Possible Involvement of ERK 1/2 in UVA‐Induced Melanogenesis in Cultured Normal Human Epidermal Melanocytes

UV‐induced melanogenesis is a well known physiological response of human skin exposed to solar radiation; however, the signaling molecules involved in the stimulation of melanogenesis in melanocytes following UV exposure remain unclear. In this study we induced melanogenesis in vitro in normal human epidermal melanocytes using a single irradiation with UVA at 1 kJ/m² and examined the potential involvement of mitogen‐activated protein kinases (MAPK) as UVA‐responsive signaling molecules in those cells. UVA irradiation did not affect the proliferation of melanocytes, but it did increase tyrosinase mRNA expression, which reached a maximum level 4 hr after UVA irradiation. The amount of tyrosinase protein, as quantitated by immunoblotting, was also increased at 24 hr following UVA irradiation. Among the MAPK examined, extracellular signal‐related kinase (ERK) 1/2 was phosphorylated within 15 min of UVA irradiation, but no such phosphorylation was observed for c‐Jun N‐terminal kinases (JNK) or p38. Accordingly, the activity of ERK1/2 was also increased shortly after UVA irradiation. These responses of ERK1/2 to UVA irradiation were markedly inhibited when cells were pre‐treated with N‐acetyl‐l ‐cysteine, an antioxidant, or with suramin, a tyrosine kinase receptor inhibitor. The formation of (6‐4)photoproducts or cyclobutane pyrimidine dimers was not detected in cellular DNA after UVA irradiation. These findings suggest that a single UVA irradiation‐induced melanogenesis is associated with the activation of ERK1/2 by upstream signals that originate from reactive oxygen species or from activated tyrosine kinase receptors, but not from damaged DNA.     

Differences in phenotypic traits and migratory strategies between eastern North American monarch butterflies,Danaus plexippus (L.)

The eastern North American population of the monarch butterfly (Danaus plexippus plexippus) has different migratory routes. The majority fly to overwintering colonies in Mexico and others take an eastern route through Florida and Cuba. Monarchs migrating through Florida–Cuba do not overwinter and are mostly found nectaring and flying close to vegetation. This present study explores whether Florida–Cuba versus Mexican migrants differ in (1) phenotypic traits important for migration (e.g. wing size and condition, lipid and lean mass content, and reproductive status) and (2) migratory strategies. The monarch natal grounds (e.g. migrants versus residents) were determined through thin‐layer chromatography cardenolide fingerprint and stable isotopes (hydrogen δ²H and carbon δ¹³C). In addition, wing size and condition, lipid and lean mass, and reproductive status were determined. The results suggest that Mexican migrants are better suited for longer sustained flights and successful overwinter periods as a result of larger wings in better condition, reproductive diapause, and significant fat content. By contrast, Florida–Cuba migrants are more suited for shorter flights and opportunistic migratory strategies, given that their wings were in poor condition, as well as the active reproductive status of > 50% of these butterflies and their significantly low fat content. Eastern monarch migration is more complex and diverse than previously assumed. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, ?? , ??–??.     

EFFECT OF FEEDBACK ON SENSORY TRAINING: A PRELIMINARY STUDY

Feedback in sensory training can facilitate performance in several ways. It can provide information about the type, the extent and the direction of errors so that they may be corrected. This paper shows the effects of immediate feedback over a three session training. Triangle test, familiar odor recognition and scaling test were used in training. The scaling test, specially designed for this study, was performed with solutions of mixtures of basic tastes in different proportions.
Prior sensory ability was taken into account by dividing 54 people into two groups according to their sensory ability. Each group was then split into an experimental group receiving feedback and into a control group.
The results showed that feedback has different effects depending on test: a positive effect for recognition test, no effect for triangle test and a probable negative effect for scaling.     

Control of Trypanosoma cruzi Epimastigote Motility through the Nitric Oxide Pathway

ABSTRACT. Trypanosoma cruzi epimastigote motility can be enhanced by addition of L-arginine, to the culture. This effect is blocked by N-methyl-L-arginine, a competitive inhibitor of the nitric oxide synthase. N-methyl-D-aspartate and L-glutamate, two agonists of the NMDALglutamate receptor, also enhanced motility. This stimulation is blocked by MK-801 a noncompetitive antagonist of the NMDA receptor. In addition, sodium nitroprusside, a guanylyl cyclase stimulator and 8-Br-cyclic GMP, an analog of cyclic GMP, also stimulated epimastigote motility. It is suggested that an increase of intracellular cyclic GMP levels mediated by nitric oxide may be responsible for the increase in epimastigote motility.     

Detection of Penicillin-binding Proteins in the Endosymbiont of the Trypanosomatid Crithidia deanei

ABSTRACT. Growth by serial transfers of the trypanosomatid Crithidia deanei in culture medium containing 1 mg/ml of the β-lactam antibiotics ampicillin or cephalexin resulted in shape distortion of its endosymbiont. The endosymbiont first appeared as filamentous structures with restricted areas of membrane damage. An increase of electron lucid areas was also observed in the endosymbiont matrix. The continuous treatment with β-lactam antibiotics, resulted in endosymbiont membranes fragmentation; and later on the space previously occupied by the symbiont was identified as an electron lucid area in the host cytoplasm. The putative targets of β-lactam antibiotic were two membrane-bound penicillin-binding proteins (PBPs) detected in the Sarkosyl-soluble fraction of purified symbionts labeled with [³H]-benzylpenicillin. The apparent molecular weight of the proteins were 90 kDa (PBP1) and 45 kDa (PBP2). PBP2 represented 85% of the total PBP content in the membrane fraction of the endosymbionts. Competition experiments using the tested antibiotics and [³H]-benzylpenicillin showed that ampicillin and cephalexin have half saturating concentrations considerably higher than [³H]-benzylpenicillin and indicated that PBP1 is the probable lethal target of the antibiotics tested. These results suggest that a physiologically active PBP is present in the cell envelope of C. deanei endosymbionts and may play important roles in the control of processes such as cell division and shape determination.     

Thermoregulation and flying habits of the Japanese sulfur butterfly Colias erate (Lepidoptera: Pieridae) in an open habitat

This study evaluated the impact of the thermal environment on the flying behavior of male Japanese sulfur butterflies Colias erate searching for females in an open habitat. Thoracic temperature was monitored before and after flight. Mean thoracic temperature of butterflies immediately after landing was consistently higher than, but independent of, ambient temperature. Although ground speed of flying butterflies was different between flight types, air speed against the butterfly was similar across flight types. The excess of thoracic over ambient temperature was lower in flying butterflies than in basking ones, as predicted by a model. This difference appeared to be due to air current, which enhanced heat loss. In a laboratory study, newly eclosed male butterflies were placed under an incandescent lamp to measure their thoracic temperature at different air current speeds. The excess of thoracic over ambient temperature decreased as the speed of air currents increased. When the air current was similar to the air speed against flying butterflies in the field, a substantial decrease occurred in the operative thoracic temperature.