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A F Muller

Publications and source records attributed to A F Muller.

At least 73 records · Page 4Linked to original sources
PubMed1988

"High-resolution" mini-two-dimensional gel electrophoresis automatically run and stained in less than 6 h with small, ready-to-use slab gels.

Although two-dimensional (2-D) gel electrophoresis is one of the most powerful techniques for analyzing protein mixtures, its application in routine clinical laboratories is currently limited, because it is time-consuming, complex, and relatively expensive. Here we describe a method for automatically running and staining "high-resolution" mini 2-D electrophoresis gels in less than 6 h, by using "ready-to-use" slab gels and a PhastSystem electrophoresis apparatus. We present 2-D gel electrophoretograms of 25 nL of plasma, as well as their automatic computer analysis. For comparison, a conventional 2-D gel electrophoresis profile of 200 nL of a plasma sample is shown. The technique is easy to perform, highly sensitive, rapid, and potentially useful in semi-routine clinical chemistry laboratories.

Autoanalysis↗
PubMed1988

Protein heterogeneity of lipoprotein particles containing apolipoprotein A-I without apolipoprotein A-II and apolipoprotein A-I with apolipoprotein A-II isolated from human plasma.

The protein heterogeneity of fractions isolated by immunoaffinity chromatography on anti-apolipoprotein A-I and anti-apolipoprotein A-II affinity columns was analyzed by high resolution two-dimensional gel electrophoresis. The two-dimensional gel electrophoresis profiles of the fractions were analyzed and automatically compared by the computer system MELANIE. Fractions containing apolipoproteins A-I + A-II and only A-I as the major protein components have been isolated from plasma and from high density lipoproteins prepared by ultracentrifugation. Similarities between the profiles of the fractions, as indicated by two-dimensional gel electrophoresis, suggested that those derived from plasma were equivalent to those from high density lipoproteins (HDL), which are particulate in nature. The established apolipoproteins (A-I, A-II, A-IV, C, D, and E) were visible and enriched in fractions from both plasma and HDL. However, plasma-derived fractions showed a much greater degree of protein heterogeneity due largely to enrichment in bands corresponding to six additional proteins. They were present in trace amounts in fractions isolated from HDL and certain of the proteins were visible in two-dimensional gel electrophoresis profiles of the plasma. These proteins are considered to be specifically associated with the immunoaffinity-isolated particles. They have been characterized in terms of Mr and pI. Computer-assisted measurements of protein spot-staining intensities suggest an asymmetric distribution of the proteins (as well as the established apolipoproteins), with four showing greater prominence in particles containing apolipoprotein A-I but no apolipoprotein A-II.

Apolipoprotein A-I↗
PubMed1987

Vasopressin and angiotensin induce inositol lipid breakdown in rat adenohypophysial cells in primary culture.

Adenohypophysial cells from female Wistar rats were dispersed and maintained for 4 days in primary culture in the presence of [3H]myoinositol. The effects of several releasing hormones, corticotropin-releasing factor (CRF), arginine vasopressin (AVP), angiotensin II (A II), thyrotropin-releasing hormone (TRH), and luteinizing hormone-releasing hormone (LHRH) on the liberation of labelled inositol phosphate (InsP), inositol-bisphosphate (InsP2), and inositol-trisphosphate (InsP3) from prelabelled inositol lipids were tested alone and in combination. Of the corticotropin (ACTH) secretagogues tested, AVP and A II produced a dose-dependent increase in inositol phosphate accumulation. CRF was inactive. The ED50 values of about 1 nM for both AVP and A II were close to the corresponding dissociation constants for binding to pituitary membranes: and, in the case of A II, close to the ED50 for A II-induced inhibition of pituitary membrane adenylate cyclase. The responses to A II and AVP could be inhibited by [Sar1,Ile8]A II and the AVP antagonist d(Et2)-VAVP, respectively. The magnitude of the maximal effect of AVP on accumulation of inositol phosphates was small (25% increase over basal value) suggesting that this effect was restricted to a minor subpopulation of pituitary cells (probably corticotrophes). CRF did not potentiate AVP-induced inositol phosphates accumulation. Maximal A II-induced increase in inositol phosphates accumulation represented 150% of the basal value and was partially additive with that of TRH suggesting that lactotrophes represent the main A II-sensitive subpopulation.

Adrenocorticotropic Hormone↗
PubMed1987

Role of angiotensin in sodium appetite of sodium-deplete sheep.

The role of the renin-angiotensin system (RAS) in the Na appetite of Na-deplete sheep was investigated. Intravenous infusion of the angiotensin-converting enzyme inhibitor, captopril, at 0.01 or 0.1 mg X kg-1 X h-1 did not cause any change in Na intake, although the higher dose caused a marked decrease in mean arterial blood pressure. Intravenous infusion of captopril at 1.0 mg X kg-1 X h-1 over 24 h decreased Na intake by 45-55% in the absence of any change in Na loss. The decrease in Na intake was restored to base-line level or above by concurrent intravenous infusion of angiotensin II (ANG II) at 3.8 or 24 micrograms/h over 24 h but not by intracerebroventricular (ICV) ANG II at 3.8 micrograms/h. In addition, ICV infusion of 0.7 M mannitol (1 ml/h over 3 h), which reduced cerebrospinal fluid (CSF) and brain extracellular fluid [Na], still increased Na intake when combined with intravenous captopril. Water intake was not altered during intravenous captopril or ANG II alone but was increased during ICV ANG II or 0.7 M mannitol (with or without iv captopril). In conclusion, these results suggest that the RAS is involved in the Na appetite of the Na-deplete sheep. Furthermore, it would appear that the brain area involved is one without a blood-brain barrier but with a CSF-brain barrier, such as one of the circumventricular organs. Also, it would appear that the effect of lowered cerebral Na and the effect of activation of the renin-angiotensin system on Na appetite are independent.

Angiotensin II↗
PubMed1987

Angiotensin II potentiates corticotropin-releasing activity of CRF41 in rat anterior pituitary cells: mechanism of action.

In this work the ability of angiotensin II (AII) to potentiate the corticotropin-releasing activity of ovine CRF41 (CRF) and the intracellular mechanism responsible for this effect are described. In perfused rat anterior pituitary cells, AII (10(-8)M) was found to potentiate the corticotropin-releasing activity of CRF producing a parallel shift of the dose-response curve. Similar results for ACTH release were observed in monolayer cell cultures. In this system, the concentration of cAMP was measured and was shown to be increased in the presence of CRF with a maximal value (2.5-fold greater than control) after 5-10 min incubation. On the other hand, AII at a dose inducing ACTH release (10(-7)M), had no effect on basal cAMP concentration, but when given simultaneously with CRF, potentiated the CRF-induced cAMP production (1.9-fold greater than CRF value). These results indicate that AII potentiates the corticotropin-releasing activity of CRF and that this effect is preceded by a similar increase in the CRF-induced cAMP production.

Angiotensin II↗
PubMed1987

Long-term effects of ACTH combined with angiotensin II on steroidogenesis and adrenal zona glomerulosa morphology in the rat.

To test the hypothesis that the trophic action of angiotensin II on the adrenal zona glomerulosa may allow a sustained stimulation of aldosterone by ACTH by preventing the morphological changes of the zona glomerulosa cells into zona fasciculata-like elements we investigated the effects in rats of a 6-day treatment with ACTH (100 micrograms/kg/day) alone or combined with angiotensin II (300 ng/kg/day) on corticosterone and aldosterone production and adrenal morphology. The responsiveness of both steroids to an acute ACTH dose was also studied on the last day of long-term treatment. Morphologic data showed that prolonged ACTH treatment stimulated the growth of zona glomerulosa cells, though it transformed the tubulo-lamellar cristae of mitochondria into a homogeneous population of vesicles. Angiotensin II furthered the trophic effects of ACTH but prevented the mitochondrial transformation. Despite its ability to conserve the well differentiated aspect of the zona glomerulosa cells, the administration of angiotensin II was unable to prevent the fall in the secretion of aldosterone caused by chronic ACTH treatment and its subsequent unresponsiveness to ACTH stimulation.

Adrenal Glands↗
PubMed1987

cAMP-dependent ACTH secretagogues facilitate corticotropin releasing activity of angiotensin II on rat anterior pituitary cells in vitro.

Both arginine vasopressin (AVP) and angiotensin II (AII) potentiate the corticotropin-releasing activity of CRF41 via a potentiation of CRF41-induced cAMP production. In perfused rat anterior pituitary cells, AII (10(-8) mol) showed a transitory 2-fold increase in its ACTH-releasing activity, when tested after application extract of rat stalk median eminence. In order to determine whether this facilitating effect on AII corticotropin-releasing activity occurred through cAMP-dependent mechanisms, the ACTH-releasing activity of AII was tested after stimulation with CRF41, AVP or forskolin, three secretagogues with known effects on cAMP production. When given 16 min after CRF41, 10 micrograms/l, AII (10(-8) mol) showed a significant increase (210%) in its ACTH-releasing activity, which returned to the normal level when AII-stimulation was repeated at 32 min (121%) and 48 min (100%). Similarly, forskolin, 3 X 10(-6) mol, produced a significant transitory increase (208%) in the subsequent AII-induced ACTH release whereas AVP, 10 micrograms/l and 100 micrograms/l, had no effect on the following ACTH response to AII. These results suggest that the AII-induced ACTH secretion--which is cAMP independent--nevertheless may be modulated by previously stimulation of the cAMP pathway.

Adrenocorticotropic Hormone↗
PubMed1986

Anatomical localization of corticotropin-releasing activity in the human brain.

Corticotropin-releasing activity (CRa) and arginine-vasopressin (AVP) content were measured in seven human hypothalami. The hypothalami were obtained from routine autopsy of patients suffering from no obvious neuroendocrinological abnormality. Twelve distinct hypothalamic areas were dissected in the frozen state and extracted in aqueous solution. CRa was measured by a bioassay measuring the aCTH released by rat pituitary cells in vitro, and vasopressin by direct radioimmunoassay. CRa was detectable in almost every area with the highest values in the supraoptic, paraventricular and infundibular (arcuate) areas. Vasopressin concentrations were maximum in the supraoptic nucleus, followed by the paraventricular and infundibular nuclei. We conclude that: hypothalami obtained from routine autopsy at a general hospital can be used for consistent CRa and vasopressin assay. Vasopressin and CRa are similarly distributed in man and in the rat. In both species, high CRa, which is not explained by AVP, is found in the paraventricular nucleus. The infundibular (arcuate) nucleus seems to display non AVP-dependent CRa much greater in the human than in the rat.

Adrenocorticotropic Hormone↗
PubMed1986

[Protein mapping of normal circulating cells: lymphocytes and monocytes].

Purified lymphocyte and monocyte populations were obtained from peripheral blood cells by ficoll-hypaque gradient and elutriation in different normal individuals. The two types of mononuclear cells were then analyzed by 2-dimensional gel electrophoresis. More than 1,000 spots were detected by our computer system and analyzed for each cell type. Automatic picture comparison showed a typical pattern for the two different populations with excellent reproducibility.

Blood Protein Electrophoresis↗
PubMed1986

Angiotensin and Na appetite of sheep.

The effect of both intravenous (iv; 24 micrograms/h) and intracerebroventricular (ivt; 3.8 micrograms/h) infusion over 1-2 days of angiotensin II (ANG II) on Na intake of both Na-replete and -deplete sheep (i.e., 22 h loss of parotid saliva) was observed. In Na-replete sheep with continuous access to water and 2-h daily access to 0.5 M NaCl solution, both iv and ivt ANG II caused an increase in Na intake. The increase in Na intake caused by iv or ivt ANG II was preceded by a Na deficit due to increased urinary Na excretion. The increase in Na intake was eliminated by the continuous return of urine. In Na-deplete sheep with continuous access to water and 2-h daily access to 0.6 M NaHCO3 solution, iv ANG II caused no change in Na loss but a small increase in Na intake during the 1st day of infusion. The ivt ANG II caused no change in Na loss or in Na intake. The iv ANG II caused a small and inconsistent increase in water intake in Na-replete sheep but did not cause any change in water intake of Na-deplete sheep. The ivt ANG II caused a large increase in water intake in both Na-replete and -deplete sheep. In both Na-replete and -deplete sheep, iv ANG II did not alter cerebrospinal fluid or plasma [Na] or osmolality but decreased plasma [K]. The ivt ANG II decreased both cerebrospinal fluid and plasma [Na] and osmolality. The results of the present experiments are consistent with the proposition that the ANG II-induced Na appetite in sheep is largely due to an ANG II-induced Na loss preceding the development of appetite.

Angiotensin II↗
PubMed1986

Vasopressin antagonists allow demonstration of a novel type of vasopressin receptor in the rat adenohypophysis.

The ligand specificity of rat adenohypophyseal vasopressin receptors was directly compared to that of peripheral receptors of the V1 and V2 types. For this purpose a series of 15 recently designed vasopressin antagonists was used. The affinities of these antagonists for rat adenohypophyseal membranes were deduced from the determination of the concentration-dependent inhibition of [3H]vasopressin binding. In parallel experiments the corticotropin (or anti-corticotropin)-releasing activities of the tested peptides were determined on freshly dispersed rat adenohypophyseal cells. All peptides tested which were found to be antagonists of the vasopressor and antidiuretic responses to vasopressin in vivo behaved as antagonists of vasopressin-induced corticotropin release. There was a close correlation between the relative affinities of the analogues tested for binding to adenohypophyseal membranes and their relative potencies in inhibiting vasopressin-induced corticotropin release, indicating that the detected vasopressin-binding sites are the receptors involved in the vasopressin effect on corticotropin secretion. No correlation could be demonstrated between anti-corticotropin-releasing activities and either anti-antidiuretic or antivasopressor potencies of the antagonists tested. A direct comparison of the ligand specificities of adenohypophyseal receptors on the one hand, and V1 (hepatic) and V2 (renal) receptors on the other hand, showed that most of the antagonists discriminated very efficiently between adenohypophyseal and either hepatic or renal receptors. The selectivity index reaches values as high as 260,000 for desGly(NH2)9 [1-(beta-mercapto-beta, beta-cyclopentamethylenepropionic acid), 2-D-O-ethyl-tyrosine, 4-valine] arginine vasopressin. It is concluded that adenohypophyseal receptors represent a novel type of vasopressin receptors. Based on the observation that adenohypophyseal receptors, like hepatic or vascular V1 receptors, do not appear to be coupled to adenylate cyclase, we propose that adenohypophyseal receptors could be designated as V1b receptors as opposed to the V1a receptors previously characterized on liver and blood vessels.

Adrenocorticotropic Hormone↗
PubMed1985

Cerebrospinal fluid sodium concentration and salt appetite.

Infusion into a lateral brain ventricle (IVT) of different hypertonic (0.7 M) saccharide solutions decreased [Na+] of cerebrospinal fluid (CSF). Increased Na appetite of moderately Na-deplete sheep was observed during infusion of mannitol, L-glucose or L-fucose, while no change was observed during infusion of D-glucose, D-fucose, D-mannose, 2-deoxy-D-glucose, 3-O-methyl-glucose or fructose. In other experiments, increased Na appetite was observed during infusion of 2.3 mM phlorizin (a relatively specific blocker of Na-coupled glucose transport into cells) or 2.3 mM phlorizin plus 0.7 M D-glucose. In addition, phlorizin eliminated the characteristic decrease in Na appetite but did not affect the increase in water intake caused by IVT infusion of hypertonic NaCl which increased [Na+] of CSF. The results suggest that: (a) there are sensors within the neuropil which respond to change of [Na+] and influence Na appetite, and that these changes of [Na+] are induced deep within the neuropil by those saccharides which do not cross the blood-brain barrier or enter cells; change of CSF[Na+] alone is not sufficient to alter appetite but a change in brain extracellular fluid (ECF)[Na+] is probably necessary; (b) the theory is advanced that the stimulus for altered Na intake could be altered brain ECF[Na+] producing a change in cerebral intracellular fluid (ICF)[Na+] of the sensors; and (c) phlorizin, in reducing or blocking Na-coupled glucose transport, could increase Na appetite by producing a fall in ICF[Na+] of the specific neurones subserving sodium appetite or prevent a decrease in Na appetite caused by IVT infusion of hypertonic NaCl by preventing an increase in ICF[Na+] of this same neuronal system.

Animals↗
PubMed1985

Corticotropin-releasing activity of the renin-angiotensin system peptides in rat and in man.

In this study we investigated in the rat the binding and corticotropin-releasing factor (CRF) activity of various constituents of the renin-angiotensin system and the possible angiotensin II receptor changes following procedures known to alter plasma renin activity. We investigated also the CRF activity of angiotensin II in vitro and in vivo in humans. The CRF activity of peptides was studied by their ability to stimulate ACTH release from pituitary cells. Deleting amino acids from the N-terminus of angiotensin II resulted in decreased CRF activity; while the ED50 for angiotensin II was 2 nM, it increased to about 10 nM for the (2-8)-heptapeptide. Angiotensin I had a weak CRF activity, whereas the substrate angiotensinogen had no stimulatory effect even at a concentration of 100 nM. There was a strong correlation between the activation and binding properties of all peptides tested. Dietary salt load or depletion as well as dexamethasone treatment did not affect the number nor the affinity of pituitary angiotensin II receptors. Angiotensin II had a CRF activity on human pituitary cells in vitro. However, peripherally injected agiotensin II at a pressive dose of 7 ng/kg/min did not produce any ACTH release in normal male volunteers. These data suggest that angiotensin II may play a modulatory role in the physiological regulation of ACTH secretion, but this role might be attributed to the endogenous brain angiotensin II as it is not closely dependent on the angiotensin II plasma levels.

Adrenocorticotropic Hormone↗
PubMed1984

RU 486: a steroid with antiglucocorticosteroid activity that only disinhibits the human pituitary-adrenal system at a specific time of day.

RU 486 is a synthetic steroid hormone antagonist which acts at the receptor level. It has both intrinsic anti-progesterone and antiglucocorticosteroid properties in animals. We investigated the antiglucocorticosteroid activity in humans by evaluating the pituitary-adrenal response to RU 486 in men and in pregnant and nonpregnant women. In non-pregnant women, RU 486 (approximately equal to 1 mg/kg of body weight per day) produced an interruption of the luteal phase without affecting the pituitary-adrenal axis, thereby indicating a more potent anti-progesterone than antiglucorticosteroid effect. In the course of pregnancy interruption by RU 486 (approximately equal to 4 mg/kg per day), there was a significant increase in plasma corticotropin, beta-lipotropin, and cortisol concentrations. In normal men, RU 486 administration led to a dose-dependent stimulation of plasma corticotropin, beta-endorphin, and cortisol. This disinhibition of the pituitary-adrenal axis was only observed during the morning hours of the circadian rhythm. When administered concomitantly with 1 mg of dexamethasone at midnight, 6 mg of RU 486 per kg completely suppressed the dexamethasone inhibitory effect on the pituitary-adrenal axis. These results indicate that RU 486 is an antiglucocorticosteroid that disrupts the negative pituitary feedback of both the morning cortisol rise and administered dexamethasone. Furthermore, they demonstrate the possibility of optimizing the anti-progestational effect of the compound and its potential use for human fertility control by modifying the dose and the time of administration of the drug and thereby minimizing the antiglucocorticosteroid effect.

Abortifacient Agents, Steroidal↗
PubMed1984

Properties of rat anterior pituitary vasopressin receptors: relation to adenylate cyclase and the effect of corticotropin-releasing factor.

Crude plasma membrane fractions were prepared from female Wistar rat anterior pituitaries. These fractions contained a single population of specific 3H-labeled [8-lysine]vasopressin [( 3H]vasopressin) binding sites with a dissociation of constant (Kd) of 8 +/- 2 X 10(-9) M and maximal binding capacity of 244 +/- 45 fmol/mg of protein. The Kd values for a series of vasopressin structural analogues with selective vasopressor or antidiuretic activities were determined together with the corresponding corticotropin-releasing activities (isolated perfused pituitary cells were used). A good correspondence was found between the two sets of values, suggesting that the detected vasopressin binding sites are the receptors involved in vasopressin-induced corticotropin release. The order of potency of these analogues for the binding to hypophysial receptors was similar to that found for the binding to the receptors involved in the vasopressor response. Corticotropin-releasing factor and angiotensin did not affect vasopressin binding to pituitary membranes. Median eminence extracts inhibited [3H]vasopressin binding with an efficiency very close to that expected from their vasopressin content. Corticotropin-releasing factor activated, and angiotensin inhibited, the adenylate cyclase activity of pituitary membranes. Under the same experimental conditions, vasopressin did not influence adenylate cyclase activity nor did it affect the corticotropin-releasing factor-induced activation. These data support the view that vasopressin is one component of the multifactorial regulation of corticotropin release and that it acts through a cAMP-independent pathway. The potentiation by vasopressin of corticotropin-releasing factor-induced cAMP accumulation in intact cells very likely proceeds through indirect mechanisms, which are not expressed in broken cell preparations.

Adenylyl Cyclases↗
PubMed1983

Lowered cerebrospinal fluid sodium antagonizes effect of raised blood sodium on salt appetite.

Moderately Na-deficient sheep (i.e., Na deficit = 300-400 mmol) will correct their deficit when given hypertonic NaHCO3 solution to drink. Access to NaHCO3 was provided by bar press for 2 h only each day following 22 h of salivary loss from a parotid fistula. Each delivery by bar press provided 9 mmol of NaHCO3 and, of the 46.3 +/- 2.5 deliveries made and drunk in 2 h, 80-90% were made in the first 20 min. Ten minutes before access to NaHCO3 commenced an intracarotid infusion of 4 M NaCl at 1.6 ml/min for 30 min was initiated. This infusion reduced intake by approximately 80% and increased both plasma and cerebrospinal fluid sodium concentration (CSF[Na]). Intraventricular (ivt) infusion of 0.7 M mannitol in artificial CSF at 1 ml/h for 3 h begun 1 h before access to Na by bar press lowered CSF[Na] and approximately doubled voluntary Na intake. The combination of the two procedures resulted in NaHCO3 intake similar to base line. That is, the ivt infusion of 0.7 M mannitol counteracted the inhibition of Na appetite produced by the systemic infusion of hypertonic NaCl, and this was associated with attenuation of the effect of the systemic 4 M NaCl infusion on CSF[Na]. The results suggest that the effects of both the ivt and the systemic infusions are mediated via the same sensor system located within the neuropil.

Animals↗