Biomedical subjects

E Malta

Publications and source records attributed to E Malta.

At least 19 recordsLinked to original sources

PubMed2000

A phase I/II trial of recombinant methionyl human brain derived neurotrophic factor administered by intrathecal infusion to patients with amyotrophic lateral sclerosis.

BACKGROUND: Brain derived neurotrophic factor (BDNF) is a potent survival factor for motoneurons. This study investigated the safety and tolerability of recombinant methionyl human BDNF (r-metHuBDNF) infused intrathecally by means of an implanted pump in patients with ALS. METHODS: Twenty-five patients with probable or definite ALS were treated with either r-metHuBDNF (25, 60, 150, 400 or 1000 microg/day) or placebo in a 12-week, randomized, double-blinded, sequential, dose-escalation study. Test treatment was interrupted by a washout period from days 11 to 25 to allow the evaluation of laboratory safety measures. In each dose cohort four patients received r-metHuBDNF and one received placebo. On completion of the double-blind period of the study all patients continued to receive r-metHuBDNF in an open-label extension for up to 60 weeks. Lumbar cerebrospinal fluid (CSF) samples were taken periodically from all patients for the measurement of r-metHuBDNF levels and in a minority of patients these were supplemented by cistemal samples. RESULTS: Within days after the initiation of infusion the majority of patients receiving r-metHuBDNF reported mild sensory symptoms, including paraesthesias or a sense of warmth, which were usually confined to the lower limbs and were frequently exacerbated by neck flexion. In most instances these symptoms decreased or even disappeared over several weeks. Sleep disturbance, dry mouth, agitation and other behavioural effects were encountered at higher doses (>150 microg/day) and necessitated dose reductions. The spinal CSF levels of r-metHuBDNF were directly related to dose, with a lumbar to cervical ratio of approximately 4:1. CONCLUSIONS: The intrathecal delivery of r-metHuBDNF in doses of up to 150 microg/day was well tolerated and appears feasible. The reversible CNS effects with higher dose indicate that BDNF can be delivered cranially against CSF flow. The small number of patients and the design of the study did not permit conclusions to be drawn about the efficacy of the treatment.

Adult↗

PubMed1999

The ALSFRS-R: a revised ALS functional rating scale that incorporates assessments of respiratory function. BDNF ALS Study Group (Phase III).

The ALS Functional Rating Scale (ALSFRS) is a validated rating instrument for monitoring the progression of disability in patients with amyotrophic lateral sclerosis (ALS). One weakness of the ALSFRS as originally designed was that it granted disproportionate weighting to limb and bulbar, as compared to respiratory, dysfunction. We have now validated a revised version of the ALSFRS, which incorporates additional assessments of dyspnea, orthopnea, and the need for ventilatory support. The Revised ALSFRS (ALSFRS-R) retains the properties of the original scale and shows strong internal consistency and construct validity. ALSFRS-R scores correlate significantly with quality of life as measured by the Sickness Impact Profile, indicating that the quality of function is a strong determinant of quality of life in ALS.

Activities of Daily Living↗

PubMed1999

Inhibition by dipyridamole of neutrophil adhesion to vascular endothelium during coronary bypass surgery.

BACKGROUND: Release of reactive oxygen radicals by activated neutrophils and neutrophil adhesion to endothelial cells have been observed after cardiopulmonary bypass. The aim of the present study was to evaluate the effects of preoperative dipyridamole treatment on neutrophil superoxide anion generation and endothelial cell-neutrophil interactions. METHODS: Two groups of patients scheduled for elective coronary artery bypass grafting were randomized to receive oral dipyridamole or a placebo. Nitro blue tetrazolium scores of circulating neutrophils, neutrophil CD11b/CD18 expression, and their adhesion to human umbilical vein endothelial cells were assayed before anesthesia, 30 minutes after the beginning of cardiopulmonary bypass, at the end of bypass, and 60 minutes postoperatively. RESULTS: In both groups, cardiopulmonary bypass resulted in a significant increase in nitro blue tetrazolium scores in circulating neutrophils as well as a significant increase in both neutrophil CD11b/CD18 expression and neutrophil adhesion to endothelial cells. The extent of neutrophil superoxide anion generation was higher in the control group; a significant (p < 0.01) reduction in neutrophil adhesion to endothelial cells was observed 1 hour postoperatively in the dipyridamole group. In 5 patients treated with dipyridamole, the incubation of activated polymorphonuclear leukocytes with adenosine deaminase significantly increased their adhesion to endothelial cells (p < 0.05). CONCLUSIONS: Our study demonstrated that preoperative treatment with oral dipyridamole significantly reduces both neutrophil superoxide anion generation and extent of neutrophil adhesion to endothelial cells after coronary bypass grafting procedures with cardiopulmonary bypass. The mechanism is probably mediated by endogenous adenosine.

Adenosine Deaminase↗

PubMed1995

The biopharmaceutical industry and new drugs for amyotrophic lateral sclerosis.

These are but a few of the controversies and pressures facing Sponsors of clinical trials in ALS. All researchers in the area share the hope that the current level of interest in clinical trials in ALS will lead to the development of effective therapies for this disease. It should be recognized that the long-term goal of all groups involved in ALS trials is the establishment of effective therapies.

Amyotrophic Lateral Sclerosis↗

PubMed1993

Influence of albumin on isoprenaline and propranolol effects on isolated rat uterus.

We investigated the effect of albumin (6%) on the (+/-)-isoprenaline-induced relaxation of strips of isolated rat uterus and its antagonism by (-)-propranolol. The mean isoprenaline EC50 in the presence of albumin was significantly less than that in the absence of albumin (geometric mean 1.94 +/- 3.33 versus 3.21 +/- 3.50 nM, respectively; n = 14; p = 0.006, paired t test). This indicates enhancement of isoprenaline activity by albumin which could not be explained by protein binding, as this would have reduced activity. Geometric mean control KB values for inhibition of isoprenaline by propranolol at 26.8 and 500 nM were 0.835 +/- 1.68 (n = 10) and 0.889 +/- 1.60 nM (n = 34), respectively. In the presence of 6% albumin, KB for propranolol was increased significantly to 13.3 +/- 1.8 nM (n = 27, p < 0.001). Calculation of KB in terms of the measured propranolol unbound concentration of 26.8 nM, after taking into account the lower isoprenaline EC50 in the presence of albumin, yielded a mean value of 0.725 +/- 1.86 nM, which was not significantly different from either control (p > 0.05). Therefore, propranolol activity was as predicted by the unbound drug concentration in contrast to isoprenaline activity. We conclude that albumin can alter in vitro drug activity by mechanisms in addition to the reduction of unbound drug concentration.

Animals↗

PubMed1991

Oxyhaemoglobin increases the production of endothelin-1 by endothelial cells in culture.

Cultured endothelial cells from bovine thoracic aortas conditioned with serum-free culture media released an endothelin-1 (ET)-1-like substance. Concentrations of ET-1-like material were determined by bioassay as contractions of isolated ring segments of dog internal mammary vein and by radioimmunoassay. ET-1-like immunoreactivity (ET-1-IR) increased progressively over a 24 h conditioning period and correlated with the bioassay for the first 12 h. Oxyhaemoglobin (1-3 microM) caused a significant two-fold increase in the concentration of ET-1-IR in the medium at 6, 8 and 12 h incubation. Methaemoglobin also caused an approximate doubling of the amount of ET-1-IR at eight h of incubation. NG-Monomethyl-L-arginine (L-NMMA), a blocker of the production of endothelium-derived relaxing factor (EDRF), had no effect on the time-dependent increase in ET-1-IR in the conditioned medium. These results may have important implications for the mechanisms underlying vascular smooth muscle hyperreactivity such as cerebral spasm following subarachnoid haemorrhage.

Animals↗

PubMed1989

Studies on the biphasic relaxant curve of glyceryl trinitrate in rat aorta: role of GTN metabolites.

1. The present study has examined the possibility that one or more metabolites of glyceryl trinitrate (GTN) (i.e. glyceryl-1,2- and -1,3-dinitrate and glyceryl-1- and -2-mononitrate) may be responsible for the second phase of the biphasic relaxant curve to GTN in phenylephrine-contracted rings of rat aorta. 2. The IC50 values for the two phases of the GTN curve were 0.1 mumol/L and 12 mumols/L with the initial phase eliciting 60% of the total relaxation response. The curves for glyceryl-1,2- and -1,3-dinitrate were monophasic with IC50 values of 248 mumols/L and 110 mumols/L, respectively. The mononitrate metabolites elicited relaxant effects at concentrations greater than or equal to 1 mmol/L. 3. The induction of tolerance to GTN or pretreatment with oxyhaemoglobin (5 mumol/L) resulted in a monophasic GTN curve with IC50 values of 16 mumol/L and 18 mumol/L respectively suggesting selective abolition of responses to low concentrations of GTN with little effect on responses to high concentrations of GTN. The relaxant effects of the -1,2- and -1,3-dinitrates, like that to GTN, were essentially unaltered by GTN tolerance or oxyhaemoglobin. 4. Thus while the relaxant effects of the dinitrate metabolites possess similar properties to that of the second phase of relaxation to GTN, a role for these metabolites is unlikely since their IC50 values are 9-20-fold greater than that for the second phase of relaxation to GTN. Whether these differences are due to the 8-10-fold lower lipophilicity of the dinitrates as compared with the parent compound requires further study.

Animals↗

PubMed1989

Organ-bath studies using the irreversible beta-adrenoreceptor antagonist bromoacetylalprenololmenthane (BAAM).

1. The effects of the irreversible beta-adrenoreceptor antagonist bromoacetylalprenololmenthane (BAAM) were studied in isolated cardiac and uterine preparations from guinea-pigs and rats and in guinea-pig ileal preparations. 2. In the presence of BAAM (0.1-10 microM) concentration-effect curves to (-)-isoprenaline were shifted to the right in a concentration-dependent manner in all cardiac and uterine tissues. Maximum responses to (-)-isoprenaline were unaffected by BAAM except in guinea-pig left atrial and in some guinea-pig uterine preparations; however, the reductions in the maximum responses were not concentration-dependent. The mean pKB values for BAAM in guinea-pig left atria, right atria, rat whole atria and rat uterus were 7.26, 7.24, 6.84 and 7.90 respectively. 3. In guinea-pig ileal preparations, BAAM (0.1-30 microM) relaxed contractions induced by K+, histamine and acetylcholine in a non-beta-adrenoreceptor-related manner since relaxant responses were unaffected by propranolol (0.5 microM). In other tissues higher concentrations of BAAM (30-100 microM) elicited atrial standstill and depressed K+-induced contractions in uterine smooth muscle. 4. Treatment of tissues with BAAM (10-100 microM) followed by extensive wash-out increased the EC50 values for (-)-isoprenaline 21- to 83-fold. The maximum response to the catecholamine was unaffected by BAAM except in guinea-pig left atrial preparations following treatment with 100 microM BAAM. At these concentrations BAAM markedly increased the effective refractory period. 5. Concentration-effect curves for the partial agonist, oxymethylene-isoprenaline (OM-ISO) were shifted to the right 12- to 355-fold after pretreatment of tissues with BAAM (10-30 microM) followed by wash-out. The maximum response to OM-ISO was unaltered in guinea-pig and rat uteri and was reduced to a similar degree as observed with (-)-isoprenaline in guinea-pig left atria. 6. In general, the non-selective beta-adrenoreceptor antagonist BAAM depressed maximum responses to beta-adrenoreceptor agonists only in cardiac preparations and at concentrations which elicited depressant activity. On the basis of the present study, BAAM does not appear to be a suitable irreversible beta-adrenoreceptor antagonist for use in organ bath experiments.

Adrenergic beta-Antagonists↗

PubMed1988

Inhibition of vascular smooth muscle relaxation by LY83583.

The ability of LY83583 to antagonize vascular smooth muscle relaxation elicited by a number of vasodilators was examined in rings of rat aorta. LY83583 (0.3-10 microM) inhibited relaxant responses to acetylcholine, calimycin (A23187), adenosine triphosphate (ATP) and sodium nitroprusside, whereas responses to atriopeptin III an activator of particulate guanylate cyclase, and papaverine were unaffected. For acetylcholine and calimycin the major effect of LY83583 (0.3-10 microM) was to reduce the maximal response without appreciably altering the EC50 values whereas for ATP the EC50 values were markedly increased by low concentrations of LY83583 (0.3-1 microM) with depression of maximal responses occurring at higher concentrations (10 microM) of the antagonist. In contrast LY83583 produced nonparallel rightward shifts of the curve for sodium nitroprusside without altering the maximal response. In addition, LY83583 (10 microM) reduced basal levels of cyclic GMP and prevented acetylcholine and sodium nitroprusside-induced elevations of cyclic GMP, in parallel with reductions in the relaxant responses. In the presence of LY83583 (10 microM) higher concentrations of sodium nitroprusside restored both the relaxant response and the elevation of cyclic GMP. The results of this study show that LY83583 antagonises only those vasodilators which are thought to act via stimulation of soluble guanylate cyclase. The nonsurmountable inhibition of relaxation to acetylcholine, calimycin and ATP probably reflects a limited maximal capacity of the endothelium to release EDRF in response to these agents.

Acetylcholine↗

PubMed1988

Studies on the specificity of the inhibitory action of N,N-diisopropyl-N'-isoamyl-N'-diethylaminoethylurea (P-286) on adrenal catecholamine release in the anaesthetized rat.

1. The ability of P-286 (N,N-diisopropyl-N'-isoamyl-N'-diethylaminoethylurea) to reduce selectively the release of catecholamines from the adrenal medulla has been studied in urethane-anaesthetized rats. 2. Pressor responses to acetylcholine (Ach) and the nicotinic receptor-agonist 1,4-dimethylphenylpiperazine (DMPP) in rats treated with atropine, (+/-)-propranolol and guanethidine were used as the index of adrenal catecholamine release. 3. The injection of P-286 (1-10 mg/kg, i.v.) elicited a dose-dependent bradycardia which was associated with hypotension. P-286 reduced pressor responses to Ach and DMPP in a dose-dependent manner with an IC50 of 2.5 mg/kg and, following near complete blockade, pressor responses to DMPP returned to 50% of control after 90 min. 4. In non-atropinized rats, P-286 (30 mg/kg, i.v.) was without effect on the bradycardic responses elicited by stimulation of the right vagus nerve at frequencies of 5-40 Hz while pressor responses to DMPP in bilaterally adrenalectomized, non-guanethidine treated rats were reduced by approximately 50% after P-286 (10 mg/kg, i.v.). 5. The latter effect of P-286 on responses to DMPP in adrenalectomized rats cannot be attributed to ganglionic blockade since in rats with intact adrenals P-286 (10 mg/kg, i.v.) also reduced pressor responses to i.v. adrenaline and i.v. angiotensin II by approximately 50%. Thus the reduction in response to DMPP in adrenalectomized rats and to the non-nicotinic agonists may be a reflection of an action on the mechanism of contraction of vascular smooth muscle; that is, at a post-receptor event. 6. The results of the study show that P-286 selectively reduces adrenal catecholamine release at doses which do not affect autonomic ganglia. Its usefulness as a tool in cardiovascular research, however, may be limited by an action of vascular smooth muscle.

Acetylcholine↗

PubMed1988

Autoradiographic localization and function of beta-adrenoceptors on the human internal mammary artery and saphenous vein.

1. Receptor autoradiography with (-)-[125I]-cyanopindolol (CYP) was used to study the distribution of beta 1- and beta 2-adrenoceptor subtypes in the human internal mammary artery and saphenous vein. 2. Images from X-ray film and nuclear emulsion coated coverslips, exposed to [125I]-CYP labelled sections, showed a high density of beta 2-adrenoceptors localized to the endothelium of the internal mammary artery and fewer beta 2-adrenoceptors on the smooth muscle. 3. The function of beta-adrenoceptors in ring preparations of the internal mammary artery was investigated in organ bath studies. (-)-Isoprenaline produced concentration-dependent relaxation of phenylephrine contracted rings. The potency and maximal effects of (-)-isoprenaline were not influenced by the presence of the endothelium. 4. Images of [125I]-CYP binding to the saphenous vein, from X-ray film and nuclear emulsion coated coverslips, showed localization of beta 2-adrenoceptors to the outer smooth muscle and not to the endothelium. 5. Relaxation of mammary artery and saphenous vein to (-)-isoprenaline is mediated via beta 2-adrenoceptors located on the smooth muscle. Endothelial beta 2-adrenoceptors, although present on the internal mammary artery, mediate other functions.

Aged↗

PubMed1987

Effect of endothelium and carbachol on alpha-adrenoceptor agonist stimulated uptake and efflux of 45Ca in rat isolated aorta.

Preincubation with carbachol (10 microM) did not affect basal 45Ca accumulation by rat isolated aortic segments complete with endothelium, although 45Ca accumulation was enhanced by removal of endothelium. This confirms the observation that in the presence of endothelium Ca2+ influx in rat aorta is antagonized, and indicates that the basal release of an endothelial derived factor might be sufficient to maximally antagonize basal Ca2+ influx, or alternatively that EDRF released as a result of muscarinic stimulation does not have identical effects to the factor released under basal conditions. Accumulation of 45Ca stimulated by B-HT 920 but not that stimulated by phenylephrine was antagonized in the presence of endothelium. Contractions elicited by B-HT 920 were abolished in the presence of endothelium while contractions evoked by phenylephrine were reduced by about 50%. Preincubation with 10 microM carbachol antagonized both phenylephrine (1 microM) stimulated 45Ca accumulation and contractile responses in the presence of endothelium to about the same extent. Therefore, it might be concluded that the inhibitory effect of EDRF in this tissue is due to an inhibition of stimulated Ca2+ influx. However, while addition of carbachol to tissues precontracted with phenylephrine elicited an immediate relaxation in the presence of endothelium, this relaxation could not be correlated with a reduction in tissue accumulation of 45Ca. Carbachol also antagonized the phenylephrine-induced reduction of tissue 45Ca content (i.e. efflux of Ca2+), in tissues preloaded with 45Ca. This implies that the initial endothelial-mediated relaxant effect of carbachol in precontracted tissues cannot be explained either by reduced influx or by an enhanced efflux of Ca2+ from the smooth muscle cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenergic alpha-Agonists↗

PubMed1986

Effect of endothelium on basal and alpha-adrenoceptor stimulated calcium fluxes in rat aorta.

The rate of unstimulated influx of Ca2+ into rat aorta smooth muscle, measured as uptake of 45Ca, was inhibited in the presence of endothelium as compared to influx in the absence of endothelium. Efflux of 45Ca from unstimulated prelabelled tissues was also reduced in the presence of endothelium. In normal physiological solution the rate of influx and efflux of Ca2+ stimulated by B-HT 920 (1 and 10 microM), but not that stimulated by phenylephrine (30 nM and 1 microM), was also reduced in the presence of endothelium. In the presence of the calcium entry blocker flunarizine (3 microM), phenylephrine (1 microM) stimulated efflux of Ca2+ was inhibited by the presence of endothelium. A correlation between inhibition of Ca2+ influx and modulation of alpha-adrenoceptor agonist-induced contractions by endothelium could not be demonstrated, and methylene blue, an antagonist of endothelium mediated inhibition of B-HT 920 contractions, did not affect Ca2+ influx stimulated by the agonist. The effects of endothelium on Ca2+ influx and efflux are unlikely to be due to alterations by endothelium of diffusion of 45Ca or the agonists in the vessel. The results demonstrate that an endothelial derived factor or factors can reduce calcium influx into smooth muscle cells and also modulate the release of calcium from cells, perhaps by affecting intracellular calcium pumping mechanisms. A reduction of calcium influx cannot be the sole explanation for the modulatory effect of endothelium on alpha-adrenoceptor agonist-induced contractions but an effect on intracellular calcium metabolism may be important.

Animals↗

PubMed1986

Analysis of agonist dissociation constants as assessed by functional antagonism in guinea pig left atria.

In electrically driven guinea pig left atria, positive inotropic responses to (-)-isoprenaline and the selective beta 1-adrenoceptor agonist RO363 were obtained in the absence and in the presence of the functional antagonists adenosine, carbachol, gallopamil, nifedipine, and Ro 03-7894. Each of the functional antagonists reduced the maximum response to both agonists and produced nonparallel rightward shifts in the cumulative concentration effect curves. For both agonists, dissociation constants (KA) were calculated using the equation described by Furchgott (1966) for irreversible antagonism. For RO363, which is a partial agonist with high agonist activity, the equations outlined for functional interaction by Mackay (1981) were also employed to calculate KA values. The KA values obtained by each method were compared with the dissociation constants (KD) for the two agonists determined from their ability to displace the radioligand (-)-[125I]iodocyanopindolol from beta 1-adrenoceptors in guinea pig left atrial membrane preparations. The estimates of KA varied substantially from KD values. The KD values were taken as more accurate estimates of the true values for the dissociation constants because a high degree of correlation exists between pKD and pD2 values for a number of other beta-adrenoceptor agonists that behave as partial agonists and between pKD and pKB values for a number of beta-adrenoceptor antagonists. Thus it appears that there are serious limitations in the current theory for using functional antagonism as a means of obtaining agonist dissociation constants.

Adenosine↗

PubMed1986

Investigation of the antimuscarinic and other actions of proadifen in-vitro.

The possibility that proadifen (SKF 525A) antagonizes endothelium-dependent relaxations to acetylcholine (ACh) in isolated blood vessel preparations via a muscarinic receptor blocking action has been investigated. In phenylephrine-contracted rat isolated aortic ring preparations (with endothelium), proadifen (10-100 microM) shifts ACh relaxant curves to the right without affecting the maximal response, yet endothelium-dependent relaxations to ATP are unaffected. At lower concentrations, proadifen (1-10 microM) antagonizes negative inotropic responses to ACh and ATP in guinea-pig left atria, antagonizes contractile responses to ACh and elevated [K+] in guinea-pig ileal preparations, displaces (-)-[3H]quinuclidinyl benzilate from muscarinic binding sites in membrane homogenates of guinea-pig ileal longitudinal muscle and reduces contractile responses to elevated [K+] in rat aortic ring preparations. It is concluded that proadifen may possess complex interactions with muscarinic receptors and Ca2+ entry blocking properties in concentrations 10-100 times lower than those reported to inhibit cytochrome P450-catalysed reactions.

Acetylcholine↗

PubMed1986

The affinity of some selective muscarinic receptor antagonists for the muscarinic receptor mediating endothelial-dependent relaxation of the rabbit and rat thoracic aorta.

The pKB values determined for pirenzepine, 4-DAMP, secoverine and gallamine against acetylcholine-mediated relaxant effects in rabbit aorta indicate that this muscarinic receptor closely resembles that which mediates contraction of non-vascular smooth muscle. The results of the present study argue against the presence of a novel type of muscarinic receptor mediating endothelium-dependent relaxation.

Acetylcholine↗

PubMed1986

Role of efficacy in the assessment of the actions of alpha-adrenoceptor agonists in rat aorta with endothelium.

Concentration-effect curves to phenylephrine are shifted to the right in the presence of endothelium in rat aorta while responses to clonidine are practically abolished. Analysis of the concentration-effect curves showed that the effect of endothelium could possibly be explained by a reduction in relative intrinsic efficacy of the two agonists by between 3.5- and 6-fold. Published observations on the modulatory effects of agonist-induced contractions by endothelium in the rat aorta tend to support this explanation. It is further concluded that this reduction in efficacy could be related to the basal release of an endothelium-derived substance and that changes in tissue contractility in the presence of endothelium cannot necessarily be taken as evidence for a stimulated liberation of endothelium-derived products by agonists.

Adrenergic alpha-Agonists↗

PubMed1985

Influence of assay buffer on dissociation constants of drugs at beta-adrenoceptor subtypes.

The present investigation has assessed the influence of assay buffer (Tris versus Krebs) on the abilities of several beta-adrenoceptor agonists and antagonists to displace the radioligand (-)-[125I]iodocyanopindolol [( 125I]CYP) from beta 1-(left atrial) and beta 2- (uterine) adrenoceptor sites. Saturation studies indicated that the dissociation constant (KD) for [125I]CYP at both beta-receptor sites was approximately 2-fold greater in Krebs as opposed to Tris buffer, and that the maximal density of binding sites (Bmax) in atria (but not uterus) was also reduced 2-fold. In general, the KD values for beta-adrenoceptor agonists were more influenced by the type of buffer used than were KD values for antagonists. Agonist KD values at beta 2-adrenoceptor sites were higher in Krebs than in Tris buffer, while at beta 1-adrenoceptor sites, variable changes resulted. The selective affinity of agonists at beta 1- and beta 2-adrenoceptor sites was therefore markedly influenced by the buffer used and could not be predicted from the established beta 1-/beta 2-adrenoceptor selectivity of the agonists as found in organ bath studies.

Adrenergic beta-Agonists↗