The controversial origin of the abdominal appendage‐like processes in immature insects: Are they true segmental appendages or secondary outgrowths? (Arthropoda hexapoda)

In this article, I review the major characteristics of different types of appendage‐like processes that develop at the abdominal segments of many immature insects, and I discuss their controversial morphological value. The main question is whether the abdominal processes are derived from segmental appendages serially homologous to thoracic legs, or whether they are “secondary” outgrowths not homologous with true appendages. Morphological and embryological data, in particular, a comparison with the structure and development of the abdominal appendages in primitive apterygote hexapods, and data from developmental genetics, support the hypothesis of appendicular origin of many of the abdominal processes present in the juvenile stages of various pterygote orders. For example, the lateral processes, such as the tracheal gills in aquatic nymphs of exopterygote insects, are regarded as derived from lateral portions of appendage primordia, homologous with the abdominal styli of apterygotan insects; these processes correspond either to rudimentary telopodites or to coxal exites. The ventrolateral processes, such as the prolegs of different endopterygote insect larvae, appear to be derived from medial portions of the appendicular primordia; they correspond to coxal endites. These views lead to the rejection of Hinton's hypothesis (Hinton [1955] Trans R Entomol Soc Lond 106:455–545) according to which all the abdominal processes of insect larvae are secondary outgrowths not derived from true appendage anlagen. J. Morphol. 2012. © 2012 Wiley Periodicals, Inc.     

Temporal variability of top-down forces and their role in host choice evolution of phytophagous arthropods

The role of top-down forces in host choice evolution of phytophagous arthropods is the subject of a vividly animated debate. Empirical evidence for the evolutionary role of top-down forces comes from studies showing that phytophagous arthropods prefer hosts that entail enemy-free space. The aim of this paper is to draw the attention of plant–arthropod researchers to the potentially, temporally variable nature of third trophic level effects. We show that this aspect is largely neglected in studies on enemy-free space, despite the fact that relative enemy impact varies seasonally among plants in at least some studies. We conclude that rigorous testing of the enemy-free space hypothesis can only be performed when within and between season variation in higher trophic level effects is taken into account.     

Application of fluorescence internal transcribed spacer-PCR (f-ITS) for the cluster analysis of bacteria isolated from air and deteriorated fresco surfaces

The aim of this work was the evaluation of fluorescence ITS-PCR (f-ITS) as a molecular tool to analyze the microbial community involved in the biodeterioration of cultural heritage surfaces. As a case study we analyzed by f-ITS ninety-two bacterial strains isolated from a medieval fresco and the surrounding air environment. The internal transcribed spacer between the 16S and 23S rRNA genes was amplified, and then the fluorescently labeled PCR products were separated by capillary electrophoresis. Bacterial strains were identified by 16S rDNA sequencing. The f-ITS electropherograms showed different profiles coherent with the affiliation of the strains at the genus and species levels. Among the isolates obtained from the fresco surface, those belonging to the genus Bacillus were the most prevailing exhibiting 8 different f-ITS profiles. The airborne bacilli exhibited only 2 of these 8 profiles. Staphylococcus were mostly isolated from air and produced 4 different profiles. Pseudomonas isolates presented 3 different profiles, and one of them was typical of Pseudomonas putida. Members of the other genera produced their distinctive profiles. Our results show that f-ITS is a promising molecular tool for the rapid selection and clustering of strains isolated from different sources.     

Target cells infected by avian erythroblastosis virus differentiate and become transformed

Transformation in vitro of bone marrow cells by avian erythroblastosis virus (AEV) gives rise to rapidly growing cells of erythroid nature. Target cells of neoplastic transformation by AEV are recruited among the early progenitors of the erythroid lineage, the burst-forming units-erythroid (BFU-E). They express a brain-related antigen at a high level and an immature antigen at a low level. We show that AEV-transformed cells express low levels of the brain antigen and high levels of the immature antigen. Their response to specific factors regulating the erythroid differentiation indicates that they are very sensitive to erythropoietin. Furthermore, cells transformed by a temperature-sensitive mutant of AEV differentiate into hemoglobin-synthesizing cells 4 days after being shifted to the nonpermissive temperature. All these properties are similar to those of late progenitors of the erythroid lineage, the colony-forming units-erythroid (CFU-E). These results indicate that the AEV-transformed cells are blocked in their differentiation at the CFU-E stage.     

Modelling of the disulphide-swapped isomer of human insulin-like growth factor-1: implications for receptor binding.

Insulin-like growth factor-1 (IGF-1) is a serum protein which unexpectedly folds to yield two stable tertiary structures with different disulphide connectivities; native IGF-1 [18-61,6-48,47-52] and IGF-1 swap [18-61,6-47, 48-52]. Here we demonstrate in detail the biological properties of recombinant human native IGF-1 and IGF-1 swap secreted from Saccharomyces cerevisiae. IGF-1 swap had a approximately 30 fold loss in affinity for the IGF-1 receptor overexpressed on BHK cells compared with native IGF-1.The parallel increase in dose required to induce negative cooperativity together with the parallel loss in mitogenicity in NIH 3T3 cells implies that disruption of the IGF-1 receptor binding interaction rather than restriction of a post-binding conformational change is responsible for the reduction in biological activity of IGF-1 swap. Interestingly, the affinity of IGF-1 swap for the insulin receptor was approximately 200 fold lower than that of native IGF-1 indicating that the binding surface complementary to the insulin receptor (or the ability to attain it) is disturbed to a greater extent than that to the IGF-1 receptor. A 1.0 ns high-temperature molecular dynamics study of the local energy landscape of IGF-1 swap resulted in uncoiling of the first A-region alpha-helix and a rearrangement in the relative orientation of the A- and B-regions. The model of IGF-1 swap is structurally homologous to the NMR structure of insulin swap and CD spectra consistent with the model are presented. However, in the model of IGF-1 swap the C-region has filled the space where the first A-region alpha-helix has uncoiled and this may be hindering interaction of Val44 with the second insulin receptor binding pocket.