Determination of trace levels of fatty acid metal salts by high-performance liquid chromatography with fluorescence prelabeling

A simple method is described for picomole determinations of fatty acid metal salts. Fatty acid salts are directly labeled with 4-bromomethyl-7-methoxycoumarin in the presence of excess ethylenediaminetetraacetic acid tripotassium salt without any solvent extractions. The fluorescence derivatives of fatty acids are separated by reverse-phase high-performance liquid chromatography followed by fluorometric detection. The response of each fatty acid (C8-C18) calcium salt is linear from 1 to 50 micrograms/ml of samples. The detection limit is about 7 pmol. Good recoveries are obtained for the calcium salts of myrystic acid and soap (C8-C18, C18:1,2). The new method is successfully applied to the study on biodegradation of fatty acids in river water.     

Tactical Voting in Plurality Elections

How often will elections end in landslides? What is the probability for a head-to-head race? Analyzing ballot results from several large countries rather anomalous and yet unexplained distributions have been observed. We identify tactical voting as the driving ingredient for the anomalies and introduce a model to study its effect on plurality elections, characterized by the relative strength of the feedback from polls and the pairwise interaction between individuals in the society. With this model it becomes possible to explain the polarization of votes between two candidates, understand the small margin of victories frequently observed for different elections, and analyze the polls'' impact in American, Canadian, and Brazilian ballots. Moreover, the model reproduces, quantitatively, the distribution of votes obtained in the Brazilian mayor elections with two, three, and four candidates.     

Effect of adrenergic agonists and antagonists on alanine amino transferase,fructose-1:6-bisphosphatase and glucose production in hepatocytes

Using rat hepatocytes we confirmed our previous results that glucagon and -adrenergic agonists increased the enzyme activity of alanine aminotransferase (AAT) and propranolol abolished their effects. Only the enzyme activity was measured and other parameters like quantity of the enzyme or activation due to modification were not looked for. As in perfusion experiment phenylephrine and phenoxybenzamine (-agonist and -antagonist respectively) also increased the AAT activity in isolated rat hepatocytes and propranolol reversed these effects. The additive effect of glucagon and phenoxybenzamine on AAT was also persistant in hepatocyte system.Fructose- 1:6-bisphosphatase (Fru-P₂ase), another key enzyme in gluconeogenic pathway, was elevated by glucagon and other -adrenergic agonists both in liver perfusion and isolated hepatocyte experiments and was brought back to the normal level by propranolol. In this case also only the enzyme activity was measured and no other parameters were looked for. Unlike AAT this enzyme was not stimulated by phenylephrine or phenoxybenzamine. But AAT and Fru-P₂-ase activities were increased significantly by adenylate cyclase activators like fluoride or forskolin. Thus, it appears that the regulation of fru-P₂-ase by glucagon is purely a -receptor mediated process whereas AAT activation shows a mixed type of regulation where some well known -agonist and antagonists are behaving as -agonists.Results further indicate the presence of phosphodiesterase in hepatocyte membrane which was stimulated by glucagon and brought back to the normal level by propranolol.The different adrenergic compounds stated above, not only modified the activity of the above two enzymes but also stimulated glucose production by hepatocytes from alanine which was in turn abolished by propranolol as well as amino oxyacetate (AOA), a highly specified inhibitor of AAT. This confirm the participation of AAT in gluconeogenesis from alanine in liver. Forskolin and fluoride also increased the glucose production from alanine and showed additive effects with glucagon, phenylephrine and phenoxybenzamine.     

Effect of glucagon and some other alpha and beta adrenergic agonists and antagonists on alanine amino transferase of perfused rat liver

Summary Glucagon increased alanine amino transferase (AAT) activity in perfused rat liver by about 90% over control. Propranolol, the beta receptor antagonist, abolished the effect of glucagon on this enzyme. Well known beta receptor agonists like isoproterenol, norepinephrine and epinephrine also increased the enzyme activity under identical condition and the enhancement was similarly abolished by propranolol. These experiments suggest that the effect of glucagon on AAT was mediated through beta adrenergic receptor. However, the interesting observation was that phenylephrine, alpha receptor agonist and phenoxybenzamine and tolazoline, two alpha receptor antagonists, increased the AAT activity like glucagon in perfusion experiments and the effects of all these three agents were also abolished by propranolol. Glucagon, when perfused with phenoxybenzamine showed some additive effect. From all these results we are proposing that in our system phenoxybenzamine is acting as beta agonist although it is known to be an alpha antagonist.     

The finding of Enterobius vermicularis eggs in pre-Columbian human coprolites

Enterobius vermicularis eggs were found in human coprolites collected in the archaeological site of Caserones, Tarapaca Valley, Chile, dating from 400 BC to 800 AD. The human pinworm had already been found in other pre-historic archaeological sites in America, and its introduction in this continent is discussed.     

Biochemical parameters to assess cell differentiation of Bouvardia ternifolia Schlecht callus

Calli derived from leaves and radicles of B. ternifolia were grown on Murashige and Skoog (MS) basal medium, and the effects of different nitrogen sources on the rate of callus growth and on the enzymes related to nitrogen assimilation were studied. Ammonium alone did not support callus growth unless a Krebs-cycle intermediate was added to the medium. The activities of glutamine synthetase (EC 6.3.1.2), glutamate synthase (EC 1.4.7.1), and glutamate dehydrogenase (EC 1.4.1.2) were measured in homogenates of callus grown on media supplied with different nitrogen sources. The results indicate that leaf and root calli have similar levels of these enzymes when grown on MS medium (Murashige and Skoog 1962. Physiol. Plant. 15, 473–497). However, when the calli were supplied with glutamine as the sole nitrogen source, the activity of glutamate synthase increased in leaf callus but was almost completely inhibited in root callus. The results indicate that calli originated from different B. ternifolia tissues do not have the same biochemical dedifferentiated state.     

PGE2 involvement in experimental infection with Trypanosoma cruzi subpopulations

PGE₂ involvement in experimental Trypanosoma cruzi infection depends on the lethal capacity of the parasite subpopulation used. Mice acutely infected with non-lethal K98 displayed an enhancement in PGE₂ serum levels during the acute period, while those infected with lethal T. cruzi subpopulations (RA or K98-2) showed levels not different from normal mice. The enhancement detected in K98 group could be related both to an increased number of CD8+ T cell number and to enhanced PGE₂ release per cell by CD8+; values of PGE₂ release by adherent cells were not altered in this group. Treatment with cyclooxygenase inhibitors enhanced mortality rates of mice infected with K98, and administration of 16,16-dimethyl PGE₂ (dPGE) reversed this effect. However, mice infected with RA did not reduce their mortality rates by administration of diverse doses of dPGE. These findings suggest that PGE₂ could play a role in resistance in mice infected with K98.     

Allosteric effects of monoclonal antibodies on human growth hormone

We have previously shown that a monoclonal antibody (MAb) recognizing the human growth hormone (hGH) antigenic domain left exposed after binding to lactogenic receptors enhanced hGH binding probably through allosteric effects on the hormone binding site. Since receptors displaying different specificities would not recognize exactly the same hGH region, we explored whether some of our MAb could affect hGH binding to somatogenic receptors from rabbit liver and to human liver hGH-specific receptors.The effect of MAbAE5, AC8 and F11 on hGH binding was measured by determining the formation of¹²⁵I-MAb:hGH:receptor complexes using two different experimental approaches. Results from procedure A, which involved the previous binding of the hormone to microsomes before adding¹²⁵I-MAb, indicated that the hGH domain defined by epitopes AE5, AC8 and F11 is uncovered in the various hormone:receptor complexes.Procedure B was devised to reveal any alteration in the hGH molecule induced by the MAb. In this case preformed¹²⁵I-MAb:hGH complexes were added to microsomes. Data showed that¹²⁵I-MAb AE5:hGH complexes bound better to the various receptors than¹²⁵I-MAb AE5 to hGH:receptor complexes. On the contrary, hGH previously bound to¹²⁵I-MAb AC8 or¹²⁵I-MAb F11 was less recognized by the receptors than the free hormone. Furthermore, binding of MAb AE5 or MAb F11 to hGH 20 K (a natural hGH variant lacking residues 32–46) also enhanced its affinity to the various receptors whereas MAb AC8 did not inhibit hGH 20 K binding.Results indicated that MAb recognizing the hGH antigenic area that remains unmasked after binding to different membrane-bound receptors are able to affect hormone binding site. MAb would induce either positive or negative allosteric changes in the hormone region involved in its binding to lactogenic, somatogenic and hGH-specific receptors.