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Biomedical subjects

A Tojo

Publications and source records attributed to A Tojo.

At least 91 records · Page 5Linked to original sources
PubMed1996

Effects of antihypertensive drugs on nitric oxide synthase activity in rat kidney.

Nitric oxide production has been reported to be reduced in hypertensive patients. In this study, we investigated the effects of antihypertensive drugs such as calcium channel blocker, amlodipine, alpha 1-adrenoceptor blocker, doxazosin and angiotensin converting enzyme (ACE) inhibitor, imidapril on nitric oxide synthase (NOS) activity in the kidneys of L-NAME-induced hypertensive rats. An increased blood pressure in L-NAME-induced hypertensive rats was significantly decreased by these antihypertensives to the same extent at four weeks. Nitrite production from the kidney slices was significantly suppressed in L-NAME-induced hypertensive rats. This suppression of nitrite production was reversed to the control level in the rats treated with amlodipine, and significantly enhanced by doxazosin and imidapril. Immunoreactivity for both the brain-type NOS in the macula densa and endothelial cell-type NOS in renal vasculature was diminished in L-NAME rats, and antihypertensive therapies, especially doxazosin and imidapril, increased NOS immunostaining. The increased glomerulosclerosis score in the L-NAME group was significantly lowered by the treatment with doxazosin and imidapril. In conclusion, a decreased NOS activity in L-NAME-induced hypertensive rats was significantly increased by alpha 1-adrenoceptor blockers and ACE inhibitors in the kidney, and this increased NOS activity may have a role in the prevention of glomerulosclerosis.

Adrenergic alpha-Antagonists↗
PubMed1996

Hypertensive glomerular damage as revealed by the expression of alpha-smooth muscle actin and non-muscle myosin.

The aim of this study was to determine the phenotypic modulation in mesangial cells of glomeruli damaged by hypertension. Salt-loaded stroke-prone spontaneously hypertensive rats were untreated or treated with a calcium antagonist, manidipine (2 mg/kg/day) for eight weeks. In normotensive Wistar-Kyoto rats, alpha-smooth muscle actin was not expressed in any glomerular cells and a non-muscle myosin heavy chain isoform, SMemb, was slightly expressed in glomerular visceral epithelial cells. In the untreated hypertensive rats, the glomeruli showed sclerosis to various degrees and expressed alpha-smooth muscle actin and SMemb. Normal expression of SMemb in the epithelial cells disappeared. Notably, alpha-smooth muscle actin-positive fibroblast-like cells appeared in the interstitium, especially around the Bowman's capsules. Manidipine ameliorated the glomerulosclerosis and reduced the expression of alpha-smooth muscle actin in mesangial cells. In conclusion, the mesangial cells changed their phenotypes and expressed alpha-smooth muscle actin and SMemb in the glomeruli during the development of hypertensive renal damage. These phenotypically changed mesangial cells are considered to be activated and to produce various kinds of cytokines and extracellular matrix, which leads to glomerulosclerosis. Manidipine attenuated the glomerular damage and the phenotypic changes. The functional relevance of phenotypic changes in these cells should be elucidated in future studies.

Actins↗
PubMed1996

[Bronchiolitis obliterans organizing pneumonia (BOOP) after allogeneic bone marrow transplantation].

We report a patient who underwent allogeneic bone marrow transplantation for ALL. The patient presented low grade fever, cough and dyspnea at day 3 after after bone marrow transplantation. Imaging studies showed bilateral patchy infiltrates on chest X-ray and chest CT. Though treated by antibiotics, chest auscultation recognized marked bilateral inspiratory crackles. Transbronchial lung biopsy performed on day 34 showed bronchiolitis obliterans and an organizing interstitial pneumonia. The patient was treated with methylprednisolone and follow up computed tomography findings improved.

Administration, Oral↗
PubMed1995

Down-modulation of c-kit mRNA and protein expression by erythroid differentiation factor/activin A.

We examined the effects of erythroid differentiation factor (EDF)/activin A on the expression of c-kit mRNA and protein in murine erythroleukemia (MEL) cells. EDF/activin A induced MEL cells to benzidine positive cells. Northern blot analysis showed that the c-kit mRNA expression was reduced synchronously with increase of beta-globin and uroporphyrinogen decarboxylase gene expression during EDF/activin A induced erythroid differentiation. Scatchard analysis indicated that the cell surface receptor number was reduced without change of affinity during differentiation. Our results suggest that EDF/activin A may act as a natural regulator of erythropoiesis with modulation of c-kit gene expression.

Activins↗
PubMed1995

Expression of immunoreactive nitric oxide synthase isoforms in rat kidney. Effects of dietary salt and losartan.

Immunohistochemical studies have shown expression of two different isoforms of NOS in the juxtaglomerular apparatus (JGA). Antibodies to a Ca(++)-calmodulin dependent isoform purified from rat brain (B-NOS) label the macula densa cells whereas antibodies to an isoform purified from rat aortic smooth muscle cells in culture (VSM-NOS) induced with lipopolysaccharide and interferon gamma label the afferent arteriole. Since dietary salt intake and angiotensin II (Ang II) are determinants of renal NO generation, we have tested the hypothesis that salt intake can regulate the immunohistochemical expression of these NOS isoforms through an effect of Ang II. In 4 of 5 paired studies, the immunostaining for both B-NOS and VSM-NOS was more intense in rats that had received a low salt (LS), compared to a high salt (HS), diet. Infusion of the Ang II type 1 (AT1) receptor antagonist, losartan, enhanced the intensity of immunoreactive staining for both isoforms. In conclusion, the immunohistochemical expression of NOS isoforms in the JGA is increased by dietary salt restriction; this effect cannot be ascribed to Ang II acting on type 1 receptors.

Amino Acid Oxidoreductases↗
PubMed1995

[Targeted toxin therapy in the treatment of leukemia].

A chimeric toxin in which the cell surface binding domain of Pseudomonas exotoxin was replaced with mature human granulocyte colony-stimulating factor (G-CSF) was produced in Escherichia coli, partially purified and tested for its biological activity on a G-CSF-dependent murine myeloid leukemia cell line, NFS60. This fusion protein, termed as G-CSF-PE40, can displace [125I] G-CSF binding to its receptor. After 48 hrs incubation in the presence of G-CSF, G-CSF-PE40 inhibited protein synthesis and revealed cytotoxicity in NFS60 cells in a concentration dependent manner. The half maximal dose of G-CSF-PE40 for protein synthesis inhibition (ID50) in NFS60 cells was estimated at around 100pM. Additionally, relatively low concentration of G-CSF-PE40 stimulated DNA synthesis in NFS60 cells after 16 hrs' incubation in the absence of G-CSF, suggesting that G-CSF-PE40 also can transduce a transient mitogenic signal. Thus, G-CSF-PE40 may be useful in the selective elimination of myeloid cells expressing G-CSF receptors, especially in combination with chemotherapeutic agents like cytosine arabinoside.

ADP Ribose Transferases↗
PubMed1995

[Multiple myeloma developing myelodysplastic syndrome with thrombocytosis].

A 64-year-old woman with multiple myeloma, IgG lambda type Durie-Salmon Stage II, was admitted because of gradually developing anemia and increased blasts with abnormal karyotype in her bone marrow after 10 years of treatment. The chromosomal analysis showed 44, XX, del(5q), del(7q), -9, add(12p), -21, typical of secondary MDS due to the cumulative alkylating agents. Thrombocytosis concomitantly occurred with emergence of chromosomal abnormality, but the serum interleukin 6 level was not elevated, which suggested that it was related to development of secondary MDS.

Antineoplastic Agents↗
PubMed1994

Adhesion of NFS-60 myeloid leukemia cells to MC3T3-G2/PA6 stromal cells induces granulocyte colony-stimulating factor production.

To examine the interaction between immature myeloid cells and stromal cells in the induction of granulocyte colony-stimulating factor (G-CSF) production, stromal cells of the MC3T3-G2/PA6 (PA6) murine cell line, which has preadipocyte characteristics and can support hematopoiesis, were cocultured with various myeloid cell lines and G-CSF mRNA expression was examined by Northern and reverse transcriptase-polymerase chain reaction analyses. A significant amount of G-CSF mRNA was induced by the culture of an interleukin-3/G-CSF-dependent murine myeloid leukemia cell line, NFS-60, on PA6 stromal cells for 16 hours. Using a G-CSF-dependent subline of DA-1 (DA-1N), the biologic activity of G-CSF was also detected in PA6/NFS-60 coculture supernatants, but not in the culture supernatant of PA6 or NFS-60 alone. Direct contact of NFS-60 cells with the PA6 stromal layer was essential for the induction of G-CSF mRNA, as indicated by the following observations: (1) NFS-60 cells efficiently adhered to PA6 cells; (2) medium conditioned by NFS-60 cells did not contain the activity to induce G-CSF mRNA in PA6 cells; and (3) induction of G-CSF mRNA was not observed when NFS-60 cells were separated from PA6 cells by a microporous membrane (0.45-microns pore size). Several other myeloid cell lines, including FDC-P2, 32Dcl3, WEHI-3, and DA-1, did not induce G-CSF mRNA expression after the coculture with PA6 cells, although significant numbers of these cells adhered to PA6 cells. Therefore, NFS-60 cells may express or overexpress a molecule that is involved in adhesion-mediated induction of G-CSF production.

Animals↗
PubMed1994

Retrovirus-mediated gene transfer of human pyruvate kinase (PK) cDNA into murine hematopoietic cells: implications for gene therapy of human PK deficiency.

With the advent of recent molecular studies, nonspherocytic hemolytic anemia caused by red blood cell pyruvate kinase (PK) deficiency is now considered to be caused by a structural mutation of the PK-LR gene. Because PK deficiency is a monogenic disorder, the introduction of the normal PK gene into a patient's bone marrow stem cells should cure the disorder. To study the feasibility of gene therapy for PK deficiency, we first constructed the PK retrovirus pMNSM-hPK using human liver-type PK (LPK) cDNA and obtained a producer cell line of E86/AmPK. By using the supernatant of this virus-producer cell, we transduced NIH/3T3 cells, mouse leukemic cells (NFS60, FDCP-2), and human leukemic cells (K562, HEL). The expression of human LPK enzyme activity was ascertained from the retrovirally transduced NIH/3T3 cells. Northern blot analysis demonstrated the expression of the human LPK mRNA in each transduced cell line. Furthermore, bone marrow stem cells (c-kit+, Lin-, Thy-1lo) sorted by fluorescence-activated cell sorting were also transduced by the producer cells in the presence of interleukin-3 and interleukin-6, and were transplanted into lethally irradiated C57BL/6 mice. Polymerase chain reaction analysis demonstrated the expression of human LPK mRNA in both the peripheral blood and hematopoietic organs on day 30 and on day 135 of bone marrow transplantation.

Animals↗
PubMed1994

Epidermal growth factor-receptor mutant lacking the autophosphorylation sites induces phosphorylation of Shc protein and Shc-Grb2/ASH association and retains mitogenic activity.

Epidermal growth factor (EGF) receptor (EGFR) can induce cell growth and transformation in a ligand-dependent manner. To examine whether the autophosphorylation of EGFR correlates with the capacity of the activated EGFR to induce cell growth and transformation, we truncated the human EGFR just after residue 1011, removing all three major autophosphorylation sites (DEL1011). Further, a point mutation was introduced at another autophosphorylation site, Tyr-992-->Phe (DEL1011+F992). The wild-type and mutant receptors were stably expressed in a NIH 3T3 variant cell line that expresses an extremely low level of endogenous EGFR and does not grow with EGF. As expected, DEL1011 and DEL1011+F992 were found to be severely impaired in EGF-induced autophosphorylation, due to the deletion of the appropriate target tyrosines. However, mutant receptors still could induce EGF-dependent DNA synthesis, morphological transformation, and anchorage-independent growth, although the extent of these was significantly reduced when compared with wild-type EGFR. EGF-induced tyrosine phosphorylation of Ras-GTPase activating protein-associated protein p62 and phospholipase C gamma 1 was dramatically reduced in the cells expressing DEL1011 and DEL1011+F992. On the other hand, tyrosine phosphorylation of Shc, complex formation of Shc-Grb2/Ash, and activation of microtubule-associated protein kinase were still fully induced upon EGF stimulation without binding of Shc or Grb2/Ash to the mutant receptor. Thus, tyrosine phosphorylation of Shc may play a crucial role for activating Ras and generating mitotic signals by the activated EGFR mutant.

3T3 Cells↗
PubMed1994

Production of human granulocyte colony stimulating factor by various kinds of stromal cells in vitro detected by enzyme immunoassay and in situ hybridization.

Production of human granulocyte colony stimulating factor (G-CSF) by stromal cells was studied in vitro. Induction of G-CSF by interleukin 1 (IL-1) and lipopolysaccharide (LPS) was compared using enzyme immunoassay in various kinds of stromal cells. Primary human bone marrow stromal cells, a human bone marrow-derived stromal cell line (KM-102), and peripheral blood monocytes secreted small amounts of G-CSF without stimulation, while vascular endothelial cells and skin fibroblasts secreted G-CSF only when induced by IL-1 or LPS. The production of G-CSF by monocytes was stimulated predominantly by LPS, whereas that by KM-102 cells, endothelial cells, and fibroblasts was induced by IL-1 but much less so by LPS. IL-1 and LPS stimulated similar levels of G-CSF production by primary bone marrow stromal cells which consisted of various types of cells. In situ hybridization for G-CSF mRNA showed that only a small proportion of primary bone marrow stromal cells expressed a large amount of G-CSF mRNA upon stimulation. The positive cells were round or oval in shape, while most of the spindle-shaped stromal cells were negative for specific grains. Although further characterization of positive cells is needed, the results suggest that bone marrow stromal cells are heterogeneous in terms of their capacity for G-CSF production.

3T3 Cells↗
PubMed1994

Nitric oxide inhibits bafilomycin-sensitive H(+)-ATPase activity in rat cortical collecting duct.

Nitric oxide (NO) is a messenger molecule that is produced from L-arginine by NO synthase (NOS). Some NOS isoforms are present in cells constitutively, whereas others can be induced by cytokines. Recent evidence suggests that NO inhibits intracellular pH regulation by the vacuolar H(+)-adenosinetriphosphatase (ATPase) in macrophages, which contain an inducible form of NOS. The vacuolar H(+)-ATPase is involved in proton secretion in intercalated cells in the collecting duct. We have therefore examined the effect of NO on bafilomycin-sensitive H(+)-ATPase activity in individual cortical collecting ducts (CCD) microdissected from collagenase-treated kidneys of normal rats using a fluorometric microassay. Incubation of CCD with the NO donors, sodium nitroprusside (0.1 and 1 mM) or 3-morpholino-sydnonimine hydrochloride (SIN-1, 30 microM), caused a dose-dependent decrease in H(+)-ATPase activity. Incubation of CCD with lipopolysaccharide (LPS) and interferon-gamma, which induces NOS in macrophages, decreased H(+)-ATPase activity by 85%. This effect was prevented by simultaneous incubation with N omega-nitro-L-arginine, a competitive inhibitor of NOS, indicating that the decrease in H(+)-ATPase activity was caused by NO production. Incubation with 8-bromo-guanosine 3',5'-cyclic monophosphate (cGMP) also inhibited H(+)-ATPase activity, suggesting that NO may exert its effect in the CCD via activation of guanylyl cyclase and production of cGMP. Immunohistochemistry using antibodies to the macrophage-type NOS revealed strong labeling of intercalated cells in the CCD, confirming the presence of NOS in these cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Oxidoreductases↗
PubMed1994

Angiotensin II regulates H(+)-ATPase activity in rat cortical collecting duct.

Angiotensin II (ANG II) plays an important role in the regulation of solute transport in the kidney, and its effect on proximal tubule sodium and fluid transport has been studied extensively. Although there is evidence that ANG II receptors are present also in the distal nephron and collecting duct, little is known about the physiological role of ANG II in these segments of the renal tubule. Preliminary studies in our laboratory suggest that ANG II may have both structural and functional effects on intercalated cells in the cortical collecting duct (CCD). Therefore, the present study examines the effect of ANG II on H(+)-adenosinetriphosphatase (H(+)-ATPase) and H(+)-K(+)-ATPase activity in individual CCD segments microdissected from collagenase-treated rat kidneys. The H(+)-ATPase was measured as bafilomycin-sensitive ATPase activity, and H(+)-K(+)-ATPase was measured as Sch-28080-sensitive ATPase activity, by a fluorometric microassay. Preincubation of CCD segments with ANG II, 10(-10)-10(-5) M, caused a dose-dependent decrease in H(+)-ATPase activity with maximum inhibition at 10(-8) M of ANG II. The inhibitory effect of ANG II was abolished when tubules were incubated with ANG II in the presence of 10(-6) M losartan, indicating that the inhibition was mediated via specific AT1 receptors. The AT2-receptor antagonist, PD-123319, had no effect on the ANG II-mediated inhibition of H(+)-ATPase activity. Preincubation of CCD segments with 10(-10) or 10(-7) M ANG II had no effect on H(+)-K(+)-ATPase activity.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine Diphosphate↗
PubMed1994

Immunocytochemical localization of distinct isoforms of nitric oxide synthase in the juxtaglomerular apparatus of normal rat kidney.

Nitric oxide (NO) is a messenger molecule that functions as a vasodilator and accounts for the biologic activity of endothelium-derived relaxing factor (EDRF). The enzyme responsible for NO production, NO synthase (NOS), exists in different isoforms. Some are expressed constitutively in various tissues, whereas others require induction by endotoxin and cytokines. There is evidence that NO plays an important role in the regulation of basal renal vascular resistance and in the tubuloglomerular feedback response. Specific antibodies to a constitutive NOS isolated from rat brain (B-NOS) and an inducible NOS isolated from rat aortic smooth muscle (VSM-NOS) were used to establish the cellular and subcellular distribution of NOS in the kidney. Kidneys from normal rats were preserved and processed for light and electron microscopic immunohistochemical studies using both a preembedding and a postembedding horseradish peroxidase technique. By light microscopy, strong immunostaining for B-NOS was observed in the juxtaglomerular apparatus, where it was located in cells of the macula densa. In contrast, immunostaining for VSM-NOS was specifically located in the terminal afferent arteriole and occasionally also in the initial efferent arteriole in the juxtaglomerular apparatus. In addition, faint immunostaining was present in the entire distal tubule. There was no labeling of arcuate or interlobular arteries. The injection of lipopolysaccharide was associated with increased immunostaining for VSM-NOS in the afferent arteriole but had no effect on B-NOS staining. By electron microscopy, B-NOS immunostaining was present throughout the cytoplasm of the macula densa cells, where it appeared to be associated mainly with small vesicles. Immunostaining for VSM-NOS in the afferent arteriole exhibited a patchy distribution in some cells, whereas other cells were stained throughout the cytoplasm. These results indicate that two distinct isoforms of NOS are present in the juxtaglomerular apparatus and support the hypothesis that NOS is involved in the regulation of tubuloglomerular feedback and glomerular capillary pressure.

Amino Acid Oxidoreductases↗
PubMed1994

Effects of a calcium antagonist and an angiotensin II receptor antagonist on rat renal arterioles.

The objective of this study was to investigate the effects of a dihydropyridine calcium antagonist, manidipine HCl, and an angiotensin II receptor antagonist, CV-11974, on renal microvasculature in hypertensive rats. Hydronephrosis was induced by ligation of the left ureter in 8-week-old stroke-prone spontaneously hypertensive rats. Two months after the operation, the hydronephrotic kidney was split longitudinally and spread out as a thin sheet, and the renal microvasculature was observed directly under a light microscope. Administration of manidipine HCl (20 micrograms/kg) caused a gradual fall in blood pressure (-34 mmHg). The afferent arterioles were dilated, and maintained the same level of dilatation until 30 min (+20%). The efferent arterioles were also dilated (+8%). Glomerular blood flow was significantly increased (+38%). Administration of CV-11974 (100 micrograms/kg) caused a sharp fall in blood pressure at 2 min (-24 mmHg), with a continuous fall in blood pressure until 60 min (-46 mmHg). The afferent arterioles were gradually dilated (+15%). The efferent arteriole was also dilated until 60 min, but to a lesser extent than the afferent arteriole. Glomerular blood flow was immediately increased (+35%). We conclude that both manidipine HCl and CV-11974 dilated both the afferent and efferent arterioles and increased glomerular blood flow.

Angiotensin Receptor Antagonists↗
PubMed1993

An ets-related gene, ERG, is rearranged in human myeloid leukemia with t(16;21) chromosomal translocation.

The t(16;21)(p11;q22) translocation is a nonrandom chromosomal abnormality found in several types of myeloid leukemia, which show variable cytomorphological features. We constructed rodent-human somatic cell hybrids containing the der(16) chromosome from leukemic cells of a patient with t(16;21). Using these hybrids, we mapped the translocation breakpoint on the Not I restriction map of chromosome 21 which we had previously constructed. The result showed the proximity of the breakpoint to the ERG gene, a member of the ets oncogene superfamily. Polymerase chain reaction and Southern blot analyses of genomic DNA from the hybrids and from peripheral blood cells and bone marrow cells of patients with t(16;21) showed that the breakpoints were clustered within a single intron in the coding region of the ERG gene. This finding and the results obtained by Northern blot analysis suggested the formation of a chimeric product(s) by fusion of the ERG gene and an unknown counterpart gene on chromosome 16.

Acute Disease↗
PubMed1993

Binding of membrane-anchored macrophage colony-stimulating factor (M-CSF) to its receptor mediates specific adhesion between stromal cells and M-CSF receptor-bearing hematopoietic cells.

To explore the biologic significance of the membrane-anchored form of macrophage colony-stimulating factor (M-CSF), we examined whether interaction between membrane-bound M-CSF and its receptor mediates intercellular adhesion as well as cell proliferation and differentiation. Human M-CSF receptors were expressed on a murine interleukin-2 (IL-3)-dependent cell line, FDC-P2, by DNA transfection with the c-fms gene (FDC-P2-MCSFR). A human bone marrow-derived stromal cell line, KM102, was used in the cell adhesion assay. The expression of membrane-bound M-CSF on KM102 cells was demonstrated by flow cytometry and immunoblot analysis. After the incubation of parent and transformed FDC-P2 cells on confluent KM102 cells, nonadherent cells were removed and the cells attached to KM102 cells were examined microscopically. Almost all parent FDC-P2 cells were nonadherent, whereas a significant number of FDC-P2-MCSFR cells bound to KM102 cells. The addition of anti-M-CSF or anti-M-CSF receptor neutralizing antibodies dose-dependently inhibited the binding of [3H]-thymidine-labeled FDC-P2-MCSFR cells to KM102 cells. An excess amount of M-CSF also inhibited the binding. On the other hand, the addition of antibodies against some representative adhesion molecules (vitronectin receptor, Pgp-1/CD44, and VLA-4) did not inhibit the adhesion between FDC-P2-MCSFR cells and KM102 cells. These results support the idea that membrane-anchored M-CSF and its receptor may function as mediators of cell-cell adhesion.

Animals↗