Airborne bacteria and fungi in a wastewater treatment plant: type and characterization of bio-aerosols,emission characterization and mapping

Aerobiologia - Exposure to bioaerosols causes infection, over-sensitivity, respiratory, and lung diseases. This study was conducted at Sanandaj wastewater treatment plant in three seasons of...     

The p38α mitogen-activated protein kinase is a key regulator of myelination and remyelination in the CNS

The p38α mitogen-activated protein kinase (MAPK) is one of the serine/threonine kinases regulating a variety of biological processes, including cell-type specification, differentiation and migration. Previous in vitro studies using pharmacological inhibitors suggested that p38 MAPK is essential for oligodendrocyte (OL) differentiation and myelination. To investigate the specific roles of p38α MAPK in OL development and myelination in vivo, we generated p38α conditional knockout (CKO) mice under the PLP and nerve/glial antigen 2 (NG2) gene promoters, as these genes are specifically expressed in OL progenitor cells (OPCs). Our data revealed that myelin synthesis was completely inhibited in OLs differentiated from primary OPC cultures derived from the NG2 Cre-p38α CKO mouse brains. Although an in vivo myelination defect was not obvious after gross examination of these mice, electron microscopic analysis showed that the ultrastructure of myelin bundles was severely impaired. Moreover, the onset of myelination in the corpus callosum was delayed in the knockout mice compared with p38α fl/fl control mice. A delay in OL differentiation in the central nervous system was observed with concomitant downregulation in the expression of OPC- and OL-specific genes such as Olig1 and Zfp488 during early postnatal development. OPC proliferation was not affected during this time. These data indicate that p38α is a positive regulator of OL differentiation and myelination. Unexpectedly, we observed an opposite effect of p38α on remyelination in the cuprizone-induced demyelination model. The p38α CKO mice exhibited better remyelination capability compared with p38α fl/fl mice following demyelination. The opposing roles of p38α in myelination and remyelination could be due to a strong anti-inflammatory effect of p38α or a dual reciprocal regulatory action of p38α on myelin formation during development and on remyelination after demyelination.The myelin sheath is the fatty insulating layer that wraps around the axons of the nerves and is critical to the efficient conduction of nerve impulses. It is produced by a specialized glial cell called oligodendrocyte (OL) in the central nervous system (CNS). The proper development of OL and myelination is essential for maintaining the efficiency and speed of electrical nerve impulse. The damage to the developing OL and myelin is a hallmark of many demyelinating and dysmyelinating disorders, including the autoimmune disorders such as multiple sclerosis (MS) as well as periventricular leukomalacia, which is the predominate form of white matter injury seen in premature infants, leading to disability and neurological and cognitive impairments.^{1, 2, 3}Myelination is a complicated process involving generation of OL progenitor cells (OPCs), differentiation of OPCs into myelinating OLs, ensheathment of axons by OLs and finally wrapping the nerves with the expansion of myelin sheath.^{4, 5, 6} The study of intracellular signals that regulate myelinogenesis is crucial to our understanding of the developmental and pathological processes in white matter structures.The mitogen-activated protein kinases (MAPKs) belong to the family of serine/threonine protein kinases that allow cells to respond to stimuli received from their extracellular environment, including mitogens as well as to intracellular stress. The p38 MAPK family members (p38α, p38β, p38γ and p38δ) in particular are implicated in various biological processes, such as cell survival, proliferation and differentiation.^{7, 8, 9, 10} The p38α is well established as a mediator of stress responses in neural cells; however, its physiological role(s) during OL development and myelination has only been recognized recently.^{11, 12, 13, 14, 15, 16} Using p38 inhibitors, several studies have demonstrated that p38α MAPK is important for myelination in cultured Schwann cells¹¹ and OPCs.¹² In addition, p38α has been reported to affect both cell proliferation and glial lineage progression in the presence of growth factors.¹⁷ More recently, Hossain et al.¹⁵ demonstrated that p38α controls Krox-20 to regulate Schwann cell differentiation and peripheral myelination. In contrast, p38 has also been reported as a negative regulator of Schwann cell differentiation and myelination.¹⁶ However, most studies were carried out using in vitro glial cell culture systems and with p38 inhibitors that were not selective for the p38α isoform. The in vivo molecular mechanisms and signaling events by which p38α regulates OPC development and myelination, therefore, remain elusive.In an effort to identify the specific role(s) of p38α in myelination during early postnatal development, we have bred p38α-floxed (p38α fl/fl) mice with nerve/glial antigen 2 (NG2) or proteolipid peptide (PLP)-cre mice to generate homozygous conditional NG2/Plp-specific p38α knockout mice for the first time. Our data showed that p38 α is a positive regulator of OL development and myelination during CNS development as both myelination and OL development were impaired in specific forebrain regions of the conditional knockout (CKO) mice. Surprisingly, we observed an opposite effect of p38α on remyelination in the cuprizone-induced demyelination model. Our findings identified novel reciprocal roles of p38α during OL development in the early postnatal brain and during remyelination in adult mice, implicating the therapeutic potential of p38α inhibition in CNS remyelination.     

Analysis of mitogenic activity of proteins after separation by gel electrophoresis

We have used a combination of gel electrophoresis and a cell culture assay in microplates to analyse mitogenic activity in tissue extracts. The procedure is a modification of the method described by Kuo et al. The proteins were separated by native gel electrophoresis or isoelectric focusing. The gel was sliced and defined pieces were transferred into tissue culture inserts fitting in 96 well microplates, which contained the test cells. The proteins diffused from the gel slices directly into the culture supernatant and the mitogenic effects were evaluated by a colorimetric assay (MTT or phosphatase activity). Human interleukin 2 was used to demonstrate the feasibility of the method by evaluating the mitogenic effect on the cell line CTLL-2. Extracts of bovine pituitary glands were separated by native gel electrophoresis and isoelectric focusing and several protein bands could be identified which showed a distinct mitogenic effect on human endothelial cells. The method is very sensitive and allows rapid screening of protein mixtures for bioactive fractions. This revised version was published online in July 2006 with corrections to the Cover Date.     

A minimal mechanics model for mechanosensing of substrate rigidity gradient in durotaxis

Durotaxis refers to the phenomenon in which cells can sense the spatial gradient of the substrate rigidity in the process of cell migration. A conceptual two-part theory consisting of the focal adhesion force generation and mechanotransduction has been proposed previously by Lo et al. to explain the mechanism underlying durotaxis. In the present work, we are concerned with the first part of the theory: how exactly is the larger focal adhesion force generated in the part of the cell adhering to the stiffer region of the substrate? Using a simple elasticity model and by assuming the cell adheres to the substrate continuously underneath the whole cell body, we show that the mechanics principle of static equilibrium alone is sufficient to account for the generation of the larger traction stress on the stiffer region of the substrate. We believe that our model presents a simple mechanistic understanding of mechanosensing of substrate stiffness gradient at the cellular scale, which can be incorporated in more sophisticated mechanobiochemical models to address complex problems in mechanobiology and bioengineering.     

Earth before life

Background

A recent study argued, based on data on functional genome size of major phyla, that there is evidence life may have originated significantly prior to the formation of the Earth.

Results

Here a more refined regression analysis is performed in which 1) measurement error is systematically taken into account, and 2) interval estimates (e.g., confidence or prediction intervals) are produced. It is shown that such models for which the interval estimate for the time origin of the genome includes the age of the Earth are consistent with observed data.

Conclusions

The appearance of life after the formation of the Earth is consistent with the data set under examination.

Reviewers

This article was reviewed by Yuri Wolf, Peter Gogarten, and Christoph Adami.     

A proteomic study of the major allergens from yellow jacket venoms

The venoms of stinging insects belong to the most dangerous allergen sources and can cause fatal anaphylactic reactions. Reliable prediction of a patient's risk to anaphylactic reactions is vital, and diagnosis requires the knowledge of the relevant allergens. Recently, a new hyaluronidase -like glycoprotein from Vespula vulgaris (Ves v 2b) was identified. This led us to investigate hyaluronidases and also other major allergens from V. germanica and four additional Vespula species. By MALDI-Q-TOF-MS, the new hyaluronidase-like protein was shown to be the major component of the 43-kDa band in all Vespula species studied. LC-ESI-Q-TOF-MS/MS sequencing of Ves g 2a and Ves g 2b facilitated the cloning of their cDNA. Ves v 2b and Ves g 2b turned out to be essentially identical on protein level. Whereas the less abundant "a" form displayed enzymatic activity, the new "b" homologue did not. This is probably caused by amino acid exchanges in the active site, and it raises questions about the physiological role of this protein. Sequence comparisons by MS/MS of antigen 5 and phospholipases from V. vulgaris, germanica, maculifrons, pensylvanica, flavopilosa and squamosa revealed the latter as a taxonomic outlier and led to the discovery of several not previously reported amino acid differences.     

Effects of Bacillus thuringiensis toxin Cry1Ac and cytoplasmic polyhedrosis virus of Helicoverpa armigera (Hübner) (HaCPV) on cotton bollworm (Lepidoptera: Noctuidae)

In this study, interactions on the mortality and debilitating effects between Cry1Ac, a toxic protein produced by Bacillus thuringiensis (Berliner) and HaCPV (Chinese strain) on first and third instars larvae of Helicoverpa armigera were evaluated in laboratory. When first instar was exposed to combination of Bt cotton leaf discs containing HaCPV (6 × 10⁶, 1 × 10⁷, and 3 × 10⁷ PIB ml⁻¹) the effect on mortality was additive, when such instar larvae exposed to combination of Cry1Ac (0.9, 2.7, or 8.1 μg g⁻¹) and the same concentrations of HaCPV the effect on mortality was additive except for the combination of Cry1Ac (0.3 μg g⁻¹) and HaCPV concentrations that showed synergism. When third instars of H. armigera were infected using a suspension containing both HaCPV and Cry1Ac, most combinations of them showed additive effect except for the combination of Cry1Ac (0.3 μg g⁻¹) and HaCPV (3 × 10⁷ PIB ml⁻¹) that showed synergism. However, when they exposed to Bt cotton leaf discs and HaCPV the effect on mortality was synergism except combination of Bt cotton leaf discs and HaCPV (6 × 10⁶ PIB ml⁻¹) that showed additive. Most of the combinations are showed additive effect in the toxicity and in combinations of Cry1Ac at lowest and HaCPV at highest concentrations synergism is observed. Not only were larval growth and development delayed, but pupation and pupal weight also decreased when larvae were fed on artificial diet containing Cry1Ac and HaCPV or transgenic Bt cotton leaf discs specially in first instar.     

Optimising microencapsulated formulation stability of Bacillus thuringiensis subsp. kurstaki (Bt-KD2) against ultraviolet condition using response surface methodology

In this paper, microencapsulated formulation of Bacillus thuringiensis subsp. kurstaki were prepared by the emulsion gelling method. Stability of formulation under ultraviolet (UV) radiation by spore viability and mortality teston Ephestia kuehniella Zeller larvae are investigated. Response surface methodology was used for optimising the formulations. Calcium Chloride (0.1 and 0.3 M) and sodium alginate (2 and 3% w/w) were used in the formulations, and stirring speed was selected between 1500 and 2000 rpm. Morphology of the microcapsule was evaluated by light microscopy. The optimal values for the variables were: sodium alginate = 2.15%, CaCl₂ = 0.24 M, speed = 1606 rpm and spore viability, mortality and diameter of 68% ± 1.73, 85% ± 1.5 and 9μ ± 1.3, respectively; while the predicted values by the software were 70% for spore viability, 87% for mortality and 8.3 μ for diameter.