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M Claire

Publications and source records attributed to M Claire.

At least 19 recordsLinked to original sources
PubMed2006

Complement component C3 mediates inflammatory injury following focal cerebral ischemia.

The complement cascade has been implicated in ischemia/reperfusion injury, and recent studies have shown that complement inhibition is a promising treatment option for acute stroke. The development of clinically useful therapies has been hindered, however, by insufficient understanding of which complement subcomponents contribute to post-ischemic injury. To address this issue, we subjected mice deficient in selected complement proteins (C1q, C3, C5) to transient focal cerebral ischemia. Of the strains investigated, only C3-/- mice were protected, as demonstrated by 34% reductions in both infarct volume (P<0.01) and neurological deficit score (P<0.05). C3-deficient mice also manifested decreased granulocyte infiltration (P<0.02) and reduced oxidative stress (P<0.05). Finally, administration of a C3a-receptor antagonist resulted in commensurate neurological improvement and stroke volume reduction (P<0.05). Together, these results establish C3 activation as the key constituent in complement-related inflammatory tissue injury following stroke and suggest a C3a anaphylatoxin-mediated mechanism.

Animals↗
PubMed2006

The astrobiology primer: an outline of general knowledge--version 1, 2006.

The Astrobiology Primer has been created as a reference tool for those who are interested in the interdisciplinary field of astrobiology. The field incorporates many diverse research endeavors, but it is our hope that this slim volume will present the reader with all he or she needs to know to become involved and to understand, at least at a fundamental level, the state of the art. Each section includes a brief overview of a topic and a short list of readable and important literature for those interested in deeper knowledge. Because of the great diversity of material, each section was written by a different author with a different expertise. Contributors, authors, and editors are listed at the beginning, along with a list of those chapters and sections for which they were responsible. We are deeply indebted to the NASA Astrobiology Institute (NAI), in particular to Estelle Dodson, David Morrison, Ed Goolish, Krisstina Wilmoth, and Rose Grymes for their continued enthusiasm and support. The Primer came about in large part because of NAI support for graduate student research, collaboration, and inclusion as well as direct funding. We have entitled the Primer version 1 in hope that it will be only the first in a series, whose future volumes will be produced every 3-5 years. This way we can insure that the Primer keeps up with the current state of research. We hope that it will be a great resource for anyone trying to stay abreast of an ever-changing field.

Astronomical Phenomena↗
PubMed1999

Homologous and heterologous induction of the human bradykinin B1-receptor and B1-receptor localisation along the rat nephron.

The kinin B1-receptor which is absent or expressed at very low levels under physiological conditions is strongly induced under inflammatory conditions. It has been shown that B1-receptor induction during inflammation involves interleukin-1beta (IL-1beta) production and activation of nuclear factor-kappaB (NF-kappaB). Since bradykinin (BK), the B2-receptor agonist induces IL-1beta expression and activates NF-kappaB, we have analysed the effect of B2-receptor activation in cultured human lung fibroblasts cells on B1-receptor expression by a semiquantitative RT-PCR analysis. Treatment with BK resulted in a significant increase in the expression of B1-receptor mRNA which was abolished by a specific B2-receptor antagonist. This result suggests that B2-receptor activation can prime the expression of B1-receptors. Although the renal localisation of the B2-receptor has been thoroughly studied, nothing is known about the distribution of the B1-receptor in the kidney. Using a combination of microdissection and a semiquantitative RT-PCR/Southern blot analysis we showed the absence of B1-receptors under physiological conditions in 10 microdissected rat nephron segments. However, 18 h LPS-treatment induced significant expression of the B1-receptor in all, but one segment. These studies provide the first molecular basis for the observed changes in renal haemodynamics after B1-agonist infusion in animal kidney models.

Animals↗
PubMed1999

Ontogeny of follicle-stimulating hormone and luteinizing hormone gene expression during pubertal development in the female striped bass, Morone saxatilis (Teleostei).

Pubertal development in teleost fish is characterized by gonadal growth that is directly stimulated by the pituitary gonadotropins, FSH and LH. We used a quantitative ribonuclease protection assay to provide, for the first time, the developmental profiles of the alpha-, betaFSH-, and betaLH-subunit gene expression in a seasonal breeding fish, the female striped bass (3-yr study, n = 207). Two-year-old females were sexually immature, although a transient rise in all gonadotropin subunit mRNAs was measured in the pituitary. Pubertal ovarian development occurred in 65% of 3-yr-old females, characterized by the appearance of lipid droplets within the oocytes. This reproductive phase, termed pubertal development, was associated with a 34-fold increase in the mRNA levels of betaFSH and a rise in the pituitary concentration of LH. The first sexual maturation took place in 4-yr-old females and coincided with a 218-fold increase in the mRNA levels of betaFSH. During this time period, the mRNA levels of the alpha and betaLH subunits increased by 11- and 8-fold, respectively. At the final stages of vitellogenic growth, mRNA levels of betaFSH declined to basal levels, whereas the mRNA levels of the alpha and betaLH subunits remained elevated. Throughout the study, pituitary LH concentration was positively correlated to the mRNA levels of betaLH, but plasma levels of LH remained low and unchanged (0.4-0.8 ng/ml) despite increasing levels of pituitary LH concentration, suggesting a regulated secretion pathway. Taken together, the data show that the profiles of betaFSH and betaLH mRNAs appear to follow an annual rhythm that is associated with developmental events in the growing oocytes. In particular, increasing levels of betaFSH mRNA appear to underlie the first sexual maturity in the female striped bass.

Animals↗
PubMed1998

Fatty acid composition of phospholipids and neutral lipids from human diabetic small arteries and veins by a new TLC method.

It has been suggested that lipid peroxidation of polyunsaturated fatty acids (PUFA) may play a role in the pathogenesis of diabetic complications. To test this hypothesis, we aimed to compare PUFA composition of small arteries and veins (< 500 microm diameter) obtained from diabetic or non-diabetic Guadeloupean patients undergoing arterio-venous shunt surgery before renal dialysis. Small forearm subcutaneous vessels were analysed by a new TLC method which involved inclusion of vascular biopies directly in alveoles made in the TLC gel and lyophilization onto the plate. The TLC plate was then chromatographed and lipids were both extracted and eluted during this step. Fatty acid composition of phospholipid and neutral lipid fractions were determined. Similar fatty acid composition was obtained for arteries and veins from diabetic or non-diabetic subjects. In phospholipids from diabetic vessels, major changes consisted of a 20% decrease of arachidonic acid (20:4 n-6), a 40% decrease of its elongation product 22:4 n-6 and 30% increase of 18:2 n-6. In neutral lipids, 20:4 n-6 was also diminished by 60% whereas oleic acid increased by 15%. This loss of arachidonic acid in small diabetic vessels suggests impaired delta6-desaturase forming 20:4 n-6 or alternatively increased peroxide formation, in the vascular wall of small vessels in diabetic patients.

Adipose Tissue↗
PubMed1994

Regulation of gamma-glutamyl transpeptidase and alkaline phosphatase activities in immortalized rat brain microvessel endothelial cells.

Rat brain microvessel endothelial cells were immortalized by transfection with a plasmid containing the E1A adenovirus gene. One clone, called RBE4, was further characterized. These cells display a nontransformed phenotype and express typical endothelial markers, Factor VIII-related antigen and Bandeiraea simplicifolia binding sites. When RBE4 cells were grown in the presence of bFGF and on collagen-coated dishes, confluent cultures developed sprouts that extend above the monolayer and organized into three-dimensional structures. The activity of the blood-brain barrier-associated enzyme, gamma-glutamyl transpeptidase (gamma GTP), was expressed in these structures, not in the surrounding monolayer. Similar results were obtained with the microvessel-related enzyme alkaline phosphatase (ALP). Addition of agents that elevate intracellular cAMP reduced the formation of three-dimensional structures, but every cell inside the aggregates still expressed gamma GTP and ALP activities. Such structures, associated with high levels of gamma GTP and ALP activities, were also induced by astroglial factors, including (1) plasma membranes from newborn rat primary astrocytes or rat glioma C6 cells, (2) C6 conditioned media, or (3) diffusible factors produced by primary astrocytes grown in the presence of, but not in contact with RBE4 cells. RBE4 cells thus remain sensitive to angiogenic and astroglial factors for the expression of the blood-brain barrier-related gamma GTP activity, as well as for ALP activity, and could constitute the basis of a valuable in vitro model of the blood-brain barrier.

Alkaline Phosphatase↗
PubMed1993

Synthesis of new 11 beta-substituted spirolactone derivatives. Relationship with affinity for mineralocorticoid and glucocorticoid receptors.

Various steroidal 17-spirolactones substituted in the 11 beta-position were synthesized to study the relationship between the nature of the 11 beta-arm and their affinity for cytosolic mineralocorticoid (MR) and glucocorticoid (GR) receptors prepared from adrenalectomized rabbit kidney or liver. One of them, the 11 beta-allenyl-3-oxo-19-nor-17-pregna-4,9-diene-21,17- carbolactone derivative, exhibited the same affinity for MR as aldosterone and a 5-fold higher affinity than mespirenone. Its affinity for GR was found to be relatively low. As suggested by molecular modeling, the marked differences in mineralocorticoid receptor binding affinity could be related to the structural features induced by this 11 beta-allenic substituent.

Adrenalectomy↗
PubMed1993

Nitric oxide and endothelin secretion by brain microvessel endothelial cells: regulation by cyclic nucleotides.

Endothelin (ET)-1 was originally characterized as a potent vasoconstrictor peptide secreted by vascular endothelial cells. It possesses a wide range of biological activities within the cardiovascular system and in other organs, including the brain. Also secreted by endothelial cells, nitric oxide (NO), has recently been identified as a relaxing factor, as well as a pleiotropic mediator, second messenger, immune defence molecule, and neurotransmitter. Most of the data concerning the secretion of these two agents in vitro has been collected from studies on macrovascular endothelial cells. Given the remarkable heterogeneity of endothelia in terms of morphology and function, we have analyzed the ability of brain microvessel endothelial cells in vitro to release ET-1 and NO, which, at the level of the blood-brain barrier, have perivascular astrocytes as potential targets. The present study was performed with immortalized rat brain microvessel endothelial cells, which display in culture a non transformed phenotype. Our data demonstrate that: (1) these cells release NO when induced by IFN gamma and TNF alpha, (2) they constitutively secrete ET-1, and (3) cAMP potentiates the cytokine-induced NO release and exerts a biphasic regulation on ET-1 secretion: micromolar concentrations of 8-Br-cAMP inhibit and higher doses stimulate ET-1 secretion. This stimulation is blocked by EGTA and the calmodulin antagonist W7, but not by protein kinase C inhibitors, suggesting the involvement of the calmodulin branch of the calcium messenger system. These results suggest that cerebral microvessel endothelial cells may participate in vivo to the regulation of glial activity in the brain through the release of NO and ET-1.

Amino Acid Oxidoreductases↗
PubMed1992

Corticosteroid receptors in cells derived from rat brain microvessels: mRNA identification and aldosterone binding.

B7 is a cell clone derived from rat brain microvessels. Expression of an amiloride-sensitive cationic channel has been recently established in these cells. In this study, the polymerase chain reaction (PCR) was used to amplify definite segments of mineralocorticoid and glucocorticoid receptor mRNA in B7 cells. Aldosterone binding was also characterized. Two classes of sites were detected. Aldosterone exhibited a high affinity for type I sites [dissociation constant (Kd) approximately 0.3 nM] and a lower one for type II sites (Kd approximately 20 nM). RU 28362, a highly specific glucocorticoid agonist, did not compete for type I sites. RU 28362 and dexamethasone were better competitors for type II sites than aldosterone. The sedimentation coefficients of aldosterone type I and type II complexes were approximately 9S. These characteristics are close to the one exhibited by aldosterone type I and type II receptors in rat kidney and other target tissues. In intact B7 cells, aldosterone binding expressed as number of acceptor sites per cell was higher (approximately 41,000 for type II and 8,800 for type I) than in the soluble cellular extract (approximately 18,000 for type II and 1,000 for type I).

Aldosterone↗
PubMed1991

Synthesis of new 10 beta-propargylic and 11 beta-allenic steroidal spirolactones.

As part of continuing studies on the synthesis of new, biologically interesting 11 beta-substituted steroidal spirolactones, we describe here the competition between 10 beta-propargylation and 11 beta-allenylation. Grignard addition of allenyl magnesium bromide to an appropriate 5,10-epoxy-9(11)-olefin provides 10 beta-propargylation or 11 beta-allenylation. The role of the catalytic effect of copper chloride and of the solvent is evaluated. Confirmation of the structural assignments of these new 3,3-ethylenethioxy-10 beta-propargyl (or 11 beta-allenyl)-19-nor-17 alpha-pregna-4,9-diene-21,17-carbolactones is reported.

Molecular Structure↗
PubMed1989

Aldosterone receptors in A6 cells: physicochemical characterization and autoradiographic study.

The A6 cell line is derived from the kidney of Xenopus laevis. Aldosterone increases sodium transport across A6 cell epithelia. In the present study, aldosterone binding characteristics were studied in A6 cell cytosol. Both type I (mineralocorticoid) and type II (glucocorticoid) receptors are present in the cytosolic fraction of these cells. Aldosterone and corticosterone had a high affinity for type I sites (Kd = 1.25 and 0.16 nM, respectively) and a lower affinity for type II sites (Kd = 39 and 10 nM, respectively). Testosterone and estradiol did not compete for aldosterone binding. RU 26988, a highly specific glucocorticoid agonist, competed with aldosterone for type II but not for type I sites. Hydrodynamic parameters of both type I and type II corticosterone receptor complexes were identical. Their Stokes radius was approximately 6 nm, as estimated by high-performance size-exclusion chromatography, and their sedimentation coefficient determined by ultracentrifugation on glycerol gradients was approximately 9s. The molecular mass calculated from these parameters was approximately 200 kDa, a value that is very close to the value estimated for nontransformed mineralocorticoid and glucocorticoid receptors of other species. The [3H]aldosterone labeling of intact A6 cells was examined by autohistoradiography. At every concentration tested (2, 20, and 50 nM), all cells were found to be specifically labeled in both cytoplasm and nucleus. At 20 nM, in the presence of an excess of RU 26988, labeling was also detected. At every concentration the labeling data was compatible with a Gaussian distribution, indicating that A6 cells correspond to a homogeneous population with regard to aldosterone binding and that probably both type I and type II sites are present in the same cells.

Aldosterone↗
PubMed1989

Aldosterone binding sites along nephron of Xenopus and rabbit.

Distal segment of several amphibians exhibits aldosterone-modulated ion transport properties. On the other hand, A6 cells, derived from Xenopus laevis (XL) kidney, are aldosterone sensitive. We examined the distribution of aldosterone binding sites in isolated tubules of XL compared with rabbit. After incubation with 2 nM [3H]aldosterone, microdissected tubular segments from proximal (PT), distal straight segment (DST), and flask cell collecting (CT) tubules from XL and from rabbit cortical thick ascending limb (CTAL), connecting (CNT), and collecting (CCD) tubules were processed for dry film autoradiography. In XL, specific nuclear labeling of type I (mineralocorticoid) sites was restricted to DST. Labeling of type II (glucocorticoid) sites was present all along the tubule. No specific cytoplasmic labeling was observed, except for type II sites in PT. In the rabbit, aldosterone binds to both type I and type II sites in the three tubular segments studied. In these segments, the binding was about fourfold higher than in DST of XL. These results bring direct evidence in designating the distal tubule of amphibians as a target epithelium for aldosterone. In addition, they suggest that A6 cell line may derive from DST of the Xenopus nephron.

Androstanols↗
PubMed1987

A new affinity matrix for mineralocorticoid receptors.

The behavior of mineralocorticoid and glucocorticoid receptors of rabbit kidney cytosol was investigated on two affinity gels: a new affinity matrix prepared with a 3-O-derivative of carboxymethyloxime deoxycorticosterone (deoxycorticosterone gel) and a gel linked to a 17 beta-dexamethasone derivative (dexamethasone gel). Deoxycorticosterone gel was highly specific, since it retained mineralocorticoid but not glucocorticoid receptors, and dexamethasone gel exhibited high selectivity for glucocorticoid receptors since it did not bind mineralocorticoid receptors. The use of these two matrices allowed separation of mineralocorticoid and glucocorticoid receptors and further characterization of each type of cytosolic receptors after its isolation. Cytosolic mineralocorticoid and glucocorticoid receptors stabilized by tungstate were found to have a Stokes radius of approximately 6 nm, as determined by high performance size exclusion chromatography and a sedimentation coefficient of approximately 9 S, determined on a glycerol density gradient containing tungstate, under either high or low salt conditions. The hydrodynamic parameters, binding characteristics, and specificity of mineralocorticoid receptors were the same in the untreated and dexamethasone gel-treated cytosol. Similarly glucocorticoid receptor characteristics remained unchanged after deoxycorticosterone gel treatment, indicating biochemical independence of cytosolic mineralocorticoid and glucocorticoid receptors. The [3H]aldosterone receptor complex eluted from deoxycorticosterone gel was recovered with a 30-40% yield and a purification factor of about 1000. Purified mineralocorticoid receptors had the same sedimentation coefficient as cytosolic mineralocorticoid receptors (9 S) but a different Stokes radius (4 versus 6 nm). The decrease in the Stokes radius of the purified mineralocorticoid receptors was probably due to the gel filtration method. These results indicate that the newly synthesized matrix specific for mineralocorticoid receptors constitutes a powerful tool for their extensive purification.

Aldosterone↗
PubMed1986

Cross-reactivity of a monoclonal antiglucocorticoid receptor antibody BuGR1 with glucocorticoid and mineralocorticoid receptors of various species.

The reactivity of a monoclonal antibody BuGR1, raised against glucocorticoid receptors of rat liver, with glucocorticoid and mineralocorticoid receptors of mammalian (rabbit) and amphibian (A6 cells) origin was examined. The glucocorticoid receptors of rabbit kidney and liver and of A6 cells were labeled with tritiated dexamethasone. The mineralocorticoid receptors were labeled with tritiated aldosterone in the presence or absence of RU26988, depending on whether aldosterone was bound to glucocorticoid receptors (A6 cells) or not (rabbit kidney), in addition to its binding to mineralocorticoid receptors. BuGR1 did not recognize mineralocorticoid receptors of A6 cells and rabbit kidney. BuGR1 cross-reacted with glucocorticoid receptors of rabbit liver and kidney but not of A6 cells, suggesting that the domain of glucocorticoid receptors recognized by BuRG1 could be present only in the mammalian species. The findings indicate that BuGR1 shows species differences as well as receptor class specificity.

Aldosterone↗
PubMed1986

Affinity of corticosteroids for mineralocorticoid and glucocorticoid receptors of the rabbit kidney: effect of steroid substitution.

Corticosteroid derivatives coupled in the C3, C7 or C17 position with a long aliphatic chain were synthesized in order to select a suitable ligand for the preparation of a biospecific affinity adsorbent for mineralocorticoid receptor purification. The affinity of these derivatives for mineralocorticoid receptors (MR) and glucocorticoid receptors (GR) was explored in rabbit kidney cytosol. In this model, aldosterone bound to a single class of receptors with high affinity (Kd 1 nM) and mineralocorticoid specificity. RU26988, a highly specific ligand for GR, did not compete for these sites. The C7 and C17 positions were found to be of crucial importance in the steroid's interaction with the mineralocorticoid receptors, since the linkage of a long side chain in these positions induced complete loss of affinity. Hence, deoxycorticosterone no longer bound to MR after 17 beta substitution with a 9-carbon aliphatic chain. This loss of affinity was not observed for glucocorticoids. The 17 beta nonylamide derivative of dexamethasone still competed for GR. Increasing the length of the C7 side of the spirolactone SC26304 suppressed its affinity for MR. Finally, C3 was an appropriate position for steroid substitution. The 3-nonylamide of carboxymethyloxime deoxycorticosterone bound to MR but not to GR, and therefore constitutes a suitable ligand for the preparation of a mineralocorticoid adsorbent.

Adrenal Cortex Hormones↗
PubMed1985

Receptor occupancy vs. induction of Na+-K+-ATPase and Na+ transport by aldosterone.

In the urinary bladder of the toad Bufo marinus aldosterone (between 0.8 and 100 nM) stimulates Na+ transport [half-maximal induction concentration (K1/2) = 6.5 nM]. At low hormone concentrations (0.8-8 nM), the increase of Na+ transport between 0.75 and 2.5 h is accompanied by a fall in transepithelial resistance (R). Higher hormone concentrations (30-800 nM) induce an additional resistance-independent fraction of Na+ transport within 2.5-8 h. From 6 h on, aldosterone (between 0.2 and 20 nM) stimulates in the same tissue the biosynthesis rate of the alpha- and beta-subunits of Na+-K+-ATPase (K1/2 = 3 and 1.5 nM, respectively). New pump synthesis is thus not a prerequisite for the early mineralocorticoid response but might be linked to the late transport event. The mineralocorticoid response is usually ascribed to interaction with the higher affinity type 1 receptor. In the present study we show, however, that at least 55% of the overall Na+ transport response is linked to nuclear occupation of the lower affinity type 2 receptors [dissociation constant (Kd) = 50 nM, maximum number of binding sites (Nmax) = 315 fmol/mg protein]. Distinct aldosterone effects, such as the fall in R and the increase in Na+-K+-ATPase synthesis, are more closely related to occupation of type 1 receptors (Kd = 0.3 nM, Nmax = 23 fmol/mg protein). At maximal induction of these latter parameters, only about 20% of type 2 receptors are occupied. These results suggest that both types of aldosterone receptors are involved in the mediation of the full mineralocorticoid response: type 1 in the early and late and type 2 particularly in the late tissue response.

Aldosterone↗
PubMed1985

Cytoplasmic and nuclear uptake of aldosterone in toad bladder: a mathematical modeling approach.

The mechanism of aldosterone uptake in the epithelial cells of toad bladder was studied using mathematical modeling. Two complementary approaches were used. The first involved analysis of cytosolic aldosterone binding at steady state according to models defined by the sum of independent noninteractive binding sites. The best model describing the experimental data corresponded to two specific binding sites with mean dissociation constant values of 0.20 and 60 nM for types 1 and 2, respectively. The second approach was based on the analysis of cytoplasmic and nuclear aldosterone uptake kinetics at 25 and 0 degrees C in intact bladder. Two models (A and B) were studied. They both implied the existence of two types of aldosterone binding sites as precursors of the corresponding chromatin bound complexes. In model A, nuclear translocation of the two types of receptors was assumed to obey first-order kinetics. In model B, the translocation process for type 1 sites involved a time lag leading to delayed binding to chromatin. Both models were found to fit the experimental data satisfactorily. The fit obtained for model B appeared to be better at low aldosterone concentrations.

Aldosterone↗