Biomedical subjects

Yukio Ikeda

Publications and source records attributed to Yukio Ikeda.

44 records · Page 3Linked to original sources

PubMed2002

Biphasic vasodilator action of troglitazone on the renal microcirculation.

Recent studies have demonstrated that thiazolidinediones, novel antidiabetic compounds that improve the insulin sensitivity, lower BP and decrease urinary protein excretion. However, neither the target vasculature nor the underlying mechanism for their actions is well understood. In this study, the action of troglitazone (Tro), a thiazolidinedione compound, on the glomerular afferent (Af-Arts) and efferent (Ef-Arts) arterioles, crucial vascular segments to the control of glomerular hemodynamics, were directly examined. Rabbit Af-Arts or Ef-Arts were microdissected from the superficial cortex and perfused at constant pressure. Increasing doses of Tro (10(-8) to 10(-5) M) were added to both the bath and lumen of preconstricted arterioles. In Af-Arts, Tro caused dose-dependent and biphasic dilation. Tro at 10(-5) M increased the diameter by 28 +/- 6% (n = 8, P < 0.01) until 20 min, with the diameter remaining at this level for 60 min, and then Tro began to dilate Af-Arts again. At 120 min, Tro at 10(-5) M further increased the diameter by 23 +/- 4% (n = 6). Disrupting the endothelium had no effect on either dilation (n = 7 or n = 5). Pretreatment with SKF 96365 (50 microM), which inhibits both voltage- and receptor-operated calcium channels, abolished the early-phase dilation without affecting the late-phase dilation; 20 or 120 min after adding Tro at 10(-5) M, the diameter increased by 4 +/- 2% (n = 7) or 28 +/- 3% (n = 6), respectively. In contrast to Af-Arts, Tro caused monophasic dilation in Ef-Arts; Tro at 10(-5) M did not cause significant dilation until 80 min, and at 120 min the diameter increased by 37 +/- 4% (n = 5). These results suggest that in the Af-Art Tro has biphasic endothelium-independent vasodilator action, which is partly mediated by an inhibition of calcium influx. This vasodilator action may play a role in the BP-lowering effect of Tro. In addition, by dilating the postglomerular Ef-Art, Tro may decrease the glomerular capillary pressure and hence the excretion of urinary protein.

Angiotensin II↗

PubMed2002

Diabetes mellitus associated with Klinefelter's syndrome: a case report and review in Japan.

We report a case of Klinefelter's syndrome in a 48-year-old man who had diabetes mellitus associated with severe insulin resistance. We diagnosed him with Klinefelter's syndrome from his atrophic testicles, primary hypogonadism in hormonal examination, and a chromosomal aberration of 47,XXY. He showed severe decreased insulin sensitivity in a hyper-insulinemic euglycemic clamp test. He had injected over 100 units of insulin per day, however, testosterone replacement and administration of pioglitazone improved his glycemic control, which resulted in a decrease of insulin dose to less than 50 units per day. Here, we discuss the characteristics of diabetes mellitus associated with Klinefelter's syndrome in Japanese patients including this case.

Blood Glucose↗

PubMed2002

Acute-phase, but not constitutive serum amyloid A (SAA) is chemotactic for cultured human aortic smooth muscle cells.

The human serum amyloid A (SAA) protein family is subclassified as acute phase SAA (A-SAA), which comprises the SAA1 and SAA2 allelic variants, and constitutive SAA (C-SAA), which is the SAA4 isoform. Extrahepatic production of A-SAA occurs in many organs and tissues of the body, including smooth muscle cells (SMC) of the aorta. A-SAA has been shown to act locally as a chemoattractant for neutrophils, monocytes and lymphocytes via the N-formyl peptide receptor-like (fPRL1). In order to gain further understanding of the physiological significance of local production of A-SAA by SMC, the effect of exogenous A-SAA on the in vitro migration of human aortic SMC was investigated. Increased SMC migration in the presence of A-SAA was detectable after six hours and continued to increase up to 24 hours after incubation. The increased migration was dose-dependent over the concentration range 10 to 100 micrograms/ml. The mode of A-SAA stimulated SMC migration was by chemotaxis not chemokinesis. Exogenous constitutive SAA (C-SAA) did not affect SMC migration. Stimulation of SMC migration by A-SAA was inhibited by both polyclonal and monoclonal antibodies to human SAA1 and also by the inhibitors of fPRL1 signaling, wortmannin, bisindolylmaleimide and pertussis toxin. The results herein indicate that A-SAA, but not C-SAA, may serve as an autocrine factor to influence SMC migration in situations of aortic tissue injury and inflammation.

Amino Acid Sequence↗

PubMed2002

Serum paraoxonase (PON1) concentration in patients undergoing hemodialysis.

Cardiac death from atherosclerosis is common in patients undergoing hemodialysis. Although the enzymic activity of human serum paraoxonase (PON1) has been reported to be decreased in such patients, serum PON1 concentrations have not been measured. We investigated serum PON1 concentrations in 81 patients undergoing hemodialysis and 103 age-matched healthy subjects using an enzyme immunoassay. The PON1 concentration was significantly lower in the patient group than the control group (mean +/- SD: 6.78 +/- 3.56 vs 18.01 +/- 4.55 U/ml, respectively. p < 0.0001). There were no significant relationships between serum PON1 concentrations and the PON1 genetic polymorphisms, 55Leu/Met (L/M) and 192Gln/Arg (Q/R). The concentration adjusted for HDL-cholesterol or apolipoprotein A-I was also lower in the patient group. However, the specific activities (enzyme activity divided by the PON1 concentration) of paraoxonase and arylesterase were increased in the patient group compared with the control group. In the male patients, but not the female patients, PON1 concentrations were significantly lower in subjects with than without coronary heart disease (CHD) (mean +/- SD: 4.48 +/- 2.77 vs 7.34 +/- 3.22 U/ml, respectively. p < 0.01). In conclusion, the serum PON1 concentration in hemodialyzed patients was significantly decreased, resulting in an attenuation of PON1 enzymic activity. This decrease may be in part involved in the development of cardiovascular disease.

Aged↗

PubMedDate not supplied

Spontaneous regression of herniated cervical disc.

BACKGROUND CONTEXT: Spontaneous regression of herniated lumbar disc has been well established. However, spontaneous regression of herniated cervical disc is rare, and such reports are few. PURPOSE: To present a rare case of spontaneous regression of herniated cervical disc. STUDY DESIGN: A case study. METHODS: A 27-year-old man presented with severe pain on the left C6 level. Magnetic resonance imaging (MRI) revealed a lateral extruded disc at the C5-C6 level. The patient refused discectomy. RESULTS: The patient's pain disappeared after 3 weeks. Follow-up MRI revealed partial spontaneous regression in the extruded disc after 3 weeks and complete spontaneous regression after 12 months. CONCLUSION: All previous cases of herniated cervical disc that regressed spontaneously have been of the extruded type. In the patient with the cervical extruded disc, nonsurgical conservative observation should be considered an option for treatment.

Adult↗

PubMedDate not supplied

Protein tyrosine phosphatase 1B is impaired in skeletal muscle of diabetic Psammomys obesus.

Protein tyrosine phosphatases (PTPases) have been suggested to modulate the insulin receptor signal transduction pathways. We studied PTPases in Psammomys obesus, an animal model of nutritionally induced insulin resistance. No changes in the protein expression level of src homology PTPase 2 (SHP-2) (muscle, liver) or leukocyte antigen receptor (LAR) (liver) were detected. In contrast, the expression level of PTPase 1B (PTP 1B) in the skeletal muscle, but not in liver, was increased by 83% in the diabetic animals, compared with a diabetes-resistant line. However, PTP 1B-specific activity (activity/protein) significantly decreased (50% to 56%) in skeletal muscle of diabetic animals, compared with both the diabetes-resistant line and diabetes-prone animals. In addition, PTP 1B activity was inversely correlated to serum glucose level (r = -.434, P < .02). These findings suggest that PTP 1B, though overexpressed, is not involved in the susceptibility to insulin resistance in Psammomys obesus and is secondarily attenuated by hyperglycemia or other factors in the diabetic milieu.

Animals↗

PubMedDate not supplied

Headaches associated with Rathke's cleft cyst.

OBJECTIVE: Headaches are common presentations in patients with Rathke's cleft cyst (RCC). This study was conducted to elucidate the characteristics and underlying mechanisms of the headache. METHODS: We retrospectively studied 46 patients with RCC, 33 of whom underwent surgical intervention. RESULTS: Headache, particularly frontal headache, was the most common symptom, occurring in 27 patients (58.7%). Eleven patients with sudden episodic headache mimicking that of pituitary apoplexy. Although the presence of headache did not correlate with cyst size, it was significantly more common in RCCs with: high- and iso intensity content on T1-weighted MR image (P= .0363), mucous content within the cyst (P= .0023), and intense chronic inflammation at the cyst wall (P= .0276). Among 6 patients with histologically recognized intense inflammation, every patient had frontal headache (P= .0407), 5 patients had episodic headache (P= .0002), and 4 patients had associated hypopituitarism (P= .0073), none of which improved after surgical intervention. Headaches improved after surgery in 17 of 21 patients (81.0%). CONCLUSIONS: Headache, particularly frontal episodic headache, is a common and characteristic manifestation in patients with RCC and may indicate intermittent inflammatory reactions caused by mucous content. Patients with episodic headache should undergo surgical treatment to prevent exacerbation of the inflammation that can result in irreversible endocrine dysfunction.

Adult↗

PubMedDate not supplied

Comparison of cytotoxicity and radical scavenging activity between tea extracts and Chinese medicines.

Three hot water extracts of black tea, green tea and powdered green tea and five Chinese medicines (Shosaiko-tou, Orengedoku-tou, Goshuyu-tou, Choto-san, Keishininjinn-tou) were investigated for their ability to modify nitric oxide (NO) production by lipopolysaccharide (LPS)-stimulated mouse macrophage-like Raw 264.7 cells, and for their cytotoxicity, radical intensity and scavenging activity. All eight materials significantly reduced the extracellular concentration of NO in the LPS-stimulated Raw 264.7 cells. ESR spectroscopy shows that tea extracts, which had higher cytotoxicity, generated higher amounts of radicals, and more efficiently scavenged O2- (generated by hypoxanthine-xanthine oxidase reaction), hydroxyl radical (generated by Fenton reaction) and NO (generated by 1-hydroxyl-2-oxo-3-(N-3-methyl-3-aminopropyl)-3-methyl-1-triazene) than Chinese medicines. Close association between the radical intensity and radical scavenging activity suggests their bimodal (anti-oxidant and pro-oxidant) action. Pretreatment of mice with tea extracts significantly reduced the lethality of Escherichia coli-infection. All tea extracts showed no apparent anti-HIV activity. The present study demonstrates, for the first time, several attractive features of tea extracts in comparison with Chinese medicines, suggesting the possible application of the tea extracts for radical-mediated diseases.

Animals↗