PubMed Health⌕ Search

Biomedical subjects

Y Toh

Publications and source records attributed to Y Toh.

At least 19 recordsLinked to original sources
PubMed2006

Analysis of cadmium in food by multiple prompt gamma-ray spectroscopy.

The Cd concentration in food is a public concern related to the human health. In order to remove Cd-polluted food, the development and validation of a rapid and sensitive method of Cd analysis is required. By applying the multiple gamma-ray detection method to prompt gamma-ray analysis (PGA), the influence from nuclei which emit only one prompt gamma-ray at a time at every neutron capture reaction can be reduced, therefore the quantification limit of Cd is improved significantly. The limit of Cd contained in rice in the case of MPGA was evaluated, and under our proposed experimental conditions, it may be possible to quantify Cd content in rice to within 0.2 ppm in 10 min.

Cadmium↗
PubMed2005

A case of esophageal small cell carcinoma with multiple liver metastases responding to chemotherapy with irinotecan plus cisplatin.

We report a case of small cell esophageal carcinoma (SCEC) with multiple liver metastases treated with some success by chemotherapy with irinotecan (CPT-11) plus cisplatin (CDDP). Radiologic and endoscopic examination of a 75-year-old man with multiple liver tumors disclosed a 4.0-cm type 2 tumor in the middle third of the esophagus. An endoscopically obtained biopsy specimen was diagnosed as undifferentiated small cell carcinoma. Multiple liver metastases were confirmed but lymph node metastases and distant metastases other than those in the liver were not detected. After six courses of chemotherapy with CPT-11 plus CDDP, the primary lesion showed complete response and liver metastases showed partial response. However, because all lesions almost immediately relapsed or progressed, arterial infusion chemotherapy for liver metastases and radiation for the primary lesion were given as second-line treatment. The primary lesion showed complete response with radiation. Arterial infusion chemotherapy prevented the progression of liver metastases once, but the patient died of liver failure at last. No distant lesions including metastatic lymph nodes were confirmed over the course of his illness, and the patient survived for a year after first diagnosis. Although the prognosis of SCEC is quite unfavorable due to highly aggressive behavior, a better prognosis is possible with effective chemotherapy and second-line treatment is important in improving prognosis.

Aged↗
PubMed2004

Morphological and physiological identification of medulla interneurons in the visual system of the tiger beetle larva.

The morphology of visual interneurons in the tiger beetle larva was identified after recording their responses. Stained neurons were designated as either medulla or protocerebral neurons according to the location of their cell bodies. Medulla neurons were further subdivided into three groups. Afferent medulla neurons extended processes distally in the medulla neuropil and a single axon to the brain through the optic nerve. They received their main input from stemmata on the ipsilateral side. Two distance-sensitive neurons, near-by sensitive and far-sensitive neurons, were also identified. Atypical medulla neurons extended their neurites distally in the medulla and proximally to the brain, as afferent medulla neurons, but their input patterns and the shapes of their spikes differed from afferent neurons. Protocerebral neurons sent a single axon to the medulla neuropil. They spread collateral branches in the posterior region of the protocerebrum on its way to the medulla neuropil. They received main input from stemmata on the contralateral side. Medulla intrinsic neurons did not extend an axon to the brain, and received either bilateral or contralateral stemmata input only. The input patterns and discharge patterns of medulla neurons are discussed with reference to their morphology.

Animals↗
PubMed2002

Isotopic ratio of 129I/127I in seaweed measured by neutron activation analysis with gamma-gamma coincidence.

129I is a long-lived (1.6 x 10(7) y) radionuclide that is produced in nature as the result of spontaneous fission of heavy elements and reaction of xenon with cosmic rays. Recently, however, artificial sources from nuclear power plants and nuclear test explosions have become a significant component of environmental radioactive iodine. Coincidence gamma-ray detection using Ge detectors makes it possible to simultaneously resolve the numerous gamma-rays produced by neutron activation. In this study, the coincidence gamma-ray detection technique was combined with neutron activation analysis to determine the radioactive iodine composition of seaweed. The ratio of 129I/127I in this common Japanese food item collected from the Ibaraki prefecture has been derived without the need for radiochemical purification. The isotopic ratio of 129I/127I in Kajime algae is 3.5(5) x 10(-10).

Gamma Rays↗
PubMed2001

Responses of medulla neurons to illumination and movement stimuli in the tiger beetle larvae.

Intracellular responses of medulla neurons (second-order visual interneurons) have been examined in the tiger beetle larva. The larva possesses six stemmata on either side of the head, two of which are much larger than the remaining four. Beneath the cuticle housing the stemmata an optic neuropil complex occurs consisting of lamina and medulla neuropils. Response patterns of medulla neurons to illumination and moving objects varied from neurons to neurons. For movement stimuli black discs and a black bar were moved in the rostro-caudal direction above the larva. Comparison of responses to the discs and the bar suggested a spatial summation of responses in some neurons, and tuning to small objects in some neurons. The majority of neurons responded to objects moving at heights of 10 mm and 50 mm with the same discharge pattern. A few neurons, however, showed distance sensitivities responding with an increase of spike discharges to moving objects only at either of the two heights. Such distance sensitivities still remained in one-stemma larvae, three of the four stemmata being occluded. These data are discussed in relation to distinct visual behavior of the larva and with special reference to perception of the hunting range.

Animals↗
PubMed2001

Characterization of mouse metastasis-associated gene 2: genomic structure, nuclear localization signal, and alternative potentials as transcriptional activator and repressor.

We characterized the mouse metastasis-associated gene 2 product (mmta2), which is a homolog of the metastasis-associated gene 1 product (MTA1). We revealed that the mmta2 gene spanned approximately 10 kb and was separated into 18 exons. The transcription start site of mmta2 was located 377 bp upstream from the putative initiation codon. The subcellular location of the mmta2 protein was the nucleus, and nuclear localization signals were identified in the region between amino acids 456 and 497. To obtain data on the transcription-regulating potential of mmta2, various constructs containing different portions were fused to the GAL4 DNA-binding domain. The entire mmta2 protein repressed the transcription of the reporter genes, whereas treatment with a histone deacetylase inhibitor, trichostatin A (TSA), led to recovery from the repression and to transcriptional activation. However, the N terminus of mmta2 activated transcriptional activity in the absence of TSA. These results suggest that mmta2 has the potential to both repress and activate gene transcription and that its transcription repression activity might be related to histone deacetylation.

3T3 Cells↗
PubMed2001

Peripheral representation of antennal orientation by the scapal hair plate of the cockroach Periplaneta americana.

Arthropods have hair plates that are clusters of mechanosensitive hairs, usually positioned close to joints, which function as proprioceptors for joint movement. We investigated how angular movements of the antenna of the cockroach (Periplaneta americana) are coded by antennal hair plates. A particular hair plate on the basal segment of the antenna, the scapal hair plate, can be divided into three subgroups: dorsal, lateral and medial. The dorsal group is adapted to encode the vertical component of antennal direction, while the lateral and medial groups are specialized for encoding the horizontal component. Of the three subgroups of hair sensilla, those of the lateral scapal hair plate may provide the most reliable information about the horizontal position of the antenna, irrespective of its vertical position. Extracellular recordings from representative sensilla of each scapal hair plate subgroup revealed the form of the single-unit impulses in response to hair deflection. The mechanoreceptors were characterized as typically phasic-tonic. The tonic discharge was sustained indefinitely (>20 min) as long as the hair was kept deflected. The spike frequency in the transient (dynamic) phase was both velocity- and displacement-dependent, while that in the sustained (steady) phase was displacement-dependent.

Animals↗
PubMed2001

Behavioural responses of the tiger beetle larva to moving objects: role of binocular and monocular vision.

The larva of the tiger beetle Cicindela chinensis is an ambushing hunter with a body length of 15-22 mm that lives in a tunnel in the ground. It ambushes prey, keeping its head horizontal at the opening of the tunnel. When prey approaches the tunnel, the larva jumps to snap at it. When an object moves beyond its jumping range (approximately 15 mm), however, the larva quickly withdraws deep into the tunnel. These responses are mediated by two of six pairs of stemmata. How does the larva judge the hunting range using such a simple visual system? A previous study suggested that both binocular and monocular vision are used for distance estimation. Range estimation by binocular vision was further confirmed in the present behavioural observations: larvae jumped towards objects beyond the normal hunting range when virtual images of such distant objects were formed close to the larva using prisms or a narrow window. A possible mechanism involved in range estimation by monocular vision was also examined in behavioural experiments. The depth of the image in the retina appears to play a role in distance estimation because a larva with one functional stemma, the other stemmata being occluded, changed its response to a very distant object from an escape to a predatory jump when a concave lens was placed above its head. Two alternative ideas, based on optical and morphological data, are proposed to explain this behavioural change by the one-stemma larvae. First, as for myopic people, the larva might see clearly only objects that are close. Second, an infinitely distant object might produce a focused image only on the central part of the retina, whereas an object within hunting range (<15 mm) might do so on surrounding regions of the retina. The latter idea implies that the region of the retina at which the larva perceives a clear image is concerned with which type of behaviour is released, a predatory jump or an escape. We conclude that visual information about hunting range in the tiger beetle larva is extracted both peripherally by the spatial pattern of image clarity and centrally by binocular vision.

Animals↗
PubMed2000

Tumor metastasis-associated human MTA1 gene: its deduced protein sequence, localization, and association with breast cancer cell proliferation using antisense phosphorothioate oligonucleotides.

Using differential cDNA library screening techniques based on metastatic and nonmetastatic rat mammary adenocarcinoma cell lines we previously cloned and sequenced the metastasis-associated gene mta1. Using homology to the rat MTA1 gene we cloned the human MTA1 gene and found it to be overexpressed in a variety of human cell lines. We found a close similarity between the human MTA1 and rat MTA1 genes, as shown by 88% and 96% identities of the nucleotide and predicted amino acid sequences, respectively. Both genes encode novel proteins that contain a proline-rich region (SH3 binding motif), a putative zinc finger motif, a leucine zipper motif, and five copies of the SPXX motif often found in gene regulatory proteins. Using Southern blot analysis, the MTA1 gene was found to be highly conserved among all species examined; and using Northern blot analysis, MTA1 transcripts were found in virtually all cell lines of human origin that were analyzed, including melanoma and breast, cervix and ovarian carcinoma cells and normal breast epithelial cells. However, the expression level of the MTA1 gene in a normal breast epithelial cell was approximately 50% of that found in rapidly growing breast adenocarcinoma cell lines and an atypical mammary cell line. Experimental inhibition of MTA1 protein expression using antisense phosphorothioate oligonucleotides resulted in growth inhibition of human MDA-MB-231 breast cancer cells with relatively high expression of the MTA1 gene. Furthermore, the MTA1 protein was localized in the nuclei of cells transfected using a mammalian expression vector containing the full-length MTA1 gene. The results suggest that the MTA1 protein may function in cellular signaling processes important in the progression and growth of cancer cells, possibly as a nuclear regulatory factor.

Amino Acid Sequence↗
PubMed2000

The role of antennal hair plates in object-guided tactile orientation of the cockroach (Periplaneta americana).

The searching behavior of blinded cockroaches was examined under unrestrained conditions, in an arena, and on a treadmill. When cockroaches searching in a circular arena touched a stationary object (metal pole) with their antennae, they frequently approached the object more closely, and then climbed up it. Similar orientation behavior was observed in tethered animals in open loop conditions, walking on a Styrofoam ball. In these restrained cockroaches, a single antenna sufficed to distinguish the angular positions of an object, in the horizontal plane (0 degrees, 45 degrees, and 90 degrees). A group of mechanosensitive hairs on the basal segment of the antenna (scapal hair plate) appears to play a major role in antennal object detection in the horizontal plane, as gauged by shaving off these scapal hair plates. In unrestrained cockroaches, shaving the scapal hair plate increased the time needed to approach an object. Under tethered conditions, the ability to turn towards and to establish antennal contact with a test object was significantly impaired.

Animals↗
PubMed2000

Suppression of manganese superoxide dismutase augments sensitivity to radiation, hyperthermia and doxorubicin in colon cancer cell lines by inducing apoptosis.

Increased expression of manganese superoxide dismutase (Mn-SOD), one of the mitochondrial enzymes involved in the redox system, has been shown to diminish the cytotoxic effects of several anti-cancer modalities, including tumour necrosis factor-alpha, ionizing radiation, certain chemotherapeutic agents and hyperthermia. We asked if Mn-SOD is a potential target to augment the sensitivity of cancer cells to various anti-cancer treatments and for this we established stable Mn-SOD antisense RNA expressing cell clones from two human colon cancer cell lines, HCT116 (p53 wild-type) and DLD1 (p53 mutant-type). Suppression of Mn-SOD in HCT116 was accompanied by an increased sensitivity to radiation, hyperthermia and doxorubicin, as compared with findings in controls. The mitochondrial permeability transition, as measured by a decrease of the mitochondrial transmembrane potential was more intensely induced by radiation in HCT116 antisense clones than in the control, an event followed by a greater extent of DNA fragmentation. Apoptosis was also induced by hyperthermia more intensely in HCT116 antisense clones than in the control. On the other hand, DLD1 antisense clones did not exhibit any enhancement of sensitivity to any of these treatments. These data support the possibility that inhibition of Mn-SOD activity renders colon cancer cells with wild-type p53 susceptible to apoptosis induced by radiation, hyperthermia and selected anti-cancer drugs. Therefore, we suggest that Mn-SOD could be a target molecule to overcome the resistance to anti-cancer treatments in some colon cancer cells carrying wild-type p53.

Adenocarcinoma↗
PubMed2000

p53 expression in squamous dysplasia associated with carcinoma of the oesophagus: evidence for field carcinogenesis.

Squamous epithelial dysplasia is often observed multifocally in the cancerous oesophagus and is presumably considered to be a pre-cancerous lesion. A mutation of the p53 tumour suppressor gene is commonly identified in oesophageal cancer and dysplasia. p53 mutations can be anticipated immunohistochemically. In order to confirm the biological and clinical significance of p53 expressions in oesophageal field carcinogenesis, immunostaining for p53 in cancerous and multifocal precancerous lesions from resected human oesophagus was systematically investigated, while paying special attention to the contiguity of these lesions. Lesions expressing p53 were detected in 46.5% (20 of 43 lesions) of the invasive carcinoma, and in 51.0% (46 of 90 lesions) of the carcinoma in situ, and in 51.4% (92 of 179 lesions) of the dysplasia. Next, the p53 expression in dysplasia was compared with that in carcinoma for the same case. 37 of 39 (94.8%) dysplasias contiguous to p53-positive carcinomas also expressed p53 (P<0.0001). On the other hand, the isolated dysplasias without contiguity to p53-positive carcinomas, only expressed p53 protein in 44.0% (11 of 25 lesions). No significant correlations were found between the p53 staining and either the clinicopathological features or prognosis. Discordant p53 alterations, such as those seen in cancerous and isolated precancerous lesions, may thus demonstrate further evidence for a multicentric or field carcinogenesis of the human oesophagus.

Aged↗
PubMed2000

Reduced expression of manganese superoxide dismutase mRNA may correlate with invasiveness in esophageal carcinoma.

Little is known about the expression and antioxidant function of manganese superoxide dismutase (Mn-SOD) in esophageal squamous cell carcinoma. To determine the significance of Mn-SOD in esophageal squamous cell carcinomas, Mn-SOD mRNA expression was examined in 45 esophageal squamous cell carcinomas and the corresponding normal mucosal tissues by reverse transcription-polymerase chain reaction. The tumor/normal (T/N) ratio of 45 patients with esophageal carcinoma was calculated, and the data were clinicopathologically analyzed. The T/N ratio of Mn-SOD mRNA expression was less than 0.5 in 11 (32.4%) of 34 esophageal carcinoma cases without any preoperative treatments, while none of 11 cases who underwent preoperative chemotherapy showed a T/N ratio of <0.5 (p < 0.05). There was an inverse correlation between the Mn-SOD expression level and the degree of venous invasion (p < 0.05) as well as lymphatic invasion (p < 0.05). Furthermore, poorly differentiated squamous cell carcinoma showed significantly lower Mn-SOD mRNA expression levels than well differentiated carcinoma (p < 0.05). Our results suggest that Mn-SOD mRNA was frequently reduced in esophageal carcinoma when compared to the normal mucosa and the reduced expression levels of Mn-SOD mRNA may lead to an accumulation of superoxide radicals in conjunction with the increased invasiveness of esophageal carcinoma.

Carcinoma, Squamous Cell↗
PubMed2000

Expression of MTA1, a metastasis-associated gene with histone deacetylase activity in pancreatic cancer.

MTA1 has been identified as a metastasis-promoting gene, and its gene expression is correlated with serosal invasion and lymph node metastasis in the gastrointestinal and esophageal cancers. We examined MTA1 mRNA expression levels in 13 cell lines and 23 tumor tissues of pancreatic cancer by quantitative reverse transcription polymerase chain reaction. MTA1 mRNA expression was found in all the cell lines, however its levels were not correlated with the metastatic pontential of each cell line representing hematogenous distant metastasis. In the pancreatic cancer tissues, the overexpression of MTA1 mRNA (tumor/normal ratio >/=1) was observed in 12 out of 23. Pancreatic cancer tissues overexpressing MTA1 mRNA (T/N ratio >/=1) tended to have higher incidence of lymph node metastasis. These results together with previous findings in the gastrointestinal and esophageal cancers suggest that MTA1 might be involved in the progression, particularly in lymph node metastasis of pancreatic cancer.

Carcinoma↗
PubMed2000

Overexpression of manganese superoxide dismutase mRNA may correlate with aggressiveness in gastric and colorectal adenocarcinomas.

The expression or activity of manganese superoxide dismutase (Mn-SOD) is reduced in a variety of malignant tumors and Mn-SOD may act as a new type of tumor suppressor gene. On the other hand, increased expression of Mn-SOD can diminish the cytotoxic effects of several anticancer modalities, including tumor necrosis factor alpha, ionizing radiation, certain chemotherapeutic agents and hyperthermia. Although Mn-SOD expression and its role in various cancers are intensely studied, little is known about its function in gastrointestinal carcinomas. To examine the expression level and significance of Mn-SOD in gastrointestinal carcinomas, Mn-SOD mRNA expression was examined in 53 gastric carcinoma and 38 colorectal carcinoma by reverse transcription-polymerase chain reaction and was compared with those in the corresponding normal mucosal tissues. The tumor/normal (T/N) ratio was calculated and the data were clinicopathologically analyzed. The average T/N ratios of Mn-SOD mRNA expression in gastric and colorectal carcinomas were 2.19 and 3. 72, respectively. Clinicopathologic analyses revealed positive correlation between the Mn-SOD expression level and venous invasion in both gastric and colorectal carcinomas (p<0.05 and p<0.05, respectively). Furthermore, the colorectal carcinoma with lymph node metastasis showed significantly higher Mn-SOD expression than those without it (p<0.05). Our results suggest that Mn-SOD mRNA overexpression can occur in gastric and colorectal carcinomas and may be related to increased aggressiveness.

Adenocarcinoma↗
PubMed2000

Molecular analysis of a candidate metastasis-associated gene, MTA1: possible interaction with histone deacetylase 1.

We previously identified a novel rat candidate metastasis-associated gene, mta1, based on its differential expression in highly metastatic cells compared to nonmetastatic cells. Furthermore, we showed that overexpression of its human counterpart, MTA1, correlated with the invasiveness or lymph node metastasis of gastric, colorectal and esophageal carcinomas. The aim of this study was to analyze the domains of the MTA1 and investigate the function(s) of this protein. Structural analysis revealed that the MTA1 protein contained a GATA-like zinc-finger domain, a leucine zipper domain, a SANT domain similar to the DNA binding domain of myb-related proteins, a src homology 3-binding domain important in protein-protein interactions, two highly acidic regions characteristic of the acidic activation domains of many transcription factors, and nuclear localization signals. Immunofluorescence staining of COS-7 cells transfected with a myc-epitope-tagged MTA1 expression vector clearly showed nuclear localization of MTA1. Coimmunoprecipitation of myc-tagged MTA1 and FLAG-tagged histone deacetylase 1 (HDAC1), followed by western blot analysis using anti-myc and anti-FLAG monoclonal antibodies showed that MTA1 physically bound with HDAC1 in COS-7 cells. Together with the recent finding that the NURD (nucleosome remodeling and histone deacetylase activities) complex contains an MTA1-related gene product, named MTA2, MTA1 may be another component of this complex and be involved in the alteration of chromatin structure and transcription repression.

Animals↗