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Biomedical subjects

Shigeki Yamaguchi

Publications and source records attributed to Shigeki Yamaguchi.

At least 19 recordsLinked to original sources
PubMed2007

NMDA receptor 2B subunit-mediated synaptic transmission in the superficial dorsal horn of peripheral nerve-injured neuropathic mice.

Previous research has shown that peripheral inflammation and peripheral nerve injury alter the properties of NMDA receptors in the spinal dorsal horn. However, there is no direct evidence that demonstrates the influence of peripheral nerve injury on NMDA receptor-mediated synaptic transmission in the spinal dorsal horn. Using whole cell tight-seal methods, NMDA receptor-mediated excitatory postsynaptic currents (NMDA EPSCs) were recorded from superficial dorsal horn neurons in adult mouse spinal cord slices. Peripheral nerve injury-induced changes in the pharmacological and electrophysiological properties of synaptic NMDA receptors were studied. The ratio of the amplitude of NMDA EPSCs to that of non-NMDA EPSCs was larger in nerve-ligated neuropathic mice than in sham-operated control mice. The decay phase of the NMDA EPSCs was slower in nerve-ligated neuropathic mice. The NR2B subunit-specific NMDA receptor antagonist ifenprodil (10 microM) reduced the amplitude of the NMDA EPSCs and shortened their decay phase. The sensitivity of NMDA EPSCs to ifenprodil was significantly larger in nerve-ligated neuropathic mice than in sham-operated control mice. Single-cell RT-PCR analysis performed on superficial dorsal horn neurons showed that the incidence of NR2A mRNA-expressing neurons was reduced in nerve-ligated neuropathic mice. This result, together with the electrophysiological findings, suggests that the subunit composition of the subsynaptic NMDA receptors in the superficial dorsal horn was altered by peripheral nerve injury. Pharmacological and electrophysiological changes observed in the present experiments might be the underlying causes of the hyperalgesia and allodynia induced by peripheral nerve injury and inflammation.

Animals↗
PubMed2006

[Morphological findings in MRI to be considered in perfoming spinal and epidural anesthesia].

The spinal cord and cauda equina move in the subarachnoid space by changing positions. The subarachnoid space is compressed from the dorsal side by epidural injection. At the end of gestation, the subarachnoid space is compressed from the ventral side by the engorged venous plexus. Idiopathic epidural lipomatosis is observed almost exclusively in the obese population. In the case of lipomatosis, the subarachnoid space is compressed by increased extradural fat around the thecal sac. We have had some severe cases of spinal canal stenosis in whom it is difficult to perform the spinal puncture. The authors showed some MR images and discussed morphological issues for spinal or epidural anesthesia.

Adult↗
PubMed2005

Omental flap in pancreaticoduodenectomy for protection of splanchnic vessels.

Intraabdominal bleeding, the most life-threatening complication following pancreaticoduodenectomy (PD), most often is associated with failure of a pancreaticojejunostomy anastomosis or with intraabdominal infection. We investigated whether placement of an omental flap around the splanchnic vessels in PD could reduce the occurrence of intraabdominal bleeding and other postoperative complications. One hundred consecutive patients who underwent PD at the authors' institution between January 2000 and October 2004 were enrolled in this prospective study. After dissection of the hepatoduodenal ligament, the major splanchnic arteries and the portal vein were covered by the omental flap. Preoperative condition, incidence of pancreatic fistula, intra-abdominal bleeding, other complications, treatment mortality, and hospital stay were analyzed for interrelationships. The frequency of pancreatic fistula (20%) differed little from those in previous reports. However, intraabdominal bleeding was observed in only 1 (1.0%) patient, who was considered to have too thin a flap. No intraabdominal abscess was encountered. No mortality or complications occurred in relation to the omental flap. Thus, wrapping an omental flap around dissected splanchnic vessels in PD reduced postoperative intraabdominal bleeding and infection, but failed to prevent pancreatic fistulas.

Adult↗
PubMed2005

Primary liver cancer with bidirectional differentiation into hepatocytes and biliary epithelium.

A 70-year old Japanese man with hepatitis B infection developed a 4.8-cm liver tumor in the right lobe. Computed tomographic findings suggested hepatocellular carcinoma or combined hepatocellular and cholangiocarcinoma. After right hepatectomy, the cut surface of the resected specimen showed a whitish tumor with indistinct borders. Microscopically, the tumor consisted of pleomorphic, eosinophilic cells forming thickened trabeculae, suggesting hepatocellular carcinoma, and also tumor cells forming glandular structures, suggesting adenocarcinoma. Cells comprising both the trabeculae and the glands were immunoreactive for cytokeratin (CK) 19. In some gland-forming cells, varying immunoreactivity for CK7 and carcinoembryonic antigen (CEA) was observed. In the cytoplasm of cells in the thickened trabeculae, hepatocyte paraffin (HepPar) 1 and alpha-fetoprotein (AFP) were focally reactive. Some of these tumor cells were also reactive for CK19. Accordingly, we concluded that this tumor was a combined hepatocellular and cholangiocarcinoma whose cells had undergone divergent differentiation into hepatocytes and biliary epithelium. Because the tumor expressed markers of both phenotypes, it may have originated from cells intermediate between hepatocytes and biliary epithelium. A few reported cases have shown similar histologic features.

Aged↗
PubMed2005

Spatial learning and long-term potentiation of mutant mice lacking D-amino-acid oxidase.

We evaluated the role of D-amino-acid oxidase on spatial learning and long-term potentiation (LTP) in the hippocampus, since this enzyme metabolizes D-amino-acids, some of which enhance the N-methyl-D-aspartate receptor functions. The Morris water maze learning and the LTP in the CA1 area of the hippocampal slice were observed in wild-type mice and mutant mice lacking D-amino-acid oxidase. The mutant mice showed significantly shorter platform search times in the water maze and significantly larger hippocampal LTPs than the wild-type mice. These results suggest that the abundant D-amino-acids in the mutant mouse brain facilitate hippocampal LTP and spatial learning.

6-Cyano-7-nitroquinoxaline-2,3-dione↗
PubMed2005

[Effectiveness of tacrolimus in a case of polymyositis].

We report a 57 year-old woman with polymyositis and interstitial pneumonia. With the steroid therapy alone, the decline of creatine kinase was insufficient and muscle strength was not improved. After the addition of tacrolimus 3 mg, serum creatine kinase declined, muscle strength was improved, and the dose of steroid could be tapered very smoothly. There was no remarkable change in the status of the interstitial pneumonia on the chest CT, but the vital capacity was improved. The improvement of the respiratory muscle strength might reduce the respiratory symptom and increase the daily activity in this case. It was possible that dose of steroid was tapered early with tacrolimus, and the side effect which accompanies long-term medication of steroids could be avoided. In polymyositis, tacrolimus is very useful medicine in the steroid-resistant case or in the case suffering from the side effect of steroids. There is possibility that tacrolimus becomes one of the choices of the treatment of polymyositis.

Female↗
PubMed2004

Procedures of choice for resection of primary and recurrent liver metastases from colorectal cancer.

Although liver resection offers the only realistic chance of cure for patients with liver metastases from colorectal cancer, no consensus exists as to the procedure of choice for managing these tumors. Data from 193 patients who underwent hepatectomy for liver metastases from colorectal cancer and 26 of 193 patients who underwent repeat hepatectomy for recurrent metastases were collected. The suitability of resection was evaluated retrospectively based on known risk factors for recurrence and patterns of recurrence. On multivariate analysis, a positive surgical margin (SM+) was the only risk factor for recurrence after the initial resection (p < 0.01). SM+ (p < 0.01) and nonanatomic resection (p < 0.05) that was less than a sectionectomy (p < 0.05) were risk factors for recurrence after repeat hepatectomy. Multiple tumors (four or more) was the most common pattern of recurrence after initial hepatectomy, and recurrence close to the line of resection was most common after repeat hepatectomy. Based on tumor doubling times, recurrence after initial hepatectomy seemed to originate from the primary colorectal lesion, whereas recurrence after repeat hepatectomy was derived from a hepatic metastasis. Retrospective analysis suggests that hepatectomy with clear surgical margins is more important than anatomic resection for initial hepatectomy, and at least sectionectomy is necessary for repeat hepatectomy.

Colorectal Neoplasms↗
PubMed2004

Patch clamp study of mouse glomus cells using a whole carotid body.

Some electrophysiological characteristics of mouse glomus cells (DBA/2J strain) were investigated using an undissociated carotid body. The carotid body with major carotid arteries was placed in a recording chamber, and glomus cells were visualized with a water immersion lens combined with an infrared differential interference video camera. Patch clamp experiments revealed that voltage-gated outward current, but not inward current, was easily observed in glomus cells. Pharmacological experiments and the kinetics of the current suggest that outward current is via delayed rectifier, A type, and large conductance calcium-activated K channels. Furthermore, K current was reversibly attenuated by mild hypoxia. The results suggest electrophysiological similarities of glomus cells among the cat, the rat, and the DBA/2J mouse. The method appears useful for physiological experiments.

Animals↗
PubMed2004

Metastatic tumor doubling time: most important prehepatectomy predictor of survival and nonrecurrence of hepatic colorectal cancer metastasis.

We determined the relative value of the metastatic colorectal cancer doubling time as a predictor of recurrence and survival after hepatectomy in comparison with other established predictors. Consecutive patients who underwent hepatic resection ( n = 144) for colorectal cancer liver metastases were studied retrospectively to identify factors that influence overall survival and recurrence in the remnant liver. Overall 5-year survival and nonrecurrence rates were 49.8% and 50.8%, respectively. By multivariate analysis, large liver tumors ( p = 0.038), p53 expression by the liver tumor (p = 0.011), and a short liver metastasis doubling time (< or = 45 days, p = 0.013) negatively affected survival; doubling times > 45 days (adjusted relative risk 0.06; p < 0.001) positively influenced disease-free survival. In patients with remnant liver recurrence, a short doubling time was associated with short disease-free intervals (7.3 +/- 6.2 months), multiple metastases (63.6%), and fewer attempts at repeat hepatectomy (22.7%). The doubling time determines tumor size and reflects the patient's immune and nutritional status. A short doubling time is the most reliable risk factor for multiple metastases, early recurrence, and poor prognosis. Further studies with a larger number of patients are needed to confirm this conclusion.

Adenocarcinoma↗
PubMed2004

A clinical and genetic study in a large cohort of patients with spinocerebellar ataxia type 6.

In order to clarify the clinical and genetic features of SCA6, we retrospectively analyzed 140 patients. We observed an inverse correlation between the age of onset and the length of the expanded allele, and also between the age of onset and the sum of CAG repeats in the normal and the expanded alleles. The ages of onset of four homozygous patients correlated better with the sum of CAG repeats in both alleles rather than with the expanded allele calculated from heterozygous SCA6 subjects. Clinically, unsteadiness of gait was the main initial symptom, followed by vertigo and oscillopsia, and cerebellar signs were detected in nearly 100% of the patients. In contrast, extracerebellar signs were relatively mild and infrequent. The results of neuro-otological examination performed in 22 patients suggested the purely cerebellar abnormalities of ocular movements in nature. There was a close relationship between downbeat positioning nystagmus (DPN) and positioning vertigo, which became more common in the later stage. We conclude that total number of CAG repeat-units in both alleles is a good parameter for assessment of age of onset in SCA6 including homozygous patients. In addition, clinical and neuro-otological examinations suggested that SCA6 is a disease with predominantly cerebellar dysfunction.

Age Factors↗