USING RIGHTS OF FIRST REFUSAL FOR FARMLAND RETENTION

How can rights of first refusal protect prime agricultural land? This paper develops a theory for valuing rights of first refusal based on compensation for foreclosing future demand, information asymmetry, and advance purchase of market share. A procedure is developed for governments to use these rights to prevent conversion.Land Economics/Use,

ACTH and polymorphisms at steroidogenic loci as determinants of aldosterone secretion and blood pressure

The majority of genes contributing to the heritable component of blood pressure remain unidentified, but there is substantial evidence to suggest that common polymorphisms at loci involved in the biosynthesis of the corticosteroids aldosterone and cortisol are important. This view is supported by data from genome-wide association studies that consistently link the CYP17A1 locus to blood pressure. In this review article, we describe common polymorphisms at three steroidogenic loci (CYP11B2, CYP11B1 and CYP17A1) that alter gene transcription efficiency and levels of key steroids, including aldosterone. However, the mechanism by which this occurs remains unclear. While the renin angiotensin system is rightly regarded as the major driver of aldosterone secretion, there is increasing evidence that the contribution of corticotropin (ACTH) is also significant. In light of this, we propose that the differential response of variant CYP11B2, CYP11B1 and CYP17A1 genes to ACTH is an important determinant of blood pressure, tending to predispose individuals with an unfavourable genotype to hypertension

Sample preparation for nanoanalytical electron microscopy using the FIB lift-out method and low energy ion milling

Thinning specimens to electron transparency for electron microscopy analysis can be done by conventional (2 - 4 kV) argon ion milling or focused ion beam (FIB) lift-out techniques. Both these methods tend to leave ''mottling'' visible on thin specimen areas, and this is believed to be surface damage caused by ion implantation and amorphisation. A low energy (250 - 500 V) Argon ion polish has been shown to greatly improve specimen quality for crystalline silicon samples. Here we investigate the preparation of technologically important materials for nanoanalysis using conventional and lift-out methods followed by a low energy polish in a GentleMill™ low energy ion mill. We use a low energy, low angle (6 - 8°) ion beam to remove the surface damage from previous processing steps. We assess this method for the preparation of technologically important materials, such as steel, silicon and GaAs. For these materials the ability to create specimens from specific sites, and to be able to image and analyse these specimens with the full resolution and sensitivity of the STEM, allows a significant increase of the power and flexibility of nanoanalytical electron microscopy

Steroid Hydroxylases in the Rat Brain: Evidence of Gene Expression and Enzyme Activity

Aldosterone and corticosterone are the main mineralocorticoid and glucocorticoid products of the rat adrenal cortex. They share a common biosynthetic pathway until the fmal stage where the substrate deoxycorticosterone (DOC) is converted to either aldosterone or corticosterone by the actions of the enzymes aldosterone synthase (CYP11B2) or 11beta-hydroxylase (CYP11B1) respectively. These enzymes are the products of highly homologous genes whose expression, along with that of other components of the corticosteroidogenic pathway, was long thought to be confined to the adrenal cortex. In recent years, however, due to the advent of more sensitive molecular biological techniques, evidence has accumulated to suggest that this is not the case and that certain extra-adrenal tissues may be capable of autonomous aldosterone and corticosterone production. In chapter 3, RT-PCR was used to detect transcripts from the CYP11B1 and CYP11B2 genes in a number of different tissue types. The transcription of genes encoding other components of corticosteroidogenesis, such as the side-chain cleavage enzyme and adrenodoxin, was also examined. Of the tissues examined, only brain tissue was found to contain transcripts from all these genes. Chapter 4 describes attempts using an SDS-polyacrylamide gel electrophoresis and immunoblotting technique to show that these transcripts are translated within brain tissue to result in the enzymes themselves. This utilised two monoclonal antibodies raised against non-homologous regions of the rat aldosterone synthase and 11beta-hydroxylase enzymes. However, no evidence of translation in extra-adrenal tissue was obtained using this technique, despite the identification of a positive band corresponding to 11beta-hydroxylase in adrenal tissue fractions. In chapter 5, the same antibodies were used to detect aldosterone synthase and 11beta-hydroxylase within extra-adrenal tissues by immunostaining methods. Using adrenal tissue sections, the two antibodies were found to be highly specific for their respective antigens and apparently free of the cross-reactivity which might be expected between such highly homologous enzymes. Positive staining was also produced in brain tissue, where the enzymes were found to colocalise within the hippocampus and the cerebellum. Although previously published work had established that steroidogenesis occurs in the glial cells of the central nervous system, strong positive staining within the Purkinje cells of the cerebellum in this study presented strong evidence for neuronal expression. Rigorous control experiments confirmed the specificity of these results. Attempts to produce specific staining within heart tissue were unsuccessful. Primary cultures of rat fetal hippocampal neurons permitted the study of CYP11B1 and CYP11B2 expression within a homogenous neuronal cell type. This work is described in chapter 6. CYP11B1 and CYP11B2 transcription and translation within these neuronal cells was demonstrated by the techniques used previously. In addition, the substrate DOC was incubated with the cells for 24-hour periods. Upon extraction and partial purification, the aldosterone and corticosterone content of the cell medium was measured by radioimmunoassay and shown to be significantly higher than that of control medium incubated in the absence of DOC. In summary, this thesis provides compelling evidence of the production of aldosterone and corticosterone within the rat central nervous system. It also includes detailed information concerning the distribution of the aldosterone synthase and 11beta- hydroxylase enzymes that produce these steroids. Finally, it demonstrates that neuronal cells cultured from the fetal rat hippocampus are capable of converting DOC into their respective products. These findings could have profound implications for the diverse physiological processes that are regulated by corticosterone and aldosterone

Proteinase-activated receptor 2 is involved in the behavioural changes associated with sickness behaviour

Proteinase-activated receptor-2 (PAR2) is widely expressed in the CNS but whether it plays a key role in inflammation-related behavioural changes remains unknown. Hence, in the present study we have examined whether PAR2 contributes to behaviour associated with systemic inflammation using PAR2 transgenic mice. The onset of sickness behaviour was delayed and the recovery accelerated in PAR2-/- mice in the LPS-induced model of sickness behaviour. In contrast, PAR2 does not contribute to behaviour under normal conditions. In conclusion, these data suggest that PAR2 does not contribute to behaviour in the normal healthy brain but it plays a role in inflammation-related behavioural changes

MicroRNAs in Aldosterone Production and Action

The secretion of aldosterone by the adrenal cortex is a tightly regulated process. Loss of this control can result in severe hypertension and end-organ damage, so detailed understanding of the various mechanisms by which the body regulates aldosterone biosynthesis is key. The emergence of microRNAs (miRNAs) as negative regulators of numerous physiological processes has naturally led to their study in the context of aldosterone production. We summarise several studies that have demonstrated a significant role for microRNAs in aldosterone biosynthesis and action, thereby presenting a possible therapeutic role in the treatment of common forms of hypertension such as primary aldosteronism. Furthermore, the presence of microRNAs in the circulation offers the prospect of accessible and informative biomarkers that may simplify the currently protracted and technically difficult diagnosis of such conditions

Effects of ACTH, dexamethasone, and adrenalectomy on 11β-hydroxylase (CYP11B1) and aldosterone synthase (CYP11B2) gene expression in the rat central nervous system

Using a highly sensitive quantitative RT-PCR method for the measurement of CYP11B1 (11β-hydroxylase) and CYP11B2 (aldosterone synthase) mRNAs, we previously demonstrated that CYP11B2 expression in the central nervous system (CNS) is subject to regulation by dietary sodium. We have now quantified the expression of these genes in the CNS of male Wistar Kyoto (WKY) rats in response to systemic ACTH infusion, dexamethasone infusion, and to adrenalectomy. CYP11B1 and CYP11B2 mRNA levels were measured in total RNA isolated from the adrenal gland and discrete brain regions using real-time quantitative RT-PCR. ACTH infusion (40 ng/day for 7 days, N=8) significantly increased CYP11B1 mRNA in the adrenal gland, hypothalamus, and cerebral cortex compared with animals infused with vehicle only. ACTH infusion decreased adrenal CYP11B2 expression but increased expression in all of the CNS regions except the cortex. Dexamethasone (10 μg/day for 7 days, N=8) reduced adrenal CYP11B1 mRNA compared with control animals but had no significant effect on either gene's expression in the CNS. Adrenalectomy (N=6 per group) significantly increased CYP11B1 expression in the hippocampus and hypothalamus and raised CYP11B2 expression in the cerebellum relative to sham-operated animals. This study confirms the transcription of CYP11B1 and CYP11B2 throughout the CNS and demonstrates that gene transcription is subject to differential regulation by ACTH and circulating corticosteroid levels