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Biomedical subjects

H Kamada

Publications and source records attributed to H Kamada.

At least 127 records · Page 7Linked to original sources
PubMed1996

Molecular design of hybrid tumour necrosis factor-alpha. II: The molecular size of polyethylene glycol-modified tumour necrosis factor-alpha affects its anti-tumour potency.

To design hybrid tumour necrosis factor-alpha (TNF-alpha) applicable to systemic anti-tumour therapeutic use, we assessed the relationships among the molecular size of hybrid TNF-alpha, in vitro bioactivity and in vivo anti-tumour potency. Natural human TNF-alpha was covalently modified with polyethylene glycol (PEG) of various number-average molecular weights (Mn = 2000, 5000, 12,000). The in vitro bioactivity of PEG-modified TNF-alpha s decreased with an increase in the degree of PEG modification, irrespective of the molecular weight of PEG. This decrease in the specific bioactivity markedly increased with an increase in the molecular weight of the attached PEG. The in vivo anti-tumour effects of the hybrid TNF-alpha s with a molecular size from 100 to 110 kDa, which had more than 50% of specific bioactivity of native TNF-alpha, were significantly superior to other PEG-TNF-alpha s. These hybrid TNF-alpha s showed over ten times greater anti-tumour effects than native TNF-alpha. Thus, the molecular size, which was determined by the degree of PEG modification and PEG molecular weight, influences the specific activity and anti-tumour effects of hybrid TNF-alpha.

Animals↗
PubMed1996

In vivo EPR detection and imaging of endogenous nitric oxide in lipopolysaccharide-treated mice.

Nitric oxide (NO), a simple diatomic free radical, is known to play a critical physiological role in diverse organisms. An iron complex, with N-(dithiocarboxy)sarcosine (Fe-DTCS), has a high affinity for endogenous NO and can trap, stabilize, and accumulate it. The stable NO adduct thus formed is detectable at room temperature with electron paramagnetic resonance (EPR) spectrometry. We report in vivo EPR imaging of endogenous NO, trapped by an Fe-DTCS complex, in the abdomen of a live mouse. To our knowledge, this is the first report on EPR imaging of endogenous free radicals produced in vivo. This EPR imaging method will be useful for the noninvasive investigation of the spatial distribution of NO in pathologic organs or tissues.

Animals↗
PubMed1996

Transient increase in the level of mRNA for a germin-like protein in leaves of the short-day plant Pharbitis nil during the photoperiodic induction of flowering.

A cDNA corresponding to an in vivo labeled protein whose level increased during flower-inductive darkness in the cotyledon of the short-day plant Pharbitis nil Choisy cv. Violet was isolated and characterized. The deduced amino-acid sequence of the protein (designated PnGLP; P.nil germin-like protein) showed homology to that of a GLP of Sinapis alba, a leaf protein, the mRNA accumulation of which showing circadian oscillations. PnGLP mRNA was detected specifically in the cotyledon and leaf, in particular, in the young expanded cotyledon and leaf. Accumulation of PnGLP mRNA increased transiently during flower-inductive darkness and peaked at a time that corresponded approximately to the critical night length. This mRNA peak was reduced by a brief exposure to red light at the 8th hour of darkness. The level of PnGLP mRNA peaked about 10 h from the beginning of the dark period, whereas it was reported that the level of mRNA for GLP of a long-day plant S. alba increased about 14 h from the beginning of the light period. Thus, the different time courses of accumulation of the mRNAs for leaf-specific GLPs appear to reflect the differences in photoperiodic responses of each plant.

Amino Acid Sequence↗
PubMed1996

In vivo anti-tumor efficacy of polyethylene glycol-modified tumor necrosis factor-alpha against tumor necrosis factor-resistant tumors.

We previously reported that the optimally PEGylated tumor necrosis factor-alpha (MPEG-TNF-alpha), in which 56% of the TNF-alpha-lysine amino groups were coupled with polyethylene glycol (PEG), had about 100-fold greater anti-tumor effect than native TNF-alpha. Here, we assessed the usefulness of MPEG-TNF-alpha as a systemic anti-tumor therapeutic drug, using B16-BL6 melanoma and colon-26 adenocarcinoma, which have been reported to be resistant to TNF-alpha in vivo, as compared with Meth-A fibrosarcoma. MPEG-TNF-alpha markedly inhibited the growth of both tumors without causing any TNF-alpha-mediated side-effects, whereas native TNF-alpha had no anti-tumor effects and caused adverse side-effects. In addition, MPEG-TNF-alpha drastically inhibited the metastatic colony formation of B16-BL6 melanoma. MPEG-TNF-alpha may, thus, be a potential systemic anti-tumor therapeutic agent.

Adenocarcinoma↗
PubMed1996

The effect of SM-8849 on experimental arthritis in mice.

The effect of a novel thiazole derivative, SM-8849, on experimental arthritis in mice was studied and compared to that of prednisolone. SM-8849 and prednisolone reduced the incidence and severity of type II collagen-induced arthritis in mice, as assayed by clinical observation and histopathological studies. Although both agents inhibited type II collagen-induced delayed type hypersensitivity (DTH) in arthritic mice, SM-8849 did not affect the production of humoral antibodies to type II collagen. To examine the inhibitory mechanism of SM-8849, the effects on T cell-dependent allergic inflammation were studied. SM-8849 clearly inhibited T cell-dependent reactions including staphylococcal enterotoxin B (SEB)-induced arthritis, SEB-induced CD25 expression on T cells and sheep red blood cell (SRBC)-induced DTH reaction. SM-8849, however, had no effect on the production of humoral antibody forming cells in the spleen of mice immunized with SRBC. These results indicate that inhibition of type II collagen-induced arthritis by SM-8849 is mainly due to the inactivation of T cells that are related to DTH reaction.

Adjuvants, Immunologic↗
PubMed1996

Effect of mizoribine on effector T cell-mediated immune responses in mice.

T cells play a principal role in cellular immunity and govern the regulatory mechanism in humoral immunity. Therefore, T cells play a key role as either effectors or regulators in the immune network. Mizoribine (MZR), an immunosuppressive agent, suppresses both humoral and cellular immunity by acting on both T cells and B cells. In this study, we examined the effect of MZR on various effector T cell-mediated immune responses in mice. MZR prolonged skin graft survival and suppressed a localized graft-versus-host reaction (GvHR) and sheep red blood cell (SRBC)-induced delayed-type hypersensitivity (DTH) reaction. In a collagen-induced arthritic mice model, MZR reduced the arthritic index and the swelling of the hind limbs. Furthermore, MZR suppressed both bone damage and histopathological changes in the hind limbs. Interestingly, MZR markedly suppressed the DTH reaction to type II collagen (CII) but had no effect on anti-CII antibody levels in this arthritic model. In these models, effector T cells such as cytotoxic T lymphocyte (CTL) and TDTH cell play an important part in the development of these reactions. It is suggested that MZR inhibited these reactions via the inhibition of the effector T cell-mediated immune response. Therefore, it is also suggested that the suppressive effect of MZR on clinical rejection and autoimmune disease is based on its suppression of the effector T cell-mediated immune response, that is cellular immunity, in addition to humoral immunity.

Animals↗
PubMed1996

Synthesis of isomelamines and isocyanurates and their biological evaluation.

The reaction of cyanogen bromide (1) with primary amines (2a-p), including arylmethylamines (2l-p), gave the corresponding cyanamides (3a-p). Trimerization of 3a-p gave 1,3,5-trisubstituted 2,4,6-triiminohexahydro-1,3,5-triazines (isomelamines) (4a-p), which were treated with hydrochloric acid to give the corresponding 1,3,5-trisubstituted 2,4,6-trioxohexahydro-1,3,5-triazines (isocyanurates) (5a-c, f) and 1,3,5-trisubstituted 2-imino-4,6-dioxohexahydro-1,3,5-triazines (5b'-e'). Biological evaluation of 4a-p, 5a-c,f, and 5b'-e' was carried out, and some of these compounds showed bronchodilator and positive inotropic activities.

Animals↗
PubMed1996

Effect of mizoribine on collagen-induced arthritis in mice.

This study examines the effect of mizoribine (MZR), an immunosuppressant, on collagen-induced arthritis in mice. DBA/1J mice, immunized on days 0 and 21 with 200 micrograms of type II collagen in complete Freund adjuvant, were treated with various doses of MZR for 12 weeks, beginning on the day after the primary immunization. MZR reduced the arthritis score in a dose-dependent fashion, showing significant suppression, even at a dose of 10 mg/kg. At doses of more than 20 mg/kg, MZR also significantly suppressed bone damage in the hind limbs. MZR significantly suppressed the delayed-type hypersensitivity response to type II collagen, but only slightly decreased anti-type II collagen antibody levels. MZR restored the L3T4+/Lyt-2+ ratio, which was increased in arthritic mice, to the level found in normal mice. These findings show that MZR suppresses collagen-induced arthritis and bone damage in mice, and suggest that the inhibitory effect of MZR is based on its suppression of cellular immunity. These results provide a theoretical basis for the clinical use of MZR in rheumatoid arthritis.

Animals↗
PubMed1996

Molecular design of hybrid tumor necrosis factor-alpha III: polyethylene glycol-modified tumor necrosis factor-alpha has markedly enhanced antitumor potency due to longer plasma half-life and higher tumor accumulation.

We have reported that chemical modification of tumor necrosis factor-alpha (TNF-alpha) with polyethylene glycol (PEG) markedly increases its antitumor potency without any adverse side effects. MPEG-TNF-alpha, especially, in which 56% of the lysine amino groups of TNF-alpha are coupled with PEG, exhibits 100-fold more antitumor activity in vivo than native TNF-alpha in the Meth-A murine sarcoma model. In this study, we investigated the pharmacokinetics of PEG-modified TNF-alpha with various molecular sizes to clarify the mechanisms of the enhanced antitumor potency of MPEG-TNF-alpha. The plasma half-lives of modified TNF-alpha increased with increasing molecular size. The decreased plasma clearance of modified TNF-alpha was partially caused by the shielding effect of the proteolytic sites in TNF-alpha by the attached PEG and the decreased transport from blood to various tissues. Almost all native TNF-alpha was uniformly distributed to the kidney and reticuloendothelial system within 1 hr of an intravenous administration, and rapidly disappeared from these tissues at 3 hr. However, very little native TNF-alpha was transported into the tumor. The absolute distributed amount and distribution profile of modified TNF-alpha to tissues other than the tumor were the same as those of native TNF-alpha, whereas the plasma levels of the modified TNF-alpha were higher than plasma levels of the native TNF-alpha. The tumor distribution of modified TNF-alpha was markedly enhanced compared with native TNF-alpha and gradually increased over time. About 9-fold more MPEG-TNF-alpha was distributed to the tumor than native TNF-alpha. Thus, we found that the marked increase in the antitumor potency of PEG-modified TNF-alpha resulted from the enhanced blood residency and tumor accumulation. The antitumor effect of MPEG-TNF-alpha against sarcoma-180 other than Meth-A fibrosarcoma was also about 100 times greater than that of native TNF-alpha when systemically administered. The optimal PEGylation of TNF-alpha facilitated its antitumor potency and MPEG-TNF-alpha may be useful systemic antitumor therapeutic drug.

Animals↗
PubMed1996

[Up-regulation of NGF, trkA, Fas, down-regulation of bcl-2, and induction of apoptosis by propentofylline in human glioma cell lines].

Propentofylline (PPF) has been reported to stimulate the synthesis/secretion of nerve growth factor (NGF) by cultured mouse astroglial cells. In the present study, we examined whether PPF stimulates NGF synthesis in human glioma cell lines, the same as in mouse astroglial cells, and if so, whether NGF has a biological effect on glioma cells. After administration of PPF into the glioma cell lines, we investigated morphological changes and gene and protein expression of NGF, trkA, Fas and bcl-2 by using GFAP staining. Western blotting, and RT-PCR. Glioma cells showed definite morphological changes, including expansion of astrocytic processes, cytoplasmic enlargement and increases in GFAP staining. Interestingly, apoptosis was identified by DNA ladder formation in each of the cell lines. The mRNA and protein expression of NGF, trkA and Fas increased, but expression of bcl-2 decreased. These findings suggest that PPF works as a transcriptional modulator and induces apoptosis in glioma cells.

Animals↗
PubMed1996

Assessment and comparison of algorithms for in vivo ESR-CT imaging of bioradicals with L-band microwaves.

In ESR-CT imaging, it is much more difficult to obtain satisfactory images than in imaging with other modalities, since two inverse problems, i.e. deconvolution of observed data and reconstruction from projections, must be solved. In this work, suitable algorithms for ESR-CT are examined using simulations and experiments. The algorithms were applied to actual data from a rat's head and a satisfactory reconstructed image was obtained from the viewpoint of morphological imaging. Several properties of the algorithms are discussed: (1) which combination of deconvolution and reconstruction method is favorable, (2) whether or not a raw differential signal should be integrated before deconvolution and reconstruction procedures, and (3) how SIRT, which offers good performance in ESR-CT, depends on an initial value and a noise type.

Algorithms↗
PubMed1995

Impairment of adenylyl cyclase signal transduction in mecobalamin-deficient rats.

This study examined alterations in the beta-adrenoceptor-G5-adenylyl cyclase system in cerebral cortex membranes from vitamin B12-deficient rats fed a diet lacking vitamin B12 (mecobalamin) for 15 weeks. Basal, 5(7)-guanylylimidodiphosphate (GppNHp)-, isoproterenol-, and forskolin-stimulated adenylyl cyclase activities were significantly reduced in mecobalamin-deficient rats compared with those in control rats. However, no significant differences were observed in the amount and function of G5- estimated by immunoblotting and guanine nucleotide photoaffinity labeling, respectively, or in the densities and the dissociation constants of beta-adrenoceptors, estimated by [125I] pindolol binding, between control and the deficient rats. These results indicate that vitamin B12 deficiency results in the impairment of the coupling among the beta-adrenoceptor, G5- and the catalytic subunit of adenylyl cyclase, and in dysfunction of the catalytic subunit of the enzyme, suggesting that vitamin B12 participates in the regulation of neuronal adenylyl cyclase signal transduction.

Adenylyl Cyclase Inhibitors↗
PubMed1995

Free radical imaging by electron spin resonance computed tomography in rat brain.

Images of nitroxide radicals were obtained from the brains of living rats following intracarotid injection of imaging agent, [2-(14-carboxytetradecyl)-2-ethyl-4,4-dimethyl-3-oxazolidinylox y] (16 DS) using L-band electron spin resonance computed tomography (ESR-CT). The image patterns obtained from the 3-carbamoyl-2,2,5,5-tetramethyl-1-pyrrolinyloxy injected rats showed the agent in tissues of the cranium but not within the brain. The uptake of 16 DS was found in the cortex, hippocampus, striatum, midbrain, pons medulla oblongata and cerebellum, and nuclei, mitochondria, synaptosomes of the cerebrum after intracarotid injection of 16 DS using an x-band ESR spectrometer. These results suggest that 16 DS penetrates the blood brain barrier.

Animals↗
PubMed1995

Electron paramagnetic resonance studies of ferric cytochrome c' from photosynthetic bacteria.

Electronic ground nature of ferric cytochromes c' isolated from five photosynthetic bacteria. Chromatium vinosum ATCC 17899, Rhodobacter capsulatus ATCC 11166, Rhodopseudomonas palustris ATCC 17001, Rhodospirillum molischianum ATCC 14031, and Rhodospirillum rubrum ATCC 11170 has been investigated by electron paramagnetic resonance (EPR) spectroscopy. EPR spectra indicate that the electronic ground state of five ferric cytochromes c' is a quantum mechanical admixed-spin state of a high spin (S = 5/2) and an intermediate spin (S = 3/2) at pH 7.2 and is high-spin state at pH 11.0. At physiological pH, however, the content of an intermediate spin state differs with the bacterial source of the protein: approximately 50%, Chromatium vinosum; approximately 40%, Rhodobacter capsulatus and Rhodopseudomonas palustris; approximately 10%, Rhodospirillum molischianum and Rhodospirillum rubrum. Computer simulation of the spectra supports this diversity of the contribution of an intermediate spin state. Model studies of the ferric porphyrin complexes suggest that the correlation between content of an intermediate spin state and heme iron displacement from the mean heme plane. Therefore, the variation of the content of an intermediate spin state observed in the present study reflects the subtle difference in the degree of heme iron displacement among the proteins.

Chromatium↗
PubMed1995

Detection of vanadyl-nitrogen interaction in organs of the vanadyl-treated rat: electron spin echo envelope modulation study.

ESEEM spectroscopy was applied for the first time to organs of an animal, viz. the kidney and liver of the rat treated with vanadyl sulfate. The aim of this study is to investigate the in vivo coordination structure of vanadyl ions administrated, and to gain information concerning the insulin-mimic activity of vanadium. ESEEM measurements for kidney and liver performed at 77 K have established nitrogen coordination to a certain percentage of vanadyl ion in the organs. The rotios of nitrogen-coordinating vanadyl ion were estimated as 70-80% in the liver, and 50-55% in the kidney. Isotropic portions of the 14N HFC were estimated as magnitude of Aiso approximately 5.0 MHz for liver, and approximately 5.2 MHz for kidney, indicating that the coordinating nitrogen is an amino nitrogen. Coordination of the Lys epsilon-amine or the N-terminal alpha-amine of a protein or (a peptide) to vanadyl ion in vivo is suggested.

Animals↗
PubMed1995

Two genes that encode ribosomal-protein S6 kinase homologs are induced by cold or salinity stress in Arabidopsis thaliana.

We have isolated two closely related cDNA clones (cATPK19 and cATPK6) with homology to protein-serine/threonine kinases from Arabidopsis thaliana using the polymerase chain reaction (PCR). The deduced amino acid sequences of the ATPK19 and ATPK6 contain all 11 conserved regions of the catalytic domain of protein kinases, and have homology to p70 ribosomal S6 kinases (52%). ATPK19 and ATPK6 have putative PEST regions in their N- and C-terminal regions, and these regions also contain putative phosphorylation sites that are recognized by casein kinases or proline-directed protein kinases such as cdc2, MAP kinase, and p54 MAP-2 kinase (SAPK). The transcription levels of the ATPK19 and ATPK6 genes rapidly and markedly increased when plants were subjected to cold or high-salt stresses. These observations suggest that ATPK19 and ATPK6 may function in the adaptation of plant cells to cold or high-salt conditions, providing an understanding of the role of protein phosphorylation in plant responses to environmental stresses.

Adaptation, Physiological↗
PubMed1995

Effect of cyclophosphamide on lymphokine production in MRL/lpr.Yaa mice.

The Y chromosome (Yaa gene) from autoimmune BXSB mice has been shown to be responsible for the acceleration of autoimmune symptoms when transferred to MRL/lpr mice. We examined the pathological, serological and immunological characteristics of MRL/lpr. Yaa mice and the suppressive effect of cyclophosphamide (CP) on the mice. MRL/lpr. Yaa mice spontaneously developed a massive lymphadenopathy characterized by hypergammaglobulinemia, the presence of several autoantibodies, and autoimmune disease. In MRL/lpr. Yaa mice, IL-2, IL-4 and IL-5 production in concanavalin A (Con A)-stimulated splenocytes were about 10-fold lower than in BALB/c mice at 5 weeks of age. The concentrations of these lymphokines remained low until the mice were 16 weeks of age. The production of IFN-gamma and IL-6 in 16 week old MRL/lpr. Yaa mice was about 4- and 2-fold lower, respectively, though these levels were similar in both strains at 8 weeks of age. It was found that this dysregulation of T cell function was almost identical to that in MRL/lpr mice. Administration of CP to MRL/lpr. Yaa mice ameliorated nephritis, and suppressed production of autoantibodies and the accumulation of abnormal T cells. CP also significantly elevated the production of lymphokines. These findings suggest that an abnormality of T cell function may contribute to the autoimmune pathogenesis of MRL/lpr. Yaa mice and that CP probably ameliorates auto-immune disease by improving the T cell functions.

Animals↗