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Biomedical subjects

A Imai

Publications and source records attributed to A Imai.

At least 91 records · Page 5Linked to original sources
PubMed1997

Detection of SRY in 45,X/47,XYY mosaicism leading to phenotypic female.

SRY on the Y chromosome initiates male sex determination. We tested a phenotypic female with sex chromosome mosaicism, X/XYY, for SRY expression. SRY was determined by polymerase chain reaction (PCR) amplification in genomic DNA from a female patient with a sex chromosome mosaic complement, 45,X/47,XYY, followed by sequencing analyses. The patient yielded the PCR product with predicted size and homology to the consensus sequence of SRY. The demonstration of SRY provides evidence that the female phenotype in the presence of sex chromosome mosaicism, X/XYY, may result from alterations in another part of the sex-determining pathway or downstream from SRY.

Adolescent↗
PubMed1997

Detection of novel molecules recognized by anti-placental lactogen antibody in rat amniotic fluid.

Amniotic fluid contains various bioactive substances including the placental PRL family. In the present study, it was elucidated that rat amniotic fluid contained immunoreactive proteins which had different molecular sizes and pI values from the authentic placental lactogens (PLs) in the rat, recognized by antipeptide antibody to the N-terminal peptide of rat PL-I. Immunoreactive PLs residing in the amniotic fluid were characterized further by two-dimensional sodium dodecyl sulfate gel electrophoresis (2DE), immunoblotting and anion-exchange chromatography. Amniotic fluid collected from rats on day 12 of pregnancy contained two PL-like molecules, tentatively called A1 (MW 75 kDa, pI 4.6) and A2 (MW 99-102 kDa, pI 5.3-5.4). A1 and A2 are specific to the amniotic fluid, because no such molecules were found in the serum or placental extracts. Immunoblot analysis of amniotic fluid revealed that A1 levels increased, whereas those of A2 decreased to an undetectable level up to day 16 of pregnancy. When the A1 concentrations from days 12 to 20 were monitored intensively, they increased from day 12 to 14, were maintained until day 18, and then decreased dramatically by day 20. The expression pattern for A1 was therefore completely different from those of authentic placental PRL family members found in serum and placental tissue, indicating that the A1 is distinct from them. Partial purification by anion-exchange chromatography and 2DE revealed that A1 consisted of 5 isoforms.

Amniotic Fluid↗
PubMed1997

Magnetic resonance evaluation of uterine malformation with corpus agenesis.

Because no treatment is available and its rare prevalence, uterine fundal agenesis is seldom mentioned in the literature. A woman with uterine corpus agenesis, without other genital tract anomalies, presented with primary amenorrhea and infertility. Gonadotropins and ovarian steroids showed normal cyclic variations. A thorough evaluation, including history, physical examination, and appropriate imaging techniques [hysterosalpingography, ultrasonography and magnetic resonance imaging (MRI)] demonstrated extreme accuracy with MRI in the diagnosis of the anatomic defect. MRI permits noninvasive differentiation of uterine anomalies and may spare the patient's diagnostic laparoscopy.

Adult↗
PubMed1996

Evidence for coupling of phosphotyrosine phosphatase to gonadotropin-releasing hormone receptor in ovarian carcinoma membrane.

BACKGROUND: Gonadotropin-releasing hormone (Gn-RH) receptor (Gn-RHR) has been demonstrated in epithelial ovarian carcinoma (Imai et al., Cancer 1994; 74:2555-61). To examine whether Gn-RHR mediates direct antiproliferative effects, we attempted to determine stimulatory regulation by Gn-RH of phosphotyrosine phosphatase (PTP) activity in plasma membranes isolated from ovarian carcinoma samples. METHODS: Surgically removed ovarian carcinomas were screened for Gn-RHR expression prior to plasma membrane isolation. The phosphotyrosine level was observed by: (1) immunoblotting of membrane extracts with antiphosphotyrosine antibodies, and (2) dephosphorylation from 32P-labeled membrane protein. Membrane PTP activity was determined using the synthetic substrate p-nitrophenyl in a spectrophotometric assay. RESULTS: A Gn-RH analog alone, or guanosine thiotriphosphate (GTP-gamma-S) alone, caused a remarkable loss of phosphotyrosine from a 35-kD protein of the membranes; incubation with a Gn-RH analog and GTP-gamma-S produced a further dephosphorylation of this endogenous protein. The Gn-RH analog buserelin stimulated the PTP activity of the membranes in a dose-dependent manner (P < 0.01). GTP-gamma-S enhanced the stimulatory action of Gn-RH on PTP; GDP-gamma-S reversed the Gn-RH action. A similar stimulation of PTP was observed (P < 0.01) when carcinoma tissue slices were exposed to Gn-RH analog in vivo prior to assay in vitro. CONCLUSIONS: Activation of PTP by Gn-RH stimulated the loss of phosphotyrosine from endogenous proteins through GTP-binding protein within plasma membrane isolated from Gn-RHR-expressing ovarian carcinoma. The antimitogenic action of the hormone may occur by counteracting tyrosine phosphorylation to promote cell growth.

Cell Membrane↗
PubMed1996

Ciliated foregut cyst in cirrhotic liver.

We encountered a patient with a ciliated hepatic foregut cyst with accompanying liver cirrhosis, which was hard to distinguish from well-differentiated hepatocellular carcinoma. A lesion 2 cm in diameter was found in the subcapsular region of the medial segment of the liver. It was slightly hypoechoic on ultrasonography, of high attenuation on nonenhanced computed tomography (CT), of high intensity on T1-weighted spin echo images of magnetic resonance imaging (MRI), and of isointensity on T2-weighted spin echo images. It was not enhanced in the arterial phase images of MRI, and was shown as a complete perfusion defect on CT arterial portography. The cyst was enucleated and found to be filled with bloody mucinous fluid.

Carcinoma, Hepatocellular↗
PubMed1996

Characterization of natriuretic peptide receptors in the rat parotid.

Competition studies between 125I-ANP and ANP (atrial natriuretic peptide) or the ring-deleted analog C-ANF4-23 (C-ANF) revealed the presence of the A-type natriuretic peptide receptor (GC-A receptor) and the ANP-clearance (ANP-C) receptor in the rat parotid membrane. The ratio of the GC-A and ANP-C receptors was about 3 to 1. Enhancement of the cGMP level by the C-type natriuretic peptide (CNP) revealed the presence of the B-type natriuretic peptide receptor (GC-B receptor) in the rat parotid gland. Based on the binding studies with ANP and C-ANF and cGMP analysis by ANP and CNP, the natriuretic peptide receptors in the rat parotid gland were demonstrated to have a rank order on the amount of GC-A receptor > GC-B receptor > ANP-C receptor.

Animals↗
PubMed1996

Expression of mRNA encoding cAMP-specific phosphodiesterase isoforms in rat parotid glands.

In previous reports, we have shown that cAMP-specific phosphodiesterase (PDE4) is the major PDE in the rat parotid gland, and that PDE4 is activated by phosphorylation. In this study, we investigated the expression of PDE4 isoform genes and alternative splicing variants of PDE4D in the rat parotid gland using reverse transcriptase-polymerase chain reaction (RT-PCR). PDE4A, PDE4B, PDE4C and PDE4D of PDE4 subfamily were expressed. PDE4D was found to be the dominant PDE4 isoform. A weak band of PDE4C was detectable. Three alternative splicing variants (PDE4D1, PDE4D2 and PDE4D3) derived from the rat PDE4D gene were expressed in the parotid gland. These data suggested that the intracellular cAMP level is regulated by multiple response mechanisms through the activations of the PDE by phosphorylation and gene expression in the rat parotid gland.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1996

Effect of cyclic GMP produced by natriuretic peptides on osteoblast-like MC3T3-E1 cells.

The C-type natriuretic peptide (10(-7) M) and atrial natriuretic peptide (10(-7) M) enhanced cGMP accumulation by 418 and 83 times the control value, respectively, in osteoblast-like MC3T3-E1 cells. The natriuretic peptide B receptor was assumed to be the major natriuretic peptide receptor. 8-Bromoguanosine 3',5'-cyclic monophosphate (8-Br-cGMP) activated alkaline phosphatase doubled the activity versus the control value on day 15. Phosphodiesterase activity was not stimulated by the addition of cGMP (1 MicroM). cGMP-dependent protein kinase (G kinase) activity of the supernatant fraction was 25.5 pmol/min/mg protein. The 42 kDa protein band was detected to be phosphorylated by G kinase on SDS-PAGE. These results supported the hypothesis that natriuretic peptides regulate the differentiation of MC3T3-E1 cells through a cGMP-dependent pathway.

Alkaline Phosphatase↗
PubMed1996

Sensitive plaque assay and propagation of Chuzan (Kasba) virus, a Palyam serogroup orbivirus, in BHK-21 cells.

Various factors influencing plaque formation of Chuzan virus in BHK-21 cell monolayers were studied and a practical method for plaque assay was developed. On addition of trypsin (5 micrograms/ml) and/or diethylaminoethyl (DEAE)-dextran (50 micrograms/ml) to the virus diluent as the virus adsorption medium and agar overlay medium, the number of plaques increased. When 100 micrograms/ ml DEAE-dextran was added to the diluent and overlay medium, plaques were produced in about 10-fold higher numbers than without trypsin and DEAE-dextran. Based on these results, a practical plaque assay method for Chuzan virus was established. Using this method, one-step growth of Chuzan virus was performed at an input multiplicity of 25 plaque-forming units (PFU) per cell. Cytopathic effects were first observed at 7.5 h post-inoculation (p.i.), and were complete at 12 h p.i. The titre of cell-associated virus, after gradual decline during the first 3 h of incubation, showed a rise within 4.5 h p.i. and a rise to a plateau of 10(6.3)PFU/0.2 ml at 12 h p.i. By indirect immunofluorescence, virus-specific antigen was detected in the cytoplasm of the cells at 4.5 h p.i., and all the cells fluoresced at 6 h p.i. Haemagglutination activity was first detected in infected whole cultures at 7.5 h p.i. reaching a plateau of 1:64 at 15 h p.i. Plaque formation and haemagglutination by the virus were specifically inhibited by antisera against the original and the plaque-cloned virus.

Animals↗
PubMed1996

Coupling of gonadotropin-releasing hormone receptor to Gi protein in human reproductive tract tumors.

The signaling pathway by which GnRH acts in peripheral tumors is distinct from that in the anterior pituitary. We attempted to identify the guanosine triphosphate (GTP)-binding protein (G protein) subtypes linked to GnRH receptor in the genital tract tumor membranes. Surgically removed ovarian carcinomas and uterine leiomyosarcomas were screened for GnRH receptor expression before plasma membrane isolation. The G alpha i was detected by immunoblotting of membrane extracts with specific antibody and pertussis toxincatalyzed ADP-ribosylation from nicotinamide adenine dinucleotide. Membrane phosphotyrosine phosphatase activity was determined as a GnRH-sensitive membrane event using synthetic substrate p-nitrophenyl in a spectrophotometric assay. Pertussis toxin, but not cholera toxin, brought about ADP-ribosylation of an immunodetected G alpha i of 41 kDa in the GnRH receptor-positive tumor membrane. Incubation with a GnRH analog and GTP decreased the ADP-ribosylation activity in a dose-dependent manner; a half-maximal effect occurred with 30 nmol/L buserelin (P < 0.01). The apparent inhibition by GnRH of the ADP-ribosylation demonstrated that GnRH resolved the alpha-subunit of the Gi to GTP-bound form in the membranes. The action of GnRH was neutralized by a competitive antagonist, antide. Pretreatment of the membrane with the pertussis toxin completely inhibited GnRH-sensitive phosphotyrosine phosphatase activity (P < 0.01). These data demonstrate the coupling of GnRH receptor to Gi protein subfamily. The Gi which couples GnRH receptor to the effector may define the difference of responses by peripheral tumor and the anterior pituitary.

Adenosine Diphosphate Ribose↗
PubMed1996

[Effect of preoperative oral 5-fluorouracil on cell cycle of advanced cervical squamous cell carcinoma].

Using flow cytometry, we examined the correlations between the tumor stage and the cell cycle in subjects with advanced cervical squamous cell carcinoma as well as between the changes of cell cycle caused by 5-FU and their prognoses. Before 5-FU treatment, 75.9 +/- 9.6% of the patients were at G1 phase, 16.8 +/- 3.9% at S and 7.3 +/- 4.5% at G2/M. The change of cell cycle was not accompanied by the progression of tumor stage. Sixteen patients received oral 5-FU (300 mg/day) for at least 2 weeks before operation. In the patients at stage I, the cell cycle was not changed even after 5-FU treatment. They have been cancer-free for 3 postoperative years. While early recurrence was found in 4 of 5 cases at stage II or III showing progression at G1, all 6 cases who had regressed or remained unchanged at G1 were free from recurrence (p = 0.0152). These results suggested that the cell cycle is not necessarily correlated with the progression of tumor stage in patients with this kind of carcinoma, and that the change of cell cycle due to preoperative oral 5-FU could be a predictive indicator for their prognoses. Especially for those with poor prognoses who had shown progression at G1, more potent adjuvant chemotherapy should be planned.

Administration, Oral↗