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Biomedical subjects

K Kitagawa

Publications and source records attributed to K Kitagawa.

At least 109 records · Page 6Linked to original sources
PubMed1998

[Angiographic diagnosis and management of bleeding from the digestive organs].

Gastrointestinal bleeding is recently seen less often by the angiographer. This is mainly due to advances in endoscopy, and nuclear medicine. When patients with gastrointestinal bleeding are referred, endoscopic diagnosis and therapy should be performed at first. However, when it is impossible to diagnose or to control the bleeding, angiography must be considered as soon as possible. Intra-abdominal bleeding should be diagnosed by angiography at first. In both cases, embolization is generally safe and effective depending on the advance of occlusive agents.

Angiography↗
PubMed1997

Expression of zinc transporter gene, ZnT-1, is induced after transient forebrain ischemia in the gerbil.

To elucidate the molecular mechanisms underlying neuronal death after transient forebrain ischemia, we cloned genes expressed after transient forebrain ischemia in the Mongolian gerbil by a differential display method. A gerbil homolog of rat zinc transporter, ZnT-1, which transports intracellular Zn2+ out of cells, was isolated. Its expression became detectable exclusively in pyramidal neurons of the CA1 region 12 hr after ischemia and reached a maximum from day 1 to day 2 as shown by in situ hybridization. By day 7, expression had disappeared entirely from the cells in the CA1 region, because the neurons had died. No other brain regions exhibited such a significant level of ZnT-1 mRNA expression during this period. Zn2+ was shown to accumulate in CA1 pyramidal neurons expressing ZnT-1 mRNA after the ischemia by using zinquin, a zinc-specific fluorescent dye. When primary hippocampal neurons were exposed to a high dose of Zn2+, ZnT-1 mRNA accumulated. These results suggest that the induction of ZnT-1 mRNA observed in CA1 neurons was caused by an increase in the intracellular Zn2+ concentration. It was reported recently that Zn2+ chelator blocked neuronal death after ischemia and that the influx of Zn2+ might be a key mechanism underlying neuronal death. The induction of ZnT-1 mRNA in CA1 pyramidal neurons fated to die after transient ischemia is of interest to the study of postischemic events and the molecular mechanisms underlying delayed neuronal death.

Amino Acid Sequence↗
PubMed1997

Regulation of the metabolism of plasma lipoproteins by apolipoprotein A-II.

Mouse apolipoprotein (apo) A-II has three variants (type A, B, and C) among inbred strains. To clarify the role of ApoA-II in the metabolism of high density lipoproteins (HDL), we constructed a new congenic mouse strain (P1.R1-Apoa2b) with type B ApoA-II of the SAMR1 strain on the genetic background of the SAMP1 strain, and examined it together with another ApoA-II congenic strain (R1.P1-Apoa2c) containing type C ApoA-II of the SAMPI strain on the SAMR1 strain and the parental SAMP1 and SAMR1 strains. Genetic characterization of the congenic strains indicated that only small regions surrounding the ApoA-II gene of the parental strains had been transferred. The strains with Apoa2c had lower plasma concentrations of HDL and ApoA-II, and a smaller HDL particle size than strains with Apoa2b. We detected no significant differences in the mRNA levels of ApoA-II or in the in vitro translational efficiency of the ApoA-II mRNA among the four strains. These findings suggested that the differences in the post-translational modification or efficiency of secretion between the Apoa2b and Apoa2c protein regulates the ApoA-II concentration which in turn determines the concentration and size of HDL in mice.

Animal Feed↗
PubMed1997

C57BL/6 strain is most susceptible to cerebral ischemia following bilateral common carotid occlusion among seven mouse strains: selective neuronal death in the murine transient forebrain ischemia.

Rats and gerbils have been used widely to investigate the molecular mechanism of selective neuronal death following transient global ischemia. Recently, the availability of transgenic mice has enabled us to examine the involvement of specific gene products in various pathophysiological conditions. However, there has been only limited information about the experimental model of cerebral ischemia in mice, particularly in regard to selective neuronal death. We examined whether bilateral carotid occlusion produced global forebrain ischemia in seven common mouse strains including C57BL/6, ICR, BALB/c, C3H, CBA, ddY and DBA/2, based on neurological signs, histological findings and cortical microcirculatory as well as India ink perfusion patterns. The C57BL/6 strain was found to be the most susceptible among seven strains. All C57BL/6 mice died within 6 h after permanent bilateral carotid occlusion. After transient bilateral carotid occlusion for 20 min, more than 90% of C57BL/6 mice showed typical neurological signs such as torsion of the neck and rolling fits, and developed selective neuronal death in the hippocampus and caudoputamen. Hypothermia prevented the neuronal death. Visualization of brain vasculature by India ink perfusion indicated that the susceptibility of the mice after bilateral carotid occlusion depended mainly on the degree of anastomosis between carotid and basilar arteries. Our results showed the feasibility of investigating selective neuronal death in transgenic mice with simple temporary occlusion of both common carotid arteries, when those from the C57BL/6 strain or inbred transgenic mice from other strains with the C57BL/6 strain in a back-cross manner are used.

Animals↗
PubMed1997

Ischemic tolerance in hippocampal CA1 neurons studied using contralateral controls.

We induced ischemic tolerance unilaterally in gerbil hippocampus using the contralateral hippocampus as control. Ischemia for 2 min of right common carotid occlusion was reversible but sufficient to cause heat-shock protein 70 production in CA1 neurons. This pretreatment given four days prior to occlusion of both common carotids for 5 min, but not at longer preceding intervals, induced tolerance in right CA1 neurons. Neuroprotection was still evident two months after the 5 min occlusion. Adenosine triphosphate content and immunoreactive microtubule associate protein 2 in the hippocampus showed that the 5 min ischemic insult was essentially equal in both hemispheres. Repetitive pretreatments at two day intervals caused almost complete protection of CA1 neurons against subsequent 5 min ischemia, while a single pretreatment showed 80% protection. However, the increase in heat-shock protein 70 with repeated pretreatments was not significantly more than with one pretreatment. We concluded that true ischemic tolerance was induced by ischemic stress itself, was long-lasting, was not due to mitigation of subsequent ischemia, and was augmented by repetition without further increase of heat-shock protein 70.

Adenosine Triphosphate↗
PubMed1997

Embodying a stable alpha-helical protein structure through efficient chemical ligation via thioether formation.

A new approach was developed to embody the alpha-helical protein structure having an arbitrary combination and arrangement of helices by the successive ligation of a haloacetyl peptide segment with a cysteinyl peptide. A four-helix-bundle protein was efficiently constructed by the repetitive ligation of alpha-helical peptide segments. The use of HPLC-purified unprotected peptide segments facilitated the purification of the intermediates to afford the highly homogeneous desired protein. The use of the bromoacetyl moiety and the chloroacetyl moiety for the ligation was judged to make no difference in practice. A trial of introducing an additional intramolecular disulfide cross-link was also examined. The resulting protein showed high stability in the chaotropic and thermal denaturation and in enzymatic degradation.

Amino Acid Sequence↗
PubMed1997

Economy during a simulated laboratory test triathlon is highly related to Olympic distance triathlon.

This study examined the relationship between Olympic distance triathlon (swim over 1.5 km, cycle over 40.0 km, and run over 10.0 km) and economy during a simulated laboratory test triathlon. Seventeen male triathletes conducted both maximal exercise tests and simulated laboratory triathlon. The latter test consisted of swimming (S), cycling (C) and running (R) stages as a continuous task using a flume-pool, a cycle ergometer and a treadmill, respectively. The exercise intensity and duration were 60% of VO2max during swimming, cycling and running for 30, 75 and 45 min, respectively. The index of economy was determined by the % VO2max at the last min of each stage during a simulated laboratory test triathlon. Results indicated that Olympic distance triathlon (total time) was correlated to swimming-VO2max (r = -0.621, p < 0.001), cycling-VO2max (r = -0.873, p < 0.001), running-VO2max (r = -0.891, p < 0.001), S-Economy (r = 0.208, ns), C-Economy (r = 0.601, p < 0.001) and R-Economy (r = 0.769, p < 0.001). There were also significant correlations between swimming time and swimming-VO2max (r = -0.648, p < 0.01), between cycling time and cycling-VO2max (r = -0.819, p <0.001), between running time and running-VO2max (r = -0.726, p < 0.001), between swimming time and S-Economy (r = 0.550, p < 0.05), between cycling time and C-Economy (r = 0.613, p < 0.01), and between running time and R-Economy (r = 0.548, p < 0.05). These results demonstrated that the larger VO2max during maximal exercise tests and smaller increment of VO2 during a simulated laboratory test triathlon indicating good economy were good predictors to determine the Olympic distance triathlon.

Adult↗
PubMed1997

Mutation induction by high-density, 50-Hz magnetic fields in human MeWo cells exposed in the DNA synthesis phase.

Exposure of cultured human MeWo cells to high-density (400 mT at 50 Hz) extremely low frequency magnetic fields (ELF-MF) induced mutations in the hypoxanthine-guanine phosphoribosyl transferase gene. Mutation induced by the ELF-MF increased during the DNA-synthesis phase in synchronously growing cells. DNA replication errors and/or disturbance of the mismatch repair systems caused by exposure to ELF-MF may be involved in the mutagenic effect.

DNA↗
PubMed1997

Increased radiosensitivity of p16 gene-deleted human glioma cells after transfection with wild-type p16 gene.

The A1235 and T98 cell lines derived from human gliomas have homozygous deletions in their p16 genes and are radiosensitive and radioresistant, respectively, with respect to other established glioma cell lines. These differences in radiosensitivity may be due to variations to some extent among cell lines, rather than genetically defined resistance or sensitivity. We examined the effect on radiation sensitivity of introducing a wild-type p16 gene into both p16-deficient glioma cell lines. The plasmid pOPMTS containing human wild-type p16 cDNA and a neomycin resistance gene, or the control plasmid pOPRSV1, were transfected into these cells. Clones from both cell lines, which expressed wild-type p16 mRNA constitutively after transfection with pOPMTS, were more radiosensitive than the parental cells and clones obtained after transfection with the negative control plasmid.

Carrier Proteins↗
PubMed1997

Synthesis and antinociceptive activity of [D-Ala2]Leu-enkephalin derivatives conjugated with the adamantane moiety.

Based on the physicochemical and pharmacological properties of drugs having an adamantane skeleton, an adamantane-based moiety was evaluated as a drug carrier for poorly absorbed compounds, including peptides, active towards the central nervous system (CNS). Seven [D-Ala2]Leu-enkephalin derivatives conjugated with an adamantane-based moiety at the C-terminus or N-terminus were prepared by the solution-phase method and their biological activities were examined. The compounds derivatized at the C-terminus through an ester or amide linkage were much more lipophilic than the parent peptide and exhibited moderate in vitro opioid activity (guinea-pig ileum assay). Among them, four derivatives (1, 2, 4, 5), exhibited significant antinociceptive effects in an in vivo assay (mouse tail-pressure test) after subcutaneous administration. This result suggests that the introduction of the lipophilic adamantane moiety into [D-Ala2]Leu-enkephalin would improve the permeation of the poorly absorbed parent peptide through the blood-brain-barrier (BBB) without loss of antinociceptive effect.

Adamantane↗
PubMed1997

Ischemic damage and subsequent proliferation of oligodendrocytes in focal cerebral ischemia.

In order to achieve a better understanding of the pathophysiology of ischemic white matter lesions, oligodendrocytic degeneration and subsequent proliferation were examined in the mouse model of middle cerebral artery occlusion. In situ hybridization histochemistry for proteolipid protein messenger RNA was employed as a sensitive and specific marker of oligodendrocytes, and immunohistochemistry for myelin basic protein was used as a compact myelin marker. Immunohistochemistry for microtubule-associated protein 2 and albumin was employed to monitor neuronal degeneration and the breakdown of the blood brain barrier, respectively. In the ischemic core of the caudoputamen, the immunoreactivity for microtubule-associated protein 2 disappeared and massive albumin extravasation occurred several hours after vessel occlusion, while proteolipid protein messenger RNA signals remained relatively strong at this time. The messenger RNA signals began to attenuate 12 h after ischemia and were hardly detectable 24 h after ischemia in the whole ischemic lesion. In situ end-labeling of fragmented DNA showed some cells with proteolipid protein messenger RNAs to have DNA fragmentation at this period. In contrast to proteolipid protein messenger RNA signals, the immunoreactivity for myelin basic protein was detected as long as five days after ischemia. An apparent increase in the cells possessing strong proteolipid protein messenger RNA signals was found five days after ischemia, mainly in the corpus callosum and the cortex bordering the infarcted areas. A double simultaneous procedure with in situ hybridization for proteolipid protein messenger RNA and immunohistochemistry for glial fibrillary acid protein or lectin histochemistry for macrophages/microglia showed proliferating oligodendrocytes to be co-localized with reactive astrocytes and macrophages/microglia. These findings show that oligodendrocytic damage occurred following ischemic neuronal damage and the breakdown of the blood brain barrier, but preceded the breakdown of myelin proteins in the ischemic lesion, that an apoptosis-like process was involved in ischemic oligodendrocytic death, and that surviving oligodendrocytes responded and proliferated in the outer border of the infarcted area.

Animals↗
PubMed1996

Effect of systemic zinc administration on delayed neuronal death in the gerbil hippocampus.

The divalent cation zinc has been reported to possess several physiological properties such as blocking apoptotic cell death through an inhibitory effect on Ca(2+)-Mg2+ endonuclease activity, or modulating the neurotoxicity via glutamate receptor subtypes. In the present study, we investigated the effect of peripherally injected zinc on delayed neuronal death seen in the hippocampus after transient global ischemia, in order to elucidate a possible beneficial role on zinc in ischemic neuronal cell death. Forty-five adult Mongolian gerbils of both sexes underwent transient bilateral clipping of the common carotid arteries for 3 min. In the pretreated animals, ZnCl2 (20 mg/kg) was injected subcutaneously once, 1 h before ischemia (superacute group; n = 6) or twice at 24 and 48 h before ischemia (subacute group; n = 14). Histological survey was carried out 3 days later by in situ DNA fragmentation method and 4 days later by hematoxylin-eosin staining by semiquantatively counting dead neurons in the CA1 sector. Subacute zinc pre-administration significantly reduced the nuclear damage and subsequent neuronal death; however, superacutely pre-administered zinc did not protect hippocampal neurons against ischemia but it did not aggravate the effect of ischemia, either. The present study suggested that transfer of exogenous zinc into the intracellular space is required for neuroprotection, presumably via the anti-endonuclease activity.

Animals↗
PubMed1996

Induction of cyclooxygenase-2 mRNA in gerbil hippocampal neurons after transient forebrain ischemia.

We examined the effect of brain ischemia on neuronal expression of cyclooxygenase-2 gene in the hippocampus. Transient forebrain ischemia was produced by occluding bilateral carotid arteries for 5 min in Mongolian gerbil. Northern blotting and in situ hybridization demonstrated that expression of cyclooxygenase-2 mRNA was transiently induced in the hippocampal neurons. Although future studies will be needed to clarify if induced cyclooxygenase-2 following ischemia is involved in neuronal damage or neuronal protection, selective cyclooxygenase-2 inhibitors may be a new therapeutical approach for the treatment of stroke.

Animals↗
PubMed1996

Tissue-specific molecular heterogeneity of human growth hormone-releasing hormone receptor protein.

A site-directed anti-peptide antibody (anti-hGHRHRc18) was generated against the cytoplasmic tail of human GHRH receptor. The dissociation constant (Kd) and the antibody binding site (AbT) of anti-hGHRHRc18 were 2.5 nmol/l and 0.54 nmol/l, respectively. In an immunoblotting experiment, affinity-purified anti-hGHRHRc18 specifically recognized a single 50-kDa protein in human pituitary. In a screening of the expression of GHRH receptor protein in extra-pituitary tissues, only human kidney showed a single 52-kDa protein. Our results suggest that the GHRH receptor protein exhibits tissue-specific molecular heterogeneity.

Amino Acid Sequence↗
PubMed1996

Immunohistochemical presence of 5 alpha-reductase rat type 1-containing cells in the rat brain.

We showed immunohistochemically the localization of 5 alpha-reductase-containing cells in the rat brain, using a rabbit antibody generated against 5 alpha-reductase rat type 1. The antibody was produced by injecting the synthetic peptide corresponding to the amino acids 38-53 of 5 alpha-reductase rat type 1, conjugated to keyhole limpet hemocyanin with 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride. Western blot analysis revealed that this antiserum recognized the protein with a molecular weight of 29,000 Da. The immunoreactive cells were distributed throughout the brain and they were preferentially located in the white matter rather than in the grey matter. These cells were mostly small and round and had a few fine processes. The immunoreaction was confined to the cytoplasm and processes. These findings indicate that 5 alpha-reductase rat type 1-containing cells are widely distributed in the rat brain and are located preferentially in the white matter rather than in the grey matter.

Animals↗
PubMed1996

Purification and properties of D-aspartate oxidase from Cryptococcus humicolus UJ1.

D-Aspartate oxidase (EC 1.4.3.1), which is highly specific to D-aspartate, was inducibly produced by a yeast strain which was isolated from soil and identified as Cryptococcus humicolus UJ1. The enzyme was purified to homogeneity as indicated on SDS-polyacrylamide gel electrophoresis. The molecular mass of the monomer subunit was determined to be 40 kDa. The native enzyme was suggested to be a homotetramer by its behavior on gel filtration. The enzyme was shown to be a flavoprotein by its absorption spectral properties, and the flavin was found to be tightly, but not covalently, bound FAD. The purified preparation had a specific activity of 76.1 mumol/min per mg protein with D-aspartate as substrate. Optimum pH was 7.5 and optimum temperature was around 35 degrees C. D-Glutamate was a very poor substrate for the enzyme. N-Methyl-D-aspartate was better than D-glutamate as substrate but markedly poorer than D-aspartate. Malonate was the most effective competitive inhibitor of the compounds tested. The N-terminal amino-acid sequence of the enzyme showed a significant homology with those of D-aspartate oxidases from beef kidney and Octopus vulgaris and those of D-amino-acid oxidases from various sources.

Amino Acid Oxidoreductases↗