Thermal biology and locomotor performance of the Andean lizard Liolaemus fitzgeraldi (Liolaemidae) in Argentina

Ectotherms thermoregulate to maintain their body temperature within the optimal range needed for performing vital functions. The effect of climate change on lizards has been studied as regards the sensitivity of locomotor performance to environmental temperatures. We studied thermoregulatory efficiency and locomotor performance for Liolaemus fitzgeraldi in the Central Andes of Argentina. We determined body temperature, micro-environmental temperatures and operative temperatures in the field. In the laboratory, we measured preferred temperatures and calculated the index of thermoregulatory efficiency. We estimated the thermal sensitivity of locomotion by measuring sprint speed (initial velocity and long sprint) and endurance at five different body temperatures. Body temperature was not associated with either micro-environmental temperature, nor did it show differences with preferred temperatures. Thermoregulatory efficiency was moderate (0.61). Initial velocity and long sprint trials showed differences at different temperatures; however, endurance did not. Moreover, the optimal temperatures for the performance trials showed no significant differences among themselves. We conclude that Liolaemus fitzgeraldi has thermal sensitivity in locomotor performance with respect to body temperature and that it is an eurythermic lizard that experiences a large variation in body temperature and that has thermal flexibility in the cold.     

1-Aminocyclopropane-1-carboxylic acid as a substrate of peroxidase: conditions for oxygen consumption, hydroperoxide generation and ethylene production

Conditions in which 1-aminocyclopropane-1-carboxylic acid (ACC) functions as a substrate of peroxidase have been investigated by measuring oxygen consumption in the reaction medium and the production of ethylene. In both cases, the presence of Mn2+ and either H2O2 or the activated form of peroxidase, namely compound I of peroxidase, was found to be essential. Both oxygen consumption and ethylene production were dependent on enzyme concentration, the optimum ACC/Mn2+ ratio being 1:1. Oxygen consumption in a system with ACC, Mn2+ and compound I showed an enzyme-dependent lag phase and then proceeded to total depletion, suggesting that the system itself generates hydroperoxides that completed the catalytic cycle of the enzyme. The presence of these hydroperoxides in the reaction medium was detected by a colorimetric method. High H2O2 concentration progressively decreased oxygen consumption, the same effect being produced by catalase. Ethylene production was oxygen dependent, mediated by ACC-free radicals and gave a poor yield. The results suggest that the fate of these ACC-free radicals determines the yield in ethylene. These radicals must be oxidized immediately, otherwise their stabilization to hydroperoxides would prevent ethylene production.     

Multiple factors influence adventitious rooting in carnation (<Emphasis Type="Italic">Dianthus caryophyllus</Emphasis> L.) stem cuttings

Efficient propagation of uniform starting material is a critical requirement for mass production of most ornamental plants, including carnation. For some elite cultivars, the production of young plantlets is limited by poor adventitious root formation from stem cuttings. We previously characterized the molecular signature during adventitious rooting in two carnation cultivars, 2101-02 MFR and 2003 R 8, which were selected because of their contrasting rooting performance. To determine additional factors that contribute to the differences observed in adventitious rooting during the commercial scaling-up of this species, we characterized rooting performance and endogenous hormone levels in stem cuttings of these two cultivars during one production season. We found that stem cutting production declined during the harvest season in a cultivar-dependent manner. In addition, the initiation of adventitious roots in the stem cutting base depended on its endogenous auxin and cytokinin levels at harvest time, while their subsequent growth and development was mainly influenced by the physiological status of the mother plant at harvest time and of the stem cutting during the rooting process.     

Rotavirus VP4 and VP7-Derived Synthetic Peptides as Potential Substrates of Protein Disulfide Isomerase Lead to Inhibition of Rotavirus Infection

Rotavirus infection of MA104 cells has been shown to be inhibited by cell membrane-impermeant thiol/disulfide exchange inhibitors and anti-PDI antibodies. To characterise the amino acid sequences of rotavirus structural proteins potentially mediating cell surface PDI?Csubstrate interactions, rotavirus-derived peptides from VP4 and VP7 (RRV) and VP7 (Wa), and their modified versions containing serine instead of cysteine were synthesized. Cysteine-containing VP7 peptides corresponding to residues 189?C210 or 243?C263 caused an infectivity inhibitory effect of about 64 and 85?%, respectively, when added to cells. Changing cysteine to serine significantly decreased the inhibitory effect. A cysteine-containing peptide corresponding to VP4 residues 200?C219 and its scrambled version reduced infectivity by 92 and 80?%, respectively. A cysteine to serine change in the original VP4 200?C219 peptide did not affect its inhibitory effect. Non-rotavirus related sequences containing cysteine residues efficiently inhibited rotavirus infectivity. Antibodies against VP7 residues 189?C210 or 243?C263 significantly inhibited rotavirus infectivity only after virus attachment to cells had occurred, whereas those against VP4 200?C219 peptide inhibited infectivity irrespective of whether virus or cell-attached virus was antibody-treated. A direct PDI?Cpeptide interaction was shown by ELISA for cysteine-containing VP7 and VP4 peptides. Virus?Ccell attachment was unaffected by the peptides inhibiting virus infectivity. The results showed that even though cysteine residues in the peptides tested are important in both virus infectivity inhibition and in vitro PDI?Cpeptide interaction, the accompanying amino acid sequence also plays some role. As a whole, our findings further support our hypothesis that cell surface PDI from MA104 cells might be contributing to rotavirus entry at a post-attachment step.     

Evolution and distribution of growth in etiolated hypocotyls ofLupinus albus

The variations in length and fresh and dry mass of etiolated hypocotyls of lupin during the growth have been studied. The growth exhibited by the different zones delimited along the hypocotyl was dependent on the localization of the zone as well as on the age of seedlings, but in both cases the pattern of growth was similar. During the period of growth studied (seedlings 7 to 21 d old), the growth of hypocotyl was basically due to cell elongation, since the relative elongation of cells was positively correlated with the relative elongation of the hypocotyl.     

Experimental Lagos bat virus infection in straw-colored fruit bats: A suitable model for bat rabies in a natural reservoir species

Rabies is a fatal neurologic disease caused by lyssavirus infection. Bats are important natural reservoir hosts of various lyssaviruses that can be transmitted to people. The epidemiology and pathogenesis of rabies in bats are poorly understood, making it difficult to prevent zoonotic transmission. To further our understanding of lyssavirus pathogenesis in a natural bat host, an experimental model using straw-colored fruit bats (Eidolon helvum) and Lagos bat virus, an endemic lyssavirus in this species, was developed. To determine the lowest viral dose resulting in 100% productive infection, bats in five groups (four bats per group) were inoculated intramuscularly with one of five doses, ranging from 10^0.1 to 10^4.1 median tissue culture infectious dose (TCID₅₀). More bats died due to the development of rabies after the middle dose (10^2.1 TCID₅₀, 4/4 bats) than after lower (10^1.1, 2/4; 10^1.1, 2/4) or higher (10^3.1, 2/4; 10^4.1, 2/4) doses of virus. In the two highest dose groups, 4/8 bats developed rabies. Of those bats that remained healthy 3/4 bats seroconverted, suggesting that high antigen loads can trigger a strong immune response that abrogates a productive infection. In contrast, in the two lowest dose groups, 3/8 bats developed rabies, 1/8 remained healthy and seroconverted and 4/8 bats remained healthy and did not seroconvert, suggesting these doses are too low to reliably induce infection. The main lesion in all clinically affected bats was meningoencephalitis associated with lyssavirus-positive neurons. Lyssavirus antigen was detected in tongue epithelium (5/11 infected bats) rather than in salivary gland epithelium (0/11), suggesting viral excretion via the tongue. Thus, intramuscular inoculation of 10^2.1 TCID₅₀ of Lagos bat virus into straw-colored fruit bats is a suitable model for lyssavirus associated bat rabies in a natural reservoir host, and can help with the investigation of lyssavirus infection dynamics in bats.     

In vitro and in vivo characterization of an interleukin‐15 antagonist peptide by metabolic stability, 99mTc‐labeling,and biological activity assays

Interleukin (IL)–15 is an inflammatory cytokine that constitutes a validated therapeutic target in some immunopathologies, including rheumatoid arthritis (RA). Previously, we identified an IL‐15 antagonist peptide named [K6T]P8, with potential therapeutic application in RA. In the current work, the metabolic stability of this peptide in synovial fluids from RA patients was studied. Moreover, [K6T]P8 peptide was labeled with ^99mTc to investigate its stability in human plasma and its biodistribution pattern in healthy rats. The biological activity of [K6T]P8 peptide and its dimer was evaluated in CTLL‐2 cells, using 3 different additives to improve the solubility of these peptides. The half‐life of [K6T]P8 in human synovial fluid was 5.88 ± 1.73 minutes, and the major chemical modifications included peptide dimerization, cysteinylation, and methionine oxidation. Radiolabeling of [K6T]P8 with ^99mTc showed a yield of approximately 99.8%. The ^99mTc‐labeled peptide was stable in a 30‐fold molar excess of cysteine and in human plasma, displaying a low affinity to plasma proteins. Preliminary biodistribution studies in healthy Wistar rats suggested a slow elimination of the peptide through the renal and hepatic pathways. Although citric acid, sucrose, and Tween 80 enhanced the solubility of [K6T]P8 peptide and its dimer, only the sucrose did not interfere with the in vitro proliferation assay used to assess their biological activity. The results here presented, reinforce nonclinical characterization of the [K6T]P8 peptide, a potential agent for the treatment of RA and other diseases associated with IL‐15 overexpression.     

Fatty acid composition of Simonsiella strains

Gas-liquid chromatography of methyl esters of bound fatty acids extracted from the cells of 48 Simonsiella strains showed that these aerobic, gliding, multicellular-filamentous bacteria have fatty acid profiles of the pattern considered typical of Gramnegative eubacteria. All strains contained predominantly tetradecanoic acid (29.5%), 9-hexadecenoic acid (22.2%), an unidentified acid with an equivalent chain length of approximately 20 carbon atoms (15.8%), and dodecanoic acid (11.4%).Discriminant analysis of the mean relative percentages of 12 fatty acids correctly assigned 94% of the strains to groups based on their source of origin (i.e., the oral cavities of sheep, cat, human or dog); the relative amounts of only 3 of the fatty acids (9-octadecenoic acid, hexadecanoic acid, and tetradecanoic acid) provided most of this discrimination.