Trypanocidal activity of a new pterocarpan and other secondary metabolites of plants from Northeastern Brazil flora

Two hundred fifteen compounds isolated from plants of Northeastern Brazil flora have been assayed against epimastigote forms of Trypanosoma cruzi, using the tetrazolium salt MTT as an alternative method. Eight compounds belonging to four different species: Harpalyce brasiliana (Fabaceae), Acnistus arborescens and Physalis angulata (Solanaceae), and Cordia globosa (Boraginaceae) showed significant activity. Among them, a novel and a known pterocarpan, a chalcone, four withasteroids, and a meroterpene benzoquinone were the represented chemical classes.     

Tissue-specific regulation of BiP genes: a cis-acting regulatory domain is required for BiP promoter activity in plant meristems

The binding protein BiP is an endoplasmic reticulum (ER)-resident member of the HSP70 stress-related protein family, which is essential for the constitutive function of the ER. In addition to responding to a variety of environmental stimuli, plant BiP exhibits a tissue-specific regulation. We have isolated two soybean BiP genomic clones, designated gsBiP6 and gsBiP9, and different extensions of their 5 flanking sequences were fused to -glucuronidase (GUS) reporter gene and introduced into Nicotiana tabacum by Agrobacterium tumefaciens-mediated transformation. Transgenic plants displayed prominent GUS activity in the vascular bundles of roots and shoots as well as in regions of intense cell division, such as procambial region and apical meristems. Promoter deletion analyses identified two cis-regulatory functional domains that are important for the spatially-regulated activation of BiP expression under normal plant development. While an AT-rich enhancer-like sequence, designated cis-acting regulatory domain 1, CRD1 (–358 to –211, on gsBiP6), activated expression of the BiP minimal promoter in all organs analyzed, BiP promoter activity in meristematic tissues and phloem cells required the presence of a second activating domain, CRD2 (–211 to –80). Apparently, the CRD2 sequence also harbors negative cis-acting elements, because removal of this region caused activation of gsBiP6 promoter in parenchymatic xylem rays. These results suggest that the tissue-specific control of BiP gene expression requires a complex integration of multiple cis-acting regulatory elements on the promoter.     

Material Spiraling in Stream Corridors: A Telescoping Ecosystem Model

Stream ecosystems consist of several subsystems that are spatially distributed concentrically, analogous to the elements of a simple telescope. Subsystems include the central surface stream, vertically and laterally arrayed saturated sediments (hyporheic and parafluvial zones), and the most distal element, the riparian zone. These zones are hydrologically connected; thus water and its dissolved and suspended load move through all of these subsystems as it flows downstream. In any given subsystem, chemical transformations result in a change in the quantity of materials in transport. Processing length is the length of subsystem required to “process” an amount of substrate equal to advective input. Long processing lengths reflect low rates of material cycling. Processing length provides the length dimension of each cylindrical element of the telescope and is specific to subsystem (for example, the surface stream), substrate (for instance, nitrate), and process (denitrification, for example). Disturbance causes processing length to increase. Processing length decreases during succession following disturbance. The whole stream-corridor ecosystem consists of several nested cylindrical elements that extend and retract, much as would a telescope, in response to disturbance regime. This telescoping ecosystem model (TEM) can improve understanding of material retention in running water systems; that is, their “nutrient filtration” capacity. We hypothesize that disturbance by flooding alters this capacity in proportion to both intensity of disturbance and to the relative effect of disturbance on each subsystem. We would expect more distal subsystems (for example, the riparian zone) to show the highest resistance to floods. In contrast, we predict that postflood recovery of functions such as material processing (that is, resilience) will be highest in central elements and decrease laterally. Resistance and resilience of subsystems are thus both inversely correlated and spatially separated. We further hypothesize that cross-linkages between adjacent subsystems will enhance resilience of the system as a whole. Whole-ecosystem retention, transformation, and transport are thus viewed as a function of subsystem extent, lateral and vertical linkage, and disturbance regime. Received 15 April 1997; accepted 1 September 1997.     

The role of glia in neuronal recovery following anoxia: In vitro evidence of neuronal adaptation

We investigated the effects of 3h of anoxia on metabolism of neurons and astrocytes, using a robust cell-based model system that mimics closely the living tissue milieu, i.e., in 3D neural aggregates cultured in bioreactors. Cells were incubated simultaneously with [1-(13)C]glucose and [1,2-(13)C]acetate; and, the gliotoxin fluorocitrate (FC) was used for glial tricarboxylic acid (TCA) cycle inhibition to assess the role of astrocytes for neuronal metabolism after oxygen deprivation. Results show that culture viability was not compromised by exposure to anoxia with and without FC. Interaction between astrocytes and glutamatergic neurons was altered due to anoxia: labeling in glutamine from [1-(13)C]glucose was decreased, whereas that in glutamate from [1,2-(13)C]acetate was increased. In contrast, GABA labeling was not affected by anoxia. It was shown that anoxia did not affect astrocytic capacity to synthesize glutamine in the reoxygenation period. The selective action of FC on astrocytes was confirmed. However, the presence of small amounts of glutamate and GABA labeled from acetate indicated residual activity of the glial TCA cycle. Although major metabolic changes were found due to FC-treatment, the intracellular pool of GABA was kept unchanged. Overall, our data clearly confirm that the glutamate-glutamine cycle depends on astrocytic TCA cycle activity and that mitochondrial impairment of astrocytes will ultimately stop metabolic trafficking between astrocytes and glutamatergic neurons. Additionally, our data suggest a metabolic independence of GABAergic neurons from astrocytes even after situations of complete oxygen depletion.     

Concordance of leishmaniasis cutaneous tests in Tunisia

A cross sectional study aimed to evaluate the effect of antigenic preparation (Leishmania infantum versus Leishmania major) and dose of leishmania antigens (5 x 10(6) versus 2.5 x 10(6) parasites in the same volume) on the reproducibility of delayed type hypersensitivity leishmania skin test. Results showed that among 34 individuals involved from visceral leishmaniasis endemic area. 26 (76.5%) had a positif Leishmania infantum leishmania (L-L. infantum) test and 27 (79.4%) to Leishmania major leishmania (L-L. major). Mean size of cutaneous reaction was 5.94 +/- 2.86 mm for L-L. infantum and 5.41 +/- 3.23 mm for L-L. major, with a significant positive linear association (p < 10-3). Intra-class correlation coefficient was 0.80 (CI95% = [0.64-0.93]) and concordance Kappa (kappa) was 0.57 (CI95% = [0.40-0.74]). Among 153 individuals from zoonotic cutaneous leishmaniasis. 92.9% revealed a positive test for both types of leishmanin (L-L. major full dose versus L-L. major half dose). Mean size of cutaneous reaction was 12.61 +/- 4.65 mm for the reference test and 11.30 +/- 3.95 mm for diluted one, with a positive linear association (p < 10-3). Intra-class correlation coefficient was 0.78 (IC95% = [0.71-0.84]) and concordance Kappa (kappa) was 0.82 (IC95% = [0.73-0.91]). These results demonstrate a limited effect of leishmania antigenic variation and antigen dose on the reproducibility of delayed type hypersensitivity induced by the leishmanin test.     

X-ray structure of TMP kinase from Mycobacterium tuberculosis complexed with TMP at 1.95 A resolution

The X-ray structure of Mycobacterium tuberculosis TMP kinase at 1.95 A resolution is described as a binary complex with its natural substrate TMP. Its main features involve: (i) a clear magnesium-binding site; (ii) an alpha-helical conformation for the so-called LID region; and (iii) a high density of positive charges in the active site. There is a network of interactions involving highly conserved side-chains of the protein, the magnesium ion, a sulphate ion mimicking the beta phosphate group of ATP and the TMP molecule itself. All these interactions conspire in stabilizing what appears to be the closed form of the enzyme. A complete multialignment of all (32) known sequences of TMP kinases is presented. Subtle differences in the TMP binding site were noted, as compared to the Escherichia coli, yeast and human enzyme structures, which have been reported recently. These differences could be used to design specific inhibitors of this essential enzyme of nucleotide metabolism. Two cases of compensatory mutations were detected in the TMP binding site of eukaryotic and prokaryotic enzymes. In addition, an intriguing high value of the electric field is reported in the vicinity of the phosphate group of TMP and the putative binding site of the gamma phosphate group of ATP.     

Hydrocortisone increases the rate of differentiation of cultured human osteoblasts

Reduced bone formation is the main finding in glucocorticoid-induced osteoporosis. The aim of this study was to determine whether differentiation of cultured human osteoblasts is inhibited by high concentrations of hydrocortisone. We measured the levels of mRNAs for three markers of cellular differentiation, type 1 collagen (COL1), alkaline phosphatase (ALP), and osteocalcin (OC), in four lines of human osteoblasts from female donors cultured with doses of hydrocortisone from 0 microM to 4 microM. The change in ALP/COL1 mRNA ratio over a given time was used to determine the average rate of differentiation of the cells in a culture. Although basal expression profiles and their changes with time were different for the different cell lines, all cell lines showed a dose-dependent rise in the rate of increase of ALP mRNA relative to COL1 mRNA. However, increase in OC mRNA with time, seen here only in young donor hOBs, was significantly inhibited by 4 microM hydrocortisone, indicating that hydrocortisone can inhibit OC expression while promoting cellular differentiation. The data suggest that increasing concentrations of glucocorticoid, including concentrations similar to plasma levels in patients receiving oral glucocorticoid therapy, increase the rate of cellular differentiation.     

Antimicrobial activity of fractions and compounds from Calophyllumbrasiliense (Clusiaceae/Guttiferae)

Calophyllum brasiliense (Clusiaceae/Guttiferae) is a native Brazilian medicinal plant traditionally used against several diseases, including infectious pathologies. Crude methanolic extracts (CME) and two fractions, denoted non-polar (soluble in chloroform) and polar (nonsoluble in chloroform), were prepared from different parts of the plant (roots, stems, leaves, flowers and fruits) and studied. The following compounds were isolated and tested against pathogenic bacteria and yeasts by determination of the minimal inhibitory concentration (MIC): brasiliensic acid (1), gallic acid (2), epicatechin (3), protocatechuic acid (4), friedelin (5) and 1,5-dihydroxyxanthone (6). The results indicated that all the parts of the plant exhibited antimicrobial activity against Gram-positive bacteria, which are selectively inhibited by components of C. brasiliense. No activity was observed against Gram-negative bacteria and yeasts tested. Regarding the isolated compounds, substance 4 showed antimicrobial activity against all the tested microorganisms, whereas compound 6 exhibited antimicrobial activity only against Gram-positive bacteria. The results from the current study confirm and justify the popular use of this plant to treat infectious processes.