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Biomedical subjects

H Kasai

Publications and source records attributed to H Kasai.

At least 307 records · Page 17Linked to original sources
PubMed1987

Transformation of glial cells in mouse embryonic brain cells in vitro with simian virus 40.

Embryonic (E10) mouse cerebellum and spinal cord cells were cultured and infected with simian virus 40 (SV40). In all infected dishes, rapid proliferations (a dividing time less than 18 h) of non-neuronal cells were detected. Three populations of those cells, SVa, SVb and SVc, could be passaged more than 10 times. They had flat morphologies like young astrocytes and, indeed, showed immunoreactivities to glial fibrillary acidic protein (GFAP), a marker for the astrocyte. However, they had an ability to form colonies in a soft agarose medium. The large-T antigen could be detected in nuclei of the three cell populations by a fluorescent antibody test and immunoprecipitation. No transformation of neuronal cells was detected, nevertheless there were neuronal cells still possessing dividing capacities in the culture preparation.

Animals↗
PubMed1987

Mutagenic metabolites in urine and feces of rats fed with 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline, a carcinogenic mutagen present in cooked meat.

To study the in vivo fate of 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx), a carcinogenic mutagen present in cooked meat, rats were fed MeIQx in the diet and their urine and feces were analyzed for the metabolites. The isolation procedure included specific adsorption of MeIQx derivatives to blue cotton and subsequent fractionations by thin layer chromatography on silica gel and by high pressure liquid chromatography. Attention was focused on mutagenically active metabolites. Three metabolites were isolated from the urine, and their structures were elucidated on the basis of 1H nuclear magnetic resonance, ultraviolet, and mass spectra. The first metabolite characterized was 2-amino-8-hydroxymethyl-3-methylimidazo[4,5-f]quinoxaline (Compound I), the second was 2-acetylamino-3,8-dimethylimidazo[4,5-f]quinoxaline (Compound II), and the third was 2-amino-8-methylimidazo[4,5-f]quinoxaline (Compound III). Compound I was isolated also from the feces. Compounds I-III were mutagenic to Salmonella typhimurium TA98 with metabolic activation. The mutagenic potency of Compounds I and II was as high as that of MeIQx, and that of Compound III was much lower than that of MeIQx.

Animals↗
PubMed1987

Construction of a series of ompC-ompF chimeric genes by in vivo homologous recombination in Escherichia coli and characterization of their translational products.

OmpC and OmpF are major outer membrane proteins and although they are homologous proteins, they function differently in several respects. As an approach to elucidate the submolecular structures that determine their differences, we have constructed a series of ompC-ompF chimeric genes by in vivo homologous recombination between these two genes, which are adjacent on a plasmid. The recombination sites in the chimeric genes were localized by means of restriction endonuclease analysis and nucleotide sequence determination. Most of the chimeric gene products were accumulated in the outer membrane. One of the chimeric gene products, with a fusion site in a central region between the OmpC and OmpF proteins, was normally expressed but not accumulated in the outer membrane. The trimeric structures of some of the chimeric gene products appeared to be extremely unstable in a SDS solution. From these results, domains contributing to the formation of specific structures in which the OmpC and OmpF proteins differ were identified. Bacterial cells possessing the chimeric gene products were also investigated as to their sensitivity to phages that require either OmpC or OmpF as a receptor component. With the aid of the chimeric gene products, the immunogenic determinants for three anti-OmpC monoclonal antibodies were found to be localized at different portions of the OmpC polypeptide: the N-terminal, central and C-terminal portions, respectively.

Bacterial Outer Membrane Proteins↗
PubMed1987

Presynaptic Ca-antagonist omega-conotoxin irreversibly blocks N-type Ca-channels in chick sensory neurons.

The present studies on electrophysiological and pharmacological differences of the three types of Ca-currents (N-, L- and T-types) in whole-cell clamped, cultured embryonic chick sensory neurons revealed that the majority (94%) of the Ca-currents in the nerve cells were the N-type, omega-Conotoxin (omega CTX, 5 microM), a blocker of transmitter release at the presynaptic terminals, induced a complete and irreversible blockage of Ca-currents elicited from the resting membrane potential (-60 mV) in 29 cells among 58. The Ca-currents thus irreversibly blocked by the omega CTX were determined as the N-type (neuronal), as they were insensitive to nifedipine (5 microM) or were reduced in amplitude by Bay K 8644 (5 microM). A small fraction (12%) of the total Ca-currents, which were still present after the omega CTX treatment (in the rest of 29 cells), were pure L-type (long-lasting) Ca-currents, as they were enhanced by the Bay K and were blocked by the nifedipine. omega CTX was a partial and reversible blocker of the L-type Ca-currents. Furthermore, T-type (transient) Ca-currents elicited in the hyperpolarized membrane (at -100 mV) were blocked by omega CTX in an incomplete and reversible manner. The N-type Ca-currents thus separated in the nerve cells exhibited various differences in features of the voltage-dependence and ionic selectivity from the L- and T-type Ca-currents.

Animals↗
PubMed1987

Oral administration of the renal carcinogen, potassium bromate, specifically produces 8-hydroxydeoxyguanosine in rat target organ DNA.

Following oral administration of a renal carcinogen, potassium bromate (KBrO3), to the rat, a significant increase of 8-hydroxydeoxyguanosine (8-OH-dG) in kidney DNA was observed. In the liver, a non-target tissue, the increase in 8-OH-dG was not significant. The non carcinogenic oxidants, NaCIO and NaCIO2, had no effect on 8-OH-dG formation in kidney DNA. These results suggest that formation of 8-OH-dG in tissue DNA is closely related to KBrO3 carcinogenesis.

8-Hydroxy-2'-Deoxyguanosine↗
PubMed1986

Formation of 8-hydroxyguanine residues in cellular DNA exposed to the carcinogen 4-nitroquinoline 1-oxide.

8-Hydroxyguanine (8-OH-Gua) residues were formed in DNA of Ehrlich ascites cells exposed to the carcinogen 4-nitroquinoline 1-oxide. Formation of 8-OH-Gua was confirmed by chemical treatment of calf thymus DNA with the proximate metabolite of this carcinogen, 4-hydroxyaminoquinoline 1-oxide, together with seryl-adenosine monophosphate. The ratio of the rates of formations of 8-OH-Gua and the quinoline-bound adducts was about 0.2-0.3. A conceivable mechanism of formation of 8-OH-Gua is proposed.

4-Hydroxyaminoquinoline-1-oxide↗
PubMed1986

The complete amino acid sequence of vitelline coat lysin.

The vitelline coat lysin of a top shell, Tegula pfeifferi, is a single polypeptide consisting of 118 amino acid residues and having a relative molecular mass of 13800. The complete amino acid sequence of the vitelline coat lysin was determined by the analyses of five peptides obtained by cyanogen bromide degradation and three fragments obtained by Staphylococcus aureus protease digestion of the protein. The sequence showed the presence of microheterogeneities in the vicinity of the C-terminal half of the molecule and the existence of two homologous domain structures.

Amino Acid Sequence↗
PubMed1986

Potentiation of antitumor activity of 1-phthalidyl 5-fluorouracil by acetazolamide.

The effect of acetazolamide (A.A.) on the antineoplastic activity of 1-phthalidyl 5-fluorouracil (PH-FU) against rat and mouse solid tumors was examined. A.A., an inhibitor of liver PH-FU hydrolase, had no antitumor activity but greatly enhanced the activity of PH-FU when coadministered. The potentiation was evaluated in terms of suppression of tumor growth and prolongation of the life-span of tumor-bearing animals. Studies also revealed that A.A. elevated the concentration of PH-FU in tumor tissues, where 5-fluorouracil is slowly liberated from PH-FU. The results are consistent with the hypothesis that A.A. prevents enzymic degradation of PH-FU in the liver and promotes its distribution into target organs.

Acetazolamide↗
PubMed1986

Stable isotope dilution quantification of mutagens in cooked foods by combined liquid chromatography-thermospray mass spectrometry.

A method of general applicability for the detection and quantification of mutagens in cooked foods at the ppb level is presented. A minimal sample prefractionation is employed and [Me-2H3]-labeled analogs of the compounds of interest are added for identification and quantification of mutagens by accurate measurement of chromatographic retention (K') in reverse-phase high-performance liquid chromatography (HPLC), and by measurement of the ratio of response of the protonated molecular ions of analyte and internal standard by directly coupled liquid chromatography-mass spectrometry (LC/MS). Initial application is demonstrated in the analysis of 2-amino-3-methylimidazo[4,5-f]quinoline (IQ) and 2-amino-3,4-dimethylimidazo[4,5-f]quinoline (MeIQ) in broiled salmon. Measured levels of IQ and MeIQ in broiled salmon flesh were 0.3-1.8 ppb and 0.6-2.8 ppb, respectively, and for the skin of broiled salmon 1.1-1.7 ppb and 1.5-3.1 ppb, respectively. Results on cooked beef and sardine are also reported.

Animals↗
PubMed1986

Single transient K channels in mammalian sensory neurons.

A single-channel recording of the transient outward current (A-current) was obtained from dorsal root ganglion cells in culture using patch-clamp techniques. Depolarization of the membrane patch elicited pulse like current of a uniform amplitude in an outward direction, of which the unitary conductance was 20 pS. Alteration of extracellular ionic compositions indicated that the charge carriers were K ions. A systematic study was made on the voltage-dependence of the ensemble average current; (a) the activation started at a potential around -60 mV; (b) the time course of the activation was relatively rapid; (c) the channel was completely inactivated at a potential positive to -40 mV. Two time constants (tau f = 100 ms and tau s = 4,000 ms) were detected in the decay of the current indicating that the channels had two different states of inactivation. A convulsant, 4-aminopyridine (4-AP), acted on the channel only from the intracellular side of the membrane. 4-AP (5 mM) reduced not only mean open time (by 50%) but also the single-channel conductance (by 20%). The properties of the channel were independent of Ca ions in the intracellular space.

4-Aminopyridine↗
PubMed1986

Formation of 8-hydroxyguanine moiety in cellular DNA by agents producing oxygen radicals and evidence for its repair.

8-Hydroxydeoxyguanosine (8-OH-dG) was detected in DNA isolated from HeLa cells after the cells in tissue culture had been irradiated with X-rays and from the liver of mice after the whole animals had been irradiated with gamma-rays. The amounts of 8-OH-dG in DNA after in vivo irradiation were three orders of magnitude lower than those after in vitro irradiation (0.008-0.032 8-OH-dG residue/10(5) dG/krad). The 8-OH-dG produced in liver DNA by irradiation of mice decreased with time, suggesting the presence of a repair enzyme(s) acting on 8-OH-dG in mouse liver. Treatment of Salmonella typhimurium cells with hydrogen peroxide also caused increase in the 8-OH-dG content. These results indicate that 8-OH-dG is formed in vivo in cellular DNA on treatment with various oxygen radical-producing agents and that it is repairable.

8-Hydroxy-2'-Deoxyguanosine↗
PubMed1986

Limited digestion of calmodulin with trypsin in the presence or absence of various metal ions.

The limited proteolysis of bovine brain calmodulin with trypsin in the presence or absence of various metal ions was reinvestigated in detail by HPLC. With metal ion-free calmodulin, limited proteolysis occurred at Arg 37 and Arg 106 with a cleavage ratio of 1 to 5, resulting in fragments consisting of residues 1-37, 38-148, 1-106 and 107-148. Fragments 1-37 and 107-148 accumulated under metal ion-free conditions. In the presence of calcium ions, the susceptibility of these sites to trypsin decreased and limited proteolysis occurred at Lys 77 as already reported by other workers. Fragment 78-148 accumulated, whereas fragment 1-77 was unstable under calcium-bound conditions, giving smaller peptides. Upon binding of manganese ions, calmodulin underwent a change of susceptibility to trypsin, resulting in cleavage at Lys 77, as observed for calcium-bound calmodulin. In the presence of zinc or magnesium ions, calmodulin was cleaved at the same sites as metal ion-free calmodulin under conditions where calmodulin would be expected to bind the respective ions.

Amino Acids↗
PubMed1986

Hydroxylation of guanine in nucleosides and DNA at the C-8 position by heated glucose and oxygen radical-forming agents.

Heated glucose is mutagenic to Salmonella typhimurium TA 100 in the absence of S-9 mix. For identifying unknown mutagens in heated glucose (dry solid, 200 degrees C, 20 min), reaction with isopropylideneguanosine (IPG) was followed by isolation and characterization of the mutagen-IPG adduct. Two adducts, glyoxal-IPG and 8-hydroxy-IPG, were identified in the reaction mixture by this technique. To elucidate the mechanism of this hydroxylation reaction, we investigated the abilities of various agents to hydroxylate deoxyguanosine or guanine base in DNA. Various reducing agents, metals, asbestoses, polyphenols, aminophenols, and X-ray were effective for hydroxylation, and an oxygen radical seems to be the reactive species. For sensitive detection of 8-hydroxyguanine, a monoclonal antibody for it was prepared.

8-Hydroxy-2'-Deoxyguanosine↗
PubMed1986

Analysis of mutagens from cooked foods by directly combined liquid chromatography-mass spectrometry.

Directly combined high performance liquid chromatography-mass spectrometry (LC/MS) has been studied as a method of analysis of heterocyclic aromatic mutagens in cooked foods, in the parts per billion concentration range. Identification and semiquantitative estimation of mutagens is based on accurate measurement of chromatographic retention (k') and molecular weight-selective detection of mutagens, which are protonated during passage of the chromatographic eluant into a thermospray interface of a quadrupole mass spectrometer. Standard chromatographic retention (k') values in two reversed-phase systems and data from thermospray mass spectra from nine mutagens are reported. An isolation scheme employing CH3OH extraction, acid-base partition, cellulose-trisulfo-Cu-phthalocyanine adsorption, and normal-phase HPLC was used prior to LC/MS analysis. Initial applications have been demonstrated in the analysis of 2-amino-3-methylimidazo[4,5-f]quinoline (IQ) and 2-amino-3,4-dimethylimidazo[4,5-f]quinoline (MeIQ) in broiled salmon flesh. Levels measured were estimated to be in the range 0.2 to 0.4 microgram/kg IQ and 0.4 to 0.9 microgram/kg MeIQ. The method is judged to be generally applicable with minimal sample prefractionation to detection of mutagens at the parts per billion level in cooked foods.

Animals↗
PubMed1986

Detection and identification of mutagens by the adducts formed upon reaction with guanosine derivatives.

Mutagens present in crude samples such as heated glucose can be detected or identified by means of the adducts formed upon reaction with a fluorescent guanosine derivative (FG) or isopropylideneguanosine (IPG). After the reaction of IPG with heated glucose, two adducts were isolated by high-performance liquid chromatography. One of the adducts was identified as the cyclic adduct formed between IPG and glyoxal. Mesoxaldialdehyde, which is structurally related to glyoxal, also produced a cyclic IPG-adduct and showed mutagenic activity in Salmonella typhimurium strain TA100. The other adduct isolated from the reaction mixture of IPG and heated glucose was 8-hydroxy-IPG. Various reagents which generate oxygen radicals were effective in the hydroxylation of guanosine derivatives at the C-8 position. These reagents also cause hydroxylation of guanine residues in DNA.

Chromatography, High Pressure Liquid↗
PubMed1985

X-ray crystallographic and chromatographic characterization of the crystals of Ca2+-calmodulin complexed with bee venom melittin.

Crystals of calmodulin complexed with both Ca2+ and melittin, a peptide from bee venom, have been grown from 2-methyl-2,4-pentanediol solution by using the hanging drop method of vapour diffusion. The crystals belong to space group P2(1)2(1)2(1) with a = 97.3(9) A, b = 56.5(0) A, c = 33.4(9) A and Z = 4. Analyses of the dissolved crystals by high performance liquid chromatography show that the crystals contain a 1:1 complex of calmodulin and melittin. An asymmetric unit contains one such complex and the solvent content of the crystals is 47.5% (v/v).

Animals↗