Form and function of the feeding apparatus in Eutardigrada (Tardigrada)

Tardigrade feeding apparatus is a complex structure with considerable taxonomic significance that can be schematically divided into four parts: buccal ring, buccal tube, stylet system, and pharynx. We analyzed the fine morphology and the tridimensional organization of the tardigrade buccal?Cpharyngeal apparatus in order to clarify the relationships between form and function and to identify new characters for systematic and phylogenetic studies. We conducted a comparative analysis of the cuticular structures of the buccal?Cpharyngeal apparatuses of twelve eutardigrade species, integrating data obtained by SEM and LM observations. Morphological diversity was observed and new cuticular structures such as the stylet coat of the stylet system were identified. The synthesis of the buccal?Cpharyngeal apparatus during molting was also analyzed obtaining a clear developmental sequence of its resynthesis. These findings lead us to redefine the previous interpretations of the functioning mechanisms of the buccal?Cpharyngeal apparatus and provide a more specific relationship between tardigrade diet and the anatomy of their feeding apparatuses. In addition, the detection by energy-dispersive X-ray spectroscopy of calcium in the stylets, buccal tube, and placoids of eutardigrade species (i.e., Milnesium tardigradum, Paramacrobiotus richtersi) indicates that CaCO₃ incrustations are not an exclusive feature of heterotardigrades and lead to suppose that this trait was present in the ancestors of both classes.     

A small Tim homohexamer in the relict mitochondrion of Cryptosporidium

The apicomplexan parasite Cryptosporidium parvum possesses a mitosome, a relict mitochondrion with a greatly reduced metabolic capability. This mitosome houses a mitochondrial-type protein import apparatus, but elements of the protein import pathway have been reduced, and even lost, through evolution. The small Tim protein family is a case in point. The genomes of C. parvum and related species of Cryptosporidium each encode just one small Tim protein, CpTimS. This observation challenged the tenet that small Tim proteins are always found in pairs as α3β3 hexamers. We show that the atypical CpTimS exists as a relatively unstable homohexamer, shedding light both on the early evolution of the small Tim protein family and on small Tim hexamer formation in contemporary eukaryotes.     

Decorin protein core inhibits in vivo cancer growth and metabolism by hindering epidermal growth factor receptor function and triggering apoptosis via caspase-3 activation

Decorin is not only a regulator of matrix assembly but also a key signaling molecule that modulates the activity of tyrosine kinase receptors such as the epidermal growth factor receptor (EGFR). Decorin evokes protracted internalization of the EGFR via a caveolar-mediated endocytosis, which leads to EGFR degradation and attenuation of its signaling pathway. In this study, we tested if systemic delivery of decorin protein core would affect the biology of an orthotopic squamous carcinoma xenograft. After tumor engraftment, the animals were given intraperitoneal injections of either vehicle or decorin protein core (2.5-10 mg kg(-1)) every 2 days for 18-38 days. This regimen caused a significant and dose-dependent inhibition of the tumor xenograft growth, with a concurrent decrease in mitotic index and a significant increase in apoptosis. Positron emission tomography showed that the metabolic activity of the tumor xenografts was significantly reduced by decorin treatment. Decorin protein core specifically targeted the tumor cells enriched in EGFR and caused a significant down-regulation of EGFR and attenuation of its activity. In vitro studies showed that the uptake of decorin by the A431 cells was rapid and caused a protracted down-regulation of the EGFR to levels similar to those observed in the tumor xenografts. Furthermore, decorin induced apoptosis via activation of caspase-3. This could represent an additional mechanism whereby decorin might influence cell growth and survival.     

Associations among knee adduction moment, frontal plane ground reaction force, and lever arm during walking in patients with knee osteoarthritis

The adduction moment about the knee during walking gait has been proposed as an indirect measure of dynamic knee joint load. However, the relative contributions of the variables primarily used to calculate the knee adduction moment have not been investigated. The objectives of this paper were to: (1) describe and compare the magnitude and temporal characteristics of the knee adduction moment, frontal plane lever arm, and frontal plane ground reaction force (GRF) during gait in patients with knee osteoarthritis (OA) and, (2) examine the associations among these variables. Results indicated that both the knee adduction moment and the frontal plane GRF varied considerably throughout stance and exhibited the characteristic "double-hump" pattern, while the frontal plane lever arm magnitude varied only slightly during stance. Knees with OA had significantly greater peak knee adduction moments and frontal plane lever arms, but significantly less peak frontal plane GRF than knees without OA. Pearson product moment correlations indicated a higher association between peak knee adduction moment and peak frontal plane lever arm than between peak knee adduction moment and peak frontal plane GRF, particularly in knees with OA. These results suggest that the frontal plane lever arm assessed during walking is an important variable in the examination of knee OA, and warrants further investigation.     

Myostatin negatively regulates the expression of the steroid receptor co-factor ARA70

Myostatin is a transforming growth factor-beta (TGF-beta) superfamily member and a key negative regulator of embryonic and postnatal muscle growth. In order to identify downstream target genes regulated by Myostatin, we performed suppressive subtraction hybridization (SSH) on cDNA generated from the biceps femoris muscle of wild-type and myostatin-null mice. Sequence analysis identified several known and unknown genes as Myostatin downstream target genes. Here, we have investigated the regulation of gene expression of an androgen receptor (AR) binding co-factor, androgen receptor associated protein-70 (ARA70), by Myostatin. We show that in mouse there are two isoforms of ARA70 with high homology (79%) to human ARA70; an alpha-isoform which is a canonical ARA70 and a beta-isoform which has a 9 consecutive amino acid deletion and 6 amino acid substitutions in the carboxyl-terminal portion. Reverse Northern analysis on the differentially expressed cDNA library indicated that there is increased expression of ARA70 in the muscles of myostatin-null mice. In addition, Northern blot, together with semi-quantitative PCR analysis, confirmed that there is increased expression of ARA70 in myostatin-null biceps femoris muscle when compared to wild-type muscle. In corroboration of these results, addition of exogenous Myostatin results in down-regulation of ARA70 expression confirming that Myostatin is a negative regulator of ARA70 gene expression. Expression analysis further confirmed that ARA70 is up-regulated during myogenesis and that peak expression of ARA70 is observed following the peak expression of MyoD in differentiating myoblasts. Given that lack of Myostatin and increased expression of AR leads to hypertrophy, we propose that absence of Myostatin, at least in part, induces the hypertrophy phenotype by increasing the activity of AR by up-regulating the expression of ARA70, a known stimulating co-factor of AR.     

A single P-loop glutamate point mutation to either lysine or arginine switches the cation-anion selectivity of the CNGA2 channel

Cyclic nucleotide-gated (CNG) channels play a critical role in olfactory and visual transduction. Site-directed mutagenesis and inside-out patch-clamp recordings were used to investigate ion permeation and selectivity in two mutant homomeric rat olfactory CNGA2 channels expressed in HEK293 cells. A single point mutation of the negatively charged pore loop (P-loop) glutamate (E342) to either a positively charged lysine or arginine resulted in functional channels, which consistently responded to cGMP, although the currents were generally extremely small. The concentration-response curve of the lysine mutant channel was very similar to that of wild-type (WT) channels, suggesting no major structural alteration to the mutant channels. Reversal potential measurements, during cytoplasmic NaCl dilutions, showed that the lysine and the arginine mutations switched the selectivity of the channel from cations (P(Cl)/P(Na) = 0.07 [WT]) to anions (P(Cl)/P(Na) = 14 [Lys] or 10 [Arg]). Relative anion permeability sequences for the two mutant channels, measured with bi-ionic substitutions, were NO(3)(-) > I(-) > Br(-) > Cl(-) > F(-) > acetate(-), the same as those obtained for anion-selective GABA and glycine channels. The mutant channels also seem to have an extremely small single-channel conductance, measured using noise analysis of about 1-2 pS, compared to a WT value of about 29 pS. The results showed that it is predominantly the charge of the E342 residue in the P-loop, rather than the pore helix dipoles, which controls the cation-anion selectivity of this channel. However, the outward rectification displayed by both mutant channels in symmetrical NaCl solutions suggests that the negative ends of the pore helix dipoles may play a role in reducing the outward movement of Cl(-) ions through these anion-selective channels. These results have potential implications for the determinants of anion-cation selectivity in the large family of P-loop-containing channels.     

Fallopia japonica, an increasingly intractable weed problem in the UK: Can fungi help cut through this Gordian knot?

A new approach to the management of one of the UK's alien superweeds, Japanese knotweed (Fallopia japonica), is currently being investigated. The classical biological control strategy is based on the premise that those neophytes which become invasive and problematic are depauperate in natural enemies, both coevolved and new encounter species. Surveys have confirmed the absence of any significant natural enemy pressure in the UK, and the presence of an extensive guild of specialist arthropod and fungal natural enemies in Japan. The results of these surveys and the follow-up studies in the UK with selected fungi are discussed.