Structural and gene expression analyses of uptake hydrogenases and other proteins involved in nitrogenase protection in Frankia

The actinorhizal bacterium Frankia expresses nitrogenase and can therefore convert molecular nitrogen into ammonia and the by-product hydrogen. However, nitrogenase is inhibited by oxygen. Consequently, Frankia and its actinorhizal hosts have developed various mechanisms for excluding oxygen from their nitrogen-containing compartments. These include the expression of oxygen-scavenging uptake hydrogenases, the formation of hopanoid-rich vesicles, enclosed by multi-layered hopanoid structures, the lignification of hyphal cell walls, and the production of haemoglobins in the symbiotic nodule. In this work, we analysed the expression and structure of the so-called uptake hydrogenase (Hup), which catalyses the in vivo dissociation of hydrogen to recycle the energy locked up in this ‘waste’ product. Two uptake hydrogenase syntons have been identified in Frankia: synton 1 is expressed under free-living conditions while synton 2 is expressed during symbiosis. We used qPCR to determine synton 1 hup gene expression in two Frankia strains under aerobic and anaerobic conditions. We also predicted the 3D structures of the Hup protein subunits based on multiple sequence alignments and remote homology modelling. Finally, we performed BLAST searches of genome and protein databases to identify genes that may contribute to the protection of nitrogenase against oxygen in the two Frankia strains. Our results show that in Frankia strain ACN14a, the expression patterns of the large (HupL1) and small (HupS1) uptake hydrogenase subunits depend on the abundance of oxygen in the external environment. Structural models of the membrane-bound hydrogenase subunits of ACN14a showed that both subunits resemble the structures of known [NiFe] hydrogenases (Volbeda et al. 1995), but contain fewer cysteine residues than the uptake hydrogenase of the Frankia DC12 and Eu1c strains. Moreover, we show that all of the investigated Frankia strains have two squalene hopane cyclase genes (shc1 and shc2). The only exceptions were CcI3 and the symbiont of Datisca glomerata, which possess shc1 but not shc2. Four truncated haemoglobin genes were identified in Frankia ACN14a and Eu1f, three in CcI3, two in EANpec1 and one in the Datisca glomerata symbiont (Dg).     

The genetic legacy of the 19th‐century decline of the British polecat: evidence for extensive introgression from feral ferrets

In the 19th century, the British polecat suffered a demographic contraction, as a consequence of direct persecution, reaching its lowest population in the years that preceded the First World War. The polecat is now recovering and expanding throughout Britain, but introgressive hybridization with feral ferrets has been reported, which could be masking the true range of the polecat and introducing domestic genes into the species. We used a fragment of the mitochondrial DNA control region and 11 microsatellite loci to characterize the frequency and extent of hybridization and introgression between the two species and assess whether the 19th‐century decline corresponded to a genetic bottleneck in the polecat. The proportion of admixture detected in the wild was high (31%) and hybrids were more frequently found outside Wales, suggesting that hybridization is more likely to occur along the eastern edge of the polecat's range expansion. The patterns observed in the mitochondrial and nuclear DNA data show that introgression was mediated by crosses between male polecats and female ferrets, whose offspring backcrossed with polecats. No first‐generation (F₁) hybrids were identified, and the broad range of observed admixture proportions agrees with a scenario of past extensive hybridization between the two species. Using several different methods to investigate demographic history, we did not find consistent evidence for a genetic bottleneck in the British polecat, a result that could be interpreted as a consequence of hybridization with ferrets. Our results highlight the importance of the Welsh polecat population for the conservation and restoration of the genetic identity of the British polecat.     

Recognition memory and the human hippocampus

The capacity for declarative memory depends on the hippocampal region and adjacent cortex within the medial temporal lobe. One of the most widely studied examples of declarative memory is the capacity to recognize recently encountered material as familiar, but uncertainty remains about whether intact recognition memory depends on the hippocampal region itself and, if so, what the nature of the hippocampal contribution might be. Seven patients with bilateral damage thought to be limited primarily to the hippocampal region were impaired on three standard tests of recognition memory. In addition, the patients were impaired to a similar extent at Remembering and Knowing, measures of the two processes thought to support recognition performance: the ability to remember the learning episode (episodic recollection) and the capacity for judging items as familiar (familiarity).     

Colposcopy in a family planning clinic: a future model?

The first year''s experience of a satellite colposcopy clinic in the Glasgow Family Planning Centre was analysed. Establishment of the clinic was supervised by an experienced member of the colposcopy team at the department of gynaecology, Western Infirmary, Glasgow, who trained one of the family planning centre''s staff. Close links were thus maintained with the hospital clinic to which patients were referred for treatment. The policy at the new colposcopy clinic was to study prospectively all women in the hospital catchment area whose cervical smears were reported as abnormal. In 58 of 162 such patients there was at least moderate dyskaryosis and the cytologist''s recommendation had been referral for colposcopy. In 104 cases the changes were either atypia alone or mild dyskaryosis and a repeat smear was recommended within three to 12 months; 18 of these patients had grade II or III cervical intraepithelial neoplasia on biopsy, and relying on repeat smears would have resulted in an 11.7% false negative rate. If an atypical cytological picture is to be an indication for colposcopy clinics attached to family planning centres may have an important role, given satisfactory training and close links with central specialist colposcopy clinics.     

Guest Lecture 9.45–10.30 Wednesday 17 September 2003. Csp Colposcopy Guidelines

The success of the Cervical Screening Programme (CSP) is due in part to its management being underpinned by Quality Assurance. These measures ensure uniform standards across the country. Since 1992 Colposcopy Guidelines have been in place; these were updated in 1997 and have just been redefined. It is entirely consistent with the National CSP that colposcopy is governed by Guidelines. The aim of clinical practice guidelines is to raise the standard of care and improve outcomes. The objectives are, therefore:

• a) to develop evidence based guidelines;
• b) to ensure the guidelines are widely adopted.

The credibility of guidelines is crucial to their adoption and this depends far more on the demonstration of an evidence base than that the authors are ‘experts’. Development by a professional group or body who are seen as having a legitimate role is very important as is involvement of all ‘stakeholders’ in ensuring acceptability. In terms of their nature, guidelines should be valid i.e. they will achieve what they are intended to achieve, and they should be robust i.e. they will work when implemented by different individuals in different settings. Colposcopy lends itself well to guidelines because it is largely a routine practice, but substandard care can have serious consequences. In previous years there has been a set of Guidelines for Practice ^1, 1Duncan 1992 ² 2Duncan 1995 and a set of Quality Standards ³ 3Luesley 1996 . On this occasion these two components have been put together in a simple publication. It needs to be borne in mine that the new guidelines were being developed in the context of a number of potential changes which could interact with each other and impact on the Guidelines. These include: The process for the development of the Guidelines included an Editor, an editorial group, and a group of contributors to produce a draft set of evidence based guidelines across 18 areas. New areas covered included HIV +ve women, immuno suppressed women, and working practice. The draft has been available for comment for several months and amendments have been made. Clearly there are areas where evidence is lacking and where different views are expressed. The most contentious area not surprisingly is in the topic of managing mild dyskaryosis; controversy in this has persisted for many years. The quality standards are either attainable or within attainment and are a driver for rising standards. These programme practice guidelines and standards have earned UK colposcopy international respect. They provide a benchmark for QA assessment and will continue to require amendment as new developments come into being.     

Disruption of the CRF/CRF1 receptor stress system exacerbates the somatic signs of opiate withdrawal

Escape from the extremely stressful opiate withdrawal syndrome may motivate opiate seeking and taking. The corticotropin-releasing factor receptor-1 (CRF1) pathway mediates behavioral and endocrine responses to stress. Here, we report that genetic inactivation (CRF1-/-) as well as pharmacological antagonism of the CRF/CRF1 receptor pathway increased and prolonged the somatic expression of opiate withdrawal. Opiate-withdrawn CRF1-/- mice also showed aberrant CRF and dynorphin expression in the paraventricular nucleus of the hypothalamus (PVN) and the striatum, indicating profound impairments in stress-responsive brain circuitry. Intake of nonstressful amounts of corticosterone effectively reduced the exaggerated somatic reactions of CRF1-/- mice to opiate withdrawal. Exogenous corticosterone also restored "wild-type-like" patterns of CRF and dynorphin gene expression in the PVN and the striatum of opiate-withdrawn CRF1-/- mice, respectively. The present findings unravel a key role for the hypothalamus-pituitary-adrenal (HPA) system and brain extra-hypothalamic CRF/CRF1 receptor circuitry in somatic, molecular, and endocrine alterations induced by opiate withdrawal.     

Regulating peroxisome–ER contacts via the ACBD5-VAPB tether by FFAT motif phosphorylation and GSK3β

Peroxisomes and the endoplasmic reticulum (ER) cooperate in cellular lipid metabolism. They form membrane contacts through interaction of the peroxisomal membrane protein ACBD5 (acyl-coenzyme A–binding domain protein 5) and the ER-resident protein VAPB (vesicle-associated membrane protein–associated protein B). ACBD5 binds to the major sperm protein domain of VAPB via its FFAT-like (two phenylalanines [FF] in an acidic tract) motif. However, molecular mechanisms, which regulate formation of these membrane contact sites, are unknown. Here, we reveal that peroxisome–ER associations via the ACBD5-VAPB tether are regulated by phosphorylation. We show that ACBD5-VAPB binding is phosphatase-sensitive and identify phosphorylation sites in the flanking regions and core of the FFAT-like motif, which alter interaction with VAPB—and thus peroxisome–ER contact sites—differently. Moreover, we demonstrate that GSK3β (glycogen synthase kinase-3 β) regulates this interaction. Our findings reveal for the first time a molecular mechanism for the regulation of peroxisome–ER contacts in mammalian cells and expand the current model of FFAT motifs and VAP interaction.