Anti-Pneumocystis carinii and antiplasmodial activities of primaquine-derived imidazolidin-4-ones

A series of primaquine-derived imidazolidin-4-ones were screened for their in vitro activity against Pneumocystis carinii and Plasmodium falciparum W2 strain. Most compounds were active against P. carinii above 10 microg/mL and displayed slight to marked activity. The imidazolidin-4-ones most active against P. carinii were also those most active antiplasmodial agents, in the muM range. One of the tested imidazolidin-4-ones was slightly more active than the parent primaquine and may represent a lead compound for the development of novel anti-P. carinii 8-aminoquinolines with increased stability and resistance to metabolic inactivation.     

Stem anatomy of Rhipsalis (Cactaceae) and its relevance for taxonomy

Several species of the genus Rhipsalis (Cactaceae) are extremely important as ornamentals and are endangered in their natural habitat. However, only a few studies have addressed its taxonomy, morphology (including anatomy), phylogeny and evolutionary history. Consequently, the limited knowledge of the genus coupled with the problematic delimitation of species had led to problems in the identification of taxa. In the current work six species of Rhipsalis, R. cereoides, R. elliptica, R. grandiflora, R. paradoxa, R. pentaptera and R. teres were studied to evaluate the relevance of anatomical characters for the taxonomy of the genus. An anatomical characterization of the primary structure of the stem of Rhipsalis is provided highlighting the differences between species. Features of the stem epidermis are found to discriminate best between species and therefore provide clear and useful characters for the separation of species.     

Preservation of bovine preantral follicle viability and ultra-structure after cooling and freezing of ovarian tissue

Bovine preantral follicles within ovarian fragments were exposed and cryopreserved in absence or presence of 1.5 M glycerol (GLY), ethylene glycol (EG), propanediol (PROH) or dimethyl sulfoxide (DMSO), undergoing a previous cooling at 20 °C for 1 h (protocol 1) or at 4 °C for 24 h (protocol 2) in 0.9% saline solution. At the end of each treatment, preantral follicles were classified as non-viable/viable when they were stained/not stained with trypan blue, respectively. To confirm viability staining, ultra-structure of the follicles was evaluated by transmission electronic microscopy (TEM). Data were compared by Chi-square test (P < 0.05). The storage of the ovaries at 20 °C for 1 h (78%) and 4 °C for 24 h (80%) did not reduce significantly the percentage of viable preantral follicles when compared to the control (75%). Similar results were obtained when ovarian fragments, respectively, for protocols 1 and 2, were exposed to MEM (78 and 77%), 1.5 M EG (78 and 71%), as well as frozen in 1.5 M EG (74 and 77%). Percentages of viable follicles in control were similar to those observed after exposure (75%) and freezing (76%) in presence of 1.5 M DMSO only when protocol 1 was used. The increase of the concentration from 1.5 to 3.0 M, for all cryoprotectants, reduced significantly the percentage of viable preantral follicles after freezing. Ultra-structural analysis has confirmed trypan blue results, showing that not only basement membrane, but also organelles, were intact in viable preantral follicles. In conclusion, ovarian tissue cooling at 4 °C for 24 h before cryopreservation (protocol 2) does not affect the viability of bovine preantral follicles when 1.5 M EG is present in the cryopreservation medium.     

Ultrastructure of <Emphasis Type="Italic">Eucalyptus grandis</Emphasis> × <Emphasis Type="Italic">E. urophylla</Emphasis> plants cultivated ex vitro in greenhouse and field conditions

The young and expanded leaf micromorphology and ultrastructure of Eucalyptus grandis 2 E. urophylla juvenile plants, cultivated in greenhouse and field conditions, were analyzed by scanning and transmission electron microscopy. In greenhouse leaves epicuticular wax needles covered the abaxial and adaxial surfaces. On the adaxial surface, the needles form an atypical arrangement in lines, mainly over the anticlinal wall of epidermis cells. After plant transfer to field conditions, the organization of epicuticular wax was altered forming amorphous layers on the adaxial leaf surface, in contrast to the abaxial surface, which maintained the wax needle cover. In both culture conditions the lamellar cuticle formed on the young leaves surface disappeared during leaf enlargement. The ex vitro environment induced the development of hypostomatic leaves. The dorsiventral organization of greenhouse leaves was replaced by an isobilateral arrangement in field conditions with concomitant aerial space reduction. Results suggest that those structural changes may be some of the strategies to avoid excessive plant transpiration during Eucalyptus hybrid plants' acclimatization.     

Yellow leaf syndrome modifies the composition of sugarcane juices in polysaccharides, phenols and polyamines

Some ultrastructural changes can be observed in diseased Saccharum officinarum L. (cv. Cuba 120-78) plants with visual symptoms of yellow leaf syndrome (YLS), used to discriminate between healthy and diseased plants. Abaxial epidermis of diseased leaves shows a large amount of adhered superficial bodies, which partially occluded some stomata. Bundle sheath cells surrounding the bottom of phloem of diseased leaves are separated from the conducting tissues by a large layer of an amorphous matrix similar to wax. Debris of the end wall can be observed in large xylem vessels. Sometimes, spherical bodies similar to phytoplasma can be observed in the intercellular spaces of bundle sheath cells. These particles have never been observed in healthy plants. YLS was also associated to an increase of the concentration of reducing sugars, glucose index, and glycoproteins recovered in juices whereas the amount of sucrose decreases. Sugarcane juices obtained from both healthy and YLS-affected Cuba 120-78 cultivars of sugarcane contained putrescine (PUT), cadaverine (CAD), spermidine and spermine (SPM) as free and macromolecules-conjugated compounds. Only CAD and SPM appeared as acid-soluble conjugates to small molecules whereas PUT and CAD are the major polyamines (PAs) conjugated to macromolecules, mainly to high molecular mass glycoproteins. The disease was associated to an increase in total PA fraction. Arginase and ornithine decarboxylase activities, responsible for the synthesis of PUT, were higher in YLS juices than in those obtained from healthy plants. CAD and SPM presumably conjugated mostly to chlorogenic, syringic and ferulic acids in juices from YLS plants.     

A novel approach for enhancing the catalytic efficiency of a protease at low temperature: Reduction in substrate inhibition by chemical modification

The alkaline protease, savinase was chemically modified to enhance the productivity of the enzyme at low temperatures on a complex polymeric protein (azocasein) substrate. At 5 and 15°C, savinase modified with ficol or dextran hydrolyzed fivefold more azocasein than the unmodified savinase. Kinetic studies showed that the catalytic improvements are associated with changes in uncompetitive substrate inhibition with K_i values of modified savinases sixfold higher than the unmodified savinase. Modeling of small‐angle scattering data indicates that two substrate molecules bind on opposing sides of the enzyme. The combined kinetic and structural data indicate that the polysaccharide modifier sterically blocks the allosteric site and reduces substrate inhibition. In contrast to the properties of cold‐active enzymes that generally manifest as low activation enthalpy and high flexibility, this study shows that increased activity and productivity at low temperature can be achieved by reducing uncompetitive substrate inhibition, and that this can be achieved using chemical modification with an enzyme in a commercial enzyme‐formulation. Biotechnol. Bioeng. 2009;103: 676–686. © 2009 Wiley Periodicals, Inc.