VNTR analysis reveals unexpected genetic diversity within <Emphasis Type="Italic">Mycoplasma agalactiae</Emphasis>, the main causative agent of contagious agalactia

Background  

Mycoplasma agalactiae is the main cause of contagious agalactia, a serious disease of sheep and goats, which has major clinical and economic impacts. Previous studies of M. agalactiae have shown it to be unusually homogeneous and there are currently no available epidemiological techniques which enable a high degree of strain differentiation.     

Streptomyces scabies 87-22 possesses a functional tomatinase

The actinomycete Streptomyces scabies 87-22 is the causal agent of common scab, an economically important disease of potato and taproot crops. Sequencing of the S. scabies 87-22 genome revealed the presence of a gene with high homology to the gene encoding the alpha-tomatine-detoxifying enzyme tomatinase found in fungal tomato pathogens. The tomA gene from S. scabies 87-22 was cotranscribed with a putative family 1 glycosyl hydrolase gene, and purified TomA protein was active only on alpha-tomatine and not potato glycoalkaloids or xylans. Tomatinase-null mutants were more sensitive to alpha-tomatine than the wild-type strain in a disk diffusion assay. Interestingly, tomatine affected only aerial mycelium and not vegetative mycelium, suggesting that the target(s) of alpha-tomatine is not present during vegetative growth. Severities of disease for tomato seedlings affected by S. scabies 87-22 wild-type and DeltatomA1 strains were indistinguishable, suggesting that tomatinase is not important in pathogenicity on tomato plants. However, conservation of tomA on a pathogenicity island in S. acidiscabies and S. turgidiscabies suggests a role in plant-microbe interaction.     

Follow-up of children born of bromocriptine-treated mothers

A survey carried out in France at the beginning of 1984 concerning development of children born of mothers treated with bromocriptine (BC) during part or all of the pregnancy showed the absence of any adverse effects of BC in 64 children born from 53 mothers. In 60 cases, BC was prescribed (2.5-7.5 mg/day) for hyperprolactinemia; 23 mothers were treated with BC for 4 weeks or less, and 23 others for 30 weeks or more. After a follow-up of between 6 months and 9 years, all children are normal. Psychological development in the 23 children born to mothers treated with BC during more than 30 weeks of pregnancy actually appears more precocious, with excellent scholastic performance in the oldest.     

Linking fisheries management and conservation in bioengineering species: the case of South American mussels (Mytilidae)

We examined a complete list of South American mussels (Mytilidae) to identify species with current or potential needs for management and conservation actions. Based on ecological/ecosystem (aggregations, beds or banks affecting ecosystem functioning) and socio-economic (artisanal fisheries or aquaculture systems) attributes species with high relevance were identified. At least 14 species exhibited large ecosystem level effects at local scales. Further, most of them also sustain important fisheries: nearly one/third of these fisheries showed characteristics that may contribute to their lack of sustainability and overexploitation, while half are either in the initial exploitation phase or in the stabilization of extraction and institutionalization phase. Invading species are modifying the structure of mussel habitats. Allocation of spatially explicit management tools, notably Territorial User Rights in Fisheries and Marine Reserves, together with co-management initiatives, are suggested as relevant tools to fulfill management and conservation objectives for these key bioengineering species.     

Group IV Phospholipase A2α Controls the Formation of Inter-Cisternal Continuities Involved in Intra-Golgi Transport

The organization of intra-Golgi trafficking and the nature of the transport intermediates involved (e.g., vesicles, tubules, or tubular continuities) remain incompletely understood. It was recently shown that successive cisternae in the Golgi stack are interconnected by membrane tubules that form during the arrival of transport carriers from the endoplasmic reticulum. Here, we examine the mechanisms of generation and the function of these tubules. In principle, tubule formation might depend on several protein- and/or lipid-based mechanisms. Among the latter, we have studied the phospholipase A₂ (PLA₂)-mediated generation of wedge-shaped lysolipids, with the resulting local positive membrane curvature. We show that the arrival of cargo at the Golgi complex induces the recruitment of Group IVA Ca²⁺-dependent, cytosolic PLA₂ (cPLA₂α) onto the Golgi complex itself, and that this cPLA₂α is required for the formation of the traffic-dependent intercisternal tubules and for intra-Golgi transport. In contrast, silencing of cPLA₂α has no inhibitory effects on peri-Golgi vesicles. These findings identify cPLA₂α as the first component of the machinery that is responsible for the formation of intercisternal tubular continuities and support a role for these continuities in transport through the Golgi complex.     

Enzyme dynamics along the reaction coordinate: critical role of a conserved residue

Conformational flexibility of the enzyme architecture is essential for biological function. These structural transitions often encompass significant portions of the enzyme molecule. Here, we present a detailed study of functionally relevant RNase A dynamics in the wild type and a D121A mutant form by NMR spin-relaxation techniques. In the wild-type enzyme, the dynamic properties are largely conserved in the apo, enzyme-substrate, and enzyme-product complexes. In comparison, mutation of aspartic acid 121 to alanine disrupts the timing of active-site dynamics, the product-release step, and global conformational changes, indicating that D121 plays a significant role in coordinating the dynamic events in RNase A. In addition, this mutation results in 90% loss of catalytic activity despite the absence of direct participation of D121 in the chemical reaction or in interactions with the substrate. These data suggest that one role of this conserved residue is to facilitate important millisecond protein dynamics.     

Species-specific chemosignals evoke delayed excitation of the vomeronasal amygdala in freely-moving female rats

Male rat chemosignals attract females and influence their reproductive status. Through the accessory olfactory bulb and its projection target, the posteromedial cortical nucleus of the amygdala (PMCo), species-specific chemosignals detected by the vomeronasal organ (VNO) may reach the hypothalamus. To test this hypothesis in vivo, behavioural activation and neurotransmitter release in the PMCo were simultaneously monitored in freely moving female oestrus rats exposed to either rat or mouse urinary stimuli, or to odorants. Plasma levels of the luteinizing hormone were subsequently monitored. All stimuli induced an immediate behavioural activation, but only species-specific chemosignals led to a delayed behavioural activation. This biphasic behavioural activation was accompanied by a VNO-mediated release of the excitatory amino acids, aspartate and glutamate, in the PMCo. The late behavioural and neurochemical activation was followed by an increase in the levels of circulating luteinizing hormone. In conclusion, these data show that only species-specific chemosignals induce a delayed behavioural activation and excitatory activation of the PMCo, which is dependent on an intact VNO.     

The cleavage step of ribonuclease P catalysis is determined by ribozyme-substrate interactions both distal and proximal to the cleavage site.

The cleavage step of bacterial RNase P catalysis involves concentration-independent processes after the formation of the ribozyme-substrate complex that result in the breaking of a phosphodiester bond. The 2'OH group at the cleavage site of a pre-tRNA substrate is an important determinant in the cleavage step. We determined here that in contrast to a tRNA substrate, the 2'OH at the cleavage site of two in vitro selected substrates has no effect, whereas a 2'OH located adjacent to the cleavage site has a similarly large effect on the cleavage step. This result indicates that a unique 2'OH in the vicinity of the cleavage site interacts with the ribozyme to achieve the maximal efficiency of the cleavage step. Individual modifications in a pre-tRNA substrate that disrupt ES interactions proximal to the cleavage site generally have little effect on the usage of this unique 2'OH. Ribozyme modifications that delete the interactions involving the T stem-loop of the tRNA have a large effect on the usage of this unique 2'OH and also alter the location of this 2'OH. We propose a new ES complex prior to the bond-breaking step in the reaction scheme to explain these results. This second ES complex is in fast equilibrium with the initial ES complex formed by bimolecular collision. The ribozyme interaction with this unique 2'OH shifts the equilibrium in favor of the second ES complex. The formation of the second ES complex may require optimal geometry of the two independently folding domains of this ribozyme to precisely position crucial functional groups and Mg2+ ions in the active site. Such a domain geometry is significantly favored by the RNase P protein. In the absence of the protein, spatial rearrangement of these domains in the ES complex may be necessary.