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Biomedical subjects

R Sasaki

Publications and source records attributed to R Sasaki.

At least 163 records · Page 9Linked to original sources
PubMed1994

Distinct inhibition by non-peptide and peptide arginine vasopressin antagonists of vasopressin-induced activation of mitogen-activated protein kinase in cultured rat vascular smooth muscle cells.

The preincubation of vascular smooth muscle cells (VSMC) with a non-peptide arginine vasopressin (AVP) antagonist (OPC-21268) (0.5 mM) for 10 min completely inhibited the 1 microM AVP-induced activation of mitogen-activated protein (MAP) kinase but did not affect the angiotensin II-, protein kinase C activator- or ionomycin-stimulated MAP kinase. Similar results were obtained with the simultaneous administration of AVP and OPC-21268. This inhibitory effect of OPC-21268 completely disappeared after washing the cells pretreated with OPC-21268. In contrast, the preincubation of VSMC with a peptide AVP antagonist, d(CH2)5Tyr(Me)AVP (1 microM), for 10 min completely blocked the 1 microM AVP-activated MAP kinase but the simultaneous administration of d(CH2)5Tyr(Me)AVP with AVP could inhibit that only by 40%. However, the washing procedure did not affect the inhibitory effect of d(CH2)5Tyr(Me)AVP. These results indicate that OPC-21268 is a specific AVP antagonist to inhibit the AVP-induced activation of MAP kinase. The antagonistic effect of OPC-21268 is also suggested to be relatively weak but prompt as compared to that of a peptide AVP antagonist d(CH2)5Tyr(Me)AVP.

Angiotensin II↗
PubMed1994

N-glycosylation of erythropoietin is critical for apical secretion by Madin-Darby canine kidney cells.

Erythropoietin (Epo) has three N-linked carbohydrate chains at positions 24, 38, and 83 in its 166-amino acid residues. When the human wild-type Epo was expressed in the polarized Madin-Darby canine kidney (MDCK) epithelial cells, Epo was preferentially secreted from the apical domain. The polarized secretion was perturbed by the treatment of the cells with tunicamycin, suggesting the involvement of N-linked carbohydrate chains in the apical sorting mechanism in MDCK cells. Replacement of asparagine residues at all N-glycosylation sites of Epo with glutamine by site-directed mutagenesis resulted in roughly equal secretion from apical and basolateral domains. Comparative studies on MDCK clones expressing the mutant Epos lacking one or two of the three N-glycosylation sites in every possible combination showed that the N-linked carbohydrate chain at position 38 is critical for the polarized secretion. Nocodazole, a microtubule-disrupting drug, reversed the polarized secretion of the wild-type Epo from the apical to basolateral preference with little change in the total secretion. Hepatocyte growth factor, a scatter factor known to induce the tubule-like structure of MDCK cells, caused almost equal secretion of the wild-type Epo into the apical and basolateral sides, although the tight junctions of MDCK cells remained intact.

Animals↗
PubMed1994

Increase caused by interleukin-6 in promoter activity of guinea pig liver transglutaminase gene.

A 5'-flanking region (-2024 to +61) of the guinea pig liver transglutaminase gene and some 5'-deletion mutants were tested for promoter activity in human hepatoblastoma HepG2 cells treated with interleukin-6 (IL-6) by an assay of the transient expression of the chloramphenicol acetyltransferase reporter gene. The promoter activity of the 5'-flanking region introduced into the HepG2 cells was increased by IL-6.

Animals↗
PubMed1994

A novel hypothyroid 'growth-retarded' mouse derived from Snell's dwarf mouse.

This paper describes a novel mutant mouse that has been spontaneously derived from the Snell's dwarf (DW/J) mouse. It was named the 'growth-retarded mouse' because of a characteristic growth pause followed by the delayed onset of pubertal growth. The onset of the increase in pituitary GH content that normally occurs concomitant with pubertal growth was also delayed in the growth-retarded mice. The serum concentration of thyroxine was very low in these mice from the neonatal period through adulthood, and a supplement of tri-iodothyronine was effective in shortening the growth pause and commencing the suppressed pubertal growth. Histological and immunohistochemical studies revealed that the anterior pituitary gland of the growth-retarded mouse contains clustered unusual chromophobic cells which are not reactive to various antisera against anterior pituitary hormones and the gland becomes enlarged with age. Breeding data indicated that these characteristics of the mice show an autosomal recessive inheritance and the gene responsible was designated as 'grm'. Partial linkage analysis utilizing microsatellite polymorphism demonstrated that the grm gene does not identify with the lit or hyt genes. Based on comparison of the hormonal status and growth pattern between growth-retarded, dwarf and normal mice, we have suggested the existence of a mutual interaction, possibly positive feedback regulation, between the pituitary and thyroid glands, that develops or matures the hormonal network which is responsible for rapid somatic growth and metabolic changes at puberty in mice.

Animals↗
PubMed1994

Isolation and characterization of oryzatensin: a novel bioactive peptide with ileum-contracting and immunomodulating activities derived from rice albumin.

A novel bioactive peptide was isolated from the tryptic digest of rice soluble protein based on ileum-contracting and anti-opioid activities in the isolated guinea pig ileum. The structure of the peptide was Gly-Tyr-Pro-Met-Tyr-Pro-Leu-Pro-Arg, and it was named oryzatensin. Oryzatensin showed a biphasic ileum-contraction, which was characterized by a rapid contraction followed by a slower one. The latter was mediated by the cholinergic nervous system because it was inhibited by tetrodotoxin and atropine. Although oryzatensin showed weak affinity for mu-opioid receptors, the apparent anti-opioid activity seemed to be associated with the slower contraction. On the other hand, oryzatensin showed phagocytosis-promoting activity for human polymorphonuclear leukocytes and augmented the production of superoxide anion by human peripheral leukocytes.

Adjuvants, Immunologic↗
PubMed1994

[A family of parkinsonism in which the clinical feature of constituents varied with the age of onset].

We report a family of parkinsonism in which the clinical feature of the constituents varied with the age of onset. The propositus was a 49-year-old woman who had developed tremor and akinesia at the age of 26 years. Levodopa markedly relieved her symptoms. The feet showed pes equinovarus with tonic extension of the great toe. The most characteristic feature was marked diural fluctuation of her symptoms; her gait was nearly normal in the morning, while she showed marked tremor and gait disturbance with parkinsonian posture in the evening. Sleep markedly improved her conditions. Her maternal uncle developed parkinsonism at the age of 60 years, and anti-parkinsonian drugs including levodopa were persistently effective. Neurological examination at the age of 75 years revealed parkinsonian features with rigidity, resting tremor, akinesia and loss of postural reflex, together with severe pes equinovarus and tonic extension of the great toe. There was no diural fluctuation in his symptoms. Several types of dystonia-parkinsonism, either familial or sporadic, have been reported in the literature, but none of them showed the same clinical and genetic features as the present family. The present family may be included in a spectrum of dystonia-parkinsonism syndrome of autosomal-dominant inheritance.

Age of Onset↗
PubMed1994

[Transverse myelopathy caused by aneurysmal bone cyst of the thoracic vertebra in an old person].

A 63-year-old woman developed progressive weakness and sensory disturbance in the legs, and had to walk with a stick three months later. Neurological examination revealed symptoms of transverse myelopathy at the level of the first lumbar cord. The plain X-rays revealed flattening and osteolytic changes of the 11th thoracic vertebra which suggested a spine tumor. CT showed a destruction of the 11th vertebra which invaded the spinal canal. The 11th vertebral body and the arches were filled by lobulated tumor masses. MRI of the spine revealed the 11th vertebra to be low in T1 and high in T2 images with marked spotty enhancement effect by gadolinium. The neighboring discs and spines were not involved by the tumor. The tumor was surgically resected with resultant massive bleeding. Histological diagnosis of the tumor was aneurysmal bone cyst. She developed a postoperative stress ulcer with perforation, but recovered. Finally she was able to walk without a stick nine months after surgery. Aneurysmal bone cyst, though very rare in elderly persons, should be considered in differentiating spine diseases which cause transverse myelopathy. It is important to make a preoperative diagnosis because severe bleeding may occur during a surgical procedure, as was seen in our case.

Bone Cysts, Aneurysmal↗
PubMed1994

[A case of acute promyelocytic leukemia (APL) with myeloblastoma in the oral cavity developing after receiving all-trans retinoic acid (ATRA)].

A 44-year-old woman was diagnosed as having acute promyelocytic leukemia (APL) in April 1988. On her first admission, chromosomal translocation (15; 17), +8, and +12 was detected. When she was readmitted to our hospital with the second relapse in May 1990, t(3; 13) and +8 was detected, instead of t(15;17). Complete remission was re-achieved with VP-16, MIT, and BHAC, but the third relapse occurred in September 1990. After obtaining informed consent, she was given etretinate 40 mg per day orally for 17 days, without any effect on leukemia. She was then given all-trans retinoic acid (ATRA) 60 mg per day orally for 29 days. Although a mild granulocytic recovery was observed, no sufficient hematological recovery was obtained (minor response). Besides common side effects of ATRA, such as dry skin and hypertriglycedemia, she had a myeloblastoma in the oral cavity, but it is unknown whether the symptom was a complication of ATRA therapy or not.

Administration, Oral↗
PubMed1993

Cross-linking of a synthetic partial-length (1-28) peptide of the Alzheimer beta/A4 amyloid protein by transglutaminase.

Cerebral deposits of beta/A4 amyloid protein is a pathologic sign of Alzheimer's disease. A synthetic partial-length (1-28) peptide of this protein contains one glutamine and two lysine residues. Here we show that this peptide can be a substrate of transglutaminase, which catalyzes cross-linking between glutamine and lysine residues in peptides, by demonstrating the formation of multimeric peptides due to the action of this enzyme. A modified (Lys28 to L-norleucine) version of the synthetic peptide was also cross-linked, but another modified version (Lys16 to L-norleucine) was very poorly cross-linked, indicating that Lys16 is involved exclusively in the cross-linking of the partial-length peptide catalyzed by transglutaminase.

Alzheimer Disease↗
PubMed1993

Functional erythropoietin receptor of the cells with neural characteristics. Comparison with receptor properties of erythroid cells.

Radioiodinated erythropoietin (Epo) was bound specifically to the cells of two non-erythroid clonal lines, PC12 and SN6, which expressed neuronal characteristics. The binding was time-, cell number-, and dose-dependent and was reversible. Although the cloned Epo receptor from PC12 cells (derived from rat adrenal medulla) was identical to that from rat erythroid cells, significant differences in the ligand binding properties between two cell lineages were found; 1) PC12 cells had a single class of binding sites with very low affinity (Kd = 16 nM), whereas erythroid cells had two classes of binding sites with different affinities (Kd = 95 pM for high affinity sites and 1.9 nM for low affinity sites), and 2) cross-linking experiments revealed one cross-linked product of 105 kDa for PC12 cells and two products of 140 and 120 kDa for erythroid cells. Taken together with additional results, the presence of a putative accessory protein(s) that may alter the ligand binding affinity through interaction with Epo receptor is discussed. The binding of Epo to PC12 cells caused a rapid increase in the cytosolic concentration of free calcium. The presence of EGTA had no effect on the Epo binding but completely inhibited the calcium increase, indicating that Epo stimulated the calcium influx from outside of the cells. The addition of Epo to the culture media of PC12 cells elevated the intracellular concentrations of monoamines.

Adrenal Medulla↗
PubMed1993

Effect of tunicamycin treatment on ligand binding to the erythropoietin receptor: conversion from two classes of binding sites to a single class.

Scatchard analyses of erythropoietin (EPO) binding to its receptor (EPO-R) have shown that some erythroid cells display a biphasic nature of the ligand-saturation curve, indicating the presence of two classes of binding sites with different affinities. The biochemical basis accounting for this observation is unknown. We found that the culture of a human erythroleukemia cell line with tunicamycin, an inhibitor of N-glycosylation, converted the biphasic Scatchard plot to a single phase with high-affinity sites. Scatchard plots of baby hamster kidney (BHK) cells that had been engineered to express cloned mouse EPO-R were also biphasic and the plots of cells cultured with tunicamycin became a single phase with high-affinity sites. Mouse EPO-R is glycosylated at one asparagine residue in the extracellular region. The mutant EPO-R, in which asparagine residue responsible for N-glycosylation was replaced with glutamine residue, was expressed on BHK cells. Unexpectedly, mutant EPO-R was similar in ligand binding to wild-type EPO-R. BHK cells that expressed mutant EPO-R showed biphasic Scatchard plots that were converted to single-phase plots with only high-affinity sites by tunicamycin treatment. These results indicate that the N-linked sugar of EPO-R is not involved in the manifestation of two classes of binding sites, and that there is a yet unidentified glycoprotein crucial for the ligand-saturation characteristics of EPO-R.

Amino Acid Sequence↗
PubMed1993

Expression induced by interleukin-6 of tissue-type transglutaminase in human hepatoblastoma HepG2 cells.

We examined the effect of interleukin-6 (IL-6) on the expression of transglutaminase in human hepatoblastoma HepG2 cells. Treatment of cells with IL-6 increased their transglutaminase activity in a time- and dose-dependent way. Dexamethasone strengthened the stimulation by IL-6. Half-maximum stimulation of transglutaminase activity in the cells occurred at a dose of 40 pM IL-6 regardless of the presence of dexamethasone. Based on its immunoreactivity, the transglutaminase induced was identified as tissue-type transglutaminase. Immunoblot analysis showed that the increase in transglutaminase activity was related to an increase in the amount of transglutaminase protein. Northern blot analysis with a cDNA probe specific for human tissue-type transglutaminase showed that exposure of HepG2 cells to IL-6 increased the mRNA level of the enzyme, and the increase was detectable 3 h after IL-6 was added. Induction of the mRNA was maximum between 10 and 14 h. The increase in the mRNA level was not blocked by the presence of cycloheximide, suggesting that the increase was independent of protein synthesis. Injections into mice of substances that induce inflammation such as turpentine and lipopolysaccharides increased the liver transglutaminase activity. These results indicated that transglutaminase may be involved in some biological processes in hepatocytes regulated by IL-6 signaling.

Animals↗
PubMed1993

Identification of promoter region of guinea pig liver transglutaminase gene.

A 5' flanking region of the guinea pig liver transglutaminase gene was cloned and sequenced. The sequences for TATA box and potential binding sites of some regulatory factors were found in this region. The promoter activity of this region was shown by transfecting its fusion-construct with the chloramphenicol acetyltransferase gene into human hepatoblastoma HepG2 cells.

Animals↗
PubMed1993

Connection of atopic disease in Japanese patients with juvenile dermatomyositis based on serum IgE levels.

Serum IgE levels of 22 patients with juvenile dermatomyositis (JDMS), 44 normal children, and 43 patients with adult dermatomyositis were compared. The geometric mean of serum IgE levels was significantly higher in the juvenile patients when compared with normal children (p < 0.01) and adult patients (p < 0.01). Of the 22 patients with JDMS, 11 (50%) had elevated serum IgE levels accompanied by atopic disease. Dermatomyositis was accompanied by atopic dermatitis (AD) in 9 (41%) of these 22 patients, a high prevalence when compared with reports among the general population. Following the appearance of muscular symptoms in JDMS patients with AD, the ratio of OKT4 to OKT8 cells rose due to a reduction in the percentage of OKT8-positive cells, along with further elevations in serum IgE levels and intractable cutaneous manifestations of dermatomyositis. All this may be a result of an interaction between the immuno-mechanism of this disease and that of AD. We suspect that, in general, children with impaired cell-mediated immunity, presenting with such symptoms as AD, may have a higher tendency for developing JDMS.

Adolescent↗
PubMed1993

Analysis of lymphocyte subpopulations in peripheral blood in adult and juvenile cases of dermatomyositis.

Dermatomyositis, recognized as an autoimmune disorder, occurs not only in adults but also in children. In this study, we evaluated lymphocyte subpopulations in the peripheral blood of 24 adult dermatomyositis and 14 juvenile dermatomyositis patients and in 17 healthy adults and 9 healthy children by flow cytometry using monoclonal antibodies. When compared with healthy adults and adult patients with inactive dermatomyositis, the adult patients with active disease had significantly lower percentages of CD3+ and CD8+ cells and a significantly higher percentage of CD20+ cells. In contrast, juvenile dermatomyositis patients had lymphocyte subpopulations not significantly different from those of healthy children; the activity/inactivity of disease did not make any difference. These results support our hypothesis that adult and juvenile dermatomyositis may be diseases of entirely different scope.

Adult↗
PubMed1993

Expression of human erythropoietin in cultured tobacco cells.

Human erythropoietin (Epo) cDNA was engineered for expression in cultured tobacco cells (Nicotiana tabacum L. cv. BY2). Two plasmid DNAs were constructed: pCEP, which contained Epo cDNA under control of the cauliflower mosaic virus-derived 35S RNA promoter and terminator, and pNSEP, which contained signal sequence-deleted Epo cDNA under control of the 35S RNA promoter and terminator. By using the electroporation method, each of these plasmid DNAs was transferred into the protoplasts of BY2 cells together with a plasmid, pNR35, which conferred G418-resistance on the cells. Four G418-resistant clones were obtained from protoplasts transfected with pNSEP and pNR35, and only one of them, named 11N, survived in suspension culture. Integration of pNSEP DNA into the genome of 11N cells was confirmed by Southern blot and PCR analyses. Production of Epo mRNA was shown by Northern blot analysis. Epo protein was shown to be expressed in 11N cells by colorimetric enzyme immunoassay. The productivity of Epo in the 11N cells (1 pg/g of wet cells) was very low.

Amino Acid Sequence↗