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Biomedical subjects

H Kamada

Publications and source records attributed to H Kamada.

At least 109 records · Page 6Linked to original sources
PubMed1997

Effect of selenium on cultured bovine luteal cells.

The present study examined the possibility that selenium (Se) directly affects the corpus luteum (CL) and contributes to the maintenance of reproductive function. Primary culture of bovine CL was used to investigate this possibility. Se addition from 5 to 200 ppb elevated progesterone concentration of the culture medium in a dose-dependent manner which was associated with an increase in cell proliferation rather than an increase in progesterone production per cell, and decreased the lipid peroxide content of luteal cells. However, the luteal cells in which hormone production was increased by LH treatment, accumulated more lipid peroxide than in control incubations. The results suggest that Se is involved in the degradation of lipid peroxides which are by-products of active progesterone production by luteal cells. The increase of cell proliferation observed in this experiment was associated with the removal of these toxic peroxides.

Analysis of Variance↗
PubMed1997

ESR imaging of the rat brain with a nitroxide radical perfused by in vivo microdialysis.

We report here our investigation of the spatial distribution of free radicals using an electron spin resonance (ESR)-imaging system combined with an in vivo brain microdialysis method, which was performed in the resonator of the ESR-imaging system. A nonmagnetic cannula, newly developed in this study, was used for the perfusion of the exogenous free radicals agent. A nitroxide, 3-carbamoyl-2,2,5,5-tetramethylpyrrolidine-1-oxyl (carbamoyl PROYXL), was used as the imaging agent in saline solution at a concentration of 0.3 M, which was perfused into the right caudate putamen of the rat at 2 microliters/min by a microinfusion pump. Two-dimensional ESR projection of the Z-X plane, which was clearly distinguished (about phi 10 mm) from the nonperfused brain area, was obtained 6 h after the beginning of perfusion of carbamoyl PROXYL. The present method is considered to be a useful tool to introduce stable free radicals into a specific area of the brain.

Animals↗
PubMed1997

In vivo ESR-CT imaging of the liver in mice receiving subcutaneous injection of nitric oxide-bound iron complex.

ESR measurements and ESR-CT imaging of subcutaneously (SC) injected nitric oxide (NO)-bound iron complexes were conducted on the upper abdomen of live mice. The use of NO-bound iron complex with N-(dithiocarboxy)sarcosine resulted in a clear ESR-CT image showing high intensity areas in the ventral regions, while other NO-bound iron complexes with N-methyl-D-glucamine dithiocarbamate or N,N-diethyl-dithiocarbamate were inappropriate because of low S/N ratios. To investigate the distributions of SC injected NO-bound iron complexes in the abdomens of mice, we measured ESR signals in resected abdominal organs. The signal amplitude was higher in the resected liver than in the resected gastrointestinal organs or the blood samples. The findings suggest that the high intensity areas in the ESR-CT images thus obtained correspond to the liver.

Animals↗
PubMed1997

Temporal brain imaging by a rapid scan ESR-CT system in rats receiving intraperitoneal injection of a methyl ester nitroxide radical.

We performed in vivo ESR-CT (electron spin resonance-computed tomography) on rats' heads, in which the blood-brain barrier-permeable nitroxide radical, 3-methoxycarbonyl-2,2,5,5-tetramethylpyrrolidine-1-oxyl (PCAM) was injected intraperitoneally, using a rapid scan ESR-CT system operating at 700 MHz. In a spatiotemporal study we found that different regions of the brain showed differences in the rate of decay of the radical. Repeated injection of PCAM gave clear ESR-CT images of the brain. We think that the present method is useful for evaluating the capacity to eliminate exogenous free radicals in some parts of the brain.

Animals↗
PubMed1997

A CT using longitudinally detected ESR (LODESR-CT) of intraperitoneally injected nitroxide radical in a rat's head.

We have developed an in vivo longitudinally detected ESR (LODESR) imaging system operating at 700 MHz based on a loop-gap resonator and a pair of saddle-type pickup coils. A good linear relationship between the LODESR signal intensity and the applied power in a range up to 15.8 W was obtained. The detection of LODESR signals was barely affected by variations in the resonant properties. The characteristic of LODESR is suitable for in vivo examination. Using this system, we succeeded in obtaining LODESR-CT images of the head region of a rat after the intraperitoneal injection of a nitroxide radical.

Animals↗
PubMed1997

Generation of lipid radicals in the hippocampal extracellular space during kainic acid-induced seizures in rats.

We report direct electron spin resonance (ESR) evidence of extracellular free radical formation during kainic acid-induced seizures obtained using in vivo brain microdialysis in freely moving rats. Saline solution containing the spin trap agent alpha-(4-pyridyl-N-oxide)-N-tert-butylnitrone was perfused through the hippocampus. ESR analysis of the dialysate samples revealed a six-line spectra, for which the hyperfine coupling constants corresponded to those of the ESR signal from the lipoxygenase/linoleic acid system, a lipid radical generating system. This result is direct evidence that lipid peroxidation of the neuronal membrane progresses during seizure activity. Increased formation of lipid radicals may participate in the cascade of reactions leading to neuronal damage in the hippocampus following kainic acid-induced seizure activity.

Animals↗
PubMed1997

Hydrogen peroxide augmentation in a rat striatum after methamphetamine injection as monitored in vivo by a Pt-disk microelectrode.

We fabricated a Pt-disk microelectrode (diameter 30 microns) to conduct differential double-pulse amperometry (first step: 750 mV, 1 s; second step: 1,100 mV, 1 s) to detect hydrogen peroxide in the brain of a freely moving animal. This measurement determined hydrogen peroxide (detection limit, 0.03 microM) without any observable influence from other oxidizable species, such as dopamine (DA), ascorbic acid, or uric acid. The electrode was implanted into the right striatum of a rat. After intraperitoneal injection of methamphetamine (MAP), hydrogen peroxide concentrations were directly detected while the behavioral changes were monitored. MAP injection led to significant augmentation of hydrogen peroxide, the elevation of which depended on the dose of MAP. This is consistent with a previous report on the increase of DA-release caused by amphetamines and indirect evidence of the production of hydrogen peroxide via DA-metabolism.

Animals↗
PubMed1997

An extracellular insoluble inhibitor of cysteine proteinases in cell cultures and seeds of carrot.

An 18 kDa extracellular insoluble protein (EIP18) was found previously in amorphous particles suspended in the culture medium and in the interspaces of cell clusters of carrot (Daucus carota L.) callus, as well as in the extracellular spaces of carrot seeds, being located both in the embryo and at the inner edge of the endosperm. We purified EIP18 by washing the amorphous particles with the mixture of Triton X-100, NaCl and ethylenediaminetetraacetic acid (EDTA). We determined several partial amino acid sequences, and then we cloned and sequenced a cDNA for EIP18. EIP18 was found to consist of 133 amino acid residues that included a signal sequence, but it did not contain cysteine, sites for N-linked glycosylation or hydrophobic regions. Since its sequence was found to be homologous to that of inhibitors of cysteine proteinases, namely cystatins, EIP18 was renamed EICC (extracellular insoluble cystatin of carrot). EICC expressed in yeast was also found in an insoluble form in yeast cell walls. EICC prepared from the culture medium of carrot cells inhibited commercial cysteine proteinases and a proteinase extracted from germinating carrot seeds. The expression of the gene for EICC was detected in developing seeds, and the level of its transcript was markedly enhanced upon treatment of somatic embryos with abscisic acid.

Amino Acid Sequence↗
PubMed1997

Amino acid changes in the putative replicase of tomato mosaic tobamovirus that overcome resistance in Tm-1 tomato.

Replacement of Gln-979 by Glu in the putative replicase of tomato mosaic tobamovirus is sufficient to overcome Tm-1 resistance in tomato. It has been suggested that this change decreases the local net charge of the protein which is important in overcoming the resistance. In this study, we constructed five mutants, designated TLAsn, TLAsp, TLHis, TLLys and TLArg, in which Gln-979 was replaced by Asn, Asp, His, Lys and Arg, respectively, and analysed their abilities to overcome Tm-1 resistance. Unexpectedly, not only TLAsp, but also TLLys multiplied in tomato cells with the Tm-1 gene. TLAsn and TLArg multiplied at a reduced level. Multiplication of TLHis was virtually almost inhibited. From these results, it is unlikely that a decrease in the local net charge is the major reason for overcoming Tm-1 resistance.

Base Sequence↗
PubMed1997

Spatiotemporal expression of C-CAM in the rat placenta.

We investigated the expression of the immunoglobulin superfamily cell adhesion molecule, C-CAM, in developing and mature rat placenta. By immunohistochemical staining at the light microscopic level, no C-CAM-expression was seen before Day 9 of gestation, when it appeared in the trophoblasts of ectoplacental cones. On Day 10.5, spongiotrophoblasts and invasive trophoblasts around the maternal vessels of the decidua basalis were stained positively. On Day 12.5, C-CAM was detected in the spongiotrophoblasts of the junctional layer, but labyrinth trophoblasts and secondary giant trophoblasts were not stained. On Day 17.5, C-CAM was found only in the labyrinth and lacunae of the junctional layer. At this stage, both the labyrinth cytotrophoblasts of the maternal blood vessels and the endothelial cells of the embryonic capillaries were strongly stained. Placental tissues from gestational Days 12.5 and 17.5 were analyzed by immunoelectron microscopy to determine the location of C-CAM at the subcellular level. On Day 12.5, positive staining of the spongiotrophoblasts was observed, mainly on surface membranes and microvilli between loosely associated cells. On Day 17.5, staining was found primarily on the microvilli of the maternal luminal surfaces of the labyrinth cytotrophoblasts, and both on the luminal surface and in the cytoplasm of endothelial cells of the embryonic vessels. RT-PCR analysis and Southern blotting of the PCR products revealed expression of mRNA species for both of the major isoforms, C-CAM1 and C-CAM2. Immunoblotting analysis of C-CAM isolated from 12.5-day and 14.5-day placentae showed that it appeared as a broad band with an apparent molecular mass of 110-170 kD. In summary, C-CAM was strongly expressed in a specific spatiotemporal pattern in trophoblasts actively involved in formation of the placental tissue, suggesting an important role in placental development. In the mature placenta, C-CAM expression was confined to the trophoblastic and endothelial cells lining the maternal and embryonic vessels, respectively, suggesting important functions in placental physiology.

Animals↗
PubMed1997

Spatiotemporal ESR-CT study on the metabolism of spin-labeled polysaccharide in a mouse.

A spatiotemporal ESR-CT study, rapid three dimensional ESR imaging by which distribution and metabolism of radicals in a small region in a living body can be followed, was carried out by intravenously administering spin-labeled polysaccharides to mice. The in vivo lifetime of spin-labeled hydroxyethylstarch (TEMPO-HES) was shorter than that of spin-labeled dextran (TEMPO-DX), suggesting that the clearance of their spins depended on the stability of the polymer chains to the hydrolysis. Spatiotemporal image at the kidney domain of a mouse showed that low molecular weight TEMPO-DX was excreted into the kidney and then was transferred to the bladder. Time dependence of the ESR intensity of TEMPO-HES at certain points in the liver domain had a maximum showing that TEMPO-HES was taken into the liver and then was decomposed there by the metabolism, but the rate of decrease in the intensity was different in each part in the liver because of the difference in metabolic function. The rate of decrease of TEMPO-DX in the blood was slowed by the prior administration of dextran, meaning that the intake of TEMPO-DX into the liver from the blood was suppressed by the dextran.

Animals↗
PubMed1997

Synthesis of spin labels for ESR imaging of living rat head.

Spin labels (7, 10, 13, 16, 22, 27) were synthesized from piperidinyloxyl (1), pyrrolidinyloxyl (2), and oxazolidinyloxyl (3). These compounds were injected into the carotid artery of anesthetized rats, and the ESR spectra of the rat brain were immediately recorded by the use of an L-band ESR spectrometer. Based on the spectra obtained, we considered whether or not these spin labels can pass the blood brain barrier and bind to brain tissue components.

Animals↗
PubMed1997

Immunopharmacological studies on collagen-induced arthritis in dark Agouti (DA) rats.

Dark Agouti (DA) and Lewis rat strains were tested for susceptibility to collagen-induced arthritis (CIA) and for development of cellular and humoral immune responses to type II collagen (CII). All of the DA rats developed arthritis following a single intradermal injection of more than 20 microg of CII (130-150 microg/kg rat weight) and showed a swelling rate of more than 100% in the hind paws. The swelling rate showed little deviation among the animals. There was a strong correlation between the severity of the arthritis and the strength of the immune response to CII in DA rats with CIA. Following immunization with even 800 microg of CII (3.8-4.2 mg/kg rat weight), Lewis rats showed a maximum rate of hind paw swelling of only 45%. In the pharmacological studies, prednisolone, indomethacin, FK-506 and mizoribine all suppressed arthritis in DA rats. These findings suggest that DA rats are more susceptible to CIA than Lewis rats and that CIA in DA rats as well as in Lewis rats is serviceable as an experimental animal model of rheumatoid arthritis.

Animals↗
PubMed1997

Inhibitory mechanism of mizoribine on the antibody production of mouse B cells stimulated with lipopolysaccharide.

It has been reported that the immunosuppressant mizoribine (MZR) inhibits T cell proliferation by depleting intracellular guanine nucleotides via competitive inhibition of inosine 5'-monophosphate (IMP) dehydrogenase in the purine metabolism pathway. This study was performed to determine if the mechanism by which MZR suppresses the proliferation of mouse B cells and antibody production by these cells is dependent on the depletion of intracellular guanine nucleotides. Stimulation of purified splenic B cells of mice with lipopolysaccharide (LPS), a mitogen to B cells, increased both proliferation and antibody production. MZR suppressed both of these functions in a dose-dependent fashion. MZR also caused a decrease in the amount of intracellular guanosine 5'-triphosphate (GTP). When the cultures were grown on plates containing guanosine plus 8-aminoguanosine, the amount of intracellular GTP, which had been reduced by MZR, was restored. Furthermore, the repletion of GTP pools restored both proliferation and antibody production almost to their previous levels. These results suggest that MZR suppresses antibody production and proliferation of B cells by acting directly on B cells. Furthermore, it is suggested that the inhibitory effect of MZR on antibody production, as well as on T cell proliferation, is dependent on the decrease in intracellular guanine nucleotide pools of mouse B cells.

Animals↗
PubMed1997

PEGylation of interleukin-6 effectively increases its thrombopoietic potency.

The in vivo thrombopoietic activity of polyethylene glycol-modified interleukin-6 (MPEG-IL-6), in which 54% of the 14 lysine amino groups of IL-6 were coupled with PEG, was compared to that of native IL-6. Native IL-6 and MPEG-IL-6, which showed about 51% of the specific bioactivity of native IL-6, were administered subcutaneously to mice every 2 days for 7 days. Native IL-6 increased not only the peripheral platelet count, but also the plasma-IgG1 level in a dose-dependent manner. MPEG-IL-6 showed about 500 times higher thrombopoietic potency than native IL-6. Further, in comparison to native IL-6, MPEG-IL-6 did not enhance IgG1 production as much as it enhanced platelet production. MPEG-IL-6 significantly stimulated platelet recovery in mice treated with 5-fluorouracil, whereas the administration of native IL-6 had a negligible effect. The plasma half-life of MPEG-IL-6 was about 100-fold longer than that of native IL-6. The decrease in the plasma clearance of MPEG-IL-6 was thought to be due, in part, to the shielding of the proteolytic sites in the IL-6 molecule by the PEG chain. The uptake of IL-6 by the reticuloendothelial system, such as the liver and spleen, was markedly limited by PEGylation. The PEGylation of IL-6 markedly enhanced the blood-residency of IL-6, resulting in effective augmentation of its thrombopoietic activity and a marked decrease in its side-effects. These findings suggest that MPEG-IL-6 may be a potential candidate for thrombopoietic agent.

Animals↗
PubMed1997

[Expression of HGF and c-met/HGF receptor mRNA in brains of normal rats and in phaeochromocytoma cells PC-12 of rats treated with NGF].

Gene expression of HGF and c-met proto-oncogene was examined during rat brain development and in cultured PC-12 cells, using reverse-transcriptase (RT)-polymerase chain reaction (PCR) technique. The both mRNAs of HGF and c-met proto-oncogene were remained at low levels in the middle and late stages of gestation (E-13 and E-18). After birth, and the level of both mRNA expression suddenly increased. During P-1 and P-12, their high level of expression continued and then decreased in P-20 and adult brain. Both HGF mRNA and c-met photo-oncogene mRNA were transiently expressed between day 2 and day 5, and disappeared in cultured PC-12 cells treated with NGF. The neurites of PC-12 cells that were treated with anti-sense oligonucleotides of HGF and c-met proto-oncogene, were shorter and fewer in number than untreated control cells. We conclude that neurite extension of PC-12 cells treated with NGF may ensue by way of c-MET protein activation and signal transduction pathways. Thus, c-MET protein activation and up-regulation of the two mRNAs may also play an important role in neuronal maturation in the developing rat brain.

Animals↗
PubMed1996

Spectroscopic characterization of nitrosylheme in nitric oxide complexes of ferric and ferrous cytochrome c' from photosynthetic bacteria.

Reactions of ferric and ferrous cytochromes c' from four photosynthetic bacteria (Rhodobacter capsulatus ATCC 11166, Rhodopseudomonas palustris ATCC 17001, Rhodospirillum rubrum ATCC 11170, and Chromatium vinosum ATCC 17899) with nitric oxide have been investigated by electronic absorption and electron paramagnetic resonance spectroscopies. The heme iron(III) of these ferric cytochromes c' has been recently reported to be in a quantum mechanically admixed (S = 5/2, 3/2) state [Fujii, S., Yoshimura, T., Kamada, H., Yamaguchi, K., Suzuki, S., Shidara, S. and Takakuwa, S. (1995) Biochim. Biophys. Acta 1251, 161-169]. The affinity of ferric cytochromes c' for NO among these bacterial species (C. vinosum > Rps. palustris approximately Rb. capsulatus >> R. rubrum) was apparently related to the S = 3/2 content in the or der. In the reaction of ferrous cytochrome c' with NO, six- and five-coordinated nitrosylhemes, which represent species with and without a ligand at the axial position trans to nitrosyl group, have been formed. The content of six-coordinated nitrosylheme in NO-ferrous cytochrome c' has been determined to be Rb. capsulatus approximately Rps. palustris > C. vinosum < R rubrum, suggesting that a stability of iron-to-histidine bond decreases with this order. The NO reactions of ferric and ferrous cytochromes c' from photosynthetic bacteria have been compared with those of cytochromes c' from denitrifying bacteria.

Cytochrome c Group↗