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Biomedical subjects

M Paul

Publications and source records attributed to M Paul.

At least 235 records · Page 13Linked to original sources
PubMed1996

The cellular basis of angiotensin converting enzyme mRNA expression in rat heart.

Angiotensin converting enzyme (ACE) is a key factor in the regulation of two peptide systems: the renin angiotensin system (RAS) and the kinin-kallikrein system (KKS). Since it is involved in the biosynthesis of Angiotensin II (Ang II) as well as in the degradation of bradykinin (BK) it could play an important role in cardiovascular physiology and pathophysiology. ACE is widely expressed in the heart and upregulated in pathophysiological situations such as heart failure and cardiac hypertrophy. In addition, inhibition of ACE has beneficial effects in these conditions. Whereas the regulation of cardiac ACE has been studied extensively, little is known concerning the cellular expression of ACE in cardiac tissue. To define the cellular localization of ACE mRNA expression in the rat heart, we separated coronary microvascular endothelial cells from cardiac myocytes using differential centrifugation and growth on selective media. ACE mRNA expression was measured by a specific polymerase chain reaction assay after reverse transcription (RT-PCR) in different cardiac cells. The studies showed that ACE is differentially expressed in endothelial cells as well as in cardiac myocytes. This differential regulation of ACE in myocytes and non-myocytes may play a role for the diverse actions of the cardiac angiotensin system under physiological and pathological conditions.

Animals↗
PubMed1996

The hypertensive Ren-2 transgenic rat TGR (mREN2)27 in hypertension research. Characteristics and functional aspects.

Primary human hypertension is a polygenic disorder. It is the prevalent cause of cardiovascular disease leading to cardiac failure, stroke, chronic renal failure and, ultimately to death. Several genes are involved in cardiovascular control mechanisms and their genetics are complex. Experimental models which are well defined are needed to clarify the role of individual genes. The generation of the hypertensive transgenic rat line TGR (mREN2)27 bearing the murine Ren-2 gene cloned from the DBA/2J mouse strain provides a monogenic model of hypertension in which the genetic basis (the additional renin gene) is known. These rats develop severe hypertension, which reaches 200 mm Hg and higher at 8 weeks of age in the heterozygous animal. Homozygous rats develop even higher blood pressures than heterozygous animals, which is paralleled by a higher mortality rate in homozygous rats. Animals develop pathomorphologic alterations which are characteristic for systemic hypertension. The transgenic rats are characterized by unchanged or even suppressed concentrations of active renin, angiotensin I (ANG I), ANG II, and angiotensinogen compared to transgene-negative littermates. In contrast, plasma levels of inactive renin (prorenin) are much higher in TGR (mREN)27 rats than in control animals. In the kidneys, renin is suppressed, probably mediated through negative feedback inhibition, in other tissues, especially in the adrenal gland, murine Ren-2 mRNA is expressed at very high levels. The cascade of pathophysiologic events which finally lead to hypertension is not fully understood in this rat model. Treatment with ACE inhibitors or angiotensin II receptor antagonists such as losartan is extremely efficient, which could mean that hypertension in this model is mediated through ANG II. Since the the renin-angiotensin system (RAS) in the kidneys is suppressed, other ANG II generating sites must be considered. This favors the concept of extrarenal RASs in this model.

Animals↗
PubMed1996

The paradoxical effects of pentoxifylline on the binding of spermatozoa to the human zona pellucida.

In the presence of pentoxifylline, human spermatozoa are induced to increase certain motion characteristics; however, the role of this drug in fertilization remains equivocal. In this study, the influence of pentoxifylline on one aspect of fertilization, that is sperm-zona binding, has been examined. Results from a fluorescence label competitive zona binding (CZB) test showed that spermatozoa exposed to a pentoxifylline challenge of between 0.1 and 5 mM, which was curtailed after 1 h by washing, had a decreased (P < 0.01) ability to bind to intact zona compared with control spermatozoa. The washing procedures also removed (decrease P < 0.01 compared with peak values) some of the enhanced motion characteristics induced by pentoxifylline. These results were in contrast with those obtained using experimental conditions that maintained an increased curvilinear velocity (VCL) and lateral head displacement (ALH) (increase P < 0.001 above baseline controls) in the continued presence of pentoxifylline. Using a hemizona binding (HZB) assay, 3 mM pentoxifylline increased (P < 0.001) sperm-zona binding almost 20% above zona binding with unexposed control spermatozoa. It was concluded that, in the presence of pentoxifylline, there is increased sperm binding to the zona pellucida; however, if the drug is removed by washing, the sperm binding to the zona is decreased in concert with the removal of the enhanced motion characteristics. The application of zona solubilization by acidic conditions in a microchamber enabled the precise determination of sperm numbers in both of the sperm-zona binding assays, and the results demonstrated that a wide variation in sperm numbers was observed in each test, with 63-580 spermatozoa bound in the CZB assay and 56-1340 spermatozoa bound on a hemizona.

Female↗
PubMed1996

Factors affecting pentoxifylline stimulation of sperm kinematics in suspensions.

Sperm suspensions were prepared either by the 'swim-up' technique or by a Percoll gradient method before pentoxifylline was added to improve sperm motion characteristics. They were subsequently washed and then incubated with oocytes in in-vitro fertilization (IVF) programmes. The curvilinear velocity and lateral head displacement were approximately 20% higher in Percoll gradient-separated samples compared with samples prepared by the swim-up technique (P > 0.001), sperm motion characteristics being assessed by computer-assisted semen analysis. The dose-response study in which samples were separated by Percoll gradient/swim-up method showed that pentoxifylline gave maximum enhancement of sperm motion characteristics at a concentration of 2.8 mM/l, when the curvilinear velocity and lateral head displacement were significantly increased (P > 0.001). However, when pentoxifylline was removed by washing, the enhanced motion characteristics were reduced or lost in the process. Surprisingly, washing had a significant effect on the control samples, the motion characteristics being increased significantly (P > 0.001). This study casts doubt on the usefulness of pentoxifylline in IVF programmes.

Cell Separation↗
PubMed1996

Expression of inducible nitric oxide synthase in placenta of women with gestational diabetes.

Gestational diabetes is one of the most prevalent medical complications of pregnancy and causes increased fetal wastage. Investigation of placentas from diabetic mothers indicate chronic disturbances in intervillous, circulation, dilatation of capillaries, and a relatively immature villous structure. Abnormal levels of nitric oxide (NO) may contribute to maternal disorders such as the pathogenesis of diabetic vascular complications. In the normal placenta NO is generated only by endothelial NOS, which apparently serves to regulate vascular tone in the fetoplacental circulation. In contrast, studies have reported the absence of inducible nitric oxide synthase (iNOS) in human placentas under normal conditions. The aim of our study was to investigate whether iNOS is expressed in placentas from patients with gestational diabetes. Reverse transcription-polymerase chain reaction and Western blot analysis demonstrated iNOS mRNA and protein expression in placental tissue only from patients with gestational diabetes. Immunohistochemistry localized iNOS staining to endothelial cells and trophoblasts. We conclude that iNOS can be expressed in human placenta. Its expression might play an important role in placental pathophysiology.

Base Sequence↗
PubMed1996

Honeybee venom allergy: immunoblot studies in allergic patients after immunotherapy and before sting challenge.

By immunoblot techniques, detailed antibody studies were performed with sera of 20 honeybee-venom-allergic patients during or at the end of specific immunotherapy (median duration: 3 years) and before honeybee sting challenge. Before immunotherapy, all patients had experienced systemic allergic reactions to a honeybee sting, with a mean severity of 3.5 +/- 0.5 according to the Müller classification. After the sting challenge, 10 patients (reactors) reacted again with a systemic allergic reaction, whereas 10 patients (nonreactors) did not. No differences were observed between reactors and nonreactors in total serum IgE and specific IgE to honeybee venom at the time of challenge. For immunoblot, honeybee venom (RELESS) was separated on 7.5-20% SDS-PAGE. For detection of specific IgE, IgG, IgG1, IgG4, and IgM, an alkaline phosphatase-linked second antibody was used. Both groups showed 11 antibody-binding bands: at 52, 46, 40, 31, 18.7, 16.9, 13, 11, 10, 9, and 8 kDa; however, the antibody-binding pattern was individual. The reactors differed from nonreactors in showing intense IgE and less IgG4 binding to at least one single component of the venom extract. For nonreactors, the inverse relationship was observed. The hypothesis, "intensity of IgE > or = IgG4 leads to allergic symptoms", was highly significant (P = 0.00026; chi-square). These immunoblot findings could offer predictive value in distinguishing reactors from nonreactors.

Adolescent↗
PubMed1996

Patch testing in severe cutaneous adverse drug reactions, including Stevens-Johnson syndrome and toxic epidermal necrolysis.

Patch testing may help to assess the culpability of a drug in an adverse reaction. Our aim was to study patch testing in severe cutaneous adverse drug reactions (ADRs) (Stevens-Johnson syndrome/toxic epidermal necrolysis (SJS/TEN), acute generalized exanthematous pustulosis (AGEP), and other cutaneous ADRs). 59 patients with cutaneous ADRs were included: 22 had SJS/TEN, 14 AGEP, and 23 other cutaneous ADRs. Patients were patch tested with the suspect drug, and with a standard series of drugs. 2 patients among the 22 SJS/TEN cases had a relevant positive test. 7 patients among the 14 AGEP cases had a relevant positive test. 6 patients among the 23 other cutaneous ADRs had a relevant positive test. Our results suggest that patch testing has a weak sensitivity in SJS/TEN and is not appropriate in these diseases. Patch testing seems more adapted to other cutaneous ADRs, such as AGEP, in which the proportion of positive patch tests was significantly higher (p < 0.02). Nevertheless, the difference of sensitivity of patch testing in SJS/ TEN, AGEP or other cutaneous ADRs could be linked not only to the clinical type of eruption, but also to the different spectrum of culprit drugs in each type of eruption.

Adult↗
PubMed1996

Type 1 and type 2 cytokine profiles in children exposed to or infected with vertically transmitted human immunodeficiency virus.

In human immunodeficiency virus (HIV)-infected adults, cytokine production profiles switch from predominantly type 1 (interleukin-2 [IL-2] and gamma interferon [IFN-gamma]) to type 2 (IL-4 and IL-10) cytokines with disease progression. To test this hypothesis in vertically HIV-infected children, we measured cytokine transcription and production in rapid progressors (RPs), seroreverters (SRs), and those children exposed to HIV in utero (P0s). Production of type 1 and type 2 cytokines was measured in peripheral blood mononuclear cell cultures of 8 SR, 25 P0, and 11 RP children. Unstimulated cultures, irrespective of infection and stage of disease, produced similar levels of IL-2, IFN-gamma, IL-4, and IL-10. Upon stimulation with phytohemagglutinin (PHA) plus phorbol-12-myristate-13-acetate (PMA), RP children produced less IL-2 (P < 0.01) and IFN-gamma (P < 0.02) than SR children and also expressed significantly less IFN-gamma mRNA (P < 0.01) than SR children. RP children expressed significantly higher levels of IL-4 mRNA than P0 children (P < 0.03). There were no differences in the production of IL-10 by PHA-PMA-stimulated peripheral blood mononuclear cell cultures among the three groups of children. Our data with these pediatric patients suggest that a deficiency in mitogen-stimulated type 1 cytokine production and excess type 2 cytokine (IL-4) transcription correlate with disease progression. Additional studies with larger sample sizes are needed to test further the hypothesis of the type 1-to-type 2 cytokine switch in children infected with HIV.

Cells, Cultured↗
PubMed1996

Demonstration of renin mRNA, angiotensinogen mRNA, and angiotensin converting enzyme mRNA expression in the human eye: evidence for an intraocular renin-angiotensin system.

AIMS/BACKGROUND: All components necessary for the formation of angiotensin II, the biologically active product of the renin-angiotensin system (RAS), have been demonstrated in ocular tissue or vitreous and subretinal fluid. The tissue concentrations of renin were too high to be explained by admixture of blood. This raises the possibility of an intraocular RAS, independent of the RAS in the circulation. METHODS: In the present study, gene expression of RAS components in different parts of enucleated human eyes was investigated as evidence for tissue specific production. RESULTS: By using pooled tissue samples renin mRNA could be detected with the RNAse protection assay in retinal pigment epithelium (RPE) choroid, but not in neural retina or sclera. With reverse transcription polymerase chain reaction (RT-PCR), renin mRNA was detected in individual samples of RPE choroid and neural retina, and not anterior uveal tract or sclera. Angiotensinogen and angiotensin converting enzyme (ACE) gene expression could be demonstrated by RT-PCR in individual RPE choroid and neural retina samples and marginally in sclera samples. CONCLUSIONS: These results support the concept of intraocular synthesis of angiotensin II, independent of renin, angiotensin, and ACE in the circulation. Since gene expression was highest in ocular parts, which are highly vascularised, local angiotensin II may be involved in blood supply and/or pathological vascular processes such as neovascularisation in diabetic retinopathy.

Adult↗
PubMed1996

Physiological characterization of the hypertensive transgenic rat TGR(mREN2)27.

Transgenic techniques represent powerful tools for the study of gene-related mechanisms of diseases such as hypertension, which results from a complex interaction between genetic and environmental factors. The renin-angiotensin system, a biochemical cascade in which renin functions as the key enzyme in the formation of the effector peptide angiotensin II, plays a major role in the regulation of blood pressure. The renin gene, therefore, represents an important candidate gene for hypertension. Because rats are more suited than mice for a number of experimental settings often employed in cardiovascular research, we modified the transgenic technique to generate the transgenic rat strain TGR(mREN2)27 harboring the murine Ren-2 gene. These transgenic rats develop fulminant hypertension at an early age despite low levels of renin in plasma and kidney. In addition, high expression of the transgene in a number of extrarenal tissues is associated with increased local formation of angiotensin II. Thus the TGR(mREN2)27 rat represents a model of hypertension with a defined genetic background. Studies on the transgenic rat may not only provide new insights into pathophysiological mechanisms of hypertension in this animal model but also offer the unique possibility to investigate the function and regulation of renin-angiotensin systems in extrarenal tissues. The aim of this review is to compile the knowledge that has been accumulated to date on this transgenic rat and to discuss possible mechanisms responsible for its hypertensive phenotype.

Animals↗
PubMed1996

Pulmonary clearance and lung function: influence of acute tobacco intoxication and of vitamin E.

Cigarette smoking increases the alveolar epithelial permeability to small solutes, as assessed by the pulmonary clearance of aerosolized 99mTc-labeled diethylenetriaminepentaacetate. The involvement of lipid peroxidation in this increased clearance was tested in eight asymptomatic young smokers by investigating the effects of a 3-wk supplementation with oral vitamin E (1,000 IU/day) on pulmonary clearance according to a protocol designed as a single-blind crossover study. Indexes of acute tobacco intoxication (exhaled CO, carboxyhemoglobin, and urinary cotinine) and lung function parameters [including Krogh factor (KCO)] were also studied. Under control conditions, pulmonary clearance was abnormally increased (2.93 +/- 0.78%/min), whereas KCO was in the normal range. Pulmonary clearance correlated strongly with expired CO (P < 0.04), HbCO (P < 0.005), urinary cotinine (P < 0.003), and KCO (P < 0.004). Supplementation with vitamin E, a highly efficient antioxidant, neither decreased the pulmonary clearance nor altered the above correlations. However, the strong correlations observed between pulmonary clearance and indexes of acute tobacco intoxication, which reflect the amount of inhaled smoke and the resultant oxidant stress, do not allow exclusion of the involvement of lipid peroxidation in the pulmonary clearance increase observed in smokers.

Adult↗
PubMed1996

Characterization of the renal phenotype of transgenic rats expressing the human endothelin-2 gene.

We have previously established a transgenic rat model termed TGR(hET-2)37 overexpressing the human endothelin-2 (ET-2) gene with high renal transgene expression. This renal overexpression is of pathophysiological interest because a long-term activated paracrine renal endothelin system has been implicated in chronic renal failure due to progressive glomerular injury. Therefore, our aim in the present study was to analyze renal transgene expression in detail and address the question of whether transgene expression causes phenotypic and functional changes in the kidney. We used reverse transcription-polymerase chain reaction and in situ hybridization techniques for transgene expression analysis. Tissue ET-2 concentrations were measured with a specific radioimmunoassay. For histological evaluation of renal tissue, all samples were subjected to hematoxylin-eosin and periodic acid-Schiff staining. Renal tissue ET-2 concentrations were significantly increased in TGR(hET-2)37 rats. Using in situ hybridization, we found that the human ET-2 gene was almost exclusively expressed within the glomeruli. The glomerular transgene expression resulted in a significantly increased glomerular injury score and likewise in a significantly increased protein excretion, whereas glomerular filtration rate was not altered. Blood pressure was similar in TGR(hET-2)37 rats and age-matched controls, suggesting that the local changes in the kidney were correlated with paracrine endothelin actions. In conclusion, our study revealed that the major renal expression site of the human ET-2 transgene in TGR(hET-2)37 rats was within the glomeruli and caused the development of glomerulo-sclerosis with significantly increased protein excretion that is independent of blood pressure. We suggest that TGR(hET-2)37 rats are a new monogenetic animal model for study of the paracrine renal endothelin system and its involvement in renal pathophysiology.

Animals↗
PubMed1996

Effect of losartan on right ventricular hypertrophy and cardiac angiotensin I-converting enzyme activity in pulmonary hypertensive rats.

The aim of this study was to investigate the effect of prophylactic treatment with the angiotensin type 1 (AT1) receptor antagonist losartan on right ventricular hypertrophy and cardiac angiotensin 1-converting enzyme (ACE) activity in a rat model of monocrotaline-induced pulmonary hypertension. Losartan failed to prevent either pulmonary hypertension or right ventricular hypertrophy. Right ventricular ACE in untreated pulmonary hypertensive rats did not differ from control rats. Losartan treatment in pulmonary hypertensive rats caused a significant 2-fold increase of ACE activity in the hypertrophied right (p < 0.005) but not in the left ventricle. Thus, cardiac ACE activity is not stimulated in rats with monocrotaline-induced right ventricular hypertrophy. Prophylactic losartan treatment in this model of progressive pulmonary hypertension failed to prevent or reduce the increase in ventricular afterload. The relevance of the increase in right ventricular ACE activity during pulmonary hypertension after losartan treatment is unknown and needs to be evaluated in further studies.

Animals↗
PubMed1996

Severe and complicated falciparum malaria in Melanesian adults in Papua New Guinea.

Severe falciparum malaria usually occurs in children, but also occurs in nonimmune migrants or partially immune adults in areas of unstable transmission. We have studied prospectively 70 adult patients with strictly defined severe malaria from the south coast of Papua New Guinea where malaria transmission is not intense. Only 19 (27.1%) were migrants from areas where malaria transmission does not occur; many other patients were periurban dwellers who had become infected after visits to their home villages. The most common clinical features were jaundice or hepatic dysfunction, impaired consciousness, renal failure, cerebral malaria, and anemia. Hypoglycemia was common following treatment with quinine. The overall case fatality rate was 18.6%; renal failure and cerebral malaria in particular were associated with a poor outcome. Reduction in mortality might be achieved by aggressive therapy of renal failure with earlier institution of dialysis; the use of preventive measures for immigrants or urban dwellers returning to high transmission areas might reduce the incidence of this dangerous disease.

Adolescent↗