Search PubMed⌕ Search

Biomedical subjects

K Yasuda

Publications and source records attributed to K Yasuda.

At least 595 records · Page 33Linked to original sources
PubMed1995

Microscopic analysis of the elastic properties of nebulin in skeletal myofibrils.

The elastic properties of nebulin were studied by measuring the elasticity of single skeletal myofibrils, from which the portion of the thin filament located at the I band had been selectively removed by treatment with plasma gelsolin under rigor conditions. In this myofibril model, a portion of each nebulin molecule at the I band was expected to be free of actin filaments and exposed. The length of the exposed portion of the nebulin molecule was controlled by performing the gelsolin treatment at various sarcomere lengths. The relation between the passive tension and extension of the exposed portion of the nebulin showed a convex curve starting from a slack length, apparently in a fashion similar to that of wool. The slack sarcomere length shifted depending on the length of the exposed portion of the nebulin, however, the relation being represented by a single master curve. The elastic modulus of nebulin was estimated to be two to three orders of magnitude smaller than that of an actin filament. Based on these results, we conclude that nebulin attaches to an actin filament in a side-by-side fashion and that it does not significantly contribute to the elastic modulus of thin filaments. The relation between the passive tension and extension of connectin (titin) was obtained for a myofibril from which thin filaments had been completely removed with gelsolin under contracting conditions; this showed a concave curve, consistent with the previous results obtained in single fibers.

Actins↗
PubMed1995

Spinal cord protection during thoracoabdominal aortic aneurysm repair: results of selective reconstruction of the critical segmental arteries guided by evoked spinal cord potential monitoring.

PURPOSE: The purpose of this study is to evaluate the results of spinal cord protection based on selective reconstruction of the segmental arteries. METHODS: Twenty-one patients who underwent repair of aneurysms (nine descending thoracic and 12 thoracoabdominal: three type I, six type II, and three type III) were analyzed. Ten patients had postdissection aneurysms. Operative techniques consisted of evoked spinal cord potential (ESP-dsc) monitoring and femorofemoral bypass in all cases, segmental resection in 12, and mild systemic hypothermia in eight. Arteries critical for cord blood flow were selectively reconstructed; if ESP-dsc showed change after resection of an aortic segment, arteries originating from this segment were reconstructed. RESULTS: ESP-dsc change was observed in 12 patients. Arteries found to be critical were at the T8-L1 level in all but three cases. Selective reconstruction was performed in 10 of these 12 patients. ESP-dsc change could be reversed before reconstruction in four cases, three by control of back-bleeding critical arteries. Selective reconstruction resulted in return of ESP-dsc in seven other patients. Spinal cord injury occurred in five patients, two of whom did not undergo selective reconstruction. CONCLUSION: These results suggest that our current technique allows determination of critical arteries but does not completely prevent injury.

Adult↗
PubMed1995

Influence of a cigarette smoke extract on the hormonal regulation of platelet-activating factor acetylhydrolase in rats.

We evaluated the effects of estrogen, progestin, and cigarette smoke extract (CSE) on plasma platelet-activating factor (PAF) acetylhydrolase (AH; PAF-AH) activity in rats. The effects on rat tissues of an i.v. injection of PAF were studied as part of our investigation of the mechanisms involved in thrombotic episodes. Plasma PAF-AH activity in adult female rats (14 wk of age) treated with 17 alpha-ethynylestradiol (100 micrograms/kg, 5 days) was decreased by 70%. Medroxyprogesterone (50 mg/kg, 5 days) increased PAF-AH activity by 50%. CSE (0.5 cigarette/kg, 5 days) did not alter PAF-AH activity during the treatment. However, a combination of CSE and 17 alpha-ethynylestradiol decreased plasma PAF-AH activity by 90%. The decrease in PAF-AH activity was age-dependent. The effect of medroxyprogesterone on plasma PAF-AH activity was not influenced by CSE. When PAF (5-40 nmol/kg) was injected i.v. into untreated adult female rats, 9 of 16 animals died after a 20-nmol/kg dose of PAF. Macroscopic findings included hemorrhage, hyperemia, and congestion in the lungs and heart, and necrosis-like changes in the gastrointestinal tract. Microscopically, thrombi were observed in the lungs and heart. When PAF was administered to adult female rats pretreated with sex steroid hormones, the mortality of rats with low plasma PAF-AH activity caused by 17 alpha-ethynylestradiol was increased but that of rats with high PAF-AH activity caused by medroxyprogesterone was decreased. Thus, PAF and PAF-AH may play important roles in the thrombotic episodes known to occur in female smokers who use oral contraceptives.

1-Alkyl-2-acetylglycerophosphocholine Esterase↗
PubMed1995

Mapping of murine Th1 and Th2 helper T-cell epitopes on fimbriae from Porphyromonas gingivalis.

Th1- and Th2-derived cytokine production in response to synthetic peptides of the fimbrial subunit protein (fimbrilin) from Porphyromonas gingivalis strain 381 was assessed in spleen mononuclear cells (MNC) of BALB/c mice (H-2d haplotype) immunised with the fimbrial protein antigen and adjuvant GM-53 in Freund's incomplete adjuvant (FIA). Sixty-seven sequential overlapping 10-mer peptides covering the complete 337 amino-acids (AA) protein of P. gingivalis fimbrilin were synthesised. Stimulation of spleen MNC in vitro with these 10-mer peptides resulted in the production of murine interleukin-2 (IL-2), gamma-interferon (IFN-gamma), IL-4, IL-5 and IL-6. Peptides 13 (AA 61-70), 24 (AA 116-125), 31 (AA 151-160) and 64 (AA 316-325) markedly induced IL-2 production. In particular, peptide 24 (DPLKIKRVHA), which contained I-Ad, I-Ed and I-Ak binding motifs, was the most potent stimulator of IL-2, IFN-gamma, IL-4, IL-5 and IL-6 production. Spleen MNC from C3H/HeN mice (H-2k) followed by BALB/c mice (H-2d) immunised with peptide 24 were high responders to peptide 24 in terms of both IFN-gamma and IL-4 production, whereas A/J mice (H-2a) and C57BL/6 mice (H-2b) were very low responders, P. gingivalis fimbriae evoked higher delayed-type hypersensitivity (DTH) reactions in B10.D2 (H-2d) and B10.BR (H-2k) mice followed by C57BL/10 (B10, H-2b) and B10.A (H-2a) and in guinea-pigs immunised with the fimbriae and GM-53 in FIA.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1995

Responses of plasma adrenocortical steroids to low dose ACTH in normal subjects.

OBJECTIVE: The standard ACTH test in clinical use employs a pharmacological dose of ACTH which assesses the maximum secretory capacity of the adrenal cortex. We have investigated the responses of plasma adrenocortical steroids including cortisol, aldosterone and dehydroepiandrosterone (DHEA) to physiological doses of ACTH (ACTH 1-24, tetracosactide, Cortrosyn) and determined the minimal dose which induces a response equivalent to that induced by a pharmacological dose of ACTH. DESIGN: Rapid ACTH tests at various physiological (0-1, 0.5, 1 and 5 micrograms) and standard pharmacological (250 micrograms) intravenous doses. SUBJECTS: Seven healthy normal volunteers. MEASUREMENTS: Plasma cortisol, aldosterone and DHEA were measured. Peak value and the increment from basal value were used as indices of responses. RESULTS: Each steroid responded to physiological doses of ACTH in a dose dependent manner. The minimum dose inducing an equivalent response to 250 micrograms ACTH was 0.5 micrograms for peak and incremental values in cortisol and DHEA, while that for aldosterone was 0.1 microgram. The time to peak for each steroid was delayed as the dose increased. Plasma aldosterone and DHEA peaked significantly earlier than plasma cortisol in 1-5 micrograms and 0.5-5-micrograms ACTH tests, respectively. CONCLUSIONS: These results suggest that the sensitivity of secretion to physiological doses of ACTH in descending order is aldosterone > DHEA = cortisol. When peak and incremental values are used, sufficient doses of ACTH are 0.1 microgram for plasma aldosterone and 0.5 microgram for plasma cortisol and DHEA in the rapid ACTH test.

Adrenal Cortex Hormones↗
PubMed1995

Immunochemical characterisation and epitope mapping of a novel fimbrial protein (Pg-II fimbria) of Porphyromonas gingivalis.

Mouse monoclonal antibody (mAb) Pgf-II specific for a 72-kDa major cell-surface protein (72K-CSP) derived from Porphyromonas gingivalis OMZ 409 was prepared. Immunoblotting analysis revealed that mAb Pgf-II reacted with 72K-CSP but not with 41-kDa fimbrial subunit protein (41K-fimbrilin) derived from P. gingivalis 381. Electron microscopic observation revealed that P. gingivalis OMZ 409 possessed peritrichous, thin fimbriae on their surface. Immunogold electron microscopy also demonstrated that mAb Pgf-II bound to the 72K-CSP examined with the gold particles arranged along the fibril array originating from the cell surface of the bacteria. These findings suggested that P. gingivalis 72K-CSP was identifiable as another fimbriae (termed Pg-II fimbriae) different from the fimbriae (termed Pg-I fimbriae) composed of a 41K-fimbrilin. Using multipin peptide synthesis technology, 102 sequential overlapping peptides covering the entire 514 amino-acid stretch of Pg-II fimbriae were synthesised. Seven immunodominant regions within Pg-II fimbrial protein molecule, which definitely reacted with the serum of patients with periodontal diseases, were detected.

Adhesins, Bacterial↗
PubMed1995

Molecular diversity and functional characterization of voltage-dependent calcium channels (CACN4) expressed in pancreatic beta-cells.

Dihydropyridine-sensitive voltage-dependent calcium channels (VDCC) play a crucial role in insulin secretion. We recently have cloned a human alpha 1-subunit of the VDCC expressed in pancreatic beta-cells, designated CACN4. In this study we have isolated complementary DNAs encoding two forms of rat CACN4 (rCACN4A and rCACN4B) from a rat insulinoma RINm5F complementary DNA library. Rat CACN4A is a protein of 2203 amino acids and is the rat homolog of human CACN4, whereas rCACN4B lacks 535 amino acids in the carboxyl-terminal region, probably due to alternative splicing. We have found two additional variations, one in the intracellular loop between repeats I and II and the other in the extracellular region between the third and fourth segments of repeat IV. Reverse transcriptase-polymerase chain reaction analysis of rat pancreatic islet messenger RNA reveals that these variants are present in pancreatic islets. In addition, whole-cell voltage-clamp recordings of Chinese hamster ovary cells stably expressing the alpha 1-subunit (rCACN4A or rCACN4B) with or without the calcium channel beta 2-subunit show that coexpression of rCACN4A with the beta 2-subunit or rCACN4B with the beta 2-subunit elicits L-type VDCC currents, whereas expression of the alpha 1-subunit alone does not, indicating that CACN4 can associate functionally with the beta 2-subunit and that the beta-subunit is essential for functional expression of CACN4. These results suggest that there are various subtypes of CACN4 expressed in pancreatic beta-cells, and that both rCACN4A and rCACN4B can function as VDCC. Furthermore, the present study suggests that the expression of the beta-subunit as well as the alpha 1-subunit may participate in the regulation of insulin secretion.

Amino Acid Sequence↗
PubMed1995

Studies on agents with vasodilator and beta-blocking activities. III. Synthesis and activity of optical isomers of TZC-1370.

Optical isomers of TZC-1370 (1) were prepared from (R)- and (S)-1-(2-chlorophenoxy)-2,3-epoxypropane. When given intravenously to anesthetized rats, the (S)-isomer was about 40 times more potent in terms of beta-blocking activity than the (R)-isomer, while their hypotensive activities were equipotent with that of the racemic compound, TZC-1370.

Adrenergic beta-Antagonists↗
PubMed1995

Studies on agents with vasodilator and beta-blocking activities. II.

A series of phenoxypropanolamines having a hydrazinopyridazinyl moiety was synthesized. Their hypotensive and beta-blocking activities were evaluated after intravenous administration of the compounds to anesthetized rats. Some of them exhibited both activities. In particular, compound 20k is a candidate for clinical use due to its hypotensive activity, equal to that of hydralazine, and its beta-blocking activity, 2.7-fold more potent than that of propranolol.

Adrenergic beta-Antagonists↗
PubMed1995

Changes of hepatic microsomal oxidative drug metabolizing enzymes in chronic renal failure (CRF) rats by partial nephrectomy.

Male SD rats, 7-weeks-old, were used to investigate the changes in the hepatic drug metabolizing system of chronic renal failure (CRF) model rats. Partial nephrectomy (5/6) was performed in a two-stage surgical procedure. After nephrectomy, the rats were housed under regular conditions at least 21 days. After confirming the CRF states, trimethadione (TMO, 100 mg/kg, i.p.) was administered for evaluation of the hepatic drug metabolizing capacity; the ratio of dimethadione (DMO: the only metabolite of TMO) to TMO (DMO/TMO) in the serum and the dialysate from the blood microdialysis method were ascertained. The hepatic drug metabolizing enzyme contents and activities were also determined. In the CRF rats, the DMO/TMO ratios decreased significantly; total cytochrome P450 (CYP) contents, aminopyrine N-demethylase activity and delta-aminolevulinic acid synthetase activity also decreased significantly in the CRF rats. The extent of the alterations of these enzyme contents and activities correlated well with the severity of the CRF states evaluated by the serum blood urea nitrogen and creatinine concentrations. With Western blot analysis, the levels of CYP2C6, CYP2C11 and CYP3A2 decreased considerably in the CRF rats. These results suggest that CRF states induce not only a reduction of renal function but also an alteration of hepatic metabolism.

Animals↗
PubMed1995

Systemic oxygen delivery and consumption in dogs with heartworm disease.

To investigate systemic oxygen (O2) transport, we calculated the oxygen delivery index (Do2I), oxygen consumption index (Vo2I) and oxygen extraction ratio (ER) in dogs with heartworm (HW) disease. The Do2I was 770 +/- 331 ml/min/kg in dogs mildly affected with pulmonary HW disease showing respiratory signs, mild anemia and mild cardiac insufficiency (n = 34); 238 +/- 155 ml/min/kg in dogs with ascitic pulmonary HW disease (n = 7); and 577 +/- 320 ml/min/kg in dogs with caval syndrome (CS) which survived (n = 15) or died (n = 7) after surgical HW removal. The Do2I was lower (P < 0.01) in all HW-infected groups, especially in ascites and CS-non-surviving dogs, than in HW-free dogs (n = 11, 1041 +/- 264 ml/min/kg). The Vo2I was higher in some mildly affected dogs (161 +/- 88 ml/min/kg), and lower (P < 0.01) in ascitic dogs (45 +/- 53 ml/min/kg) than in HW-free dogs (123 +/- 44 ml/min/kg). The ER was higher (P < 0.01) in all HW-infected groups than in HW-free dogs. The Do2I correlated significantly with Vo2I (r = 0.84, P < 0.01), and the Vo2I correlated significantly with ER (r = 0.48, P < 0.01). The Do2I correlated significantly with arterial O2 tension (r = 0.33), serum LDH (r = -0.46) and CK (r = -0.46) activities, serum urea nitrogen (UN, r = -0.32) and lactic acid (LA, r = -0.39) concentrations and cardiac index (r = 0.64).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

Daily excretion levels of an unidentified ketosteroid in the urine of patients with Cushing's syndrome and healthy subjects measured by a new method.

We developed a new method for measuring an unidentified ketosteroid glucuronide (US-G) detected by the method of Iwata et al. for measuring 17-ketosteroid glucuronides by reversed phase HPLC on a Capcell-Pak C8 column with three kinds of mobile phase solutions (Iwata method; Clin Chem 35: 795-799, 1989). The Iwata method inadequately separated US-G and two hydroxy 17-ketosteroides, 11 beta-hydroxyetiocholanolone and 11 beta-hydroxyandrosterone, and it exhibits insufficient sensitivity for measuring traces of US-G in the urine of healthy subjects. We solved these problems by developing a new method which measures US-G in urine, as a free type by hydrolyzing the glucuronide type enzymatically, by normal phase HPLC on a Capcell-Pak Silica column with one kind of mobile phase solution. By this method, the levels of US excreted as a glucuronide in the urine of healthy subjects and of patients with Cushing's syndrome were determined as proportions of the levels of 11 beta-hydroxyandrosterone. The average daily urinary excretion of US was 971 micrograms (125-4,995 micrograms) in patients with Cushing's syndrome (n = 22: two males and 20 females aged 26 to 65 years), and 34 micrograms (0-141 micrograms) in healthy subjects (n = 63: 49 males, and 14 females aged 21 to 54 years), and the differences were clearly significant. However, there were no differences between the urinary US levels of patients with pituitary adenoma and patients with adrenal adenoma. Furthermore, no US was detected in the urine of patients with aldosteronism (two males and eight females aged 34 to 61 years).(ABSTRACT TRUNCATED AT 250 WORDS)

17-Ketosteroids↗
PubMed1995

Inhibition of aldosterone turn-off phenomenon following chronic adrenocorticotropin treatment with in vivo administration of antiglucocorticoid and antioxidants in rats.

Chronic adrenocorticotropin (ACTH) treatment in rats leads to a fall in aldosterone secretion (aldosterone turn-off or "aldosterone escape" phenomenon) with a concomitant rise in corticosterone. To elucidate whether ACTH-induced aldosterone suppression is mediated by steroid type II receptor or related to a free-radical effect by over-synthesized corticosterone, we examined the effects of a glucocorticoid antagonist, RU486, and antioxidants dimethyl sulfoxide (DMSO) and vitamin E, on the aldosterone turn-off phenomenon in rats. Each rat received daily for 5 days a different dose of ACTH-Z (5, 10, 20 or 40 micrograms/100 g body weight) 1 mg RU486/100 g body weight, 100 microliters (1.3 mmol) DMSO/100 g body weight or 2 mg vitamin E/100 g body weight with subcutaneous injection. Plasma steroid levels and in vitro release of steroids from the adrenal capsule were measured. The ACTH-Z treatment caused a dose-dependent increase in corticosterone and a decrease in aldosterone in both plasma and adrenal capsule experiments, as well as an increase in adrenal weights. For the following study 5 micrograms/100 g body weight of ACTH-Z was used. Administration of RU486 alone caused no change in plasma aldosterone level compared to controls, even though the steroid type II receptor was blocked, as evidenced by significant increases in plasma ACTH and corticosterone levels. Concomitant administration of RU486 and ACTH-Z increased both plasma corticosterone and aldosterone levels (p < 0.01) but decreased adrenal capsule corticosterone production (p < 0.05) compared to the rats treated with ACTH-Z alone.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenal Glands↗
PubMed1995

The distribution of afferent neurons in the trigeminal mesencephalic nucleus and the central projection of afferent fibers of the mylohyoid nerve in the rat.

Horseradish peroxidase conjugated to wheatgerm agglutinin (HRP:WGA) was injected into the proximal cut ends of three branches of the mylohyoid nerve in rats: the branch to the mylohyoid muscle (BrMh), the branch to the anterior belly of the digastricus muscle (BrDg), and the cutaneous branch (BrCu). HRP-labeled cells were detected in the ipsilateral caudal portion of the trigeminal mesencephalic nucleus (Vmes) and the ipsilateral ventromedial division of the trigeminal motor nucleus, except when HRP:WGA was applied to the BrCu. Morphologically, all labeled Vmes cells were of the pseudounipolar type. Projections of the primary afferents of the BrMh were observed in the ipsilateral trigeminal nucleus caudalis, the upper cervical dorsal horns of laminae I-III, and the dorsolateral recticular formation (Rf), whereas the primary afferents of the BrDg terminated in the ipsilateral trigeminal nucleus principalis and Rf. These observations suggest that the role of the afferent inputs of the mylohyoid muscle differs from that of those of the anterior belly of the digastricus muscle in terms of several functions associated with jaw-closing and infrahyoid muscles.

Afferent Pathways↗
PubMed1995

Abnormal behavior in adiabatic calorimetry of set dental stone.

Dehydration in set dental stone was studied by employing specific heat measurements. Dehydration proceeds in two steps in air. In the case of bulk samples, especially those made with a lower water-powder ratio, three endothermic reaction stages are observed; a reaction of the dihydrate to the hemihydrate is apparently separated in two, one of which is not inherent. It is thought that the occurrence of a new peak is due to the difficulty for the dehydrated water to escape, depending on the porosity of the set stone.

Calcium Sulfate↗