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Biomedical subjects

S Kamada

Publications and source records attributed to S Kamada.

At least 55 records · Page 3Linked to original sources
PubMed1992

A protein binding to CArG box motifs and to single-stranded DNA functions as a transcriptional repressor.

A CArG box motif [CC(A+T-rich)6GG] is one of the DNA elements required for muscle-specific gene transcription. Nuclear factors in mouse C2 myogenic cells strongly bind to the CArG box in the first intron of the gene (Sm alpha-A) encoding human smooth muscle alpha-actin. To clone cDNAs of the CArG box-binding factor (CBF), lambda gt11 cDNA expression libraries from C2 cells were screened for in situ DNA binding specific for this CArG box sequence. The 1.6-kb cDNA (CBF-A) encoding 285 amino acids (aa) was obtained, and a beta-galactosidase fusion protein, bacterially produced from the cDNA, bound to DNA fragments containing several CArG boxes. When the expression level of CBF-A in C2 cells increased by transfection of CBF-A expression plasmids, Sm alpha-A transcription was repressed. The deduced aa sequence of CBF-A is similar to some single-stranded (ss) nucleic acid-binding proteins. The fusion protein could bind to ssDNA, whereas CBF in C2 cell nuclear extracts could not. From these results, CBF-A is a novel CArG box-, ssDNA- and RNA-binding protein, as well as a repressive transcriptional factor.

Actins↗
PubMed1992

Effects of insulin-like growth factor-II on proliferation and differentiation of ovarian granulosa cells.

The effects of insulin-like growth factor-II (IGF-II) on the proliferation and differentiation of ovarian granulosa cells were studied in cultured human and porcine granulosa cells. IGF-II significantly increased basal progesterone secretion in granulosa cells at concentrations of 1-100 ng/ml. A stimulatory effect was also observed in gonadotropin-stimulated porcine granulosa cells treated with IGF-II. The secretion of estradiol by basal and gonadotropin-stimulated porcine granulosa cells was also significantly increased by adding IGF-II. IGF-II led to dose-dependent increases in [3H]thymidine incorporation into DNA and in the number of granulosa cells. To further characterize the cellular mechanisms underlying the stimulatory effects of IGF-II on the proliferation and differentiation of granulosa cells, we investigated the intermediary roles of cyclic AMP and intracellular Ca2+ concentration ([Ca2+]i). Treatment with 100 ng/ml IGF-II produced a significant increase in the basal accumulation of cyclic AMP in porcine granulosa cells. However, no change of [Ca2+]i by IGF-II was noted. IGF-II produced effects in accumulation that were similar to those of IGF-I. Our findings suggest that IGF-II may be a general stimulator in the proliferation and differentiation of granulosa cells, and that cyclic AMP may be a second messenger for the effects of IGF-II in ovarian granulosa cells.

Animals↗
PubMed1992

Influence of progesterone/estradiol ratio on luteal function for achieving pregnancy in gonadotropin therapy.

The purpose of this study was to evaluate the influence of the relationship between plasma progesterone (P4) and estradiol (E2) levels in the luteal phase for achieving pregnancy in human menopausal gonadotropin (hMG)-human chorionic gonadotropin (hCG)-treated cycles. Plasma P4 and E2 levels were determined in 93 hMG-hCG-treated cycles (23 pregnant and 70 nonpregnant) of 46 patients during 3 periods of the luteal phase, using radioimmunoassay. In addition, 88 spontaneous ovulatory cycles and 100 clomiphene-treated cycles were also studied in the same manner. In hMG-hCG-treated cycles in the early luteal phase, the P4/E2 ratio in pregnant cycles was significantly higher than that in nonpregnant cycles. There was no significant difference between the P4/E2 ratios of the luteal phase of hMG-hCG-treated pregnant-group, clomiphene-treated and spontaneous ovulatory cycles. In nonpregnant cycles, however, the P4/E2 ratio in hMG-hCG-treated cycles was significantly lower than that in clomiphene-treated or spontaneous ovulatory cycles. These results suggest that in hMG-hCG-treated cycles, the P4/E2 ratio may be a more reliable index of luteal function for achieving pregnancy than P4 levels alone.

Chorionic Gonadotropin↗
PubMed1992

Synthesis and release of endothelin-1 by human decidual cells.

We have studied whether a novel vasoconstrictor, endothelin-1 (ET-1), is synthesized by and released from human decidual cells in early pregnancy, and whether ET-1 acts directly on their own cells. It was observed that ET-1-like immunoreactivity (ET-1-LI) was released from cultured decidual, but not villous, cells, as a function of time. Reverse-phase high-pressure liquid chromatography of the conditioned media from the decidual cells revealed a major peak of ET-1-LI coeluting with standard ET-1. Phorbol myristate acetate, a protein kinase C activator, dose-dependently increased the release of ET-1-LI from the decidual cells, while a protein kinase C inhibitor, H7, significantly attenuated the stimulatory effect of phorbol myristate acetate on ET-1-LI release. Northern blot analysis demonstrated the expression of messenger RNA for prepro-ET-1 in the decidual tissue, but no such messenger RNA was observed in the villous tissue. The human decidual tissue contained a noninteracting, single class of binding sites demonstrating higher affinity for ET-1 and ET-2 than ET-3. This would be most consistent with the ETA receptor subtype. An ET-1-induced, dose-dependent accumulation of total inositol phosphates was also observed in human decidual cells prelabeled with myo-[3H]inositol. The present results demonstrate for the first time that human decidual cells in early pregnancy can synthesize and release ET-1. These cells also possess specific functional receptors for ET-1 which are coupled to phosphoinositide hydrolysis. Thus our data suggest a possible role for ET-1 in autocrine and/or paracrine function in human decidual cells.

Binding, Competitive↗
PubMed1992

Direct effects of bromocriptine on the steroidogenic capability of porcine granulosa cells.

The direct effects of bromocriptine on steroidogenesis were examined in cultured porcine granulosa cells. The following observations were made with bromocriptine: (1) It significantly increased the basal or FSH-stimulated secretion of progesterone in cultured porcine granulosa cells at concentrations exceeding 10(-7) mol/l; (2) its inhibitory effect on basal estradiol secretion was demonstrated; (3) it did not influence cell number in cultured porcine granulosa cells; (4) it increased the extracellular accumulation of cAMP in a concentration-dependent manner; and (5) it did not induce a change in cytosolic free Ca2+ concentration. These findings suggest that bromocriptine exerts a direct effect on steroidogenesis in ovarian granulosa cells.

Animals↗
PubMed1992

Determination of insulin-like growth factor-2 in feto-maternal circulation during human pregnancy.

In order to clarify the roles of insulin-like growth factors (IGFs) on the human maternal-fetal environment, IGF-2 and IGF-1 levels were investigated in human plasma and amniotic fluid during pregnancy. Initially, new radio-immunoassay (RIA) systems for human IGF-2 could be developed. The sensitivity of this assay was 17.5 pg/tube and the cross-reactivity with IGF-1 was 0.64%. The pattern of change of maternal plasma IGF-2 in early pregnancy differed from that of IGF-1, but both IGF levels increased progressively in the second half of gestation, and decreased to non-pregnancy levels in the puerperium. Maternal levels of IGF-2 were approximately seven times greater than those of IGF-1. The ratio of IGF-2 to IGF-1 was 3.2 in amniotic fluid. The IGF concentrations in amniotic fluid obtained in the second trimester were significantly greater than those of term specimens, and closely related to those of prolactin (PRL) in amniotic fluid. The highest IGF-2 to IGF-1 ratio (15.9) was found in umbilical vein plasma. On Sephadex G-150 gel-chromatography of maternal and fetal plasma at term, two apparent peaks of unsaturated IGF-2 binding protein (BP) could be detected in both 150 and 40 kilo dalton (kD) regions. One main peak of unsaturated IGF-2 BP could be determined in the 40 kD region in the amniotic fluid at term. High concentration of IGF-2 could be detected in feto-maternal circulation during human pregnancy.(ABSTRACT TRUNCATED AT 250 WORDS)

Amniotic Fluid↗
PubMed1992

Direct effect of endothelin-1 on the granuloma cells of the porcine ovary.

Specific binding sites for endothelin-1 (ET-1), a novel potent vasoconstrictor peptide, as well as the effects of ET-1 on cytosolic free Ca2+ concentration ([Ca2+]i), intracellular total inositol phosphate (IP) generation and steroidogenesis were studied in cultured porcine granulosa cells. Scatchard analysis of a binding study using 125I-labelled ET-1 indicated the presence of a single class of high-affinity binding sites with almost equal affinity for ET-1 and ET-3: the apparent dissociation constant was 0.59 nmol/l and the maximal binding capacity was 1.84 pmol/mg protein. Affinity-labelling of 125I-labelled ET-1 to the membranes using disuccinimidyl tartarate as a cross-linker revealed one major and one minor band with the apparent molecular weights of 32 kDa and 49 kDa respectively. ET-1 dose-dependently (1-100 nmol/l) induced rapid and transient increases in [Ca2+]i in fura-2-labelled cells. ET-1 also dose-dependently stimulated total IPs in cells prelabelled with myo-[3H]inositol. ET-1 had a slight stimulatory effect on the secretion of progesterone but not of oestradiol from porcine granulosa cells. The present data clearly demonstrate the presence of a non-selective ET receptor (ETB) in porcine granulosa cells coupled with phosphoinositide hydrolysis and [Ca2+]i mobilization, and suggest that ET-1 may play some role in the production of progesterone by porcine granulosa cells.

Animals↗
PubMed1991

Transcriptional regulatory elements in the 5' upstream and first intron regions of the human smooth muscle (aortic type) alpha-actin-encoding gene.

We have determined the nucleotide (nt) sequence of 5.5 kb including the 5' flanking, first untranslated exon and first intron regions of the human smooth muscle (SM) (aortic type) alpha-actin-(Sm alpha A)- encoding gene. The promoter region and a part of the first intron show remarkably high sequence conservation with equivalent regions of the chicken gene, and contain multiple transcriptional regulatory elements. From transient chloramphenicol acetyltransferase gene (cat) expression assays in SM cells, a DNA fragment from nt -123 to +49 containing two CArG boxes showed strong positive promoter activity, whereas a far upstream region from nt -253 to -124 showed a negative effect. The conserved region in the first intron also contains the CArG box and showed an enhancer activity. Therefore, the human SM alpha A gene is controlled under positive and negative mechanisms.

Actins↗
PubMed1991

Structure, chromosome location, and expression of the human smooth muscle (enteric type) gamma-actin gene: evolution of six human actin genes.

Recombinant phages that carry the human smooth muscle (enteric type) gamma-actin gene were isolated from human genomic DNA libraries. The amino acid sequence deduced from the nucleotide sequence matches those of cDNAs but differs from the protein sequence previously reported at one amino acid position, codon 359. The gene containing one 5' untranslated exon and eight coding exons extends for 27 kb on human chromosome 2. The intron between codons 84 and 85 (site 3) is unique to the two smooth muscle actin genes. In the 5' flanking region, there are several CArG boxes and E boxes, which are regulatory elements in some muscle-specific genes. Hybridization with the 3' untranslated region, which is specific for the human smooth muscle gamma-actin gene, suggests the single gene in the human genome and specific expressions in enteric and aortic tissues. From characterized molecular structures of the six human actin isoform genes, we propose a hypothesis of evolutionary pathway of the actin gene family. A presumed ancestral actin gene had introns at least sites 1, 2, and 4 through 8. Cytoplasmic actin genes may have directly evolved from it through loss of introns at sites 5 and 6. However, through duplication of the ancestral actin gene with substitutions of many amino acids, a prototype of muscle actin genes had been created. Subsequently, striated muscle actin and smooth muscle actin genes may have evolved from this prototype by loss of an intron at site 4 and acquisition of a new intron at site 3, respectively.

Actins↗
PubMed1991

[The effects of insulin-like growth factor-I (IGF-I) and IGF-II on prolactin (PRL) release from human decidua and amniotic fluid circulation].

It has been reported that insulin-like growth factor (IGF) may play an important role in the feto-placental environment during pregnancy. The present study was undertaken to investigate the effect of IGF-I and IGF-II on prolactin (PRL) release from human decidual cells in vitro and in vivo. The human decidua in early pregnancy was obtained by D & C, and was enzymatically dispersed into a monocellular suspension. Monolayer cultures of these cells were exposed for 96 hours to either control media or medium supplemented with IGF-I and IGF-II. PRL levels in the media were measured by EIA. Five days after dispersion, the intracellular calcium concentration [( Ca]2+i) in cultured decidual cells was measured by the Fura-2 fluorescence method with a Spectrofluorometer. PRL and IGF-I levels in amniotic fluid of 2nd trimester and term pregnancy were measured by RIA for in vivo study. In an in vitro study, IGF-I increased PRL release from decidual cells significantly during a 96 hour culture. However, IGF-II did not enhance this PRL release. IGF-I stimulation had no effect on [Ca]2+i. In an in vivo study, amniotic fluid IGF-I levels in the 2nd trimester (139.8 +/- 28.1 ng/ml) were significantly higher than those in term pregnancy (46.4 +/- 14.2 ng/ml), and a significant positive correlation (r = 0.852, p less than 0.001) was observed between IGF-I and PRL levels in the amniotic fluid. The present in vivo and in vitro studies indicated that IGF-I plays an important role in PRL release from decidua into amniotic fluid.(ABSTRACT TRUNCATED AT 250 WORDS)

Amniotic Fluid↗
PubMed1991

[The role of angiotensin in paracrine interaction between rat anterior pituitary cells].

The present study was undertaken to investigate the role of angiotensin II (AII) in GnRH-induced prolactin (PRL) release from anterior pituitary cells of young male rats. The anterior pituitary glands were enzymatically dispersed, and subsequently the cells were allowed to reaggregate for 48 hours. Twenty-min perifusion with 100 nM GnRH increased PRL release (p less than 0.01) from the anterior pituitary cell aggregates. The integrated value for PRL release was 9.1 +/- 2.9 ng/10(7) cells. The release of angiotensin I (AI) from these perifused pituitary aggregates was significantly increased by GnRH. In contrast, GnRH-stimulated release of PRL was significantly suppressed by saralasin, a specific AII antagonist, whereas saralasin did not attenuate GnRH-induced LH release from these aggregates. These data demonstrate that GnRH is capable of stimulating PRL release through a mechanism that may involve the release of angiotensin.

Angiotensin II↗
PubMed1991

[Spontaneous rupture of the ascending aorta--a case report of successfully treated by surgery].

We experienced a case of spontaneous rupture of the ascending aorta, which seems to be the second case reported in the Japanese literature. A 64-year-old man was admitted to our hospital because of severe anterior chest pain and collapse. Dilatation of the ascending aorta associated with pericardial effusion was demonstrated on CT and echocardiography. There was, however, no evidence of intimal flap in the aorta. Emergency pericardiocentesis was done for cardiac tamponade which developed in spite of aggressive hypotensive therapy. But, persistent tamponade necessitated median sternotomy, and then, it was found that left lateral aspect of the ascending aorta was covered with fresh blood clot. Inspection from inside of the aorta after aortotomy under cardiopulmonary bypass revealed a small transmural perforation at the left side of the aorta at approximately 15 mm distal to the aortic anulus. The perforated wall was directly closed with a running 4-0 polypropylene suture, and the aortic root was wrapped around with a sheet of Teflon felt. Postoperative course was uneventful. When acute intrapericardial or intrapleural bleeding develops with no evidence of aortic aneurysm or dissection, presence of spontaneous aortic rupture should be taken into consideration, although it happens very rarely.

Aorta↗
PubMed1991

[One-staged surgery for coarctation of the aorta associated with annuloaortic ectasia--a case report].

A 37-year-old man was admitted to St. Marianna University Hospital with an episode of severe anterior chest pain. Contrast enhanced CT scan and digital subtraction angiography disclosed an aneurysmal dilatation of the aortic root and almost completely obstructed aortic isthmus. Modified Bentall operation was performed with simultaneous graft bypass using a woven Dacron prosthesis between the ascending aorta and the abdominal aorta through the median thoracoabdominal incision. Histologically the aortic wall showed cystic medial necrosis, and the aortic valve showed myxomatous degeneration. Only 9 cases with coarctation of the aorta associated with annuloaortic ectasia have been reported in the Japanese literature, and this is believed to be the first report that one-staged surgery has successfully been done dealing simultaneously both the coarctation and the annuloaortic ectasia.

Adult↗
PubMed1991

[Levels of endothelin-1 in maternal and cord plasma during pregnancy and delivery].

In order to elucidate the possible involvement of endothelin-1 (ET-1) in the development of the feto-placental unit, plasma concentrations of immunoreactive ET-1 during pregnancy and delivery were measured in the current study. Forty-four pregnant women (8 in the 1st trimester, 8 in the 2nd trimester, 12 in the 3rd trimester and 16 at delivery), 6 at 1 month postpartum and 14 non-pregnant women volunteered to participate in this study. Plasma levels of immunoreactive ET-1 in all subjects were measured by specific radioimmunoassay. Plasma cortisol, prolactin and oxytocin levels during delivery were also measured by RIA. Although plasma ET-1 levels did not change during the 1st (1.3 +/- 0.4 pg/ml, mean +/- S.E.M., n = 8) or 2nd (1.7 +/- 0.3 pg/ml, n = 8) trimester, they were significantly (p less than 0.05) higher in the 3rd trimester (2.6 +/- 0.3 pg/ml, n = 12) than those of the non-pregnant controls (1.7 +/- 0.3 pg/ml, n = 14) and returned to the control levels within 1 month post-partum (1.8 +/- 0.1 pg/ml, n = 6). Maternal ET-1 levels before labor onset (2.3 +/- 0.4 pg/ml, n = 16), at delivery (3.0 +/- 0.7 pg/ml) and 24 hours post-partum (2.7 +/- 0.5 pg/ml) showed no significant differences among them. On the other hand, ET-1 levels in cord plasma (7.0 +/- 1.2 pg/ml) were significantly higher (p less than 0.05) than those in maternal plasma. Furthermore, there were no significant correlations between plasma ET-1 levels and those of other hormones (cortisol, prolactin and oxytocin) during delivery. From these results, we concluded that maternal plasma ET-1 levels significantly increased in the last trimester and returned to non-pregnant levels within one month post-partum.

Adult↗
PubMed1990

[Right ventricular myxoma complicated by paroxysmal atrial tachycardia: a surgical case report].

A rare case of right ventricular myxoma complicated by paroxysmal atrial tachycardia (PAT) is presented. A 13-year-old boy was referred to our hospital because of the recurrent episodes of PAT. Every available medical treatment was tried to reverse the PAT, during which an abnormal mass in the right ventricle was found by echocardiography. Subsequently magnetic resonance imaging computed tomography demonstrated that the tumor developed from the anterior wall of right ventricle with a pedicle. A 10 g of reddish myxomatous mass originating from the base of anterior papillary muscle was resected including the stalk during total cardiopulmonary bypass. The transient paroxysmal atrial tachycardia developed shortly after operation, however, tachycardic episode has never recurred after that. It is noteworthy that intracardiac evaluation is necessary when there is longstanding and inveterate tachyarrhythmia in otherwise healthy children.

Adolescent↗
PubMed1989

Structure of 3'-downstream segment of the human smooth muscle (aortic-type) alpha-actin-encoding gene and isolation of the specific DNA probe.

We isolated the 3'-downstream part of the human aortic smooth muscle alpha-actin (SM alpha A)-encoding gene and determined the nucleotide sequence, including the ninth (last) exon and 3'-untranslated (UT) region. From the comparison of the human 3'-UT region with rat and chicken 3'-UT regions, its homology is lower than those in 3'-UT regions of other actin isoforms such as cardiac alpha-actin and cytoskeletal beta-actin. Therefore, by using the 3'-UT region of the human SM alpha A gene as an actin isoform-specific probe, this gene was detected as a single copy only in the human genome, which expressed the 1.7-kb RNA transcript in an aortic tissue-specific manner.

Actins↗