Random surface dynamics for Z2 gauge theory.
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Journal Article↗
Biomedical subjects
S Huang
Publications and source records attributed to S Huang.
Two distinct and frequently mutated regions of retinoblastoma protein are required for binding to SV40 T antigen.
The retinoblastoma susceptibility gene (RB) encodes a phosphoprotein of 110 kd (pp110RB) that forms specific complexes with SV40 T antigen and the transforming proteins of several other DNA tumor viruses. Interaction with RB is thought to contribute to transformation by these viruses as demonstrated by genetic analyses. To help understand the function of these interactions, the regions of RB that are involved in binding to T have been mapped. An in vitro protein synthesis system capable of producing full-length RB protein has been developed to facilitate the mapping study. A 5- to 10-fold increase in translational efficiency in the reticulocyte lysate was obtained when the 5' non-coding region of RB mRNA was replaced with that of beta-globin mRNA or a plant viral RNA, alfalfa mosaic virus (AMV) RNA4. A series of mutated RB polypeptides produced from this system were assayed for T binding. Two non-contiguous regions of the RB protein, amino acid residues 394-571 and 649-773, were found to be necessary for binding to T: mutations in either region abolished T-RB complex formation. These results are consistent with the finding that, in all the cases analyzed so far, mutated RB proteins in human tumor cells also failed to bind to T antigen due to deletions including at least one of the two required regions. Thus the regions of RB defined in vitro as necessary for interaction with T might be physiologically relevant as well, and might play a fundamental role in normal RB protein function.
Antigens, Polyomavirus Transforming↗
Modulation of neural commitment by changes in target cell contacts in Pleurodeles waltl.
In amphibian development, neural structures arise from the presumptive ectoderm at the gastrula stage by an inductive interaction with the chordamesoderm. It has been previously reported that early gastrula presumptive ectoderm can be neuralized when it is dissociated into single cells. A similar result is reported here with regard to Pleurodeles waltl presumptive ectoderm. Using this experimental model system we demonstrate: first, that neuronal and glial lineages can be specified from the presumptive ectoderm without any intervention of the natural inducing tissue; and second, that whereas rupture of cell-cell contacts evoked neural induction, dissociation immediately followed by reaggregation reduces the neuralizing response, pointing toward an active role played by cell-cell contacts of presumptive ectodermal cells in the modulation of neural commitment.
Animals↗
Purification, characterization, and amino terminal sequence of xylose reductase from Candida shehatae.
D-Xylose is a major component of the carbohydrates derived from agricultural residues and forest products. Among more than two hundred known xylose-utilizing yeasts, only a few species are known to be able to ferment xylose anaerobically. Candida shehatae is one of such xylose-fermenting yeasts. Xylose reductase (E.C. 1.1.1.21) is a key enzyme responsible for xylose metabolism in xylose-utilizing as well as xylose-fermenting yeasts. In this paper, we report the development of a convenient and reliable procedure for the purification of xylose reductase from C. shehatae to near homogeneity. The amino acid composition and N-terminal sequence of the enzyme have also been analyzed. C. shehatae seems to contain only a single xylose reductase, but the enzyme has a dual coenzyme specificity for both NADPH and NADH. The enzyme is remarkably stable at room temperature and 4 degrees C.
Aldehyde Reductase↗
Isolation of characterization of two sequence-specific endonucleases from the cyanobacterium Synechocystis sp. PCC 6308.
The first two restriction endonucleases to be characterized in the cyanobacterium Synechocystis sp. PCC 6308 are described. SynI, an AvaII isoschizomer, recognizes the base sequence 5-GG[AT]CC-3. SynII, an XmnI isoschizomer, recognizes the sequence 5-GAANNNNTTC-3.
Base Sequence↗
Extracellular matrix: an immunological and biochemical (CAT and TOH activity) survey of in vitro differentiation of isolated amphibian neuroblasts.
After neural induction certain cells in the neuroepithelium immediately acquire the property to express certain neural phenotypes (Duprat et al., 1984, 1987). However, the activity of almost all the specific enzymes involved in the biosynthesis of neurotransmitters is considerably higher when neurectodermal cells are cultured with chordamesodermal cells than when they are cultured alone. The stimulating effects of chordamesoderm do not appear to be due to diffusible factors (Duprat et al., 1985b). The present study was designed to investigate the role of extracellular matrix components in neuronal cell differentiation. We showed that the extracellular matrix cannot replace chordamesoderm in stimulating the biochemical differentiation of neuroblasts, although fibronectin and especially laminin stimulate morphological differentiation. We suggest that interaction between neuronal and non-neuronal cells plays an important part in functional biochemical differentiation, whereas the molecules of extracellular matrix are important for morphological differentiation.
Animals↗
Evaluation of the equivocal test results of Treponema pallidum haemagglutination assay.
Two hundred and eighty Rapid Plasma Reagin (RPR) positive sera with an emphasis on cases with negative and borderline positive Treponema pallidum haemagglutination assay (TPHA) results were selected. Modified TPHA (M-TPHA) and fluorescent treponemal antibody absorption (FTA-abs) tests were used for comparison. One hundred and twenty five samples were TPHA negative, of which 78 and 69 cases were also negative by M-TPHA and FTA-abs, respectively. Eighty one sera negative by TPHA at a titre of 1/80 and positive at 1/40, considered to be negative according to the manufacturer's instructions, were also negative by M-TPHA (n = 11) and by FTA-abs (n = 1). Fifty borderline positive TPHA specimens gave one negative result by both M-TPHA and FTA-abs. The remaining 24 sera were positive by all three tests. Because of the high percentage of TPHA negative results among the positive RPR sera which became reactive when rechecked by the FTA-abs, it is concluded that as a confirmatory test the TPHA should be used not instead of but in addition to the FTA-abs.
Antibodies, Bacterial↗
Differential regulation of right and left ventricular beta-adrenergic receptors in newborn lambs with experimental cyanotic heart disease.
To determine whether chronic hypoxemia secondary to an intracardiac right-to-left shunt alters regulation of the myocardial beta-adrenergic receptor/adenylate cyclase system, we produced chronic hypoxemia in nine newborn lambs by creating right ventricular outflow obstruction and an atrial septal defect. Oxygen saturation was reduced to 65-74% for 2 wk. Eight lambs served as normoxemic controls. beta-receptor density (Bmax) and ligand affinity (KD) were determined with the radio-ligand [125I]iodocyanopindolol and adenylate cyclase activity determined during stimulation with isoproterenol, sodium fluoride (NaF), and forskolin. During chronic hypoxemia, Bmax decreased 45% (hypoxemic, 180.6 +/- 31.5 vs. control, 330.5 +/- 60.1 fmol/mg) in the left ventricle (exposed to hypoxemia alone) but was unchanged in the right ventricle (exposed to hypoxemia and pressure overload). KD was not different from control in either ventricle. Left ventricular isoproterenol-stimulated adenylate cyclase activity was decreased by 39% (30.0 +/- 4.3% increase vs. 44.1 +/- 9.5% increase) whereas right ventricular adenylate cyclase activity was unchanged. Stimulation of adenylate cyclase with NaF or forskolin was not different from control in either ventricle. Circulating epinephrine was increased fourfold whereas circulating and myocardial norepinephrine were unchanged. These data demonstrate a down-regulation of the left ventricular beta-adrenergic receptor/adenylate cyclase system during chronic hypoxemia secondary to an intracardiac right-to-left shunt.
Adenylyl Cyclases↗
Some characteristics of rat nigrostriatal dopaminergic neuroconnection during development--a combined immunocytochemical and electron-microscopic study.
The characteristics of the nigrostriatal dopaminergic neuroconnections in developing rats are studied by combined immunocytochemical and electron-microscopic techniques, with an antibody to tyrosine hydroxylase (TH). From the embryonic day 21 on, some of the TH-positive nerve fibers are densely packed in the striatum to form a patch-like dopamine island. The percentage of the TH-positive nerve terminals among the labeled profiles is much higher inside than outside the dopamine island (P less than 0.01). On the other hand, the TH-positive terminals mainly form symmetrical axon-dendritic synapses, while most of the TH-negative terminals form asymmetrical axon-spinous synapses. The functional significance of the characterized dopaminergic connection is discussed.
Animals↗
DNA-binding activity of retinoblastoma protein is intrinsic to its carboxyl-terminal region.
The retinoblastoma (RB) gene encodes a nuclear phosphoprotein with a molecular weight of 110,000 (pp110RB) associated with DNA-binding activity. This sequence-nonspecific DNA binding activity was further studied by Southwestern and DNA-cellulose chromatography using purified fusion proteins expressed in Escherichia coli. Three fusion proteins, containing amino acids 612-775, 776-928, and 612-928 of pp110RB, bound to DNA; the binding affinity of the latter was approximately 20-fold higher than those of either smaller region. Other regions of pp110RB had no detectable binding activity, indicating that the carboxyl-terminal region of the RB protein is the major domain responsible for interacting with DNA. Since several potential phosphorylation sites reside within this region, isoforms of RB protein from cellular lysates with various degrees of phosphorylation were compared with respect to their DNA-binding affinity. The hyperphosphorylated form was eluted from DNA-cellulose columns at 0.1-0.3 M NaCl, whereas the hypophosphorylated form appeared in the eluates only at salt concentrations of 0.4-0.7 M, implying that phosphorylation of RB protein may affect its DNA-binding activity. That pp110RB can bind DNA intrinsically, and that this activity can be modulated by phosphorylation, is consistent with the proposed regulatory role of the RB protein in cell growth and differentiation.
Blotting, Southern↗
The proportion of various types of congenital color vision defects.
One hundred and three color vision defective subjects were screened from 3456 middle school students with pseudoisochromatic plate test. One hundred subjects out of them were further examined with a test battery including Panel D-15 and FM 100-hue test and Neitz anomaloscope test. It was found that there were 21 protanopes (P), 3 extremely protanomalous (EPA), 13 protanomalous (PA), 25 deutenopes (D), 5 extremely deuteranomalous (EDA), 28 deuteranomalous (DA), 6 unclassified subjects in our investigation. The proportion of various types of congenital color vision defects was P:EPA:PA:D:EDA:DA = 1.00:0.14:0.62:1.19:0.24:1.33.
Adolescent↗
[Pathological study of 51 cases of cardiac tumors].
51 cases of cardiac tumors were studied pathologically, including light and electron microscopic observation. Among 47 cases of benign tumors, 46 were cardiac myxomas and one was leiomyoma. Among the remaining 4 cases of malignant cardiac tumors, there were two malignant myxomas, one lymphoma and one metastatic squamous epithelial cell cancer. Cardiac tumors might be grossly divided into three types: papillary, massive and lobular types, while the papillary type was most commonly seen. In this article, diagnosis of cardiac tumors, pathologic features of cardiac myxoma and pathohistological difference between tumor and organized thrombus are discussed.
Adolescent↗
From presumptive ectoderm to neural cells in an amphibian.
As an immediate consequence of neural induction during gastrulation, some neuroectodermal cells acquire the ability to develop a number of specific neuronal and astroglial features, without requiring subsequent chordamesodermal cues. Thus, cholinergic, dopaminergic, noradrenergic, gabaergic, somatostatinergic, enkephalinergic, etc. traits are expressed in cultures of neural plate and neural fold isolated from amphibian late gastrulae immediately after induction and cultured in a defined medium. These results strongly suggest that at the late gastrula stage, the neural precursor population does not yet constitute a homogeneous set of cells. It was of interest to know the origin of this heterogeneity. Is it a direct result of the process of neural induction itself, stochastic phenomena being involved or not at the cellular level, or does it reflect a pre-existing heterogeneity in the presumptive ectoderm? At the early gastrula state, presumptive ectoderm can be neuralized consecutively to its dissociation into single cells. Using this experimental model, we have demonstrated by means of immunological probes that neuralized presumptive ectodermal cells, without any intervention of the chordamesoderm (natural inducing tissue), can develop autonomously into glial and neuronal lineages. These data suggest the existence of diverse predispositions of presumptive ectodermal cells. Competent ectoderm seems to be a heterogeneous structure with cells presenting distinct neural predispositions that can emerge as a consequence of a permissive inductive signal without real specificity (such as a target tissue dissociation). Moreover, such a differentiated neuronal population includes neurons of the GABAergic and enkephalinergic phenotypes but not of the cholinergic, catecholaminergic, somatostatinergic, etc. phenotypes. These data show that the developmental program of ectodermal cells induced without interaction with the chordamesoderm appears restricted compared to the naturally induced ectoderm. Experiments are now under way to analyze such sequential neural events.
Amphibians↗
Metastases to both testicles from prostatic carcinoma six years after radiation therapy.
A case is presented of a sixty-nine-year-old man with metastases to both testicles and right epididymis six years after treatment with external beam radiation for Stage C prostatic carcinoma.
Adenocarcinoma↗
Germ-line transmission of a planned alteration made in a hypoxanthine phosphoribosyltransferase gene by homologous recombination in embryonic stem cells.
Embryonic stem cells (derived from 129/Ola mice) containing a mutant hypoxanthine phosphoribosyltransferase gene that had been corrected in vitro in a planned manner by homologous recombination were injected into blastocysts obtained from C57BL/6J mice. The injected blastocysts were introduced into pseudopregnant female mice to complete their development. Eleven surviving pups were obtained. Nine were chimeras: six males and three females. Two of the males transmitted the embryonic stem cell genome containing the alteration in the hypoxanthine phosphoribosyltransferase gene to their offspring at high frequencies. These experiments demonstrate that a preplanned alteration in a chosen gene can be made in the germ line of an experimental animal by homologous recombination in an embryonic stem cell.
Animals↗
Translational initiation factor expression and ribosomal protein gene expression are repressed coordinately but by different mechanisms in murine lymphosarcoma cells treated with glucocorticoids.
P1798 murine lymphosarcoma cells cease to proliferate upon exposure to 10(-7) M dexamethasone and exhibit a dramatic inhibition of rRNA and ribosomal protein synthesis (O. Meyuhas, E. Thompson, Jr., and R. P. Perry, Mol. Cell Biol. 7:2691-2699, 1987). These workers demonstrated that ribosomal protein synthesis is regulated primarily at the level of translation, since dexamethasone did not alter mRNA levels but shifted the mRNAs from active polysomes into inactive messenger ribonucleoproteins. We have examined the effects of dexamethasone on the biosynthesis of initiation factor proteins in the same cell line. The relative protein synthesis rates of eIF-4A and eIF-2 alpha were inhibited by about 70% by the hormone, a reduction comparable to that for ribosomal proteins. The mRNA levels of eIF-4A, eIF-4D, and eIF-2 alpha also were reduced by 60 to 70%, indicating that synthesis rates are proportional to mRNA concentrations. Analysis of polysome profiles showed that the average number of ribosomes per initiation factor polysome was only slightly reduced by dexamethasone, and little or no mRNA was present in messenger ribonucleoproteins. The results indicate that initiation factor gene expression is coordinately regulated with ribosomal protein synthesis but is controlled primarily by modulating mRNA levels rather than mRNA efficiency.
Animals↗
Chronotropic effect of the methanolic extracts of the plants of the Paris species and steroidal glycosides isolated from P. vietnamensis on spontaneous beating of myocardial cells.
Rhizomes of five identified plants of the Paris species, Liliaceae, and Rhizoma Paridis which are sold as a crude drug named "Zao Xiu," "Qiyeyizhihua" or other names in nine different markets in China were tested for their effects on cultured cardiomyocytes. In the standard medium, eight methanol extracts out of sixteen at a concentration of 0.2 mg/ml stopped the spontaneous beating of myocardial cell sheets, but these extracts significantly increased the beating rate when the concentration was reduced to one half. In the culture medium with a low calcium concentration, 0.5 mM, the beating rate of the cells decreased to about 60% of that of the control in the standard medium. The addition of five of the extracts to the low calcium medium at a concentration of 0.1 mg/ml caused a stop of cell beating, but the other extracts increased beating rate at least by 10%. These steroidal glycosides isolated from the rhyzomes of P. vietnamensis (Takht.) H. Li also stimulated cell beating. Among them, diosgenin-3)-alpha-L-rhamno-pyranosyl-(1---2)-(alpha-L-arabinofura nosyl-(1---4))-D-glucopranoside (compound 1) was the most effective stimulant for cell beating as well as calcium uptake by the myocardial cells.
Animals↗
[Complement-mediated solubilization of immune complexes in immune complex nephritis].
In order to examine the ability of complement to solubilize the immune complexes (IC) in vivo, we made acute or chronic serum sickness nephritis in 10 rabbits or 12 rats with injection of BSA as antigen (Ag). Animals were divided into two groups. The 500 mu or 50 mu/week of cobra venom factor (CVF) for rabbits or rats was administered intraperitoneally in one group of animals to reduce the serum complement levels and complement-mediated solubilization of immune complex. On the other hand, the 2 ml or 0.2 ml/week of turpentine oil (TO) was injected intramuscularly in another group of animals to elevate the serum complement levels. The renal biopsy was performed with weekly intervals in each animals, and the specimens were stained for antigen (BSA), antibody (IgG) and C3 by immunofluorescence techniques. The result in this experiments showed the significant difference between TO-, and CVF-treated animals in the degree of disappearance of IC in the kidney lesions. The undetectable amount of IC (especially BSA) was remained in the renal tissue of TO-treated animals. This fact indicated that complement might act to solubilize the IC deposited in the tissue in vivo also.
Animals↗