The renin-angiotensin system in rats made hypertensive by ligation of the kidney poles (38584).

The renin-angiotensin system was studied in experimental renal hypertension produced by ligation of the poles of the left kidney followed by contralateral nephrectomy. Plasma renin concentration of renin substrate was lower and that of angiotensin I converting enzyme was higher in hypertensive animals. The juxtaglomerular index decreased in the medial zone of the kidney, while heavily granulated areas appeared in the poles. Ligated kidneys of rats that remained normotensive showed juxtaglomerular indices intermediate between the control and the hypertensive rats. Differences in renal renin content between the groups correspond to those for the juxtaglomerular index, but were smaller. No differences between the experimental groups were observed in iso-renin content in the brain; however in all animals with ligated kidney poles, hypertensive or normotensive, there was a tendency for iso-renin in the adrenals, left ventricular myocardium, and especially aorta to be lower than in controls.     

Mouse bone marrow cytogenetic damage produced by residues of tequila

Five concentrations (50-860 mg/kg) of residues obtained after distillation and lyophilization of commercial tequila were injected into mice for evaluation of chromosome aberrations, sister-chromatid exchanges, and proliferation kinetics in mouse bone marrow cells. Appropriate positive and negative controls were included. Our results showed significant dose-related increases of chromosomal aberrations starting at 50 mg/kg and for sister-chromatid exchanges at 430 mg/kg. Cellular proliferation kinetics showed no alterations. With these data we demonstrated that the residues of tequila are genotoxic in vivo.     

Characterization of Protease-Activated Receptor (PAR) ligands: Parmodulins are reversible allosteric inhibitors of PAR1-driven calcium mobilization in endothelial cells

Several classes of ligands for Protease-Activated Receptors (PARs) have shown impressive anti-inflammatory and cytoprotective activities, including PAR2 antagonists and the PAR1-targeting parmodulins. In order to support medicinal chemistry studies with hundreds of compounds and to perform detailed mode-of-action studies, it became important to develop a reliable PAR assay that is operational with endothelial cells, which mediate the cytoprotective effects of interest. We report a detailed protocol for an intracellular calcium mobilization assay with adherent endothelial cells in multiwell plates that was used to study a number of known and new PAR1 and PAR2 ligands, including an alkynylated version of the PAR1 antagonist RWJ-58259 that is suitable for the preparation of tagged or conjugate compounds. Using the cell line EA.hy926, it was necessary to perform media exchanges with automated liquid handling equipment in order to obtain optimal and reproducible antagonist concentration-response curves. The assay is also suitable for study of PAR2 ligands; a peptide antagonist reported by Fairlie was synthesized and found to inhibit PAR2 in a manner consistent with reports using epithelial cells. The assay was used to confirm that vorapaxar acts as an irreversible antagonist of PAR1 in endothelium, and parmodulin 2 (ML161) and the related parmodulin RR-90 were found to inhibit PAR1 reversibly, in a manner consistent with negative allosteric modulation.     

Orchid seed removal by ants in Neotropical ant‐gardens

• Most plants that inhabit ant‐gardens (AGs) are cultivated by the ants. Some orchids occur in AGs; however, it is not known whether their seeds are dispersed by AG ants because most orchid seeds are tiny and dispersed by wind.
• We performed in situ seed removal experiments, in which we simultaneously provided Azteca gnava ants with seeds of three AG orchid species and three other AG epiphyte species (Bromeliaceae, Cactaceae and Gesneriaceae), as well as the non‐AG orchid Catasetum integerrimum.
• The seeds most removed were those of the bromeliad Aechmea tillandsioides and the gesneriad Codonanthe uleana, while seeds of AG orchids Coryanthes picturata, Epidendrum flexuosum and Epidendrum pachyrachis were less removed. The non‐AG orchid was not removed. Removal values were positively correlated with the frequency of the AG epiphytes in the AGs, and seeds of AG orchids were larger than those of non‐AG orchids, which should favour myrmecochory.
• Our data show that Azt. gnava ants discriminate and preferentially remove seeds of the AG epiphytes. We report for the first time the removal of AG orchid seeds by AG ants in Neotropical AGs.

     

Proton pumping and the internal pH of yeast cells, measured with pyranine introduced by electroporation.

The internal pH of yeast cells was determined by measuring the fluorescence changes of pyranine (8-hydroxy-1,3,6-pyrene-trisulfonic acid), which was introduced into the cells by electroporation. This may be a suitable procedure for the following reasons. (i) Only minor changes in the physiological status of the cells seemed to be produced. (ii) The dye did not seem to leak at a significant rate from the cells. (iii) Different incubation conditions produced large fluorescence changes in the dye, which in general agree with present knowledge of the proton movements of the yeast cell under different conditions. (iv) Pyranine introduced by electroporation seemed to be located in the cytoplasm and to avoid the vacuole, and therefore it probably measured actual cytoplasmic pH. (v) Correction factors to obtain a more precise estimation of the internal pH are not difficult to apply, and the procedure may be useful for other yeasts and microorganisms, as well as for the introduction of other substances into cells. Values for the cytoplasmic pHs of yeast cells that were higher than those reported previously were obtained, probably because this fluorescent indicator did not seem to penetrate into the cell vacuole.     

Spatial relationships between cacti and nurse shrubs in a semi-arid environment in central Mexico

Abstract. The Zapotitlán de las Salinas valley, central Mexico, harbours a high diversity of cacti. Pattern analysis indicated that the establishment of two columnar cacti, Neobuxbaumia tetetzo and Cephalocereus hoppenstedtii, and of three small globose cacti, Coryphantapallida, Mammillaria colina andM casoi, is aggregated and associated with perennial nurse shrubs. Some nurse species, Castela tortuosa, Caesalpinia melanadenia and Eupatorium spinosarum have a higher number of cacti beneath their canopies than would be expected by chance. A replacement pattern was found between the columnar cacti and their nurses, an aspect which was not found with the globose cacti. Following the assumption that protection against excessive radiation is the main factor determining the nurse effect, the azimuth orientation of the cacti with respect to their nurses was evaluated. Only Coryphanta pallida presented a non-random distribution with a tendency towards the North and West. The difference in maximum temperature between the soil surface under the different nurse species and of open spaces, which is reached at midday, was 16 °C. No significant differences were found in beneath-canopy temperatures for the three nurse species considered. Soil nitrogen levels were significantly lower beneath the different nurse plants than in open spaces. This result suggests that soil fertility is not an important factor in the nurse-plant phenomenon in Zapotitlán.     

Bacteriological quality of crops irrigated with wastewater in the Xochimilco plots, Mexico City, Mexico

Xochimilco county plots (Mexico City), one of the most fertile agricultural areas in the Valley of Mexico, produce a large portion of the fresh vegetables consumed in the city. These plots are generally irrigated with domestic wastewater, and for this reason, it was deemed important to examine and evaluate the bacteriological quality of the water, soil, and vegetables from these plots that are harvested and marketed. The soils were also examined for the classical parameters such as nitrates, ammonia, etc., and organic matter and texture. The crops selected for this study were radishes, spinach, lettuce, parsley, and celery because they are usually consumed raw. The highest bacterial counts were encountered in leafy vegetables, i.e., spinach (8,700 for total coliform and 2,400 for fecal coliform) and lettuce (37,000 for total coliform and 3,600 for fecal coliform). Statistically significant differences in bacterial counts between rinsed and unrinsed edible portions of the crops were observed even in rinsed vegetables, and high densities of fecal coliform were detected, indicating that their consumption represents a potential health hazard. The total coliform values found in irrigation water ranged from 4 X 10(4) to 29 X 10(4), and for fecal coliform the values ranged from 5 X 10(2) to 30 X 10(2).