Biomedical subjects

T Tsukamoto

Publications and source records attributed to T Tsukamoto.

At least 73 records · Page 4Linked to original sources

PubMed2001

[Left adrenocortical cancer with inferior vena cava tumor thrombus--a case report].

An 62-year-old male was admitted to our hospital for an evaluation of high grade fever, body weight loss and lumbago. He was diagnosed as having a left adrenal tumor with intracaval extension and underwent a radical surgery, including resection of the tumor, left kidney, spleen and IVC tumor thrombus. Histopathological diagnosis was adrenocortical carcinoma with tumor thrombus. To our knowledge, our case seems to be the 8th case report of left adrenocortical cancer with tumor thrombus extension into IVC. Average survival of reported cases was about 15 months. At 4 months after surgery, the patient died due to lung metastasis.

Adrenal Cortex Neoplasms↗

PubMed2001

[Low dose CVD chemotherapy as a tumor dormancy therapy for extra-adrenal malignant pheochromocytoma: a case report].

A 38 year-old man presented with upper abdominal mass and hypertension pointed out at a medical examination. Blood pressure was 170/90 under medication of an alpha-blocker. Abdominal CT scan showed an 8 x 8 cm inter-aortocaval mass displacing pancreas head ventrally, and further a 4 x 4 cm mass at the aortic bifurcation, but there was no tumorous lesion in bilateral adrenal glands. Plasma nor-epinephrine level and urinary VMA excretion were excessive but plasma adrenaline level was within normal limits. MIBG scintigram showed hot spots in the 4th and 9th thoracic vertebrae. The destructive change of the 9th vertebra on magnetic resonance imaging strongly suggested metastasis of the tumor. Histologic and immunohistochemical findings of the biopsy specimen taken from the lower abdominal tumor in addition to the above clinical data led to the diagnosis of extra-adrenal malignant pheochromocytoma with spinal metastases. Since 2 cycles of full dose CYVADIC chemotherapy had no effects on lowering the high blood pressure and reducing the tumor size, low dose (60% of the full dose) CVD (cyclophosphamide, vincristine and dacarbazine) was given as a palliative chemotherapy on an out-patient clinic approximately every 4 weeks. After 4 cycles of the chemotherapy, his backache due to spinal metastasis markedly improved, hypertension as well as the plasma dopamine level was normalized and nor-epinephrine level was markedly decreased, though the tumor size was not reduced. Thereafter, no medication for hypertension was necessary. During 3 years and 6 months until now, 36 cycles of the chemotherapy has been repeated with no significant side effects. He has been at full-time work with quality of life being well preserved. Low dose CVD regimen appears to be an effective tumor dormancy therapy for advanced extra-adrenal pheochromocytoma.

Abdominal Neoplasms↗

PubMed2001

[Usefulness of ambulatory adjuvant chemotherapy with low-dose epirubicin in patients with axially-node positive breast cancer: Chiba Epirubicin Cooperative Study Group].

We evaluated the usefulness of adjuvant chemotherapy with low-dose epirubicin (EPI) as a key drug in patients with axially-node positive breast cancer. All the 24 patients who were entered in the study between January 1991 and December 1992 were shown histologically to have more than 4 axially-node involvement and underwent curable resection for the breast lesions. Twenty mg/m2 of EPI was administered intravenously every 4 weeks as ambulatory treatment for 1 year and 5-fluorouracil (5-FU) and tamoxifen (TAM) were concomitantly administered at a dose of 150 mg/day and 20-40 mg/day, respectively, daily for 2 years. The median follow-up period was 70 months with a 55.1% 5-year relapse-free survival and 67.4% 5-year survival rate. One patient developed Grade 3 nausea.vomiting, anorexia and general fatigue; however, the other toxicities were mild, such as Grade 1 leukopenia, liver dysfunction, nausea.vomiting, anorexia and general fatigue. This adjuvant therapy with low-dose EPI was safely administered to outpatients, and is considered to be useful for the treatment of axially-node positive breast cancer.

Adult↗

PubMed2001

[Comparative studies on activities of antimicrobial agents against causative organisms isolated from patients with urinary tract infections (1999). I. Susceptibility distribution].

The bacterial strains isolated from patients diagnosed as having urinary tract infections (UTIs) in 9 institutions in Japan were supplied between the period of August 1999 to July 2000. Then, the susceptibilities of them to many kinds of antimicrobial agents were investigated. The number of them were 499 strains. The breakdown of these strains was Gram-positive bacteria as 31.3% and Gram-negative bacteria as 68.7%. Susceptibilities of these bacteria to antimicrobial agents were as follows; vancomycin (VCM), ampicillin (ABPC) and imipenem (IPM) showed strong activities against Enterococcus faecalis. The increase of low-susceptible strains which was noticed in the former year showed a slight recovery in this year. VCM showed a strong activity against MRSA preventing growth of all strains with 1 microgram/ml. In addition, the activity of arbekacin (ABK) was also strong with the MIC90 of 2 micrograms/ml against MRSA. However, MSSA and MRSA showing low susceptibilities were detected in one strain each (MIC: 16 micrograms/ml and 32 micrograms/ml, respectively). Carbapenems showed high activities against Citrobacter freundii and Escherichia coli. Meropenem (MEPM) prevented growth of all strains within 0.125 microgram/ml. Quinolone resistant E. coli decreased in this year compared with those in the last year, that percentage was less than 5%. Almost all drugs showed strong activities against Klebsiella pneumoniae and Proteus mirabilis. MEPM and carumonam (CRMN) prevented growth of all strains within 0.125 microgram/ml. On the other hand, one strain of K. pneumoniae showing resistance to cefaclor (CCL) and one strain of P. mirabilis showing low susceptibility to most of cephems were detected. Against Pseudomonas aeruginosa, almost drugs were not so active. The MIC90s of carbapenems were 8 micrograms/ml and those of all other drugs were more than 16 micrograms/ml.

Anti-Bacterial Agents↗

PubMed2001

[Comparative studies on activities of antimicrobial agents against causative organisms isolated from patients with urinary tract infections (1999). II. Background of patients].

Five-hundred forty four bacterial strains isolated from 412 patients diagnosed as having urinary tract infections (UTIs) in 9 institutions in Japan were supplied between the period of August 1999 to July 2000. Then, the clinical background of patients were investigated such as sex, age and type of infections, infections and kind of bacteria, frequency of isolation of bacteria by age and infections, bacteria and infections by timing of administration of antibiotics, and bacteria and infections by surgical procedures. About the relationship between age and sex of patients and type of infections, the number of male patients aged less than 50 years was few, and complicated UTIs without indwelling catheter was the most frequent. In females, the number of patients aged less than 20 years was few. Complicated UTIs without indwelling catheter was the most frequent among female patients aged between 40 to 59 years, in other age groups, uncomplicated UTIs was most frequent. As for type of infections and kind of bacteria, Escherichia coli decreased when the infections became complicated, and Pseudomonas aeruginosa and Enterococcus faecalis increased when the infection became complicated. Considering this result by age of patients, isolation frequency of E. coli was gradually decreased with aging in patients aged more than 20 years with uncomplicated UTIs or complicated UTIs without indwelling catheter. The isolation frequencies of E. faecalis and Staphylococcus aureus were gradually increased with aging in complicated UTIs without indwelling catheter. In patients with complicated UTIs with indwelling catheter, there was no difference between age group, and P. aeruginosa and E. faecalis were frequently isolated. As for type of causative organisms in UTIs before and after the administration of antibiotics, the isolation of bacteria was remarkably decreased after administration in patients with uncomplicated UTIs and complicated UTIs without indwelling catheter. E. coli decreased after administration of antibiotics, and P. aeruginosa and E. faecalis increased after administration in patients with all infections. As for type of causative organisms in UTIs and surgical procedures, E. coli were more frequently isolated in patients with uncomplicated UTIs when surgical procedures were experienced. Also, Klebsiella spp. and E. faecalis were more frequently isolated in patients with surgical procedures. However, in complicated UTIs, type of causative organisms had no relationship with surgical procedures.

Adolescent↗

PubMed2001

[Comparative studies on activities of antimicrobial agents against causative organisms isolated from patients with urinary tract infections (1999). III. Secular changes in susceptibility].

The bacteria (Enterococcus faecalis, Staphylococcus aureus, Escherichia coli, Klebsiella spp. and Pseudomonas aeruginosa) isolated from patients diagnosed as having urinary tract infections (UTIs) in 9 institutions in Japan were supplied between the period of August 1999 to July 2000. Then, the susceptibilities of these bacteria to various antimicrobial agents were examined and the results were compared with those obtained between 1991 and 1998. Comparison was made by classifying strains isolated from patients into those with uncomplicated UTIs and those with complicated UTIs (including with or without indwelling catheter). About E. faecalis, increase of low sensitive strains noted in the former year showed a decreasing tendency, however, one strain each with MIC of 4 micrograms/ml to vancomycin (VCM) was detected in patients with both uncomplicated and complicated UTIs. As for S. aureus, many sensitive strains to cephems, imipenem (IPM) and VCM were noted, and each MIC50 was better than that in the former years. S. aureus strains showing low susceptibility to arbekacin (ABK) were detected in patients with complicated UTIs in this year as well as in the former year, and one strain each with MIC of 16 micrograms/ml and 32 micrograms/ml was detected. Susceptibilities of E. coli were effective to all drugs except for penicillins and minocycline (MINO). Decrease of low sensitive strains was also noted in all drugs except for quinolones. Each MIC90 of ciprofloxacin (CPFX) and sparfloxacin (SPFX) in patients with complicated UTIs against E. coli was 3 degrees classes lower than that in patients with uncomplicated UTIs. As for Klebsiella pneumoniae, decrease of low sensitive strains to cephems was noted in patients with uncomplicated UTIs in 1998. In 1999, low sensitive strains decreased also in patients with complicated UTIs, and few were detected. Susceptibilities of K. pneumoniae to quinolones were effective as compared with those in the former years with the MIC80s of 0.125 microgram/ml or below without detection of low sensitive strains. One low sensitive strain of K. pneumoniae with MIC of 8 micrograms/ml was detected for gentamicin (GM). Susceptibilities of P. aeruginosa to carbapenems were notable. The MIC90 of meropenem (MEPM) and IPM was 4 micrograms/ml each which was 2 degrees better than that in 1998. Resistant P. aeruginosa strains to other drugs except for monobactams decreased in 1999.

Anti-Bacterial Agents↗

PubMed2001

Molecular followup of newly diagnosed bladder cancer using urine samples.

PURPOSE: Patients with superficial bladder cancer can be treated with transurethral resection. However, 50% to 70% of them have intravesical recurrence after transurethral resection and muscle invasive disease develops in 10% to 20%, which is eventually indicated for radical cystectomy. Therefore, reliable predictors of intravesical recurrence are required for management of superficial bladder cancer. We investigated whether detection of the loss of heterozygosity in urine samples would be available as a sensitive diagnostic modality for recurrence of bladder cancer. MATERIALS AND METHODS: Urine samples, cancer tissue and peripheral blood lymphocytes were obtained from 37 patients with newly diagnosed bladder cancer, and analyzed for the loss of heterozygosity on chromosomes 9 and 17p by single strand DNA conformation polymorphism analysis. RESULTS: Chromosomal loss was detected on 24 (65%) cancer tissues and 26 (70%) urine samples. The loss of heterozygosity on chromosome 17p was detected in 19 (51%) urine samples, mostly in cancers with higher grades and/or stages. During postoperative followup of 24 patients with superficial bladder cancer who had undergone transurethral resection, intravesical recurrence did not develop in 9 of 10 without chromosomal aberrations in urine samples. In contrast, intravesical recurrence developed in 11 of 14 patients who had a loss of heterozygosity in urine samples. This loss showed a significant correlation with the intravesical disease-free period (p = 0.004). Multivariate analysis revealed that the loss of heterozygosity in urine samples was a significant predictor of intravesical recurrence. CONCLUSIONS: Detection of the loss of heterozygosity in urine samples is available as a sensitive marker for predicting intravesical recurrence of superficial bladder cancer.

Adult↗

PubMed2001

[Transurethral endoscopic treatment for chronic hematospermia caused by müllerian duct cyst and ejaculatory duct obstruction].

Between June 1997 and September 1999, we performed transurethral unroofing (TUUR) in three patients with hematospermia that recurred repeatedly for one year or more. Patient 1 (48 years old) and Patient 2 (59 years old) were diagnosed as having müllerian duct cysts that communicated with the left ejaculatory duct, and Patient 3 (36 years old) as an ejaculatory duct obstruction with the right ejaculatory duct dilation. A mixture of water-soluble contrast medium and indigocarmine blue dye was injected into the cysts and the ejaculatory duct cavity after incision of the vas deferens in Patients 1 and 3, and by cyst puncture under transrectal ultrasound (TRUS) guidance in Patient 2. Then the urethra was incised between the bladder neck and the verumontanum using a Collins' hot knife electrode, and spouting of the dye from the incision was judged to indicate successful unroofing. In Patient 2, safe and simple TUUR was possible by identifying the cyst location and its distance from the knife electrode under TRUS guidance. Hematospermia resolved after surgery in all three patients and there has been no recurrence for 1.3-3.5 years (mean: 2.6 years). Thus, TUUR was effective for treating chronic hematospermia caused by müllerian duct cyst and ejaculatory duct obstruction. For safe and reliable performance of this treatment, TRUS guidance and injection of the dye into the cyst and ejaculatory duct cavity can be recommended.

Adult↗

PubMed2001

[The prediction of bladder outlet obstruction with prostate volume, maximum flow rate, residual urine and the international prostate symptom score in patients with lower urinary tract symptoms].

We determined whether prostate volume (PV), maximum flow rate (Qmax), residual urine (RU) and the International Prostate Symptom Score (I-PSS) predicted bladder outlet obstruction in patients having lower urinary tract symptoms (LUTSs). The study consisted of 114 patients aged 50 years or older with LUTSs who had scores of 8 or more on the I-PSS and 2 or more for the quality of life index. All patients received transrectal ultrasonography for estimation of PV and pressure-flow study (PFS). When PFS showed an obstruction grade of 2 or more in Schäfer's p/Q diagram, the result was defined as bladder outlet obstruction. When we examined which criteria indicated that 90% of patients had bladder outlet obstruction (positive predictive value: 90%), we found that PV of 35 ml or more, Qmax of 8 ml/sec or less, RU of 110 ml or more, and I-PSS of 30 or more did so. Fifty-nine percent of patients met at least one of these criteria. The results suggested that 59% of patients with LUTSs had bladder outlet obstruction with a 90% positive predictive value based on the value of PV, Qmax, RU or I-PSS.

Aged↗

PubMed2001

[A case of polyneuropathy associated with increased levels of vascular endotherial growth factor (VEGF) insera].

A 54-year-old woman began to notice numbness and motor weakness in the lower extremities in July 1999. These symptoms rapidly progressed and she could not walk any more. When she admitted to our hospital, she showed peripherally dominant, moderate motor weakness, drop foot and loss of superficial and deep sensation in the lower extremities, but only slight weakness in the hands. Cranial nerves were intact. Deep tendon reflexes were all absent. Nerve conduction velocities were reduced and cerebrospinal fluid protein was elevated. VEGF was greatly increased in serum (1,850 pg/ml), which has been found to be increased exclusively in patients with Crow-Fukase syndrome. Many characteristic manifestations of the syndrome except polyneuropathy are well explained to be resulted from the abnormal production of VEGF. She did not, however, exhibit any constellation of Crow-Fukase syndrome such as edema, skin change, organomegaly, bone lesions or M-proteinemia. Steroid therapy improved her symptoms and lessened the levels of serum VEGF and cerebrospinal fluid protein. This case indicated that overproduction of VEGF could induce polyneuropathy rather than the other symptoms of Crow-Fukase syndrome, and that a polyneuropathy associated with increased VEGF might exist.

Endothelial Growth Factors↗

PubMed2000

Use of an implanted marker and real-time tracking of the marker for the positioning of prostate and bladder cancers.

PURPOSE: A real-time tracking radiotherapy was investigated to assess its usefulness in precise localization and verification of prostate and bladder cancers. METHODS AND MATERIALS: The real-time tracking radiation therapy (RTRT) system consists of implantation of a 2.0-mm gold marker into a clinical target volume (CTV), three-dimensional radiation treatment planning (3DRTP) system, and the use of two sets of diagnostic x-ray television systems in the linear accelerator room, image processing units, and an image display unit. The position of the patient can be corrected by adjusting the actual marker position to the planned marker position, which has been transferred from the 3DRTP and superimposed on the fluoroscopic image on the display unit of the RTRT system. The position of the markers can be visualized during irradiation and after treatment delivery to verify the accuracy of the localization. Ten patients with prostate cancer and 5 patients with bladder cancer were examined using this system for the treatment setup on 91 occasions. RESULTS: After manual setup using skin markers, the median of absolute value of discrepancies between the actual position of the marker and the planned position of the marker for prostate cancer was 3.4 (0.1-8.9) mm, 4.1 (0.2-18.1) mm, and 2.3 (0.0-10.6) mm for the lateral, anteroposterior, and craniocaudal directions, respectively. The 3D median distance between the actual and planned positions of the marker was 6.9 (1.1-18.2) mm for prostate cancer and 6.9 (1.7-18.6) mm for bladder cancer. After relocation using RTRT, the 3D distance between the actual and planned position of the marker was 0.9 +/- 0.9 mm. Median 3D distances between actual positions after treatment delivery and planned positions were 1.6 (0.0-6.3) mm and 2.0 (0.5-8.0) mm during daily radiotherapy for the marker in patients with prostate cancer and bladder cancer, respectively. CONCLUSION: We believe the new positioning system can reduce uncertainty due to setup error and internal organ motion, although further improvement is needed for the system to account for the rotational and elastic changes of the affected tissues.

Humans↗

PubMed2000

Catalase-less peroxisomes. Implication in the milder forms of peroxisome biogenesis disorder.

We established a Chinese hamster ovary cell line having a temperature-sensitive phenotype in peroxisome biogenesis. This mutant (65TS) was produced by transforming a PEX2-defective mutant, Z65, with a mutant PEX2 gene, PEX2(E55K), derived from a patient with infantile Refsum disease, a milder form of peroxisome biogenesis disorder. In 65TS, catalase was found in the cytosol at a nonpermissive temperature (39 degrees C), but upon the shift to a permissive temperature (33 degrees C), catalase gradually localized to the structures containing a 70-kDa peroxisomal membrane protein, PMP70. In contrast to catalase, other matrix proteins containing typical peroxisome targeting signals, acyl-CoA oxidase and peroxisomal 3-ketoacyl-CoA thiolase, were co-localized with PMP70 in most cells, even at 39 degrees C. We found that these structures are partially functional peroxisomes and named them "catalase-less peroxisomes." Catalase-less peroxisomes were also observed in human fibroblasts from patients with milder forms of peroxisome biogenesis disorder, including the one from which the mutant PEX2 gene was derived. We suggest that these structures are the causes of the milder phenotypes of the patients. Temperature-dependent restoration of the peroxisomes in 65TS occurred even in the presence of cycloheximide, a protein synthesis inhibitor. Thus, we conclude that in 65TS, catalase-less peroxisomes are the direct precursors of peroxisomes.

ATP-Binding Cassette Transporters↗

PubMed2000

Establishment and characterization of a human lung cancer cell line NCI-H460-LNM35 with consistent lymphogenous metastasis via both subcutaneous and orthotopic propagation.

Lymphogenous metastasis is a common feature of human lung cancers, but very little is known about the underlying mechanism. In the present study, in vivo selection was carried out to obtain a highly lymphogenous metastatic subline of a human large cell carcinoma of the lung, NCI-H460. The resulting subline, termed NCI-H460-LNM35 (LNM35), was shown to metastasize to regional lymph nodes with a 100% incidence not only as a result of orthotopic intrabronchial (i.b.) implantation, but also as a result of conventional s.c. implantation. LNM35 has a short latency period, allowing for the collection of experimental data within 28 days after i.b. inoculation and 45 days after s.c. inoculation. It was noted that orthotopically i.b.-propagated LNM35 closely mimicked the clinical manifestations of human lung cancer patients by infiltrating into lymphatic vessels and metastasizing to the mediastinal lymph nodes. The LNM35 cell line is, to the best of our knowledge, the first human lung cancer cell line to be reported as having lymphogenous metastatic properties, and the observed 100% incidence by s.c. inoculation gives LNM35 a significant advantage even over previously reported human cancer cell lines of other origins. Comparisons between LNM35 and its parental NCI-H460 cell lines were also made with regard to expression levels and/or activities of various molecules that are thought to play a part in the metastatic process. We show here that the expression of cyclooxygenase 2 is increased in LNM35 and that a specific cyclooxygenase 2 inhibitor, nimesulide, can inhibit the invasion of LNM35 in vitro through Matrigel containing basement membrane components.

Animals↗

PubMed2000

Eradication diminishes enhancing effects of Helicobacter pylori infection on glandular stomach carcinogenesis in Mongolian gerbils.

To investigate the nature of the link between Helicobacter pylori (Hp) infection and stomach carcinogenesis, a study of the glandular stomach of Mongolian gerbils (MGs) was performed. MGs were treated with N-methyl-N-nitrosourea (MNU), followed by inoculation with Hp (groups 1 and 2) or without Hp (group 3), or infected with Hp (groups 4 and 5) or inoculation without Hp (group 6) followed by MNU administration. At week 21, the animals in groups 2 and 5 underwent an eradication procedure. At week 50, the incidences of adenocarcinomas in group 1 (15 of 23) and group 4 (9 of 26) were significantly higher than in group 3 (1 of 15) and group 6 (1 of 18), respectively. Moreover, those in group 2 (5 of 24) and group 5 (2 of 22) were lower than in groups 1 and 4, respectively. This study shows that Hp eradication may be useful as a prevention approach against stomach cancer.

Adenocarcinoma↗

PubMed2000

Effect of viral status on recurrence after liver resection for patients with hepatitis B virus-related hepatocellular carcinoma.

BACKGROUND: Risk factors for recurrence after resection of hepatitis B virus (HBV)-related hepatocellular carcinoma (HCC) require more precise definition. METHODS: Forty patients who underwent liver resection for HBV-related HCC were studied. Their clinical findings, laboratory data (including viral status), pathologic findings, and operative methods were evaluated for recurrence risk in univariate and multivariate analyses. RESULTS: The HB envelope (HBe) antigen, wild-type HBV, intrahepatic metastases, elevated serum activities of aspartate aminotransferase and alanine aminotransferase, and moderately or severely active hepatitis were more likely to be found in patients with a high viral load than in patients with a low viral load. Precore mutant-type HBV was more likely to be found in patients with a low viral load than in patients with a high viral load. The platelet count was significantly lower in the patients with a high viral load. A high viral load, the presence of wild-type HBV, the absence of anti-HBe, the absence of precore mutant-type HBV, Child score B, a low platelet count, and a positive surgical margin were risk factors for recurrence in univariate analysis. A nonanatomic resection tended to be a risk factor. A high viral load and positive surgical margin were independent risk factors for recurrence. CONCLUSIONS: The measurement of viral load and detection of anti-HBe, wild-type HBV, and precore mutant-type HBV are useful for estimating a patient's prognosis after resection of HBV-related HCC.

Adult↗

PubMed2000

Expression of MAT1/PEA-15 mRNA isoforms during physiological and neoplastic changes in the mouse mammary gland.

MAT1 is a novel transforming gene which was cloned from a mouse mammary tumor induced by N-methyl-N-nitrosourea in vitro in the presence of lithium as a mitogen. Later, it was found to be identical to the 3' untranslated region (UTR) of the 2.5 kb isoform of PEA-15 (phosphoprotein enriched in astrocytes-15 kDa). We re-cloned MAT1/PEA-15 cDNAs and showed 2.5, 2.0 and 1.8 kb isoforms and confirmed MAT1 localization as reported. The 2.0 and 1.8 kb isoforms were produced by alternative splicing and alternative polyadenylation at the 3' UTR, respectively. To analyze the role of MAT1/PEA-15, we examined the expression of MAT1/PEA-15 mRNA in normal mammary tissues and in mammary tumors. The mammary gland during pregnancy, lactation and weaning showed weak but stable expression. Compared with normal mammary gland, mammary tumors showed stronger expression. Aberrant expression of MAT1/PEA-15 isoforms was found in mouse mammary epithelial cell lines, FSK7 and TM6, which lost the 2.5/2.0 and 2.5 kb isoforms, respectively. In contrast to other oncogenes like c-myc, MAT1/PEA-15 mRNA was extremely stable after actinomycin D and cycloheximide treatments suggesting that other protein expression is prerequisite for degradation of MAT1/PEA-15 mRNA. It evoked the possibility of the 3' UTR of MAT1/PEA-15 (designated as MAT1-T) as a riboregulator in mammary tumorigenesis and necessity for further analysis of human breast cancers as well as mouse mammary tumors.

Animals↗

PubMed2000

Cloning and characterization of mRNA capping enzyme and mRNA (Guanine-7-)-methyltransferase cDNAs from Xenopus laevis.

The mRNA cap structure, which is synthesized by a series of reactions catalyzed by capping enzyme, mRNA (guanine-7-)-methyltransferase, and mRNA (ribose-2'-O-)-methyltransferase, has crucial roles for RNA processing and translation. Methylation of the cap structure is also implicated in polyadenylation-mediated translational activation during Xenopus oocyte maturation. Here we isolated two Xenopus laevis cDNAs, xCAP1a and xCAP1b, for mRNA capping enzyme and one cDNA for mRNA (guanine-7-)-methyltransferase, xCMT1, which encode 598, 511, and 402 amino acids, respectively. The deduced amino acid sequence of xCAP1a was highly homologous to that of human capping enzyme hCAP1a, having all the characteristic regions including N-terminal RNA 5'-triphosphatase as well as C-terminal mRNA guanylyltransferase domains which are conserved among animal mRNA guanylyltransferases, whereas in xCAP1b the most C-terminal motif was missing. The amino acid sequence of xCMT1 was also similar to human (guanine-7-)-methyltransferase, hCMT1a, with all the conserved motifs among cellular (guanine-7-)-methyltransferases, except for its N-terminal portion. The recombinant xCAP1a and xCMT1 exhibited cap formation and mRNA (guanine-7-)-methyltransferase activities, respectively. RT-PCR analysis showed that mRNA for xCAP1a and xCMT1 exist abundantly in fertilized eggs as maternal mRNAs, but xCMT1 mRNA gradually decreased in its amount in later stages of early development.

Amino Acid Sequence↗

PubMed2000

Molecular mechanism of detectable catalase-containing particles, peroxisomes, in fibroblasts from a PEX2-defective patient.

Patients with peroxisome biogenesis disorders (PBD) can be identified by detection of peroxisomes in their fibroblasts, by means of immunocytochemical staining using an anti-catalase antibody. We report here data on three PBD patients with newly identified mutations (del550C and del642G) in the PEX2 gene which encodes a 35-kDa peroxisomal membrane protein containing two membrane-spanning and a C-terminal cysteine-rich region. Some of the fibroblasts from the patient with the del642G mutation contained numerous catalase-containing particles, whereas no fibroblasts containing such particles were found in the patient with the del550C mutation. We confirmed that the del642G mutation caused a partial defect in peroxisome synthesis and import by expression of the mutated PEX2 into PEX2-defective CHO mutant cells. We propose that the two putative membrane-spanning segments in Pex2p are important domains for peroxisome assembly and import and that a defect in one of these domains severely affects PBD patients. Furthermore, a defect in the C-terminal portion of Pex2p exposed to the cytosol containing a RING finger motif caused the mild phenotype, residual enzyme activities, and mosaic detectable peroxisomes in fibroblasts from the patient.

Amino Acid Sequence↗