Biomedical subjects

H Tamada

Publications and source records attributed to H Tamada.

At least 55 records · Page 3Linked to original sources

PubMed1997

Enhancement of estrogen receptor gene expression in the mediobasal hypothalamus during anestrus in the beagle bitch.

Estrogen receptor mRNA (ER mRNA) levels were measured in the mediobasal hypothalamus (MBH) of beagle bitches at different stages of the estrous cycle, and compared with levels in ovariectomized (OVX) estrogen-treated bitches. In cyclic bitches, the level of hypothalamic ER mRNA increased during the progression of anestrus and declined thereafter. Hypothalamic ER mRNA and plasma luteinizing hormone (LH) levels during anestrus and proestrus were positively correlated (r = 0.94, P < 0.001). In OVX bitches, levels of hypothalamic ER mRNA were low, and increased significantly after treatment with a low dose of estradiol benzoate. These results suggest that, during the course of anestrus in the bitch, hypothalamic ER mRNA expression increases, and may be up-regulated by estradiol.

Animals↗

PubMed1997

Failure in learning task and loss of cortical cholingergic fibers in microsphere-embolized rats.

The present study was undertaken to elucidate the pathological changes in learning and memory functions and in the metabolism of cortical cholinergic neurons following microsphere embolism in the rat. Microspheres (48 microm) were injected into the right internal carotid artery of rats. Learning and memory functions were measured 7 or more days after the embolism by active and passive avoidance, and water maze tasks. In the biochemical study, cortical acetylcholine and choline contents, and choline acetyltransferase activity were measured. Cortical acetylcholinesterase-containing fibers were quantitatively estimated in the embolized rat. The active and passive avoidance, and water maze tasks were impaired in the microsphere-embolized rat. In the histochemical study, the density of cortical acetylcholinesterase-containing fibers of the ipsilateral hemisphere of the microsphere-embolized rat was decreased, but cell density was unchanged. Furthermore, microsphere embolism decreased the cortical acetylcholine concentration and choline acetyltransferase activity and increased the choline concentration. The results suggest that microsphere embolism causes severe damage to cortical cholinergic neurons, which may be, at least in part, related to the impairment of learning and memory functions in the sustained brain ischemia.

Acetylcholine↗

PubMed1997

Evidence for the involvement of transforming growth factor-alpha in implantation in the rat.

This study was conducted to examine the possibility for participation of transforming growth factor-alpha (TGF-alpha), one of the epidermal growth factor (EGF) family of growth factors, in implantation in the rat. Immunostaining of TGF-alpha in the periimplantation uterus showed distinct staining in the luminal and glandular epithelium and moderate staining in stromal and myometrial cells. After implantation decidual cells and embryos were also positive stained for immunostaining. Immunocytochemistry of EGF receptor showed distinct staining in the luminal and glandular epithelium during the preimplantation period, and after implantation decidua at implantation sites and embryos were stained. Intraluminal injection of anti-TGF-alpha antibodies into uterine horns at 0600 h on day 5 of pregnancy decreased the number of rats showing implantation (blue dye reaction) at 0200 h on day 6 in a dose-dependent manner. Intraluminal injection of 100 pg of TGF-alpha on day 5 of pseudopregnancy elicited a greater decidual response when compared with the vehicle-injected contralateral uterine horn. Intraluminal injection of 20 pg of TGF-alpha into each uterine horn induced implantation in 50% of the ovariectomized progesterone-treated delayed implanting rats. These results suggest that TGF-alpha is involved in the implantation process in the rat.

Animals↗

PubMed1997

Physiological role of 20alpha-dihydroprogesterone during the estrous cycle in goats.

The relationships between the effects of single or repeated subcutaneous injections of 25 mg progesterone on luteal function during the estrous cycle in goats as well as the secretion of 20alpha-dihydroprogesterone or 15-keto-13, 14-dihydro-prostaglandin F(2alpha) (PGFM), the major metabolite of PGF(2alpha), were investigated. A single dose of progesterone given on Day 4, 10, or 18 of the estrous cycle increased the concentration of 20alpha-dihydroprogesterone and did not affect the length of the cycle. Each dose of progesterone on Days 2 to 5 increased the concentration of 20alpha-dihydroprogesterone (with a later decrease each day to a nadir which then increased daily) and shortened the cycle. The 20alpha-dihydroprogesterone concentration remained high; when it decreased, the concentration of the luteolytic agent PGFM began to increase. Daily doses of 25 mg 20alpha-dihydroprogesterone given on Days 2 to 5 had no effect on the length of the cycle. These results indicate that during the estrous cycle in goats, progesterone is catabolized to the biologically inactive steroid 20alpha-dihydroprogesterone, but much of the progesterone that is given early in the luteal phase of the estrous cycle causes premature luteolysis by stimulating an increase in the release of PGF(2alpha) . The secretion of 20alpha-dihydroprogesterone may help to regulate progesterone production during the estrous cycle in goats.

Journal Article↗

PubMed1997

Changes in cholinergic neurons and failure in learning function after microsphere embolism-induced cerebral ischemia.

Central cholinergic neurons play an important role in learning and memory functions. The present study was undertaken to elucidate the pathological changes in learning function and acetylcholine metabolism of the cerebral cortex and hippocampus, following microsphere embolism in rats. Microspheres (48 microns) were injected into the right internal carotid artery of the rats. Learning function was determined using a passive avoidance task on the seventh day after the embolism. In the biochemical study, acetylcholine and choline contents, and choline acetyltransferase activity were measured in the cerebral cortex and hippocampus. Cortical acetylcholinesterase-containing fibers were quantitatively estimated in the embolized rat. Passive avoidance was impaired in the microsphere-embolized rat. Microsphere embolism decreased the acetylcholine concentration and choline acetyltransferase activity in the cerebral cortex and hippocampus. In the histochemical study, the length of cortical acetylcholinesterase-containing fibers was decreased, but cell density was unchanged in the ipsilateral hemisphere of the microsphere-embolized rat. The results suggest that microsphere embolism induces severe damage to cholinergic neurons, which may be related to the impairment of learning function in the ischemic brain.

Acetylcholine↗

PubMed1997

[A case of infant testicular tumor diagnosed ultrasonographically in the prenatal period].

We report a case of testicular tumor detected by ultrasonography during the prenatal period. Ultrasonography performed at 32 weeks of gestation showed that one testis was larger than the other. The right testis was markedly enlarged at 38 weeks of gestation. The heterogeneous echo pattern of the right testis suggested a testicular tumor. Right high orchiectomy was performed 3 months after birth. Pathological findings of the tumor were teratoma with mature and immature components according to the histological classification of testicular tumor. In Japan, this is the second case diagnosed in the prenatal period using ultrasonography.

Female↗

PubMed1996

Increasing gonadotropin-releasing hormone release by perifused hypothalamus from early to late anestrus in the beagle bitch.

An in vitro perifusion system was used to investigate pulsatile gonadotropin-releasing hormone (GnRH) release from hypothalamic fragments derived from beagle bitches at different stages of the estrous cycle. The spontaneous GnRH release from the excised tissue fragments that include the "mediobasal hypothalamic-preoptic area-suprachiasmatic nucleus units' was episodic throughout all stages of the estrous cycle with a significantly high release rate during late anestrus and late proestrus. The GnRH release rate and plasma levels of luteinizing hormone were positively correlated (r = 0.94, P < 0.01). These results suggest that during the course of anestrus in the bitch the GnRH release rate increases while the pituitary responds accordingly.

Animals↗

PubMed1996

Reversible suppression of pituitary-testicular function by a sustained-release formulation of a GnRH agonist (leuprolide acetate) in dogs.

Pituitary-testicular function was studied in 15 dogs following treatment with a sustained-release formulation of a GnRH agonist, leuprolide acetate (LA). Adult male dogs were treated with a single subcutaneous injection of microencapsulated LA (0.1 or 1 mg/kg). Treatment with LA at a dose of 1 mg/kg resulted in decreased (P<0.001) ejaculatory volume and disappearance of morphologically normal spermatozoa within 8 wk and the effect persisted for 6 wk, while the 0.1 mg/kg dose was not adequate to effect suppression of spermatogenesis. The larger dose treatment (1 mg/kg) caused a transient rise in plasma levels of LH and testosterone followed by a marked decline to below the normal level by 2 wk, the low levels being maintained for at least 5 wk, indicating a prolonged effect of LA treatment on pituitary-gonadal axis. Twenty weeks after treatment with LA, a complete return to normal spermatogenesis was observed. The full reversibility of spermatogenesis in the dog after LA treatment suggests that this peptide could be used as a reversible method of male contraception.

Journal Article↗

PubMed1995

Secretion of unconjugated estrone during pregnancy and around parturition in goats.

The secretion of unconjugated estrone and its production site in pregnant goats were investigated in vivo. The mean estrone concentration (n = 15) in the peripheral plasma increased gradually, being 83 pg/ml on Day 40 and 483 pg/ml on Day 140 after mating. The estrone concentration increased rapidly after Day 2 before partum, reaching a peak at parturition (2370 pg/ml), and falling to 171 pg/ml at Day 1 post partum. The concentrations of estrone from the umbilical vein and umbilical artery did not differ from that found in the maternal jugular vein, suggesting that the fetus does not take part in estrogen production. The estrone concentration from the uterine vein after the fetus was removed was higher than the concentrations found in the maternal jugular vein and umbilical artery. In the placental tissue, a high concentration of estrone (18157 pg per gram of wet tissue) was detected. These findings suggest that the main production site of unconjugated estrone is the placenta.

Journal Article↗

PubMed1995

Gallium uptake in cerebrotendinous xanthomatosis.

In a patient with cerebrotendinous xanthomatosis, a rare familial sterol storage disease, increased uptake of gallium-67 was observed in the tendon xanthomas. This is considered to have resulted from the tumour-like proliferation of histiocytic cells in the xanthomas. Abnormalities in the white matter of the cerebellum and the brain stem observed by X-ray computed tomography and magnetic resonance imaging were not detected by 67Ga scintigraphy, possibly due to the small size of the CNS lesions.

Brain↗

PubMed1995

Expression of insulin-like growth factor I mRNA in rat luteal tissue increases with functional regression of the corpus luteum.

The expression of insulin-like growth factor (IGF-I) messenger ribonucleic acid (mRNA) in rat corpora lutea (CL) was determined during the second half of pregnancy and early lactation, and the effect of prostaglandin F2 alpha on expression was examined during late pregnancy. Northern blot analysis revealed 4 species of transcripts in CL. Radioactivity of dot blots was measured directly for quantitative analysis of expression. The expression in CL increased during the second half of pregnancy, peaked around parturition, and declined thereafter. The injection of 1 mg of prostaglandin F2 alpha at 1300 and 1800 h on day 18 of pregnancy, which decreased plasma progesterone concentration, doubled luteal expression of IGF-I mRNA 1 day later. These results suggest that functional regression of the corpus luteum is correlated with the increased expression of IGF-I mRNA in luteal tissue in rats.

Animals↗

PubMed1995

Fetal survival in ovariectomized uterus-incised rats.

This study was undertaken to investigate whether the actions of ovarian hormones not related to the uterine physical state are essential for fetal survival during late pregnancy in rats. Bilateral ovariectomy and longitudinal incision in one uterine horn, which enabled exposure of the fetuses without detaching the placentas, were performed in each rat on day 14, 15, 16, 17, or 18 of pregnancy, and fetal survival was examined on day 21 or 3 days after the operation. Although almost none of the fetuses were maintained in the intact uterine horn, the fetal survival rate in the incised uterine horn increased linearly as the operation was performed during the later stage of pregnancy. In control animals, which received sham ovariectomy and the unilateral uterine incision, fetal survival rates were high in the intact and incised uterine horns. In the rats given bilateral ovariectomy and unilateral uterine incision on day 14 of pregnancy, progesterone substitution maintained fetuses in the intact and incised uterine horns examined on day 17. The results suggested that the actions of ovarian progesterone not related to the uterine physical state become less essential for fetal survival as pregnancy progresses to the late stage in rats.

Animals↗

PubMed1994

Mutations of the APC gene occur during early stages of gastric adenoma development.

Mutations of the adenomatous polyposis coli (APC) gene have recently been shown to play an important role in colorectal tumorigenesis. We investigated mutations of the APC gene in 30 gastric adenomas obtained endoscopically. Mutations of the APC gene were examined by polymerase chain reaction-single-strand conformation polymorphism analysis followed by sequencing of the polymerase chain reaction products. Mutations were detected in 20% (6 of 30) of gastric adenomas. In addition, deletion of the remaining allele that subsequently led to complete inactivation of the APC gene was confirmed in one-half (3 of 6) of the tumors with APC gene mutations. Sequencing analysis confirmed that the mutations resulted in truncation of the gene products or in an amino acid change. The incidences of mutations of the APC gene remained constant regardless of the size or degree of histological atypia. Our observations suggest that mutations of the APC gene, similarly to those in colorectal tumorigenesis, occur during the early stages of gastric adenoma development.

Adenoma↗

PubMed1994

Secretion of progesterone and 20 alpha-dihydroprogesterone during pregnancy in goats.

The relationships between the secretion of progesterone and 20 alpha-dihydroprogesterone and the sites of their production in pregnant goats were investigated. The progesterone concentration in the peripheral plasma increased after the goats mated, and was high from day 10 to day 140 of pregnancy. The 20 alpha-dihydroprogesterone concentration increased gradually from day 0 to day 140 after mating. The progesterone concentration before parturition decreased rapidly on day 1 prepartum, but the 20 alpha-dihydroprogesterone concentration remained high until the day of parturition and then began to fall. The ratio of progesterone to 20 alpha-dihydroprogesterone decreased and fell to less than one on day 1 prepartum. The plasma concentrations of progesterone in ovarian vein and of 20 alpha-dihydroprogesterone in the ovarian vein, umbilical vein, and umbilical artery were higher than those in the jugular vein. The ratio of progesterone to 20 alpha-dihydroprogesterone in placental tissue was less than one. These results suggest that in pregnant goats the main production site is the ovary for progesterone and the ovary and feto-placental unit for 20 alpha-dihydroprogesterone, and 20 alpha-dihydroprogesterone may take help to regulate progesterone production within the ovary and the feto-placental unit.

20-alpha-Dihydroprogesterone↗

PubMed1994

Secretion of progesterone and 20 alpha-dihydroprogesterone during the estrous cycle in goats.

The secretion of progesterone and 20 alpha-dihydroprogesterone (20 alpha-DHP) during the estrous cycle and the effects of prostaglandin F2 alpha (PGF2 alpha) and 20 alpha-DHP on the secretion of these two steroids during the midluteal phase in goats were studied. The mean progesterone concentration in the peripheral plasma was extremely low (< 0.01 ng/mL) on the day of estrus. The concentration increased to a maximum (7.80 ng/mL) on about day 10 after estrus, and decreased rapidly during the last 3 days of the cycle. The plasma concentration of 20 alpha-DHP also was low (0.86 ng/mL) on the day of estrus, but increased gradually after estrus and decreased gradually in the last 5 days of the cycle (to 3.22 ng/mL). The ratio of progesterone to 20 alpha-DHP was > 1 after day 2 of estrus, but decreased and fell to < 1 during the last 3 days of the cycle. An injection of 3 mg of PGF2 alpha decreased the secretion of progesterone within 30 min, but affected the secretion of 20 alpha-DHP little until 2 h. The ratio of progesterone to 20 alpha-DHP fell to < 1 after 24 h. Three of the five goats given such an injection came into estrus within 2 days, and the other two came into estrus within 3 days. An injection of 15 mg of 20 alpha-DHP did not affect progesterone secretion or the estrous cycle length. These results indicate that in the goat after estrus, there is much 20 alpha-DHP in the peripheral plasma. Progesterone may be catabolized to the biologically inactive steroid, 20 alpha-DHP, during luteolysis.

20-alpha-Dihydroprogesterone↗

PubMed1994

Epidermal growth factor--induced implantation and decidualization in the rat.

Effects of epidermal growth factor (EGF) on blastocyst implantation and experimentally-induced decidualization were examined in the rat. Intraluminal injection of EGF into each uterine horn induced implantation in the ovariectomized progesterone-treated delayed implanting rat in a dose-dependent manner. This induction was inhibited by indomethacin, an inhibitor of prostaglandin synthesis. Intraluminal injection of EGF on day 5 of pseudopregnancy elicited a greater decidual response when compared to the vehicle-injected contralateral uterine horn. These results suggest that EGF may play important roles in the process of implantation and decidualization in the rat.

Animals↗

PubMed1994

[Analysis of loss of heterozygosity (LOH) at the p53 and Rb suppressor genes in urinary bladder carcinoma].

Loss of heterozygosity (LOH) at the p53 and Rb genes, and its clinical correlations were examined in 58 urinary bladder carcinomas. DNA was extracted from formalin-fixed, paraffin-embedded tissues, and amplified by polymerase chain reaction (PCR). The LOH at p53 was examined by restriction fragment length polymorphism (RFLP), and the LOH at Rb by single-strand conformation polymorphism (SSCP). Among patients with urinary bladder carcinoma, 60.3% (35/58 patients) showed heterozygosity at p53 and LOH was detected in carcinoma in 60.0% (21/35), i.e., LOH in 61.9% (13/21) of superficial (< or = pT1) and in 57.1% (8/14) of muscular invasive carcinomas. Therefore, LOH at p53 was considered to occur before the beginning of muscular invasion. Except for the patients who died of other causes or were missed during the follow-up, 67.4% (29/43) showed 43.8% (7/16) died of carcinomatosis, but, only 15.4% (2/13) of the patients without p53-LOH died. The 5-year survival rate calculated by the Kaplan-Meier method was 76.9% in patients with heterozygosity at p53, and 25.1% in those with LOH at p53, being significantly lower at p < 0.05 in the former than in the latter. From an analysis of multiple bladder carcinomas, LOH at p53 occurred on the same allele in different tumors of the same bladder, suggesting the monoclonal origin of each tumor of multiple bladder carcinomas. On the other hand, 51.7% (30/58) of patients showed heterozygosity at Rb, and LOH was detected in 16.7% (5/30) of them, i.e., 6.3% (1/16) in superficial carcinoma and 28.6% (4/14) in muscular invasive carcinoma.

Adult↗

PubMed1993

Anterior sagittal anorectoplasty as a redo operation for imperforate anus.

Based on the idea of transsphincteric approach by Peña, we applied anterior sagittal anorectoplasty (ASARP) as a redo operation in 10 patients, who present moderate to severe fecal incontinence postoperatively. Those patients exhibited anal opening located anteriorly to the center of contraction of external sphincter muscles. Operation is begun with making a circumferential skin incision in the mucocutaneous junction around the anal opening, extending posteriorly along the median line to the center of the external sphincter muscles. Upon confirming the vertical muscle and the external sphincter muscles, the rectal tube, being dissected free, is mobilized backward to be placed at the center of the vertical muscles and enclosed by the muscle. After the operation, an improvement was noted in either clinical symptoms or scores, being particularly marked for incontinence and staining scores. Anorectal manometry and barium enema studies also showed a significant improvement. These results provide ample justification of ASARP as a redo operation for imperforate anus being worthwhile trying in properly selected patients with poor anorectal function following the primary operation.

Anus, Imperforate↗