The membranotropic activity of N-terminal peptides from the pore-forming proteins sticholysin I and II is modulated by hydrophobic and electrostatic interactions as well as lipid composition

The sea anemone Stichodactyla helianthus produces two pore-forming proteins, sticholysins I and II (St I and St II). Despite their high identity (93%), these toxins exhibit differences in hemolytic activity that can be related to those found in their N-terminal. To clarify the contribution of the N-terminal amino acid residues to the activity of the toxins, we synthesized peptides spanning residues 1-31 of St I (StI1-31) or 1-30 of St II (StII1-30) and demonstrated that StII1-30 promotes erythrocyte lysis to a higher extent than StI1-31. For a better understanding of the molecular mechanism underlying the peptide activity, here we studied their binding to lipid monolayers and pemeabilizing activity in liposomes. For this, we examined the effect on peptide membranotropic activity of including phospatidic acid and cholesterol in a lipid mixture of phosphatidylcholine and sphingomyelin. The results suggest the importance of continuity of the 1-10 hydrophobic sequence in StII1-30 for displaying higher binding and activity, in spite of both peptides' abilities to form pores in giant unilamellar vesicles. Thus, the different peptide membranotropic action is explained in terms of the differences in hydrophobic and electrostatic peptide properties as well as the enhancing role of membrane inhomogeneities.     

Influence of the reinforcement magnitude on omission effects

Reinforcement Omission Effects (ROEs), indicated by higher rate of responses after nonreinforced trials in a partial reinforcement schedule, have been interpreted as behavioral transient facilitation after nonreinforcement induced by primary frustration, and/or behavioral transient inhibition after reinforcement induced by demotivation or temporal control. The size of the ROEs should depend directly on the reinforcement magnitude. The present experiment aimed to clarify the relationship between reinforcement magnitude and the omission effects manipulating the magnitude linked to discriminative stimuli in a partial reinforcement FI schedule. The results showed that response rates were higher after omission than after reinforcement delivery. Besides, response rates were highest immediately after the reinforcement omission of a larger magnitude than of a smaller magnitude. These data are interpreted in terms of ROEs multiple process behavioral facilitation after nonreinforcement, and behavioral transient inhibition after reinforcement.     

Effect of indole-3-acetic acid administration by gavage and by subcutaneous injection on rat leukocytes

This study was done to investigate the effect of indole-3-acetic acid (IAA) administered subcutaneously and by gavage on neutrophil function and cytotoxicity in neutrophils and lymphocytes. A gavage administration resulted in an increase in phagocytic capacity in neutrophils in a dose depended manner for 1 mg, 2 mg, 18 mg, and 40 mg of IAA per kg of body mass, respectively, compared with the control. Similarly, subcutaneous administration of IAA at 2, 18, and 40 mg per kg of body mass promoted a significant rise in phagocytosis by neutrophils. H2O2 production in neutrophils from treated rats by gavage was similar to those receiving subcutaneous IAA treatment, and did not show a significant difference between treatments and control. IAA treatment, whether by gavage or subcutaneous, did not produce an alteration in antioxidant enzyme activities or in glucose-6-phosphate dehydrogenase activity of either neutrophils or lymph nodes. Subcutaneous IAA administration did not alter the neutrophil and lymphocyte death as deduced by unaltered membrane integrity, DNA fragmentation and mitochondrial transmembrane potential, compared with controls. In conclusion, IAA administration either subcutaneously or by gavage could increase the phagocytic capacity by neutrophils and this acid administration did not have prooxidant effects or cytotoxic effects on neutrophils and lymphocytes.     

Cell wall thickenings and tylosoid: developmental morphology reveals novelties for secretory canals in Protium ovatum (Burseraceae)

Journal of Plant Research - We investigated the structure, histochemistry, and ultrastructure of the secretory canals in the vegetative axis of Protium ovatum from a developmental perspective....     

Sampling approaches of the Hindustan citrus mite (Schizotetranychus hindustanicus) in Brazilian citrus orchards and climatic factors affecting its population dynamics

The Hindustan citrus mite, Schizotetranychus hindustanicus (Acari: Tetranychidae), is an invasive pest in South America and constitutes a threat to Brazilian citriculture. This study aimed to determine the contribution of weather variables to the seasonal abundance of S. hindustanicus and the best sampling scheme (sampling variable and unit) for this mite. Populations of S. hindustanicus were monitored monthly in an orange orchard for 31 months in Roraima state, Brazil. Eggs, mobile stages, and the symptoms caused by S. hindustanicus were sampled in different combinations of canopy quadrants, vertical tree strata, and branch sections. The optimal sampling variable and sampling unit for S. hindustanicus scouting were determined according to fidelity and precision criteria. Rainfall and high air temperature were the main factors reducing S. hindustanicus populations. The most suitable variable for S. hindustanicus sampling was egg count. The optimal sampling unit was a leaf collected in the central section of branches located in the middle tree stratum. In addition, the sample should be taken from the southwest quadrant. Collectively, this study adds to the understanding of S. hindustanicus population dynamics and provides a sampling scheme for better management of this pest.

     

Photoperiod modulates growth,morphoanatomy, and linalool content in Lippia alba L. (Verbenaceae) cultured in vitro

Biotechnology provides valuable tools to support conservation of plant species, especially in case of threatened taxa or when dealing with seed unavailability, low viability or sterility. However, plant cell culture methods have often to face problems associated with tissue recalcitrance to in vitro systems. Recalcitrance can be related to a variety of triggering factors, involving many efforts and manipulations within one or more of the micropropagation stages before obtaining successful results. An in vitro propagation protocol was developed for Zelkova sicula, a very rare and endangered relict tree, endemic to Sicily (Southern Italy). The species revealed extremely recalcitrant to in vitro culture approaches, but after many trials throughout a number of years an effective micropropagation protocol was completed. The rooting rate was about 84% of the treated explants, 8% of which were successfully acclimatized outdoor and reintroduced in the wild within a comprehensive conservation project. The technique allowed to overcome the problems of sexual sterility of this species, hence contributing concretely to contrast the problems connected with its conservation. However, additional efforts need to be carried out in order to refine the acclimatization step and further improve the whole process effectiveness.

     

Positive co‐occurrence between feeding‐associative savannah fishes depends on species and habitat

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Association of APOE, GCPII and MMP9 polymorphisms with common diseases and lipid levels in an older adult/elderly cohort

Background and aims

The characterization of candidate gene polymorphisms in elderly populations is an important tool for the identification of risk factors for age-related diseases and conditions. We aimed to genotype the APOE polymorphisms (rs429358 and rs7412), rs61886492 (1561C>T) and rs202720 of GCPII gene and rs3918242 (− 1562C>T) of MMP9 gene in an older-adult/elderly cohort from Cuiabá city, Mato Grosso Brazil as well as to characterize risk factors for morbidities and conditions affecting this cohort.

Methods

The studied population consisted of 570 subjects from Cuiabá city, Brazil, who were subjected to clinical interviews and blood collection for laboratory examinations and DNA extraction. Restriction Fragment Length Polymorphism Polymerase Chain Reaction (RFLP-PCR), sequence-specific primer PCR (SSP-PCR) and TaqMan® allelic discrimination assay were used for genotyping.

Results

The frequencies of APOE ε2 and ε4 were 6.6% and 14.8%, respectively, and the frequencies of GCPII rs61886492 T allele, GCPII rs202720 C allele and MMP9 rs3918242 T allele were, respectively, 3.0%, 26.6% and 10.1%. Significant associations between APOE ε2 allele with lower total cholesterol and LDL-cholesterol were found. In addition, MMP9 rs3918242 T allele was associated with higher LDL-cholesterol levels, suggesting a link between lipid metabolism alteration and cardiovascular disease.

Conclusions

The present findings contributed to characterize risk factors specific for the studied population and to better understand the molecular physiopathology of common morbidities and conditions affecting older-adult/elderly people.     

The Effect of Different Water Immersion Temperatures on Post-Exercise Parasympathetic Reactivation

Purpose

We evaluated the effect of different water immersion (WI) temperatures on post-exercise cardiac parasympathetic reactivation.

Methods

Eight young, physically active men participated in four experimental conditions composed of resting (REST), exercise session (resistance and endurance exercises), post-exercise recovery strategies, including 15 min of WI at 15°C (CWI), 28°C (TWI), 38°C (HWI) or control (CTRL, seated at room temperature), followed by passive resting. The following indices were assessed before and during WI, 30 min post-WI and 4 hours post-exercise: mean R-R (mR-R), the natural logarithm (ln) of the square root of the mean of the sum of the squares of differences between adjacent normal R–R (ln rMSSD) and the ln of instantaneous beat-to-beat variability (ln SD1).

Results

The results showed that during WI mRR was reduced for CTRL, TWI and HWI versus REST, and ln rMSSD and ln SD1 were reduced for TWI and HWI versus REST. During post-WI, mRR, ln rMSSD and ln SD1 were reduced for HWI versus REST, and mRR values for CWI were higher versus CTRL. Four hours post exercise, mRR was reduced for HWI versus REST, although no difference was observed among conditions.

Conclusions

We conclude that CWI accelerates, while HWI blunts post-exercise parasympathetic reactivation, but these recovery strategies are short-lasting and not evident 4 hours after the exercise session.