Biomedical subjects

B Mayer

Publications and source records attributed to B Mayer.

At least 19 recordsLinked to original sources

PubMed2026

Beyond in silico prediction: multi-omics to identify a pathogenic deep intronic HNRNPK variant in Au-Kline syndrome.

Pathogenic variants in HNRNPK are associated with autosomal dominant Au-Kline syndrome (AKS, Au-Kline-Okamoto syndrome, OMIM #616580). This syndrome is characterized by developmental delay and intellectual disability, hypotonia, and distinctive facial features. Despite the use of whole-genome sequencing (WGS) as a powerful diagnostic tool, we nearly dismissed a novel intronic variant (NM_031263.4(HNRNPK):c.214-55 T > A) affecting HNRNPK splicing and function. Although commonly used bioinformatic splice prediction tools, including SpliceAI and PDIVAS, yielded inconclusive results, Face2Gene analysis indicated a high phenotypic similarity to AKS. Characteristic facial features described by Choufani et al. [1] supported the clinical diagnosis of AKS. Subsequent functional studies demonstrated aberrant splicing with intron retention, and DNA methylation profiling revealed a positive HNRNPK-specific episignature. These insights and the de novo status support an evaluation as likely pathogenic. This case report supports the relevance of facial analysis and comprehensive variant validation strategies, particularly for deep intronic variants with ambiguous in silico splicing predictions.

Journal Article↗

PubMed2001

Protein tyrosine nitration in cytokine-activated murine macrophages. Involvement of a peroxidase/nitrite pathway rather than peroxynitrite.

Peroxynitrite, formed in a rapid reaction of nitric oxide (NO) and superoxide anion radical (O(2)), is thought to mediate protein tyrosine nitration in various inflammatory and infectious diseases. However, a recent in vitro study indicated that peroxynitrite exhibits poor nitrating efficiency at biologically relevant steady-state concentrations (Pfeiffer, S., Schmidt, K., and Mayer, B. (2000) J. Biol. Chem. 275, 6346-6352). To investigate the molecular mechanism of protein tyrosine nitration in intact cells, murine RAW 264.7 macrophages were activated with immunological stimuli, causing inducible NO synthase expression (interferon-gamma in combination with either lipopolysaccharide or zymosan A), followed by the determination of protein-bound 3-nitrotyrosine levels and release of potential triggers of nitration (NO, O(2)*, H(2)O(2), peroxynitrite, and nitrite). Levels of 3-nitrotyrosine started to increase at 16-18 h and exhibited a maximum at 20-24 h post-stimulation. Formation of O(2) was maximal at 1-5 h and decreased to base line 5 h after stimulation. Release of NO peaked at approximately 6 and approximately 9 h after stimulation with interferon-gamma/lipopolysaccharide and interferon-gamma/zymosan A, respectively, followed by a rapid decline to base line within the next 4 h. NO formation resulted in accumulation of nitrite, which leveled off at about 50 microm 15 h post-stimulation. Significant release of peroxynitrite was detectable only upon treatment of cytokine-activated cells with phorbol 12-myristate-13-acetate, which led to a 2.2-fold increase in dihydrorhodamine oxidation without significantly increasing the levels of 3-nitrotyrosine. Tyrosine nitration was inhibited by azide and catalase and mimicked by incubation of unstimulated cells with nitrite. Together with the striking discrepancy in the time course of NO/O(2) release versus 3-nitrotyrosine formation, these results suggest that protein tyrosine nitration in activated macrophages is caused by a nitrite-dependent peroxidase reaction rather than peroxynitrite.

Animals↗

PubMed2001

Co-conformational variability of cyclodextrin complexes studied by induced circular dichroism of azoalkanes.

The solution structures of the beta-cyclodextrin complexes between 2,3-diazabicyclo[2.2.2]oct-2-ene (1) and its 1-isopropyl-4-methyl derivative 2 have been investigated by means of induced circular dichroism (ICD) and MM3-92 force-field calculations, which considered the effect of solvation within a continuum approximation. Of primary interest was the so-called co-conformation of the host-guest complex, i.e., the relative orientation of the guest within the host. A pool of low-energy complex structures, which were located by means of a Monte Carlo simulated annealing routine, was generated to evaluate the dynamic co-conformational variability of the complexes. The ICD effects were calculated for the computed low-energy structures by applying a semiempirical method. The experimental and theoretical ICD as well as the calculated low-energy complex geometries suggest solution co-conformations in which the parent compound 1 adapts a lateral arrangement with the ethano bridge of the guest penetrating deepest into the cavity and the azo group aligning parallel to the plane of the upper rim. In contrast, the alkyl derivative 2 prefers a frontal co-conformation with the isopropyl group penetrating deepest into the cavity and the azo group aligning perpendicular to the plane of the upper rim. The validity of the predictions of the Harata rule regarding the sign and the intensity of the ICD signals for the n(-)pi, n(+)pi, and pipi transition of the azo chromophore in dependence on the complex co-conformation are discussed. With respect to the co-conformational variability of the complexes of the two azoalkanes, it was observed that the nearly spherical guest 1 forms a geometrically better defined complex than the sterically biased, alkyl-substituted derivative 2. This dichotomy is attributed to the largely different modes of binding for azoalkanes 1 and 2. It is concluded that the goodness-of-fit in a host-guest complex cannot be directly related to the "tightness-of-fit".

Journal Article↗

PubMed2001

Suramin and the suramin analogue NF307 discriminate among calmodulin-binding sites.

Calmodulin-binding sites on target proteins show considerable variation in primary sequence; hence compounds that block the access of calmodulin to these binding sites may be more selective than compounds that inactivate calmodulin. Suramin and its analogue NF307 inhibit the interaction of calmodulin with the ryanodine receptor. We have investigated whether inhibition of calmodulin binding to target proteins is a general property of these compounds. Suramin inhibited binding of [(125)I]calmodulin to porcine brain membranes and to sarcoplasmic reticulum from skeletal muscle (IC(50)=4.9+/-1.2 microM and 19.9+/-1.8 microM, respectively) and blocked the cross-linking of [(125)I]calmodulin to some, but not all, target proteins in brain membranes by [(125)I]calmodulin. Four calmodulin-binding proteins were purified [ryanodine receptor-1 (RyR1) from rabbit skeletal muscle, neuronal NO synthase (nNOS) from Sf9 cells, G-protein betagamma dimers (Gbetagamma) from porcine brain and a glutathione S-transferase-fusion protein comprising the C-terminal calmodulin-binding domain of the metabotropic glutamate receptor 7A (GST-CmGluR7A) from bacterial lysates]. Three of the proteins employed (Gbetagamma, GST-CmGluR7A and RyR1) display a comparable affinity for calmodulin (in the range of 50-70 nM). Nevertheless, suramin and NF307 only blocked the binding of Gbetagamma and RyR1 to calmodulin-Sepharose. In contrast, the association of GST-CmGluR7A and nNOS was not impaired, whereas excess calmodulin uniformly displaced all proteins from the matrix. Thus suramin and NF307 are prototypes of a new class of calmodulin antagonists that do not interact directly with calmodulin but with calmodulin-recognition sites. In addition, these compounds discriminate among calmodulin-binding motifs.

Allosteric Regulation↗

PubMed2001

S-nitrosation controls gating and conductance of the alpha 1 subunit of class C L-type Ca(2+) channels.

Modulation of smooth muscle, L-type Ca(2+) channels (class C, Ca(V)1.2b) by thionitrite S-nitrosoglutathione (GSNO) was investigated in the human embryonic kidney 293 expression system at the level of whole-cell and single-channel currents. Extracellular administration of GSNO (2 mM) rapidly reduced whole-cell Ba(2+) currents through channels derived either by expression of alpha1C-b or by coexpression of alpha1C-b plus beta2a and alpha2-delta. The non-thiol nitric oxide (NO) donors 2,2-diethyl-1-nitroso-oxhydrazin (2 mM) and 3-morpholinosydnonimine-hydrochloride (2 mM), which elevated cellular cGMP levels to a similar extent as GSNO, failed to affect Ba(2+) currents significantly. Intracellular administration of copper ions, which promote decomposition of the thionitrite, antagonized its inhibitory effect, and loading of cells with high concentrations of dithiothreitol (2 mM) prevented the effect of GSNO on alpha1C-b channels. Intracellular loading of cells with oxidized glutathione (2 mM) affected neither alpha1C-b channel function nor their modulation by GSNO. Analysis of single-channel behavior revealed that GSNO inhibited Ca(2+) channels mainly by reducing open probability. The development of GSNO-induced inhibition was associated with the transient occurrence of a reduced conductance state of the channel. Our results demonstrate that GSNO modulates the alpha1 subunit of smooth muscle L-type Ca(2+) channels by an intracellular mechanism that is independent of NO release and stimulation of guanylyl cyclase. We suggest S-nitrosation of intracellularly located sulfhydryl groups as an important determinant of Ca(2+) channel gating and conductance.

Calcium Channel Blockers↗

PubMed2001

L-ascorbic acid potentiates endothelial nitric oxide synthesis via a chemical stabilization of tetrahydrobiopterin.

Ascorbic acid has been shown to stimulate endothelial nitric oxide (NO) synthesis in a time- and concentration-dependent fashion without affecting NO synthase (NOS) expression or l-arginine uptake. The present study investigates if the underlying mechanism is related to the NOS cofactor tetrahydrobiopterin. Pretreatment of human umbilical vein endothelial cells with ascorbate (1 microm to 1 mm, 24 h) led to an up to 3-fold increase of intracellular tetrahydrobiopterin levels that was concentration-dependent and saturable at 100 microm. Accordingly, the effect of ascorbic acid on Ca(2+)-dependent formation of citrulline (co-product of NO) and cGMP (product of the NO-activated soluble guanylate cyclase) was abolished when intracellular tetrahydrobiopterin levels were increased by coincubation of endothelial cells with sepiapterin (0.001-100 microm, 24 h). In contrast, ascorbic acid did not modify the pterin affinity of endothelial NOS, which was measured in assays with purified tetrahydrobiopterin-free enzyme. The ascorbate-induced increase of endothelial tetrahydrobiopterin was not due to an enhanced synthesis of the compound. Neither the mRNA expression of the rate-limiting enzyme in tetrahydrobiopterin biosynthesis, GTP cyclohydrolase I, nor the activities of either GTP cyclohydrolase I or 6-pyruvoyl-tetrahydropterin synthase, the second enzyme in the de novo synthesis pathway, were altered by ascorbate. Our data demonstrate that ascorbic acid leads to a chemical stabilization of tetrahydrobiopterin. This was evident as an increase in the half-life of tetrahydrobiopterin in aqueous solution. Furthermore, the increase of tetrahydrobiopterin levels in intact endothelial cells coincubated with cytokines and ascorbate was associated with a decrease of more oxidized biopterin derivatives (7,8-dihydrobiopterin and biopterin) in cells and cell supernatants. The present study suggests that saturated ascorbic acid levels in endothelial cells are necessary to protect tetrahydrobiopterin from oxidation and to provide optimal conditions for cellular NO synthesis.

Ascorbic Acid↗

PubMed2001

Electrochemistry of pterin cofactors and inhibitors of nitric oxide synthase.

Tetrahydrobiopterin (BH4) is an essential cofactor of nitric oxide synthase (NOS), but its function is not fully understood. Specifically, it is unclear whether BH4 participates directly in electron transfer. We investigated the redox properties of BH4 and several other pteridines with cyclic voltammetry and Osteryoung square wave voltammetry. BH4 was oxidized at a potential of +0.27 V vs normal hydrogen electrode (NHE); the corresponding reductive signal after the reversal of the scan direction was very small. Instead, reduction occurred at a potential of -0.16 V vs NHE; there was no corresponding oxidative signal. These two transitions were interdependent, indicating that the reductive wave at -0.16 V represented the regeneration of BH4 from its product of oxidation at +0.27 V. Similar voltammograms were obtained with tetrahydroneopterin and 6,7-dimethyltetrahydropterin, both of which can substitute for BH4 in NOS catalysis. Completely different voltammograms were obtained with 7,8-dihydrobiopterin, sepiapterin, 2'-deoxysepiapterin, and autoxidized BH4. These 7,8-dihydropterins, which do not sustain NOS catalysis, were oxidized at much higher potentials (+0.82-1.04 V vs NHE), and appreciable reduction did not occur between +1.2 and -0.8 V, in line with the concept of a redox role for BH4 in NOS catalysis. However, the electrochemical properties of the potent pterin-site NOS inhibitor 4-amino-BH4 resembled those of BH4, whereas the active pterin cofactor 5-methyl-BH4 was not re-reduced after oxidation. We conclude that the 2-electron redox cycling of the pterin cofactor between BH4 and quinonoid dihydrobiopterin is not essential for NO synthesis. The data are consistent with 1-electron redox cycling between BH4 and the trihydrobiopterin radical BH3(*).

Antioxidants↗

PubMed2001

[ACE inhibition in patients with myocardial infarct and ventricular dysfunction: inappropriate application of therapy standards in patient samples].

Several reports indicate the benefit of ACE inhibitors for patients with left ventricular systolic dysfunction after acute myocardial infarction (MI). We sought to determine the implementation of the treatment guidelines in patient samples from the general population. Furthermore we aimed to identify patient characteristics associated with the use of ACE inhibitors. Screening of two MI-registries allowed the identification of 226 MI patients with left ventricular dysfunction. Patients were considered to be eligible for ACE inhibitor therapy when a EF < or = 40% was documented in the patient records of cardiac rehabilitation clinics (REG-MI, n = 147) or detected by standardised echocardiography (KORA, n = 78). On average 5.5 years following MI, a standardised questionnaire and a detailed medical history was obtained. Specifically, information was collected regarding current medication and potential contraindications for ACE inhibitors. MI patients with LV dysfunction received ACE inhibitors in 62% (REG-MI) and 45% (KORA). The doses prescribed were substantially smaller than target doses used in the large-scale studies (REG-MI: 40 +/- 4%, KORA: 23 +/- 3%, % of target doses). Only 13% (REG-MI) and 3% (KORA) received more than 50% of the target dosage. Additionally, actual doses of the most frequently used ACE inhibitors were significantly different (captopril: 23 +/- 2%, enalapril: 42 +/- 5% of target doses). The likelihood of receiving ACE inhibitors was significantly higher in patients with written recommendation for such medication (odds ratio 6.02, confidence interval 1.93-20.16) and in patients visiting cardiologists (odds ratio 3.69, confidence interval 1.26-11.07) as revealed by multivariate analysis of the REG-MI database. Despite national and international guidance, a large proportion of MI patients with left ventricular dysfunction is not receiving ACE inhibitors, and when used, the doses prescribed are markedly smaller than target doses used in clinical trials that established the utility of these drugs. Medical care by cardiologists and written recommendation of ACE inhibition in patient records were independent predictors of a more appropriate prescription of ACE inhibitors.

Aged↗

PubMed2001

Formation of a protonated trihydrobiopterin radical cation in the first reaction cycle of neuronal and endothelial nitric oxide synthase detected by electron paramagnetic resonance spectroscopy.

Nitric oxide synthase (EC 1.14.13.39; NOS) converts L-arginine into NO and L-citrulline in a two-step reaction with Nomega-hydroxy-L-arginine (NOHLA) as an intermediate. The active site iron in NOS has thiolate axial heme-iron ligation as found in the related monooxygenase cytochrome P450. In NOS, tetrahydrobiopterin (BH4) is an essential cofactor for both steps, but its function is controversial. Previous optical studies of the reaction between reduced NOS with O2 at -30 degrees C suggested that BH4 may serve as an one-electron donor in the first cycle, implying formation of a trihydrobiopterin radical. We investigated the same reaction under identical conditions with electron paramagnetic resonance spectroscopy. With BH4-containing full-length neuronal NOS we obtained an organic free radical (g-value 2.0042) in the presence of Arg, and a similar radical was observed with the endothelial NOS oxygenase domain in the presence of Arg and BH4. Without substrate the radical yield was greatly (10x) diminished. Without BH4, or with NOHLA instead of Arg, no radical was observed. With 6-methyltetrahydropterin or 5-methyl-BH4 instead of BH4, radicals with somewhat different spectra were formed. On the basis of simulations we assign the signals to trihydropterin radical cations protonated at N5. This is the first study that demonstrates the formation of a protonated trihydrobiopterin radical with the constitutive isoforms of NOS, and the first time the radical was obtained without exogenous BH4. These results offer strong support for redox cycling of BH4 in the first reaction cycle of NOS catalysis (BH4 <--> BH3.H+).

Animals↗

PubMed2001

Association between a polymorphism in the G protein beta3 subunit gene (GNB3) with arterial hypertension but not with myocardial infarction.

OBJECTIVE: A polymorphism at position 825(C-->T) of the G protein beta3 (GNB3) gene was found to be associated with enhanced transmembrane signalling as well as with an increased prevalence of arterial hypertension. The aim of the present study was to further investigate the association of the GNB3 C825T allele status with arterial hypertension in a large population-based sample and its association with specific end organ damage, i.e. myocardial infarction (MI). METHODS: Individuals from a population-based sample (n=2052) and patients suffering from premature MI (age at first MI < or = 60 years, n = 606) were studied by questionnaire as well as by physical examination and biochemical analyses. RESULTS: In the population-based sample, the prevalence of arterial hypertension (blood pressure > or = 160/95 mmHg and/or antihypertensive medication) was higher in individuals with the TT genotype (41.8%) as compared to heterozygote individuals (36.6%) or those with the CC genotype (32.75%) (P = 0.02). This association was predominantly found in men. Moreover, men without antihypertensive medication carrying the TT genotype showed higher diastolic blood pressure than those carrying the CC genotype (86.5 vs. 83.7 mmHg, P = 0.04). However, the genotype distribution and the allele frequencies were similar in both, the population-based and the MI patient sample. Furthermore, neither the age at the time of MI nor the location of the MI were related to the genotype distribution. Similarly, gender and age stratified analyses did not show any association of the GNB3 genotype and MI. CONCLUSIONS: In male individuals from a large population-based sample, the T allele of the GNB3 polymorphism was associated with arterial hypertension. However, the effects of the GNB3 825T allele on blood pressure were small and did not translate to a clinically relevant increase of risk for MI.

Antihypertensive Agents↗

PubMed2001

Nitric oxide synthase-I containing cortical interneurons co-express antioxidative enzymes and anti-apoptotic Bcl-2 following focal ischemia: evidence for direct and indirect mechanisms towards their resistance to neuropathology.

Neuronal nitric oxide-I is constitutively expressed in approximately 2% of cortical interneurons and is co-localized with gamma-amino butric acid, somatostatin or neuropeptide Y. These interneurons additionally express high amounts of glutamate receptors which mediate the glutamate-induced hyperexcitation following cerebral injury, under these conditions nitric oxide production increases contributing to a potentiation of oxidative stress. However, perilesional nitric oxide synthase-I containing neurons are known to be resistant to ischemic and excitotoxic injury. In vitro studies show that nitrosonium and nitroxyl ions inactivate N-methyl-D-aspartate receptors, resulting in neuroprotection. The question remains of how these cells are protected against their own high intracellular nitric oxide production after activation. In this study, we investigated immunocytochemically nitric oxide synthase-I containing cortical neurons in rats after unilateral, cortical photothrombosis. In this model of focal ischemia, perilesional, constitutively nitric oxide synthase-I containing neurons survived and co-expressed antioxidative enzymes, such as manganese- and copper-zinc-dependent superoxide dismutases, heme oxygenase-2 and cytosolic glutathione peroxidase. This enhanced antioxidant expression was accompanied by a strong perinuclear presence of the antiapoptotic Bcl-2 protein. No colocalization was detectable with upregulated heme oxygenase-1 in glia and the superoxide and prostaglandin G(2)-producing cyclooxygenase-2 in neurons. These results suggest that nitric oxide synthase-I containing interneurons are protected against intracellular oxidative damage and apoptosis by Bcl-2 and several potent antioxidative enzymes. Since nitric oxide synthase-I positive neurons do not express superoxide-producing enzymes such as cyclooxygenase-1, xanthine oxidase and cyclooxygenase-2 in response to injury, this may additionally contribute to their resistance by reducing their internal peroxynitrite, H(2)O(2)-formation and caspase activation.

Animals↗

PubMed2001

The alpha-amino group of L-arginine mediates its antioxidant effect.

Antioxidant effects may constitute part of the possible antiatherogenic effects of the amino acid L-arginine. These antioxidant properties were further characterized in a model of lipoprotein oxidation. Oxidation of lipoproteins in unfractionated human serum was continuously monitored by a fluorescent probe. The antioxidant effects of L-arginine, N-alpha-acetyl-arginine and vitamin E in combination with L-arginine were measured after initiation of free radical generation with either copper or 2,2'-azobis(2-amidinopropane) hydrochloride (AAPH). The half-time of the fast propagation rate for copper-induced lipoprotein oxidation increased after incubation with L-arginine in a dose-dependent manner (P < 0.01). N-alpha-acetyl-arginine did not show such effects. Vitamin E and L-arginine show different effects on copper-induced oxidation, the former increasing only lag-time, the latter increasing only propagation rate, and do not have reciprocal effects. In contrast to copper-induced oxidation, L-arginine increased the lag-time of AAPH-induced lipoprotein oxidation (P < 0.01), with no effect on the propagation rate at physiological concentrations. Again, N-alpha-acetyl-arginine did not show any antioxidant effects. Our experiments provide further evidence that mechanisms other than serving as a substrate for the NO-synthase could be involved in the antiatherosclerotic effect of L-arginine. In addition, our experiments clearly show, that the antioxidant effect of L-arginine is due to a chemical moiety different from that serving as the substrate for NO biosynthesis.

Amidines↗

PubMed2001

Marked suppression of renin levels by beta-receptor blocker in patients treated with standard heart failure therapy: a potential mechanism of benefit from beta-blockade.

OBJECTIVES: Recent trials demonstrated beneficial effects of beta-blockers in combination with standard heart failure medication. The mechanisms underlying this benefit are incompletely understood. We hypothesized that beta-blockers may augment the inhibition of the renin-angiotensin system in patients with left ventricular (LV) dysfunction treated with angiotensin-converting enzyme (ACE) inhibitors and/or diuretics by prevention of renin upregulation that occurs in such patients. DESIGN: We examined plasma renin levels (direct radioimmunometric assay) in 312 men with previous myocardial infarction (MI) and echocardiographic LV dysfunction. Patients took medication according to their physicians' prescriptions: antiplatelet agents alone (n=62) or in combination with ACE inhibitors, diuretics or beta-blockers (n=250). RESULTS: Plasma renin levels were elevated in patients taking ACE inhibitors or diuretics and ACE inhibitors plus diuretics (adjusted means from multiple regression analysis were 28.5 mU L-1 [95% CI=20.6-39.5] and 73.7 mU L-1 [95% CI = 49.9- 109.9], respectively) compared with patients on antiplatelets alone (16.1 mU L-1, 95% CI = 13.5-19.3, P < 0.05 each). The combinations of beta-blockers with ACE inhibitors or diuretics and beta-blockers with ACE inhibitors plus diuretics were related to markedly suppressed plasma renin levels (adjusted means 16.4 [13.1-20.6] and 32.1 [23.3-44.3]) as compared with respective patient groups without beta-blockers (P < 0.01 each). CONCLUSIONS: Concomitant beta-blocker treatment can prevent the reactive renin stimulation and potentially the escape from effective inhibition of the renin-angiotensin system in patients with LV dysfunction after MI treated with ACE-inhibitors and/or diuretics.

Adrenergic beta-Antagonists↗

PubMed2001

Siblings of myocardial infarction patients are overlooked in primary prevention of cardiovascular disease.

AIMS: Patients with arterial hypertension or hypercholesterolaemia may benefit from medical therapy for primary prevention of myocardial infarction. Preventive therapy may be particularly effective in individuals with a positive family history for myocardial infarction since such subjects are at high risk for coronary events. The objective of this population-based study was to analyse the risk profile as well as the current utilization of preventive strategies in asymptomatic siblings of patients with myocardial infarction. METHODS AND RESULTS: We studied siblings of 325 patients with premature myocardial infarction from the Augsburg MONICA myocardial infarction registry by standardized questionnaire, blood pressure recordings, and biochemical measurements. Out of 580 siblings, 510 were free of coronary heart disease symptoms. With multiple risk factors being present in most asymptomatic siblings, 29.4% of asymptomatic individuals had an estimated individual 10-year risk for a major cardiovascular event of > or = 20%, or when projected to the age of 60. According to the guidelines of the European Societies of Cardiology, Atherosclerosis, and Hypertension (ESC/EAS/ESH) from 1994 (1998 guidelines in parenthesis) dietary and lifestyle interventions were indicated for arterial hypertension in 48.1% (43.0%) and/or for hypercholesterolaemia in 17.3% (78.8%). Drug treatment was indicated for arterial hypertension in 27.9% (30.6%) and for hypercholesterolaemia in 13.6% (19.1%) of asymptomatic siblings. Of those individuals with the respective indication, actual drug treatment was given for arterial hypertension in 91.5% (83.3%) and for hypercholesterolaemia in 46.4% (33.0%). However, treatment targets were reached in only 31.0% (28.2%) with arterial hypertension and in 7.2% (5.2%) with hypercholesterolaemia, respectively. CONCLUSIONS: Most asymptomatic individuals with positive fraternal family history have more than one modifiable risk factor. Interestingly, a large number of these individuals appears to be under medical surveillance as many receive some sort of drug treatment. However, this therapy did not meet the treatment goals in the majority of those with arterial hypertension and/or hypercholesterolaemia. Thus, although individuals with a positive fraternal history for myocardial infarction can be easily identified, implementation of sufficient preventive strategies continues to be poor in a Western European country.

Adult↗

PubMed2001

Long-term effects of in-hospital cardiac rehabilitation on the cardiac risk profile. A case-control study in pairs of siblings with myocardial infarction.

AIMS: In the general population, measures for secondary prevention of myocardial infarction are poorly utilized. Our aim was therefore to analyse whether post-myocardial infarction in-hospital rehabilitation and education programmes improve the subsequent utilization of preventive strategies. METHODS AND RESULTS: We screened 93 500 patient charts in cardiac rehabilitation clinics to identify a myocardial infarction patient with a sibling, who likewise had a myocardial infarction prior to the age of 60 years but was discordant with respect to the participation in cardiac in-hospital rehabilitation. In 92 such sibling pairs the coronary risk profile was studied by standardized questionnaire, biochemical measurements and physical examination. At the time of the acute myocardial infarction, both groups showed an equal risk factor distribution. However, at follow-up (on average 5.5 years after myocardial infarction), rehabilitation-siblings presented with significantly lower systolic (137+/-2 vs 150+/-3 mmHg, P<0.01) and diastolic blood pressure (82+/-1 vs 89+/-1 mmHg, P<0.01). Antihypertensive drug therapy resulted more often in effective (<or=140/90 mmHg) control of blood pressure (58% vs 29%, P<0.01). Blood lipid levels and smoking prevalence tended to be lower in rehabilitation-siblings. Significantly fewer rehabilitation-siblings presented with two or more modifiable risk factors (OR 0.36 (CI 0.17-0.76); P<0.01). There was a strong tendency towards fewer recurrent cardiac events (re-myocardial infarction, coronary angioplasty, coronary artery bypass grafting) during follow-up in rehabilitation-siblings (OR 0.57 (CI 0.31-1.04); P=0.07). CONCLUSION: An in-hospital programme for cardiac rehabilitation may successfully encourage therapy to modify risk factors and thus enhance the long-term implementation of secondary prevention.

Case-Control Studies↗

PubMed2001

Effects of an onion-olive oil maceration product containing essential ingredients of the Mediterranean diet on blood pressure and blood fluidity.

Twenty-four patients with arterial hypertension (WHO class I) received either 4 capsules of an onion-olive oil maceration product, containing essential ingredients of the Mediterranean diet, or placebo daily over a period of one week. In order to investigate the acute effect on arterial blood pressure, measurements were performed before and 5 h after the administration of the first dose of 4 capsules verum or placebo, respectively. For the evaluation of the long term effect further blood pressure measurements were performed after one week's treatment with a daily dose of 4 capsules. After a wash-out phase of 2 weeks followed by a crossover, the second study phase, which was identical in design, was carried out. In addition patients were instructed to measure their blood pressure 4 times daily at home for the whole study period. Haemorheological parameters (platelet aggregation, erythrocyte aggregation, plasma viscosity and haematocrit) were also determined at the measuring points mentioned above. The onion-olive oil maceration product led to a significant decrease in systolic blood pressure. There was also a trend towards a decrease in diastolic blood pressure. The improved blood fluidity observed resulted from a decrease in haematocrit. All effects could be shown immediately and after one week's administration.

Adult↗

PubMed2001

Chromosomal insertion and excision of a 30 kb unstable genetic element is responsible for phase variation of lipopolysaccharide and other virulence determinants in Legionella pneumophila.

We recently described the phase-variable expression of a virulence-associated lipopolysaccharide (LPS) epitope in Legionella pneumophila. In this study, the molecular mechanism for phase variation was investigated. We identified a 30 kb unstable genetic element as the molecular origin for LPS phase variation. Thirty putative genes were encoded on the 30 kb sequence, organized in two putative opposite transcription units. Some of the open reading frames (ORFs) shared homologies with bacteriophage genes, suggesting that the 30 kb element was of phage origin. In the virulent wild-type strain, the 30 kb element was located on the chromosome, whereas excision from the chromosome and replication as a high-copy plasmid resulted in the mutant phenotype, which is characterized by alteration of an LPS epitope and loss of virulence. Mapping and sequencing of the insertion site in the genome revealed that the chromosomal attachment site was located in an intergenic region flanked by genes of unknown function. As phage release could not be induced by mitomycin C, it is conceivable that the 30 kb element is a non-functional phage remnant. The protein encoded by ORF T on the 30 kb plasmid could be isolated by an outer membrane preparation, indicating that the genes encoded on the 30 kb element are expressed in the mutant phenotype. Therefore, it is conceivable that the phenotypic alterations seen in the mutant depend on high-copy replication of the 30 kb element and expression of the encoded genes. Excision of the 30 kb element from the chromosome was found to occur in a RecA-independent pathway, presumably by the involvement of RecE, RecT and RusA homologues that are encoded on the 30 kb element.

Blotting, Southern↗

PubMed2001

Molecular mechanisms involved in the synergistic activation of soluble guanylyl cyclase by YC-1 and nitric oxide in endothelial cells.

YC-1 is a direct activator of soluble guanylyl cyclase (sGC) and sensitizes the enzyme for activation by nitric oxide (NO) and CO. Because the potentiating effect of YC-1 on NO-induced cGMP formation in platelets and smooth muscle cells has been shown to be substantially higher than observed with the purified enzyme, the synergism between heme ligands and YC-1 is apparently more pronounced in intact cells than in cell-free systems. Here, we investigated the mechanisms underlying the synergistic activation of sGC by YC-1 and NO in endothelial cells. Stimulation of the cells with YC-1 enhanced cGMP accumulation up to approximately 100-fold. The maximal effect of YC-1 was more pronounced than that of the NO donor DEA/NO (approximately 20-fold increase in cGMP accumulation) and markedly diminished in the presence of L-N(G)-nitroarginine, EGTA, or oxyhemoglobin. Because YC-1 did not activate endothelial NO synthase, the pronounced effect of YC-1 on cGMP accumulation was apparently caused by a synergistic activation of sGC by YC-1 and basal NO. The effect of YC-1 was further enhanced by addition of DEA/NO, resulting in a approximately 160-fold stimulation of cGMP accumulation. Thus, YC-1 increased the NO-induced accumulation of cGMP in intact cells by approximately 8-fold. Addition of endothelial cell homogenate increased the stimulatory effect of YC-1 on NO-activated purified sGC from 1.2- to 3.7-fold. This effect was not observed with heat-denatured homogenates, suggesting that a heat-labile factor present in endothelial cells potentiates the effect of YC-1 on NO-activated sGC.

Animals↗