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T Kameda

Publications and source records attributed to T Kameda.

At least 37 records · Page 2Linked to original sources
PubMed2000

The concentric structure of the developing gut is regulated by Sonic hedgehog derived from endodermal epithelium.

The embryonic gut of vertebrates consists of endodermal epithelium, surrounding mesenchyme derived from splanchnic mesoderm and enteric neuronal components derived from neural crest cells. During gut organogenesis, the mesenchyme differentiates into distinct concentric layers around the endodermal epithelium forming the lamina propria, muscularis mucosae, submucosa and lamina muscularis (the smooth muscle layer). The smooth muscle layer and enteric plexus are formed at the outermost part of the gut, always some distance away from the epithelium. How this topographical organization of gut mesenchyme is established is largely unknown. Here we show the following: (1) Endodermal epithelium inhibits differentiation of smooth muscle and enteric neurons in adjacent mesenchyme. (2) Endodermal epithelium activates expression of patched and BMP4 in adjacent non-smooth muscle mesenchyme, which later differentiates into the lamina propria and submucosa. (3) Sonic hedgehog (Shh) is expressed in endodermal epithelium and disruption of Shh-signaling by cyclopamine induces differentiation of smooth muscle and a large number of neurons even in the area adjacent to epithelium. (4) Shh can mimic the effect of endodermal epithelium on the concentric stratification of the gut. Taken together, these data suggest that endoderm-derived Shh is responsible for the patterning across the radial axis of the gut through induction of inner components and inhibition of outer components, such as smooth muscle and enteric neurons.

Animals↗
PubMed2000

[Should arterial grafts be used for urgent coronary artery bypass surgery?].

It is not clear whether arterial grafts should be used for emergency or urgent coronary artery bypass grafting (CABG) because harvest of internal thoracic arteries (ITAs) is not easy under urgent conditions and the blood flow through the ITAs may be inadequate immediately after CABG. The purpose of this study was to assess whether the use of arterial grafts in urgent CABG affects the outcome adversely or not. Twenty consecutive patients who underwent urgent CABG within 48 hours following coronary angiography at our institute between July 1991 and October 1998 were reviewed. The patients who underwent CABG with associated procedures were excluded. Among these subjects, 11 patients received at least one arterial graft. Only 1 patient died of subarachnoidal hemorrhage, and the hospital mortality rate was 5.0%. According to the overall survival rate, cardiac-death-free rate, and cardiac-event-free rate, the long-term outcome was much better in the patients with arterial grafts than those with saphenous vein grafts alone. We suggest that arterial grafts should be used even for urgent CABGs since the use of arterial grafts may not affect operative results adversely and will confer better long-term benefits.

Arteries↗
PubMed2000

Expression of gonadotropin and activin receptor messenger ribonucleic acid in human ovarian epithelial neoplasms.

Activin receptors (ActRs) and gonadotropin receptor mRNA expression were investigated in 18 human ovarian epithelial neoplasms. Northern blot analysis showed the presence of 3.0-kb type Ia ActR, 6.0- and 3.0-kb type IIa ActR, and 5.0-kb type IIb ActR mRNA transcripts in total RNA prepared from the cancer tissues. One carcinoma showed two major transcripts of a follicle-stimulating hormone receptor (FSH-R) gene, 4.1 and 2.4 kb, whereas the other two carcinomas showed two major transcripts of the luteinizing hormone/human chorionic gonadotropin receptor (LH-R) gene, 5.4 and 2.4 kb. These results were further analyzed by studying the corresponding PCR-amplified FSH and LH-R cDNA obtained by reverse transcription of total RNA. Expression of FSH-R mRNA was confirmed in about half of the cancer tissues. The size of the FSH-R reverse transcription-PCR product was the same as in normal ovarian follicles. Similarly, expression of LH-R mRNA was also detected in about half of the cancers. Normal ovaries and cancer tissues were homogenized, and activin concentrations were measured in extracts. Activin levels in normal ovarian tissue were around 0.59 +/- 0.01 ng/mg protein (mean +/- SE; n = 5), and activin production was detected in every cancer tissue, except one--serous adenocarcinoma. The findings in this study demonstrated that activin and ActRs are present in and synthesized by human ovarian epithelial neoplasms. Thus, activin seems to be available as an autocrine/paracrine factor in epithelial neoplasms and may contribute to the expression of FSH-R, although the roles of activin and gonadotropin in tumorigenesis has yet to be defined.

Activin Receptors↗
PubMed1999

Control of the expression of luteinizing hormone receptor by local factors in rat granulosa cells.

To identify the mechanisms underlying the hormone-dependent induction and maintenance of luteinizing hormone receptor (LH-R) in rat granulosa cells, the effect of follicle-stimulating hormone (FSH) and local factors on the LH-R mRNA levels were studied. LH-R mRNA levels of the cells incubated with FSH decreased rapidly after medium removal, and readdition of FSH with the fresh medium did not restore these levels. On the other hand, 8-bromoadenosine 3,5-cyclic monophosphate significantly enhanced the expression of LH-R mRNA after medium removal, while the level of LH-R mRNA was lower than that of the cells replaced by original medium including FSH. In addition, the incubation with 8-Br-cAMP produced dose-dependent responses for LH-R mRNAs and enhanced the activity of 1379 bp of the LH-R 5'-flanking region, while the level of LH-R mRNA decreased 3 days after medium removal. Further studies were undertaken to assess the role of factors in maintaining the LH receptor once induced by FSH. Since FSH and cAMP increase follistatin production in granulosa cells, we examined the effect of follistatin on LH-R induction in the presence of activin and FSH. Activin induced LH-R in the presence of FSH significantly, and follistatin antagonized this effect in a dose-dependent manner. However, insulinlike growth factor-I (IGF-I) induced LH-R mRNA in the presence of FSH even after medium change. IGF-I might be one of the important factors that act in the medium to maintain LH-R levels in granulosa cells.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed1999

Regulation of cAMP responsive element binding modulator isoforms in cultured rat ovarian granulosa cells.

A pituitary glycoprotein hormone FSH stimulates ovarian granulosa cells to induce ovarian follicular development. In this study we identified rat ovarian genes that were rapidly induced by FSH in the cultured rat granulosa cells by means of subtraction cloning. Complementary DNA clones encoding cAMP responsive element binding modulator (CREM) were identified as one of the FSH inducible genes. Northern blotting and reverse transcription and polymerase chain reaction (RT-PCR) analyses revealed that only the repressor type of CREM gene products, ICER (inducible cAMP early repressor) isoforms, were induced by FSH treatment in cultured rat granulosa cells. The induction of ICER by FSH was mimicked by reagents known to increase intracellular cAMP levels, indicating that the induction is through cAMP and protein kinase A signal transduction system. Induction of ICER was also confirmed as the protein levels. Electrophoretic mobility shift assay of granulosa cell extracts with a radiolabeled double stranded oligonucleotide corresponding to somatostatin cAMP responsive element also revealed that only the ICER proteins were induced by FSH treatment, whereas levels of CREM proteins were nearly constant regardless of the FSH treatment. Our present study demonstrates that FSH-induced and cAMP-mediated induction and attenuation of transcriptional responses by CREM gene products may be a key mechanistic component for the granulosa cell differentiation and proliferation.

Animals↗
PubMed1999

Control of FSH receptor mRNA expression in rat granulosa cells by 3',5'-cyclic adenosine monophosphate, activin, and follistatin.

FSH is required to maintain FSH and LH/hCG receptors at elevated steady-state levels after receptor induction. Although this function of FSH is mediated by cAMP, how cAMP level is related to the maintenance of gonadotropin receptors is unknown. To investigate cAMP's effect on changes in the levels of FSH receptor mRNAs in rat granulosa cells, total RNA from cells was prepared and analyzed by Northern blots. Incubation with 8-Br-cAMP for 24 h produced a dose-related increase in FSH receptor mRNA in granulosa cells of DES-primed immature rats. On the other hand, 8-Br-cAMP, washed at 24 h, exerted inverse dose-related effects on FSH receptor mRNA levels at 96 h. The addition of 1 mM cAMP resulted in higher levels of FSH receptor mRNA than that induced by 0.2 mM cAMP at 24 h, while 0.2 mM cAMP is as effective as 1-2 mM cAMP for the induction of FSH receptor mRNA at 96 h. To further analyze cAMP's role in the production of activin in granulosa cells, we measured activin levels in the culture medium after the addition of 8-Br-cAMP. The levels of activin A were suppressed by the addition of 8-Br-cAMP in a dose-dependent manner. In addition, the procedure by which 8-Br-cAMP was removed after 24 h incubation showed that the level of activin in the medium increased after medium change. With regard to the actions of activin A on gonadotropin receptors, our laboratory has demonstrated that activin A increases the levels of FSH receptor mRNAs. Therefore, cAMP has a negative effect on FSH receptor expression by suppressing the activin level. Since follistatin production is up-regulated by cAMP in this system, we examined the effect of follistatin on FSH receptor mRNA level, which is induced by activin and FSH. Cotreatment with follistatin (0-100 ng/ml) and activin (50 ng/ml) in the presence of FSH (30 ng/ml) caused a significant reduction in FSH receptor mRNA levels induced by activin. Based on these observations, it is possible that cAMP has both stimulatory and inhibitory effects on the expression of gonadotropin receptors, and the overall influence of cAMP on their expression might be determined by the integration of such opposing effects.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed1999

Etidronate (EHDP) inhibits osteoclastic-bone resorption, promotes apoptosis and disrupts actin rings in isolate-mature osteoclasts.

Bisphosphonates, therapeutic reagents against tumoral bone diseases (Paget's disease or osteoporosis), are potent inhibitors of bone resorption. The mechanisms by which they directly act on mature osteoclasts remain unclear. Using a recently developed technique for isolation of highly purified mammalian mature osteoclasts, we demonstrated that etidronate [ethane-1-hydroxy-1,1-diphosphonate (EHDP), 1-hydroxy-1,1-ethylidenebisphosphonate], inhibited directly osteoclastic bone-resorbing activity by pit assay. In addition, EHDP also directly induced apoptosis and disrupted actin rings in osteoclasts. The data support previous data on non-purified osteoclasts and results in vivo.

Actins↗
PubMed1999

The effect of follicle-stimulating hormone (FSH) on the expression of FSH receptor in cultured rat granulosa cells.

The acquisition of FSH receptors during folliculogenesis is believed to be a key event in the subsequent development of the follicle. The regulation by FSH of FSH receptor expression and function were further studied using cultured granulosa cells of diethylstilbestrol (DES)-primed immature rats. Incubation of rat granulosa cells with FSH led to a reduction in FSH receptor levels for a short time (6 h), followed by an increase in FSH receptor levels that reached maximum of around 150% of the initial level within 3 days after the addition of FSH. FSH stimulation caused a reduced cAMP response to subsequent FSH treatment and a time course experiment demonstrated that this response was detectable within 30 min of exposure to FSH and reached a plateau after 4 h to 24 h. The recovery of FSH responsiveness in cAMP production of granulosa cells was seen after 48 h of FSH-free interval. Treatment with forskolin (FSK) enhanced the effect of subsequent FSH on the production of intracellular cAMP. Treatment with PMA did not affect the response to subsequent FSH treatment. These data showed that the FSH is essential for the suppression of the FSH receptor function in the adenylyl cyclase pathway. Desensitization of cellular response to continuous agonist stimulation may occur because of changes in the numbers of FSH receptor, as well as changes in the functional properties of the effector system.

Animals↗
PubMed1999

Effects of coronary artery bypass grafting using internal mammary arteries for diabetic patients.

OBJECTIVES: In our institute, internal mammary arteries (IMAs) have been preferred for coronary artery bypass grafting (CABG) in diabetic patients. The purpose of this study was to evaluate the influence of diabetes and IMA grafting on survival after CABG. BACKGROUND: The influence of diabetes on the results of CABG is not well documented, and there is controversy about whether the use of IMAs conveys greater survival benefits to diabetic patients. METHODS: A total of 420 consecutive patients who underwent CABG from April 1990 to July 1998 were reviewed; 211 of these patients had diabetes mellitus at the time of surgery. Internal mammary artery grafts have been used with increasing frequency, and bilateral IMAs have been used when possible since 1993. Internal mammary artery grafts were used in 164 nondiabetic patients (78%) and in 155 diabetic patients (73%). Seventy-eight nondiabetic patients and 74 diabetic patients received bilateral IMA grafts. RESULTS: The postoperative mortality was 2.4% in the nondiabetic and 2.8% in the diabetic group. With regard to postoperative complications, diabetic patients had a significantly higher rate of chest wound infection (p < 0.05), irrespective of whether IMAs were used or not. The use of bilateral IMAs did not increase the risk of chest wound infection in nondiabetic or diabetic patients. Overall survival curve, cardiac death-free curve and cardiac event-free curve were not affected adversely by diabetes, and in diabetic patients, CABG with saphenous veins alone conveyed significantly (p < 0.01) less long-term benefit than did CABG with at least one IMA graft. CONCLUSIONS: It was suggested that IMA grafts should be preferred in diabetic patients.

Adult↗
PubMed1999

Developmental patterning in chondrocytic cultures by morphogenic gradients: BMP induces expression of indian hedgehog and noggin.

BACKGROUND: The maturation of chondrocytes is essential for endochondral bone formation. The Indian Hedgehog (Ihh) gene is expressed in prehypertropic chondrocytes and has been proposed to regulate chondrocyte maturation. While such secretary factors as PTHrP and BMP are thought to be involved in Ihh expression, the mechanism of the restricted expression of Ihh is not clear. RESULTS: Using primary chondrocytes, we have developed here a modified micromass culture (MM-C) system that allows the formation of concentration gradients of secreted factors, expressed either endogenously or retrovirally, from each of plural micromass cultures on a single plate. Using this system, we determined that chondrocytes create the inhibitory micro-environment, partly dependent on PTHrP secretion, for the Ihh expression. We also showed that retrovirally induced BMP-2 induces the expression of both Ihh and Noggin (encoding the BMP-inactivating protein), and we further present evidence that a negative-feedback loop involving Noggin might account for the precise localization of BMP signalling for Ihh induction. CONCLUSION: These results suggest that the expression of the Ihh gene in cartilage is regulated by several mechanisms that include the secretion of inhibitory factors (including PTHrP) and the negative-feed back loop formed by BMPs and Noggin.

Animals↗
PubMed1999

Protective effect of thiopental against cerebral ischemia during circulatory arrest.

BACKGROUND: One of the most important disadvantages of the hypothermic circulatory arrest technique is the limited time allowable for circulatory arrest. Thiopental is usually used to protect the brain against ischemic injuries. However, it remains uncertain how well thiopental reduces cerebral metabolism. We investigated its effectiveness by comparing outcomes after different doses. METHODS: Fifty patients who underwent aortic arch repair with hypothermic circulatory arrest had their records reviewed. Electroencephalograms (EEG) and partial pressures of oxygen in the internal jugular vein (PjO2) were monitored. Following confirmation of total disappearance of EEG activity, 15 or 30 mg/kg thiopental was administered before circulatory arrest Th duration of circulatory arrest ranged from 16 to 77 min. RESULTS: Hospital mortality rate was 10% and 4 (8%) patients developed neu-rologic complications, but 3 of them were transient. After thiopental infusion, PjO2 increased significantly from 430 to 499mmHg (p <0.01), indicating that thiopental reduces cerebral oxygen consumption. The rate of the decrease in PjO2 during circulatory arrest was slower with the higher thiopental dose, suggesting that thiopental lowered the cerebral metabolic rate of oxygen during circulatory arrest. CONCLUSION: It appears that thiopental has protective effects against cerebral ischemia under profound hypothermia.

Adult↗
PubMed1999

Effect of prolactin on the expression of luteinizing hormone receptors during cell differentiation in cultured rat granulosa cells.

Chronic and transient hyperprolactinemia has been associated with luteal phase dysfunction. Recently, evidence has emerged to suggest that elevated PRL may exert its antigonadal effects through reducing available ovarian LH receptors. We have now examined the influences of PRL on LH receptor induction in cultured granulosa cells. Basal specific LH binding was negligible and remained unchanged in response to treatment with PRL by itself. Whereas treatment with FSH produced, as expected, a substantial increase in specific LH binding, concurrent treatment with PRL resulted in no significant change during the first 4 days of culture, followed by a significant decrease in LH binding on days 5 and 6 as well as an approximately 50% inhibition of FSH effect on day 6. Scatchard plot analysis showed that concurrent treatment with PRL resulted in inhibition of the granulosa cell LH binding capacity, whereas no difference could be detected in the binding affinity of LH to its receptor. Treatment with 8-bromo-cAMP produced a significant increase in specific LH binding; concurrent treatment with PRL (30 ng/ml) produced a significant attenuation of 8-bromo-cAMP action. In addition, treatment with FSH increased the intracellular accumulation of cAMP, and concurrent treatment with PRL did not result in inhibition of the FSH action, as assessed by the generation of intracellular cAMP. Taken together, these findings suggest that the ability of PRL to interfere with FSH action with regard to the induction of LH receptors is exerted at sites distal to those involved in cAMP generation. The effect of PRL on LH receptor messenger RNA (mRNA) levels was not significant during the increase in receptors, whereas after the maximal level of receptor expression was reached, the effect of PRL was apparent. Cotreatment with FSH (30 ng/ml) and increasing doses of PRL inhibited the levels of FSH-induced LH receptor mRNA in a dose-dependent manner, whereas PRL did not inhibit the effect of FSH on the FSH receptor mRNA. To investigate the hormonal regulation of the 5'-flanking region, we analyzed the effect of FSH on 1379 bp of LH receptor promoter in rat granulosa cells. Treatment with FSH (1-100 ng/ml) significantly enhanced the activity of 1379 bp of the LH receptor 5'-flanking region in dose-dependent manner. Treatment with 30 ng/ml PRL alone did not significantly influence the activity of the LH receptor promoter and did not affect the increased promoter activity induced by FSH. In addition, the rates of LH receptor mRNA gene transcription assessed by nuclear run-on transcription assay increased by the addition of FSH and were not affected by the addition of PRL in the presence of FSH. These data showed that PRL might not effect LH receptor gene transcription in the regulation of LH receptor mRNA. Next, an attempt was made to determine the effect of PRL on LH receptor mRNA stability by measuring the decay of LH receptor mRNA under conditions known to inhibit transcription. However, inhibitors of transcription were found to have a stabilizing effect on the LH receptor mRNA, thus potentially masking the effect of PRL. According to the expression of LH receptor mRNA, PRL might not affect the maximum level induced by FSH, but thereafter the maximum levels of LH receptor mRNA decreased faster than those of the control. Therefore, it may be possible that PRL acts to stimulate labile LH receptor mRNA-destabilizing factors.

Animals↗
PubMed1999

[A case report of coronary artery bypass grafting using hypothermic circulatory arrest technique for the severely calcified ascending aorta].

Severe calcification of the ascending aorta makes coronary artery bypass grafting (CABG) complicated since aortic cross-clamping may induce cerebral embolization of aortic debris or aortic dissection. Furthermore, there are problems that the distal aortic occlusion becomes incomplete and proximal anastomosis between the ascending aorta and saphenous veins becomes impossible. CABG for a 56 year-old male with severely calcified ascending aorta was successfully conducted using hypothermic circulatory arrest technique. His right internal thoracic artery was bypassed to LAD under fibrillatory arrest and then his right gastroepiploic artery was bypassed to the distal portion of RCA under hypothermic circulatory arrest. There was no complication and left ventricular ejection fraction improved from 16% to 38% postoperatively.

Aorta↗
PubMed1998

Unstable retrovirus mutants with acquired transforming activity: rapid changes in the number of repeats of a specific junD polynucleotide segment.

We have previously reported that the non-transforming jun D (wild type) gene can acquire transforming activity through spontaneous mutations when it is replicated through avian replication-competent retrovirus vectors in chicken embryo fibroblasts. In two of these spontaneous mutants, T1 and T2, which were isolated from proviral DNA in the same transformed cell clone, a specific 48 bp polynucleotide segment of the jun D coding sequence was tandemly repeated three and five times, respectively. We report here that the number of direct repeats in these mutants rapidly changes (mostly decreases) in the context of either RSV-based replication-competent or MLV-based replication-defective retroviruses, most likely during the process of reverse transcription, while these mutations are stable in the cellular chromosome. We also show that the growth conditions of the infected culture modulate the proportions of polymorphic proviral populations in the infected culture. We finally discuss the possible molecular mechanisms that generate genetic diversity in these amplification mutants.

Animals↗
PubMed1998

Calcium-sensing receptor in mature osteoclasts, which are bone resorbing cells.

Bone metabolism consists of osteoblast-mediated bone formation coupled to osteoclastic resorption of bone. Osteoclastic bone resorption plays an important role in normal skeletal development and the maintenance of its integrity throughout life. Although osteoclastic activity is thought to be under the control of feedback regulation by extracellular cations, the molecular mechanism of detecting extracellular cations within the bone microenvironment remains to be clarified. In the present study we showed by reverse transcription-polymerase chain reaction and Northern blot analysis that cultured mature osteoclasts express the calcium-sensing receptor (CaSR) mRNA. The nucleotide sequence of rabbit osteoclast CaSR was approximately 90% identical to that of CaSR cDNA from human, bovine, and rat parathyroid glands. Moreover, the activity of osteoclastic bone resorption, as determined by pit formation, was regulated by extracellular calcium ion as well as its agonists that are known to act through the CaSR. We conclude that CaSR, homologous to that identified in parathyroid glands, is present in mature osteoclasts and calcium ion released from bone may directly regulate osteoclastic bone resorption.

Animals↗
PubMed1998

Suppression of cellular transformation by glucocorticoid receptor mutants.

Glucocorticoid receptor (GR) has been shown to suppress activator protein 1 (AP-1)-mediated transcription by several molecular mechanisms. We previously showed that activation of endogenous AP-1 is essential for cellular transformation induced by oncogenes, such as v-src and c-Ha-ras. In the present study, we have analyzed whether high levels of GR expression suppress cellular transformation caused by these oncogenes. To eliminate the ligand effects that induce the transcriptional stimulation via glucocorticoid response elements, we constructed two GR mutants: CD-GR-1, lacking the COOH-terminal portion, including both the ligand and Hsp90-binding domains, and tau1TDCD-GR-1, a derivative of CD-GR-1 lacking the tau1 transactivation domain. When these GR mutants were expressed in chicken embryonic fibroblasts by retroviral vectors, they translocated into the nucleus without addition of glucocorticoid to the culture medium, and they suppressed cellular transformation caused by v-src and c-Ha-ras, as well as by c-fos and c-jun. Cellular transformation by v-myc was not suppressed by these mutants. Such suppressive effects of these GR mutants have a very similar oncogene dependency to that of dominant-negative mutants of AP-1. This suggests that GR can be altered to suppress cellular transformation by inhibiting endogenous AP-1 activity without activating glucocorticoid response elements.

Animals↗