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Biomedical subjects

T E Webb

Publications and source records attributed to T E Webb.

At least 91 records · Page 5Linked to original sources
PubMed1983

Characterization of a messenger RNA transport protein.

A cytoplasmic protein which facilitates the energy-dependent transport of mRNA from isolated nuclei to a specified medium has been further characterized, since it could have relevance to the mechanism of mRNA nucleo-cytoplasmic transport in vivo. This protein is now shown, by cDNA hybridization analysis using appropriate recombinant probes, to be obligatory for the transport of alpha 2u-globulin and albumin mRNA from male rat liver nuclei. It is concentrated in the cytoplasm. When isolated under conditions where they retain nuclear proteins, the nuclei contain less than 2% of the total mRNA transport activity. Approx. 20% is recovered in the cytosol, while the rest (80%) copurifies with the messenger ribonucleoproteins in the polyribosome fraction. The protein is eluted from the poly A-messenger ribonucleoproteins between 0.25 and 0.50 M NaCl. The activities of the cytosolic- and messenger ribonucleoprotein-derived transport proteins were mutually additive below saturation of the transport system. Further, the activities of both fractions were increased when they were fortified with the catalytic subunit of the cAMP-dependent protein kinase in the presence of ATP. On the other hand, protein kinase-induced thiophosphorylation of the protein with ATP[S] decreased transport activity. The molecular weight of the transport protein from either cell compartment as judged by molecular sieving is approx. 35,000. It has now been purified 2000-fold and requires manganese ions and serum albumin for stabilization of activity. The highly purified transport factor from the cytosol is tentatively assigned a molecular weight of 32,000 by SDS-polyacrylamide gel electrophoresis.

Alpha-Globulins↗
PubMed1983

Messenger RNA populations and their nuclear precursors in cultured human glioma and fetal brain cells.

Using labelled single copy DNA to cytoplasmic messenger RNA from a glioma cell line, it is shown by the excess RNA hybridization technique that a human glioma and a human fetal brain cell line both contain the mid and low abundancy classes of cytoplasmic messenger RNA. However, the high abundancy class present in the glioma cells is absent from the hybridization profile of the fetal cell line. Most of the nuclear RNA species complementary to this single copy DNA were present in the low abundancy class of both cell types; the mid-abundancy class was present in much lower concentration than in glioma cytoplasmic RNA and the high abundancy class was essentially absent. The extent of formation of S1-nuclease resistant hybrids indicated that some of the messengers which are present in the high abundancy class in the cytoplasm of glioma cells are present in the lower abundancy classes of fetal brain cells. Thus the glioma cells appear to exhibit a higher degree of specialization potential than the embryonic cells.

Aged↗
PubMed1983

Effect of physiological concentrations of insulin and antidiabetic drugs on RNA release from isolated liver nuclei.

The addition of 10(-11) M insulin to a cell-free system from rat liver promotes the release of messengerlike RNA from isolated prelabeled nuclei. The stimulation was similar whether the nuclei were preincubated with insulin, or if insulin was added directly to the cell-free system with or without a protease inhibitor. Dot blot hybridization using cloned cDNA for alpha 2u-globulin mRNA showed that this was one of the messages whose release was enhanced by insulin. Nuclei isolated from rats treated with either of the antidiabetics tolbutamide or tolazamide showed no increase in RNA release in the presence of insulin over the concentration range 10(-5) - 10(-14) M. Furthermore, these nuclei did not release detectable levels of alpha 2u-globulin mRNA.

Animals↗
PubMed1983

An oncofetal 60-kilodalton protein in the plasma of tumor-bearing and carcinogen-treated rats.

A Mr 60,000 protein, detected by its ability to induce the release of RNA from isolated nuclei, is present in the plasma of tumor-bearing and carcinogen-treated rats, together with low amounts of 2 messenger RNA transport proteins identified earlier in normal cells. The Mr 60,000 protein has been identified in tumor cell cytoplasm and in amniotic fluid, but does not appear to cross the placental barrier. Significant amounts of the Mr 60,000 oncofetal protein appear in the plasma of carcinogen-treated rats within a few weeks of treatment. It may be the fetal form of the adult messenger RNA transport proteins.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1983

Organ and species specificity of the messenger RNA transport factor.

The transport of messenger RNA from isolated rat liver nuclei is dependent on a 35,000 dalton protein localized in the cytoplasm. The tissue and species specificity of this protein are reported. The factor from female rat liver or from rat brain, kidney, or hepatoma supports the transport of messenger RNA from male rat liver nuclei. Messenger RNA is also transported in response to the factor from beef and chicken liver. The cytosols from rat erythrocytes, amoeba and yeast were inactive in the rat liver system. The results indicate that the messenger RNA transport factor is not specific for the nucleotide sequence of the coding portion of the messenger RNA and that it is not organ or species specific within the vertebrates.

Amoeba↗
PubMed1983

Concurrent changes in growth-related biochemical parameters during regression of hormone-dependent rat mammary tumors.

The in vivo relationship was studied between these biochemical parameters which previous studies have separately implicated in the regression of hormone-dependent rat mammary tumors. Upon depletion of estrogen and suppression of prolactin levels by ovariectomy, there was a marked increase in the production of prostaglandin E2 (PGE2)(fourfold) and in the cyclic AMP (cAMP) content (twofold) in the regressing 7,12-dimethylbenz[a]anthracene-induced primary tumors. These two parameters appeared to be coupled since, in addition to this correlation, PGE2 stimulated adenylate cyclase and raised cAMP levels in both this primary tumor system and in another hormone-dependent transplantable rat mammary tumor (MTW9-A). Furthermore both the sensitivity of the adenylate cyclase system to PGE2 and the number of membrane binding sites for PGE2 increased upon induction of regression in these tumors. Under conditions where PGE2 and cAMP were elevated, (i.e., in regressing, but not growing, hormone-dependent mammary tumors), there was significant phosphorylation in the intact tissue of a 75,000-dalton nuclear protein, which appeared to be identical to the regression-associated protein shown by Cho-Chung and co-workers to undergo increased phosphorylation in response to elevated cAMP levels.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1982

Relationship of iron status to urinary norepinephrine excretion in children 7-12 years of age.

In a group of 7- to 12-year-old children without manifest clinical iron deficiency, urinary excretion of free norepinephrine was found to have substantial positive correlation with measure of total iron-binding capacity and negative correlation with serum ferritin. Results support earlier reports of an inverse contingency between iron status and urinary norepinephrine level as observed with severe iron lack, findings consistent with speculation that monoamine oxidase activity may be modified by iron availability.

Anemia, Hypochromic↗
PubMed1981

Transport of functional messenger RNA from liver nuclei in a reconstituted cell-free system.

The reliability of a reconstituted cell-free system for messenger RNA processing and transport, consisting of isolated nuclei in fortified cytosol, has been evaluated in terms of the functionality and regulated release of the transported product. The poly(A) messenger RNA transport in vitro formed appropriate initiation complexes with ribosomes in an optimized translation system and had template activity comparable to that transported in vivo. The intra-nuclear origin of this messenger RNA is supported by pulse-labeling studies, its transport from detergent-treated nuclei and the absence of the release under non-transport conditions. Serum albumin was identified by immunoprecipitation and electrophoresis as one of the products synthesized when the transported RNA was translated in vitro. The transport of messenger RNA in the cell-free system was dependent on specific cytosol (soluble cytoplasmic) proteins. These proteins, which constitutes less than 0.1% of the total cytosol proteins, are precipitated wtih streptomycin with high specificity.

Animals↗
PubMed1981

Regulated transport of messenger ribonucleic acid from isolated liver nuclei by nucleic acid binding proteins.

Rat liver nucleocytosolic messenger ribonucleic acid (mRNA) transport is shown to be regulated by proteins with a high affinity for nucleic acids. In the cell-free system described, the energy-dependent transport of all RNA classes [transfer RNA (tRNA), mRNA, and ribosomal RNA (rRNA)] exhibited a dependence upon the availability of discrete minor sets of cytosol proteins. In addition to having a different level of saturation, only the mRNA "transport protein" activities are increased by adenosine cyclic 3',5'-phosphate (cAMP), an effect most likely mediated by a cAMP-dependent protein kinase. The mRNA transport proteins were isolated from cytosol by precipitation with streptomycin sulfate followed by deoxyribonucleic acid (DNA)-cellulose affinity chromatography, or from oligo-(thymidylate)-cellulose bound cytoplasmic messenger ribonucleoprotein (mRNP) particles by high-salt extraction. Either method yielded a protein fraction which exhibited a 1000-fold increase in mRNA transport activity as compared to cytosol. Over one-half of the mRNA transport activity is associated with the mRNP of the cell. A partial homology between the cytosol and mRNP-derived proteins was demonstrated by polyacrylamide gel electrophoresis. One major (20 000 daltons) and several minor proteins (23 000, 52 000, 54 000, and 72 000 daltons) were in common. Nuclear 4-5S exited from in vitro incubated nuclei in three phases, according to their differential in vivo rates of labeling and intranuclear pool sizes. The amount of nuclear RNA transported in vitro as mRNA (about 1.0%) agrees wtih the in vivo estimates. Additional evidence for in vivo equivalence was provided by the physicochemical characterization and bioassay of the RNA. The transported mRNA sedimented in urea-sucrose gradients as an 8-18S heterodisperse product. This RNA initiated cell-free translation with the synthesis of precursor peptides as diverse in size as those for albumin and alpha 2U-globulin. The relative abundancies of various transported mRNAs were different than the corresponding abundancies of liver cytoplasmic mRNAs.

Animals↗
PubMed1981

Continuities in the structural expression of affectivity: a developmental comparison.

Developmental trends in children's verbalization of affective distress is examined using the Structured Pediatric Psychosocial Interview. Scale scores for two independent samples of younger (7-10 yrs) and older (11-14 yrs) public school children were factor analyzed. Results show high degree of congruency between the two developmental groups in their verbalization of affectivity. Factors associated with effective hostility (Resentment and Detachment) and with goal-directed investment (Emulation and Apathy) show marked continuity across developmental stages. However, a factor related to description of internal arousal (Tension, Restlessness, Sensitivity) showed increased complexity with age.

Adolescent↗
PubMed1981

Binocular pattern stabilization by afterimage technique: reliability of children's time-dependent judgments of chromatic features.

To investigate visual afterimage technique as a means of producing retinally stabilized pattern, children's judgments of time-dependent shifts in chromatic appearance of random-dot configurations were twice examined within a 3-wk. interval. 13 subjects, aged 7 to 12 yr., were very consistent (r = .93) in their test-retest response times. This supports the belief that after image procedures can be developed as a reliable means of studying developmental aspects of stabilized pattern perception.

Child↗
PubMed1980

Glucocorticoid receptors in human tumors.

Glucocorticoid receptors were examined in a range of solid human tumors. In addition to breast carcinomas, subsets of other tumor types (notably renal cell carcinomas) contain concentrations of these receptors characteristic of glucocorticoid-responsive tissues. The physico-chemical properties of the single glucocorticoid receptor present in the human tumors resembled those of the glucocorticoid receptor in rat tumors and the predominant form found in normal target tissues of the rat.

Animals↗