Biomedical subjects

M Shimizu

Publications and source records attributed to M Shimizu.

At least 667 records · Page 37Linked to original sources

PubMed1996

Sonicated albumin for evaluating midventricular obstruction in hypertrophic cardiomyopathy.

The flow dynamics of midventricular obstruction in hypertrophic cardiomyopathy were evaluated with intravenous injection of sonicated albumin in 14 patients with vague velocity profiles on conventional continuous wave Doppler echocardiography. Nine patients (64%) demonstrated a clear envelope after the injection. The following three patterns of continuous Doppler profiles were obtained : 1) a monophasic flow profile with a brief and sharp increase in peak velocity in late systole, 2) a late-peaking systolic flow and a diastolic flow during isovolumic relaxation time emerging after sonicated albumin injection (biphasic flow profile), 3) a biphasic flow profile with systolic and diastolic flow waves having a notch around the second heart sound. The calculated peak pressure gradients from the modified Bernoulli equation did not differ significantly with the presence of diastolic wave or the site of obstruction. Therefore, these are independent parameters for estimating the severity of midventricular obstruction. Therefore, these are independent parameters for estimating the severity of midventricular obstruction. The sonicated albumin method was useful in delineating the flow profile, and thus evaluating the hemodynamics of midventricular obstruction in hypertrophic cardiomyopathy.

Aged↗

PubMed1996

Chronic antidepressant exposure enhances 5-hydroxytryptamine7 receptor-mediated cyclic adenosine monophosphate accumulation in rat frontocortical astrocytes.

In rat frontal cortical astrocytes, 5-hydroxytryptamine (5-HT), 5-carboxamidotryptamine and 5-methoxytryptamine elicited a concentration-dependent increase of cyclic AMP accumulation, with EC50 values of 137 +/- 7 nM (5-HT), 10.4 +/- 3.9 nM (5-carboxamidotryptamine) and 57.8 +/- 13.6 nM (5-methoxytryptamine). Accumulation of cyclic AMP stimulated by 5-HT (10 microM) was inhibited by methiothepin (IC50 = 21 +/- 13 nM) but not by pindolol, SCH 23390, ICS 205-930 or GR 113808. These pharmacological effects on cyclic AMP formation in astrocytes are consistent with those observed in 5-HT7 receptor binding studies. Indeed, reverse transcription-polymerase chain reaction analysis revealed the presence of 5-HT7 mRNA in astrocytes. Chronic exposure of astrocytes to mianserin (0.05-4 microM) or amitriptyline (1-8 microM) for 3 days produced a concentration-dependent enhancement of 5-HT-stimulated cyclic AMP accumulation, with EC50 values of 0.47 +/- 0.04 microM (mianserin) and 2.5 +/- 0.3 microM (amitriptyline). The enhancement of cyclic AMP accumulation was time dependent, reaching maximal levels within 2 days. Mianserin exposure (2 microM, for 3 days) resulted in a comparable enhancement of cyclic AMP accumulation mediated by 5-carboxamidotryptamine and 5-methoxytryptamine, whereas this treatment had no effect on cyclic AMP production induced by G protein-specific stimulators and catalytic subunit-selective stimulators. The mianserin-induced enhancement of 5-HT-stimulated cyclic AMP accumulation was decreased by methiothepin (IC50 = 15 +/- 8 nM) and significantly attenuated by pretreatment with 5-HT7 receptor antisense oligonucleotides, suggesting that chronic mianserin exposure produces an increase in 5-HT7 receptor activity. Chronic exposure to maprotiline, setiptiline or clomipramine (5 microM, for 3 days) mimicked the effect of mianserin. The enhancement of 5-HT7 receptor activity after chronic antidepressant exposure may be a mechanism underlying the therapeutic effects.

Adenylyl Cyclases↗

PubMed1996

Systemic lupus erythematosus with ischemic peripheral neuropathy and lupus anticoagulant: response to intravenous prostaglandin E1.

We report a case of systemic lupus erythematosus with cutaneous vasculitis and peripheral neuropathy. Results of laboratory examinations revealed lupus anticoagulant in the patient's serum. His lower limbs showed asymmetry. A sural nerve biopsy specimen showed modest degeneration of nerve fibers and incomplete obstruction of nutrient vessels. His cutaneous vasculitis responded to treatment with high-dose corticosteroid, but the lower limb neuropathy responded incompletely. Daily intravenous prostaglandin E1 treatment improved his neurologic and cutaneous symptoms markedly. Our case implied that nutritional vascular ischemia caused by lupus anticoagulant is involved in the pathogenesis of lupus neuropathy in addition to well-known peripheral nerve vasculitis. It also documented the effectiveness of intravenous prostaglandin E1 in the treatment of systemic lupus erythematosus.

Adult↗

PubMed1996

Enhanced calcium response to serotonin in platelets from patients with affective disorders.

In this report we have investigated the intracellular calcium (Ca2+) mobilization mediated by serotonin 5-HT2A receptors in the platelets of 13 patients with bipolar disorder and 12 patients with major depression in comparison with 15 healthy control subjects. We found an enhanced intracellular Ca2+ rise in response to 5-HT in platelets from both bipolar patients and patients with major depression. The 5-HT2A receptor-mediated intracellular Ca2+ signaling mechanism may have an important role in the pathophysiology of affective disorders.

Adult↗

PubMed1996