Functional response and egg distribution among hosts by Pseudapanteles dignus,a larval endoparasitoid of Tuta absoluta

The functional response of a biocontrol agent has been classically pointed out as a quantitative evaluation criterion to understand its killing capacity to an arthropod pest. In this paper, we revisited the functional response of the internal larval parasitoid Pseudapanteles dignus (Muesebeck) (Hymenoptera: Braconidae), a candidate for biocontrol of the South American tomato leafminer, Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae), measured as the daily egg oviposition of single parasitoid females at increasing densities of T. absoluta larvae through dissection of hosts. The functional response curve of the number of parasitized hosts was fitted out taking into account the number of eggs laid and their distribution among hosts at each T. absoluta larval density. The data also allowed us to discuss the self-superparasitism strategy of this parasitoid as an adaptive trait. Pseudapanteles dignus showed a sigmoid shape functional response and a contagious distribution of eggs among hosts, favouring self-superparasitism and laying a similar number of eggs in each superparasitized host at each T. absoluta density. This research is firstly intended to ascertain about the oviposition behaviour of P. dignus and additionally to provide information on its reproduction to be applied in mass rearing procedures and augmentative releases against T. absoluta.     

Glycolipid ester-type heterodimers from Ipomoea tyrianthina and their pharmacological activity

Tyrianthins A (1) and B (2), two new partially acylated glycolipid ester-type heterodimers were isolated from Ipomoea tyrianthina. Scammonic acid A was determined as the glycosidic acid in both monomeric units. Tyrianthin A (1) (IC₅₀ 0.24 ± 0.09 μM and E_max 81.80 ± 0.98%), and tyrianthin B (2) (IC₅₀ 0.14 ± 0.08 μM and E_max 87.68 ± 0.72%) showed significant in vitro relaxant effect on aortic rat rings, in endothelium- and concentration-dependent manners. Also, these compounds were able to increase the release of GABA and glutamic acid in brain cortex, and displayed weak antimycobacterial activity.     

Morphology and function of the hyoid apparatus of fossil xenarthrans (mammalia)

The analysis of the hyoid apparatus of fossil xenarthrans provides insight on the form of the tongue and its function in food intake and intraoral processing. The hyoid apparatus of xenarthrans is notable for fusion among its elements. The presence of a V‐bone, a complex consisting of fused basihyal and thyrohyal bones, is a consistent and probably synapomorphic feature of xenarthrans. Fusion of other elements is variable in fossil xenarthrans. Most fossil sloths retain independent elements, as in living dasypodids and mammals generally. Among nothrotheriids, the elements are slender and their articular surfaces indicate considerable mobility, and the relatively long and horizontal orientation of the geniohyoid muscle suggests considerable tongue protrusion. Among mylodontines, such as Paramylodon and Glossotherium, the elements indicate relatively mobile articulations, except between the stylo‐ and epihyals. The relatively posterior placement of the apparatus and the length and alignment of the geniohyoid muscle indicate considerable capacity for tongue protrusion. Scelidotherium, however, had rigidly articulated stylohyal and epihyal, and the apparatus lies farther anteriorly, which together with the elongated, steeply inclined mandibular symphysis, indicates a relatively shorter geniohyoid muscle and thus more limited capacity for tongue protrusion. A similar situation is indicated for Megatherium, casting doubt on the classical reconstruction of this sloth as having a long prehensile tongue. Among cingulates Prozaedyus resembles living dasypodids, indicating considerable tongue protrusion important in food acquisition and intake. More extensive fusion of hyoid elements occurs in the cingulates Glyptodon and Proeutatus, in which the stylohyal and epihyal at least, are fused into a single element termed the sigmohyal. The presence of this element supports recent proposals of a sister‐group relationship between glyptodonts and eutatines. The rigidity of the apparatus suggests limited tongue protrusion, but the tongue, in glyptodonts at least, was a powerful structure important for intraoral manipulation of food. J. Morphol. 271:1119–1133, 2010. © 2010 Wiley‐Liss, Inc.     

Copper accumulation in the aquatic fern Salvinia minima causes more severe physiological stress than zinc

BioMetals - Copper (Cu) and zinc (Zn) have a high demand in the industry. However, these ions, at high concentrations, can cause severe damage to both fauna and flora. Phytoremediation has gained...     

Amino acid change 335 E to K affects the sialic-acid-binding and neuraminidase activities of Urabe AM9 mumps virus hemagglutinin-neuraminidase glycoprotein

A mutation coding for the amino acid change E335 to K is frequently found in the hemagglutinin-neuraminidase (HN) gene of Urabe AM9 mumps viruses isolated during post-vaccination meningitis cases. To identify if this mutation modifies the biological activities of the HN glycoprotein, two variants of Urabe AM9 vaccine differing at amino acid 335 (HN-E335 and HN-K335) were isolated and their receptor-binding specificity was determined by means of competence assays. Pre-incubation of the viruses with sialic acids inhibited both syncytia formation in Vero cells and replication in SH-SY5Y cells. Thus, HN-K335 showed higher affinity towards sialylalpha2,6lactose, whereas HN-G335 preferred sialylalpha2,3lactose. These results are relevant because a high expression of sialylalpha2,6lactose in nerve cells was confirmed by means of Sambucus nigra lectin-cytochemistry. In addition, kinetics assays showed that HN-K335 and HN-E335 also differ in their hydrolysis rate (Vmax values of 37.5 vs. 3.5 nmol min-1mg-1, respectively). Therefore, HN-K335 variant presented a neuraminidase activity level 11-fold higher than that of HN-E335 variant. In conclusion, the mutation affects the receptor-binding and neuraminidase activities of Urabe AM9 mumps virus variants.     

Solution structure and alanine scan of a spider toxin that affects the activation of mammalian voltage-gated sodium channels

Magi 5, from the hexathelid spider Macrothele gigas, is a 29-residue polypeptide containing three disulfide bridges. It binds specifically to receptor site 4 on mammalian voltage-gated sodium channels and competes with scorpion beta-toxins, such as Css IV from Centruroides suffusus suffusus. As a consequence, Magi 5 shifts the activation voltage of the mammalian rNav1.2a channel to more hyperpolarized voltages, whereas the insect channel, DmNav1, is not affected. To gain insight into toxin-channel interactions, Magi 5 and 23 analogues were synthesized. The three-dimensional structure of Magi 5 in aqueous solution was determined, and its voltage-gated sodium channel-binding surfaces were mapped onto this structure using data from electrophysiological measurements on a series of Ala-substituted analogues. The structure clearly resembles the inhibitor cystine knot structural motif, although the triple-stranded beta-sheet typically found in that motif is partially distorted in Magi 5. The interactive surface of Magi 5 toward voltage-gated sodium channels resembles in some respects the Janus-faced atracotoxins, with functionally important charged residues on one face of the toxin and hydrophobic residues on the other. Magi 5 also resembles the scorpion beta-toxin Css IV, which has distinct nonpolar and charged surfaces that are critical for channel binding and has a key Glu involved in voltage sensor trapping. These two distinct classes of toxin, with different amino acid sequences and different structures, may utilize similar groups of residues on their surface to achieve the common end of modifying voltage-gated sodium channel function.     

Intramolecular fluorescence resonance energy transfer between fused autofluorescent proteins reveals rearrangements of the N- and C-terminal segments of the plasma membrane Ca2+ pump involved in the activation

The blue and green fluorescent proteins (BFP and GFP) have been fused at the N- and C-terminal ends, respectively, of the plasma membrane Ca(2+) pump (PMCA) isoform 4xb (hPMCA4xb). The fusion protein was successfully expressed in yeast and purified by calmodulin affinity chromatography. Despite the presence of the fused autofluorescent proteins BFP-PMCA-GFP performed similarly to the wild-type enzyme with respect to Ca(2+)-ATPase activity and sensitivity to calmodulin activation. In the autoinhibited state BFP-PMCA-GFP exhibited a significant intramolecular fluorescence resonance energy transfer (FRET) consistent with the location of the fluorophores at an average distance of 45A. The FRET intensity in BFP-PMCA-GFP decreased when the enzyme was activated either by Ca(2+)-calmodulin, partial proteolysis, or acidic lipids. Moreover, FRET decreased and became insensitive to calmodulin when hPMCA4xb was activated by mutation D170N in BFP-PMCA(D170N)-GFP. The results suggest that the ends of the PMCA are in close proximity in the autoinhibited conformation, and they separate or reorient when the PMCA achieves its final activated conformation.