Effects of Juvenoids and Retinoic Acid on Development of Larvae and Nymphs in the Tick Ixodes ricinus L. (Acari,Ixodidae) and Regeneration of Haller's Organ during Metamorphosis

Larvae and nymphs of the tick Ixodes ricinus L. display similar reactions to analogs of the insect juvenile hormones (methoprene and pyriproxyfen), which induce at both stages juvenalization of the Haller's sense organ regenerates. Similar effects were also described for retinoic acid. Unlike juvenoids, retinoic acid can affect not only regeneration, but also normal development of the Haller's organ and cause changes corresponding to so-called regenerative induction. Amputation of the leg and treatment with retinoic acid do not affect the duration of larval or nymphal development, while juvenoids somewhat accelerate their development.     

Microbial composition affects the functioning of estuarine sediments

Although microorganisms largely drive many ecosystem processes, the relationship between microbial composition and their functioning remains unclear. To tease apart the effects of composition and the environment directly, microbial composition must be manipulated and maintained, ideally in a natural ecosystem. In this study, we aimed to test whether variability in microbial composition affects functional processes in a field setting, by reciprocally transplanting riverbed sediments between low- and high-salinity locations along the Nonesuch River (Maine, USA). We placed the sediments into microbial ‘cages'' to prevent the migration of microorganisms, while allowing the sediments to experience the abiotic conditions of the surroundings. We performed two experiments, short- (1 week) and long-term (7 weeks) reciprocal transplants, after which we assayed a variety of functional processes in the cages. In both experiments, we examined the composition of bacteria generally (targeting the 16S rDNA gene) and sulfate-reducing bacteria (SRB) specifically (targeting the dsrAB gene) using terminal restriction fragment length polymorphism (T-RFLP). In the short-term experiment, sediment processes (CO₂ production, CH₄ flux, nitrification and enzyme activities) depended on both the sediment''s origin (reflecting differences in microbial composition between salt and freshwater sediments) and the surrounding environment. In the long-term experiment, general bacterial composition (but not SRB composition) shifted in response to their new environment, and this composition was significantly correlated with sediment functioning. Further, sediment origin had a diminished effect, relative to the short-term experiment, on sediment processes. Overall, this study provides direct evidence that microbial composition directly affects functional processes in these sediments.     

Effect of of methoprene and retinoic acid on characteristics of Haller's organ regeneration in the tick Haemaphysalis longicornis (Acari, Ixodidae)

The results of experiments on regeneration of the Haller's sensory organ in the metastriate ixodid tick Haemaphysalis longicornis Neumann in the presence of the juvenoid methoprene and retinoic acid and of studies of its structural changes by SEM confirmed the similarity of prostriate and metastriate ixodids as concerns the juvenalizing effect of the above morphogens on regenerative processes during nymphal-imaginal metamorphosis. However, the metastriate ticks (Haemaphysalis and earlier studied Hyalomma) are well behind the prostriate ticks (Ixodes) as concerns the extent of changes induced by juvenoids and retinoids in the sensillar sets of Haller's organ regenerates.     

Photoperiodic Control of Developmental Diapause in Nymphs of Prostriate Ixodid Ticks (Acari: Ixodidae)

Extrinsic control of developmental diapause in nymphs of prostriate ticks of the subgenus Ixodes sensu stricto (Ixodes ricinus and Ixodes persulcatus from Eurasia and Ixodes scapularis from North America) appears to be based on a complex two-step photoperiodic reaction of a short-day/long-day type. Diapause control in the subgenus Afrixodes (the South African tick Ixodes rubicundus) appears to be based on a simple long-day reaction. The option between non-diapause development and diapausing arrest in engorged nymphs is determined by both pre- and post-feeding photoperiodic regimes. Consequently diapausing arrest in engorged nymphs of Ixodes sensu stricto can be induced either by a short-day (after their engorgement) or by a long-day regime (in unfed nymphs), while active, non-diapause development is possible only when the short-day pre-feeding regime is followed by a long-day post-feeding regime. The photoperiodic response in I. (Afrixodes) rubicundus nymphs seems to be of the long-day type both before and after feeding. Consequently this non-diapause development is enabled by a long-day regime, while diapause is induced by a short-day regime of exposure. Nevertheless, there are some indications that the control of nymphal diapause in the latter species is also of a complex nature. This revised version was published online in July 2006 with corrections to the Cover Date.     

Effect of juvenoids and retinoic acid on the development or larva and nymphs of the tick Ixodes ricinus L. (Acari: Ixodidae) and regeneration of Haller's organ during metamorphosis

Larvae and nymphae of the tick Ixodes ricinus L. display similar reactions to analogs of the insect juvenile hormones (methopren and pyriproxyfen), which induce at both stages juvenalization of the Haller's sense organ regenerates. Similar effects were also described for retinoic acid. Unlike juvenoids, retinoic acid can affect not only regeneration, but also normal development of the Haller's organ and cause changes corresponding to so-called regenerative induction. Amputation of the leg and treatment with retinoic acid do not affect the duration of larval or nymphal development, while juvenoids somewhat accelerate their development.     

In Vivo Interaction Proteomics Reveal a Novel p38 Mitogen-Activated Protein Kinase/Rack1 Pathway Regulating Proteostasis in Drosophila Muscle

Several recent studies suggest that systemic aging in metazoans is differentially affected by functional decline in specific tissues, such as skeletal muscle. In Drosophila, longevity appears to be tightly linked to myoproteostasis, and the formation of misfolded protein aggregates is a hallmark of senescence in aging muscle. Similarly, defective myoproteostasis is described as an important contributor to the pathology of several age-related degenerative muscle diseases in humans, e.g., inclusion body myositis. p38 mitogen-activated protein kinase (MAPK) plays a central role in a conserved signaling pathway activated by a variety of stressful stimuli. Aging p38 MAPK mutant flies display accelerated motor function decline, concomitant with an enhanced accumulation of detergent-insoluble protein aggregates in thoracic muscles. Chemical genetic experiments suggest that p38-mediated regulation of myoproteostasis is not limited to the control of reactive oxygen species production or the protein degradation pathways but also involves upstream turnover pathways, e.g., translation. Using affinity purification and mass spectrometry, we identified Rack1 as a novel substrate of p38 MAPK in aging muscle and showed that the genetic interaction between p38b and Rack1 controls muscle aggregate formation, locomotor function, and longevity. Biochemical analyses of Rack1 in aging and stressed muscle suggest a model whereby p38 MAPK signaling causes a redistribution of Rack1 between a ribosome-bound pool and a putative translational repressor complex.     

New aspects in investigations of diapause and non-diapause dormancy types in insects and other arthropods

The paper resumes consideration of the problem posed by the Russian ecologist A.M. Emme (1953) on the need for a comparative study of diapause and quiescence (a non-diapause type of dormancy) in insects and other arthropods. The problem has recently become important due to the scarcity of eco-physiological studies of non-diapause dormancy, whose role in life cycle regulation remains unclear, and to the fact that most attention is now paid to diapause (as the leading adaptation in the control of seasonal development of arthropods). Analysis of data available for insects and acariform mites revealed the prospects of a comprehensive study of non-diapause forms of dormancy known presently (the common stage-independent quiescence, modified stage-specific quiescence, and post-diapause quiescence). The combination of post-diapause quiescence and diapause proper, revealed in many recent insects and acariform mites (mainly Prostigmata), may correspond to the initial ancestral state of dormancy in arthropods, representing a universal adaptation to both predictable and unpredictable environmental changes. This hypothesis gives a reasonable explanation of the possible dual nature of winter dormancy in oribatid mites (in contrast to the existing contradictory interpretations of their hibernal dormancy as only quiescence or only diapause).     

Diminished transmission of drug resistant HIV-1 variants with reduced replication capacity in a human transmission model

Background

Different patterns of drug resistance are observed in treated and therapy naïve HIV-1 infected populations. Especially the NRTI-related M184I/V variants, which are among the most frequently encountered mutations in treated patients, are underrepresented in the antiretroviral naïve population. M184I/V mutations are known to have a profound effect on viral replication and tend to revert over time in the new host. However it is debated whether a diminished transmission efficacy of HIV variants with a reduced replication capacity can also contribute to the observed discrepancy in genotypic patterns.As dendritic cells (DCs) play a pivotal role in HIV-1 transmission, we used a model containing primary human Langerhans cells (LCs) and DCs to compare the transmission efficacy M184 variants (HIV-M184V/I/T) to HIV wild type (HIV-WT). As control, we used HIV harboring the NNRTI mutation K103N (HIV-K103N) which has a minor effect on replication and is found at a similar prevalence in treated and untreated individuals.

Results

In comparison to HIV-WT, the HIV-M184 variants were less efficiently transmitted to CCR5⁺ Jurkat T cells by both LCs and DCs. The transmission rate of HIV-K103N was slightly reduced to HIV-WT in LCs and even higher than HIV-WT in DCs. Replication experiments in CCR5⁺ Jurkat T cells revealed no apparent differences in replication capacity between the mutant viruses and HIV-WT. However, viral replication in LCs and DCs was in concordance with the transmission results; replication by the HIV-M184 variants was lower than replication by HIV-WT, and the level of replication of HIV-K103N was intermediate for LCs and higher than HIV-WT for DCs.

Conclusions

Our data demonstrate that drug resistant M184-variants display a reduced replication capacity in LCs and DCs which directly impairs their transmission efficacy. As such, diminished transmission efficacy may contribute to the lower prevalence of drug resistant variants in therapy naive individuals.

     

Angiographic diagnosis of hemorrhagic myocardial infarct

Hemorrhagic myocardial infarction (HMI) has certain angiographic features that make it possible to diagnose it during the patient's life. HMI angiographic criteria are hypervascularization of an infarction zone in the late arterial phase, an intense contrast of an infarction zone in the parenchymal phase, extravasation of a contrast medium in an infarction zone in the venous phase of coronarography lasting for a long time, and slow discharge of a contrast medium from the distal vascular channel of an infarction zone. HMI characteristic features require thorough phase-by-phase angiographic investigation of the coronary arteries in all MI patients, especially in young ones and those after intracoronary thrombolytic therapy. The detected morphological spasm of microcirculatory vessels and veins disturbing the blood outflow from an infarction zone, noticeable hemorrhages in its interstice prove to be the morphological substantiation of HMI angiographic signs.     

A Study of the Thermophysical Properties of Human Prostate Tumor Tissues in the Temperature Range from–160 to +40°C

Biophysics - A differential scanning calorimetry study of the specific isobaric heat capacity, phase-transition enthalpy, moisture content, and cryoscopic temperature for samples of benign and...