetized rabbits without renal failure. Intrarenal infusion of rHuEPO resulted in no change in mean arterial pressure, renal blood flow, or renal vascular resistance as compared with vehicle control. rHuEPO also produced no significant change in glomerular filtration rate, filtration fraction, or arterial hematocrit. However, urine volume, urinary excretion of sodium and potassium, and fractional sodium excretion were significantly reduced by intrarenal infusion of rHuEPO. These observations demonstrate that rHuEPO has no direct effects on mean arterial pressure or renal hemodynamics, whereas rHuEPO stimulates net tubular sodium reabsorption possibly by direct tubular action, and reduces urine volume and urinary excretion of sodium and potassium in anesthetized rabbits without renal failure.

Anesthesia, Intravenous↗
PubMed1992

Cloning and characterization of the cDNA encoding a novel brain-specific 14-kDa protein.

A new acidic protein with a molecular weight of 14,000 was purified from rat brain, in which it was specifically expressed, and partially sequenced by protein sequencing. On the basis of results obtained from the amino acid sequences, mixed oligonucleotides were synthesized and used as probes to clone a cDNA from a rat brain cDNA library. The cloned cDNA provided the full-length sequence of the 14-kDa protein. Northern blot hybridization using total RNA from several tissues of the rat provided evidence that the 14-kDa protein was expressed specifically in rat brain. Transfection of this cDNA into mammalian cells resulted in expression of the 14-kDa protein. The amino acid sequence predicted from the cDNA of the rat brain 14-kDa protein contained 137 amino acid residues. A hydropathy profile revealed a hydrophobic domain (amino acids 60-80) flanked by highly hydrophilic stretches on both sides. Whereas the N-terminal region of the 14-kDa protein contained four repeating motifs, EKTKEGV, the C-terminal domain was rich in glutamic acid and proline. A computer search of the amino acid sequence of the 14-kDa protein indicated no homology to any other protein reported so far.

Amino Acid Sequence↗
PubMed1992

Age-related changes in renal cytochrome P-450 arachidonic acid metabolism in spontaneously hypertensive rats.

We recently demonstrated that renal synthesis of cytochrome P-450-dependent arachidonic acid (AA) metabolites is increased in spontaneously hypertensive rats (SHR) during the rapid elevation of blood pressure. In this study, the chemical identity of these metabolites is described, and the structural analysis together with differential susceptibility to antibodies suggested that they are derived from at least two different cytochrome P-450 isozymes: 1) the epoxygenase that metabolizes AA mainly to 11,12-epoxyeicosatrienoic acid (EET), which is further hydrolyzed to 11,12-dihydroxyeicosatrienoic acid (DHT) and 2) omega/omega-1 hydroxylase(s) that generate the 20-hydroxyeicosatetraenoic acid (HETE) and 19-HETE, respectively. Their production and release from the isolated kidney was activated by arginine vasopressin and inhibited by cytochrome P-450 enzyme inhibitors. The formation of these metabolites in SHR or WKY cortical microsomes was age dependent. The production rates of EET, DHT, and 19-HETE increased from fetal to 9 wk of age by 3-, 6- and 4-fold, respectively, whereas that of 20-HETE increased by 27-fold. The omega/omega-1 hydroxylase activities were significantly higher in SHR, whereas epoxygenase activity (sum of EET and DHT production) demonstrated no differences between the two strains at any age group tested, although the amount of EET vs. DHT in a given age was significantly different. Since these metabolites have a wide and contrasting spectrum of biological and renal effects (vasodilation and vasoconstriction, inhibition and stimulation of Na(+)-K(+)-ATPase), their relative production rates at a given age may influence not only renal hemodynamics and salt and water balance but also pro- and antihypertensive mechanisms in SHR.

8,11,14-Eicosatrienoic Acid↗
PubMed1992

Renal cytochrome P-450-arachidonic acid metabolism: localization and hormonal regulation in SHR.

Epoxygenase and omega- and omega-1-hydroxylases are the major cytochrome P-450-arachidonate (P-450-AA) metabolizing enzymes in renal tissues. We measured P-450-AA metabolism in single nephron segments and determined the tubular localization of this activity in spontaneously hypertensive rats (SHR) and Wistar-Kyoto rats (WKY). Formation of 20-hydroxyeicosatetraenoic acid (20-HETE), the product of AA omega-hydroxylase was specifically localized in the entire proximal tubules (S1, S2, and S3 segments), whereas formation of 19-HETE, the product of omega-1-hydroxylase and epoxyeicosatrienoic acids (EETs), products of AA epoxygenase, was demonstrable throughout the tubule. Although distribution patterns were similar in SHR and WKY, formation of 19- and 20-HETE in the proximal tubules was higher in SHR, whereas the formation of EETs was not different between the two strains. In the proximal tubules, angiotensin II (ANG II) significantly stimulated epoxygenase activity (EETs formation), whereas parathyroid hormone (PTH) and epidermal growth factor (EGF) had no effect on epoxygenase but significantly stimulated omega-hydroxylase activity (20-HETE formation). Because P-450-AA metabolites have a wide and contrasting spectrum of biological and renal effects, from vasodilation to vasoconstriction and from inhibition to stimulation of Na(+)-K(+)-adenosinetriphosphatase, their localization to the specific nephron segments and differential stimulation of their formation by ANG II, PTH, and EGF may contribute not only to renal hemodynamics and blood pressure regulation but also to the regulation of renal sodium and water balance.

Angiotensin II↗
PubMed1992

Roles of renal cytochrome P450-dependent arachidonic acid metabolites in hypertension.

Cytochrome P450 represents the third metabolic pathway of arachidonic acid giving rise to several biologically active compounds, such as 19-HETE, 20-HETE and EETs and their corresponding DHETs. The kidney is the rich source of these metabolites which have some important biologic actions within the kidney. These metabolites have a wide and contrasting spectrum of biological and renal effects, from vasodilation to vasoconstriction and from inhibition to stimulation of Na-K-ATPase, their relative production rates may influence not only renal hemodynamics but also pro- and anti-hypertensive mechanisms of hypertension. There is increasing evidence that the abnormality of these metabolites in animal models of hypertension. However, sufficient evidence of the physiological and pathophysiological roles of hypertension in man is still lacking.

Animals↗
PubMed1992

The effects of intrarenal infusion of recombinant human erythropoietin on mean arterial pressure and renal hemodynamics in anesthetized rabbits.

The effects of recombinant human erythropoietin (rHuEPO) on mean arterial pressure (MAP) and renal hemodynamics were studied in anesthetized rabbits without renal failure. Intrarenal infusion of rHuEPO at a rate of 100 U/min for 30 min resulted in no change in MAP, renal blood flow, or renal vascular resistance. rHuEPO also produced no significant change in glomerular filtration rate filtration fraction, or arterial hematocrit. These results demonstrate that rHuEPO has no direct effects on MAP or renal hemodynamics in anesthetized rabbits without renal failure.

Anesthesia↗
PubMed1991

Detection of 20-hydroxyeicosatetraenoic acid in rat urine.

20-Hydroxyeicosatetraenoic acid (20-HETE), an arachidonate metabolite of the cytochrome P450 omega hydroxylase, was detected in rat urine by gas chromatography-mass spectrometric techniques. The concentration of 20-HETE in urine from 7-week-old hypertensive and normotensive rats was 2.1 and 1.3 nM, respectively. This is the first demonstration of 20-HETE urinary excretion and thus calls attention to the possibility that 20-HETE participates in the regulation of renal function via its effect on vascular tone and ion transport processes.

Animals↗
PubMed1991

Effect of phosphorylation of calmodulin on calcium binding affinity as estimated by terbium fluorescence.

The effect of phosphorylation of calmodulin by casein kinase 2 on the calcium binding of the former was studied by measurement of terbium fluorescence. The binding of Tb3+ to calmodulin was followed by an increase in Tb3+ fluorescence at 545 nm. The terbium fluorescence of phosphorylated calmodulin increased at a lower concentration of Tb3+ than that of non-phosphorylated calmodulin, indicating that Tb3+ binding affinity of calmodulin was increased by phosphorylation. Our results suggest that the interaction between calcium and binding domain becomes stronger by phosphorylation.

Adenosine Triphosphate↗
PubMed1990

Amino acid sequence and disulfide bridges of an antifungal protein isolated from Aspergillus giganteus.

A very basic secreted protein which displays antifungal activity was isolated from the medium of the mold Aspergillus giganteus. The protein consists of 51 amino acid residues whose sequence was determined as Ala-Thr-Tyr-Asn-Gly-Lys-Cys-Tyr-Lys-Lys-Asp-Asn- Ile-Cys-Lys-Tyr-Lys-Ala-Gln-Ser-Gly-Lys-Thr-Ala-Ile-Cys-Lys-Cys-Tyr-Val- Lys- Lys-Cys-Pro-Arg-Asp-Gly-Ala-Lys-Cys-Glu-Phe-Asp-Ser-Tyr-Lys-Gly-Lys-Cys- Tyr-Cys . Disulfide bonds were formed between Cys7-Cys33, Cys14-Cys40, Cys26-Cys28 and Cys49-Cys51. These results suggest that the antifungal protein forms a loop structure and is similar to phospholipase A2.

Amino Acid Sequence↗
PubMed1990

Behavior and body weight changes under intermittent exposure to cold in C57BL/6J mice.

This experiment examined effects of the intermittent exposure to cold. C57BL/6J mice were exposed to cold (4-5 degrees C) for six hours in light (L-cold group) or dark (D-cold group) period and their wheel-running and drinking activities, daily amounts of food and water intake, and body weight were analyzed. Wheel running and drinking decreased during cold exposure, while they increased in postcold period. These behavioral changes were more clearly found in the D-cold group. Body weight of the D-cold group was kept constant for all days of cold exposure, while that of the L-cold group tended to increase. These results are discussed from the view points of adaptive significance of postcold behaviors and the relationship between behavioral and physiological adaptations.

Animals↗
PubMed1990

Chronic effects of synthetic endothelin on blood pressure and sodium excretion in rats.

Continuous infusion of endothelin at a rate of 60 micrograms/kg/day into the jugular vein of rats via osmotic minipumps induced a significant increase in systolic blood pressure, but did not induce any significant changes in urine volume and urinary sodium excretion, compared to those in vehicle-infused rats. When 6 mg/kg/day of benidipine, a newly developed calcium channel blocker, was administered simultaneously with 60 micrograms/kg/day of endothelin, the systolic blood pressure of conscious rats rose on Day 1 to only 137.0 +/- 2.4 mm Hg (P less than .05) compared to the rise to 163.8 +/- 4.7 mm Hg when endothelin alone was infused. The antihypertensive effect of benidipine was sustained. The present results suggest that endothelin can act as a circulating hormone. In addition, they clearly demonstrate that the calcium channel blocker attenuates the elevation of blood pressure induced by endothelin.

Animals↗
PubMed1990

Role of bradykinin in the regulation of blood pressure and renal blood flow in DOCA-salt hypertensive rats.

We examined the role of bradykinin in the onset and/or the maintenance of blood pressure and renal blood flow in deoxycorticosterone acetate (DOCA)-salt hypertensive rats by using a competitive antagonist of bradykinin [Arg-Pro-Hyp-Gly-Thi-Ser-Dphe-Thi-Arg; Hyp, L-4-hydroxyproline; Thi, beta-(2-theinyl-L-alanine)]. The intravenous injection of the bradykinin antagonist (25, 50 and 100 micrograms) produced an increase in mean arterial pressure in all rats treated with tap water, 1% NaCl and DOCA + 1% NaCl. However, the magnitude of the increase in mean arterial pressure was significantly lower in the DOCA-hypertensive rats than in the two groups of rats drinking tap water and 1% NaCl after 4 and 6 weeks, but there was no significant difference after 2 weeks. The bradykinin antagonist induced a decrease in renal blood flow in all rats. However, the extent of the fall in renal blood flow was reduced in the DOCA-hypertensive rats compared with the control rats drinking tap water. These results suggest that endogenous bradykinin is depressed in the established phase of hypertension in DOCA-hypertensive rats. It is also suggested that endogenous bradykinin may counteract the elevation of vascular resistance in the early stages of this model.

Animals↗
PubMed1990

Purification and characterization of a novel brain-specific 14-kDa protein.

A new acidic protein specifically present in the brain was purified to homogeneity from bovine brain. The apparent molecular mass was estimated to be 14 kDa by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and 57 kDa by gel filtration, a finding suggesting that it exists as a tetramer under physiological conditions. The protein had a high content of Glu and Pro, and its pI was 4.3. The first six amino acid residues of the protein were Met-Asp-Val-Phe-Met-Lys, and the amino terminal was blocked. The distribution of the protein examined by Ouchterlony gel immunodiffusion indicates that it is present specifically in brain, including rat, human, and bovine, but could not be detected in 10 other rat tissues examined. The protein was absent in Purkinje cell bodies, as examined by electron microscopic immunocytochemistry, but was present in nerve terminals that make synapse-like contacts with Purkinje cells and in neurons with dark granules in the globus pallidus of the rat.

Amino Acid Sequence↗