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T Iwasa

Publications and source records attributed to T Iwasa.

At least 19 recordsLinked to original sources
PubMed1997

Light-induced protein conformational changes in the photolysis of octopus rhodopsin.

Light-induced protein conformational changes in the photolysis of octopus rhodopsin were measured with a highly sensitive time-resolved transient UV absorption spectrophotometer with nanosecond time resolution. A negative band around 280 nm in the lumirhodopsin minus rhodopsin spectra suggests that alteration of the environment of some of the tryptophan residues has taken place before the formation of lumirhodopsin. A small recovery of the absorbance at 280 nm was observed in the transformation of lumirhodopsin to mesorhodopsin. Kinetic parameters suggest that major conformational changes have taken place in the transformation of mesorhodopsin to acid metarhodopsin. In this transformation, drastic changes of amplitude and a shift of a difference absorption band around 280 nm take place, which suggest that some of the tryptophan residues of rhodopsin become exposed to a hydrophilic environment.

Animals↗
PubMed1997

Identification of two palmitoyl groups in octopus rhodopsin.

We determined the structure and site of fatty acid incorporated in octopus rhodopsin using a combination of fluorescence label and enzymatic cleavage methods in conjunction with fast-atom bombardment (FAB) mass spectrometry. A single peptide containing two adjacent cysteines, Cys337 and Cys338, was successfully isolated using the fluorescence from a dye conjugated to Cys345. The FAB mass spectrometric analysis of the peptide (323Phe-340Phe) revealed that two palmitoyl groups are linked to Cys337 and Cys338 via thioester bonds in octopus rhodopsin as in bovine rhodopsin.

Amino Acid Sequence↗
PubMed1997

Consecutive maintenance of human solitary and hereditary colorectal polyps in SCID mice.

Recently, the sequential changes from adenoma to adenocarcinoma have been well studied in human colorectal carcinogenesis. To study the precise clonal changes from colorectal polyps to cancer, we have established an experimental system to maintain human colorectal polyps in severe combined immunodeficient (SCID) mice that have been improved by the selective inbreeding of C.B17-scid/scid homozygous male and female showing undetectable serum IgG and IgM (< 1 microgram/ml). Two of two solitary polyps from two nonhereditary colon polyp patients, four of five colon polyps from two Peutz-Jeghers' syndrome patients and one polypoid lesion from a familial polyposis coli (FAP) patient grew very slowly but steadily, at approximately one-tenth the rate of their malignant form, (i.e., adenocarcinoma), in the improved SCID mice and were maintained for a long period (more than 2 years), over several mouse generations. However, two polyps from FAP and Peutz-Jeghers' syndrome patients could not be transplanted further because of microinfection at the transplanted site due to incomplete sterilization of original human tumors prior to surgical operation (endoscopic polypectomy). Transplanted colon polyps had a semitransparent, soft and sticky appearance, with cells containing large amounts of mucin. Malignant transformation of human colon polyp to adenocarcinoma has not been observed during the maintenance period (about 2 years) in SCID mice. In the consecutively maintained human colon polyps, however, K-ras mutations were detected at codon 12, while these mutations were not found in their original polyps in the patients.

Adenomatous Polyposis Coli↗
PubMed1996

Simple purification and functional reconstitution of octopus photoreceptor Gq, which couples rhodopsin to phospholipase C.

In invertebrate photoreceptors, illuminated rhodopsin activates multiple G proteins, which are assumed to initiate multiple phototransduction cascades. In this paper, we focused on one of the phototransduction cascades, which utilizes rhodopsin, a Gq-like G protein, and phospholipase C (PLC). A Gq-like G protein from octopus photoreceptors was successfully purified to apparent homogeneity as an active form by simple two-step chromatography. The purified G protein had an alpha beta gamma-trimeric structure consisting of 44-kDa alpha, 37-kDa beta, and 9-kDa gamma subunits. The 44-kDa alpha subunit was assigned to the Gq class by western blot with antiserum against mammalian Gq alpha and by partial amino acid sequencing of its proteolytic fragments. Light-dependent binding of GTP gamma S was observed when the purified octopus Gq was reconstituted with octopus rhodopsin that had been integrated into phospholipid vesicles. Octopus Gq activated PLC beta 1 purified from bovine brain dose-dependently in the presence of A1F4-. Finally, light- and GTP-dependent activation of PLC beta 1 was observed in a reconstitution system consisting of octopus rhodopsin, Gq, and bovine PLC beta 1.

Aluminum Compounds↗
PubMed1996

Regioselectivity and substrate concentration-dependency of involvement of the CYP2D subfamily in oxidative metabolism of amitriptyline and nortriptyline in rat liver microsomes.

Kinetic analysis of the metabolism of amitriptyline and nortriptyline using liver microsomes from Wister rats showed that more than one enzyme was involved in each reaction except for monophasic amitriptyline N-demethylation. The Vmax values particularly in the high-affinity sites for E-10-hydroxylation of both drugs were larger than those for Z-10-hydroxylations. Their E- and E-10-hydroxylase activities in Dark-Agouti rats, which are deficient for CYP2D1, were significantly lower than those in Wistar rats at a lower substrate concentration (5 microM). The strain difference was reduced at a higher substrate concentration (500 microM). A similar but a smaller strain difference was also observed in nortriptyline N-demethylase activity, and a pronounced sex difference (male > female) was observed in N-demethylation of both drugs in Wistar and Dark-Agouti rats. The reactions with the strain difference were inhibited concentration-dependently by sparteine, a substrate of the CYP2D subfamily, and an antibody against a CYP2D isoenzyme. The profiles of these decreased metabolic activities corresponded to that of the lower metabolic activities in Dark-Agouti rats. These results indicated that a cytochrome P450 isozyme in the CYP2D subfamily was involved in E- and Z-10-hydroxylations of amitriptyline and nortriptyline in rat liver microsomes as a major isozyme in a low substrate concentration range. It seems likely that the CYP2D enzyme contributes to nortriptyline N-demethylation.

Amitriptyline↗
PubMed1994

Phylogenetic relationships among vertebrate visual pigments.

Genomic DNA fragments in exon 4 of chicken, goldfish and salmon visual pigments were amplified by polymerase chain reaction, using oligonucleotide mixtures as primers, and hypothetical phylogenetic trees were drawn up from the deduced amino acid sequences. The results suggest that vertebrate visual pigments have evolved along at least five lines, and that these lines diverged from an ancestral gene before the bony fishes diverged from the rest of the higher vertebrates.

Amino Acid Sequence↗
PubMed1994

The biological significance of glycyrrhizin- and glycyrrhetinic acid derivative-induced selective phosphorylation of histones H2A and H2B by A-kinase in vitro.

Histones H2A and H2B were found to be glycyrrhizin (GL)-binding proteins, because (i) the two histones H2A-H2B pairs were isolated selectively from the crude histone preparations of calf thymus by means of GL-affinity column chromatography (HPLC); (ii) phosphorylation of these two histones by A-kinase was remarkably stimulated by native GL or oGA (a derivative of glycyrrhetinic acid) at 20 microM; and (iii) in the crude histone preparations of calf thymus, these two histones were selectively phosphorylated by A-kinase in the presence of both dsDNA and 20 microM oGA or 20 microM GL. The provided data suggest that the GL-induced selective phosphorylation of histones H2A and H2B by A-kinase may be implicated in the transcriptional activation involved in the biological activities of the drug.

Animals↗
PubMed1993

GTP-binding protein couples with metabotropic glutamate receptor in bovine retinal on-bipolar cell.

GTP-binding protein (G protein) linking to metabotropic glutamate receptor of bovine retinal on-bipolar cell was studied by use of pharmacologically selective ligands, 2-amino-4-phosphonobutyric acid (APB) on bacterial toxin-catalyzed ADP-ribosylation and GTP gamma S-binding. In contrast to the electrophysiological findings reported, G protein coupling to APB-sensitive glutamate receptor served as a substrate for pertussis toxin but did not for cholera toxin. Several glutamate analogues effective on on-bipolar cell, as well as APB, increased GTP gamma S binding to retinal membranes devoid of rod outer segments. The enhancement of GTP gamma S binding by APB was completely abolished when the membranes were pretreated with pertussis toxin and NAD. These results suggest that, in retinal on-bipolar cell, the G protein which couples metabotropic glutamate receptor to hyperpolarizing response of the cell is sensitive to pertussis toxin.

Animals↗
PubMed1993

Infrared studies of octopus rhodopsin. Existence of a long-lived intermediate and the states of the carboxylic group of Asp-81 in rhodopsin and its photoproducts.

The infrared absorption spectra of octopus rhodopsin and its photoproducts have been observed at 282K and 210K under irradiation of blue and orange light in a neutral condition. The acid metarhodopsin-minus-rhodopsin and lumirhodopsin-minus-rhodopsin difference spectra have been obtained. A new intermediate (called transient acid metarhodopsin) with a lifetime of about 5 s has been found to exist prior to acid metarhodopsin. The present results, together with the data obtained previously, give information on the state of the carboxylic group in the side chain of Asp-81, which is the only acidic amino-acid residue in the part of opsin buried inside the membrane. This carboxylic group is protonated throughout the transformation series, but its state changes on going from transient acid metarhodopsin to acid metarhodopsin. It is probable that these two photoproducts are different from each other only in the opsin moiety.

Animals↗
PubMed1993

Primary neurilemoma of the thyroid gland: report of a case.

Neurilemoma, like other non-epithelial tumors, seldom occurs in the thyroid gland. A 57-year-old man was first referred to our hospital with an asymptomatic anterior neck tumor. A solid tumor was detected in the right lobe of the thyroid and an enucleation of the thyroid tumor was performed. The tumor was 35 x 33 x 33 mm in size, and diagnosed as Antoni A type neurilemoma. We were only able to find seven previously reported detailed cases of primary neurilemoma of the thyroid gland. A review of these cases, however, revealed that neurilemoma tends to develop in the right lobe of the thyroid gland. An operation is thus considered necessary and an enucleation of the tumor is appropriate.

Humans↗
PubMed1993

Submassive hepatic necrosis induced by dichloropropanol.

A hitherto undescribed industrial liver injury of fulminant form induced by dichloropropanol is reported. Two middle-aged men developed severe hepatic injury just after cleaning a dichloropropanol tank at a plant producing dichloropropanol. They died from hepatic failure 4 and 11 days respectively, after carrying out the work. Liver specimens taken at autopsy from one of the cases showed submassive hepatic necrosis. This accident prompted us to undertake an experimental study in rats of intraperitoneal one-shot injection of two isomeric substances of dichloropropanol, that is, 2,3-dichloro-1-propanol (DC1P) and 1,3-dichloro-2-propanol (DC2P). Saline was injected into the control rats. One, two, four, six, 24, 48, 72 h, and 1 week after the injection, rats in each group were sacrificed. Neither control nor DC1P-injected rats showed significant biochemical or histopathological abnormalities. DC2P-injected rats revealed elevations of transaminase from 6 h after the injections, and submassive necrosis of the liver was observed in many rats. It was concluded that the severe liver injuries in both the human cases and rats in our study were caused by DC2P.

Adult↗
PubMed1993

Reduction of leaky lymphocyte clones producing immunoglobulins and thymic lymphocytic leukemia by selective inbreeding of SCID (severe combined immunodeficiency) mice.

Selective inbreeding of C.B17-scid/scid mouse pairs showing undetectable IgG and IgM has been carried out in order to reduce the mortality of mice by early occurrence of thymic lymphocytic leukemia and abnormal lymphocyte clones producing immunoglobulins, both of which inhibit the successful heterotransplantation of normal and neoplastic human tissues. Although the majority of C.B17-scid/scid mice showed undetectable (< 1 microgram/ml) or low level (< or = 25 micrograms/ml) of serum IgG and IgM, some produced abnormally high concentrations of IgG and IgM (> 25 micrograms/ml). The incidence of such mice showing higher levels of IgG was very high at F1 and F2 generation (10/55, 18.2%), but significantly low after the F3 generation (18/446, 4.0%, p << 0.001). Although leukemia incidence was very high at F4 to F5 generations (8/40, 20.0%), death from leukemia was not observed early in life (4-6 months after birth) at F7 to F10 generations (0/36, 0%, p < 0.01) and was very low during the age of 6-10 months after the F8 generation (11/66, 16.7% at F4 and F5 vs 4/93, 4.3% at F8-10), p < 0.01). Scid mice improved by the selective inbreeding will provide an invaluable experimental system for the heterotransplantation of normal and neoplastic human tissues.

Animals↗
PubMed1993

[Brachial plexus block with a nerve stimulator and "around the needle" catheter technique].

Brachial plexus block using a nerve stimulator is an accurate procedure. But prolonged analgesic effect can not be obtained. Therefore we used "around the needle" catheter technique to have a long analgesic effect. A 20-gauge, 5-inch intravenous catheter (Angiocath) was threaded over a 23-gauge, 10-cm needle (Pole). We used axillary approach. The cathode of the nerve stimulator (NS-2CA, Professional Instrument company) is connected to the needle, and its anode is connected to the electrode on the surface of the skin. When the needle is introduced and advanced, 1 mA of electric current is applied for nerve stimulation. When the muscle twitch is obtained, a plastic cannula is then threaded off the needle into the axillary sheath. An infusion tube and three way stopcock is connected to the cannula. From 1988 to 1991 we had 31 cases. The success rate is about 90%. If we stimulate other nerves in the same sheath, it is not necessary to seek aimed one. But the musculocutaneous nerve is the only exception, because it may be stimulated outside the neurovascular sheath.

Brachial Plexus↗
PubMed1992

[Fulminant hepatitis after the inhalation of dichloropropanols].

A fatal case of acute fulminant hepatitis following exposure to dichloropropanols is reported. A 59-year-old male worker in a chemical plant developed general malaise, nausea and vomiting several hours after cleaning a tank that had contained dichloropropanols. He had no previous history of hepatic dysfunction. On admission, hepatomegaly was prominent. Because of highly elevated levels of GOT and GPT in the serum, reduced prothrombin time and a lowered consciousness level, a diagnosis of fulminant hepatitis was made. Significant decreases of leukocytes and platelets were also observed. Serum creatinine and BUN were slightly elevated. Although plasma exchanges were conducted on the third and fourth day, the liver functions continued to deteriorate. The patient died on the fifth day. Because dichloropropanols could be detected in the blood specimens obtained at the time of admission, we considered that fulminant hepatitis in this case was attributed to dichloropropanols exposure. To our knowledge, this is the first case of fulminant hepatitis after dichloropropanols-exposure.

Administration, Inhalation↗
PubMed1992

[Toxicity of dichloropropanols--changes in hematological findings and serum chemistry].

We investigated the toxicity of dichloropropanols (DCPs) in hematological findings and serum chemistry. The solutions of two isomers of DCPs, 1,3-dichloro-2-propanol (DC2P) and 2,3-dichloro-1-propanol (DC1P) were dissolved in saline at the concentration of 100 mg/ml, and 0.1 ml of each solution was subcutaneously injected into male Wistar rats weighing about 200 g. At 6 hours after the injections, in the DC2P group, the number of white blood cells and platelets showed a significant decrease. Transaminases, alkaline phosphatase and lactate dehydrogenase were greatly elevated. Blood urea nitrogen and creatinine also showed a significant increase. There were no changes in the measurements in the DC1P group. These results indicate that there is a prominent hepatotoxicity in DC2P, and that there is a considerable difference in the toxicity present in DC2P and DC1P. Furthermore, in the workplace where DCPs, especially DC2P, is used, the monitoring of the working environment and biological monitoring should be mandatory.

Alkaline Phosphatase↗