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S Yanagawa

Publications and source records attributed to S Yanagawa.

At least 19 recordsLinked to original sources
PubMed1995

The dishevelled protein is modified by wingless signaling in Drosophila.

Wingless (Wg) is an important signaling molecule in the development of Drosophila, but little is known about its signal transduction pathway. Genetic evidence indicates that another segment polarity gene, dishevelled (dsh) is required for Wg signaling. We have recently developed a cell culture system for Wg protein activity, and using this in vitro system as well as intact Drosophila embryos, we have analyzed biochemical changes in the Dsh protein as a consequence of Wg signaling. We find that Dsh is a phosphoprotein, normally present in the cytoplasm. Wg signaling generates a hyperphosphorylated form of Dsh, which is associated with a membrane fraction. Overexpressed Dsh becomes hyperphosphorylated in the absence of extracellular Wg and increases levels of the Armadillo protein, thereby mimicking the Wg signal. A deletional analysis of Dsh identifies several conserved domains essential for activity, among which is a so-called GLGF/DHR motif. We conclude that dsh, a highly conserved gene, is not merely a permissive factor in Wg signaling but encodes a novel signal transduction molecule, which may function between the Wg receptor and more downstream signaling molecules.

Adaptor Proteins, Signal Transducing↗
PubMed1995

Progressive decrease in heteronymous monosynaptic Ia facilitation with human ageing.

To evaluate functional change in the spinal reflex pathway with ageing, we studied heteronymous Ia facilitation from the quadriceps to soleus muscle in 30 normal volunteers (aged 24-68 years). The size of the test H-reflex of the soleus muscle was adjusted to 25% that of the maximal M-response. The conditioning stimulus was adjusted to 1.5-fold the motor threshold to stimulate all the Ia fibres in the femoral nerve. Facilitation was quantified as the slope of the very early part of facilitation, within 0.8 ms of onset. This procedure enabled us to evaluate the extent of monosynaptic Ia facilitation without contamination by other effects. The extent of facilitation decreased linearly with age. This decrease in facilitation could reflect a decrease in the number of Ia fibres and in their conduction velocities, and an increase in presynaptic inhibition on Ia terminals. The increase in presynaptic inhibition may be an adaptive phenomenon in the ageing of the neuromuscular system or, alternatively, a deteriorating process with decreasing flexible supraspinal modulation.

Adult↗
PubMed1994

Conditioning effect in single human motoneurones: a new method using the unitary H reflex.

1. A new method for the study of spinal reflexes using single motor units is described. 2. The excitability of a motoneurone is assessed as the 'critical firing stimulus' (CFS), which is the difference between the test stimulus intensity needed to reach the threshold for the lowest threshold Ia fibres and the intensity which evokes firing of a motor unit with the probability of 50% (FP50%). The intensity with FP50% is obtained by modulating stimulator output. When the motor unit is fired by a stimulus, the next intensity is decreased, and vice versa. The Ia threshold is defined as the threshold for homonymous monosynaptic peaks in PSTHs during contraction of the muscle examined. 3. A conditioning effect is represented as a change in CFS, the extent being expressed as a percentage of the unconditioned CFS. 4. Effects obtained by conditioning stimulation with the new and conventional H reflex methods are compared. The sensitivities are almost the same and the extents of the effects have highly correlated linear relations for the two methods. 5. The advantages of the new method are (1) that it shows reflex activities on a single motoneurone, (2) that it is applicable both to muscles at rest and during contraction, and (3) that it quantifies conditioning effects as percentages of the size of test Ia EPSPs.

Adult↗
PubMed1993

Neuromuscular response in man to repetitive nerve stimulation.

Paired stimulation has been used extensively in clinical neurophysiology. We studied change in the sizes of compound muscle action potentials (CMAPs) and compound nerve action potentials (CNAPs) in humans after a single electrical stimulus to the peripheral nerve. For the paired stimuli, potentials elicited by the first stimuli were used as the test responses. When the interstimulus intervals were varied, the second potentials underwent refractoriness and then were facilitated up to 20-30 ms, thereafter being depressed for 160-200 ms. When intensities were graded at fixed intervals for motor fibers the maximal effect was obtained with liminal stimulation, but was no longer observed at supramaximal stimulation. When the intensity used to obtain M-responses was half the maximum, maximal facilitations were 35% (CNAP) and 17% (CMAP) of the first potential, the respective maximal depressions being 13% and 42%. When the sizes of the two CNAPs were equalized by adjusting the second stimuli, the CMAP was facilitated (26%) up to 65 ms, thereafter being depressed (13%). These results must be taken into account when making clinical examinations that use paired stimulation.

Action Potentials↗
PubMed1993

Mouse mammary tumor virus with rearranged long terminal repeats causes murine lymphomas.

Mouse mammary tumor virus (MMTV) is a slowly transforming retrovirus associated primarily with the induction of mammary tumors. It is widely accepted that T-cell lymphomas of various mouse strains are associated with extra proviruses of MMTV. These extra proviruses showed site-specific rearrangements in the U3 region of long terminal repeats (LTRs), consisting of about 400 nucleotide deletions and occasional substitution resulting in unique tandem repeats. However, the question of whether these mutant MMTVs cause lymphomas has not been experimentally resolved. Here we present distinct evidence that they do. We constructed chimeric MMTVs by replacing the LTR of the recently constructed pathogenic MMTV provirus clone with rearranged LTRs of MMTV proviruses obtained from two DBA/2 mouse lymphoma cell lines, MLA and DL-8, and inoculated them into BALB/c mice. These mice developed lymphomas, but no mammary tumors, 4 to 11 months postinoculation, whereas the original pathogenic MMTV clone alone induced mammary tumors. These results showed that the tissue specificity of MMTV tumorigenesis is determined by the LTR structures.

Animals↗
PubMed1993

[Intensive 1-(4-amino-2-methyl-5-pyrimidinyl) methyl-3-(2-chloroethyl)-3- nitrosourea hydrochloride (ACNU) and cryopreserved autologous bone marrow transplantation].

High-dose ACNU followed by autologous bone marrow transplantation was administered alone or together with other agents such as cyclophosphamide, dacarbazine, carboquone or/and VP-16. The starting dose of ACNU was 200 mg/m2, with gradual escalation up to 400 mg/m2. Median duration of granulocytes of less than 100/mm3 and platelets of less than 30,000/mm3 was 4.5 days (range; 0-9) and 10.5 days (range; 0-43), respectively. Bacteremia occurred in 4 cases, but no case of pneumonia was encountered. Heart failure possibly due to the cyclophosphamide was noted in one case with arrhythmia. Out of 13 cases with measurable diseases, three patients with Hodgkin's disease, two patients with diffuse lymphoma, and one patient with follicular lymphoma attained a complete response. Partial response was obtained in two patients with non-Hodgkin's lymphoma. Two patients with melanoma and one with acute nonlymphocytic leukemia without measurable disease still remain disease-free.

Adult↗
PubMed1992

Myotonic and repetitive discharges in hypokalemic myopathy associated with glycyrrhizin-induced hypochloremia.

Electromyographic studies were performed in two patients with hypokalemic myopathy induced by the administration of glycyrrhizin, 270-273 mg per day for a period of two and eight months, respectively. Myotonic and repetitive discharges were observed when the serum chloride level fell below 90 mEq/l. Following the administration of potassium chloride, when the chloride level rose above 90 mEq/l, these discharges disappeared. These findings support the causal role of hypochloremia in myotonic discharges. A serum chloride level below 90 mEq/l appears to be critical in producing the myotonic and repetitive discharges.

Aged↗
PubMed1992

Presence of transplantable T-lymphoid cells in C57BL/6 mice infected with murine AIDS virus.

The Duplan strain of murine leukemia virus induces murine AIDS in C57BL/6 mice. When spleen cells from C57BL/6 mice infected with the virus were transplanted into nude mice, subcutaneous solid tumors at the transplanted sites were formed and splenomegaly and lymphadenopathy were induced. These transplantable cells were Thy-1- CD4+ alpha-beta T-cell receptor-positive T cells and integrated with the pathogenic defective viral genome. These results indicate that neoplastic cells of T-cell lineage were induced by infecting C57BL/6 mice with murine AIDS virus.

Animals↗
PubMed1991

Increase in Ib inhibition by antagonistic voluntary contraction in man.

1. Ib inhibition from gastrocnemius medialis (GM) muscle to soleus (Sol) muscle was studied at rest and at the onset of phasic voluntary contraction of antagonistic pretibial muscles in seventeen normal subjects. 2. In twelve out of seventeen subjects there was inhibition of Sol H reflex by GM conditioning stimulation at rest with a latency of 1.5-3.0 ms and a threshold of 0.85-1.00 times the motor threshold (MT). The amount of inhibition at 0.95-1.05 x MT, which was calculated by subtracting the size of the conditioned reflex from that of the unconditioned one, ranged from 0.8 to 5.6% of the maximal M-response or 2.9-18.3% of control H reflex. This inhibition was ascribed to Ib inhibition, taking into account its latency and threshold. 3. On weak pretibial contraction the inhibition either increased in amount or newly appeared in all the subjects. When the strength of voluntary contraction was graded from 1 to 20% of the maximum, the increment in the amount of inhibition decreased or almost disappeared at strengths of more than several per cent. These facts imply that at least some of the Ib interneurones are facilitated to fire by descending commands alone without peripheral Ib impulses. Contralateral ankle dorsiflexion did not modify the inhibition. 4. Soleus muscle H reflex was not modulated at all by cutaneous stimulation instead of GM stimulation at rest, nor was it affected by cutaneous stimulation on ipsilateral antagonistic contraction. 5. It is concluded that activity in the Ib inhibitory pathway is facilitated at the onset of antagonistic voluntary contraction. This suggests that control of the Ib inhibitory pathway may be utilized in ordinary voluntary movement, and is presumably beneficial for smooth execution of movement.

Adult↗
PubMed1991

Identification of a novel mammary cell line-specific enhancer element in the long terminal repeat of mouse mammary tumor virus, which interacts with its hormone-responsive element.

We analyzed the long terminal repeat (LTR) of mouse mammary tumor virus for sequences that influence its promoter activity by using the chloramphenicol acetyltransferase assay. A series of LTR deletion mutants and recombinants between LTR and simian virus 40 regulatory sequences were used for these studies. Through transfection experiments in three different human cell lines (T47D, MCF-7, and HeLa), we identified a novel mammary cell line-specific enhancer element on a 98-bp BanII fragment (from position -1075 to -978 upstream of the start site of transcription) which interacts with the hormone-responsive element of LTR. We also identified nuclear factors that specifically interacted with this BanII fragment in the nuclear extract from the mammary tumor cell line, T47D, but not from the HeLa cell line.

Breast Neoplasms↗
PubMed1991

Intraoperative radiation therapy for malignant glioma.

Intraoperative radiation therapy (IORT) was used as part of the initial therapy for malignant glioma in 32 of 73 patients with histologically verified anaplastic astrocytoma (grade III astrocytoma) and glioblastoma multiforme. The initial treatment for all cases was subtotal or total tumor resection combined with external irradiation and chemotherapy. IORT was performed 1 week after tumor resection, with doses of 10-50 Gy (mean 26.7 Gy) in one session. Fourteen of 32 cases had IORT two times because of tumor recurrence. The IORT patients had survival rates at 24 and 36 months after initial treatment of 57.1 and 33.5% (median survival 26.2 months). The other 41 patients had 23.6 and 13.1% survivals (median survival 20.7 months), which were significantly lower (p less than 0.01). Tumor recurrence within the original lesion site was suspected because of clinical condition, computed tomography, and magnetic resonance imaging studies in 65.6% of the IORT group (21 cases) 12 months after initial treatment. Twenty cases of death in the IORT group, including five autopsy cases, demonstrated regional tumor recurrence with a high incidence of intraventricular tumor invasion. The authors consider IORT is beneficial for selected malignant glioma patients, including tumor recurrence, because of prolonged survival.

Adolescent↗
PubMed1990

Fv-1 restriction of endogenous feline C-type RD114 virus genome phenotypically mixed with ecotropic murine leukemia viruses.

Endogenous feline leukemia RD114 virus genome rendered capable of infecting mouse cells by phenotypic mixing with an ecotropic murine leukemia virus (MuLV) exhibited the Fv-1 restriction pattern of the ecotropic murine virus. However, RD114 genomes phenotypically mixed with ecotropic MuLV showed one-hit dose-response kinetics, even when titrated with murine cells with the restricted Fv-1 phenotype.

AKR murine leukemia virus↗
PubMed1990

Extra mouse mammary tumor proviruses in DBA/2 mouse lymphomas acquire a selective advantage in lymphocytes by alteration in the U3 region of the long terminal repeat.

We determined the nucleotide sequences of the long terminal repeats (LTRs) from mouse mammary tumor virus (MMTV) proviruses acquired in two DBA/2 mouse lymphoma cell lines, MLA and DL-8. Proviruses from MLA contained a 352-base-pair deletion from nucleotides 669 to 1020 in the U3 region of the LTR, whereas the LTR alteration of the DL-8 provirus involved both a similar 360-base-pair deletion and generation of a tandem repeat region consisting of sequences of flanking deletions. To assess the function of the rearranged LTRs, we constructed plasmids in which normal and rearranged LTRs drove the reporter chloramphenicol acetyltransferase gene and transfected them into T-cell lines (Jurkat, Molt-3, and DL-8) and the mammary tumor cell line T47D. Both rearranged LTRs were transcriptionally active, but normal LTRs were not active in either the presence or absence of glucocorticoids in all T-cell lines. In T47D cells, however, the MLA provirus LTR showed the same glucocorticoid- or progestin-dependent transcriptional activity as did normal LTRs. The DL-8 provirus LTR acquired a novel enhancer(s) by rearrangement and thus had a high basal transcriptional activity in T47D cells. The results of chloramphenicol acetyltransferase assays using plasmids with various chimeric MMTV LTRs revealed that the rearranged LTRs had lost their negative regulatory element and contained an enhancer element that was highly homologous to the enhancer A element of polyomavirus (from nucleotides 525 to 558). GR but not C3H mouse MMTV contained this enhancer. These results elucidate some of the molecular mechanisms involved in the selection of mutant MMTVs with rearranged LTRs in lymphoma cells.

Animals↗
PubMed1990

[Delayed effects of radiation of patients with germ-cell tumor, with special to cerebral blood flow].

Delayed effects of radiation therapy (RT) on twenty patients with germ-cell tumors, including 17 cases of germinoma, were evaluated with special reference to cerebral blood flow (CBF). All patients except for one of germinoma had craniotomy to verify the tumor histology, then RT followed with a total dose of 39.6 to 60 Gy for each patient. A follow-up study with CT scans and MRI proved not any recurrence of the tumors during the past 14-year period between June, 1975 and April, 1989. On the other hand, CBF was measured by 133Xe inhalation 1 to 14 years after RT. 40% of all patients were below critical values of CBF with higher frequency in the younger. Statistically, the post-irradiated changes of CBF were not related to a total administered dose, grading of brain atrophy, or physical mental developments, but closely related to irradiated volume dose (product of absorbed dose and field, rad.cm3) only for the age ranging from 8 to 15 years at RT. These results suggested that late effects of RT on CBF were more strongly depend upon absorbed dose and field of irradiation to brain in children than in adolescents.

Adolescent↗