Yohnosuke Kobayashi

Endothelin is a potent secretagogue for atrial natriuretic peptide in cultured rat atrial myocytes.

Using cultured neonatal rat atrial cardiocytes, we have studied the effect of synthetic porcine endothelin (pET), a novel potent vasoconstrictor isolated from endothelial cells, on the release of immunoreactive (IR) rat atrial natriuretic peptide (rANP). pET stimulated IR-rANP secretion in a dose-dependent manner (10(-10)-10(-7) M) with an approximate half-maximally stimulatory dose of 2 x 10(-10) M. The pET-induced IR-rANP secretion was attenuated by Ca2+-channel blocker nicardipine, but no further stimulation was induced when combined with a Ca2+-channel agonist BAY-K 8644. pET in combination with tetradecanoyl-phorbol-acetate resulted in a synergistic effect on IR-rANP secretion. These data suggest that ET may play as an endogenous secretagogue for rANP by modulating Ca2+ influx through the voltage-dependent Ca2+-channels in atrial cardiocytes.

Epilepsy with Continuous Spike‐Waves During Slow Sleep and Its Treatment

SUMMARY: Five children with epilepsy with “continuous spike‐waves during slow sleep” (CSWS) are reported. The main clinical features of CSWS include (a) onset between 5 and 7 years of age, (b) the occurrence of several types of seizure (i.e., partial motor, generalized motor, and atypical absence), and (c) the presence of language disturbances and abnormal behavior based on emotional impairment. The EEG findings were characterized by sleep tracings showing almost continuous (>95%), diffuse slow spike and wave activity. After treatment with valproate (VPA) (or ethosuximide, ESM) and clonazepam (CZP), the spike and wave complex status disappeared. Symptoms and signs of the CSWS also decreased. We suggest that combined treatment is an appropriate treatment for CSWS.

Successful control with bromide of two patients with malignant migrating partial seizures in infancy

A 3-month-old male and a 4-month-old female infant with intractable seizures were diagnosed as having malignant migrating partial seizures in infancy (MMPSI) with developmental arrest on the basis of characteristics of symptoms, clinical courses and EEGs. We treated these two patients with potassium bromide (80 mg/kg) after conventional antiepileptic drugs failed to adequately control the seizures. The potassium bromide therapy resulted in complete control of seizures in one patient, and more than 95% reduction in seizure frequency in the other.

Comparative analyses of megakaryocytes derived from cord blood and bone marrow

Thrombocytopenia is typically observed in patients undergoing cord blood transplantation. We hypothesized that delayed recovery of the platelet count might be caused by defects in the megakaryocytic differentiation pathway of cord blood progenitors. To test this hypothesis, we compared the features of in vitro megakaryocytopoiesis between cord blood progenitors and those in bone marrow cells after isolation of CD34+ cells as progenitors. The proliferative responses of the progenitors in cord blood are higher than those in bone marrow cells in the presence of interleukin (IL)‐3, stem cell factor (SCF) and thrombopoietin (TPO). However, the ability to generate mature megakaryocytes was higher in bone marrow progenitors than in cord blood in the same in vitro culture system, when examined by the expression of CD41, polyploidy and proplatelet formation. Furthermore, an earlier induction of c‐mpl protein, a receptor for TPO, was observed in the progenitors from bone marrow than in those from cord blood in the presence of SCF and IL‐3. Therefore, the ability to generate mature megakaryocytes in bone marrow progenitors is superior to that in cord blood, and the delayed engraftment of platelets after cord blood transplantation might be attributed to the features of cord blood megakaryocyte progenitors.

Evaluation of Preclinical Atherosclerosis by Flow-Mediated Dilatation of the Brachial Artery and Carotid Artery Analysis in Patients with a History of Kawasaki Disease

Cardiac sequelae of Kawasaki disease are an important cause of ischemic heart disease in young adults. The possibility of early progression of atherosclerosis following Kawasaki disease is therefore of great concern. We examined whether preclinical atherosclerotic changes are seen in patients with a history of Kawasaki disease, and whether these changes appear in all or in only a proportion of patients. Sixty-five patients with a history of Kawasaki disease, aged 13.1 ± 2.1 years, and 20 aged-matched controls participated in the study. All subjects underwent flow-mediated dilatation (FMD) of the brachial artery and analysis of carotid artery size and pulse-wave transmission. Patients were classified into four groups depending on the severity of the maximum coronary artery lesion: group 0 (normal), group 1 (mild), group 2 (moderate), and group 3 (severe). There was no statistical difference in the carotid artery analyses between the four groups. FMD (mean ± SD) was significantly lower in groups 2 and 3 than in groups 0 and 1 and the control group (group 0, 19.4 ± 3.9%; group 1, 19.5 ±4.1%; group 2, 8.9 ± 2.8%; group 3, 4.2 ± 1.5%; control group, 18.8 ± 2.8%; p < 0.0001). There was a significantly negative correlation between the severity of the coronary artery lesion and FMD (p < 0.0001 for both). Endothelial dysfunction was revealed by FMD in patients with persistent coronary artery lesions subsequent to Kawasaki disease. Preclinical atherosclerosis may be present only in patients with coronary aneurysms.

Endothelin stimulates accumulations for cellular atrial natriuretic peptide and its messenger RNA in rat cardiocytes

The effect of endothelin-1 (ET-1) on secretion and synthesis of rat atrial natriuretic peptide (rANP) as well as its mRNA levels was studied in primary cultures of neonatal rat atrial cardiocytes. ET-1 dose-dependently (10(-10)-10(-7) M) increased media and cellular rANP-like immunoreactivity as well as its cytoplasmic mRNA levels in rat cardiocytes during 24 hrs incubation. These results suggest that ET-1 directly stimulates expression of the rANP gene in cardiocytes, thereby leading to enhanced synthesis and secretion of rANP.

Oxidative Metabolism and Phagocytosis of Polymorphonuclear Leukocytes in Patients with Chronic Renal Failure

The respiratory burst activity (generation of hydrogen peroxide) of peripheral polymorphonuclear leukocytes (PMN) in both phorbol myristate acetate (PMA)-stimulated and unstimulated states and phagocytosis were assessed using flow cytometry on 46 patients with chronic renal failure: 33 patients undergoing chronic hemodialysis (CHD), 8 patients who have never been on dialysis (nonhemodialysis; NHD), 5 patients undergoing continuous ambulatory peritoneal dialysis (CAPD); these patients were compared with 27 normal control subjects. In patients just before the initiation of dialysis, impaired hydrogen peroxide production by PMA-stimulated PMN and depressed phagocytosis were noted, which was restored to the control levels by hemodialysis. A mild but significant reduction of hydrogen peroxide production in a PMA-stimulated state was found in NHD patients, and an inverse correlation was noted between the impairment of this function and the degree of diminished renal function. There was no significant difference between CAPD patients and controls in hydrogen peroxide production by PMA-stimulated PMN. Decreased hydrogen peroxide production by unstimulated PMN was observed in both CHD and CAPD patients. These findings may explain, at least partly, the enhanced susceptibility to bacterial and fungal infections of these patients.

Requirement of thrombopoietin-induced activation of ERK for megakaryocyte differentiation and of p38 for erythroid differentiation

Abstract. Thrombopoietin (TPO) plays a critical role not only in proliferation and differentiation of megakaryocytes but also in erythroid differentiation. We have investigated whether the different pathway of mitogen-activated protein kinase (MAPK) after TPO stimulation may discriminate megakaryocyte and erythroid differentiation. In this study, we have used human CD34+ hematopoietic progenitor cells (HPCs) from cord blood (CB) in serum-free liquid culture supplemented with TPO, to compare the respective effects of specific inhibitors of MAPK kinase (MEK) (PD98059) and p38 MAP kinase (p38) (SB203580) on megakaryocyte and erythroid development. PD98059, but not SB203580, significantly suppressed TPO-induced megakaryocyte differentiation when examined by the expression of CD41 and polyploidy assay. In the presence of SB203580, CD34+/CD36+ erythroid progenitors clearly decreased, whereas they increased when cultured with PD98059. These results indicate that activation of extracellular-signal-regulated kinase (ERK) is required for TPO-induced megakaryocyte differentiation and that p38 is required for TPO-induced erythroid differentiation.

Molecular cloning, sequencing and expression of cDNA encoding human trehalase

A complete cDNA clone encoding human trehalase, a glycoprotein of brush-border membranes, has been isolated from a human kidney library. The cDNA encodes a protein of 583 amino acids with a calculated molecular weight of 66,595. Human enzyme contains a typical cleavable signal peptide at amino terminus, five potential glycosylation sites, and a hydrophobic region at carboxyl terminus where the protein is anchored to plasma membranes via glycosylphosphatidylinositol. The deduced amino acid sequence of the human enzyme showed similarity to sequences of the enzyme from rabbit, silk worm, Tenebrio molitor, Escherichia coli and yeast. Northern blots revealed that human trehalase mRNA of approx. 2.0 kb was found mainly in the kidney, liver and small intestine. Expression of the recombinant trehalase in E. coli provided a high level of the enzyme activity. The isolation and expression of cDNA for human trehalase should facilitate studies of the structure of the gene, as well as a basis for a better understanding of the catalytic mechanism.

Meconium-induced lung injury mediated by activation of alveolar macrophages

To clarify the mechanism of meconium-induced cellular injury, we examined the effect of meconium on the alveolar macrophages (AM) and bronchial epithelial cells (AK-D). Meconium obtained from healthy newborns was added to culture medium of AM and/or AK-D, which were cultured for 1 hour. Superoxide anion production of AM and the expression of intercellular adhesion molecule-1 (ICAM-1) on AK-D stimulated by meconium or oxygen radicals were determined. As a result, superoxide anion production of AM significantly increased when AM was cultured with meconium. Expression of ICAM-1 on AK-D appeared when AK-D was stimulated by hydroxyl radical but did not when AK-D was cultured with meconium. These results suggest that meconium-induced lung injury may occur through an activation of alveolar macrophages and the macrophage-epithelial cell axis may be important for the pathogenesis of meconium aspiration syndrome.