A method for identification of inhibitors of the phosphorylation reactions of bacterial response regulator proteins using (31)P nuclear magnetic resonance spectroscopy

Bacterial response regulators are attractive targets for antibacterial drug development, yet random screening against these targets has failed as yet to identify chemicals that constitute viable leads. Alternative methods to provide leads for drug development based on identification and optimization of low affinity ligands from NMR screens have been described. However, leads from these processes still require verification in a bioassay, which is often problematic if compounds have unfavorable optical and solubility properties. A simple method, based on using NMR to observe the activity of the target, is described. It has the advantages of being able to characterize both low affinity leads and a wider selection of compounds in a structure activity relationships series, without the problems affecting a fluorescence assay. In this example we use (31)P to monitor the turnover of a bacterial response regulator, but the generic approach could be applied to other nuclei and thus a range of biological systems.

P2X receptor immunoreactivity in different arteries from the femoral, pulmonary, cerebral, coronary and renal circulations

The expression of the seven P2X receptor subunits (P2X1-7) in the rat vascular system was determined using subtype-selective antibodies. Arteries of different sizes (from arterioles to conduit vessels) from a range of vascular beds were used to give an overview of receptor expression. P2X1 receptor immunoreactivity was detected in the smooth muscle layer of arteries. The relative level of P2X1 receptor immunoreactivity was dependent on the size of the artery and the vascular bed; expression was highest in small and medium arteries. P2X4 receptors were detected in all arteries; once again, the relative level of expression was dependent on the size of the artery and the vascular bed. P2X5 receptor immunoreactivity was barely detectable in most arteries studied. P2X7 receptor immunoreactivity was generally punctate and associated with the outer adventitial layer. Immunoreactivity for P2X2, P2X3 and P2X6 receptors was not detected in arteries. These results demonstrate that arteries express multiple P2X receptor subunits and that there is a heterogeneity in the level of expression. The properties of artery P2X receptors correspond to homomeric P2X1 receptors, and the function of P2X4 and P2X5 receptor subunits in arteries is unclear.

Lack of run-down of smooth muscle P2X receptor currents recorded with the amphotericin permeabilized patch technique, physiological and pharmacological characterization of the properties of mesenteric artery P2X receptor ion channels

Immunoreactivity for P2X(1), P2X(4) and P2X(5) receptor subtypes was detected in the smooth muscle cell layer of second and third order rat mesenteric arteries immunoreactivity, for P2X(2), P2X(3), P2X(6) and P2X(7) receptors was below the level of detection in the smooth muscle layer. P2X receptor-mediated currents were recorded in patch clamp studies on acutely dissociated mesenteric artery smooth muscle cells. Purinergic agonists evoked transient inward currents that decayed rapidly in the continued presence of agonist (tau approximately 200 ms). Standard whole cell responses to repeated applications of agonist at 5 min intervals ran down. Run-down was unaffected by changes in extracellular calcium concentration, intracellular calcium buffering or the inclusion of ATP and GTP in the pipette solution. Run-down was overcome and reproducible responses to purinergic agonists were recorded using the amphotericin permeabilized patch recording configuration. The rank order of potency at the P2X receptor was ATP=2 methylthio ATP>alpha, beta-methylene ATP>CTP=l-beta,gamma-methylene ATP. Only ATP and 2meSATP were full agonists. The P2 receptor antagonists suramin and PPADS inhibited P2X receptor-mediated currents with IC(50)s of 4 microM and 70 nM respectively. These results provide further characterization of artery P2X receptors and demonstrate that the properties are dominated by a P2X(1)-like receptor phenotype. No evidence could be found for a phenotype corresponding to homomeric P2X(4) or P2X(5) receptors or to heteromeric P2X(1/5) receptors and the functional role of these receptors in arteries remains unclear.

P2 purinoceptor-mediated control of rat cerebral (pial) microvasculature; contribution of P2X and P2Y receptors

Purine and pyrimidine nucleotides evoke changes in the vascular tone of medium to large cerebral vessels through the activation of P2 purinoceptors. We have applied P2 receptor drugs to rat pial arterioles and measured changes in arteriole diameter (o.d. 40-84 micrometer at rest), and recorded currents from arteriolar smooth muscle cells using patch-clamp techniques. Transient vasoconstrictions and rapidly inactivating currents were evoked by alpha,beta-methylene ATP (0.1-30 micrometer) and were sensitive to the P2 receptor antagonists suramin and iso-PPADS. UTP and UDP (0.1-1000 micrometer) evoked sustained suramin-sensitive vasoconstrictions. ATP (0.1-1000 micrometer) and 2-methylthioATP (2MeSATP, 300 micrometer) evoked transient vasoconstrictions followed by sustained vasodilatations. ADP application resulted in only vasodilatation (EC50 approximately 4 micrometer). Vasodilator responses to ATP, 2MeSATP or ADP were unaffected by suramin (100 micrometer). RT-PCR analysis indicated that P2X1-7 and P2Y1,2,6 RNA can be amplified from the pial sheet. Our results provide direct evidence for the presence of functional P2X receptors with a phenotype resembling the P2X1 receptor subtype on cerebral resistance arterioles. The pharmacological properties of the pyrimidine-evoked responses suggest that a combination of P2Y2- and P2Y6-like receptors are responsible for the sustained vasoconstrictions. It is therefore likely that the nucleotides and their associated receptors are involved in a complicated regulatory system to control cerebral blood pressure.

Comparison of P2X receptors in rat mesenteric, basilar and septal (coronary) arteries

alpha beta meATP-evoked concentration-dependent, PPADS-sensitive, desensitising, P2X receptor-mediated, constrictions of mesenteric, basilar and septal artery rings with EC(50) values of 1, 1 and 30 microM, respectively. In patch clamp studies on acutely dissociated artery smooth cells alpha beta meATP-evoked transient inward currents (tau approximately 100 ms) with mean current densities of approximately 340, 175 and 120 pA/pF, respectively. P2X(1) receptor immunoreactivity was expressed in mesenteric and basilar arteries and this receptor subunit appears to dominate the P2X receptor phenotype in these vessels. In contrast P2X(1) receptor immunoreactivity was not detected in septal arteries and the alpha beta meATP sensitivity of constriction was not consistent with the involvement of P2X(1) receptors. These results suggest that not all arteries share a common P2X receptor phenotype.

External exposure to radionuclides accumulated in shoreline sediments with an application to the lower Clinch River

A simple analytical method was developed to estimate external doses from exposure to contaminated riverine shorelines. The method consists of deriving an adjustment factor that accounts for the geometry of the riverine shoreline; the adjustment factor is applied to the dose-rate coefficients already available for infinite contaminated surfaces. Such a geometry factor circumvents very complex radiation transport calculations which would otherwise be necessary to model exposures to a finite contaminated surface. For instance, for radionuclides emitting gamma rays of energies above 600 keV (e.g., 137Cs), the published dose-rate coefficients must be reduced by 75%, 60%, 50%, and 33% for shoreline widths of 4, 10, 20, and 50 m, respectively. The geometry factor changes only mildly with the energy of the gamma radiation. This property allows for the geometry factor to be used for radionuclides emitting multiple gamma rays of various energies. If a quick analysis is desired, the geometry factors derived for 137Cs can be used for all radionuclides. More refined analysis can be performed by deriving geometry factors for each radionuclide according to its gamma spectrum. Also, the mild variation with energy allows the geometry factors to be applied to the case when radionuclides are accumulated in layers under the soil surface, and not only to the case when radionuclides are deposited onto the soil surface. Empirical relationships between the geometry factor and the dimension of the shoreline were provided so that one can obtain values of the geometry factor for any shoreline width. These relationships can be easily used to account for the uncertainty in the dimension of the shoreline. The method was applied to derive similar adjustment factors for contaminated surfaces of other simple geometries (e.g., circular surfaces). An example of how this method can be applied to its full extent is presented for the case of external exposure to the shores of the lower Clinch River. This river received large amounts of 137Cs, 60Co, 106Ru, 95Zr, 95Nb, 144Ce, and 90Sr released during 1944-1991 from the Oak Ridge Reservation in Oak Ridge, Tennessee.

Reduced vas deferens contraction and male infertility in mice lacking P2X1 receptors

P2X1 receptors for ATP are ligand-gated cation channels, present on many excitable cells including vas deferens smooth muscle cells. A substantial component of the contractile response of the vas deferens to sympathetic nerve stimulation, which propels sperm into the ejaculate, is mediated through P2X receptors. Here we show that male fertility is reduced by approximately 90% in mice with a targeted deletion of the P2X1 receptor gene. Male mice copulate normally--reduced fertility results from a reduction of sperm in the ejaculate and not from sperm dysfunction. Female mice and heterozygote mice are unaffected. In P2X1-receptor-deficient mice, contraction of the vas deferens to sympathetic nerve stimulation is reduced by up to 60% and responses to P2X receptor agonists are abolished. These results show that P2X1 receptors are essential for normal male reproductive function and suggest that the development of selective P2X1 receptor antagonists may provide an effective non-hormonal male contraceptive pill. Also, agents that potentiate the actions of ATP at P2X1 receptors may be useful in the treatment of male infertility.

Effects of diadenosine polyphosphates (Ap(n)As) and adenosine polyphospho guanosines (Ap(n)Gs) on rat mesenteric artery P2X receptor ion channels

Diadenosine polyphosphates (Ap(n)As, n=3 - 7) and adenosine polyphospho guanosines (Ap(n)Gs, n=3 - 6) are naturally occurring vasoconstrictor substances found in platelets. These vasoconstrictor actions are thought to be mediated through the activation of P2X receptors for ATP. The effects of Ap(n)As and Ap(n)Gs at P2X receptors on rat mesenteric arteries were determined in contraction studies and using the patch clamp technique on acutely dissociated artery smooth muscle cells. P2X(1) receptor immunoreactivity was detected in the smooth muscle layer of artery rings. The sensitivity to alpha,beta-methylene ATP and desensitizing nature of rat mesenteric artery P2X receptors correspond closely to those of recombinant P2X(1) receptors. Ap(4)A, Ap(5)A and Ap(6)A evoked concentration dependent P2X receptor inward currents which desensitized during the application of higher concentrations of agonist. The agonist order of potency was Ap(5)A> or = Ap(6)A> or = Ap(4)A >> Ap(3)A. Ap(2)A and Ap(7)A were ineffective. Similar results were obtained in contraction studies except for Ap(7)A which evoked a substantial contraction. Ap(n)Gs (n=2 - 6)(30 microM) evoked P2X receptor inward currents in mesenteric artery smooth muscle cells. Ap(n)Gs (n=4 - 6) were less effective than the corresponding Ap(n)A. This study shows that at physiologically relevant concentrations Ap(n)As and Ap(n)Gs can mediate contraction of rat mesenteric arteries through the activation of P2X(1)-like receptors. However the activity of the longer chain polyphosphates (n=6 - 7) may be overestimated in whole tissue studies due to metabolic breakdown to yield the P2X receptor agonists ATP and adenosine tetraphosphate. British Journal of Pharmacology (2000) 129, 124 - 130

Inhibition of vasoconstriction and Ca2+ currents mediated by neuropeptide Y Y2 receptors

The effects of neuropeptide Y (NPY) and agonists selective for NPY Y1 and Y2 receptors were studied on contraction and Ca2+ currents in arterial smooth muscle. In isolated arterioles from the guinea pig small intestine, small brief constrictions were evoked by depolarising the arteriolar smooth muscle using high K+ solution applied from a micropipette. The constrictions were reduced in amplitude by the Y2-selective agonists PYY(13-36) and N-acetyl[Leu28, Leu31]NPY-(24-36) in concentrations from 20-100 nM. NPY or the Y1 selective agonist [Leu31 Pro34]NPY in concentrations from 50 pM to 100 nM increased the amplitude of the constrictions, with a maximum effect at 10 nM. Smooth muscle cells were isolated from rat small mesenteric arteries, and voltage-activated Ca2+ currents measured by whole cell patch clamping. The peak amplitude of the Ca2+ currents was decreased by N-acetyl[Leu28, Leu31]NPY-(24-36), and by NPY (100 nM). [Leu31, Pro34]NPY either had no effect or slightly increased the Ca2+ currents. We conclude that Y2 receptors on vascular smooth muscle can reduce Ca2+ currents induced by depolarisation, and thus oppose constriction caused by smooth muscle depolarisation.

Estimated folate intakes: data updated to reflect food fortification, increased bioavailability, and dietary supplement use

BACKGROUND

There is a critical need to estimate dietary folate intakes for nutrition monitoring and food safety evaluations, but available intake data are seriously limited by several factors.

OBJECTIVE

Our objective was to update 2 national food consumption surveys to reflect folate intakes as a result of the recently initiated food fortification program and to correct folate intakes for the apparently higher bioavailability of synthetic folic acid (SFA; ie, folate added to foods or from dietary supplements) than of naturally occurring folate so as to express intakes as dietary folate equivalents.

DESIGN

It was not possible to chemically analyze foods, so adjustments were made to food-composition data by using information about food ingredients and characteristics. Total folate intakes were estimated for several sex and age groups by using the modified data coupled with dietary supplement use.

RESULTS

Within the limitations of the data, our findings suggested that 67-95% of the population met or surpassed the new estimated average requirement, depending on the sex and age group and survey. Nonetheless, some subgroups had estimated intakes below these standards. Estimated SFA intakes suggested that approximately 15-25% of children aged 1-8 y, depending on the survey, had intakes above the newly established tolerable upper intake level. We estimated that 68-87% of females of childbearing age had SFA intakes below the recommended intake of 400 microgram/d, depending on the age group and survey.

CONCLUSION

There is a need to explore ways to improve folate intakes in targeted subgroups, including females of childbearing age, while not putting other population groups at risk of excessive intakes.

Health claims and observational human data: relation between dietary fat and cancer

The US Food and Drug Administration review that provided the basis for authorizing a food-label health claim linking the risk of cancer to dietary fat intake illustrated several considerations in the use of epidemiologic data, and observational data in particular, to support dietary recommendations. The review suggested the need for clear and established criteria for judging the quality of observational human data as well as the importance of making the evaluation process for individual studies transparent and organized. The review, which provided for a claim in the absence of controlled human studies, also suggested that observational data may play a greater role when the nature of the relation to be described by a health-claim statement is broad and general rather than targeted and specific. Of particular importance was the relevance of available data to the questions inherent in showing a diet-disease relation, the need to consider the totality of the evidence, and the key role that existing authoritative reports must play in establishing the basis for relation.

Restriction endonuclease profiles of orf virus isolates from the British Isles

A comparison of DNA profiles of representative isolates of orf virus, obtained using four different restriction endonucleases (RE), showed that the enzyme EcoRI could be used to discriminate between wild-type virus isolates and vaccine strains. The enzyme was used to compare the RE profiles of orf virus isolates from 43 outbreaks of orf that occurred in vaccinated flocks between 1988 and 1993; 21 outbreaks yielded wild-type virus, 10 yielded vaccine viruses, three produced both vaccine and wild-type viruses and no clear result was obtained from nine of the outbreaks. From the 21 outbreaks yielding wild-type viruses, 28 orf virus isolates had clear RE profiles and 15 distinct RE profiles were recorded. Usually only one virus type was associated with each outbreak but from two farms, two different wild-type viruses were recovered. No predominant genotype was identified, with four RE profile types being recovered for more than one outbreak. From the more severe form of orf involving the buccal cavities of lambs only wild-type viruses were recovered, with at least four different genotypes being represented.

2',3'-O-(2,4,6- trinitrophenyl) adenosine 5'-triphosphate (TNP-ATP)--a nanomolar affinity antagonist at rat mesenteric artery P2X receptor ion channels

1. P2X receptor activation by alpha,beta-meATP evoked inward currents in acutely dissociated rat mesenteric artery smooth muscle cells and contractions of whole artery rings. 2. The selective P2X1 and P2X3 receptor antagonist TNP-ATP inhibited P2X receptor mediated inward currents in response to 3 microM alpha,beta-meATP (an approximately EC90 concentration) with an IC50 of approximately 2 nM. This provides further evidence that the P2X receptor underlying membrane depolarisation associated with P2X receptor activation can be accounted for by the expression of P2X1 receptors. 3. TNP-ATP inhibited alpha,beta-meATP induced contractions with an IC50 of approximately 30 microM and had non-specific effects on smooth muscle contraction. 4. The reduced potency of TNP-ATP in whole tissue experiments probably reflects the breakdown of TNP-ATP by nucleotidases. Thus, TNP-ATP is of limited use in whole tissue experiments as a P2X receptor antagonist.

Sudden death in sheep associated with Clostridium sordellii

Clostridium sordellii was isolated from 37 sheep, in 29 flocks, which died suddenly between 1993 and 1995. The sheep were of all ages, but the most severe gross lesions affected lambs four to 10 weeks of age. In older weaned lambs and ewes the gross changes were less marked and more variable. Thirty sheep suffering from a variety of other conditions were examined and C sordellii was not isolated. The isolation of C sordellii has been reported only twice before from sheep in Britain, and on both occasions no detailed investigations were described. The evidence from this study indicates that C sordellii should be considered when investigating the cause of sudden death in sheep of all ages in Britain.

Reduction of vasoconstriction mediated by neuropeptide Y Y2 receptors in arterioles of the guinea-pig small intestine

Brief applications of a high-K+ solution were used to evoke transient constrictions of arterioles from the guinea-pig small intestine. Analogues of neuropeptide Y (NPY) selective for Y2-receptors reduced the constrictions, whereas NPY or a Y1-selective analogue potentiated the constrictions. We conclude that arteriolar smooth muscle has both Y1 and Y2 receptors, and suggest that Y2 receptors inhibit vasoconstriction by modulating the opening of voltage-sensitive Ca2+ channels. This may be related to the role of NPY that is present in some vasodilator nerves.