Search PubMed⌕ Search

Biomedical subjects

Y Isaka

Publications and source records attributed to Y Isaka.

At least 55 records · Page 3Linked to original sources
PubMed1996

Evidence for direct association of Vpr and matrix protein p17 within the HIV-1 virion.

Vpr is one of the auxiliary proteins of HIV-1 and is selectively incorporated into the virion by a process involving the C-terminal p6 portion of the Gag precursor Pr55. Vpr and the matrix protein p17 are the components of the viral preintegration complex and appear to play important roles in the nuclear transport of proviral DNA in nondividing cells. In the present study, we have demonstrated by coimmunoprecipitation experiments that Vpr associates with matrix protein p17 but not with capsid protein p24 within the HIV-1 virion. Experiments employing the yeast two-hybrid GAL4 assay for protein-protein interactions also demonstrated a direct association between Vpr and the C-terminal region of matrix protein p17. Association of Vpr and the matrix protein p17 within the mature virion is consistent with their collaborative role in the nuclear transportation of the viral preintegration complex in nondividing cells such as macrophages.

Animals↗
PubMed1996

Inhibition of TGF-beta 1 expression by antisense oligonucleotides suppressed extracellular matrix accumulation in experimental glomerulonephritis.

Overproduction of transforming growth factor-beta 1 (TGF-beta 1) has been implicated in the pathogenesis of fibrotic diseases. TGF-beta 1 plays a crucial role in the accumulation of extracellular matrix (ECM) in human and experimental glomerular diseases. However, it remains unclear whether inhibition of TGF-beta 1 overproduction would suppress TGF-beta 1-induced ECM accumulation. To inhibit the overproduction of TGF-beta 1 in experimental glomerulonephritis induced by anti-Thy 1.1 antibody, we introduced antisense oligodeoxynucleotides (ODN) for TGF-beta 1 into the nephritic kidney by the HVJ-liposome-mediated gene transfer method. Sense, scrambled or reverse ODN were also introduced as controls. Transfected ODN accumulated mainly in the nuclei of mesangial cells in the glomeruli of transfected kidneys. In the antisense ODN-transfected rats, a marked decrease in expression of TGF-beta 1 mRNA was confirmed by Northern analysis. Consequently, the expression of TGF-beta 1 protein in the glomerulus was markedly reduced in the antisense ODN-transfected kidney with a comparable effect in preventing glomerular ECM expansion in experimental glomerulonephritis. In contrast, sense, scrambled and reverse ODNs failed to suppress TGF-beta 1 expression and ECM accumulation. Thus, these results suggested that inhibition of TGF-beta 1 overproduction could suppress progression to glomerulosclerosis.

Animals↗
PubMed1996

Gene therapy by skeletal muscle expression of decorin prevents fibrotic disease in rat kidney.

There are currently no effective therapies for progressive fibrotic diseases. Recent evidence has implicated overproduction of transforming growth factor-beta1 (TGF-beta1) as a major cause of tissue fibrosis. Furthermore, this evidence implies that inhibitors of TGF-beta1 may be clinically useful as antifibrotic agents. The proteoglycan decorin is a known inhibitor of TGF-beta1. In a rat model of glomerulonephritis we have shown that fibrosis is mediated by TGF-beta1. We report here that transfer of decorin cDNA into rat skeletal muscle increases the amount of decorin messenger RNA and protein present in skeletal muscle and decorin present in kidney, where it has a marked therapeutic effect on fibrosis induced by glomerulonephritis. Transfected glomerulonephritic rats showed a significant reduction in levels of glomerular TGF-beta1 mRNA and TGF-beta1 protein, extracellular matrix accumulation and proteinuria. These results demonstrate the potential of gene therapy as a novel treatment for fibrotic diseases caused by TGF-beta1.

Animals↗
PubMed1996

[Quantitative measurements of cerebral blood flow using 99mTc-ECD radionuclide angiography, SPECT and one-point arterial sampling].

We quantified regional cerebral blood flow using 99mTc-bicisate ethyl cysteinate dimer (ECD) radionuclide (RN) angiography, one-point arterial sampling and static SPECT in 12 patients. The tracer was injected as a bolus into the right antecubital vein, and time-activity curves over the cerebrum and the aortic arch were sequentially recorded for 300 s with 3 s intervals in a 128 x 128 format with a large-field of view gamma camera equipped with a low-energy collimator. Blood was obtained from the femoral artery immediately after stopping the RN angiography and the arterial concentration of 99mTc-ECD was calculated. Thereafter, the SPECT data acquisition was started with the subject's head immobilized. We applied a three-compartment kinetic model: The influx constant of 99mTc-ECD from blood to brain (K1) and the transfer of ECD from diffusible compartment to nondiffusible one in the blood (k5). The K1 value was compared with the global cerebral blood flow value (Fa) measured by the 133Xe clearance technique. From the kinetic analysis, the following parameter values could be calculated: K1 = 0.21 +/- 0.05 (ml/ml/min), k5 = 0.66 +/- 0.15 (/min), Fa = 0.32 +/- 0.09 (ml/ml/min) and the extraction fraction E = K1/Fa = 0.65 +/- 0.05. There was a strong correlation between K1 and Fa (Y = 0.53X + 3.7; rs = 0.91). By combining the K1 and E values in the whole-brain, we can obtain the absolute global flow value and regional 99mTc-ECD CBF maps if the average concentration of the tracer in the whole-brain is used as a reference. Our method is less invasive and suitable for quantitation of cerebral blood flow in patients with brain disorders.

Aged↗
PubMed1996

Molecular biological intervention.

Molecular biological intervention including gene therapy is a novel form of molecular medicine that will have an impact on the treatment of many serious diseases. Recent advancement in understanding of molecular mechanism of human disease and development of gene technology allows us practical approaches to molecular biological intervention. In addition to the possibility of correcting inherited genetic disorders, molecular biological intervention is being used to combat acquired disease. In the field of nephrology, the basic study has started on the gene transfer into the kidney in vivo. This review describes some approaches and methods that may be used for molecular biological intervention for glomerulonephritis and the state of our preclinical studies targeting transforming growth factor-beta.

Animals↗
PubMed1995

In vivo transfection of genes for renin and angiotensinogen into the glomerular cells induced phenotypic change of the mesangial cells and glomerular sclerosis.

Locally activated renin angiotensin system plays an important role in the progression of the glomerular diseases. In order to understand the local effect of overexpressed angiotensin II in the glomerulus in situ, we introduced human genes for renin and angiotensinogen into the rat kidney by hemagglutinating virus of Japan-liposome procedure. Three days after transfection human renin was detected in the glomeruli by immunohistochemistry. Seven days after transfection, extracellular matrix was expanded in the glomeruli and alpha-smooth muscle actin was expressed in the mesangial cells. These results suggest that locally activated renin angiotensin system induces glomerular sclerosis and a phenotypic change in mesangial cells.

Actins↗
PubMed1995

Targeting of chrolamphenicol acetyltransferase to human immunodeficiency virus particles via Vpr and Vpx.

Vpr and Vpx are the auxiliary proteins of human immunodeficiency viruses (HIVs) selectively incorporated into mature viral particles. We showed that the bacterial chloramphenicol acetyltransferase (CAT) fused to the N-terminus of HIV-1 Vpr, HIV-2 Vpr, or HIV-2 Vpx was incorporated into mature virions in a type-selective manner. By using chimeric proteins between HIV-1 Vpr and HIV-2 Vpx, we found that the N-terminal side of these proteins was mainly important for type-selective virion incorporation. The C-terminal arginine-rich region of HIV-1 Vpr was also found to transport CAT fusion proteins into virions but without any type selectivity. Furthermore, the corresponding regions of HIV-2 Vpr and HIV-2 Vpx had no such activity. This region of HIV-1 Vpr may interact nonspecifically with viral genomic RNA. Collectively, Vpr and Vpx may provide a means to introduce foreign proteins and other molecules into HIV virions for therapeutic purposes.

Amino Acid Sequence↗
PubMed1995

Functional and anatomic evaluation of carotid atherothrombosis. A combined study of indium 111 platelet scintigraphy and B-mode ultrasonography.

We examined the relation between in vivo thrombogenicity and the morphology of carotid lesions to clarify the role of platelet deposition in carotid atherothrombosis. We evaluated 60 subjects (120 carotid bifurcations) who had at least one established risk factor for atherosclerosis by using indium 111 platelet scintigraphy and high-resolution B-mode ultrasonography. We evaluated platelet accumulation in the carotid arterial wall by means of a dual-tracer method that used In 111-labeled platelets and technetium 99m-labeled human serum albumin. The tracer accumulation was assessed both visually and semiquantitatively by using the platelet accumulation index, ie, the ratio of radioactivity of the amount of In 111-labeled platelets deposited on the vascular wall to the amount of radioactivity in labeled platelets circulating in the blood pool. The morphology of the carotid lesions was analyzed with B-mode ultrasonography in terms of the presence of ulceration, the maximum percent stenosis, the echogenicity of plaque, and the plaque score, which indicates the severity of systemic atherosclerosis. Platelet accumulation increased with increase in plaque score (P < .01), and the magnitude of platelet accumulation was significantly greater in lesions with ulceration than in those without (P < .05). The platelet accumulation index in vessels with plaque showed a very weak but significant correlation with maximum percent stenosis (r = .28, P < .05) and a stronger correlation with the unilateral plaque score (r = .42, P < .0001). Analysis of the echogenicity of plaque showed that heterogeneous plaque had a high frequency of accumulating platelets. Platelet accumulation was related to the surface characteristics and severity of carotid lesions, especially in the presence of ulceration.

Arteriosclerosis↗
PubMed1995

[Intrasubject comparison of regional cerebral blood flow between N-isopropyl-p-[123I]iodoamphetamine SPECT and 99mTc-hexamethylpropyleneamine oxime SPECT in patients with ischemic cerebrovascular disease].

We compared regional cerebral blood flow (CBF) of CBF-SPECT brain imaging in two brain perfusion agents, N-isopropyl-p-[123I]iodoamphetamine (123I-IMP) and 99mTc-hexamethylpropyleneamineoxime (99mTc-HMPAO), in the same patients with ischemic cerebrovascular disease. In eight healthy volunteers and 16 patients with chronic stage of cerebral infarction, single photon emission computed tomography (SPECT) data was normalized to the count density of the tracer in the whole brain, and then converted to the absolute units of CBF by multiplying average 133Xe-CBF in the whole-brain. One-way analysis of variance (ANOVA), grouped by the affected and contra lateral hemispheres of patients and right and left hemispheres of normal volunteers, was used to assess the changes in pattern of regional CBF (rCBF) among disease and control groups. Regional CBF was significantly reduced in patients compared with normal controls in all the brain regions on both tracers: F = 6.6-14 and p = 9.1 x 10(-4) - 1.6 x 10(-6) in IMP, and F = 5.8-14.8 and p = 2 x 10(-3) - 8.2 x 10(-7) in HMPAO. F value was higher in IMP than that of HMPAO in five of nine brain regions of interests (the frontal, temporal and occipital cortices, thalamus and the striatum), whereas F value was higher in HMPAO than IMP in the other four regions (the central lobule, parietal cortex, hippocampus and the centrum semiovale).(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1994

Quantitation of rCBF by 99mTc-hexamethylpropyleneamine oxime single photon emission computed tomography combined with 133Xe CBF.

A simple, noninvasive method of measuring CBF that uses single photon emission computed tomography (SPECT) of 99mTc-hexamethylpropyleneamine oxime (99mTc-HMPAO) and whole-brain CBF obtained by 133Xe clearance technique was developed. SPECT data were normalized to the count density of HMPAO uptake in the whole brain and then converted to the absolute units of CBF by multiplying average CBF in the whole brain obtained by 133Xe. Mean CBF values in healthy volunteers (n = 12) were 49 +/- 7 and 30 +/- 5 ml 100 g-1 min-1 for gray matter and white matter, respectively, with a global flow value of 45 +/- 5 ml 100 g-1 min-1. The mean flow value was 19 +/- 7 ml 100 g-1 min-1 for the core of the infarct and 31 +/- 5 ml 100 g-1 min-1 for the contralateral region (n = 13). CBF values were reproducible for all brain regions. The method was convenient to use and suitable for the routine measurement of regional CBF in normal and pathologic states.

Cerebrovascular Circulation↗
PubMed1994

Decreased cerebrovascular dilatory capacity in subjects with asymptomatic periventricular hyperintensities.

BACKGROUND AND PURPOSE: The clinical significance of the periventricular hyperintensity incidentally found on magnetic resonance images of the brain is questionable. We evaluated resting cerebral blood flow and cerebrovascular dilatory capacity of subjects with asymptomatic periventricular hyperintensities to study their cerebral hemodynamics. METHODS: Magnetic resonance imaging of the brain was performed in 28 asymptomatic subjects with cerebrovascular risk factors to determine the severity of periventricular hyperintensity. Mean gray matter flow was computed by a 133Xe-clearance technique in subjects at rest and after the administration of 1 g acetazolamide. Flow values were correlated with the scores for periventricular hyperintensity. RESULTS: Resting gray matter flow was not significantly correlated with the severity of periventricular hyperintensity for the whole brain (rs = -.364), whereas flow after acetazolamide loading (rs = -.783, P < .001) and the absolute value of increased flow (rs = -.567, P < .01) were significantly and negatively correlated with the severity of periventricular hyperintensity. CONCLUSIONS: A decrease in vasodilatory capacity and compensatory vasodilation occur in the cerebral cortex of subjects with asymptomatic periventricular lesions and maintain cerebral blood flow.

Aged↗
PubMed1994

[Quantitation of regional cerebral blood flow by single photon emission computed tomography of CBF-tracer combined with whole-brain CBF: a comparison between 123I-IMP and 99mTc-HMPAO in healthy volunteers].

A simple, noninvasive method of measuring cerebral blood flow (CBF) that uses single-photon emission computed tomography (SPECT) of CBF-tracer and whole brain CBF obtained by xenon-133 (133Xe) clearance technique was developed. In nine healthy volunteers, SPECT data were normalized to the count density of 123I-IMP or 99mTc-HMPAO uptake in the whole-brain, and then converted to the absolute units of CBF by multiplying average 133Xe-CBF in the whole brain. The CBF values measured by 99mTc-HMPAO CBF-SPECT was significantly lower in the high flow regions of cortical gray matter (bilateral frontal lobe; p < 0.05 and right occipital lobe; p < 0.05), and was significantly higher in the bilateral white matter (p < 0.05 or 0.01) and the cerebellum (p < 0.005) compared with the flow values measured by 123I-IMP CBF-SPECT. Whereas, the IMP-CBF values were significantly lower in the bilateral striatum (p < 0.02 or 0.05) compared with the HMPAO-CBF values. Good correlations were found between IMP-CBF and the HMPAO-CBF values in the cortical gray matter (rs = 0.761; p < 0.001, n = 108), the white matter (rs = 0.739; p < 0.001, n = 18) and the cerebellum (rs = 0.731; p < 0.001, n = 18). In the striatum (rs = 0.58; p < 0.05, n = 18) and the thalamus (rs = 0.628; p < 0.05, n = 18), the correlations between IMP-CBF and HMPAO-CBF values were inferior to those of the other three regions.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

Isolation of mitochondrial cyclophilin from bovine heart.

Peptidyl-Prolyl cis-trans isomerase was isolated from bovine heart mitochondrial matrix. The enzyme has a M(r) of 19,000 and its activity was inhibited by cyclosporin A (inhibition constant, 6.9 nM), but not by FK-506. The mitochondrial content of the enzyme is in good agreement with the number of binding sites for cyclosporin A (85 pmol/mg of matrix protein). Partial amino acid sequencing showed that the enzyme has a serine-rich N-terminal extension and is similar to human cyclophilin 3 (Bergsma et al. (1991) J. Biol. Chem. 266, 23204-23214) rather than the cytosolic and endoplasmic reticulum isoforms. We conclude that this protein is mitochondrial cyclophilin and a homologue of human cyclophilin 3.

Amino Acid Isomerases↗
PubMed1993

Factors causing prolonged hypoperfusion after transient ischemic attack.

Even during the symptom-free stages, patients with a TIA often experience cerebral blood flow disturbances. In order to evaluate the factors which cause this abnormality, we studied the cerebral blood flow disturbance, anatomy and clinical status in 21 patients after TIAs. The results of 99mTc-hexamethyl-propylene-amine oxime SPECT were compared with CT, cerebral angiogram, cerebrovascular risk factors and clinical findings to determine which factor is most responsible for the hypoperfusion of brain after TIA. The overall sensitivity rates in detecting a lesion were 67% in SPECT and 19% in CT. The hypoperfused area tended to be large in patients who had intracranial, severe stenotic, multiple, or hemodynamically significant arterial lesions on the ipsilateral side. No such relationships were found between other examinations. We conclude that hypoperfusion after TIA essentially reflects a continuous cerebral blood flow disturbance that can be attributed to atherosclerosis of the cerebral arteries, with subsequent embolic and/or hemodynamic cerebral ischemia, although there may be a variety of processes.

Adult↗
PubMed1993

Glomerulosclerosis induced by in vivo transfection of transforming growth factor-beta or platelet-derived growth factor gene into the rat kidney.

Glomerulosclerosis, a final common lesion of various glomerular diseases, is characterized by mesangial cell proliferation and extracellular matrix (ECM) expansion. TGF-beta and PDGF are known to play a critical role in the regulation of ECM metabolism and mesenchymal cell proliferation, respectively. However, there is little evidence to demonstrate the direct role of each of these growth factors in the pathogenesis of glomerulosclerosis. Using an in vivo transfection technique, we could realize the selective overexpression of single growth factor in the kidney. The introduction of either TGF-beta or PDGF-B gene alone into the kidney induced glomerulosclerosis, although the patterns of action of these growth factors were different; TGF-beta affected ECM accumulation rather than cell proliferation and PDGF affected the latter rather than the former.

Animals↗
PubMed1993

Complete recanalization of total occlusion in abdominal aorta by intra-aortic infusion of a thrombolytic agent--a case report.

Complete recanalization was achieved by intra-aortic infusion of urokinase in a case of complete occlusion of the abdominal aorta. The patient was a fifty-nine-year-old man with atrial fibrillation, hypertension, and diabetes mellitus who was admitted because of intermittent claudication and pain in both lower extremities at rest. Angiography demonstrated complete obstruction of the abdominal aorta, but the bilateral iliac arteries were visualized via collaterals. Urokinase was administered intra-aortically in a total dose of 1,200,000 U during the first day and a total dose of 960,000 U during the second day. The aorta and the iliac arteries recanalized after this treatment, and complete recanalization associated with disappearance of subjective symptoms was observed after one month of treatment with warfarin. The present case suggests the usefulness of intra-arterial infusion of urokinase for the treatment of complete occlusion of the abdominal aorta.

Aorta, Abdominal↗