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Biomedical subjects

T Ichimura

Publications and source records attributed to T Ichimura.

At least 109 records · Page 6Linked to original sources
PubMed1991

Regulation of rat proximal tubule epithelial cell growth by fibroblast growth factors, insulin-like growth factor-1 and transforming growth factor-beta, and analysis of fibroblast growth factors in rat kidney.

Growth factors may play an important role in regulating the growth of the proximal tubule epithelium. To determine which growth factors could be involved, we have investigated the mitogenicity of various purified factors in rat kidney proximal tubule epithelial (RPTE) cells cultured in defined medium. Fibroblast growth factors, aFGF (acidic FGF) and bFGF (basic FGF), stimulate DNA synthesis in a dose-dependent manner, with ED50 values of 4.5 and 3.2 ng/ml, respectively; their effects are not additive. With cholera toxin in the medium, both aFGF and bFGF can replace insulin or epidermal growth factor (EGF) to attain the maximum level of cell growth, but they cannot replace cholera toxin. Cholera toxin specifically potentiates the effects of FGFs on DNA synthesis. At high cell density, both insulin and insulin-like growth factor 1 (IGF-1) induce DNA synthesis more effectively than EGF, FGFs and cholera toxin. The high concentration (0.2-1.0 microgram/ml) of insulin required for cell growth can be replaced by a low concentration of IGF-1 (10-20 ng/ml), indicating that insulin probably acts through a low affinity interaction with the IGF-1 receptor. Transforming growth factor-beta 1 (TGF-beta 1) inhibits DNA synthesis induced by individual factors and combinations of factors in a concentration-dependent manner. Northern blot analysis shows that mRNA for TGF-beta 1, IGF-1, and aFGF, but not bFGF are present in rat kidney. Western blot analysis and bioassay data confirmed that the majority of FGF-like protein in rat kidney is aFGF. The data suggest that in addition to EGF, IGFs, and TGF-beta, FGFs may also be important kidney-derived regulators of proximal tubule epithelial cell growth in vivo and in vitro.

Animals↗
PubMed1991

Three-dimensional fine structure of cytoskeletal-membrane interactions at nodes of Ranvier.

Cytoskeleton-membrane-extracellular matrix interactions at the node of Ranvier were examined in both central and peripheral axons by combining three different methods for tissue preparation with three different electron microscopic techniques for imaging supramolecular structure. Conventional and three-dimensional high voltage electron microscopy of thin and semithick sections of tissues stained en bloc with ferric chloride revealed the presence of transcellular structures across the nodal gap traversing the paranodal glial-axonal junction. These structures penetrate both axonal and glial membranes and are further traced to the cortical axoplasm. This observation was verified by an examination of similar regions in rapidly-frozen freeze-substituted fresh axons. The filamentous nature of these structures, their focal attachment to the external true surface of the nodal and paranodal axolemma and their association with membrane particles were visualized in deep etch rotary-shadow replicas. At the node, both extracellular gap-crossing filaments and membrane-cytoskeletal linkers in the nodal axoplasm are joined to one of the prominent membrane particles of the nodal axolemma. At the paranodal axo-glial junction, the anchoring site of these membrane-cytoskeleton linkers are found on the linear arrays of 16 nm particles. Thus, cytoplasmic filaments and extracellular filaments or bridge structures are involved in the membrane-cytoskeletal interaction at the node and paranode. Some of these membrane particles are known to play a role in ionic conductances known to occur at this site. An additional role in cell adhesion or maintenance of the membrane specialization of this functionally important site of axolemma is now indicated.

Animals↗
PubMed1991

Molecular cloning of cDNA to rat 14-3-3 eta chain polypeptide and the neuronal expression of the mRNA in the central nervous system.

Activation of tyrosine and tryptophan hydroxylases, key enzymes for the catecholamine and serotonin biosynthesis, requires Ca2+/calmodulin-dependent protein kinase II and 14-3-3 protein which comprises a family of, at least, seven polypeptides in the bovine. Here we show that the amino acid sequence of the rat 14-3-3 eta chain deduced from the nucleotide sequence is completely identical to that of bovine counterpart. Using in situ hybridization the expression of mRNA for this protein is detected not only in the monoamine-synthetic neurons but also in many other discrete nuclei which synthesize neither catecholamine nor serotonin. The highly conservative structure between mammalian species and wider expression of this protein than expected in the central nervous system suggest that the 14-3-3 protein exerts some, though yet to be defined, functions fundamental to neuronal activities other than activation of the monoamine biosynthesis.

14-3-3 Proteins↗
PubMed1991

Widespread distribution of the 14-3-3 protein in vertebrate brains and bovine tissues: correlation with the distributions of calcium-dependent protein kinases.

A highly specific antiserum was prepared against bovine brain 14-3-3 protein, a protein kinase-dependent activator of tyrosine and tryptophan hydroxylases. The immunoassay using this antiserum proved the presence of 14-3-3 protein in various bovine tissues and in brains of various vertebrate species. The quantitative analysis indicated that the tissue distribution of 14-3-3 protein is more closely related to the known distributions of the Ca2(+)-dependent protein kinases, i.e., Ca2+/calmodulin- and Ca2+/phospholipid-dependent protein kinases, rather than those of tyrosine and tryptophan hydroxylases. This result, together with the available data on this protein, suggests potential roles of the 14-3-3 protein in more diverse kinase-mediated processes than the predicted role in monoamine synthesis.

14-3-3 Proteins↗
PubMed1991

Breathing patterns during sleep in stable asthmatic children.

Breathing patterns during sleep at night were studied in 15 asymptomatic asthmatic children and 11 nonasthmatic controls using impedance pneumography. Inspiratory time (TI), expiratory time (TE) and expiratory time/inspiratory time ratio (TE/TI) were used as the indices of breathing patterns. In the daytime, TI, TE and TE/TI, showed no significant differences between asthmatics and controls. During nocturnal sleep, TE and TE/TI increased significantly in the asthmatics compared with the value during daytime, while these values showed only a small variation overnight in the controls. TI showed no significant changes through the night in either the asthmatics and the controls. The results of this study indicate that the stable asthmatic children had abnormal breathing patterns during nocturnal sleep.

Adolescent↗
PubMed1991

Identification of a membrane protein responsible for ribosome binding in rough microsomal membranes.

A membrane protein fraction was obtained from rat liver rough microsomes by affinity chromatography on a concanavalin A-Sepharose column and then a chelating-Sepharose column. This protein fraction comprised about 2% of the total membrane proteins of rough microsomes and the ribosome-binding activity of ribosome-stripped rough microsomes was predominantly found in this protein fraction, as determined with a liposome assay system. To identify the essential components responsible for the ribosome binding, two approaches were employed. Trypsin treatment of liposomes reconstituted with this protein fraction resulted in the loss of the ribosome-binding activity in parallel with the loss of a dominant band, estimated Mr 34,000, in SDS-polyacrylamide gels. Next, the direct interaction between the binding sites on the membrane of reconstituted liposomes and 60S ribosomal subunits was investigated by photocrosslinking using sulfosuccinimidyl 2-(m-azido-o-nitrobenzamido)-ethyl-1,3'-dithiopropionate (SAND). The photocrosslinked complex was formed between 60S ribosomal subunits pretreated with SAND and binding-site proteins on the membrane of the liposomes. Then, after the liposomes were solubilized, the complex was isolated by sucrose gradient centrifugation of the binding mixture. The crosslinked proteins were released from 60S ribosomal subunits by cleavage of of crosslinks with beta-ME and analyzed by SDS-polyacrylamide gel electrophoresis and 125I-autoradiography. The 34-kDa protein (p34) was the predominant component that crosslinked to the 60S ribosomal subunits and was found in proportion to the amount of 60S ribosomal subunits added to the system. The p34 was distinguishable by immunoblot analysis from urate oxidase, which is the 34-kDa protein of peroxisomal cores contaminating rough microsomes. These results suggest that the present p34 is a likely candidate molecule for the ribosome-binding activity of rough microsomes.

Animals↗
PubMed1990

Breathing patterns in asthmatic children during attack.

Breathing patterns in asthmatic children during attack were studied using multielectrode impedance pneumography. A great number of respiration patterns were analyzed by a personal computer. During severe attacks, a pattern of prolonged expiratory time was noted. Inspiratory time, however, did not change, regardless of the severity of the asthmatic attack. No remarkable changes in breathing patterns were recognized during mild attacks. It was, therefore, considered that breathing patterns remained essentially unchanged except in cases of severe asthmatic attacks.

Adolescent↗
PubMed1989

Concurrent poststreptococcal acute glomerulonephritis and Schönlein-Henoch purpura.

A 5-year-old Japanese boy developed concurrent poststreptococcal acute glomerulonephritis (PSAGN) and Schönlein-Henoch purpura (SHP). An elevated titer of ASK on admission confirmed the preceding streptococcal infection. Arthritis of the left knee and petechiae on admission were regarded as features of SHP. The presence of SHP was further confirmed by the pathological finding of leukocytoclastic vasculitis in the skin. PSAGN was strongly suspected due to the findings of microscopic hematuria and hypocomplementemia in the acute phase. The concurrence of SHP and PSAGN suggests similar underlying pathophysiological processes as poststreptococcal sequelae. At the height of the illness, peripheral blood lymphocyte subset analysis showed a marked increase in the suppressor inducer T subset and a reciprocal decrease in the helper T subset. This alteration in T lymphocyte subsets was regarded as indicative of the immunological derangement in this patient.

Child, Preschool↗
PubMed1989

Five cases of autoimmune neutropenia in infancy or early childhood.

Five cases of chronic neutropenia which developed mainly in infancy were investigated and followed up for 5 to 34 months. Antineutrophil antibody levels were assayed by the direct and indirect immunofluorescence methods using flow cytometry. Selective neutropenia, myeloid hyperplasia and/or maturation arrest of myeloid series cells in the bone marrow, and the demonstration of antineutrophil antibody in the sera and on autologous neutrophils, indicated that the neutropenias involved were autoimmune in nature. Two cases exhibited spontaneous recovery 12 and 14 months respectively after the diagnosis, with concomitant marked decreases in antineutrophil antibody levels. Our study of these five cases supports the view that this disorder may be a clinical entity with a relatively consistent clinical presentation and course. Within this framework of the disorder, however, a clear heterogeneity in clinical presentation and course was also noted in our cases. Clinical severity in this disorder may be enhanced by arrested maturation of myeloid series cell in the bone marrow.

Agranulocytosis↗
PubMed1989

Chemistry and cell biology of neuron- and glia-specific proteins.

Studies of proteins specific to a certain type of cell are of general interest because these proteins may be involved in the determination of morphological and functional characteristics of the cell. In the nervous tissue, many "neuron-specific" and "glia-specific" proteins have been identified by various biochemical and immunohistochemical means and their relationships to cell functions have been studied. This paper briefly reviews our studies on the chemical and cell-biological aspects of the neuron- and glia-specific proteins, with special reference to the 14-3-3 protein and the S100 protein. Our studies suggest that glial protein S100 may be involved in the regulation of cell growth and differentiation, while neuronal protein 14-3-3, in the regulation of serotonin and catecholamine biosynthesis in neurons and other monoamine-synthesizing cells.

14-3-3 Proteins↗
PubMed1989

Induction of HLA-DQ antigen expression on a human promyelocytic leukemia cell line HL-60.

A variant strain of HL-60, which is positive for HLA-DR antigen, was induced to express HLA-DQ antigen following treatment with phorbol esther. It was preceded by cell cycle arrest in the G1 phase and was accompanied by augmented phagocytosis. This differential expression of HLA class II antigens on this subline may contribute to understanding the functional role of HLA class II antigens in the hematopoietic differentiation of macrophage cells.

Cell Cycle↗
PubMed1989

[Using specific radioimmunoassay for guinea pig VIP (GP VIP), immunoreactive GP VIP levels in respiratory tract tissue of normal and airway-allergic guinea pigs].

Vasoactive intestinal polypeptide (VIP) has recently received widespread attention with respect to its control of airway constriction, and is now regarded as the most promising candidate as a neurotransmitter for nonadrenergic noncholinergic inhibitory nerves in the airway. A specific system of radioimmunoassay (RIA) was devised to measure guinea pig VIP (gp VIP) concentration in airway tissue. An antiserum, R 550, was obtained by immunizing rabbits with newly synthesized gp VIP. The detectable VIP concentration was assessed to be 10 fmol/tube with the RIA system. The concentration of gp VIP in the respiratory tract tissue of normal guinea pigs was 0.04-0.22 pmol/g wet weight of tissue. The VIP level was highest in the trachea, in contrast to lower levels in both the major bronchus and lower lung. After being passively sensitized with ovalbumin, the experimental guinea pigs were exposed to the same antigen. After three minutes, as the expiration time was prolonged and the respiratory resistance increased, the immunoreactivity in the trachea and the major bronchus was significantly higher than the pre-exposure levels. After six hours, however, they returned to the original levels except in the lower lung where the level was constant throughout the respiratory change. As described above, the possibility of controlling airway constriction by VIPergic nerve in immediate-type allergic reactions is suggested by our findings.

Amino Acid Sequence↗
PubMed1988

[The measurement of plasma-free testosterone in normal menstrual females, pregnant females, post menopausal females and vulvar dystrophy].

It is considered that plasma-free testosterone is a bioactive androgen in blood and is more reflective in androgenicity than plasma total testosterone. We measured plasma-free testosterone by dialyzable method in normal menstrual females, pregnant females, post menopausal females and vulvar dystrophy. The values of plasma total testosterone (T), fractional free testosterone (%FT) and plasma-free testosterone (free T) were 0.61 +/- 0.27 (mean +/- SD)ng/ml, 1.19 +/- 0.34% and 0.61 +/- 0.20 ng/kl in the follicular phase of normal menstrual females (n = 25), and 0.57 +/- 0.23 ng/ml, 1.29 +/- 0.46% and 0.56 +/- 0.35 ng/dl in the luteal phase of normal menstrual females (n = 24), respectively. The values in both phases showed no differences from each other. In post menopausal females (n = 18), the concentration of T (0.36 +/- 0.27 ng/ml) and free T (0.52 +/- 0.12 ng/dl) was significantly lower (T: P less than 0.01, free T: P less than 0.05) than that in normal menstrual females. However, %FT in post menopausal females (1.37 +/- 0.12%) was not different as compared with that in normal menstrual females. In pregnant females (n = 2) of second and third trimester, T (0.53 +/- 0.07 ng/ml) was not different as compared with that in normal menstrual females, but %FT (0.67 +/- 0.45%) and free T (0.33 +/- 0.23 ng/dl) were significantly lower (P less than 0.05) than in normal menstrual females. In vulvar dystrophy, lichen sclerosus (n = 19) and hyperplastic dystrophy without atypia (n = 12) were measured.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1988

Structural components in the synaptic cleft captured by freeze-substitution and deep etching of directly frozen cerebellar cortex.

Structural components in the synaptic cleft were examined in cerebellar excitatory synapses by conventional electron microscopy and by rapid freezing followed by freeze-substitution or deep etching. Two transverse components and one parallel element were identified in the clefts of rapidly frozen and freeze-substituted synapses: (i) bridging fibrils, 4-6 nm in diameter, that span the cleft; (ii) columnar pegs, 4-6 nm wide and 8-15 nm high, projecting from the postsynaptic surface; and (iii) intervening fine fibrils running parallel to the apposed synaptic membranes. These were more clearly visible in deep-etched synapses, although the postsynaptic pegs were difficult to distinguish from intramembrane particles in the cross-fractured postsynaptic membranes. Deep etching also revealed other fibrils on the cytoplasmic surface of the postsynaptic membrane. These appear to contact the membrane surface or the intramembrane particles. Freeze-substituted materials also displayed the fibrillar components in the postsynaptic dense fuzz, but failed to display the presynaptic dense projections typically observed in thin sections or deep-etched replicas of the conventionally fixed materials. The bridging fibrils are likely to play a mechanical role in holding the synapse together, while the short pegs may be integral parts of the receptor molecules.

Animals↗
PubMed1988

Myoblast-mediated fusion-injection: a new technique for introduction of macromolecules specifically into living skeletal muscle cells.

A new technique for the introduction of macromolecules specifically into living skeletal muscle cells has been developed by a modification of the red blood cell ghost-mediated fusion-injection technique [M. Furusawa (1980) Int. Rev. Cytol. 62, 29-67]. Fluorescein-labeled bovine serum albumin (FITC-BSA) was introduced into chicken skeletal muscle myoblasts by the human red blood cell-mediated fusion-injection method in the presence of polyethylene glycol. Myoblasts loaded with FITC-BSA were then purified by a fluorescence cell sorter and cocultured with myotubes. Specific cell fusion between myoblasts and myotubes occurred under normal culture conditions and BSA was successfully introduced into living myotubes. This technique may provide a new method not only for the study of a given macromolecule's function in living muscle cells but also for therapeutic purposes such as muscle-specific drug delivery.

Animals↗
PubMed1988

Molecular cloning of cDNA coding for brain-specific 14-3-3 protein, a protein kinase-dependent activator of tyrosine and tryptophan hydroxylases.

The 14-3-3 protein is a family of acidic proteins present exclusively in the brain and is believed to have a function in monoamine biosynthesis because of its ability to activate tyrosine hydroxylase and tryptophan hydroxylase in the presence of Ca2+/calmodulin-dependent protein kinase type II. In this study, we resolved bovine brain 14-3-3 protein into seven polypeptide components by means of reversed-phase chromatography and determined the amino acid sequence of one of these components (eta chain) by cloning its cDNA from a bovine cerebellum cDNA library. The eta-chain mRNA is 1.8 kilobases long and encodes a polypeptide of 246 amino acids and Mr 28,221. Computer-assisted analysis of the sequence indicates that the eta chain exhibits no internal sequence repeats, nor does it have significant sequence similarity to other proteins with known amino acid sequence. However, the eta chain appears to consist of two structural regions that are distinguishable in their clearly different charge characteristics: the almost neutral amino-terminal region and the strongly acidic carboxyl-terminal region. The structural features of the eta chain and the domain organization of tyrosine and tryptophan hydroxylases suggest that the 14-3-3 protein binds to the regulatory domain of the phosphorylated hydroxylases through its acidic carboxyl-terminal region and activates the hydroxylases by inducing an active conformation.

14-3-3 Proteins↗