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Biomedical subjects

Y Endo

Publications and source records attributed to Y Endo.

At least 559 records · Page 31Linked to original sources
PubMed1988

The cytotoxins alpha-sarcin and ricin retain their specificity when tested on a synthetic oligoribonucleotide (35-mer) that mimics a region of 28 S ribosomal ribonucleic acid.

An oligoribonucleotide (35-mer) that mimics the alpha-sarcin and the ricin region of eukaryotic 28 S rRNA was transcribed in vitro from a synthetic template with T7 RNA polymerase and was used to test whether the specificity of the hydrolysis by the toxins was retained. alpha-Sarcin, at a low concentration, cleaved a single phosphodiester bond on the 3' side of a guanosine residue in the synthetic oligomer that corresponds to G-4325 in 28 S rRNA, the site of action of the toxin in intact ribosomes. At a high concentration of alpha-sarcin, the substrate (35-mer) was hydrolyzed after each of its purines. alpha-Sarcin was without an effect on a synthetic RNA (20-mer) that reproduces the near universal sequence of nucleotides in the loop, but lacks the stem, of the toxin's domain. Thus, the specificity of the attack of alpha-sarcin on a precise region of 28 S rRNA appears to be contingent on the sequence of the nucleotides and the structure of the domain. Ricin depurinated a nucleotide in the synthetic oligomer (35-mer), and in the presence of aniline the phosphoribose backbone was cleaved at a position that conforms to A-4324 in 28 S rRNA, the site of action of the toxin in vivo.

Base Sequence↗
PubMed1988

The mechanism of action of barley toxin: a type 1 ribosome-inactivating protein with RNA N-glycosidase activity.

In a previous report (Endo, Y. and Tsurugi, K. (1987) J. Biol. Chem. 262, 8128-8130) it was shown that the RNA N-glycosidase activity of ricin A-chain was responsible for the ability of this protein to inactivate eukaryotic ribosomes. The objective of the present study was to determine whether a similar mechanism was used by a ribosome-inactivating protein from pearled barley (barley toxin). Rat liver ribosomes were incubated either with ricin A-chain or barley toxin, and the rRNA was extracted and treated with acidic aniline to hydrolyze phosphodiester bonds rendered susceptible by removal of a purine or pyrimidine base. Evaluation of the rRNA by polyacrylamide/agarose electrophoresis disclosed two 28 S rRNA-derived fragments which differed in size from those generated by untreated (control) ribosomes. Sequencing of the smaller of these fragments confirmed that - as is the case for ricin A-chain - the aniline-sensitive site in barley toxin-treated ribosomes was between A and G in 28 S rRNA. We conclude that barley toxin inactivates ribosomes via a mechanism identical to that of ricin A-chain: enzymatic hydrolysis of the N-glycosidic bond at A of 28 S rRNA.

Animals↗
PubMed1988

The production of active human thyroid-stimulating hormone from alpha and beta mRNAs in Xenopus laevis oocytes.

Active human thyroid-stimulating hormone (hTSH) was produced by Xenopus laevis oocytes following injection of an mRNA mixture of hTSH beta and alpha subunits synthesized by T3 RNA polymerase. Some of the hTSH molecules were secreted into the medium, while others remained in the cells. The active molecules consisted of alpha and beta subunits and were in highly glycosylated form. The Xenopus laevis oocyte-produced hTSH stimulated the rat thyroid cell line FRTL-5 to produce and secrete the cyclic AMP as does authentic hTSH.

Animals↗
PubMed1988

The site of action of the A-chain of mistletoe lectin I on eukaryotic ribosomes. The RNA N-glycosidase activity of the protein.

The site of action of the A-chain of mistletoe lectin (ML-A) from Viscum album on eukaryotic ribosomes was studied. Treatment of rat liver ribosomes with ML-A, followed by treatment of the isolated rRNA with aniline, caused the release of a fragment with about 450 nucleotides from 28 S rRNA. Further analysis of nucleotide sequences of this fragment revealed that the aniline-sensitive site of phosphodiester bond was between positions A-4324 and G-4325 in 28 S rRNA. These results indicate that ML-A inactivates the ribosomes by cleaving a N-glycosidic bond at A-4324 of 28 S rRNA in the ribosomes as ricin A-chain does.

Animals↗
PubMed1988

The site of action of six different ribosome-inactivating proteins from plants on eukaryotic ribosomes: the RNA N-glycosidase activity of the proteins.

The site of action of six different ribosome-inactivating proteins from plants on eukaryotic ribosomes was studied. Treatment of ribosomes with any one of these proteins caused the 28S rRNA extracted from the inactivated ribosomes to become sensitive to treatment with aniline. A fragment containing about 450 nucleotides was released from the 28S rRNA. Further analysis of the nucleotide sequences of the 450-nucleotide fragments revealed that the aniline-sensitive phosphodiester bond was between A-4324 and G-4325 of the 28S rRNA. These results indicate that all six ribosome-inactivating proteins damage eukaryotic ribosomes by cleaving the N-glycosidic bond at A-4324 of the 28S rRNA of the ribosomes, as does ricin A-chain.

Aniline Compounds↗
PubMed1988

Site of action of a Vero toxin (VT2) from Escherichia coli O157:H7 and of Shiga toxin on eukaryotic ribosomes. RNA N-glycosidase activity of the toxins.

The site of action of a Vero toxin (VT2 or Shiga-like toxin II) from enterohemorrhagic Escherichia coli and Shiga toxin from Shigella dysenteriae 1 on eukaryotic ribosomes was studied. Treatment of eukaryotic ribosomes with either toxin caused the release of a fragment of 400 nucleotides from 28S ribosomal RNA when the isolated ribosomal RNA was treated with aniline. Release of this fragment with aniline treatment was accompanied by inhibition of protein synthesis and of elongation-factor-1-dependent aminoacyl-tRNA binding to ribosomes. Analysis of the nucleotide sequence of the 3'-terminal fragment of 553 nucleotides of 28S rRNA of rat liver 60S ribosomal subunits suggested that an adenine base at position 4324 (A-4324) was absent in toxin-treated 28S rRNA. Further analysis by thin-layer chromatography demonstrated quantitative release of adenine from rat liver ribosomes on treatment with the toxins. These results indicate that both VT2 and Shiga toxin inactivate 60S ribosomal subunits by cleaving the N-glycosidic bond at A-4324 in 28S ribosomal RNA.

Animals↗
PubMed1988

The juxtaglomerular apparatus in IgA nephropathy: an analysis of the transport and fate of IgA deposits at the glomerular hilus.

This study on 27 cases of IgA nephropathy has shown that IgA deposits are rare in the juxtaglomerular apparatus (JGA) despite large amounts of IgA deposits in the mesangium. Phagocytes are absent in JGA. A small number of ill-defined, IgA-positive substances are seen in the matrix of lacis cells, and their electron-density is decreased. These findings indicate dissolution of IgA deposits in the intercellular matrix. In addition, it is suggested that the transport of IgA deposits through the glomerular stalk toward JGA is prevented at the border area between the mesangium of glomerular hilus and the lacis cell region. The block is not complete, because small, IgA-positive substances are seen sparsely in the matrix of lacis cells. The structure of the lacis cell region is thought to restrict the passage of macromolecules such as IgA deposits. Frequently positive staining for C3 in the mesangium and lacis cell region and within the wall of afferent and efferent arterioles indicates that C3 is easily accessible to the arteriolar wall adjacent to JGA, by the route through the glomerular stalk and JGA. This may be concerned in the pathogenesis of arteriolar hyalinosis at the glomerular hilus.

Adolescent↗
PubMed1988

Characterization of an islet-activating protein-sensitive site in mouse sperm that is involved in the zona pellucida-induced acrosome reaction.

Recently, it has been suggested that a mouse sperm-associated protein with properties similar to the inhibitory guanine nucleotide-binding regulatory protein Gi plays an intermediary role in the zona pellucida-induced acrosome reaction (Endo, Y., Lee, M. A., and Kopf, G. S. 1987. Dev. Biol. 119, 210-216). In the present study experiments were designed to characterize further the role of this Gi-like protein in mediating this physiological event. Sperm capacitated in the presence of islet-activating protein (IAP) were inhibited from undergoing the acrosome reaction induced by either solubilized zonae pellucidae or purified ZP3. This inhibitory effect was observed with IAP concentrations previously shown to ADP-ribosylate the alpha-subunit of the Gi-like protein and inhibit the acrosome reaction induced by mechanically isolated, structurally intact zonae pellucidae. Inhibition occurred as a consequence of the inability of the sperm to progress from a capacitated, acrosome-intact state (B pattern) to an intermediate stage prior to the completion of the acrosome reaction (S pattern), as assessed with a chlortetracycline fluorescence assay. These inhibitory effects of IAP on the sperm acrosome reaction were confirmed by electron microscopy. In contrast, the acrosome reaction induced either spontaneously or nonspecifically by A-23187 was completely insensitive to IAP. Since the inhibitory effects of IAP on the acrosome reaction were at the level of the B to S transition, a transition normally accompanied by a loss in a transmembrane pH gradient, the effects of IAP on the loss of this gradient was assessed with the pH-sensitive fluorescent probe, 9-amino-3-chloro-7-methoxyacridine. The IAP-induced inhibition of the B to S transition was accompanied by a parallel retention of the transmembrane pH gradient. 3-Quinuclidinyl benzilate (QNB), a muscarinic cholinergic antagonist which has been demonstrated to specifically inhibit the zona-induced acrosome reaction at the B to S transition, also prevented the loss of this transmembrane pH gradient. The similarity of the effects of both IAP and QNB on sperm-zona interactions suggested that the IAP- and QNB-sensitive sites were either closely related or identical. Experiments designed to test these possibilities suggested that both sites were not identical. Finally, it was demonstrated that the acceleration of the zona-induced B to S transition observed with biologically active phorbol esters was insensitive to IAP, suggesting that the site of phorbol ester action is downstream from or independent of the IAP-sensitive site.(ABSTRACT TRUNCATED AT 400 WORDS)

Acrosome↗
PubMed1988

The metabolism of ribosomal proteins microinjected into the oocytes of Xenopus laevis.

When the total proteins from Xenopus laevis 60 S ribosomal subunits (TP60) were 3H-labeled in vitro and injected back into X. laevis oocytes, most 3H-TP60 are integrated into the cytoplasmic 60 S subunits via the nucleus during 16 h of incubation. In the oocytes whose rRNA synthesis is inhibited, 3H-TP60 are rapidly degraded with a half-life of 2-3 h. This degradation ceased as soon as rRNA synthesis was resumed, suggesting that ribosomal proteins unassociated with nascent rRNA are unstable in the oocytes. The degradation of 3H-TP60 in the absence of RNA synthesis was inhibited by iodoacetamide, a cysteine protease inhibitor, resulting in the accumulation of 3H-TP60 in the nucleus reaching about a threefold concentration in the cytoplasm. Considering the results with enucleated oocytes, we suggest that the X. laevis nucleus has a limited capacity to accumulate ribosomal proteins in an active manner but that those ribosomal proteins accumulated in excess over rRNA synthesis are degraded by a cysteine protease in the nucleus. By contrast, ribosomal proteins from Escherichia coli only equilibrate between the nucleus and the cytoplasm and are degraded by serine protease(s) in the cytoplasm without being integrated in the form of ribosomes in the nucleus.

Animals↗
PubMed1988

Analysis of cytoplasmic factors in developmental cleavage of mouse embryo.

One-cell embryos from certain mouse strains were found incapable of developing beyond the 2-cell stage in vitro (2-cell block), but a microinjection of EDTA effectively overcame this block. When 2-cell arrested embryos were fused with embryos that had developed to the late 2-cell stage in vivo, the fusants developed beyond the 2-cell stage. Microinjection of cytoplasm of in vivo 2-cell embryos into 1-cell embryos also obviated the 2-cell block. Analyses of 35S-labeled embryos by 2-dimensional polyacrylamide gel electrophoresis indicated changes in synthetic protein patterns possibly related to this block.

Animals↗
PubMed1988

A receptor model for tumor promoters: rational superposition of teleocidins and phorbol esters.

Four 12-O-tetradecanoyl-13-O-acetylphorbol-type tumor promoters--teleocidin, phorbol ester, aplysiatoxin, and ingenol ester--are superposed in an attempt to understand their common biological activity on the assumption that they may bind to the same receptor site. A method using three-dimensional computer graphics was applied for superposing molecules and receptor mapping. The main feature of the method is that molecules are superposed in terms of spatial arrangement of physical and chemical properties but not in terms of the atomic positions as in conventional methods. This led to successful extraction of common structural features required for potent tumor-promoting activity: two hydrogen donors, a hydrogen acceptor, and a large lipophilic group. Their mutual spatial arrangements are most important for biological activity.

Caenorhabditis elegans Proteins↗
PubMed1988

Hepatic squamous cell carcinoma with hypercalcemia in liver cirrhosis.

Primary squamous cell carcinoma of the liver is exceedingly rare and has previously been reported in association with hepatic teratoma, hepatic cyst or hepatolithiasis. This paper describes an autopsy case of squamous cell carcinoma which developed with hypercalcemia in a cirrhotic liver. This cancer was characterized histologically, immunohistologically and ultrastructurally, and was found to exhibit immunofluorescence positivity for anti-epidermal keratin monoclonal antibody, together with the presence of tonofilaments scattered sparsely in the cytoplasm of the cancer cells.

Antibodies, Monoclonal↗
PubMed1988

Urinary iodide excretion measured with an iodide-selective ion electrode: studies on normal subjects of varying ages and patients with thyroid diseases.

As a part of studies concerning clinical application of the measurement of urinary iodide with an iodide-selective ion electrode, we report here the reference values for the iodide content or concentration in morning spot urine specimens from normal subjects of varying ages and studies with patients with thyroid diseases in Japan. The number distribution of the iodide content or concentration in the morning specimens appeared logarithmic normal in adults, children and infants. Normal ranges found in 95 per cent of populations of healthy subjects were 5.3 to 62.0 mumoles/g Creatinine (Cr) for adults, 5.3 to 42 mumoles/g Cr for children, and 1.9 to 56 microM for infants, respectively. Urinary iodide concentrations in breast-fed infants varied widely compared with those in bottle-fed infants. Mean values were 16.4 microM for breast-fed infants and 8.6 microM for bottle-fed infants, and they were not statistically different. Urine samples from the infants with transient hypothyroidism, who had undergone amniofetography showed extraordinarily high iodide concentrations, even though they were measured at 20th, 29th and 30th days after birth. Although urinary iodide excretion in patients with simple goiter was within normal limits, the mean was statistically lower than that in normal controls (p less than 0.001). Because of the simplicity and rapidity of the electrode method, we strongly recommend it for use in examining iodide excretion in patients with various thyroid diseases.

Adolescent↗
PubMed1988

Serum free thyrotropin subunit in congenital isolated thyrotropin deficiency.

In two patients with congenital isolated thyrotropin (TSH) deficiency, serum TSH determined by a sensitive immunoradiometric assay (IRMA) was consistently undetectable. The basal levels of serum free TSH-alpha subunit (TSH-alpha) determined by a specific radioimmunoassay (RIA) were elevated in the hypothyroid state, and decreased to the undectable level during displacement therapy with thyroid hormone. The serum free TSH-alpha significantly increased following intravenous administration of thyrotropin releasing hormone (TRH). Serum free TSH-beta subunit (TSH-beta) was undectable. These findings suggest that TSH deficiency in this disease is not due to absence of thyrotroph in the pituitary gland or deficiency of TSH-alpha, but to abnormalities of the TSH-beta gene.

Adult↗
PubMed1988

A new bleeding tendency due to hereditary hyper alpha 2-macroglobulinemia.

A heritable elevation in alpha 2-macroglobulin (alpha 2M) was identified in a 9-year-old girl with a severe bleeding tendency and activated partial thromboplastin time (APTT) prolonged to 49.1 sec (normal 27-38) as well as recalcification time prolonged to 438 sec (less than 180). The addition of her plasma to normal plasma made APTT prolong from 26.8 to 38.3 sec. The plasma alpha 2M levels in her relatives were checked, i.e., proband, her sister, mother, maternal grandmother, father, and paternal grandmother: Their levels were 406, 380, 352, 339, 166 and 236 mg/100 ml (140-285), respectively. Thus the patient's condition was thought to be an autosomal dominant disease, though her other relatives displayed no apparent clinical symptoms. Of significance was that a possible causal association between her elevated alpha 2M and her prolonged APTT was indicated. The activity of the alpha 2M, determined as trypsin-protein esterase, was 351 mg/100 ml (197%). The alpha 2M also demonstrated normal horizontal mobility to anti-alpha 2M plasma with a high precipitin arc (showing the difference of the protein concentration) by crossed immunoelectrophoresis, and a normal horizontal mobility of immunofixation electrophoresis. In addition, after analysis of testing done by SDS-polyacrylamide-gel-electrophoresis, we found no qualitative abnormality in the alpha 2M of the patient.

Blood Coagulation Disorders↗
PubMed1988

Exocytotic release of neurotransmitter substances from nerve endings in the taste buds of rat circumvallate papillae.

Exocytotic release of neurotransmitters from nerve endings was demonstrated ultrastructurally in the taste buds of rat circumvallate papillae by stimulation of high K+ and Ca2+ Ringer perfusion and application of tannic acid-Ringer incubation (TARI) method. Omega-shaped images of large cored vesicles and small clear vesicles, indicating exocytotic release of their contents, were found only in the non-synaptic sites. Occasionally exocytosis occurred at sites facing other nerve fibers. Many coated pits were also seen, which presumably represent membrane retrieval at a later stage of exocytosis. It is likely that the taste buds receive more than one type of innervation.

Animals↗