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R Kubota

Publications and source records attributed to R Kubota.

At least 73 records · Page 4Linked to original sources
PubMed1994

Active and passive mechanisms of [fluorine-18] fluorodeoxyglucose uptake by proliferating and prenecrotic cancer cells in vivo: a microautoradiographic study.

UNLABELLED: In this study, [18F]FDG uptake mechanisms were investigated in neoplastic cells during cell proliferation and cell death. METHODS: Detailed analysis was performed on mouse tumor models of different growth rates using [18F]FDG, [6-13H]thymidine [3H]Thd (a precursor of DNA synthesis) and [125I]bovine serum albumin ([125I]BSA) (a marker of diffusion) with autoradiographic and histopathologic techniques and electron microscopy. RESULTS: The three compounds, [18F]FDG, [3H]Thd and [125I]BSA, showed different heterogeneous patterns of distribution within tumor tissue sections in neoplastic and non-neoplastic cellular elements. The uptake of [18F]FDG by prenecrotic (or necrobiotic) tumor cells surrounding focal necrotic cell debris was 1.5 to 2.3 times higher than that of viable tumor cells. Prenecrotic cells did not retain trapped [18F]FDG; therefore, the uptake was considered to be nonmetabolic. Inconspicuous cell membrane, vesicular cytoplasmic organelles and condensed nuclear chromatin were remarkable findings in the prenecrotic cells. A comparison of viable tumor cells in tumors undergoing different growth rates showed that the ratio of [18F]FDG uptake was similar to that of [3H]Thd uptake in each S-phase cell. Fluorine-18-FDG showed a cell cycle dependency, with a higher uptake observed in cells in G0/G1 and G2 phases of the cell cycle compared with the S and M phases. CONCLUSION: A passive mechanism of [18F]FDG uptake may exist in the necrobiotic/prenecrotic or hypoxic/anoxic cells in tumors. However, the discordance of [18F]FDG and [3H]Thd uptake may be the result of the different cell cycle dependency of tracer uptake in the same tumor.

Animals↗
PubMed1994

Microautoradiographic study for the differentiation of intratumoral macrophages, granulation tissues and cancer cells by the dynamics of fluorine-18-fluorodeoxyglucose uptake.

UNLABELLED: A substantial amount of macrophage infiltration occurs in both human and animal tumors. We previously showed that 2-deoxy-2-[18F]fluoro-D-glucose ([18F]FDG) uptake was higher in tumor-associated macrophages and young granulation tissues than in tumor cells. Differentiation of intratumoral non-neoplastic cells from neoplastic cells is important not only for the reduction of false-positives in FDG-PET tumor studies but also for patient management. METHODS: A time-course study was performed using micro- and macro-autoradiography and tissue distribution in C3H/He mice bearing transplanted syngeneic FM3A mammary carcinoma and MH134 hepatoma was evaluated to analyze the intratumoral cellular dynamics of [18F]FDG and 2-deoxy-D-[3H]glucose in vivo. RESULTS: The volume-doubling time in vivo was 1.3 days for MH134 and 4.9 days for FM3A, and the survival time of the host was 32.1 and 40.3 days, respectively. The peak uptake of both tracers in the tumor was 60 min after intravenous injection. The uptake by MH134 was 1.7-2.1 times higher than that by FM3A. The intracellular concentration as determined by counting the silver grains on micro-autoradiographic sections showed that the uptake by macrophages and focal small necrotic areas in both tumors was faster than the blood clearance until 15 min after tracer injection. CONCLUSION: Thus, non-neoplastic cellular elements can be differentiated from viable neoplastic cells by means of the dynamic analysis of [18F]FDG uptake.

Animals↗
PubMed1993

Treatment with a combination of low-density lipoprotein aphaeresis and pravastatin of a patient with drug-resistant nephrotic syndrome due to focal segmental glomerulosclerosis.

Results of recent animal studies have lent support to the hypothesis that hyperlipidaemia may contribute to renal injury. This report documents the case of a 15-year-old boy with drug-resistant nephrotic syndrome due to focal segmental glomerulosclerosis (FGS) who showed an improvement in renal function and proteinuria as a result of treatment with low-density lipoprotein aphaeresis (LDL-A) combined with pravastatin. Although further work is required to determine the efficacy of lipid-lowering therapy in progressive glomerular disease in humans, the combination of LDL-A and pravastatin is likely be included in the choice of treatment modalities available for patients with drug-resistant nephrotic syndrome due to FGS.

Adolescent↗
PubMed1993

Fluctuation of HTLV-I proviral DNA in peripheral blood mononuclear cells of HTLV-I-associated myelopathy.

To assess the immunopathological significance of the increased replication of human T-cell leukemia virus type I (HTLV-I) in HTLV-I-associated myelopathy/tropical spastic paraparesis (HAM/TSP) we investigated the dynamics of HTLV-I proviral DNA in peripheral blood mononuclear cells (PBMC) of HAM/TSP patients at different clinical stages. We compared the dynamics to those of asymptomatic HTLV-I carriers (AC). The estimation of the amount of HTLV-I proviral DNA was carried out by quantitative polymerase chain reaction of serially diluted DNA samples where it was feasible to titrate 0.04-80 copies per 100 PBMC. The proviral DNA quantified in six patients with HAM/TSP was 2-20 copies per 100 PBMC, while that in eight cases of AC was 0.04-8 copies per 100 PBMC. Thus, the amount of HTLV-I proviral DNA in HAM/TSP patients was 3-50 times as high as that of AC. When we followed up HAM/TSP patients for 1-3 years, the amount of HTLV-I proviral DNA fluctuated from 4 to 10-fold. These data suggest that the rate of HTLV-I replication increases in HAM/TSP and the amount of HTLV-I proviral DNA fluctuates in their clinical course. Fluctuation in the amount of HTLV-I proviral DNA may reflect dynamics of HTLV-I infected cell proliferation and immunological suppression in vivo in HAM/TSP patients.

Adult↗
PubMed1993

An autoaggressive process against bystander tissues in HTLV-I-infected individuals: a possible pathomechanism of HAM/TSP.

Human T lymphotropic virus type I (HTLV-I)-associated myelopathy/tropical spastic paraparesis (HAM/TSP) is a well-defined clinico-pathological entity in which the virus infection and the host immune responses are involved in the pathomechanism. It is generally agreed that the virus infection precedes the development of HAM/TSP and the infection is persistent during the course of disease. However, what plays the key role for the development of HAM/TSP remains to be elucidated. In this article, we emphasise the importance of the unique nature of HTLV-I-infected cells, which may have a potential ability to produce viral antigens outside of the blood flow, and we also review a variety of evidences supporting the following proposal. In our hypothesis, the supply of infected T cells from blood flow to central nervous system (CNS) is primary for the development of CNS lesions. Both anatomically determined hemodynamic conditions and adhesion molecule-mediated interactions between circulating infected T cells and endothelial cells may contribute to the localization of the main lesions. Following an induction of the HTLV-I antigens on the surface of infected T cells in CNS compartment, expansion of the responses of immunocompetent T cells against the viral proteins may result in CNS tissue damage which may be mediated by released cytokines. This is the first attempt to implicate a bystander damage mechanism in a human disease as an essential pathomechanism.

Autoimmunity↗
PubMed1993

A comparative study on protein incorporation of L-[methyl-3H]methionine, L-[1-14C]leucine and L-2-[18F]fluorotyrosine in tumor bearing mice.

Brain and tumor uptake of L-[methyl-3H]methionine (3H-Met), L-[1-14C]leucine (14C-Leu) and L-2-[18F]fluorotyrosine (18F-Tyr) and their incorporation into the acid-precipitable fraction (APF) were investigated in mice bearing FM3A-P0 and the higher metastatic FM3A-P15A mammary carcinomas in order to compare the potential of positron emitting analogs for measuring protein synthesis rates (PSR) in brain and tumors by positron emission tomography (PET). The total uptake of the 3H-Met by the brain was higher than those of two other amino acids. On the other hand, the incorporation rates into the APF in the brain and tumors were significantly faster with 14C-Leu compared to the others. Most of the 14C in the APF was identified in labeled proteins; however, considerable amounts of 3H were recovered in the lipid and RNA fractions, and 18F was also detected in the lipids. Among the positron emitting analogs of three amino acids, 11C-labeled Leu could be the most suitable for measuring PSR by PET. For all the amino acids, the total uptake and the APF both expressed as the % injected dose seemed slightly higher in the FM3A-P15A than in the FM3A-P0, although the differences did not reach statistical significance.

Animals↗
PubMed1993

Micro-autoradiographic method to study [18F]FDG uptake in mouse tissue.

A new micro-autoradiographic method using 18F (half-life: 109.8 min) was developed to detect 2-deoxy-2-[18F]fluoro-D-glucose ([18F]FDG) in mouse tissues. A linear relationship between the number of silver grains and corresponding 18F-radioactivity was observed. The half-distance of spatial resolution with 18F-micro-autoradiography was about 2.1 microns. The grain number increased with exposure time until 6 h, but 7 h or longer exposure induced a characteristic latent image fading. After i.v. injection of [18F]FDG into normal mice, the highest grain level among the hippocampal regions of the brain was found in the stratum lacunosum-moleculare followed by the dentate molecular and the stratum oriens. All granular and pyramidal cell layers showed lower grain levels than neuropil fields. In the pyramidal cell fields, the CA3a contained the highest grain level and the CA4 the lowest. This method requires only 4 h exposure and can be applied to all 18F-tracers to assess the tracer-tissue association.

Animals↗
PubMed1993

Cellular accumulation of 18F-labelled boronophenylalanine depending on DNA synthesis and melanin incorporation: a double-tracer microautoradiographic study of B16 melanomas in vivo.

The cellular distribution of 4-borono-2-[18F]fluoro-L-phenylalanine ([18F]FBPA, an analog of p-boronophenylaline), a potential agent for boron neutron capture therapy (BNCT), and [6-3H]thymidine ([3H]Thd, a DNA precursor) in murine two B16 melanoma sublines and FM3A mammary carcinoma was studied in vivo using double-tracer microautoradiography. Tumour volume, tumour age, cell density in the tissues and the proportion of S phase cells in the cell cycle were the same in the three tumour models. Volume doubling time, which represents tumour growth rate, was fastest in B16F10, followed by B16F1 (P < 0.05), the slowest being in FM3A (P < 0.001). The rate of DNA synthesis in S phase cells corresponded to the volume doubling time. The greatest amount of [18F]FBPA was observed in S phase melanocytes and the lowest amount was found in non-S phase non-melanocytes. The [18F]FBPA accumulation was primarily related to the activity of DNA synthesis and, secondarily, to the degree of pigmentation in melanocytes. The therapeutic efficacy of BNCT with p-boronophenylalanine may be greater in melanoma that exhibits greater DNA synthesis activity and higher melanin content.

Animals↗
PubMed1993

Limited sequence divergence of HTLV-I of Indian HAM/TSP patients from a prototype Japanese isolate.

Nucleotide sequences of two HTLV-I proviruses isolated from Indian patients with HAM/TSP were analyzed. The sequence data of the env, pX, and LTR regions showed 98-99% homologies with the prototype HTLV-I, ATK-1, isolated from a Japanese ATL patient, indicating that HTLV-I isolates in India and Japan are similar, with minor variations. However, certain small sequences of noncoding regions in the pX and LTR showed differences of 6.1 and 7.2%, respectively, thus the conclusion could vary depending on the regions and length of the sequences used for comparison.

Adult↗
PubMed1993

Re-evaluation of amino acid PET studies: can the protein synthesis rates in brain and tumor tissues be measured in vivo?

The significance of L-[methyl-11C]methionine (11C-Met), L-[1-11C]leucine (11C-Leu) and L-2-[18F]fluorotyrosine (18F-Tyr) for measuring protein synthesis rates in the brain and in tumors by PET was re-evaluated. Tissue uptake and protein incorporation of 3H-Met, 14C-Leu and 18F-Tyr were investigated in mice bearing the FM3A mammary carcinoma. In the control group, the uptake of all three tracers in the brain and FM3A and their incorporation into the acid-precipitable fraction (APF) increased over 60 min. When the protein synthesis in vivo was inhibited by cycloheximide, the incorporation of all three tracers into the APF was significantly reduced to 6%-32% and 3%-11% of the control in the brain and FM3A, respectively. Under these conditions, total uptake of 14C-Leu in the brain and FM3A decreased rapidly, and most of the 14C in the APF was detected as proteins. On the other hand, 3H-Met and 18F-Tyr uptake continued to increase, and significant amounts of radioactivity were incorporated into nonprotein materials. In mice given ouabain to inhibit amino acid transport, total uptake of all three amino acids by FM3A was reduced to 67%-74% of the control 5 min postinjection. These results demonstrate that uptake of the three amino acids is affected by alterations in the amino acid transport system in the brain and tumor tissues, but that only 14C-Leu uptake reflects protein synthesis rates.

Amino Acids↗
PubMed1992

Frequent clonal proliferation of human T-cell leukemia virus type 1 (HTLV-1)-infected T cells in HTLV-1-associated myelopathy (HAM-TSP).

Human T-cell leukemia virus type 1 (HTLV-1) integrates its proviruses into random sites in host chromosomal DNA. Random integration of the proviruses was observed in asymptomatic HTLV-1 carriers and patients with HTLV-1-associated myelopathy (HAM/TSP). However, clonal integration has been reported in patients with adult T-cell leukemia (ATL), including that in the smoldering, chronic, and acute states, indicating clonal expansion of infected cells. In this study, we found that about 20% of HAM/TSP patients and their seropositive family members harbored subpopulation(s) of clonally proliferated cells infected with HTLV-1, although they still maintained randomly infected cells as a major population. These clones were stable during examination periods of 4 months to 3 years. However, these carriers or HAM/TSP patients did not show any significant indication of ATL. This extremely high frequency of clonal expansion of HTLV-1-infected cells indicates that some clones of HTLV-1-infected cells have a tendency to proliferate more efficiently than the other population without malignant transformation.

Cell Division↗
PubMed1992

Cerebrotendinous xanthomatosis: cranial CT and MRI studies in eight patients.

We report the findings on cranial computed tomography (CT) and magnetic resonance imaging (MRI) and their correlation with the clinical manifestations, disease severity and biochemical abnormalities in eight patients with cerebrotendinous xanthomatosis. CT revealed cerebral atrophy in seven cases, cerebellar atrophy in four and focal low density lesions in the cerebral white matter in two. T2-weighted MRI showed high signal lesions in the cerebral white matter, focal in four cases and diffuse in one, and in the globus pallidus in three patients, two of whom also had lesions in the cerebellar white matter. While severely affected patients showed variable CT and MRI abnormalities, our cases did not show the dramatic findings expected from the neurological manifestations. Diffuse lesions in the cerebral and cerebellar white matter have been emphasized in previous reports, but in our study the focal lesions in the cerebral white matter were also present; the globus pallidus was frequently involved.

Achilles Tendon↗
PubMed1992

Investigation of tumor metastatic potential with N-[18F]fluoroacetyl-D-glucosamine.

In order to investigate the metastatic potential of tumors in vivo by measuring hyaluronic acid metabolism, C57BL/6 mice with B16 melanoma variants and C3H/He mice with FM3A tumor variants were evaluated using N-[18F]fluoroacetyl-D-glucosamine (18F-GlcNFAc). The uptake of 18F-GlcNFAc was slightly higher (P less than 0.05) in B16-F10 tumors (high metastatic potential) than in B16-F1 (low metastatic potential). Analysis of metabolites showed that acid-insoluble fraction was the largest one in the liver by 60 min, whereas in the tumors, phosphates fraction was the major metabolite. Slower metabolism in tumors was suggested, and it may be one of the reasons for the difficulty of detecting the characteristics of their hyaluronic acid synthesis. 18F-GlcNFAc uptake by FM3A variants showed no significant correlation with their metastatic potential. In addition, N-acetyl-D-[1-14C]glucosamine, 2-deoxy-D-[1-14C]glucose and [6-3H]thymidine failed to demonstrate any difference between tumors' metastatic variants in vivo.

Acetylglucosamine↗