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T Aihara

Publications and source records attributed to T Aihara.

At least 55 records · Page 3Linked to original sources
PubMed1997

Stimulus-dependent induction of long-term potentiation in CA1 area of the hippocampus: experiment and model.

In the CA1 area of the hippocampus, the magnitude of long-term potentiation (LTP) depends not only on the frequency of applied stimuli, but also on their number. With a slice preparation using extracellular recording in the hippocampus CA1 of a guinea pig, we investigate the magnitude of LTP induced by electrical stimuli with a range of frequencies and the number of applied stimuli. We find that the magnitude of the saturated potentiation obtained with periodic stimuli largely depends on the frequency and is insensitive to the number of stimuli, once the saturation level has been obtained. Furthermore, we investigated nonperiodic stimuli and found that the magnitude of the saturated potentiation is also sensitive to the statistical correlation between successive interstimulus intervals, even when their average frequency is held constant. In order to explain the LTP dependence on these various experimental parameters, we propose a simple mathematical model for the induction of LTP. In the model, an exponentially decaying element released as a result of previous stimuli is coupled with a new stimulus to act as the potentiation force, and the magnitude of potentiation is determined by this potentiation force. We can determine the decaying time constant of this hypothetical element as a model parameter by fitting the model to the experimental data. The time scale is found to be of the order of 200 msc. A molecular or cellular factor with this decaying time constant is likely to be induced in LTP induction.

Animals↗
PubMed1997

The production and clearance of endothelin and its influence on kidney function after liver transplantation in rats.

To assess the involvement of endothelin-1 (ET-1) in rat liver allograft rejection, we evaluated ET-1 expression in tissues obtained from BN (RT1n) to BN rats (group 1), and DA (RT1a) to BN rats (group 2). The ET-1 levels in group 1, determined by radioimmunoassay, remained low in the serum, liver, and bile, but in group 2, they peaked on postoperative day (POD) 5 in the liver, kidney, bile, and urine, at 344 +/- 31.6 pg/gwet, 306 +/- 97.4 pg/gwet, 1008 +/- 258 pg/day, and 156 +/- 45 pg/day, respectively, whereas levels in the serum peaked on POD 7 at 38.7 +/- 13.1 pg/ml. In the portal vein (PV) ET-1 showed extremely high levels without statistical difference between groups 1 and 2, at 93.0 +/- 15.5, and 83.0 +/- 9.84 pg/ml on POD 7, respectively. However, in the suprahepatic vena cava (SHVC) and the abdominal aorta (AO), the ET-1 levels were statistically higher in group 2 compared to group 1 (P < 0.01). Immunohistochemical staining showed decreased staining of the liver and kidney in group 2 on POD 7. In conclusion, increasing levels of ET-1 were released from the liver and kidney during the early stage of rejection, resulting in the high ET-1 levels in these tissues, which were cleared promptly. However, an increased production of ET-1 was not observed in association with the release of ET-1.

Animals↗
PubMed1997

[Identification of predictive factors associated with recurrent restenosis after second percutaneous transluminal coronary angioplasty].

The predictive factors of a second restenosis after repeated percutaneous transluminal coronary angioplasty (PTCA) were investigated by review of the records of 100 consecutive patients who underwent second angioplasty for restenosis of the same site. PTCA was successful in 97 (97%) of these patients, but 38 patients (39%) developed a second restenosis (recurrent restenosis group) and 59 did not (no recurrent restenosis group). The clinical, angiographic and procedural factors at the second PTCA of the two groups of patients were compared. The major risk factors (hypertension, diabetes mellitus, hyperlipidemia) and type and morphology of the lesion (eccentricity, calcification, length, bend) at repeat PTCA did not differ significantly between the recurrent restenosis and no recurrent restenosis groups. The mean intervals from the initial to the second PTCA were significantly shorter in the recurrent stenosis group than in the no recurrent restenosis group (2.1 +/- 1.1 vs 3.4 +/- 1.3 months, p < 0.001). Sixteen (76%) of 21 patients had a second restenosis at an interval between the two PTCAs of < 3 months, compared with 22 (29%) of 76 patients with an interval of > or = 3 months (p < 0.001). Patients who undergo a second angioplasty procedure within 3 months from the previous procedure at the same site have a much higher risk of recurrent restenosis and these patients may benefit from an alternative therapeutic approach.

Aged↗
PubMed1996

Histologic characteristics of breast cancers with occult lymph node metastases detected by keratin 19 mRNA reverse transcriptase-polymerase chain reaction.

BACKGROUND: Amplification of keratin 19 mRNA (K19) by reverse transcriptase-polymerase chain reaction (RT-PCR) has been shown to be a sensitive method to detect occult breast cancer metastases in lymph nodes. METHODS: Axillary lymph nodes were obtained from 126 patients with breast cancer, and metastases in these lymph nodes were studied by both histologic examination and K19 RT-PCR. The patients were categorized into 3 groups according to the results of these 2 examinations, i.e., patients with 1) both histologically and K19 RT-PCR negative lymph nodes (metastases negative group [n = 91]); 2) histologically negative but K19 RT-PCR positive lymph nodes (occult metastases positive group [ n = 15]); and 3) histologically positive lymph nodes (metastases positive group [n = 20]). RESULTS: Various histologic parameters such as tumor size, histologic type, histologic grade, lymphatic invasion, vascular invasion, and estrogen receptor status were compared among these three groups. There were no significant differences among any of these histologic parameters between the metastases positive and occult metastases positive groups. Conversely, tumor size of the metastases positive (2.5 +/- 0.2 cm) and occult metastases positive (2.5 +/- 0.2 cm) groups was significantly (P < 0.05) greater than that of the metastases negative group (1.9 +/- 0.1 cm), and positivity of lymphatic vessel invasion in the former 2 groups (70% and 53%, respectively) was also significantly (P < 0.01) greater than that in the latter group (18%). CONCLUSIONS: These results demonstrate that histologic characteristics of breast cancers with occult metastases are similar to those of breast cancers with histologically detectable metastases.

Actins↗
PubMed1996

Phyllodes Tumor of the Breast: Pathology, Histogenesis, Diagnosis, and Treatment.

Phyllodes tumor of the breast is histologically unique in that it is composed of epithelial and stromal components. The histogenesis of this disease has remained largely unknown but recently we have obtained interesting information through clonal analysis, and have been able to show a difference in the histogenesis between phyllodes tumor and fibroadenoma. Elucidation of histogenesis would difinitely improve our understanding of the biological behavior of this disease and also help to establish the most appropriate treatment strategy. The pathology, histogenesis, diagnosis, and treatment of phyllodes tumor are reviewed in this paper. Our hypothesis on the histogenesis of this disease is also presented.

Journal Article↗
PubMed1996

Demonstration of monoclonal origin of human parotid gland pleomorphic adenoma.

BACKGROUND: Parotid gland pleomorphic adenoma is histologically comprised of epithelial and mesenchymal elements. It remains to be established whether this neoplasm arises from epithelial and mesenchymal elements, or solely from the epithelial element. METHODS: In an attempt to resolve this issue, we have conducted clonal analysis on five pleomorphic adenomas. The method for clonal analysis was based on the trinucleotide repeat polymorphism of the x-chromosome-linked androgen receptor gene and on random inactivation of this gene by methylation. The epithelial and mesenchymal elements were obtained separately from the paraffin sections of the pleomorphic adenomas using a microdissection technique and then subjected to clonal analysis. RESULTS: Clonal analysis revealed that both epithelial and mesenchymal elements were monoclonal. In addition, the same allele of the androgen receptor gene was inactivated in both elements in every case. CONCLUSIONS: It is unlikely that the epithelial and mesenchymal elements of different origin happen to inactivate the same allele of the androgen receptor gene in all five tumors. Rather, it is more reasonable to consider that these two elements have a common single cell origin.

Adenoma, Pleomorphic↗
PubMed1996

A malignant Triton tumor in the anterior mediastinum requiring emergency surgery: report of a case.

We report herein the case of a 17-year-old woman with von Recklinghausen's disease who was diagnosed as having a giant malignant Triton tumor located in the anterior mediastinum, which had adhered to the heart and the great vessels. An emergency operation was performed to relieve the tracheobronchial stenosis and congestive heart failure caused by the pressure of the tumor. Extracorporeal circulation was not required and the tumor could be excised only piece by piece. To our knowledge, this is the first report of a malignant Triton tumor being located in the anterior mediastinum.

Adolescent↗
PubMed1996

Hypomelanosis of Ito associated with neuroblastoma.

We report a patient with hypomelanosis of Ito associated with neuroblastoma. Though not previously reported, the association is plausible since both conditions are forms of "neurocristopathy".

Adrenal Gland Neoplasms↗
PubMed1996

Venopelvic fistula: a rare complication of hyperalimentation.

The prolonged placement of a hyperalimentation catheter via the left great saphenous vein resulted in obstruction of the inferior vena cava and in the formation of a venopelvic fistula. Administration of hyperosmolar fluid via this catheter might be the cause of this complication.

Arteriovenous Fistula↗
PubMed1996

Clonal analysis of precancerous lesion of hepatocellular carcinoma.

BACKGROUND & AIMS: It remains to be established whether precancerous lesion (dysplastic nodule) of hepatocellular carcinoma (HCC) is a neoplastic or hyperplastic lesion. Clonal analysis of this lesion was conducted to elucidate this important issue on histogenesis. METHODS: The method for clonal analysis was based on restriction fragment length polymorphism of the X chromosome-linked phosphoglycerokinase gene and on random inactivation of the gene by methylation. Clonal somatic mutations were also analyzed by DNA fingerprinting with two multilocus probes (33.6 and 33.15), and loss of heterozygosity was studied using five single-locus probes (MS1[1p33-p35], MS31[7p22-pter], MS43a[12q24.3-qter], MS8[5q35-qter], and g3[7q36-qter]). RESULTS: Clonal analysis by the phosphoglycerokinase gene-based method showed that all of the five dysplastic nodules and seven HCCs were monoclonal in origin. DNA fingerprinting showed clonal somatic mutations in six of 10 dysplastic nodules and in six of nine HCCs. Loss of heterozygosity was found in one dysplastic nodule (7p22-pter) and two HCCs (1p33-p35 and 12q24.3-qter). CONCLUSIONS: These results confirm monoclonality of HCC and show that hepatic precancerous lesion (dysplastic nodule) is not a hyperplastic but a neoplastic lesion, consisting of monoclonal cells with genetic alterations.

Aged↗
PubMed1996

Detection of gastric cancer micrometastases in lymph nodes by amplification of keratin 19 mRNA with reverse transcriptase-polymerase chain reaction.

A sensitive method for the detection of gastric cancer micrometastases in lymph nodes was developed. The method was based on amplification of keratin 19 mRNA by reverse transcriptase-polymerase chain reaction (RT-PCR). Keratin 19 RT-PCR showed that keratin 19 mRNA was expressed in all 12 gastric cancers, but not in any of 20 normal control lymph nodes, indicating that keratin 19 mRNA is a good target of RT-PCR for the detection of gastric cancer micrometastases in lymph nodes. Serial dilution studies of RNA extracted from gastric cancers against RNA extracted from control lymph nodes demonstrated that the detection sensitivity of the keratin 19 RT-PCR method was one cancer cell in 10(3)-10(5) lymph node cells. Detectability of lymph node metastases was compared between keratin 19 RT-PCR and conventional histological examination, using 100 lymph nodes obtained from 12 gastric cancer patients. Keratin 19 mRNA was detected in all of the seven lymph nodes which were histologically metastasis-positive. Of the 93 lymph nodes which were histologically metastasis-negative, 79 were found not to express keratin 19 mRNA but 14 were found to express keratin 19 mRNA, indicating that these lymph nodes contained micrometastases which could not be detected by histological examination. These results demonstrate that keratin 19 RT-PCR is a more sensitive method than histological examination for the detection of gastric micrometastases in lymph nodes.

Adult↗
PubMed1996

Clockwise whirlpool sign at color Doppler US: an objective and definite sign of midgut volvulus.

PURPOSE: To evaluate the clockwise whirlpool sign at color Doppler ultrasound (US) in the diagnosis of midgut volvulus. MATERIALS AND METHODS: Pediatric patients (160 boys, 76 girls; age range, 0 day to 14 years) with possible midgut volvulus underwent abdominal gray-scale US and color Doppler US. Midgut volvulus was diagnosed by recognition of the whirlpool sign (wrapping of the superior mesenteric vein and the mesentery around the superior mesenteric artery). If the whirlpool rotated clockwise with caudal movement of the transducer, the direction of the whirlpool was defined as clockwise. RESULTS: Color Doppler US showed a whirlpool sign that was clockwise in 12 of 13 patients with surgically confirmed midgut volvulus and counterclockwise in three patients without midgut volvulus. Sensitivity, specificity, and positive predictive value of clockwise whirlpool sign for midgut volvulus were 92%, 100%, and 100%. CONCLUSION: The clockwise whirlpool sign is diagnostic of midgut volvulus. Color Doppler US should be performed as an initial imaging study in children suspected of having midgut volvulus.

Adolescent↗
PubMed1996

Detection of breast cancer micrometastases in axillary lymph nodes by means of reverse transcriptase-polymerase chain reaction. Comparison between MUC1 mRNA and keratin 19 mRNA amplification.

Usefulness of MUC1 mRNA and keratin 19 mRNA as a target of reverse-transcriptase polymerase chain reaction (RT-PCR) was compared in the detection of breast cancer micrometastases in axillary lymph nodes. RT-PCR amplification of MUC1 mRNA and keratin 19 mRNA was conducted using total RNA samples. RT-PCR products were stained with ethidium bromide and analyzed by agarose gel electrophoresis. Expression of both MUC1 mRNA and keratin 19 mRNA was detected by RT-PCR in a breast cancer cell line (MRK) and in all the 23 primary breast cancers but not in the control lymph nodes obtained from patients with benign diseases. A serial dilution study of MRK cells against normal lymph node cells has shown that detection sensitivity of MUC1 RT-PCR and keratin 19 RT-PCR were 1/10(5) and 1/10(6) (cancer/lymph node cells), respectively. Sixty-three axillary lymph nodes were obtained from 23 patients with primary breast cancer, and metastases in each lymph node were investigated by histological examination (hematoxylin and eosin sections) and RT-PCR method. In all 10 lymph nodes, which were histologically metastasis-positive, both MUC1 mRNA and keratin mRNA were detected by RT-PCR. Of the 53 histologically negative lymph nodes, 3 (6%) and 5 (9%) lymph nodes were found to express MUC1 mRNA and keratin 19 mRNA, respectively, indicating the presence of micrometastases which could be detected by RT-PCR but not by histological examination. These results demonstrate the usefulness of both MUC1 RT-PCR and keratin 19 RT-PCR in the detection of breast cancer micrometastases in lymph nodes, and also indicate the superiority of keratin 19 RT-PCR over MUC1 RT-PCR because of its higher detection sensitivity.

Axilla↗