ACC synthase expression regulates leaf performance and drought tolerance in maize

Ethylene regulates entry into several types of plant developmental cell death and senescence programs besides mediating plant responses to biotic and abiotic stress. The response of cereals to conditions of drought includes loss of leaf function and premature onset of senescence in older leaves. In this study, ACC synthase ( ACS ) mutants, affecting the first step in ethylene biosynthesis, were isolated in maize and their effect on leaf function examined. Loss of ZmACS6 expression resulted in delayed leaf senescence under normal growth conditions and inhibited drought-induced senescence. Zmacs6 leaves continued to be photosynthetically active under both conditions indicating that leaf function was maintained. The delayed senescence phenotype associated with loss of ZmACS6 expression was complemented by exogenous ACC. Surprisingly, elevated levels of foliar chlorophyll, Rubisco, and soluble protein as well as improved leaf performance was observed for all Zmasc6 leaves, including young and fully expanded leaves which were far from initiating senescence. These observations suggest that ethylene may serve to regulate leaf performance throughout its lifespan as well as to determine the onset of natural senescence and mediate drought-induced senescence.     

Synthesis and evaluation of lasonolide A analogues

Homolasonolide A and 10-desmethyllasonolide A are biologically less active than lasonolide A. The ethyl ester analogue of lasonolide A exhibited higher activity than the parent compound in some biological test.     

Triaryl methane derivatives as antiproliferative agents

Clotrimazole (CLT) 1, a synthetic anti-fungal imidazole derivative, inhibits tumor cell proliferation and angiogenesis. In the current study, flow cytometric analysis demonstrated that the decrease in tumor cell growth by CLT 1 was associated with inhibition of cell cycle progression at the G(1)-S phase transition, resulting in G(0)-G(1) arrest. A series of CLT 1 analogues has been generated in order to develop CLT 1 derivatives that are devoid of the imidazole moiety which is responsible for the hepatoxicity associated with CLT 1 while retaining CLT 1 efficacy. The majority of these analogues demonstrate in vitro antiproliferative activity ranging from submicromolar to micromolar concentrations.     

Structure-based virtual screening and biological evaluation of potent and selective ADAM12 inhibitors

We describe a series of potent and selective inhibitors of ADAM12 that were discovered using computational screening of a focused virtual library. The initial structure-based virtual screening selected 64 compounds from a 3D database of 67,062 molecules. Being evaluated by a cell-based ADAM12 activity assay, compounds 5, 11, 14, 16 were further identified as the potent and selective inhibitors of ADAM12 with low nanomolar IC₅₀ values. The mechanism underlying the potency and selectivity of a representative compound, 5, was investigated through molecular docking studies.     

Hunting restraint by Creoles at the Community Baboon Sanctuary, Belize: a preliminary survey

This study surveyed 33 male hunters between the ages of 17 and 54 at the Community Baboon Sanctuary (CBS), Belize, to evaluate attitudes and behaviors in relation to hunting black howler monkeys (Alouatta pigra). The study defined hunting restraint as a learned predisposition not to hunt 1 or more species of nonhuman animal. Consistent with Belizean folklore, Creoles at the CBS exhibited hunting restraint with respect to black howlers, preferring to kill bushmeat other than monkeys. The most cited reasons for the observed hunting restraint were utilitarian. Historical and cultural factors also appeared significant. The study results are interpreted in terms of economic theory and suggest that disinhibition of hunting restraint might depend on changes in opportunity costs of hunting these primates. Nonetheless, a change in hunting attitudes and behaviors by Belizean Creoles seems unlikely in the near future because the local and national government and the benefits of ecotourism economically and legally protect howlers. The Creoles' culturally transmitted hunting restraint also culturally protects A. pigra, and the species is not a preferred source of food.     

Modifications of serotonergic and adrenergic receptor concentrations in the brain of aggressive Canis familiaris

The aim of the study was to measure beta-adrenergic (beta-AR) and serotonergic (5-HTR) receptor concentrations in different brain areas (frontal cortex, hippocampus, hypothalamus and thalamus) of normal and aggressive dogs. Eight adult male dogs, 4.2+/-0.6 years old, showing no clinical signs but aggression, were used for the study. Eight healthy male dogs, 4.4+/-0.8 years old, with no history of neurological and/or behavioural disorders and accidental death, were used as controls. The whole frontal cortex, hippocampus, thalamus and hypothalamus were collected after euthanasia and plasma membrane fractions obtained by ultracentrifugation. beta-AR and 5-HTR were measured by binding assays using specific radioligand [(-)[3H]CGP 12177 and 5-hydroxy[3H]-tryptamine trifluoroacetate, respectively]. A significant decrease in beta-AR levels was observed in the frontal cortex (P=0.001), hippocampus (P<0.0001), and thalamus (P<0.0001) of aggressive dogs compared to controls. As far as 5-HTR are concerned, two receptor subtypes were detected. The two subtypes were classified as low-affinity (5-HTR LA) and high-affinity (5-HTR HA) serotonergic receptors for [3H]-hydroxytryptamine, on the basis of their affinity for [3H]-hydroxytryptamine. 5-HTR LA significantly increased in the whole central nervous system (CNS) area of aggressive dogs (frontal cortex P=0.071; hippocampus P=0.0013; thalamus P<0.0001; hypothalamus P=0.0004); 5-HTR HA significantly increased only in the thalamus (P=0.0005) and hypothalamus (P=0.0002). Results suggest the possible role played by the catecholaminergic and serotonergic systems in canine aggressive behaviour. The understanding of the biological basis of canine aggression may enable the development of pharmacological treatments that would target specific neurotransmitter systems.     

Functional genomic approaches using the nematode Caenorhabditis elegans as a model system

Since the completion of the genome project of the nematode C. elegans in 1998, functional genomic approaches have been applied to elucidate the gene and protein networks in this model organism. The recent completion of the whole genome of C. briggsae, a close sister species of C. elegans, now makes it possible to employ the comparative genomic approaches for identifying regulatory mechanisms that are conserved in these species and to make more precise annotation of the predicted genes. RNA interference (RNAi) screenings in C. elegans have been performed to screen the whole genome for the genes whose mutations give rise to specific phenotypes of interest. RNAi screens can also be used to identify genes that act genetically together with a gene of interest. Microarray experiments have been very useful in identifying genes that exhibit co-regulated expression profiles in given genetic or environmental conditions. Proteomic approaches also can be applied to the nematode, just as in other species whose genomes are known. With all these functional genomic tools, genetics will still remain an important tool for gene function studies in the post genome era. New breakthroughs in C. elegans biology, such as establishing a feasible gene knockout method, immortalized cell lines, or identifying viruses that can be used as vectors for introducing exogenous gene constructs into the worms, will augment the usage of this small organism for genome-wide biology.     

Molecular investigation of two consecutive nosocomial clusters of Candida tropicalis candiduria using pulsed-field gel electrophoresis

Pulsed-field gel electrophoresis (PFGE) typing was applied to the epidemiological investigation of 21 Candida tropicalis isolates collected from urine specimens of 11 patients and one healthcare worker, in an intensive care unit (ICU) over a 4-month period. Seventeen epidemiologically unrelated strains from 14 patients were also tested to determine the discriminatory power of PFGE. PFGE typing consisted of electrophoretic karyotyping (EK) and restriction endonuclease analysis of genomic DNA (REAG), using two restriction enzymes (BssHII and SfiI). The EK pattern was the same in all 38 isolates, while REAG using SfiI separated the isolates into nine types. However, 16 different PFGE types were identified by REAG with BssHII, and the same results were obtained when the results of both REAG tests were combined. In serial urinary isolates from 10 patients, all strains from each patient had the same PFGE pattern. While the epidemiologically unrelated strains from 14 patients consisted of 13 different PFGE types, the 20 isolates from the 11 ICU patients fell into only two PFGE types (types C1 and C2), and these apparently originated from the two different outbreaks. All strains of type C1 (n = 12) were isolated from six patients, between November 1999 and January 2000, and all of the type C2 strains (n=8) were isolated from five patients, during January and February 2000. This study shows two consecutive clusters of C. tropicalis candiduria in an ICU, defined by PFGE typing, and also demonstrates that a PFGE typing method using BssHII is perhaps the most useful method for investigating C. tropicalis candiduria.