[en] Plumbous ion has been shown to be a potent catalyst for the depolymerization of RNA in vitro but the question of whether or not Lead-catalyzed RNA degradation also occurs in vivo has never been addressed. Our experimental design, to answer this question, was to transfuse rabbit reticulocytes into normal rabbits and rabbits that had been injected with different doses of lead acetate. After 24 hours the mRNA was isolated form the reticulocytes of each rabbit by phenol extraction and affinity chromatography on oligo dT cellulose. The amount of mRNA per ml of packed reticulocytes was determined. The integrity of the mRNA was then determined with a cell-free reticulocyte translation system that was dependent on exogenous mRNA. The results showed that there was little difference in the amount of mRNA recovered from control and treated rabbits, but the ability of the mRNA to support globin synthesis was decreased by as much as 86% in the lead-treated rabbits. These data suggest that not only is mRNA attacked by lead in vivo but that the lead attacks the mRNA at just one or at least very few sites. In the in vivo studies, purified rabbit globin mRNA was incubated with lead acetate and the products of this reaction were labelled with ³²P using T4 polynucleotide kinase. A labelled fragment of slightly greater mobility than tRNA was isolated by gel electrophoresis. This fragment was digested to the monomers and analyzed by TLC to identify the nucleotide at the 5' end

[en] Prolonged exposure to estradiol 17-β (E₂) in rats has been shown to decrease dopamine (DA) synthesis in and release from tuberoinfundibular dopaminergic (TIDA) neurons in Fischer 344 rats. The objective of the present study was to determine whether inhibition of the E₂-induced increase in anterior pituitary (AP) weight and prolactin (PRL) secretion by concomitant administration of the dopaminergic agonist, bromocryptine, could prevent the decrease in TIDA neuronal function produced by chronic E₂ administration. TIDA neuronal function was evaluated by in vitro superfusion and electrical stimulation of median eminence (ME) tissue after allowing for accumulation of [³H] dopamine (DA). The effect of chronic E₂ and/or bromocryptine treatment on catecholamine content in tuberohypophyseal neurons in the neurointermediate lobe was also measured to determine whether increased pituitary size possibly damaged the tuberohypophyseal neurons

[en] Exposure of isolated rat gastric mucosal cells to 10^-10 and 10^-9 M gastrin for 2 hr significantly stimulated [³H] leucine incorporation into protein by 100 and 212%, respectively, when compared with the basal levels. Doses beyond 10^-9 M lowered the maximal stimulatory effect of the hormone. Gastrin (10^-9 M) specifically stimulated the synthesis of five proteins in isolated gastric mucosal cells with apparent molecular weights of 105, 76, 71, 63, and 54 kDa. Actinomycin-D completely abolished the gastrin-mediated stimulation of protein synthesis in isolated gastric mucosal cells

[en] Two commonly used cystoscopic infusion fluids were examined to determine whether their infusion stimulates DNA synthesis of the bladder epithelium. Following a single intravesical dose of 0.5 ml of distilled water or 1.5% L-glycine solution, rats were killed periodically up to 1 week. A transient but significant increase in epithelial cell [³H]thymidine labeling was observed at 48 hr after distilled water instillation. Glycine solution did not stimulate DNA synthesis

[en] The objective of this study is to examine and characterize epidermal growth factor receptor (EGF-R) binding in inhaled plutonium-induced canine lung-tumor tissue and to compare it with that in normal canine lung tissue. Crude membrane preparations from normal and lung-tumor tissue from beagle dogs were examined in a radioreceptor assay, using ¹²⁵I-labeled epidermal growth factor (EGF) as a ligand. Specific EGF receptor binding was determined in the presence of excess unlabeled EGF. We have examined EGF receptor binding in eight lung-tumor samples obtained from six dogs. Epidermal growth factor receptor binding was significantly greater in lung-tumor samples (31.38%) compared with that in normal lung tissue (3.76%). Scatchard plot analysis from the displacement assay revealed that there was no statistical difference in the binding affinity but significantly higher concentration of EGF-R sites in the lung-tumor tissue (619 fmol/mg) than in normal lung tissue (53 fmol/mg). The increase in EGF-R number in plutonium-induced dog lung tumors does not seem to correlate with increase in the initial lung burden exposure to plutonium. Our results demonstrate that there is a significant increase in EGF-R binding in inhaled plutonium-induced dog lung tumors

[en] The in vitro effect of bovine brain cortex phosphatidylserine on ³²Pi incorporation into phosphatidylinositol, phosphatidylcholine, and phosphatidylethanolamine of rat anterior pituitary glands was studied. Phosphatidylserine (0.1 to 66.6 microM) decreased the incorporation of ³²Pi into phosphatidylinositol, but not phosphatidylcholine or phosphatidylethanolamine, in a concentration-related manner. The inhibitory effect of phosphatidylinositol was similar to that of dopamine in the same experimental conditions. The combined effects of submaximal concentrations of dopamine and phosphatidylserine elicited an apparently additive inhibitory effect on phosphatidylinositol synthesis. The inhibitory effect of phosphatidylserine was completely reversed by haloperidol and sulpiride and only partially by pimozide, antidopaminergic agents which per se do not affect phosphatidylinositol synthesis. The stimulatory effect of TRH to increase ³²Pi incorporation into phosphatidylinositol was decreased by phosphatidylserine. These observations suggest that the decrease in prolactin release in the presence of phosphatidylserine may be evoked through a dopaminergic mechanism

[en] The composition and structure of the complex oligosaccharides of thyrotropin (TSH) and free alpha-subunits are not well established, but are believed to be important determinants of the biological properties of these glycoproteins. We employed a simple double-label technique to learn the relative fucose content of mouse thyrotropin and free alpha-subunits. Thyrotropic tumor minces were incubated simultaneously with [³⁵S]methionine and [³H]fucose. Thyrotropin and free alpha-subunits were labeled with both isotopes, and the ratio of ³H/³⁵S was higher in free alpha-subunits than in thyrotropin; free alpha-subunits were approximately fivefold richer in fucose than was thyrotropin. The ³H/³⁵S ratio was not substantially altered in TSH or free alpha-subunits secreted after a brief incubation with 10(-7) M thyrotropin-releasing hormone. Species which incorporated [³H]fucose were resistant to endoglycosidase H. Thus, mouse free alpha-subunits secreted by thyrotropic tumor are relatively rich in fucose. Double-isotope labeling using an amino acid and a sugar appears to be a useful technique for studies of the glycoprotein hormones

[en] Two groups of rats, (N = 7), were fasted for 24 hrs prior to the study. On the day of the experiment, the animals were anesthetized and infused with either 5 ml nicotine solution (200 μg/L) in saline containing 5 μc ³H-nicotine, (sp. activity 50-80 mCi/mol) for 90 minutes or injected as a bolus with 0.5 ml of the same nicotine (200 μg/L) solution. The animals were sacrificed 60 minutes after the injection or after the infusion was stopped. Blood and tissue samples were counted by liquid scintillation counting. Percent distribution of ³H-nicotine per gm of tissue was calculated from the total radioactivity recovered in individual tissues over the total activity injected into the rat and the values were compared using student's t test. Results: Distribution of ³H-nicotine was found highest in kidney (45-49%) among all tissues examined and was not different between routes of administration. Significantly higher retention of ³H-nicotine was found with continuous infusion in esophagus, fundus, antrum, spleen, cecum, pancreas, testes, heart and muscle when ³H-nicotine retentions were compared with bolus injection. In contrast, the distribution of ³H-nicotine in adrenal gland, was significantly lower in continuous infusion group. Distribution in blood was 6 fold higher in continuous infusion (7.26%) compared to bolus (1.11%) injection. The distribution ³H-nicotine in other tissues were not different by either routes of injection

[en] Immature, ovariectomized, estrogen-primed rats respond to the administration of porcine relaxin by an increase in the incorporation of labeled amino acids ([¹⁴C]leucine, [¹⁴C]phenylalanine, [³H]proline) into uterine proteins in vitro. The maximum response occurs about 12 hr after a single injection of 0.1 mg relaxin in benzopurpurine 4B solution; subsequently, the relaxin effect declines but is still apparent after 24 hr. Smaller, but still significant increases in incorporation rates can be induced by relaxin in the absence of estrogen priming. Uterine collagen synthesis, as indicated by the incorporation of [³H]proline and its conversion to hydroxyproline, appears to be a primary target of the relaxin stimulus, since the effect of relaxin upon proline incorporation into uterine collagen is significantly greater than its effect upon labeling of noncollagen protein

[en] Prolonged exposures to technical grade dinitrotoluene (DNT), a mixture of isomers used in the manufacture of several commercial products, may cause atherosclerotic heart disease in humans. However, the cellular/molecular basis the DNT-induced atherogenesis has not been investigated. As increased smooth muscle cell (SMC) proliferation is observed during the initial stages of atherosclerosis, the present studies were conducted to evaluate the proliferative capability of cultured SMC obtained from rats treated with two predominant isomers of technical grade DNT. Sprague-Dawley rats were treated for 8 weeks with 2,4- or 2,6-DNT (0.5, 5 or 10 mg/kg) or saline. The extent of ³H-thymidine incorporation into DNA was used as an index of cell proliferation. Additional studies were conducted to determine if 2,4- or 2,6-DNT was toxic to SMC in vitro as measured by lactate dehydrogenase (LDH) release and cell glutathione content. The extent of ³H-thymidine incorporation was 270% and 148% higher in SMC obtained from 5 and 10 mg/kg 2,4-DNT, respectively, than cells obtained from control animals. In contrast, SMC obtained from 2,6-DNT did not show an increase in ³H-thymidine incorporation at any of the doses tested. Acute exposure of cells to DNT (1-100 μM) in vitro did not cause measurable cell damage. Direct cytotoxic effects of 2,4-DNT on SMC may not account for the alterations in thymidine incorporation observed in cells obtained from DNT-treated animals. The sterospecific enhancement of vascular SMC proliferation following subchronic exposure to DNT in vivo supports the hypothesis that 2,4-DNT is atherogenic