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M Paul

Publications and source records attributed to M Paul.

At least 199 records · Page 11Linked to original sources
PubMed1998

Vascular beta-adrenergic receptor adenylyl cyclase system from renin-transgenic hypertensive rats.

In transgenic rats harboring the mouse Ren-2d gene [TG(mREN2)27], downregulation of the myocardial beta-adrenergic receptor adenylyl cyclase system has been demonstrated previously. Because a reduced vasodilatory reactivity may significantly contribute to hypertension in this model of an activated tissue renin-angiotensin system, the present study investigated alterations of the vascular beta-adrenergic receptor adenylyl cyclase system. In freshly harvested aortas from transgenic rats, the activity of adenylyl cyclase was reduced significantly (P<.05) in the presence of isoprenaline (10 micromol/L; -28+/-4.5%), guanosine 5'-triphosphate, 5'-guanylylimidodiphosphate [Gpp(NH)p] (100 micromol/L; -29+/-4.7%), and forskolin (100 micromol/L) with (-42+/-6%) and without (-40+/-4.3%) MnCl2. Densities of beta-adrenoceptors were similar in both strains. In situ hybridization demonstrated the expression of the transgene in aortic smooth muscle cells. These data indicate a reduced catalyst function as a major contributing factor involved in the maintenance of high blood pressure in TG(mREN2)27. However, in cultivated aortic smooth muscle cells, cAMP production after stimulation with isoprenaline, forskolin, and Gpp(NH)p in the presence or absence of MnCl2 was not different. Affinities and densities of beta-adrenoceptors and amounts of immunochemically detected inhibitory and stimulatory G-protein alpha-subunits were unchanged. Desensitization after incubation with 10 micromol/L isoprenaline for 72 hours was identical in smooth muscle cells from both strains. Cell cultivation and isoprenaline treatment had no effect on transgene expression. We concluded that in transgenic rats the downregulation of the aortic beta-adrenergic adenylyl cyclase system is due to humoral and hemodynamic factors present in vivo rather than to transgenicity itself.

Adenylyl Cyclases↗
PubMed1998

Chamber-specific alterations of norepinephrine uptake sites in cardiac hypertrophy.

The present study investigated local differences of sympathetic activation and sympathetic neuroeffector defects in nonhypertrophied right and hypertrophied left ventricles in a rat model with renin-induced pressure overload [TG(mREN2)27]. As judged from the depletion of myocardial norepinephrine stores, sympathetic activation was more pronounced in the left than in the right ventricles. In addition, norepinephrine uptake1 carrier sites were reduced in left but unchanged in right ventricles. Gene expression of the carrier was unchanged in stellate ganglia. An increase of Gialpha expression and a heterologous adenylyl cyclase desensitization occurred only in the left but not in the right ventricles, whereas a reduction of beta-adrenergic receptors was observed in both chambers. We concluded that general sympathetic activation can lead to beta-adrenoceptor downregulation but that pressure overload further increases sympathetic activation involving norepinephrine uptake mechanisms in the left ventricles, resulting in heterologous beta-adrenergic desensitization.

Adenylyl Cyclases↗
PubMed1998

Physicochemical characteristics of pentamidine-loaded polymethacrylate nanoparticles: implication in the intracellular drug release in Leishmania major infected mice.

This work describes the preparation, the physicochemical properties, the tolerance and the intracellular trafficking of pentamidine loaded nanoparticles. Pentamidine was bound to the polymer by ionic interaction. This interaction involved the carboxylic acid functions of methacrylic acid (10% of the polymer) and the amine groups of the drug. Pentamidine fixation and release were pH dependent. An acidic pH led to a decrease of fixation or a release. At pH 5, which is the pH value of lysosomes and parasitophorous vacuoles, the release reached up to 50%. At this pH value, pentamidine is ionized and therefore can not traverse the biological membranes. Unloaded nanoparticles and pentamidine-loaded nanoparticles were tested in vitro on U937 cells and no cytotoxicity was observed. In vivo, in Leishmania infected mice, no significant weight loss was found. Ultrastructural studies showed the different steps of drug loaded nanoparticles trafficking inside Leismania-infected Küpffer cells. The nanoparticle uptake by macrophagic cells led to the location of nanoparticles inside phagocytosis vacuoles which fused with primary lysosomes to form secondary lysosomes. Ultimate fusion of secondary lysosomes containing nanoparticles with parasitophorous vacuoles was also observed. Nanoparticles were identified close to amastigotes but internalization by the parasite was not observed.

Animals↗
PubMed1998

Differential development of early hypertension in heterozygous transgenic TGR(mREN2)27 rats.

The aim of the study was to determine blood pressures in young heterozygous transgenic rats harbouring the Ren-2 mouse gene, TGR(mREN2)27, and to examine the association between blood pressure and plasma renin-angiotensin parameters during the conscious state. Two litters of heterozygous TGR(mREN2)27 rats and their normotensive Sprague-Dawley reference animals were bred in our laboratory. Cardiovascular phenotypes and blood, for the evaluation of plasma renin-angiotensin-system parameters, were obtained via arterial catheters in conscious rats 4 weeks after birth. Blood pressure values showed a high degree of interindividual variability and significant litter differences in the group of transgenic animals ranging from normotensive tohypertensive values. Plasma prorenin levels were markedly increased in TGR(mREN2)27, whereas both active renin and angiotensin II plasma concentrations were reduced independently from hypertension. Plasma prorenin levels in litter 2 of transgenic animals which exhibited significantly elevated blood pressures were significantly higher as compared to those of litter 1 which showed blood pressures that were not significantly different from SD. These data demonstrate that the development of hypertension in heterozygous TGR(mREN2)27 takes place in the fourth week of postnatal life and exhibits large interindividual variability. Moreover, development of early hypertension in young heterozygous TGR(mREN2)27 is associated with higher plasma prorenin levels.

Animals↗
PubMed1998

Endothelin converting-enzyme-1 mRNA expression in human cardiovascular disease.

Endothelin-1 converting-enzyme (ECE-1) cleaves the precursor, big-endothelin-1, to the active peptide endothelin-1. The aim of this study was to investigate whether ECE-1 mRNA expression is modified in human cardiovascular disease. Tissue samples from the left human atrium were analyzed for ECE-1 expression and related to different clinical parameters. A quantitative PCR assay (qPCR) with competitive and non-competitive standards was established. The ECE-1 measurements were normalized by a GAPDH qPCR. Patients who suffered from a myocardial infarction had elevated ECE-1 levels when compared to controls (5.81+/-0.76 vs. 3.20+/-0.51 fg ECE-1, ng GAPDH, p<0.05). Drug treatment with the beta-blocker metoprolol was associated with a decreased ECE-1 expression level (3.90+/-0.58 vs. 5.81+/-0.76 fg ECE-1, ng GAPDH, p<0.1). We conclude that the expression of ECE-1 is altered in the atrial tissue depending on the physiological status of the heart. This suggests a differential role of ECE-1 in cardiovascular diseases.

Adrenergic beta-Antagonists↗
PubMed1998

[Potential risk factors for Toxoplasma gondii infection in cases with recently acquired toxoplasmosis].

Investigation of potential risk factors for T. gondii infection was performed in 31 cases with a recently acquired toxoplasmosis in comparison with 34 seronegative patients as a control group. Epidemiological study was performed according to a questionnaire elaborated by European Research Network on Congenital Toxoplasmosis. Essential risk factors for toxoplasmosis in examined population were: consumption of raw pork (p < 0.00001), raw meat tasting during meal preparation (p < 0.00001), eating salami (p = 0.03), professional contact with meat (p = 0.02) and drinking milk (p = 0.02) or untreated water (p = 0.01). In seronegative controls more common were university education (p = 0.001), washing hands after handling raw meat (p = 0.04) and washing fruit and vegetables (p = 0.03).

Adolescent↗
PubMed1997

Phosphorylation of both phosphoacceptor sites in the HIV-1 Vpu cytoplasmic domain is essential for Vpu-mediated ER degradation of CD4.

Human immunodeficiency virus type 1 (HIV-1) Vpu is phosphorylated at two serine residues (Ser52 and Ser56) present within the acidic dodecapeptide region of the 54-aa cytoplasmic domain. Previous experiments have shown that Vpu phosphorylation is critical for the degradation of CD4 in the endoplasmic reticulum. In this study, we carried out experiments to elucidate the role of individual phosphoacceptor sites in CD4 proteolysis. We show here that acidic amino acids could not functionally substitute for phosphoserines in Vpu that is capable of inducing the degradation of CD4. Our studies have further revealed that phosphorylation of either of the two phosphoacceptor sites is not sufficient to generate a functional Vpu protein. When tested for functional complementation, inactive phosphorylation-proficient Vpu mutants failed to generate Vpu proteins that had the ability to induce the degradation of Vpu-sensitive glycoproteins. The failure to complement was not due to assembly defects in the Vpu protein as unphosphorylated Vpu formed oligomeric complexes in the cell. We also showed that Vpu expression inhibits protein transport in a phosphorylation-dependent manner. Our studies have thus revealed that both phosphoserines in Vpu are critical participants in a pathway that leads to the proteolysis of CD4 in the ER and that these phosphoserines should be present on the same subunit of the Vpu protein.

CD4 Antigens↗
PubMed1997

Occupational reproductive hazards.

Although the causes of many reproductive disorders remain unknown, scientific evidence is accumulating to implicate occupational agents in fertility disorders and adverse pregnancy outcomes. Effective assessment and management of workers exposed to reproductive hazards often involves a team-based approach. By identifying potential reproductive hazards, making appropriate referrals, and by educating and advocating for patients, clinicians can play an important part in safeguarding the reproductive health of workers.

Female↗
PubMed1997

Detection of specific Echinococcus granulosus antigen 5 in liver cyst bioptate from human patients.

Eighty one liver cyst fluid samples obtained by fine needle aspiration biopsy (FNAB) in human patients were examined for specific E. granulosus antigen 5 (Ag5). The patients were suspected cases of hepatic cystic echinococcosis (CE) but protoscolices and hooks had not been found in the cyst bioptates. Presence of Ag5 was tested for using enzyme linked immuno-sorbent assay (ELISA) technique with monoclonal antibody against Ag5. Sensitivity of the test was approximately 1 ng of antigen/1 ml of examined fluid. Positive results were obtained in the control group of six patients having protoscolices and/or hooks in biopsy samples from liver cysts. Positive Ag5 results were also obtained in the samples from 89 fertile cysts and 28 sterile cysts originated from 15 naturally infected pigs as an experimental control group. Ag5 was present in nine cases (11.1%) out of 81 liver cyst fluid samples from suspected CE patients. In 25 human patients the sensitivity of the microscopic examination for protoscolices and/or hooks in FNAB material was 64% (16/25). In pig hydatid cysts the sensitivity of the microscopic examination for protoscolices and/or hooks in FNAB material was 86.5% and of the detection of Ag5-100%. In conclusion, examination of hepatic cyst biopsy samples for specific Ag5 resulted in increased detection of liver echinococcosis in human patients.

Adolescent↗
PubMed1997

Cardiovascular end-organ damage in Ren-2 transgenic rats compared to spontaneously hypertensive rats.

To compare hypertensive end-organ damage in two genetic forms of hypertension we assessed cardiovascular function in two rat strains of genetic hypertension: transgenic rats overexpressing the mouse Ren-2 gene [(TGR(mREN2)27]) and blood pressure matched spontaneously hypertensive rats (SHR). Despite similarly elevated blood pressure, systolic dp/dt (mmHg/s) was more impaired in transgenic rats (3099 +/- 446) than in SHR (3571 +/- 272) and normals (4342 +/- 119; P < 0.05). Left ventricular weight (mg/g body weight) increased more in the transgenic rats (40 +/- 3) than in SHR (31 +/- 2) and normals (26 +/- 2). Endothelium-dependent relaxation was significantly decreased only in the transgenic rats. This study shows significantly more cardiac and endothelial dysfunction in transgenic, hypertensive TGR (mREN2)27 than in age and blood pressure matched SHR. This supports the hypothesis that chronic activation of the renin-angiotensin system significantly contributes to hypertensive end-organ damage.

Animals↗
PubMed1997

Evidence of alternative promoters directing isoform-specific expression of human endothelin-converting enzyme-1 mRNA in cultured endothelial cells.

The endothelins, a family of closely related vasoactive and mitogenic peptides, are thought to play an important role in cardiovascular pathophysiology. The conversion of the inactive precursor "big endothelin" to the biologically active peptide is catalyzed in vitro and in vivo by endothelin-converting enzymes (ECE). Recently the cDNA cloning of two homologous proteins, termed ECE-1 and ECE-2, has been reported. ECE-1 may play a key role in the activation and regulation of the cardiovascular endothelin proteolytic cascade. ECE-1 mRNA is expressed in two isoforms, termed alpha and beta, which are identical except for the 5'-terminal regions. To investigate the transcriptional regulation of isoform-specific ECE-1 mRNA expression we isolated phage clones from a human genomic library and identified the alpha- and beta-specific exons of ECE-1. The exon/intron organization of the 5'-terminal region of the human ECE-1 gene in conjunction with putative transcription initiation start sites suggests the existence of two alternative promoters, each directing the expression of either isoform. A reverse transcription/polymerase chain reaction assay indicated differential mRNA expression of ECE-1 isoforms. Using a luciferase reporter gene assay, we found that the genomic region upstream of exon 1 alpha confers strong promoter activity in the human endothelial cell line ECV 304, which was previously shown to express predominantly ECE-1 alpha mRNA. Transfection of serial deletion mutants in ECV304 cells indicated the existence of three positive and also one negative regulating element within 2 kb of the alpha-promoter region. Luciferase reporter gene studies also revealed that the genomic region upstream of exon 3, which encodes the putative ECE-1 beta specific N-terminus, was able to direct luciferase expression in primary cultured bovine aortic endothelial cells, indicating the existence of an alternative promoter. Transfection of nested deletions spanning 1.2 kb upstream of the putative translation initiation codon of ECE-1 beta suggested the existence of three positive regulating regions within the beta-specific promoter. Both ECE-1 promoters lack TATA or CAAT boxes, and the two show different patterns of consensus sequences for transcription factors, suggesting a differential transcriptional regulation of isoform-specific ECE-1 mRNA expression.

Aspartic Acid Endopeptidases↗
PubMed1997

[Endothelins in cardiovascular diseases].

Endothelins are peptides with powerful vasoconstrictor and mitogenic properties. It has become evident that endothelins are involved in many regulatory mechanisms of the circulation in which they have a modulating role both in short and in long term. However, in many cases it remains unclear whether the alteration of the endothelin metabolism is a primary pathology or a secondary phenomenon. The synthesis of endothelin receptor antagonists and animal models with altered endothelin metabolism have opened a new era of endothelin research that will allow insight into the mechanisms of endothelin-action and eventually might lead to new therapeutic concepts. This review discusses the evidence both in favor and against pathogenic effects of endothelins in cardiovascular disease.

Animals↗
PubMed1997

Vectors based on Semliki Forest virus for rapid and efficient gene transfer into non-endothelial cardiovascular cells: comparison to adenovirus.

OBJECTIVE: Replication-deficient, recombinant adenovirus is used as a carrier for gene transfer, but it is unspecific and the onset of transgene expression is relatively late. Here, we evaluated the efficiency and selectivity of gene transfer mediated by recombinant Semliki Forest virus (SFV). METHODS: We compared the efficiency of a SFV-based vector with an adenoviral vector, using LacZ as a reporter gene. Firstly, the affinity for vascular smooth muscle cells, endothelial cells and cardiac myocytes was assessed. Secondly, we compared the time course of LacZ expression and cytotoxicity in vascular smooth muscle cells. RESULTS: The SFV-based vector infects vascular smooth muscle cells and cardiomyocytes as efficiently as adenovirus. In contrast to adenovirus, SFV hardly transfers LacZ to endothelial cells (2.6% or less). SFV-mediated expression was visible after 1 h, reaching a maximum after 6 h. In contrast, adenovirus-mediated expression became visible after 6 h, and reached a maximum after 48-72 h. Both vectors were cytotoxic. CONCLUSIONS: We demonstrate that SFV efficiently transfers LacZ to vascular smooth muscle cells and cardiomyocytes, but not to endothelial cells. In contrast, adenovirus causes efficient transgene expression in all cell types tested. Furthermore, SFV-mediated expression is faster than adenovirus-mediated expression. Therefore, SFV-mediated gene transfer may be a suitable alternative to adenovirus, providing a fast expression in non-endothelial cardiovascular cell types.

Adenoviridae↗
PubMed1997

Activity of pentamidine-loaded methacrylate nanoparticles against Leishmania infantum in a mouse model.

The use of drug delivery systems may reduce the toxicity and improve the activity of antileishmanial compounds. In view of such a strategy, we loaded the antileishmanial agent pentamidine on polymethacrylate nanoparticles. The activity of pentamidine-loaded nanoparticles was compared with that of free pentamidine in a BALB/c mice model of visceral leishmaniasis induced by Leishmania infantum. On day 0, mice were infected intravenously with 10(7) promastigotes and then treated via the tail vein on days 14, 16 and 18 with bound pentamidine, free drug or isotonic saline (control group). On day 21, liver parasite burdens were evaluated using the Stauber method. Livers and spleens were removed and weighed. Effective doses (ED) were determined using the Michaelis-Menten representation relating the percentage of parasite suppression to the dose. The ED50 of bound pentamidine was six times lower than that of free pentamidine (0.17 mg kg-1 vs 1.06 mg kg-1). The ED90 value calculated for bound pentamidine was 1 mg kg-1. It was not possible to obtain the ED90 for free pentamidine because the dose-response curve reached a plateau near 60% of parasite suppression. A significant decrease in liver and spleen weights, probably reflecting the leishmanicidal activity, was observed for treated mice with bound pentamidine. These results showed that bound pentamidine was more potent than the free drug against L. infantum in our BALB/c mice model.

Animals↗
PubMed1997

Bergmann glial cells in situ express endothelinB receptors linked to cytoplasmic calcium signals.

The endothelin (ET) isoforms ET-1, ET-2 and ET-3 applied at 100 nM triggered a transient increase in [Ca2+]i in Bergmann glial cells in cerebellar slices acutely isolated from 20-25 day-old mice. The intracellular calcium concentration ([Ca2+]i) was monitored using Fura-2-based [Ca2+]i microfluorimetry. The ET-triggered [Ca2+]i transients were mimicked by ETB receptor agonist BQ-3020 and were inhibited by ETB receptor antagonist BQ-788. ET elevated [Ca2+]i in Ca(2+)-free extracellular solution and the ET-triggered [Ca2+]i elevation was blocked by 500 nM thapsigargin indicating that the [Ca2+]i was released from InsP3-sensitive intracellular pools. The ET-triggered [Ca2+]i increase in Ca(2+)-free solution was shorter in duration. Restoration of normal extracellular [Ca2+] briefly after the ET application induced a second [Ca2+]i increase indicating the presence of a secondary Ca2+ influx which prolongs the Ca2+ signal. Pre-application of 100 microM ATP or 10 microM noradrenaline blocked the ET response suggesting the involvement of a common Ca2+ depot. The expression of ETB receptor mRNAs in Bergmann glial cells was revealed by single-cell RT-PCR. The mRNA was also found in Purkinje neurones, but no Ca2+ signalling was triggered by ET. We conclude that Bergmann glial cells are endowed with functional ETB receptors which induce the generation of intracellular [Ca2+]i signals by activation of Ca2+ release from InsP3-sensitive intracellular stores followed by a secondary Ca2+ influx.

6-Cyano-7-nitroquinoxaline-2,3-dione↗
PubMed1997

Down-regulation of aortic and cardiac AT1 receptor gene expression in transgenic (mRen-2) 27 rats.

1. Transgenic(TG) (mRen-2) rats overexpressing the mouse renin gene develop fulminant hypertension and cardiac hypertrophy. Since the activation of AT1 receptor by angiotensin II is involved in blood pressure regulation, cardiac performance and myocardial growth, we investigated the biological effects of angiotensin II and the regulation of the AT1 receptor in the heart and aorta of TGR (mRen-2)27 rats in comparison to control animals. 2. Contraction studies on isolated cardiac muscle strips reveal that angiotensin II exerts no positive inotropic effect on the left ventricular myocardium of both, transgenic and control rats. In contrast, angiotensin II leads via AT1 receptor activation in the left atrium of control rats to a significant contraction (130 +/- 5% of basal contraction) which is not detectable in left atrium preparations of the transgenic animals. Furthermore, AT1 receptor activation causes a profound contraction of aortic rings isolated from control rats amounting to 1.39 +/- 0.2 mN mg-1 wet weight, whereas aortic rings from TGR (mRen-2)27 rats contract only minimally upon angiotensin II stimulation (0.2 +/- 0.02 mN mg-1 wet weight). 3. These altered physiological responses of angiotensin II in the transgenic rats are in part due to a marked down-regulation of the AT1 receptor in atrial, ventricular and aortic tissue of these transgenic animals in comparison to control Sprague-Dawley rats, as shown by radioligand binding assays and quantitative polymerase chain reaction (PCR) experiments. The AT1 receptor density Bmax in the left atrium was 1.3 +/- 0.08 fmol mg-1 protein in control rats (KD 1.1 +/- 0.18 nmol l-1) and 0.94 +/- 0.15 fmol mg-1 protein (KD 2.1 +/- 0.3 nmol l-1. In the aorta Bmax values were 15.1 +/- 0.5 fmol mg-1 protein (KD 1.9 +/- 0.27 nmol l-1) for control rats and 11.3 +/- 0.76 fmol mg-1 protein (KD 1.9 +/- 0.27 nmol l-1) for the TGR(mRen-2)27 rats AT1 receptor mRNA was reduced in the transgenic animals to 46 +/- 3% in the left atrium, 50 +/- 11% in the left ventricle and 40 +/- 3% in the aorta, respectively. 4. Together, the AT1 receptor is down-regulated in TGR (mRen-2)27 rats in comparison to wildtype Sprague Dawley rats leading to a profoundly decreased response of cardiac and aortic tissue upon stimulation with angiotensin II.

Analysis of Variance↗