Search PubMed⌕ Search

Biomedical subjects

K Mizuno

Publications and source records attributed to K Mizuno.

At least 19 recordsLinked to original sources
PubMed1995

Primary structure of a gamma subunit of G protein, gamma 12, and its phosphorylation by protein kinase C.

We have determined the primary structure of a novel gamma subunit (gamma 12, previously designated gamma S1) of G protein purified from bovine spleen. The mature gamma 12 protein composed of 68 amino acids had acetylated serine at the N terminus and geranylgeranylated/carboxylmethylated cysteine at the C terminus. This was consistent with the C-terminal prenylation signal in the amino acid sequence, which was predicted from gamma 12 cDNA isolated from a bovine spleen cDNA library. Western blots with the specific antibody against gamma 12 showed that gamma 12 is present in all tissues examined. Among various gamma subunits (gamma 1, gamma 2, gamma 3, gamma 7, and gamma 12), gamma 12 has a unique property to be phosphorylated by protein kinase C. The phosphorylated amino acid residue was Ser1 (or Ser2). The phosphorylated beta gamma 12 associated with Go alpha more tightly than the unphosphorylated form. Exposure of Swiss 3T3 and aortic smooth muscle cells to phorbol 12-myristate 13-acetate and NaF induced phosphorylation of gamma 12. Stimulation of aortic smooth muscle cells with natural vasoactive agents such as angiotensin II and vasopressin also induced phosphorylation of gamma 12. The extent of phosphorylation of beta gamma 12 in vitro was suppressed by a complex formation with Go alpha, which was relieved by the addition of guanosine 5'-O-(3-thiotriphosphate) or aluminum fluoride. These results strongly suggest that gamma 12 is phosphorylated by protein kinase C during activation of receptor(s) and G protein(s) in living cells.

Amino Acid Sequence↗
PubMed1995

Selective regulation of Lyn tyrosine kinase by CD45 in immature B cells.

It has been well established that protein-tyrosine phosphatase CD45 is critically involved in the regulation of initial tyrosine phosphorylation and effector functions of T and B cells. However, the signaling pathway governed by CD45 is not completely understood. In B cells, it has not been unequivocally resolved as to which protein-tyrosine kinases (PTKs) associated with B cell antigen receptor are regulated by CD45 in intact cells. As a first step toward the elucidation of CD45-initiated signaling events, we have tried to identify physiological substrates for CD45 by analyzing PTK activity in CD45-deficient clones recently generated from the immature B cell line WEHI-231. The results clearly demonstrated that among PTKs examined (Lyn, Lck, and Syk), only Lyn kinase is dysregulated in the absence of CD45 such that without B cell antigen receptor ligation, Lyn is hyperphosphorylated and activated in CD45-negative clones. Thus, Lyn seems to be a selective in vivo substrate for CD45 in immature B cells.

Animals↗
PubMed1995

Phosphatidylinositol 3-kinase is involved in TRE-dependent gene expression in response to arginine vasopressin.

We identified arginine vasopressin (AVP) as a potent activator of TPA-response element (TRE)-dependent gene expression in rat 3Y1 fibroblasts. In order to examine the involvement of phosphatidylinositol 3-kinase (PI3-kinase) in TRE-mediated gene expression, we examined the effect of the overexpression of PI3-kinase mutant. The overexpression of p110 alpha, the catalytic subunit of PI3-kinase, enhances TRE-reporter expression in response to AVP. On the other hand, the overexpression of the p110-EcoS mutant, which contains the binding site for the regulatory p85 subunit but lacks the catalytic domain, results in decreased TRE reporter expression in response to AVP. These results suggest that PI3-kinase is involved in TRE-dependent gene expression in response to AVP.

Animals↗
PubMed1995

Stimulation of sky receptor tyrosine kinase by the product of growth arrest-specific gene 6.

Sky (also called Rse, Brt, and Tyro3) is a member of a subfamily of related receptor tyrosine kinases, including Axl/Ufo/Ark and c-Eyk/Mer. We obtained evidence that Gas6 (the product of growth arrest-specific gene 6) is a ligand of the Sky receptor tyrosine kinase. Gas6, but not protein S (an anticoagulant protein structurally similar to Gas6), specifically bound to the soluble form of Sky (Sky-Fc), composed of the extracellular domain of Sky fused to the Fc domain of human immunoglobulin G1. The native and recombinant Gas6, but not protein S, stimulated tyrosine phosphorylation of Sky ectopically expressed in Chinese hamster ovary cells. Stimulation of Sky in response to Gas6 was inhibited by Sky-Fc. The half-maximal concentration of Gas6 that stimulated Sky was about 1 nM. Thus, Gas6 as a ligand for Sky specifically binds to and stimulates Sky receptor tyrosine kinase.

Animals↗
PubMed1995

LIMK-1 and LIMK-2, two members of a LIM motif-containing protein kinase family.

We previously isolated human cDNA encoding LIM-kinase (LIMK), a putative protein kinase which contains two repeats of the LIM motif at the N-terminus and a protein kinase consensus sequence at the C-terminus. Using as a probe a cDNA fragment of human LIMK, we isolated from a rat brain cDNA library cDNA clones encoding two distinct protein kinases (termed LIMK-1 and LIMK-2) related to human LIMK. LIMK-1 shares with human LIMK 95% of the total 647 amino acids and is probably a rat equivalent of human LIMK. LIMK-2 has an overall sequence and a domain structure similar to that of human LIMK and rat LIMK-1, but overall identity is 50-51% at the amino acid level. Like human LIMK, the protein kinase domains of rat LIMK-1 and -2 contain a characteristic sequence DLNSHN in subdomain VIB and a highly basic insert between subdomain VII and VIII. LIMK-1 and -2 are therefore closely related but distinct members of a novel LIM-containing protein kinase subfamily. Several forms of LIMK-2 transcripts encoding proteins that are N-terminally modified and/or C-terminally truncated are generated by alternative splicing or alternative initiation. Northern blot analysis revealed the expression of LIMK-1 mRNA predominantly in the brain and the expression of LIMK-2 mRNA in various tissues in the rat. Antibody raised against LIMK-1 specifically immunoprecipitated and identified in Rat2 fibroblast cells a 72 kDa protein, which has no detectable autophosphorylating activity but is capable of phosphorylating serine and threonine residues of myelin basic protein, by in vitro kinase reaction. As the LIMK family kinases have unique structural features, they are likely to have specific functions in previously uncharacterized signaling pathways.

Alternative Splicing↗
PubMed1995

Autophosphorylation activity and association with Src family kinase of Sky receptor tyrosine kinase.

"Sky" is a putative receptor tyrosine kinase predominantly expressed in the brain. Sky, like Axl/Ufo/Ark and c-Eyk, has an extracellular domain composed of two immunoglobulin-like domains and two fibronectin type III domains. Immunoblot analysis using an antibody raised against a C-terminal peptide of Sky identified a 98-kDa Sky protein in COS cells transfected with sky cDNA (COS/sky cells). A 98-kDa protein in the immunoprecipitates with anti-Sky antibody was autophosphorylated on tyrosine, by in vitro kinase reaction. When the lysates of COS/sky cells were immunoprecipitated with anti-Sky antibody and immunoblotted with an anti-phosphotyrosine antibody, a 60-kDa phosphotyrosine-containing protein, in addition to the tyrosine-phosphorylated Sky, was detected. Using the anti-Src antibody, which is reactive to Src, Fyn and Yes, we obtained evidence for an association between the Src family tyrosine kinase and the tyrosine-phosphorylated Sky receptor. These results suggest that the Src family kinase may play an important role in signal transduction of the Sky receptor.

Amino Acid Sequence↗
PubMed1995

Effects of glycolytic metabolites on preservation of high energy phosphate level and synaptic transmission in the granule cells of guinea pig hippocampal slices.

The present study was undertaken to investigate whether neural activity of hippocampal slices can be preserved after replacing D-glucose with glycolytic intermediate metabolites such as lactate, pyruvate and citrate or with other sugars such as fructose, mannose, maltose, glucosamine, sucrose and galactose. As an index of neural activity, population spikes (PS) were recorded in the granule cell layers after electrical stimulation to the perforant path of guinea pig hippocampal slices. In addition, we determined the levels of ATP and creatine phosphate (CrP) in each slice after the replacement of D-glucose with these substrates, and correlated it with the neural activity. Substrates other than D-glucose could not maintain the PS for even 20 min although the slices perfused with medium containing lactate, pyruvate, galactose, fructose and maltose maintained similar levels of ATP and CrP as in slices incubated in the D-glucose-containing medium. These results indicate that D-glucose is essential for the preservation of synaptic activity in addition to its main role as the substrate for energy production to maintain the levels of high energy phosphates.

Adenosine Triphosphate↗
PubMed1995

Antigen receptor-initiated growth inhibition is blocked in CD45-loss variants of a mature B lymphoma, with limited effects on apoptosis.

Role of CD45 in B cell antigen receptor (BcR)-mediated signaling events in mature B cells was examined using BAL-17 and its CD45-negative clones. In the CD45-negative clones, BcR stimulation induced tyrosine phosphorylation almost identical to the parental cells, with a few exceptions of reduced phosphorylation, especially of a protein of about 60 kDa. BcR-induced calcium responses were reduced in the CD45-negative clones, but the kinetics were similar to the parent. BcR stimulation led to growth inhibition in the parental cells, but signals for growth inhibition were completely blocked in the CD45-negative clones. Interestingly, the same stimulation induced low, but significant levels of apoptosis both in the parent and in the CD45-negative clones. Thus, in mature BAL-17 cells, CD45 subtly mediate early signaling events (tyrosine phosphorylation and Ca2+ mobilization), and is absolutely required for the signaling pathway leading to growth regulation, but has limited effects on apoptosis.

Animals↗
PubMed1995

Selective transmission of hepatitis C virus in vivo and in vitro.

A human plasma containing quasi-species of hepatitis C virus (HCV) was inoculated to a chimpanzee and to human lymphocytic cell lines, HPB-Ma clone 10-2, AD HPB, and Daudi, which support replication of HCV. Among six different hypervariable region (HVR) sequences detected in the inoculum, the same two were recovered both in vivo and in vitro.

Amino Acid Sequence↗
PubMed1995

Postmenopausal bone loss in Japanese women.

OBJECTIVES: Our purpose was to detect anatomic variations in postmenopausal bone loss and to determine the risk factors most affecting bone mass in Japanese women. METHODS: One hundred sixty-six Japanese women (54 premenopausal and 112 postmenopausal), aged 40-68 years, were enrolled in the study. Bone mineral densities (BMD) of the lumbar spine (L2-4) and total body were measured by dual energy X-ray absorptiometry and the results were subjected to statistical analysis. RESULTS: Among the various sites studied, the lumbar spine (L2-4) showed the fastest bone loss after menopause. Multiple regression analysis indicated that two factors, number of years since the menopause and body mass index (BMI), affected lumbar spine (L2-4) BMD. CONCLUSION: Measurement of lumbar spine (L2-4) BMD is suitable for evaluating postmenopausal osteoporosis. The risk factors for postmenopausal bone loss were a long period after menopause and a low BMI.

Adult↗
PubMed1995

Effect of body position on the blood gases and ventilation volume of infants with chronic lung disease before and after feeding.

The effect of body position before and after tube feeding was evaluated in six extremely immature infants who were being mechanically ventilated because of chronic lung disease. Their mean birthweight and gestational age were 722.7 g (range, 540 to 994) and 24.9 weeks (range, 23.9 to 26.0), respectively. This study was performed at a mean postnatal age of 47.5 days (range, 21 to 85 days). The prone position resulted in a significant increase in arterial oxygen saturation before and after feeding, whereas the tidal volume demonstrated an increase only before feeding. Also the prone position showed a significant decrease in heart rate before and after feeding and a tendency to decrease transcutaneous carbon dioxide tension values before feeding. There were no significant differences in minute ventilation despite increased tidal volume in the prone position, most likely due to a decrement of the spontaneous respiratory rate in the prone positioning. We conclude that the prone position may offer an advantage over the supine position in the management of extremely immature infants with chronic lung disease before and after feeding.

Carbon Dioxide↗
PubMed1995

Molecular cloning and in situ localization in the brain of rat sky receptor tyrosine kinase.

We previously identified a human cDNA encoding a novel receptor tyrosine kinase, termed Sky, which is predominantly expressed in the brain and has a unique extracellular domain consisting of two immunoglobulin (Ig)-like and two fibronectin type III (FN III) motifs. In attempts to define the functional role of the Sky receptor, we cloned a rat sky cDNA, and localized the sites of expression of sky transcript in the adult rat brain by Northern blot and in situ hybridization analyses using the cloned rat cDNA as a probe. The deduced amino acid sequence of rat Sky has an overall sequence and a domain topology highly conserved with human Sky (90% overall identity and 98% identity within the tyrosine kinase domain). Northern blot analysis revealed that a single 3.8-kb sky mRNA is expressed in PC12 pheochromocytoma and Neuro-2a neuroblastoma cell lines and in various regions of the adult rat brain. In situ hybridization analysis revealed widespread but confined neuronal populations in adult rat brain that express sky transcript; prominent hybridization signals were detected in the inner granular layer of the olfactory bulb, CA-1 area of the hippocampus, granule cell layer of the cerebellum, tenia tectum and cingulate gyrus neurons, and wide regions of cortex layers II-VI. The high level of expression of sky mRNA in neurons in restricted brain regions suggests that the Sky receptor may play an important role in development, function, and maintenance of specific neuronal populations in the central nervous system.

Amino Acid Sequence↗
PubMed1995

Adjustments of cardiac function during prolonged exercise relative to lactate threshold.

Alterations in cardiac function during prolonged submaximal exercise relative to lactate threshold (LT) were evaluated on 7 normal healthy males aged 30.3 +/- 5.7 years. Systolic time intervals were analyzed through simultaneous recordings of electrocardiogram, phonocardiogram, and impedance cardiogram at a paper speed of 50 mm/s. Determination of stroke volume (SV) was based upon the method described by Kubicek et al. ANOVA followed by the Scheffe post-hoc comparison revealed that SV and myocardial contractility indices (MSER and PEP/LVET) remained relatively unchanged throughout 40-min cycling exercise, although the changes in heart rate and oxygen uptake were statistically significant. In addition, systolic blood pressure remained almost unchanged during the exercise. These results may be interpreted as evidence of the "contractility reserve", i.e., the ability of maintaining heart muscle contractility during prolonged exercise at LT intensity.

Adult↗
PubMed1995

[Ictal electroencephalographic recordings of patients with seizure].

We analyzed the ictal electroencephalographies (EEGs) in 75 seizures of 73 patients. Eighty percent of the patients were below the age of 20. The seizures consisted of 35 generalized seizures, 24 partial seizures and 16 pseudoseizures. The ictal EEG of true seizures showed changes with a spike in 23 cases, and change without spike (eg. rhythmic activity, desynchronization) in 32 cases. Four ictal records could not be evaluated due to artifacts. Because half of the patients with pseudoseizures also had epilepsy, their ictal EEG examinations were very useful. The ictal EEG examination could be performed successfully on 96% of the patients with a seizure frequency of more than six a day, 52% of them with one to five seizures a day and eleven percent of them with less than one seizure a day. Seventy-five percent of ictal EEG recordings were performed when the patient was awake. The cassette of electrodes, originally made in our department, was very useful in recording the ictal EEG of children when they were awake.

Child, Preschool↗
PubMed1995

In vivo angioscopic detection of the damaged endothelium on the atheromatous plaque: application with vital staining by methylene blue.

We attempted to detect the lesion of the damaged endothelium on the atherosclerotic plaque in vivo with dye and angioscope. The plaques were induced on the aortae of rabbits by the continuous mechanical injury with the insertion of the polyethylene tube and feeding with 2% cholesterol-added diet. We observed the some plaques could be stained with 5 x 10(-2) mol/L methylene blue by angioscope. Control aorta, without any stimulations on the aorta, could not be stained. One month after injury and cholesterol feeding the plaques were stained. In such plaques, the lack of the endothelium and the existence of the lipid-containing cell in the intima was observed. However, the plaques of the aorta 6 months after finishing these procedures could not be stained. In these plaques, the morphological characteristics known as the regression of the atheromatous plaque, ie, the regeneration of the endothelium, the thick collagen layer on the plaque and the massive calcification of the plaque were observed. The results obtained were as follows. (1) The atheromatous lesion with the damaged endothelium could be detected in vivo by our vital staining method. (2) The atheromatous plaques stained in vivo are the lesion with complication and enhanced permeability. (3) The slightly stained plaques indicate the lesions with regression and lost high permeability. (4) Our method would be able to add important information on the atheroscrelotic lesions in the clinical situations than that now we perform.

Angioscopy↗