Biomedical subjects

T Igarashi

Publications and source records attributed to T Igarashi.

At least 37 records · Page 2Linked to original sources

PubMed2003

Treatment and prognosis of patients with paraplegia or quadriplegia because of metastatic spinal cord compression in prostate cancer.

Metastatic spinal cord compression (MSCC) is a serious complication of metastatic prostate cancer (PCa). This study retrospectively evaluated patients who presented with paraplegia or quadriplegia because of MSCC of PCa. Of 847 patients with PCa who were treated between 1989 and 1998, 26 (3.1%) demonstrated paraplegia or quadriplegia because of MSCC. Characteristics, treatment efficacy, and prognosis of these patients were analyzed. In total, 15 cases became paraplegic despite androgen ablation therapy (Group I). Average time to paraplegia from initial hormonal treatment was 34 months. Out of nine cases who underwent radiation therapy (RT) to spinal lesions with/without chemotherapy, one patient became ambulatory. However, this patient subsequently had recurrent compression. Two cases had remission of paralysis. Two cases underwent laminectomy plus RT and in one case paralysis improved. MSCC was the first indication of PCa in 11 cases (Group II). Two cases underwent laminectomy plus hormone therapy and nine cases underwent hormone therapy alone. Four patients became ambulatory and two cases showed improved motor capacity. Average interval from paraplegia to death was 7.4 months in Group I and 27.1 months in Group II. However, there was no statistical difference in these two groups on disease-specific survival from the start of initial treatment. It is difficult to recover the ability to walk if paraplegia or quadriplegia occurs in PCa patients although decompression surgery plus hormone therapy seemed to impair the prognosis. Stage M1 patients with paraplegia had survival rates as good as stage M1 patients without paralysis. This should encourage an aggressive treatment approach. However, for patients with hormone-independent disease there seems to be no effective treatment and prognosis is poor.

Adenocarcinoma↗

PubMed2003

Mexiletine carbonyloxy beta-D-glucuronide: a novel metabolite in human urine.

1. The study was performed to isolate and characterize a glucuronic acid conjugate of mexiletine that releases mexiletine on acid hydrolysis from urine samples obtained from healthy volunteers following a single oral dose of mexiletine. 2. The [M-H]- ion of the isolated metabolite was observed at m/z 398 in the negative electrospray ionization mass spectrum. This mass number was 44 higher than that of the product generated when mexiletine is subjected to direct glucuronidation. In positive-ion mode, collision-induced dissociation of the quasimolecular ion [M+NH4]+, m/z 417, gave product ions at m/z 224, 180 and 58. These mass spectral data indicated that the metabolite contained a carbonyloxy moiety in its structure in addition to mexiletine and a glucuronic acid moiety. 3. The presence of this carbonyloxy moiety was further supported by the following chemical reactions. When the metabolite was hydrolysed with an aqueous solution of 1 M sodium hydroxide at room temperature, mexiletine was released, whereas the N-methoxycarbonyl derivative of mexiletine was obtained after treatment of the metabolite with methanolic sodium hydroxide solution. 4. The results indicated that the structure of the isolated metabolite was the N-carbonyloxy beta-D-glucuronic acid conjugate of mexiletine.

Adult↗

PubMed2003

Change of the heterogametic sex from male to female in the frog.

Two different types of sex chromosomes, XX/XY and ZZ/ZW, exist in the Japanese frog Rana rugosa. They are separated in two local forms that share a common origin in hybridization between the other two forms (West Japan and Kanto) with male heterogametic sex determination and homomorphic sex chromosomes. In this study, to find out how the different types of sex chromosomes differentiated, particularly the evolutionary reason for the heterogametic sex change from male to female, we performed artificial crossings between the West Japan and Kanto forms and mitochondrial 12S rRNA gene sequence analysis. The crossing results showed male bias using mother frogs with West Japan cytoplasm and female bias using those with Kanto cytoplasm. The mitochondrial genes of ZZ/ZW and XX/XY forms, respectively, were similar in sequence to those of the West Japan and Kanto forms. These results suggest that in the primary ZZ/ZW form, the West Japan strain was maternal and thus male bias was caused by the introgression of the Kanto strain while in the primary XX/XY form and vice versa. We therefore hypothesize that sex ratio bias according to the maternal origin of the hybrid population was a trigger for the sex chromosome differentiation and the change of heterogametic sex.

Animals↗

PubMed2002

Laparoscopic adrenalectomy for pheochromocytoma.

We reviewed 10 cases of laparoscopic adrenalectomy for pheochromocytoma and compared the results with those of a recent series of 11 patients who underwent open adrenalectomy. Of the 10 cases, the tumor was removed successfully in all cases except in one case with laparoscopy that required open laparotomy. A pair of laparoscopic coagulating scissors was utilized in all except the initial two cases. In the laparoscopy group (excluding the initial two cases and the case that required conversion to open surgery), mean operative time and blood loss were 145 min and 55 ml, respectively. No significant difference was observed in mean operative time between the laparoscopy group and the open surgery group (165 min for open surgery). Mean blood loss of the laparoscopy group was significantly less than that of the open surgery group (330 ml for open surgery, P = 0.01). Mean intervals to first ambulation and oral intake, and postoperative hospital stay of the laparoscopy group, tended to be less than those of the open surgery group, although no statistical significance was observed (2.3 versus 3.2 d, 2.9 versus 3.6 d, and 12 versus 14 d, respectively). We conclude that laparoscopic adrenalectomy for pheochromocytoma is equally effective and less invasive than open adrenalectomy and should be considered the therapy of choice even for pheochromocytoma.

Adolescent↗

PubMed2002

An essential amino acid residue for catalytic activity of the dextranase of Streptococcus mutans.

Dextranase (Dex) is an enzyme that hydrolyzes glucan, a polymer of glucose synthesized from sucrose by glucosyltransferases (GTFs). By comparing amino acid sequences of Dexs and GTFs, we found that the Dex enzymes of Streptococcus mutans, Streptococcus sobrinus, Streptococcus downei and Streptococcus salivarius had similar amino acid sequences to those of the catalytic sites of GTFs of mutans streptococci. We therefore examined the amino acid essential in Dex catalysis by molecular genetic approaches in this study. Site-directed mutagenesis was used to convert the Asp-385 of the Dex molecule of S. mutans Ingbritt to Glu, Asn, Thr or Val. Replacement of Asp-385 with any of the amino acids resulted in complete disappearance of Dex activity. However, replacement of other Asp residues did not affect the enzyme activity. The inactive enzymes still retained dextran-binding ability. These results suggest that Asp-385 of the Dex of S. mutans Ingbritt was essential for enzyme activity and the catalytic and substrate-binding sites were located at different sites within the Dex molecule.

Amino Acid Sequence↗

PubMed2002

Clinical significance of pulmonary metastases in stage D2 prostate cancer patients.

Several prognostic factors such as the extent of bone metastases (EOD) in advanced prostate cancer (PCa) have been reported. Metastasis of the lung is rarely a significant clinical factor in the management of prostate cancer. The present study evaluates the clinical significance of lung metastases. We retrospectively reviewed the PCa database to identify patients with pulmonary metastases at initial diagnosis. The medical records of the patients were examined with respect to age, histologic grade, EOD score, marker response to endocrine therapy and clinical outcome. We then compared several potential clinical factors between patients with and without pulmonary metastases. Next, we retrospectively reviewed autopsy records of 60 Japanese patients who died of hormone-refractory metastatic PCa with particular focus upon metastatic profiles. A comparative study of stage D(2) patients with (n=20) and without (n=77) pulmonary metastases found no significant differences in EOD score, performance status, marker response and survival. Only tumor grade was better in the group with, than without pulmonary metastases (P=0.0120, chi-square analysis). In the series of autopsies, we found pulmonary metastases in 38 cases (63%), following metastases of the bone (57 cases, 95%) and lymph nodes (52 cases, 87%). A retrospective analysis of survival showed that patients with bone or lymph node metastases had a positive relative risk. In contrast, lung metastasis could be a positive prognostic indicator, although the findings were not statistically significant. These data suggest that the presence of pulmonary metastasis has no ominous impact on clinical course and disease outcome even in patients with disseminated prostate cancer.

Aged↗

PubMed2002

Leukotriene receptor antagonist, montelukast, can reduce the need for inhaled steroid while maintaining the clinical stability of asthmatic patients.

BACKGROUND: Oral leukotriene receptor antagonists have been shown to have efficacy in chronic asthma. OBJECTIVE: To determine whether the addition of montelukast could lead to a reduction in inhaled corticosteroid dose without a significant decrease in peak expiratory flow rate (PEFR). METHODS: After a 4-week run-in period, 191 moderate-to-severe asthmatic patients whose asthma had been well controlled with daily inhaled corticosteroid therapy (beclometasone dipropionate 800 to 1600 micro g/day), were randomly assigned to one of two treatments - placebo (n = 98) or montelukast 10 mg once daily (n = 93) - for a 24-week, multicentre, double-blind, treatment period. At the beginning of the active treatment period, the daily dose of inhaled corticosteroid was halved in all of the patients. In addition, the inhaled corticosteroid dose was subsequently titrated every 8 weeks, based on PEFR, asthma symptoms and beta-agonist use. RESULTS: After 8 weeks of a 50% reduction in inhaled corticosteroid use, morning PEFR increased by 5.3 +/- 32.3 L/min from baseline in patients receiving montelukast and significantly decreased by 6.9 +/- 29.0 L/min in those receiving placebo (P = 0.035). In addition, evening PEFR significantly decreased by 9.8 +/- 28.5 L/min (P = 0.003) in the placebo group, but was maintained in the montelukast group. In spite of a subsequent 50% reduction in the inhaled corticosteroid dose every 8 weeks, morning and evening PEFRs were maintained over the 24-week treatment period in the montelukast group; PEFR significantly decreased in the placebo group. There was a significant difference between the two groups with regard to morning PEFR, therapy score and asthmatic score at weeks 8, 16 and 24, as well as evening PEFR at week 8. However, the symptom scores were not significantly different between the two groups or within each group. CONCLUSION: These data suggest that montelukast reduces the need for inhaled corticosteroids while maintaining asthma control over a 24-week period. Therefore, montelukast may be useful for long-term treatment in patients with asthma who require high doses of inhaled corticosteroids.

Acetates↗

PubMed2002

Analysis of a dextran-binding domain of the dextranase of Streptococcus mutans.

AIMS: To examine the dextran-binding domain of the dextranase (Dex) of Streptococcus mutans. METHODS AND RESULTS: Deletion mutants of the Dex gene of Strep. mutans were prepared by polymerase chain reaction and expressed in Escherichia coli cells. Binding of the truncated Dexs to dextran was measured with a Sephadex G-150 gel. Although the Dexs which lacked the N-terminal variable region lost enzyme activity, they still retained dextran-binding ability. In addition, further deletion into the conserved region from the N-terminal did not influence the dextran-binding ability. However, the Dex which carried a deletion in the C-terminus still possessed both enzyme activity and dextran-binding ability. Further deletion into the conserved region from the C-terminal resulted in complete disappearance of both enzyme and dextran-binding activities. CONCLUSIONS: Deletion analysis of the Dex gene of Strep. mutans showed that the C-terminal side (about 120 amino acid residues) of the conserved region of the Dex was essential for dextran-binding ability. SIGNIFICANCE AND IMPACT OF THE STUDY: The dextran-binding domain was present in a different area from the catalytic site in the conserved region of the Dex molecule. The amino acid sequence of the dextran-binding domain of the Dex differed from those of glucan-binding regions of other glucan-binding proteins reported.

Amino Acid Sequence↗

PubMed2002

Factors affecting toxicity, response and progression-free survival in relapsed patients with indolent B-cell lymphoma and mantle cell lymphoma treated with rituximab: a Japanese phase II study.

BACKGROUND: The aim of the study was to determine factors affecting the toxicity and efficacy of rituximab monotherapy in relapsed patients with indolent B-cell lymphoma and mantle cell lymphoma (MCL). PATIENTS AND METHODS: A total of 90 patients were enrolled and treated with rituximab infusions at 375 mg/m2 once weekly for 4 weeks. Central pathology review revealed that histologically, 81 patients had indolent B-cell lymphoma or MCL: 59 with follicular lymphoma, 17 with MCL, four with marginal zone lymphoma and one with lymphoplasmacytoid lymphoma. Of these, four were ineligible due to violation of other eligibility criteria. Pre-treatment variables affecting toxicities were analyzed for all 90 patients, and those affecting response and progression-free survival (PFS) were analyzed for 77 eligible patients with confirmed indolent B-cell lymphoma or MCL. The relationship between serum rituximab levels and efficacy was also analyzed for 66 eligible patients. RESULTS: Hematological toxicities (grade > or =3) occurred more frequently in females (P <0.05), and thrombocytopenia and leukopenia were more frequent in patients with high lactate dehydrogenase (LDH) levels (P <0.05). Non-hematological toxicities (grade > or =2) were more frequent in patients with extranodal disease or bone marrow involvement. The overall response rate (ORR) in patients receiving one prior chemotherapy regimen was higher than those receiving two or more regimens (P <0.05). The median PFS was shorter in MCL patients, in those with extranodal disease, or in those receiving two or more prior chemotherapy regimens (P <0.01). The PFS intervals of patients with higher serum rituximab levels (> or =70 microg/ml) immediately before the third infusion were longer than in other patients (P <0.01). CONCLUSIONS: Several prognostic factors and serum rituximab levels are useful for predicting the toxicity and efficacy of rituximab monotherapy.

Adult↗

PubMed2002

The prototype of sex chromosomes found in Korean populations of Rana rugosa.

The seventh largest chromosome in Japanese populations of the frog Rana rugosa morphologically evolved as a sex chromosome. The sex chromosome is XX/XY type in one geographic form and ZZ/ZW type in another. In contrast, the seventh chromosomes are still homomorphic between the sexes in the other two geographic forms: they are more subtelocentric in the Kanto form and subtelocentric in the western Japanese form. To identify a prototype of the sex chromosomes, we extended our investigation in this study to the Korean form, which is supposed to be close to the phylogenetic origin of this species. The karyotype, a sex-linked gene sequence, and mechanisms of sex determination and gonadal differentiation were all examined. In addition, phylogenetic analyses were performed based on mitochondrial gene sequences and the results of crossings between the Korean and Japanese forms. As a consequence, the more subtelocentric seventh chromosome, shared by the Korean and Japanese Kanto forms, was concluded to be the prototype of the sex chromosomes. Starting at the prototype, a whole process of morphological sex chromosome evolution was reconstructed.

Animals↗

PubMed2001

Neuronal injury and loss after traumatic brain injury: time course and regional variability.

We have examined regional neuronal injury after traumatic brain injury using Fluoro-Jade, an acidic dye that exhibits a marked affinity for both the degenerating neuronal cell body and its processes and have determined the extent to which early injury corresponds to regional patterns of neuronal loss. Rats (n=45) were subjected to lateral fluid percussion brain injury and euthanized at 3 h to 28 days post injury. Complementary Fluoro-Jade, silver impregnation methods and TUNEL were used to assess neuronal injury. Neuronal loss was evaluated in sections immunostained for NeuN, a neuronal specific nuclear protein. Overt neuronal cell loss was evident by 7 days post injury in the cortex, hippocampus and thalamus. Injured neurons were apparent in the ipsilateral cortex bordering the impact site, hippocampus (CA1 and dentate), thalamus, and vermis of the cerebellum as early as 3 h post injury. Degenerating neurons were maximal by 1 and 3 days in the cortex and hippocampus, by 3 and 7 days in the cerebellum, and by 7 days in the thalamus. The regional distribution of Fluoro-Jade-labeled neurons corresponded to a similar pattern of silver and TUNEL staining. Together, these findings demonstrate a regionally specific temporal pattern of neuronal injury that results in overt neuronal cell loss within both cortical and subcortical regions.

Animals↗

PubMed2001

Hypermethylation of the CD44 gene is associated with progression and metastasis of human prostate cancer.

BACKGROUND: CD44 is a metastasis suppressor gene for prostate cancer and the down-regulation of CD44 and its variants is associated with the progression of prostate cancer. Also, hypermethylation of the CpG islands of the CD44 gene is closely associated with transcriptional inactivation, resulting in the decreased expression of CD44. To clarify the exact role of methylation status of CpG islands of CD44 gene in the progression and metastasis of prostate cancer, we investigated the methylation status of this gene in primary and metastatic human prostate tumors obtained from surgery or autopsy. METHODS: We examined 97 samples from 40 Japanese patients with adenocarcinoma of the prostate. Tumor tissues were obtained from radical prostatectomy specimens from eight patients with stage B, 12 patients with stage C and three patients with stage D1 and at autopsy from 17 hormone-refractory metastatic cases, who had initially responded to the therapy and thereafter relapsed. Distant metastatic tissues were also obtained at autopsy (i.e., liver, lung, kidney, mammary gland, and pelvic lymph nodes) from 10 of 17 hormone-refractory cases. We analyzed the hypermethylation status of CD44 promotor region by PCR using genomic DNAs digested with the m(5)C-sensitive restriction enzyme HpaII. RESULTS: The correlation between the methylation status of CD44 gene and the stage progression of prostate cancer was statistically significant (P = 0.0438). In two of 10 hormone-refractory cases, a comparison of the methylation status of the CD44 gene in metastases to that in primary tumors revealed interfocal heterogeneity of CD44 methylation status. CONCLUSIONS: These results indicate an important role of CD44 methylation in the progression and metastasis of prostate cancer, although the amount of methylational heterogeneity is substantial among metastatic sites within the same patient.

Adenocarcinoma↗

PubMed2001

Three families with autosomal dominant nephrogenic diabetes insipidus caused by aquaporin-2 mutations in the C-terminus.

The vasopressin-regulated water channel aquaporin-2 (AQP2) is known to tetramerize in the apical membrane of the renal tubular cells and contributes to urine concentration. We identified three novel mutations, each in a single allele of exon 4 of the AQP2 gene, in three families showing autosomal dominant nephrogenic diabetes insipidus (NDI). These mutations were found in the C-terminus of AQP2: a deletion of G at nucleotide 721 (721 delG), a deletion of 10 nucleotides starting at nucleotide 763 (763-772del), and a deletion of 7 nucleotides starting at nucleotide 812 (812-818del). The wild-type AQP2 is predicted to be a 271-amino acid protein, whereas these mutant genes are predicted to encode proteins that are 330-333 amino acids in length, because of the frameshift mutations. Interestingly, these three mutant AQP2s shared the same C-terminal tail of 61 amino acids. In Xenopus oocytes injected with mutant AQP2 cRNAs, the osmotic water permeability (Pf) was much smaller than that of oocytes with the AQP2 wild-type (14%-17%). Immunoblot analysis of the lysates of the oocytes expressing the mutant AQP2s detected a band at 34 kD, whereas the immunoblot of the plasma-membrane fractions of the oocytes and immunocytochemistry failed to show a significant surface expression, suggesting a defect in trafficking of these mutant proteins. Furthermore, coinjection of wild-type cRNAs with mutant cRNAs markedly decreased the oocyte Pf in parallel with the surface expression of the wild-type AQP2. Immunoprecipitation with antibodies against wild-type and mutant AQP2 indicated the formation of mixed oligomers composed of wild-type and mutant AQP2 monomers. Our results suggest that the trafficking of mutant AQP2 is impaired because of elongation of the C-terminal tail, and the dominant-negative effect is attributed to oligomerization of the wild-type and mutant AQP2s. Segregation of the mutations in the C-terminus of AQP2 with dominant-type NDI underlies the importance of this domain in the intracellular trafficking of AQP2.

Amino Acid Sequence↗

PubMed2001

Primary biliary cirrhosis with antibody against carbonic anhydrase II associates with distinct immunological backgrounds.

Objective: a part of patients with primary biliary cirrhosis (PBC) has anti-human carbonic anhydrase II (CA II) autoantibodies, although several contradictional reports followed. Since immunization of mice with CA II results in cholangitis in a susceptible strain, PBC with anti-CA II antibody may have distinct clinical features. Thus, we tested the sera of patients with PBC for anti-CA II antibodies and compared clinical characteristics of PBC patients with and without anti-CA II antibodies in Japanese patients. Methods: anti-CA II antibodies were detected in nine of 50 (18%) PBC patients by immunoblotting. The evaluation of these patients included various clinical parameters, autoantibodies, and immunological backgrounds. Results: the levels of serum liver tests and the prevalence of serum anti-mitochondrial antibody (77.8 vs. 92.7%) were not different between the patients with and without anti-CA II antibody. However, the prevalence of anti-nuclear antibody (ANA) was significantly higher in the patients with anti-CA II antibody than that in the patients without anti-CA II antibody (66.7 vs. 25.6%, P=0.044), although their mean titers were not statistically different. Association of Sjøgren's syndrome tended to be more frequent in the patients with anti-CA II antibody than those without it (33.3 vs. 14.6%, P=0.327). Studies of HLA class I allotype revealed that three of five (60.0%) patients with anti-CA II antibodies and one patients from 34 (3.0%) patients without anti-CA II antibodies had HLA B51 allotype; the difference in the prevalence of this allotype was significant (P=0.004, Pc=0.01), and the prevalence of other HLA class I and HLA DR allotypes was similar between the patients with and those without anti-CA II antibody. Administration of ursodeoxycholic acid (600 mg per day) was accompanied by change in liver tests in a similar way between the two patient groups. Conclusions: These results suggest that, although clinical features are not distinctive, PBC patients with anti-CA II antibody may have a genetic background, which may contribute to a susceptibility to immune-mediated cholangitis.

Journal Article↗

PubMed2001

Enhanced expression of a-series gangliosides in fibroblasts of patients with peroxisome biogenesis disorders.

Peroxisome biogenesis disorders (PBD) are classified into Zellweger syndrome (ZS), infantile Refsum disease (IRD) and neonatal adrenoleukodystrophy. Disturbances in the differentiation of neural cells such as migration arrest are characteristic of PBD. So far the pathogenesis of these disturbances is not clearly understood. We describe an altered metabolism of glycosphingolipids in PBD which has not yet been investigated. We observed an increased amount of a-series gangliosides, GM2, GM1 and GD1a, in the fibroblasts of patients with ZS and IRD. Gangliosides GM1 and GD1a were not present in detectable amounts in normal subjects. A key step in the synthesis of a-series gangliosides is a transfer of GalNAc to ganglioside GM3, so we determined the level of ganglioside GM3 by immunohistochemical methods. We found a granular structure, which was positive toward anti-ganglioside GM3 antibody in the cytoplasm of the patients' fibroblasts. In control cells, the cell membrane was slightly positive toward anti-GM3 antibody. These results may help to clarify the pathogenesis of PBD with respect to the functional roles of glycosphingolipids in cell differentiation, proliferation and apoptosis.

Fibroblasts↗

PubMed2001

Quantitative determination of marine toxins associated with diarrhetic shellfish poisoning by liquid chromatography coupled with mass spectrometry.

Quantitative determination by liquid chromatography (LC) coupled with mass spectrometry (MS) was achieved for the following 10 toxins found in association with diarrhetic shellfish poisoning: okadaic acid (OA), dinophysistoxin-1 (DTX1), 7-O-palmitoylokadaic acid (palOA), 7-O-palmitoyldinophysistoxin-1 (pa1DTX1), pectenotoxin-1 (PTX1), pectenotoxin-2 (PTX2), pectenotoxin-2 seco acid (PTX2SA), pectenotoxin-6 (PTX6), yessotoxin (YTX), and 45-hydroxyyessotoxin (YTXOH). Toxins in 2 g of the adductor muscle or the digestive glands of scallops, Patinopecten yessoensis, were extracted with 18 ml of methanol-water (9:1, v/v), freed of polar contaminants by partition between chloroform and water, and treated by solid-phase extraction on a silica cartridge column. Samples containing YTXOH were purified separately on a buffered reversed-phase column. Chromatographic separation was achieved by the following combinations of columns and mobile phases: a Symmetry C18 column with acetonitrile-0.05% acetic acid (7:3, v/v) for OA, DTX1, PTX6 and PTX2SA; a Develosil ODS column with the same mobile phase for PTX1 and PTX2; a Capcellpak column with methanol-2.5% acetic acid (98:2, v/v) for palOA and palDTX1; and an Inertsil ODS column with methanol-0.2 M ammonium acetate (8:2, v/v) for YTX and YTXOH. Carboxylic acid toxins were selectively monitored on [M-H]- ions, sulfated toxins on [M-Na]-ions, and neutral toxins on [M+NH4]+ ions. Average recoveries of the toxins spiked to tissue homogenates ranged from 70 to 134%. Detection limits in the muscle ranged from 5 to 40 ng/g and those in the digestive glands from 10 to 80 ng/g.

Chromatography, Liquid↗

PubMed2001

Smad-mediated transcription is required for transforming growth factor-beta 1-induced p57(Kip2) proteolysis in osteoblastic cells.

Cyclin-dependent kinase inhibitory proteins (CKIs) are negative regulators of the cell cycle. Of all CKIs, only p57(Kip2) plays an essential role(s) that other CKIs cannot compensate for in embryonic development. Recently, we found that p57(Kip2) is degraded through the ubiquitin-proteasome pathway in osteoblastic cells stimulated to proliferation by transforming growth factor (TGF)-beta1 (Urano, T., Yashiroda, H., Muraoka, M., Tanaka, K., Hosoi, T., Inoue, S., Ouchi, Y., and Toyoshima, H. (1999) J. Biol. Chem. 274, 12197-12200). We report here that TGF-beta1-induced p57(Kip2) proteolysis is mediated through transcription by the Smad pathway. When the constitutively active form of the TGF-beta type I receptor ALK-5(TD) was ectopically expressed in osteoblastic cells, p57(Kip2) that had been accumulated by serum starvation causing the cell-cycle arrest was rapidly degraded in a manner analogous to TGF-beta1 stimulation. Moreover, Smad2 or Smad3 with Smad4 enhanced the proteolytic pathway of p57(Kip2). The degradation of p57(Kip2) evoked by TGF-beta1 was blocked by forced expression of an inhibitory Smad called Smad7 or by the addition of actinomycin D or alpha-amanitin. These results indicate that accelerated degradation of p57(Kip2) by TGF-beta1/Smad signaling is mediated through a newly synthesized factor(s) that modifies p57(Kip2) or the ubiquitin-proteasome pathway.

Animals↗

PubMed2001

Macrophage are the principal reservoir and sustain high virus loads in rhesus macaques after the depletion of CD4+ T cells by a highly pathogenic simian immunodeficiency virus/HIV type 1 chimera (SHIV): Implications for HIV-1 infections of humans.

The highly pathogenic simian immunodeficiency virus/HIV type 1 (SHIV) chimeric virus SHIV(DH12R) induces a systemic depletion of CD4(+) T lymphocytes in rhesus monkeys during the initial 3-4 weeks of infection. Nonetheless, high levels of viral RNA production continue unabated for an additional 2-5 months. In situ hybridization and immunohistochemical analyses revealed that tissue macrophage in the lymph nodes, spleen, gastrointestinal tract, liver, and kidney sustain high plasma virus loads in the absence of CD4(+) T cells. Quantitative confocal immunofluorescence analysis indicated that greater than 95% of the virus-producing cells in these tissues are macrophage and less than 2% are T lymphocytes. Interestingly, the administration of a potent reverse transcriptase inhibitor blocked virus production during the early T cell phase but not during the later macrophage phase of the SHIV(DH12R) infection. When interpreted in the context of HIV-1 infections, these results implicate tissue macrophage as an important reservoir of virus in vivo. They become infected during the acute infection, gradually increase in number over time, and can be a major contributor to total body virus burden during the symptomatic phase of the human infection.

Adenine↗