Interspecific relationships in co‐occurring populations of social parasites and their host ants

Myrmica ant colonies host numerous insect species, including the larvae of Maculinea butterflies and Microdon myrmicae hoverflies. Little is known about the interspecific relationships among these social parasites and their host ants occurring in sympatric populations. We investigated communities of social parasites to assess the strategies allowing them to share the same pool of resources (i.e. Myrmica colonies). The present study was carried out at five sites inhabited by different social parasite communities, each comprising varying proportions of Maculinea teleius, Maculinea nausithous, Maculinea alcon, and Microdon myrmicae. We investigated their spatial distributions, host segregation, the degree of chemical similarity between social parasites and hosts, and temporal overlaps in colony resource exploitation. Spatial segregation among social parasites was found in two populations and it arises from microhabitat preferences and biological interactions. Local conditions can drive selection on one social parasite to use a Myrmica host species that is not exploited by other social parasites. Myrmica scabrinodis and Myrmica rubra nests infested by larvae of two social parasite species were found and the most common co‐occurrence was between Ma. teleius and Mi. myrmicae. The successful coexistence of these two species derives from their exploitation of the host colony resources at different times of the year. © 2013 The Linnean Society of London, Biological Journal of the Linnean Society, 2013, 109 , 699–709.     

Effects of TNF-alpha/colchicine combined treatment on Burkitt lymphoma cells: molecular and ultrastructural changes

Tumour necrosis factor alpha (TNF-alpha) kills Daudi cells (Human Burkitt Lymphoma), inducing either necrosis or apoptosis without DNA fragmentation. Therefore, we were interested in studying the molecular and ultrastructural events occurring when the nucleus is more accessible and cells are blocked in mitosis, following colchicine treatment. In fact, as early as after 1 h treatment a typical ladder pattern was shown by means of DNA gel electrophoresis. In parallel the quantitative analysis of the different morphological patterns observed gave evidence of an increased percentage of primary necrosis after 6 h treatment, and a higher incidence of cells in late apoptosis as well as in secondary necrosis after 24 h treatment. Our findings show that Daudi cells respond to the combined treatment with an increased formation of micronuclei and nuclear alterations which follow a number of early mitochondrial changes and result in enhanced cell death. These data imply that TNF-alpha-induced apoptosis of Daudi cells can be triggered by mitochondrial changes and is somehow related to microtubule organization.     

In vitro exposure of human lymphocytes to 900 MHz CW and GSM modulated radiofrequency: studies of proliferation, apoptosis and mitochondrial membrane potential

The aim of this study was to investigate the nonthermal effects of radiofrequency (RF) fields on human immune cells exposed to a Global System for Mobile Communication (GSM) signal generated by a commercial cellular phone and by a sinusoidal non-modulated signal. To assess whether mobile phone RF-field exposure affects human immune cell functions, peripheral blood mononuclear cells (PBMCs) from healthy donors were exposed in vitro to a 900 MHz GSM or continuous-wave (CW) RF field 1 h/day for 3 days in a transverse electromagnetic mode (TEM) cell system (70-76 mW/kg average specific absorption rate, SAR). The cells were cultured for 48 or 72 h, and the following end points were studied: (1) mitogen-induced proliferation; (2) cell cycle progression; (3) spontaneous and 2-deoxy-D-ribose (dRib)-induced apoptosis; (4) mitochondrial membrane potential modifications during spontaneous and dRib-induced-apoptosis. Data obtained from cells exposed to a GSM-modulated RF field showed a slight decrease in cell proliferation when PBMCs were stimulated with the lowest mitogen concentration and a slight increase in the number of cells with altered distribution of phosphatidylserine across the membrane. On the other hand, cell cycle phases, mitochondrial membrane potential and susceptibility to apoptosis were found to be unaffected by the RF field. When cells were exposed to a CW RF field, no significant modifications were observed in comparison with sham-exposed cells for all the end points investigated.     

Effect of sex on counterregulatory responses to exercise after antecedent hypoglycemia in type 1 diabetes

A marked sexual dimorphism exists in healthy individuals in the pattern of blunted neuroendocrine and metabolic responses following antecedent stress. It is unknown whether significant sex-related counterregulatory differences occur during prolonged moderate exercise after antecedent hypoglycemia in type 1 diabetes mellitus (T1DM). Fourteen patients with T1DM (7 women and 7 men) were studied during 90 min of euglycemic exercise at 50% maximal O(2) consumption after two 2-h episodes of previous-day euglycemia (5.0 mmol/l) or hypoglycemia of 2.9 mmol/l. Men and women were matched for age, glycemic control, duration of diabetes, and exercise fitness and had no history or evidence of autonomic neuropathy. Exercise was performed during constant "basal" intravenous infusion of regular insulin (1 U/h) and a 20% dextrose infusion, as needed to maintain euglycemia. Plasma glucose and insulin levels were equivalent in men and women during all exercise and glucose clamp studies. Antecedent hypoglycemia produced a relatively greater (P < 0.05) reduction of glucagon, epinephrine, norepinephrine, growth hormone, and metabolic (glucose kinetics) responses in men compared with women during next-day exercise. After antecedent hypoglycemia, endogenous glucose production (EGP) was significantly reduced in men only, paralleling a reduction in the glucagon-to-insulin ratio and catecholamine responses. In conclusion, a marked sexual dimorphism exists in a wide spectrum of blunted counterregulatory responses to exercise in T1DM after prior hypoglycemia. Key neuroendocrine (glucagon, catecholamines) and metabolic (EGP) homeostatic responses were better preserved during exercise in T1DM women after antecedent hypoglycemia. Preserved counterregulatory responses during exercise in T1DM women may confer greater protection against hypoglycemia than in men with T1DM.     

The solution structure of ChaB,a putative membrane ion antiporter regulator from <Emphasis Type="Italic">Escherichia coli</Emphasis>

Background  

ChaB is a putative regulator of ChaA, a Na⁺/H⁺ antiporter that also has Ca⁺/H⁺ activity in E. coli. ChaB contains a conserved 60-residue region of unknown function found in other bacteria, archaeabacteria and a series of baculoviral proteins. As part of a structural genomics project, the structure of ChaB was elucidated by NMR spectroscopy.     

Platelet aggregation and antibacterial effects of an l-amino acid oxidase purified from Bothrops alternatus snake venom

The isolation and biochemical/enzymatic characterization of an L-amino acid oxidase, Balt-LAAO-I, from Bothrops alternatus snake venom, is described. Balt-LAAO-I is an acidic glycoprotein, pI approximately 5.37, homodimeric, Mr approximately 123,000, whose N-terminal sequence is ADVRNPLE EFRETDYEVL. It displays a high specificity toward hydrophobic and basic amino acids, while deglycosylation does not alter its enzymatic activity. Balt-LAAO-I induces platelet aggregation and shows bactericidal activity against Escherichia coli and Staphylococcus aureus. In addition, this enzyme is slightly hemorrhagic and induces edema in the mouse paw. Balt-LAAO-I is a multifunctional enzyme with promising relevant biotechnological and medical applications.     

In vitro effect of indomethacin and interferon-alpha on Th1 and Th2 cytokine synthesis in patients with chronic hepatitis C

Current evidences suggest that non-steroidal anti-inflammatory drugs could enhance the antiviral activity of interferon-alpha in chronic HCV infection. In this study, we investigated the effect of indomethacin, a non-steroidal anti-inflammatory drug, and interferon-alpha on cytokine production by peripheral blood mononuclear cells from 12 untreated patients with chronic hepatitis C. We evaluated the effect of incubation with indomethacin, interferon-alpha or both on synthesis of Th1- (interleukin-2, interferon-gamma) and Th2-associated cytokines (interleukin-4, interleukin-10), and of the antiviral protein 2',5'-oligoadenylate synthetase. Interferon-alpha induced a significant increase in production of interleukin-2. Smaller increases were also seen in the presence of indomethacin, while incubation with both indomethacin and interferon-alpha leads to a synergistic effect. Incubation with indomethacin decreased both interleukin-4 and interleukin-10, whereas interferon-alpha increased these cytokines. The addition of indomethacin to interferon-alpha significantly reversed this interferon-induced increase. Finally, both indomethacin and the association interferon-alpha plus indomethacin determined a significant increase in 2',5'-oligoadenylate synthetase production compared to both baseline and interferon-alpha alone. In conclusion, indomethacin was able to enhance the antiviral activity of interferon-alpha and to modulate the interferon-induced Th1 and Th2 cytokine response by increasing the Th1-response, fundamental for sustained clearance of HCV, and by decreasing the Th-2 type response, associated with HCV persistence.     

IS<Emphasis Type="Italic">Rm31</Emphasis>, a new insertion sequence of the IS<Emphasis Type="Italic">66</Emphasis> family in<Emphasis Type="Italic"> Sinorhizobium meliloti</Emphasis>

Sinorhizobium meliloti natural populations show a high level of genetic polymorphism possibly due to the presence of mobile genetic elements such as insertion sequences (IS), transposons, and bacterial mobile introns. The analysis of the DNA sequence polymorphism of the nod region of S. meliloti pSymA megaplasmid in an Italian isolate led to the discovery of a new insertion sequence, ISRm31. ISRm31 is 2,803 bp long and has 22-bp-long terminal inverted repeat sequences, 8-bp direct repeat sequences generated by transposition, and three ORFs (A, B, C) coding for proteins of 124, 115, and 541 amino acids, respectively. ORF A and ORF C are significantly similar to members of the transposase family. Amino acid and nucleotide sequences indicate that ISRm31 is a member of the IS66 family. ISRm31 sequences were found in 30.5% of the Italian strains analyzed, and were also present in several collection strains of the Rhizobiaceae family, including S. meliloti strain 1021. Alignment of targets sites in the genome of strains carrying ISRm31 suggested that ISRm31 inserts randomly into S. meliloti genomes. Moreover, analysis of ISRm31 insertion sites revealed DNA sequences not present in the recently sequenced S. meliloti strain 1021 genome. In fact, ISRm31 was in some cases linked to DNA fragments homologous to sequences found in other rhizobia species.