Biomedical subjects

T Shishido

Publications and source records attributed to T Shishido.

At least 37 records · Page 2Linked to original sources

PubMed2001

In vivo assessment of acetylcholine-releasing function at cardiac vagal nerve terminals.

We examined whether the ACh concentration measured by cardiac microdialysis provided information on left ventricular ACh levels under a variety of vagal stimulatory and modulatory conditions in anesthetized cats. Local administration of KCl (n = 5) and ouabain (n = 7) significantly increased the ACh concentration in the dialysate to 4.3 +/- 0.8 and 7.3 +/- 1.3 nmol/l, respectively, from the baseline value of 0.6 +/- 0.5 nmol/l. Intravenous administration of phenylbiguanide (n = 5) and phenylephrine (n = 6) significantly increased the ACh concentration to 5.4 +/- 0.9 and 6.0 +/- 1.5 nmol/l, respectively, suggesting that the Bezold-Jarisch and arterial baroreceptor reflexes affected myocardial ACh levels. Modulation of vagal nerve terminal function by local administration of tetrodotoxin (n = 6), hemicholinium-3 (n = 6), and vesamicol (n = 5) significantly suppressed the electrical stimulation-induced ACh release from 20.4 +/- 3.9 to 0.6 +/- 0.1, 7.2 +/- 1.9, and 2.7 +/- 0.6 nmol/l, respectively. Increasing the heart rate from 120 to 200 beats/min significantly reduced the myocardial ACh levels during electrical vagal stimulation, suggesting a heart rate-dependent washout of ACh. We conclude that ACh concentration measured by cardiac microdialysis provides information regarding ACh release and disposition under a variety of pathophysiological conditions in vivo.

Acetylcholine↗

PubMed2001

A new model-based method of reconstructing central aortic pressure from peripheral arterial pressure.

We have shown in our previous study that the transfer function between central aortic pressure and tonometric radial arterial pressure can be modeled as a pure elastic lossless tube terminated with a modified Windkessel. We hypothesized, using the model-derived radial arterial flow, that central pressure could be reconstructed by adding the time-shifted forward and backward pressure components (Stergiopulos et al.: Am J Physiol 274: H1386---H1392, 1998). In eight patients (age 16--75), central micromanometric and radial arterial tonometric pressure were measured simultaneously. We imposed measured tonometric pressure to the terminal modified Windkessel to estimate radial arterial flow, with which tonometric pressure was separated into forward and backward components. These components were then appropriately time shifted, and summed to central pressure. We used average parameter values for the terminal impedance, but individualized the transmission delay. The poor correlation (r(2)) between tonometric and central pressure (0.264--0.765) was improved by both central pressure reconstruction methods (generalized transfer function: 0.887--0.974, model-based method: 0.849--0.979). The sensitivity analysis indicated that the key model parameter in reconstructing central pressure was the transmission delay. We conclude that our model-based method was capable of reconstructing central pressure as precisely as the generalized transfer function method, and also capable of individualizing the transfer function by changing the transmission delay.

Aorta↗

PubMed2001

Laterality in direct and indirect inotropic effects of sympathetic stimulation in isolated canine heart.

Although sympathetic nerve stimulation is known to increase ventricular contractility, concomitant increases in heart rate (HR) make it difficult to separate its direct inotropic effect from indirect inotropic effect through a force-frequency mechanism. We stimulated the stellate ganglia in 8 isolated canine hearts with functional sympathetic nerves. Right sympathetic stimulation at 10 Hz increased ventricular end-systolic elastance (E(es)) by 95.7 +/- 7.5% (p < 0.001) and HR by 32.5 +/- 4.2% (p < 0.05). In contrast, left sympathetic stimulation at 10 Hz increased E(es) by 70.7 +/- 6.5% (p < 0.001) without significant changes in HR. Preventing the chronotropic response by fixed-rate pacing attenuated the E(es) response to right sympathetic stimulation at 5 Hz (52.0 +/- 5.1 vs. 22.8 +/- 2.8%, p < 0.001), but not to left sympathetic stimulation at 5 Hz (54.5 +/- 3.4 vs. 53.3 +/- 2.2%, NS). In the isolated canine heart, the right sympathetic nerve affected E(es) by both the direct inotropic effect and the indirect HR-dependent inotropic effect. In contrast, the left sympathetic nerve regulated E(es) primarily by its direct inotropic effect.

Animals↗

PubMed2001

Low compliance rather than high reflection of arterial system decreases stroke volume in arteriosclerosis: a simulation.

Although various investigators have suggested that the left ventricles of aged subjects suffer from high-frequency reflection, arterial reflection is larger in the low-frequency range because of a larger impedance mismatch. It has not been quantified whether high-frequency reflection rather than low-frequency reflection has larger deleterious effects on stroke volume. We used a computer simulation method to evaluate how increases in high- and low-frequency arterial reflections associated with age-related arterial sclerosis affect left ventricular (LV) pump function. Low-frequency reflections derive principally from the total arterial compliance, and high-frequency reflections result from impedance fluctuations in the high-frequency range. We numerically coupled a time-varying elastance LV model with a variety of arterial impedances to quantitatively evaluate the effects of low- and high-frequency reflections on LV pump performance. When we simultaneously increased low- and high-frequency reflections to levels of sclerotic impedance (type A in Murgo et al., Circulation 62: 105-116, 1980), stroke volume decreased by 4.4%. Further increases of the reflections up to 8 times of the type A impedance lowered stroke volume by 15.9%. This trend was clearly seen with selective increases in low-frequency reflections (3.5 and 20.2% decrease in stroke volume, respectively), but not with those in high-frequency reflections (1.0% decrease and 0.9% increase in stroke volume, respectively). Thus we conclude that the detrimental effect of increases in arterial reflections associated with arterial sclerosis on stroke volume is mild and mainly attributable to decreased compliance rather than to increased high-frequency reflections.

Arteriosclerosis↗

PubMed2001

[Adenocarcinoma of the renal pelvis and transitional cell carcinoma of the ureter occurring 11 years after radical cystectomy for bladder cancer: a case report].

We report a case of upper urinary tract carcinoma which recurred 11 years after total cystectomy. A 52-year-old man presented with complaints of a sense of residual urine and terminal miction pain. Urinary cytology, cystoscopic examination and intravenous pyelography revealed normal findings. Twenty months later, because class V urinary cytologic findings were detected, transurethral biopsy was performed. Carcinoma in situ was diagnosed pathologically. Therefore, total cystectomy and ileal conduit urinary diversion were performed. The pathological diagnosis was transitional cell carcinoma, grade 3, pTis. At 127 months postoperatively, laboratory examination revealed an extremely high serum level of LDH (3,084 U/l). The right kidney was not visualized on IVP and computed tomography revealed a right renal irregular mass. On the suspicion of a renal pelvic tumor, right total nephroureterectomy was done. The pathologic diagnosis was renal pelvic adenocarcinoma and ureteral transitional cell carcinoma. The patient was treated postoperatively with 3 cycles of systemic chemotherapy and radiotherapy. The serum level of LDH returned to normal. However, one year later, the serum level of LDH elevated to 1,118 U/l. He died of retroperitoneal lymph node, left adrenal gland and pulmonary metastases.

Adenocarcinoma↗

PubMed2000

The adapter type protein CMS/CD2AP binds to the proto-oncogenic protein c-Cbl through a tyrosine phosphorylation-regulated Src homology 3 domain interaction.

CMS/CD2AP is a cytoplasmic protein critical for the integrity of the kidney glomerular filtration and the T cell function. CMS contains domains and motifs characteristic for protein-protein interactions, and it is involved in the regulation of the actin cytoskeleton. We report here that the individual SH3 domains of CMS bind to phosphotyrosine proteins of approximately 80, 90, and 180 kDa in cell lysates stimulated with epidermal growth factor. The second SH3 domain of CMS bound specifically to a tyrosine-phosphorylated protein of 120 kDa, which we identified as the proto-oncoprotein c-Cbl. The c-Cbl-binding site for CMS mapped to the carboxyl terminus of c-Cbl and is different from the proline-rich region known to bind SH3-containing proteins. CMS binding to c-Cbl was markedly attenuated in a tyrosine phosphorylation-defective c-Cbl mutant indicating that this interaction is dependent on the tyrosine phosphorylation of CMS. It also implies that CMS interacts with c-Cbl in an inducible fashion upon stimulation of a variety of cell-surface receptors. Immunofluorescence analysis revealed that both proteins colocalize at lamellipodia and leading edges of cells, and we propose that the interaction of CMS with c-Cbl offers a mechanism by which c-Cbl associates and regulates the actin cytoskeleton.

Actins↗

PubMed2000

Single-beat estimation of end-systolic elastance using bilinearly approximated time-varying elastance curve.

BACKGROUND: Although left ventricular end-systolic elastance (E(es)) has often been used as an index of contractility, technical difficulties in measuring volume and in changing loading conditions have made its clinical application somewhat limited. By approximating the time-varying elastance curve by 2 linear functions (isovolumic contraction phase and ejection phase) and estimating the slope ratio of these, we developed a method to estimate E(es) on a single-beat basis from pressure values, systolic time intervals, and stroke volume. METHODS AND RESULTS: In 11 anesthetized dogs, we compared single-beat E(es) with that obtained with caval occlusion. Although the decrease (but not the increase) in contractility (5.3 to 11.4 mm Hg/mL) and the change in loading conditions (3.7 to 34.0 mm Hg/mL) over wide ranges significantly altered the slope ratio, the estimation of E(es) was reasonably accurate (y=0.97 x 0.46, r=0. 929, SEE=2.1 mm Hg/mL). CONCLUSIONS: E(es) can be estimated on a single-beat basis from easily obtainable variables by approximating the time-varying elastance curve by a bilinear function.

Animals↗

PubMed2000

Transformation of BALB3T3 cells caused by over-expression of rat CD98 heavy chain (HC) requires its association with light chain: mis-sense mutation in a cysteine residue of CD98HC eliminates its transforming activity.

CD98 is a 125-kDa glycoprotein (GP125) consisting of an 85-kDa heavy chain (HC) and a 40-kDa light chain (LC), and is highly expressed on the cell surface of activated lymphocytes and various tumor cells. In addition to the regulatory role of CD98HC in L-, y(+)L- and Xc-amino-acid transport systems, which are principally mediated by CD98LC, we have reported transforming activity of human CD98HC. In this study, we established and analyzed BALB3T3 clones transfected with cDNAs encoding wild-type and mutated rat CD98HC proteins designated as BrH/Wild, C103S, C325S and 103/325, in which 103 and/or 325 cysteine were intact or replaced with serine. Flow cytometry with anti-rat CD98HC MAb B3 revealed that wild-type and mutated CD98HC transfectants expressed almost the same amounts of rat CD98HC proteins on the cell surface. Immunoprecipitation with B3 revealed that exogenous rat CD98HC proteins were associated with endogenous mouse CD98LC by a disulfide bond in BrH/Wild and C325S, but not in C103S and 103/325 transfectants. These transfectants showed similar doubling times and leucine and arginine transport activities, as compared with BALB3T3 and control transfectants in monolayer culture. Wild-type and C325S transfectants, however, formed much larger anchorage-independent colonies than C103S, 103/325 and control transfectants in soft agar. In addition, wild-type and C325S transfectants showed tumorigenicity in nude mice, although C103S, 103/325 and control transfectants did not. These findings indicate that over-expression of CD98HC and its disulfide-linkage with CD98LC at the cell surface result in malignant transformation of murine fibroblasts.

Amino Acid Substitution↗

PubMed2000

Neurotoxic effect of high dose methamphetamine administration on the hippocampal formation of adult mice: morphometric study using image analyzer.

The volume of the hippocampal formation was measured after repeated methamphetamine (MAP) administration. MAP (30 mg/kg, i.p.) or an equivalent volume of saline (SAL) was administered once daily for 5 days to adult male BALB/c mice. The animals were perfused 7 days after the last injection, and brain sections were stained with cresyl violet and studied with a computer-assisted image analyzer. The volume of the molecular layer at the ventral position of the dentate gyrus of MAP-treated animals was significantly decreased (77% of control, p < 0.001). In contrast, the volumes of the molecular layers at the dorsal and midseptal positions of the dentate gyrus did not change after MAP administration. Similarly, repeated MAP treatment did not affect the volumes of the granular layer and hilus at the dorsal, midseptal or ventral positions of the dentate gyrus. The present results are the first to document a persistent neurotoxic effect of high dose MAP administration on the hippocampal volume of adult mice.

Animals↗

PubMed2000

v-Crk activates the phosphoinositide 3-kinase/AKT pathway in transformation.

v-Crk induces cellular tyrosine phosphorylation and transformation of chicken embryo fibroblasts (CEF). We studied the molecular mechanism of the v-Crk-induced transformation. Experiments with Src homology (SH)2 and SH3 domain mutants revealed that the induction of tyrosine phosphorylation of cellular proteins requires only the SH2 domain, but both the SH2 and SH3 domains are required for complete transformation. Analysis of three well defined signaling pathways, the mitogen-activated protein kinase (MAPK) pathway, the Jun N-terminal kinase (JNK) pathway, and the phosphoinositide 3-kinase (PI3K)/AKT pathway, demonstrated that only the PI3K/AKT pathway is constitutively activated in v-Crk-transformed CEF. Both the SH2 and SH3 domains are required for this activation of the PI3K/AKT pathway in CEF. We also found that the colony formation of CEF is strongly induced by a constitutively active PI3K mutant, and that a PI3K inhibitor, LY294002, suppresses the v-Crk-induced transformation. These results strongly suggest that constitutive activation of the PI3K/AKT pathway plays an essential role in v-Crk-induced transformation of CEF.

Animals↗

PubMed2000

The kinase-deficient Src acts as a suppressor of the Abl kinase for Cbl phosphorylation.

The kinase activity of Abl is known to be regulated by a putative trans-acting inhibitor molecule interacting with the Src homology (SH) 3 domain of Abl. Here we report that the kinase-deficient Src (SrcKD) directly inhibits the tyrosine phosphorylation of Cbl and other cellular proteins by Abl. We found that both the SH2 and SH3 domains of SrcKD are necessary for the suppressor activity toward the Abl kinase phosphorylating Cbl. To suppress the Cbl phosphorylation by Abl, the interaction between the SH3 domain of SrcKD and Cbl is required. This interaction between SrcKD and Cbl is regulated by a closed structure of Cbl. The binding of Abl to the extreme carboxyl-terminal region of Cbl unmasks the binding site of SrcKD to Cbl. This results in a ternary complex that inhibits the Abl-mediated phosphorylation of Cbl by steric hindrance. These results illustrate a mechanism by which the enzymatically inactive Src can exert a biological function in vivo.

Amino Acid Sequence↗

PubMed2000

Cyanide intoxication induced exocytotic epinephrine release in rabbit myocardium.

Cyanide intoxication, which has been used as a model of energy depletion at cardiac sympathetic nerve terminals, causes non-exocytotic release of norepinephrine (NE). However, the effect of cyanide intoxication on cardiac epinephrine (Epi) release remains unknown. Using cardiac microdialysis in the rabbit, we measured dialysate Epi and NE concentrations as indices of myocardial interstitial Epi and NE levels, respectively. Local administration of sodium cyanide (30 mM) through the dialysis probe increased both Epi and NE levels (from 11.3+/-2.3 to 32.3+/-4.4 pg/ml and from 33.6+/-6.1 to 389.0+/-71.8 pg/ml, respectively, mean+/-S.E., P<0.01). Local desipramine (100 microM) administration suppressed the cyanide induced NE response without affecting the Epi response. In contrast, local omega-conotoxin GVIA (10 microM) administration partially suppressed the cyanide induced NE response and totally abolished the Epi response. In conclusion, cyanide intoxication causes N-type Ca(2+) channel dependent exocytotic Epi release as well as inducing N-type Ca(2+) channel independent non-exocytotic NE release.

Adrenergic Uptake Inhibitors↗

PubMed2000

Three-component coupling of acylphosphonates and two carbonyl compounds promoted by low-valent samariums: one-Pot synthesis of beta-hydroxyphosphonates

Three-component coupling of acylphosphonates and two carbonyl compounds leading to beta-hydroxyphosphonates has been achieved with low-valent samariums. Thus, acylphosphonates reacted with aldehydes in the presence of semicatalytic amounts of samarium metal or SmI(2) to give acyloxyphosphonates in good yields. The second coupling reaction of the acyloxyphosphonates with aldehydes or ketones promoted by SmI(2) afforded beta-hydroxyphosphonates instead of olefins. Moreover, these two reactions could be carried out in one pot.

Journal Article↗

PubMed2000

Local epinephrine release in the rabbit myocardial interstitium in vivo.

Although several investigations have suggested cardiac epinephrine (Epi) release, local Epi release in the myocardial interstitium in vivo has not been measured. Using cardiac microdialysis in the rabbit, we measured dialysate Epi and norepinephrine (NE) concentrations as indices of myocardial interstitial Epi and NE levels, respectively. Exocytotic release induced by local administration of KCl (100 mM) through the dialysis probe increased Epi to 24.2 +/- 13.2 pg/ml from a control value of 3.2 +/- 3.6 pg/ml (P < 0.01, n = 6). Non-exocytotic release induced by the local administration of tyramine (10 microg/ml) also increased Epi to 34.6 +/- 15.3 pg/ml (p < 0.05 from control, n = 6). We conclude that Epi can be released via both exocytotic and non-exocytotic release mechanisms from the heart.

Animals↗

PubMed2000

Differential acetylcholine release mechanisms in the ischemic and non-ischemic myocardium.

To understand better the pathophysiological roles of the vagal efferent system in ischemic heart diseases, we examined endogenous acetylcholine (ACh) release in the myocardium in vivo. Acute myocardial ischemia was induced in anesthetized cats by a 60-min occlusion of the left anterior descending coronary artery (LAD). We implanted dialysis probes in the left ventricular free wall and measured the dialysate ACh concentration using liquid chromatography. In the ischemic region, the ACh level increased from 0.68+/-0.12 to 12.3+/-3.3 n M (mean+/-S.E., P<0.01) by LAD occlusion. Bilateral vagotomy did not inhibit ischemia-induced ACh release (20.3+/-6.4 n M). In vagotomized animals, inhibition of the N-type Ca(2+)channel by intravenous administration of omega-conotoxin GVIA (10microg/kg) also failed to suppress ACh release (15.9+/-2.0 n M). However, the inhibition of intracellular Ca(2+)mobilization by local administration of 3,4,5-trimethoxybenzoic acid 8-(dietyl amino)-octyl ester (1 m M) suppressed ACh release (4.4+/-0.8 n M, P<0.05 compared with no pharmacological intervention). In the non-ischemic region, the ACh level increased from 1.9+/-0.4 to 6. 0+/-1.0 n M (P<0.05) by LAD occlusion, which was completely abolished by vagotomy. We concluded that ACh release in the ischemic region was mainly attributed to a local release mechanism, whereas that in the non-ischemic region depended on the presence of intact vagal activity. The local release mechanism would depend on intracellular Ca(2+)mobilization but not on N-type Ca(2+)channel opening.

Acetylcholine↗

PubMed2000

Effects of phencyclidine on behavior and extracellular levels of dopamine and its metabolites in neonatal ventral hippocampal damaged rats.

RATIONALE: The use of neonatal hippocampal lesioned rats is well established in animal models of schizophrenia. Moreover, the dysfunction of N-methyl-D-aspartate (NMDA) neurotransmission may play a crucial role in the pathophysiology of schizophrenia. OBJECTIVE: To examine the role of NMDA neurotransmission in the neonatal ventral hippocampal damaged rat. METHODS: In initial experiments, we compared the effects of mild environmental stress (HAB) and the injection of saline and methamphetamine (MAP, 1.5 mg/kg, IP) in lesioned and sham-operated rats. We also examined the effects of a single injection of phencyclidine (PCP, 10 mg/kg, IP) on locomotor activity and extracellular levels of dopamine (DA) and its metabolites in the nucleus accumbens (NAc) of lesioned and sham-operated rats using an in vivo brain microdialysis method. RESULTS: Compared with sham-operated controls, the lesioned rats showed increased locomotor activity at postnatal day 56 (PD56) but not at PD35 after HAB and MAP administration. Similarly, the lesioned rats showed increased locomotor activity at PD56 but not at PD35 after PCP administration. Unexpectedly, the increase in DA levels was significantly greater in the sham-operated rats than in the lesioned rats. CONCLUSIONS: The results suggest that neonatal hippocampal lesioned rats are accompanied by the dysfunction of NMDA neurotransmission. They also suggest that hyperresponsiveness to PCP following neonatal hippocampal lesions does not depend on the extracellular DA concentration in the NAc.

Animals↗

PubMed2000

Effects of dopamine, NMDA, opiate, and serotonin-related agents on acute methamphetamine-induced self-injurious behavior in mice.

We examined the biochemical processes responsible for acute methamphetamine (MAP)-induced self-injurious behavior (SIB) in mice. In initial experiments, a single dose of MAP (5, 10, or 15 mg/kg, IP) or an equivalent volume of saline was administered to male BALB/c mice. Acute MAP administration dose dependently increased the incidence of SIB (p < 0.05). In further experiments, we evaluated the effects of SCH23390, sulpiride, MK-801, naloxone or 5-hydroxy-L-tryptophan (5-HTP) on the incidence of acute MAP (15 mg/kg, IP)-induced SIB. Both SCH23390 (0.5 and 1.0 mg/kg, IP) and 5-HTP (100 and 200 mg/kg, IP) reduced the incidence of MAP-induced SIB (p < 0.05). MK-801 (0.125 and 0.25 mg/kg, IP) completely blocked the SIB induced by MAP (p < 0.001). In contrast, neither sulpiride (25, 50, and 100 mg/kg, IP) nor naloxone (1, 5, and 10 mg/kg, IP) affected the incidence of MAP-induced SIB. It is concluded that dopamine D(1), NMDA, and serotonin neurotransmission may be involved in critical biochemical processes responsible for acute MAP-induced SIB.

5-Hydroxytryptophan↗

PubMed2000

Increased brain angiotensin receptor in rats with chronic high-output heart failure.

BACKGROUND: The renin-angiotensin system (RAS) plays a key role in the pathophysiology of chronic heart failure (CHF). In rats, we reported that CHF enhances dipsogenic responses to centrally administered angiotensin I, and central inhibition of the angiotensin-converting enzyme (ACE) prevents cardiac hypertrophy in CHF. This suggests that the brain RAS is activated in CHF. To clarify the mechanism of the central RAS activation in CHF, we examined brain ACE and the angiotensin receptor (AT) among rats with CHF. METHODS AND RESULTS: We created high-output heart failure in 22 male Sprague-Dawley rats by aortocaval shunt. Four weeks after surgery, we examined ACE mRNA by reverse transcriptase polymerase chain reaction (RT-PCR) and AT by binding autoradiography. ACE mRNA levels were not significantly increased in the subfornical organ (SFO), the hypothalamus, or in the lower brainstem of CHF rats (n = 5) compared with sham-operated rats (SHM) (n = 6). Binding densities for type 1 AT (AT1) in the SFO (P < .05), paraventricular hypothalamic nuclei (P < .05), and solitary tract nuclei (P < .05) were higher in rats with CHF (n = 5) than in SHM rats (n = 6). Thus, in rats with CHF, AT1 expression is increased in brain regions that are closely related to water intake, vasopressin release, and hemodynamic regulation. CONCLUSIONS: The fact that AT1 expression was upregulated in important brain regions related to body fluid control in CHF rats indicates that the brain is a major site of RAS action in CHF rats and, therefore, a possible target site of ACE-inhibitors in the treatment of CHF.

Animals↗