Asynchronous development of honey bee host and Varroa destructor (Mesostigmata: Varroidae) influences reproductive potential of mites

A high proportion of nonreproductive (NR) Varroa destructor Anderson & Trueman (Mesostigmata: Varroidae), is commonly observed in honey bee colonies displaying the varroa sensitive hygienic trait (VSH). This study was conducted to determine the influence of brood removal and subsequent host reinvasion of varroa mites on mite reproduction. We collected foundress mites from stages of brood (newly sealed larvae, prepupae, white-eyed pupae, and pink-eyed pupae) and phoretic mites from adult bees. We then inoculated these mites into cells containing newly sealed larvae. Successful reproduction (foundress laid both a mature male and female) was low (13%) but most common in mites coming from sealed larvae. Unsuccessful reproductive attempts (foundress failed to produce both a mature male and female) were most common in mites from sealed larvae (22%) and prepupae (61%). Lack of any progeny was most common for mites from white-eyed (83%) and pink-eyed pupae (92%). We also collected foundress mites from sealed larvae and transferred them to cells containing newly sealed larvae, prepupae, white-eyed pupae, or pink-eyed pupae. Successful reproduction only occurred in the transfers to sealed larvae (26%). Unsuccessful reproductive attempts were most common in transfers to newly sealed larvae (40%) and to prepupae (25%). Unsuccessful attempts involved the production of immature progeny (60%), the production of only mature daughters (26%) or the production of only a mature male (14%). Generally, lack of progeny was not associated with mites having a lack of stored sperm. Our results suggest that mites exposed to the removal of prepupae or older brood due to hygiene are unlikely to produce viable mites if they invade new hosts soon after brood removal. Asynchrony between the reproductive status of reinvading mites and the developmental stage of their reinvasion hosts may be a primary cause of NR mites in hygienic colonies. Even if reinvading mites use hosts having the proper age for infestation, only a minority of them will reproduce.     

Helicobacter Pylori's Plasticity Zones Are Novel Transposable Elements

Background

Genes present in only certain strains of a bacterial species can strongly affect cellular phenotypes and evolutionary potentials. One segment that seemed particularly rich in strain-specific genes was found by comparing the first two sequenced Helicobacter pylori genomes (strains 26695 and J99) and was named a “plasticity zone”.

Principal Findings

We studied the nature and evolution of plasticity zones by sequencing them in five more Helicobacter strains, determining their locations in additional strains, and identifying them in recently released genome sequences. They occurred as discrete units, inserted at numerous chromosomal sites, and were usually flanked by direct repeats of 5′AAGAATG, a sequence generally also present in one copy at unoccupied sites in other strains. This showed that plasticity zones are transposable elements, to be called TnPZs. Each full length TnPZ contained a cluster of type IV protein secretion genes (tfs3), a tyrosine recombinase family gene (“xerT”), and a large (≥2800 codon) orf encoding a protein with helicase and DNA methylase domains, plus additional orfs with no homology to genes of known function. Several TnPZ types were found that differed in gene arrangement or DNA sequence. Our analysis also indicated that the first-identified plasticity zones (in strains 26695 and J99) are complex mosaics of TnPZ remnants, formed by multiple TnPZ insertions, and spontaneous and transposable element mediated deletions. Tests using laboratory-generated deletions showed that TnPZs are not essential for viability, but identified one TnPZ that contributed quantitatively to bacterial growth during mouse infection and another that affected synthesis of proinflammatory cytokines in cell culture.

Conclusions

We propose that plasticity zone genes are contained in conjugative transposons (TnPZs) or remnants of them, that TnPZ insertion is mediated by XerT recombinase, and that some TnPZ genes affect bacterial phenotypes and fitness.     

PHBV‐TiO2 mats prepared by electrospinning technique: Physico‐chemical properties and cytocompatibility

One of the most important challenges in tissue engineering research is the development of biomimetic materials. In this present study, we have investigated the effect of the titanium dioxide (TiO₂) nanoparticles on the properties of electrospun mats of poly (hydroxybutyrate‐co‐3‐hydroxyvalerate) (PHBV), to be used as scaffold. The morphology of electrospun fibers was observed by scanning electron microscopy (SEM). Both pure PHBV and nanocomposites fibers were smooth and uniform. However, there was an increase in fiber diameter with the increase of TiO₂ concentration. Thermal properties of PHBV and nanocomposite mats were characterized by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). DSC analysis showed that the crystallization temperature for PHBV shifts to higher temperature in the presence of the nanoparticles, indicating that TiO₂ nanoparticles change the process of crystallization of PHBV due to heterogeneous nucleation effect. TGA showed that in the presence of the nanoparticles, the curves are shifted to lower temperatures indicating a decreasing in thermal stability of nanocomposites compared to pure PHBV. To produce scaffolds for tissue engineering, it is important to evaluate the biocompatibility of the material. Cytotoxicity assay showed that TiO₂ nanoparticles were not cytotoxic for cells at the concentration used to synthesize the mats. The proliferation of cells on the mats was evaluated by the MTT assay. Results showed that the nanocomposite samples increased cell proliferation compared to the pure PHBV. These results indicate that continuous electrospun fibrous scaffolds may be a good substrate for tissue regeneration.     

Improvement in the high-performance liquid chromatography malondialdehyde level determination in normal human plasma

We report a very rapid and simple isocratic reversed-phase HPLC separation of malondialdehyde (MDA) in normal human plasma without previous purification of the MDA–2-thiobarbituric acid (TBA) complex. The separation of MDA–TBA complex was performed using a 250×4.6 mm Nucleosil-5C18 column with a mobile phase composed of 35% methanol and 65% 50 mM sodium phosphate buffer, pH 7.0. Samples of 50 μl (composed of 100 μl plasma mixed with 1.0 ml of 0.2% 2-thiobarbituric acid in 2 M sodium acetate buffer containing 1 mM diethylenetriaminepentaacetic acid, pH 3.5, and 10 μl of 5% 2,6-di-tert.-butyl-4-methylphenol in 96% ethanol, incubated at 95°C for 45 min [K. Fukunaga, K. Takama and T. Suzuki, Anal. Biochem., 230 (1995) 20] were injected into the column. The MDA–TBA complex was eluted at a flow-rate of 1 ml/min and monitored by fluorescence detection with excitation at 515 nm and emission at 553 nm. Analysis of groups of normal male and female volunteers gave plasma levels of MDA of 1.076 nmol/ml with a coefficient of variation of about 58%. No significant statistical differences were found between male and female groups, and no correlation was discovered on the age.     

Cannabinoid induced degranulation of rabbit neutrophils

We have examined the effects of various cannabinoids on the degranulation of rabbit peritoneal neutrophils. Several cannabinoids were found to cause a dose-dependent and noncytotoxic release of lysosomal enzymes from the neutrophils. The degranulation induced by cannabidiol is rapid ($\text{t}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{= 2.3 min}$), and enhanced by extracellular calcium and cytochalasin B. In addition to their intrinsic activity, cannabinoids also modulate the neutrophils' responses to the chemotactic peptide formyl-methionyl-leucyl-phenylalanine. This investigation represents the initial step toward the characterization of the effect of cannabinoids on the excitation-activation coupling sequence of hormonally responsive cells.     

Male-Induced Sociosexual Behavior by Vaginal Secretions in Macaca arctoides

Odor communication in Old World monkeys and apes is controversial, because most females have evolved visual and behavioral cues to signal fertility, e.g., sexual swellings. Female stump-tailed macaques (Macaca arctoides) do not have swellings, and mediation of chemical communication likely occurs because males engage in sexual behavior mostly throughout the periovulatory phase of the menstrual cycle. We tested whether vaginal secretions from different cycle phases, with saline solution as a control, promote changes in the frequency of male genital exploration, copulation, and coercive behavior toward females different from the donors, while female donors were apart from the group. Males explored more female genitals when exposed to follicular, periovulatory, and early luteal secretions in comparison to saline or menstrual or late luteal secretions. The increase in coercive behavior after exposure to follicular and periovulatory secretions most likely was a male response to the lack of cooperation of target females in engaging in copulation, as the latter were not receptive during the tests. The strength of male response to vaginal secretions varied significantly as a result of individual variability between donor females, yet the variability does not correlate either to dominance rank or to female age. Exploratory behavior of males correlates significantly with their social rank. Our results suggest that vaginal secretions are among the cues that male Macaca arctoides use to acknowledge the reproductive status of females in the absence of visual signals.     

Reduction of baclofen-, but not sodium valproate-induced growth hormone release in type I diabetic men.

The effects of sodium valproate (a drug enhancing endogenous gamma aminobutyric acid (GABA)-ergic activity) and of the GABA analog baclofen (a GABA B receptor agonist) on serum GH levels was tested in 8 type I diabetic men and 8 normal controls. Sodium valproate (800 mg) or baclofen (10 mg) were given by mouth at 08.30 h on the experimental day. Control tests with a placebo were performed on different occasions. Basal GH levels were similar in controls and diabetic patients. Sodium valproate induced a 7 fold increase in serum GH concentrations in both groups. In contrast, baclofen-induced GH rise was significantly higher in normal controls (mean peak was 3.4 times higher than baseline) than in diabetic patients (mean peak was only 2.1 times higher than basal value). Serum GH levels did not change after placebo administration in any groups. These data suggest the presence of diabetes-induced alterations of a GABAergic pathway mediated by B receptors in the control of GH secretion. Alternatively, the data might indicate a change in diabetic men of other baclofen-sensitive neurotransmissions, different from GABA.