Search PubMed⌕ Search

Biomedical subjects

J Yamamoto

Publications and source records attributed to J Yamamoto.

At least 37 records · Page 2Linked to original sources
PubMed2002

CT imaging of intrabiliary growth of colorectal liver metastases: a comparison of pathological findings of resected specimens.

The objective of this study was to assess the usefulness of CT in the pre-operative evaluation of macroscopic intrabiliary tumour growth of colorectal liver metastases. 25 metastatic nodules of 18 patients who underwent an initial hepatectomy for colorectal liver metastasis were retrospectively evaluated. The CT appearance and pathological findings of the resected specimens were correlated. A number of unusual peritumoral features associated with intrabiliary tumour growth were detected by pre-operative CT. These were classified into three patterns: (1) thickened portal tract; (2) intrahepatic bile duct dilatation; and (3) a wedge-shaped area with enhancement. In 8 (32%) of the 25 nodules the portal tract was depicted as thicker than usual and these features were found proximal to the tumour in three instances, distal to the tumour in four instances, and both proximal and distal in one instance. All of the three intrabiliary tumours larger than 30 mm resulted in thickening of the portal tract. Intrahepatic bile duct dilatation was detected in association with 10 (40%) of 25 nodules. Bile duct dilatation was observed in more than one segment when intrabiliary tumour reached the hepatic hilus from the tumour. The presence of bile duct dilatation was not related to either the size of the tumour or the extent of intrabiliary tumour growth. An abnormally high density wedge-shaped area on contrast enhanced CT was another feature indicating intrabiliary tumour growth and was seen in association with four nodules. Such areas were seen in the liver parenchyma distal to the tumour on three occasions, or encompassing the tumour on one accasion. This wedge-shaped area appeared as a well demarcated dark red-brown region in the cut surface of the resected specimen. CT was useful for detecting the presence of intrabiliary tumour growth with these three patterns of radiological findings in patients with liver metastases from colorectal cancer

Aged↗
PubMed2001

Increased synchronization of cortical oscillatory activities between human supplementary motor and primary sensorimotor areas during voluntary movements.

In human, both primary and nonprimary motor areas are involved in the control of voluntary movements. However, the dynamics of functional coupling among different motor areas has not been fully clarified yet. Because it has been proposed that the functional coupling among cortical areas might be achieved by the synchronization of oscillatory activity, we investigated the electrocorticographic coherence between the supplementary motor and primary sensorimotor areas (SMA and S1-M1) by means of event-related partial coherence analysis in 11 intractable epilepsy patients. We found premovement increase of coherence between the SMA proper and S1-M1 at the frequency of 0-33 Hz and between the pre-SMA and S1-M1 at 0-18 Hz. Coherence between the SMA proper and M1 started to increase 0.9 sec before the movement onset and peaked 0.3 sec after the movement. There was no systematic difference within the SMA (SMA proper vs pre-SMA) or within the S1-M1, in terms of the time course as well as the peak value of coherence. The phase spectra revealed near-zero phase difference in 57% (20 of 35) of region pairs analyzed, and the remaining pairs showed inconsistent results. This increase of synchronization between multiple motor areas in the preparation and execution of voluntary movements may reflect the multiregional functional interactions in human motor behavior.

Adolescent↗
PubMed2001

A new staging system for mass-forming intrahepatic cholangiocarcinoma: analysis of preoperative and postoperative variables.

BACKGROUND: The objective of this study was to analyze the clinicopathologic variables and the postoperative outcome in patients with mass-forming intrahepatic cholangiocarcinoma (ICC) to identify important factors for predicting postresection prognosis. Although it has been reported that mass-forming ICC has a different etiology and biologic features compared with hepatocellular carcinoma (HCC), patients with ICC have been dealt with clinicopathologically in the same manner as patients with HCC. METHODS: Sixty patients who underwent hepatectomy for mass-forming ICC with curative intent between 1981 and 1999 were studied. Fourteen preoperative clinical and diagnostic parameters and 12 postoperative surgicopathologic parameters were analyzed. RESULTS: The rate of operative mortality in this patient cohort was 5%, and the overall 1-year, 3-year, and 5-year survival rates were 68%, 35%, and 29%, respectively, with a median survival of 19.6 months. A multivariate analysis revealed that independent negative prognostic factors were 1) hepatic regional lymph node metastasis, 2) multiple tumor presentation, 3) symptomatic tumor, and 4) the presence of vascular invasion. Using these factors, a new staging system was devised: Stage I disease was defined as a solitary tumor without vascular invasion, Stage II disease was defined as a solitary tumor with vascular invasion, Stage IIIA disease was defined as multiple tumors with or without vascular invasion, Stage IIIB disease was defined as any tumor with regional lymph node metastasis, and Stage IV disease was defined as any tumor with distant metastases. The Kaplan-Meier estimated 3-year survival rate and the median survival for each subgroup were 74% for patients with Stage I disease (median survival is the time when the cumulative survival rate of some patients' group declined to 50%; thus, the median survival could not be calculated in patients with Stage I disease because survival was 74% at the latest follow-up), 48% and 26.2 months for patients with Stage II disease, 18% and 16.8 months for patients with Stage IIIA disease, and 7% and 11.2 months for patients with Stage IIIB disease, respectively (P < 0.0001). None of the patients met the criteria for Stage IV disease. CONCLUSIONS: The current results support the use of a new staging system for patients with ICC that is simple and predicts well the differences in survival after patients undergo hepatic resection.

Adult↗
PubMed2001

Deformation of liquid crystal droplets under the action of an external ac electric field.

Deformation of liquid crystal droplets suspended in liquid polymer matrix under the action of external electric field was observed in dependence of ion concentration in such system. Experimental dependence of droplet elongation vs electric field demonstrates nonmonotonous character with increase of ion concentration. The theory that provides the basic agreement with experimental observation is developed.

Journal Article↗
PubMed2001

Transcriptional regulation of the murine acetyl-CoA synthetase 1 gene through multiple clustered binding sites for sterol regulatory element-binding proteins and a single neighboring site for Sp1.

Cytosolic acetyl-CoA synthetase (AceCS1) activates acetate to supply the cells with acetyl-CoA for lipid synthesis. The cDNA for the mammalian AceCS1 has been isolated recently, and the mRNA was shown to be negatively regulated by sterols in cultured cells. In the current study, we describe the molecular mechanisms directing the sterol-regulated expression of murine AceCS1 by cloning and functional studies of the 5'-flanking region of the AceCS1 gene. An AceCS1 promoter-reporter gene (approximately 2.1 kilobase pairs) was negatively regulated when sterols were added to the medium of cultured cells, and the promoter was markedly induced by co-transfection of a plasmid that expresses the transcriptionally active nuclear form of either sterol regulatory element-binding protein (SREBP)-1a or -2 in HepG2 cells. Sequence analysis suggested that the AceCS1 promoter contains an E-box, two putative CCAAT-boxes, eight sterol regulatory element (SRE) motifs, and six GC-boxes. Gel shift assays demonstrated that all eight SRE motifs bound purified SREBP-1a in vitro with similar affinity. Luciferase reporter gene assays revealed that sterol regulation was critically dependent on three closely spaced SRE motifs and an adjacent GC-box. However, mutation of two putative upstream CCAAT-boxes did not affect SREBP dependent activation. Electrophoretic mobility "supershift" analyses confirmed that both Sp1 and Sp3 bound to the critical GC-box. In addition, transfection studies in Drosophila SL2 cells demonstrated that SREBP synergistically activated the AceCS1 promoter along with Sp1 or Sp3 but not with nuclear factor-Y.

Acetate-CoA Ligase↗
PubMed2001

Observation of a pretransitional effect near a virtual smectic-A--smectic-C* transition.

Unusual softening of the layer compression modulus B has been observed near the phase boundary where the smectic-C* phase vanishes in a naphtalene-based liquid crystal mixture. From the systematic study of x-ray and layer compression measurements, this unusual effect is attributed to the pretransitional softening near a virtual smectic-A-smectic-C* phase transition in the smectic-A phase, which no longer appears on the thermoequilibrium phase diagram. This phenomenon is similar but not equivalent to supercritical behavior.

Journal Article↗
PubMed2001

Observation of a soft smectic liquid-crystal phase in a mixture showing V-shaped switching.

We present the experimental observation of a soft smectic liquid crystal phase in a three-component liquid crystal mixture reported to exhibit V-shaped switching. Unlike the layer compression modulus B of the usual smectic phase, B of the soft smectic phase has a peculiar temperature and frequency dependence. It was found that this characteristic feature is one of the main driving force to realize an ideal V-shaped switching.

Journal Article↗
PubMed2001

Transparent nematic phase in a liquid-crystal-based microemulsion.

Complex fluids are usually produced by mixing together several distinct components, the interactions between which can give rise to unusual optical and rheological properties of the system as a whole. For example, the properties of microemulsions (composed of water, oil and surfactants) are determined by the microscopic structural organization of the fluid that occurs owing to phase separation of the component elements. Here we investigate the effect of introducing an additional organizing factor into such a fluid system, by replacing the oil component of a conventional water-in-oil microemulsion with an intrinsically anisotropic fluid--a nematic liquid crystal. As with the conventional case, the fluid phase-separates into an emulsion of water microdroplets (stabilized by the surfactant as inverse micelles) dispersed in the 'oil' phase. But the properties are further influenced by a significant directional coupling between the liquid-crystal molecules and the surfactant tails that emerge (essentially radially) from the micelles. The result is a modified bulk-liquid crystal that is an ordered nematic at the mesoscopic level, but which does not exhibit the strong light scattering generally associated with bulk nematic order: the bulk material here is essentially isotropic and thus transparent.

Journal Article↗
PubMed2001

Cytocidal effect and DNA damage of nedaplatin: a mathematical model and analysis of experimental data.

PURPOSE: Cell cycle non-specific anticancer agents such as cis-diamminedichloroplatinum(II) are believed to depend linearly on the value of the area under the drug concentration time curve, which is supported by a mathematical model. However, the quantitative non-linear phenomena of both the cytocidal effect and DNA crosslink formation by cisdiammine(glycolato)platinum (nedaplatin) have been shown in vitro. Therefore, we developed a new mathematical model to explain these phenomena. METHODS: We assumed that nedaplatin enters intracellular fluid from medium through simple diffusion to form DNA crosslinks that kill cells. We developed a mathematical model to represent this assumption using differential equations that we then solved using an original computer program. The calculated results were compared with the experimental data. RESULTS: The drug's simple diffusion rate constant, the DNA crosslink formation rate constant, and the crosslink-dependent cell death rate constant in the model were 1.8 x 10(-14) (l h-1), 1.6 x 10(8) (l mol-1/2 h-1), 5.45 x 10(1) (mol-1), respectively. The model fits the experimental results statistically. The model also demonstrated theoretical proof that continuous exposure at a low dose was superior to the short exposure at a high dose seen in published experimental data. CONCLUSIONS: We developed a mathematical model to describe the non-linear pharmacodynamic effect of nedaplatin in vitro. This model may provide a novel drug infusion procedure for cancer patients.

Antineoplastic Agents↗
PubMed2001

Cytocidal effect and DNA damage of nedaplatin in vitro by simulating pharmacokinetic parameters.

PURPOSE: The pharmacodynamic effects of cis-diammine(glycolato)platinum (nedaplatin, 254-S) in vitro have been reported, but the dosage and exposure time in vitro have not always been based on clinical observations of the drug's actions in vivo. Regardless of the actual exposure conditions used, the effect of cell-cycle nonspecific anticancer agents such as nedaplatin is believed to depend on the area under the drug concentration-time curve (AUC). In this study, we evaluated the pharmacodynamics of nedaplatin in vitro, especially in relation to its AUC dependency, in terms of cell survival and DNA crosslinking. METHODS: BG-1 human ovarian cancer cells were treated with various concentrations of nedaplatin to simulate the pharmacokinetics of administration in a clinical setting. The BG-1 cells were exposed to nedaplatin dissolved in medium containing serum using constant concentration conditions, either high (maximum 7.69 mg/l) or low (average 1.33 mg/l). These concentrations were based on doses used in clinical studies. We then adjusted the exposure conditions in vitro to simulate the elimination of the drug from serum in vivo as follows: T1/2 alpha 1.20 h and T1/2 beta 2.70 h. The AUC values were set at 4, 8, 16, 25 and 40 mg.h/l for all exposure conditions. A colony-formation assay for the surviving fraction and an alkaline-elution assay for DNA crosslink measurement were done for the pharmacodynamic evaluation with comparison on the basis of the AUC value. RESULTS: Exposure to a low concentration for a long time was the most effective of the exposure conditions at the same AUC value. The greater the AUC value, the higher the crosslink index under all exposure conditions. This index tended to increase particularly after exposure to the low concentration. The natural logarithm of the surviving fraction (Y') was a linear function of the crosslink index regardless of the drug-exposure condition: ln(Y') = -87.2x + ln(5.79), R2 = 0.89. The threshold cytocidal effect was associated with a crosslink index of 0.02. CONCLUSION: There was a strong correlation between the cytocidal effect of nedaplatin and DNA crosslink formation. The cytocidal effect and DNA crosslinking in vitro depended on the exposure conditions used to define the AUC. Therefore, a new pharmacokinetic-pharmacodynamic model for nedaplatin must be constructed to investigate the most effective administration procedure in vivo.

Antineoplastic Agents↗
PubMed2001

New lesions detected by intraoperative ultrasound during liver resection for hepatocellular carcinoma.

During liver resection for hepatocellular carcinoma (HCC), it is not uncommon for examinations by intraoperative ultrasound (IOUS) to detect small new lesions that were not found by preoperative examinations. Although a differential diagnosis is critical, it has not yet been established if IOUS is useful for this purpose with such small lesions. A total of 90 new lesions detected by IOUS in 79 liver resections were analysed. IOUS was performed on all of these cases and the features were recorded. The histologic characteristics of these 90 new lesions were checked by needle biopsy and their relations to the clinical data were analyzed. The IOUS pattern of the lesion was hypoechoic in 36 cases, hyperechoic in 49 and mosaic in 5. A total of 24 HCC lesions were detected and the incidences of malignancy for each type were 30.6%, 18.4% and 80.0%, respectively. Multiple regression analysis revealed that the IOUS features of the new lesions were the only significant factors in predicting the histology. IOUS should be mandatory in liver resection for HCC because it is useful for finding new lesions and might contribute to prediction of the histologic features.

Adult↗
PubMed2001

Increased lymphoid MxA expression in acute asthma exacerbation in children.

BACKGROUND: Although the association between acute asthma exacerbation and viral infection has been well documented, virus identification rates vary. It has recently been reported that the expression of MxA protein in lymphocytes, inducible by type I interferons, can serve as a sensitive marker for viral infection in the host. The objective was to determine the contribution of viral infection to precipitation of asthma attacks in children. METHODS: We studied 186 asthmatic children, aged 0-12 years, over a 1-year period to evaluate MxA protein levels in peripheral blood lymphocytes by using a flow cytometric analysis in whole blood. RESULTS: Of all the subjects, 80 (47%) exhibited significantly elevated levels of MxA expression in lymphocytes, presumably indicating the states of viral infection. The association of viral infections with acute asthma exacerbation seemed to be marked in younger children: enhanced MxA expression was seen in 73.3% of infants (aged 0-1 year), 49.5% of toddlers (aged 2-5 years), and 26% of schoolchildren (aged 6-12 years). Seasonal changes in the frequency of viral infection associated with deterioration were also observed. CONCLUSIONS: Flow cytometric assay of MxA protein expression in whole blood appears to be an easy and useful method to evaluate viral infections in acute asthma exacerbation.

Acute Disease↗
PubMed2001

An autopsy case of the schizophrenic 32 years after lobotomy.

An autopsy case is reported here of a 69-year-old patient with schizophrenia, who was known retrospectively to have had a prefrontal lobotomy 32 years previously. The patient was diagnosed as schizophrenic at the age of 24 and the lobotomy was undertaken 13 years later. The patient was recently found outside in a dehydrated condition and admitted to a general hospital, where he died of respiratory failure. Bilateral cystic lesions were found in the deep white matter of the frontal lobe. The cyst walls consisted of glial fibrous tissues, and severe demyelination with axonal destruction was diffusely observed in the white matter of the frontal lobe. In the thinner frontal cortex without arcuate fibers (U fibers) close to the cavities, cytoarchitectural abnormalities were observed. In the thalamic nuclei marked retrograde degeneration and astrocytic gliosis were observed. The detailed neuropathological findings of a lobotomized schizophrenic brain are reported here. It is proposed that one should be reminded of a lobotomized brain if bilateral cysts are found.

Aged↗
PubMed2001

Treatment strategy for small hepatocellular carcinoma: comparison of long-term results after percutaneous ethanol injection therapy and surgical resection.

This comparative study was conducted to clarify the efficacy of percutaneous ethanol injection (PEI) and surgical resection in the treatment of small hepatocellular carcinomas (HCC). Thirty-nine patients treated by PEI and 58 who underwent hepatic resection for small HCC (smaller than 3 cm and 3 or less in number) during the same period were enrolled. The surgery group included more patients with large and multiple bilobar nodules than the PEI group. The histological differentiation of the treated tumors became worse in the surgery patients than in those treated by PEI. On the other hand, the PEI group included more patients with a poor hepatic reserve, according to Child-Pugh grading, the ICG test, and the serum total bilirubin value. The 1-, 3-, and 5-year overall survival rates were almost identical between the 2 cohorts (100%, 82.1%, and 59.0%, respectively, in the PEI group; 96.6%, 84.4%, and 61.5%, respectively, in the surgery group) (P =.96). During the follow-up period, 33 of 39 (85%) and 41 of 58 (71%) patients developed tumor recurrence after PEI and surgery, respectively. Cumulative 1-, 3-, and 5-year tumor-free survival rates in the PEI group were 63.4%, 30.3%, and 9.7 %, whereas those in the surgery group were 75.5%, 44.7%, and 25.7%, respectively (P =.10). Our overall findings show that local therapy can achieve an actual 5-year survival rate of around 60% for patients with small HCC with the proper selection of treatment. A prospective randomized comparative trial is required to settle this longstanding issue.

Adult↗
PubMed2001

Estimating the prognosis of hepatic resection in patients with metastatic liver tumors from colorectal cancer with special concern for the timing of hepatectomy.

BACKGROUND: The effect of the time interval between colorectal and liver resection for metastatic lesions on the patient's survival remains controversial. Pretreatment classification for predicting the prognosis of this disease has not yet been reported. METHODS: Nine clinical factors revealed by preoperative examinations, intraoperative screening before liver resection, and resection margin were examined in 304 patients who underwent hepatic resections for metastatic colorectal carcinoma. The patients were divided according to the timing of hepatectomy and both tumor number and maximum diameter to devise a staging system. RESULTS: Tumor number and maximum tumor size were significant prognostic factors in the metachronous hepatectomy group, and resection margin was significant in the synchronous group. The following staging system was proposed: stage I, n < or = 3 and diameter < 5 cm in the metachronous hepatectomy group (n = 86); stage II, n < or = 3 and diameter > or = 5 cm in the metachronous hepatectomy group (n = 46); and stage III, n > or = 4 and diameter > 5 cm in the metachronous group and the synchronous hepatectomy group (n = 144). CONCLUSIONS: The current study revealed that the factors that influenced the patient's prognosis were different between the synchronous and metachronous groups. It may be useful to develop a staging system that considers this difference.

Adult↗
PubMed2001

Abdominal pain in patients with resectable pancreatic cancer with reference to clinicopathologic findings.

Abdominal and/or back pain is one of the most common symptoms in patients with pancreatic cancer. However, the cause of the pain and the clinicopathologic features of patients with pain have not been fully elucidated. We retrospectively determined the factors related to preoperative abdominal and/or back pain in 95 patients with resectable pancreatic cancer. Pancreatic tumor size, invasion of the intrapancreatic nerves, invasion of the anterior pancreatic capsule, and lymph node metastasis were determined to be variables related to the pain. Pancreatic tumor size, invasion of anterior pancreatic capsule, and lymph node metastasis were also variables significantly correlating to pain intensity. Survival also correlated with pain intensity: the median survival periods were 29 months in patients without pain, 19 months in those with mild pain, and 9 months in those with severe pain who required analgesics. Larger pancreatic tumors, invasion of the intrapancreatic nerves, and invasion of the anterior pancreatic capsule may cause abdominal and/or back pain in patients with resectable pancreatic cancer. This study also suggests clinical implications of the pain intensity as a prognostic factor in patients with resectable pancreatic cancer.

Abdominal Pain↗
PubMed2001

Physical growth and retinopathy in preterm infants: involvement of IGF-I and GH.

GH and IGF-I are important for physical growth. We measured serum levels of these factors in preterm infants. The study population (n = 81) was divided into three groups according to the gestational age. We evaluated differences in serum GH and IGF-I levels among groups with regard to physical growth and development of retinopathy of prematurity. Serum GH levels in extremely preterm infants born at <28 wk of gestational age were significantly higher than levels in those born between 28 and 34 wk at 1 and 2 mo of age. In contrast, serum IGF-I levels in extremely preterm infants remained low, whereas those in the other two groups gradually increased. Evaluation of the effects of GH and IGF-I on physical growth in very low birth weight infants (<1500 g) showed that IGF-I concentrations were positively related to physical growth for several months after birth, whereas no relationship was observed between GH and physical growth. Multivariate analysis demonstrated that high GH concentration at 1 mo of age was significantly associated with development of severe retinopathy of prematurity. In conclusion, persistent low serum IGF-I levels may explain the slow physical growth during neonatal life, and exposure of high GH may cause, at least in part, severe retinopathy of prematurity in preterm infants.

Disease Progression↗