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Biomedical subjects

T Tsukiyama

Publications and source records attributed to T Tsukiyama.

At least 37 records · Page 2Linked to original sources
PubMed1999

Precaval draining vein from paraesophageal varices: radiologic-anatomic correlation.

OBJECTIVE: The purpose of this study was to describe the CT features of the precaval draining vein from paraesophageal varices in six patients with liver cirrhosis. We also assessed the anatomic nature of the vein. CONCLUSION: The precaval vein courses anteriorly to the inferior vena cava and drains into the right anterior aspect of the inferior vena cava. The diameter of the precaval vein ranged from 3 to 13 mm (mean, 6.5 mm). The precaval vein is anatomically identical to the anastomosis between the right and left inferior phrenic veins.

Aged↗
PubMed1999

Bioconversion of milbemycin-related compounds: isolation and utilization of non-producer, strain RNBC-5-51.

A non-producing strain, the so-called strain RNBC-5-51 SANK 60198, was isolated during a screening program of strain improvement in the milbemycin production. Strain RNBC-5-51 indicated almost the same characteristics as those in the parent strain, that is, the abundant spore formation on agar media and the good growth in liquid media. But it does not produce any kind of milbemycins. In addition, strain RNBC-5-51 accumulated precursor-like compounds of milbemycin-polyketide, the production of which were inhibited by the addition of cerulenin. In the bioconversion experiments, strain RNBC-5-51 converted milbemycin beta6 and A4 to milbemycin alpha14, and milbemycin beta7 and A3 to milbemycin alpha11, respectively. This strain also converted milbemycin D and avermectin B1a, to 26-(3-methyl-2-butenoyloxy)milbemycin D and 26-(3-methyl-2-butenoyloxy)avermectin B1a, respectively. These results suggest that milbemycin alpha11 is biosynthesized through the same route as milbemycin alpha14, and the mutated step in strain RNBC-5-51 might be in the polyketide synthetic pathway of milbemycins. Strain RNBC-5-51 loses the ability for de novo synthesis of milbemycins, but it retains the ability to bioconvert the milbemycin skeleton. This strain might be useful for C-26 modification of milbemycin-related compounds.

Anti-Bacterial Agents↗
PubMed1998

Inorganic pyrophosphatase is a component of the Drosophila nucleosome remodeling factor complex.

The Drosophila nucleosome remodeling factor (NURF) is a protein complex consisting of four polypeptides that facilitates the perturbation of chromatin structure in vitro in an ATP-dependent manner. The 140-kD NURF subunit, imitation switch (ISWI), is related to the SWI2/SNF2 ATPase. Another subunit, NURF-55, is a 55-kD WD repeat protein homologous to the human retinoblastoma-associated protein RbAp48. Here, we report the cloning and characterization of the smallest (38 kD) component of NURF. NURF-38 is strikingly homologous to known inorganic pyrophosphatases. Both recombinant NURF-38 alone and the purified NURF complex are shown to have inorganic pyrophosphatase activity. Inhibition of the pyrophosphatase activity of NURF with sodium fluoride has no significant effect on chromatin remodeling, indicating that these two activities may be biochemically uncoupled. Our results suggest that NURF-38 may serve a structural or regulatory role in the complex. Alternatively, because accumulation of unhydrolyzed pyrophosphate during nucleotide incorporation inhibits polymerization, NURF may also have been adapted to deliver pyrophosphatase to chromatin to assist in replication or transcription by efficient removal of the inhibitory metabolite.

Amino Acid Sequence↗
PubMed1998

Primary Malignant Lymphoma of the Breast: Mammographic and Ultrasonographic Findings.

Malignant lymphoma rarely involves the breast. We discribe four cases of primary breast lymphoma encountered in our institution from 1979 through 1996, focusing on mammographic and ultrasonographic findings. The lymphomas were demonstrated by mammography as a well-defined mass in one case, an ill-defined mass in two cases and as diffuse increased opacity in one case. No desmoplastic change or calcification was noted. In 3 cases ultrasonography was used, revealing hypoechoic masses with (1 case) or without (2 case) posterior enhancement. During the past two years, 45 of 197 cancers (23%) were demonstrated as a mass without desmoplastic change or calcification by mammography and ultrasonography at our institution. It can be difficult to distinguish malignant lymphoma from more common diseases of the breast, such as carcinoma, by mammography and ultrasonography.

Journal Article↗
PubMed1998

Drosophila NURF-55, a WD repeat protein involved in histone metabolism.

The Drosophila nucleosome remodeling factor (NURF) is a protein complex of four distinct subunits that assists transcription factor-mediated chromatin remodeling. One NURF subunit, ISWI, is related to the transcriptional regulators Drosophila brahma and yeast SWI2/SNF2. We have determined peptide sequences and isolated cDNA clones for a second NURF component (the 55-kDa subunit). Immunological studies show that p55 is an integral subunit of NURF and is generally associated with polytene chromosomes. The predicted sequence of p55 reveals a WD repeat protein that is identical with the 55-kDa subunit of the Drosophila chromatin assembly factor (CAF-1). Given that WD repeat proteins related to p55 are associated with histone deacetylase and histone acetyltransferase, our findings suggest that p55 and its homologs may function as a common platform for the assembly of protein complexes involved in chromatin metabolism.

Acetyltransferases↗
PubMed1998

Hepatic falciform ligament artery: angiographic anatomy and clinical importance.

The hepatic falciform ligament artery (HFLA) was evaluated by angiography and also by dissections. Based on the findings, the mechanism of the post-chemoembolization skin rash was studied. A total of 340 liver cirrhosis patients who underwent hepatic artery chemoembolization for hepatocellular carcinoma were reviewed in terms of the angiographic incidence of the HFLA, variations in its origin, and the incidence of skin rash. The HFLA was demonstrated in 26 (7.6%) of the 340 patients on angiography. Two HFLAs were observed in one patient. The origin was the middle hepatic artery (A4) in 16 cases, the superior branch of the middle hepatic artery in three, the inferior branch of the middle hepatic artery in two, the inferior branch of the left hepatic artery (A3) in three, and the confluence of A3 and A4 in three cases. There were no patients who developed post-chemoembolization skin rash. Two cadavers were dissected to investigate the anastomosis between the HFLA and the subcutaneous artery. Two different anastomoses were found: (1) direct and (2) via the ensiform branch of the internal thoracic artery. These were located at the lower and upper part of the falciform ligament, respectively. The distribution of a chemotherapeutic agent through these anastomoses is the likely cause of post-chemoembolization skin rash. If prophylactic embolization of the proximal portion of the HFLA using a metallic coil is performed, the skin rash will be prevented.

Adult↗
PubMed1998

Veins of Retzius at CT during arterial portography: anatomy and clinical importance.

PURPOSE: To classify the veins of Retzius demonstrated at computed tomography (CT) during arterial portography (CTAP) on the basis of anatomic location and to evaluate the relationship between the frequency of CT visualization and associated disease. MATERIALS AND METHODS: The authors reviewed axial CTAP scans from 130 patients. Patients were classified into one of two groups: patients with liver cirrhosis (group 1 [n = 81]) and patients without liver cirrhosis (group 2 [n = 49]). RESULTS: The pathways of the veins of Retzius were classified as follows: (a) The ileocolic vein drained into the inferior vena cava (IVC) or the right renal vein through the right gonadal vein (n = 61); (b) the pancreaticoduodenal vein drained into the IVC (n = 8); (c) the proximal branches of the superior mesenteric vein drained into the left gonadal vein (n = 6); and (d) the ileocolic vein drained directly into the IVC (n = 5). The veins of Retzius were demonstrated in 41 (51%) of the 81 patients in group 1 and 26 (53%) of the 49 patients in group 2. There was no statistically significant difference between the two groups. CONCLUSION: The veins of Retzius were demonstrated at CTAP in approximately 50% of patients with and 50% of patients without liver cirrhosis.

Adult↗
PubMed1998

Preaortic esophageal veins: CT appearance.

OBJECTIVE: The purpose of this study was to describe the CT imaging features of preaortic esophageal veins in 10 patients with liver cirrhosis. CONCLUSION: Preaortic esophageal veins deriving from the paraesophageal varices course anterior to the descending aorta and drain into the hemiazygos vein. Preaortic esophageal veins are anatomically identical to extrinsic esophageal veins. The diameter of the veins we studied ranged from 1 to 8 mm (mean, 3.1 mm). Two preaortic esophageal veins were noted in each of two patients.

Adult↗
PubMed1997

Role of histone tails in nucleosome remodeling by Drosophila NURF.

The Drosophila nucleosome remodeling factor NURF utilizes the energy of ATP hydrolysis to perturb the structure of nucleosomes and facilitate binding of transcription factors. The ATPase activity of purified NURF is stimulated significantly more by nucleosomes than by naked DNA or histones alone, suggesting that NURF is able to recognize specific features of the nucleosome. Here, we show that the interaction between NURF and nucleosomes is impaired by proteolytic removal of the N-terminal histone tails and by chemical cross-linking of nucleosomal histones. The ATPase activity of NURF is also competitively inhibited by each of the four Drosophila histone tails expressed as GST fusion proteins. A similar inhibition is observed for a histone H4 tail substituted with glutamine at four conserved, acetylatable lysines. These findings indicate a novel role for the flexible histone tails in chromatin remodeling by NURF, and this role may, in part, be independent of histone acetylation.

Acetylation↗
PubMed1997

Chromatin remodeling and transcription.

Recent advances highlight two important chromatin remodeling systems involved in the transcriptional process. One system includes several members of the evolutionarily conserved SWI2/SNF2 family found in distinct multiprotein complexes with ATP-dependent nucleosome destabilizing activity; the other is the enzymatic system that governs histone acetylation and deacetylation. Identification of the catalytic subunits of these opposing histone-modifying activities reveal conserved proteins defined genetically as transcriptional regulators.

Acetylation↗
PubMed1997

Role of nucleosome remodeling factor NURF in transcriptional activation of chromatin.

The Drosophila nucleosome remodeling factor (NURF) is a protein complex of four subunits that assists transcription factor-mediated perturbation of nucleosomes in an ATP-dependent manner. We have investigated the role of NURF in activating transcription from a preassembled chromatin template and have found that NURF is able to facilitate transcription mediated by a GAL4 derivative carrying both a DNA binding and an activator domain. Interestingly, once nucleosome remodeling by the DNA binding factor is accomplished, a high level of NURF activity is not continuously required for recruitment of the general transcriptional machinery and transcription for at least 100 nucleotides. Our results provide direct evidence that NURF is able to assist gene activation in a chromatin context, and identify a stage of NURF dependence early in the process leading to transcriptional initiation.

Adenosine Triphosphatases↗
PubMed1996

Peripancreatic veins on thin-section (3 mm) helical CT.

OBJECTIVE: The purpose of this study was to evaluate thin-section helical CT for the frequency of visualization of the peripancreatic veins, the venous anatomy at the head of the pancreas, and variations of the venous anatomy. SUBJECTS AND METHODS: We performed 30-sec helical CT of the pancreas with one breath-hold and a 3-mm scanning collimation in 50 patients. The scan was started 60 sec after injection of an i.v. contrast medium at the rate of 2 ml/sec (total amount of contrast medium, 100 ml). The axial scan data were reviewed for the following information: the frequency of CT visualization of the peripancreatic veins (anterior superior pancreaticoduodenal vein, first jejunal vein, gastrocolic trunk, inferior mesenteric vein, left gastric vein, middle colic vein, posterior superior pancreaticoduodenal vein, right colic vein, and right gastroepipolic vein) and the anatomic relationship between the large portal venous system (portal vein, superior mesenteric vein, and splenic vein) and its tributaries. RESULTS: The frequency of visualization on CT of each vessel was gastrocolic trunk, 100%; right gastroepiploic vein, 100%; first jejunal vein, 96%; inferior mesenteric vein, 88%; left gastric vein, 80%; posterior superior pancreaticoduodenal vein, 72%; middle colic vein, 72%; right colic vein, 64%; and anterior superior pancreaticoduodenal vein, 50%. The anatomic relationship between the large portal venous system and its tributaries was as follows: The left gastric vein drained into the splenic vein-portal vein confluence (46%), into the splenic vein (32%), and into the portal vein (22%); the inferior mesenteric vein drained into the splenic vein (46%), the splenic vein-superior mesenteric vein confluence (25%), and the superior mesenteric vein (29%). The posterior superior pancreaticoduodenal vein drained into the portal vein above the splenic vein-portal vein confluence (mean distance, 0.3 cm). The middle colic vein, gastrocolic trunk, and first jejunal vein drained into the superior mesenteric vein below the splenic vein-portal vein confluence (mean distances of 2.4 cm, 3.0 cm, and 3.7 cm, respectively). CONCLUSION: Thin-section helical CT scans provide good visualization of the peripancreatic veins.

Abdomen↗
PubMed1995

Purification and properties of an ATP-dependent nucleosome remodeling factor.

We report the purification of an ATP-dependent nucleosome remodeling factor (NURF) from Drosophila embryo extracts. NURF is composed of at least four polypeptides that act in concert with the GAGA transcription factor to alter chromatin structure at the hsp70 promoter. The energy requirement is attributed to an ATPase activity that is stimulated by nucleosomes but not by free DNA or histones, suggesting that NURF acts directly on a nucleosome to perturb its structure. This finding and the physical properties of NURF contrast sharply with the multisubunit SWI2/SNF2 complex, which has also been shown to alter nucleosomes in an ATP-dependent manner. The results suggest that two distinct systems may be involved in remodeling chromatin for transcription.

Adenosine Triphosphatases↗
PubMed1995

ISWI, a member of the SWI2/SNF2 ATPase family, encodes the 140 kDa subunit of the nucleosome remodeling factor.

The generation of an accessible heat shock promoter in chromatin in vitro requires the concerted action of the GAGA transcription factor and NURF, an ATP-dependent nucleosome remodeling factor. NURF is composed of four subunits and is biochemically distinct from the SWI2/SNF2 multiprotein complex, a transcriptional activator that also appears to alter nucleosome structure. We have obtained protein microsequence and immunological evidence identifying the 140 kDa subunit of NURF as ISWI, previously of unknown function but highly related to SWI2/SNF2 only in the ATPase domain. The ISWI protein is localized to the cell nucleus and is expressed throughout Drosophila development at levels as high as 100,000 molecules/cell. The convergence of biochemical and genetic studies on ISWI and SWI2/SNF2 underscores these ATPases and their close relatives as key components of independent systems for chromatin remodeling.

Adenosine Triphosphatases↗
PubMed1995

Homologs of Drosophila Fushi-Tarazu factor 1 map to mouse chromosome 2 and human chromosome 9q33.

SF-1, a nuclear receptor that regulates gene expression of the cytochrome P450 steroid hydroxylases, and ELP, an embryonal protein that suppresses expression of the Moloney murine leukemia virus LTR, are isoforms transcribed from the same gene by alternative promoter usage and splicing. This gene is the mammalian homolog of the Drosophila fushi-tarazu factor 1 (FTZ-F1) gene. We have mapped the mouse gene Ftzf1 to the proximal quarter of Chr 2 by a linkage analysis using interspecific backcross mice, and its human homolog FTZ1 to Chr 9q33 by fluorescence in situ hybridization. The mouse and human genes are located in the homologous regions of mouse Chr 2 and human Chr 9, respectively.

Adrenal Insufficiency↗
PubMed1995

Protection against metastasis by immunization with an allogeneic lymphocyte antigen.

Q5 antigens are expressed on the surface of various experimental murine tumor cells. They share partially common antigenicity with Qa-2 alloantigens expressed on normal lymphocytes. For that reason we tested the immunoprotection by anti-Qa-2 immunization of mice against a Q5+ tumor. Nerve fibrosarcoma (NSFA) tumor, which specifically develops metastasis in the lung, has been reported to be poorly immunogenic. However, expression of the Q5 antigen was evident on the surface of NFSA cells. After immunizing (C3H/He x B6.K1)F1 (Qa-2-) mice with B6 (Qa-2+) lymphocytes, the protection against the proliferation of the semi-syngeneic NFSA tumor was examined. First, immunization of normal mice induced resistance to NFSA cell transplants. Second, when the tumor cells were transplanted to the hind foot of a mouse and the resulting tumor was removed by amputating the leg, the mice were protected against the development of lung metastasis after immunization by intraperitoneal inoculation of B6 cells 3 days after tumor removal. Immunization with attenuated NFSA cells in this system failed to protect the mice from lung metastasis. On the other hand, inoculation of the mice with B6 cells without removal of the original tumor on the foot showed little effect on the progression of the tumor. Thus, cytotoxic T lymphocytes (CTL), which seemed to be present in an inactive form in the mice from which the tumor had not been removed, were induced in the mice after the removal of the major tumor followed by immunization with B6 lymphocytes. The induction of CTL by the immunization was suppressed in mice bearing large tumors. Cells stimulated by the tumor antigen seemed to be involved in the suppression. It was also shown that the Q5 antigen is the direct recognition target of the CTL since the activity of Q5-specific CTL clones in lysing tumor cells was inhibited by a monoclonal antibody specific for the Q5 antigen. In contrast to immunization with attenuated tumor cells, our novel allogeneic lymphocyte immunization procedure offers high CTL activation, by-passing the induction of T cell unresponsiveness.

Amputation, Surgical↗