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Biomedical subjects

K Kumada

Publications and source records attributed to K Kumada.

At least 73 records · Page 4Linked to original sources
PubMed1996

Requirement for PP1 phosphatase and 20S cyclosome/APC for the onset of anaphase is lessened by the dosage increase of a novel gene sds23+.

Ubiquitin-dependent proteolysis is required for the onset of anaphase. We show that protein dephosphorylation by protein phosphatase 1 (PP1) is also essential for initiating anaphase in fission yeast. PP1 may directly or indirectly regulate the 20S cyclosome/APC (anaphase-promoting complex) required for anaphase-promoting proteolysis. Using anti-phosphopeptide antibodies, PP1 is shown to be dephosphorylated at the C-terminus, upon the onset of anaphase, for reactivation. sds23+, a novel gene, is a multicopy suppressor for mutations in PP1 and the 20S cyclosome/APC, implying that the gene dosage increase can relieve the requirement for PP1 and the cyclosome/APC for the onset of anaphase. The sds23+ gene is not essential for cell viability, but a mutant with the gene deleted cannot form colonies at 22 and 36 degrees C. In the sds23 deletion mutant, the progression of anaphase and cytokinesis is retarded and cell shape is aberrant. These defects are overcome by plasmids carrying the genes encoding subunits of the 20S cyclosome/APC or PP1. These results demonstrate functions other than promoting anaphase for the components of the 20S cyclosome/APC and also a close functional relationship of Sds23 with PP1 and 20S cyclosome/APC.

Amino Acid Sequence↗
PubMed1996

20S cyclosome complex formation and proteolytic activity inhibited by the cAMP/PKA pathway.

The 20S cyclosome complex (also known as the anaphase-promoting complex) has ubiquitin ligase activity and is required for mitotic cyclin destruction and sister chromatid separation. The formation and activation of the 20S cyclosome complex is regulated by an unknown mechanism. Here we show that Cut4 (ref. 6) is an essential component of the cyclosome in fission yeast. Cut4 shares sequence similarity with BimE, a protein that regulates mitosis in Aspergillus nidulans. Mutations in cut4 result in hypersensitivity to cyclic AMP and to stress-inducing heavy metals, inhibition of the onset of anaphase, disruption of the 20S complex, and inhibition of mitotic cyclin ubiquitination. These phenotypes are fully suppressed by cAMP phosphodiesterase and the protein kinase A (PKA) regulatory subunit and weakly suppressed by Sti1 (an activator of the Hsp70 and Hsp90 chaperones). Suppression correlates with the amount of 20S complex, indicating that cyclosome formation and activation is inhibited by the cAMP/PKA pathway.

Anaphase↗
PubMed1996

Calcitonin gene-related peptide is a potent intestinal, but not gastric, vasodilator in conscious dogs.

The effects of human alpha-calcitonin gene-related peptide (alpha-CGRP), beta-CGRP, and vasoactive intestinal polypeptide (VIP) on left gastric (LGA) and superior mesenteric arterial (SMA) blood flow, heart rate and systemic arterial blood pressure were investigated in 6 conscious beagle dogs. Both intravenous injections of alpha-CGRP and beta-CGRP (5-200 pmol/kg) and infusion of alpha-CGRP (25-100 pmol/kg per h) induced a dose-related increase in SMA flow and a dose-related decrease in its resistance. At lower doses, alpha-CGRP was more potent than beta-CGRP, but their maximal responses were the same. alpha-CGRP and beta-CGRP had little effect on LGA flow. However, alpha-CGRP at 200 pmol/kg, but not beta-CGRP, stimulated gastroduodenal contractions that were associated with a phasic increase of LGA flow. Atropine inhibited gastric, but not duodenal, motor and circulatory responses to alpha-CGRP. Tachycardia and hypotension induced by beta-CGRP were significantly less than those by alpha-CGRP. VIP, on the other hand, increased mainly LGA flow. These results suggest that blood vessels of the small intestine of dogs are more sensitive to CGRP than those of the stomach, while the sensitivity to VIP is reversed.

Animals↗
PubMed1996

Cut2 proteolysis required for sister-chromatid seperation in fission yeast.

Although mitotic cyclins are well-known substrates for ubiquitin-mediated proteolysis at the metaphase-anaphase transition, their degradation is not essential for separation of sister chromatids; several lines of evidence suggest that proteolysis of other protein(s) is required, however. Here we report the anaphase-specific proteolysis of the Schizosaccharomyces pombe Cut2 protein, which is essential for sister-chromatid separation. Cut2 is located in the nucleus, where it is concentrated along the short metaphase spindle. The rapid degradation of Cut2 at anaphase requires its amino-terminal region and the activity of Cut9 (ref. 14), a component of the 20S cyclosome/anaphase-promoting complex (APC), which is necessary for cyclin destruction. Expression of non-degradable Cut2 blocks sister-chromatid separation but not cell-cycle progression. This defect can be overcome by grafting the N terminus of cyclin B onto the truncated Cut2, demonstrating that the regulated proteolysis of Cut2 is essential for sister-chromatid separation.

Amino Acid Sequence↗
PubMed1996

Caffeine-resistance in fission yeast is caused by mutations in a single essential gene, crm1+.

Caffeine is a base analogue and is known to affect a wide variety of cellular processes. In order to dissect genetically molecules which mediate the biological effects of caffeine, temperature-sensitive (ts) and caffeine-resistant mutants were isolated from fission yeast, Schizosaccharomyces pombe. Surprisingly, all twelve ts isolates contained a mutation in the same locus, crm1. Cells of the ts crm1 mutant showed an abnormal chromosome structure at the restrictive temperature, an elevated expression of Pap1-dependent transcription, and cross-resistance to an unrelated drug such as staurosporine. Overproduction of pap1+ also conferred caffeine resistance, whilst the resistance of the crm1 mutant is abolished in the pap1- background. These results show that the crm1+ gene is a major locus for caffeine resistance, which arises from Pap1-dependent transcriptional activation.

Alkaloids↗
PubMed1996

Histopathological response to preoperative chemotherapy including 5-fluorouracil additionally assessed by immunocytochemical and pharmacologic parameters in patients with advanced gastric cancer.

To investigate quantitative methods for assessing the response to preoperative downstaging chemotherapy (PDC), the immunocytochemical expression of proliferating cell nuclear antigen (PCNA) and bromodeoxyuridine (BrdU) as well as a pharmacologic study of the rate of thymidylate synthetase inhibition (TSIR) were studied in resected specimens obtained from patients with advanced gastric cancer. Fifty-one patients with advanced gastric cancer who received PDC (30 with 5-fluorouracil peroral administration and the other 21 with intravenous administration of 5-fluorouracil and cisplatin) were studied. The labeling index of PCNA (PCNA-LI) and BrdU were measured. The PCNA suppression (PCNA-S), which was measured by both the values of prechemotherapeutic PCNA-LI in endoscopically biopsied specimens and postchemotherapeutic PCNA-LI in resected specimens, was also examined. TSIR was measured by a protein-bound radiochemical method. We compared the above-mentioned parameters with the histopathological response to PDC according to the General Rules for Gastric Cancer Study. In the patients with peroral 5-flurorouracil, a stepwise regression analysis showed that TSIR is a significantly effective for determining the histopathological response to PDC. In the patients with 5-fluorouracil and cisplatin, PCNA-S was the most effective indicator of the histopathological response to PDC, as shown by a stepwise regression analysis. The present study thus showed that both TSIR and PCNA-S were effective additional indicators of the histopathological response to PDC.

Administration, Oral↗
PubMed1996

Influence of hepatic mitochondrial redox state on complement biosynthesis and activation during and after cardiopulmonary bypass operations.

We have proposed the hazardous phenomena associated with cardiopulmonary bypass (CPB) are due to metabolic derangement by hepatic mitochondrial dysfunction during and after CPB. On the contrary, complement activation and consumption during CPB is reported to be related to the morbidity associated with cardiac surgery. To determine the significance of the hepatic mitochondrial function on the morbidity of cardiac surgery, we measured the serum levels of complements (C3 and C4), activated complements (C3a and C4a), and the arterial ketone body ratio (AKBR), which reflects the hepatic mitochondrial redox state, in 30 patients undergoing CPB. The AKBR, which was at a normal level preoperatively, dropped to a critical level after the initiation of CPB and remained at a low level during the CPB, returning to the preoperative level on the second postoperative morning in a time dependent fashion. The patients group were assigned to two groups according to their AKBR on the first postoperative morning. Group I consisted of patients whose AKBR had recovered to above 0.7 on the first postoperative morning (n = 16). Group II consisted of the rest of the patients (n = 14). The serum complement concentration had considerably decreased by the end of bypass, but recovered in a time-dependent fashion after CPB. The group I patients (C3: 71% of its preoperative value, C4: 85% of its preoperative value) recovered their complements more quickly than the group II patients (C3: 56% of its preoperative value, C4: 54% of its preoperative value). However, the serum C3a and C4a concentrations increased by the end of bypass (C3a: 806% of its preoperative value, C4a: 341% of its preoperative value). The activated complements were significantly higher in the group II patients (C3a: 124% of its preoperative value, C4a: 236% of its preoperative value) than in the group I patients (C3a: 75% of its preoperative value, C4a: 113% of its preoperative value) on the first postoperative morning. It is suggested that hepatic mitochondrial function is related to recovering the complements and to reducing the activated complements after CPB.

Adolescent↗
PubMed1996

Establishment of a hepatocyte cell line producing growth-promoting factors for liver-colonizing tumor cells.

A hepatocyte-derived cell line designated MLE-15A2 was established from a primary culture of mouse hepatocytes. The MLE-15A2 cells appeared to retain the basic nature of hepatocytes in that they showed morphology of an epithelial cell type and secreted albumin into the culture medium. These cells were grown on collagen-coated plates and could be easily expanded to a large-scale culture. Therefore, MLE-15A2 cells may provide a more useful model for studying liver microenvironments than primary cultures of hepatocytes. We found that conditioned media from MLE-15A2 cells, as well as from primary cultures of hepatocytes, promoted the proliferation of highly liver-colonizing colon 26 NL-17 cells better than the poorly liver-colonizing colon 26 NL-4 cells. Moreover, the conditioned media stimulated the growth of some human colon cancer cell lines. These results indicate that MLE-15A2 cells secrete growth factors that selectively stimulate certain tumor cell types. Hepatocyte-derived growth factors may regulate selective survival and colonization of tumor cells in the process of liver metastasis. The growth-promoting activity was unaffected by dialysis, was stable at 80 degrees C for 30 minutes and was bound to a heparin-Sepharose column. The major activity was eluted from the column with 0.7-0.75 M NaCl, and some minor activities eluted with lower concentrations of NaCl. These results suggest that the active components are heterogeneous heparin-binding proteins with lower affinity to heparin than platelet-derived and fibroblast growth factors.

Animals↗
PubMed1996

Heparin-like glycosaminoglycans inhibit leukocyte adhesion to endotoxin-activated human vascular endothelial cells under nonstatic conditions.

Since heparin-like glycosaminoglycans (GAGs) have been reported to possess anti-inflammatory effects, we tested effects of heparin-like GAGs on cell adhesion between endothelial cells (ECs) and leukocytes. Effects of heparin-like GAGs on adhesion molecule expression and leukocyte adhesion were analyzed using cultured human umbilical vein ECs stimulated by endotoxin. Expression of adhesion molecules on ECs was unchanged, but adherence of leukocytes to ECs was significantly reduced by heparin-like GAGs under nonstatic conditions. These results suggest that heparin-like GAGs may act as anti-inflammatory agents partly by inhibition of leukocyte adherence to stimulated ECs under nonstatic conditions and may prevent critical conditions caused by endotoxin.

Anti-Inflammatory Agents↗
PubMed1996

Long-term followup of patients with tumor thrombi from renal cell carcinoma and total replacement of the inferior vena cava using an expanded polytetrafluoroethylene tubular graft.

PURPOSE: Inferior vena caval resection and its reconstruction are sometimes necessary when the inferior vena cava is extensively involved by a large and fixed tumor thrombus from renal cell carcinoma or other malignancies. We successfully replaced the inferior vena cava using tubular expanded polytetrafluoroethylene (Teflon) vascular grafts after en bloc removal of the tumor thrombus and inferior vena cava. We followed the patients long term and observed inferior vena caval patency. MATERIALS AND METHODS: The 3 men and 2 women ranged from 42 to 75 years old. The renal tumors were on the right side in 4 patients and asynchronously bilateral in 1. The suprarenal inferior vena cava was replaced in 3 patients and the infrarenal portion was replaced in 2. The expanded polytetrafluoroethylene tube grafts, 18 to 22 mm. in diameter and 5 to 12 cm. long, were externally stented in 3 patients and not stented in 2. RESULTS: Followup ranged from 6 to 96 months (mean 58). Long-term patency of the graft was maintained in all patients. Of the patients 3 had no evidence of disease at 6 months and 2 died of recurrent tumor at 6 and 84 months. CONCLUSIONS: Total replacement of the inferior vena cava using an expanded polytetrafluoroethylene tubular graft may offer a feasible method with good patency rates in the long term.

Adult↗
PubMed1996

[Clinicopathological study of Henoch-Schönlein purpura nephritis with special reference to C3c deposits].

The aim of this study was to evaluate glomerular C3c deposits of Henoch-Schönlein purpura nephritis (HSPN) in children. Fifty-one patients aged 7-15 years (20 males and 31 females) were studied. On histological investigation, crescent formation seen under light microscopy and subepithelial electron dense deposits (EDD) under electron microscopy were found to be related to the degree of proteinuria and the duration of proteinuria and/or hematuria. A comparative clinicopathological study was performed on C3c-positive patients (n = 22) and C3c-negative patients (n = 25). Histological findings, such as crescent formation and subepithelial EDD, had no relation to glomerular C3c-deposits. At renal biopsy, C3c deposits were positive in 65 % of patients with heavy proteinuria ( > 100mg/kg/day), and in 30% of mild proteinuria patients ( < 50mg/kg/day). The difference between the two groups was statistically significant (p < 0.05). The duration of proteinuria and/or hematuria in C3c-positive patients had a tendency to persist in comparison with that in C3c-negative cases. Renal biopsies on many cases of C3c-negarive patients were performed following the lapse of three months, while the biopsies on patients showing global (+) C3c deposits (n = 15) were conducted within the three-month period. These results suggest that glomerular C3c deposits influence the clinical conditions of patients with HSPN, and complement activation is generated in the early stage of HSPN.

Adolescent↗
PubMed1996

Case report: development of hepatocellular carcinoma in a patient with chronic hepatitis C infection after a complete and sustained response to interferon-alpha.

A 60-year-old man with a chronic hepatitis C virus (HCV) infection and histological features of chronic active hepatitis was treated with interferon-alpha (IFN). He successfully responded to IFN with normalization of serum ALT and disappearance of serum HCV-RNA. His liver biochemistry profile remained normal and serum HCV-RNA was not detected throughout the entire follow-up period. One year later, a small hepatocellular carcinoma (HCC) was detected by routine ultrasonographic screening. Laparotomy revealed a small tumour with no metastasis and the non-tumorous liver demonstrated macronodular cirrhosis. Although no space-occupying lesions were detected by frequent radiological examinations prior to IFN therapy, the small size of the tumour suggested de novo development of HCC. Patients with chronic HCV infection, including those who have complete responses to IFN and lack clinical and histological evidence of cirrhosis, should be followed up for the potential development of HCC.

Antiviral Agents↗
PubMed1996

Possible prediction of adverse reactions to pyrimidine chemotherapy from urinary pyrimidine levels and a case of asymptomatic adult dihydropyrimidinuria.

Deficiency of dihydropyrimidine dehydrogenase or dihydropyrimidinase, enzymes that catalyze the breakdown of pyrimidine chemotherapy agents such as 5-fluorouracil, may cause serious adverse reactions to these agents. We attempted to establish the reference range for urinary pyrimidines in adults to detect individuals with abnormal pyrimidine metabolism. We analyzed urinary pyrimidine levels in 1133 adults to establish a reference range for persons ages 20 years or older. Urinary dihydrouracil and uracil levels were determined by high-performance liquid chromatography with column switching. The reference range obtained was found to be 0-59.3 micromol/g creatinine for dihydrouracil and 0-129.8 micromol/g creatinine for uracil. In addition, an asymptomatic man with suspected dihydropyrimidinase deficiency was detected on the basis of dihydropyrimidinuria. Although only three cases of this disease have been found worldwide, including one infant reported previously by our group, it may not be so rare as has been thought. In this man, a 10 mg/kg oral uracil loading test yielded a peak blood dihydrouracil level of 192.1 micromol/liter and a peak uracil level of 67.8 micromol/liter. Eight h after loading, the uracil level was still 11.1 micromol/liter, about 17 times that in healthy subjects. Additional research on dihydropyrimininase deficiency may help to prevent adverse reactions to pyrimidine chemotherapy agents in susceptible individuals.

Adult↗
PubMed1995

Ventral pancreatitis in a patient with pancreas divisum.

Pancreas divisum results in drainage of most pancreatic secretions through the minor papilla via the dorsal duct, and the association of minor papilla stenosis has been implicated as a cause of pancreatitis. Most of the reported cases represent pancreatitis confined to the dorsal part. The authors treated a 10-year-old boy with recurrent pancreatitis that was substantially more severe in the ventral part. The patient was referred with a brief history of abdominal pain and had undergone a laparotomy when segmental ventral pancreatitis had been observed. Severe pancreatitis and acute renal failure developed, which required drainage of the lesser sac and hemodialysis, respectively. After 5 months, he had another episode that subsequently led to a pseudocyst in the ventral part. Endoscopic retrograde cholangiopancreatography via minor papilla showed a normal-caliber dorsal duct communicating with a part of the fine ventral ducts. A normal biliary tree was shown, but no ventral duct was visualized by cannulation to the major papilla of Vater. Dual sphincteroplasties and a cholecystectomy were performed. The minor papilla was stenotic and admitted only the finest lacrimal duct probe. The orifice of the ventral duct could not be observed. Thus it was clarified that the dorsal duct with its stenotic orifice had drained both the dorsal and ventral pancreas. The patient has remained asymptomatic over 36 months postoperatively. Despite their limited experience, the authors believe that (1) this anatomic variant led to ventral pancreatitis, and (2) the sphincteroplasty of the minor papilla was successful.

Acute Disease↗
PubMed1995

Efficacy of intraportal injection of anti-ICAM-1 monoclonal antibody against liver cell injury following warm ischemia in the rat.

BACKGROUND: Increased expression of intercellular adhesion molecule-1 (ICAM-1) and lymphocyte-function-associated antigen-1 (LFA-1) has been reported to play a major role in reperfusion injury after ischemia. In the present study we tested the effects of anti-rat-ICAM-1 monoclonal antibody (1A29) on partial-liver warm ischemia in rats. METHODS: Histological changes and expression of ICAM-1 and LFA-1 were investigated in rat partial-liver warm ischemia, performed by clamping hepatic hilar vessels distributing to the right lateral lobe for 30, 45, and 60 minutes. In a second study, the effects of intraportal 1A29 injection after 60 minutes of warm ischemia in the rat were examined histologically. In both studies, the liver tissue was removed for analysis 48 hours after clamping. RESULTS: Reperfusion after 60 minutes of warm ischemia induced histological liver injury and strong expression of ICAM-1 and LFA-1, although 30 and 45 minutes of ischemia did not provoke either histological damages or the expression of ICAM-1 and LFA-1. Intraportal injection of 1A29 after 60 minutes of warm ischemia clearly suppressed liver cell injury histologically. CONCLUSION: Intraportal injection of 1A29 prevented the histological inflammation of an ischemic liver and may be useful in liver surgery or liver transplantation, because high concentrations can reach the target organ and nonspecific immunosuppression in other tissues and organs can be decreased.

Animals↗
PubMed1995

Fission yeast TPR-family protein nuc2 is required for G1-arrest upon nitrogen starvation and is an inhibitor of septum formation.

Fission yeast nuc2+ gene encodes a protein of a tetratricopeptide repeat (TPR) family which is conserved throughout evolution. We previously showed that nuc2 is required for exit from the mitotic metaphase. In this study, we present evidence which shows that nuc2 has two additional roles in the cell cycle. We showed that the nuc2 mutant is sterile even at the permissive temperature and septation occurs in the absence of chromosome separation at the restrictive temperature. The nuc2 mutant fails to arrest at the G1 phase upon nitrogen starvation at the permissive temperature which is a prerequisite for conjugation. Upon starvation, however, the nuc2 mutant ceased division normally and induced starvation-dependent gene expression. Therefore, the nuc2 mutant is deficient only for failure to block DNA replication upon starvation. At the lower restrictive temperature, the nuc2 mutant showed a 'cut' phenotype where septation and cytokinesis takes place without the completion of mitosis. Ectopic overexpression of the nuc2+ gene caused multiple rounds of S and M phases in the complete absence of septum formation. We propose that nuc2 is a novel cell cycle regulator essential for three events; firstly for exit from mitosis, secondly for DNA replication restraint under nutrient starvation and thirdly for inhibition of septation and cytokinesis until the completion of mitosis.

Apc3 Subunit, Anaphase-Promoting Complex-Cyclosome↗