Biomedical subjects
Publications and source records attributed to A Müller.
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The dihydropyridine S(-)-Bay K 8644 (Bay K), the benzoylpyrrole FPL 64176 (FPL) and the benzodiazocine CGP 48506 (CGP) are structurally unrelated L-type Ca2+ channels agonists. The aim of our study was to investigate whether these three drugs interact with different binding sites and thereby modulate the behaviour of L-type Ca2+ channels in a qualitatively different manner. Single-channel recordings were performed on CHO cells stably expressing the alpha1C-b subunit of the L-type Ca2+ channel. Mean open time and open probability were determined sweep by sweep and the effects of CGP (10(-4) M), Bay K (10(-6) M) and FPL (10(-6) M) were compared. All three compounds increased mean open time and open probability when applied alone. However, the gating pattern changes induced by each drug were qualitatively and quantitatively different. We also applied binary mixtures and analysed the resulting sweeps with respect to their gating pattern. The application of mixtures did result in a gating pattern not seen with any of the single drugs. The mixture of CGP and FPL led to a prolonged mean open time compared with each single drug. The mixture of Bay K and FPL exhibited an open probability lower than with each single drug. The mixture of CGP and Bay K increased the mean open time per sweep like Bay K, but the number of openings was similar to the level seen with CGP alone. These results cannot be explained by assuming alternative binding of the drugs to a single binding site. We therefore conclude that Bay K, CGP and FPL bind to different but interacting sites on the L-type Ca2+ channel.
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DNA methylation plays an important part in the regulation of gene expression. Alterations in DNA methylation in tumours have been reported and have been used to generate hypotheses about mutagenesis and silencing of tumour suppressor genes. However, the underlying mechanism is still poorly understood, and conflicting data on the levels of overexpression of 5'-cytosine DNA methyltransferase in sporadic colon carcinoma have been published. We used a competitive RT-PCR assay for quantification of mRNA of 5'-cytosine DNA methyltransferase in colon biopsies obtained from patients with hereditary colon carcinoma syndromes and compared the results with those obtained in a control group. No significant difference was found between the flat mucosa of FAP patients and the mucosa of the control group. In FAP and HNPCC patients, the 5'-cytosine DNA methyltransferase mRNA levels of adenomas were significantly higher (P<0.05) than of flat mucosa in the same group, but both showed great variability from patient to patient. Our findings suggest that the mRNA levels of methyltransferase cannot be used as predictive marker for screening in families affected by hereditary colon carcinoma.
Internal gunshot wounds in the head and neck region are complicated. Two cases of such injuries in the head and neck region are introduced and therapeutic approaches are discussed. If there are no severe additional injuries, the treatment of choice is the endoscopic removal of the projectile. Alternatively, the projectile has to be taken out by conventional surgery, using the approach which induces the least stress for the patient.
BACKGROUND & AIMS: Patients with cirrhosis are characterized by a reduced splanchnic vascular resistance and a hyporeactivity to adrenergic vasoconstrictors. So far, their adrenergic splanchnic vascular responsiveness has not been evaluated in vitro. We compared responses to alpha1- and beta2-adrenoceptor stimulation of hepatic arteries and portal veins of patients with cirrhosis undergoing transplantation with those of organ donors. METHODS: Isometric contractions of endothelium-denuded vessel rings were induced cumulatively by methoxamine and relaxations by isoproterenol. Results are expressed as percentage of the contraction obtained by 85 mmol/L KCl or of the relaxation obtained by 100 micromol/L papaverine, respectively. RESULTS: Maximal methoxamine-induced contractions were reduced in cirrhotic hepatic arteries (cirrhosis, 51.8% +/- 6.8%; donor, 89.9% +/- 6.6%; P < 0.01) and portal veins (cirrhosis, 49.2% +/- 6.4%; donor, 94.0% +/- 5.3%; P < 0.01). In cirrhosis, isoproterenol induced a less marked relaxation of hepatic arteries (cirrhosis, 46.6% +/- 3.2%; donor, 100.3% +/- 4.4%; P < 0. 01) but an increased relaxation of portal veins (cirrhosis, 41.9% +/- 6.2%; donor, 26.2% +/- 2.8%; P < 0.01). CONCLUSIONS: In cirrhosis, endothelium-free hepatic arteries are hyporeactive to alpha1- and beta2-adrenoceptor agonists, and portal veins are hyporeactive to alpha1- but hyperreactive to beta2-adrenoceptor agonists. These findings support the in vivo findings of a hyporesponsiveness to adrenergic vasoconstrictors in patients with cirrhosis.
Cryptosporidia and microsporidia are emerging parasitic pathogens in immunocompetent and immunocompromised individuals. Cryptosporidium infects several wild and domestic animals that excrete oocysts into the environment and contaminated water represents the major source of infection for humans. Waterborne transmission of Cryptosporidium is a major risk for humans and appropriate measures have to be taken to protect immunocompetent and immunocompromised individuals to become infected. For microsporidia, the sources and ways of transmission are not well documented. Although several animal hosts have been identified recently, the relevant reservoirs of human microsporidia are still unknown. Also, the routes of spreading are unknown. Is microsporidiosis a zoonotic disease that will be transmitted through close contact with infected animals or is contaminated surface water responsible for transmission and represents a relevant reservoir? This review is designed to give information on these two emerging intestinal parasites in a format that will be useful to clinical microbiologists, physicians interested in infectious diseases, and public health personnel.
We investigated the prophylactical administration of liposomal amphotericin B (Ambisome) in the early phase after liver transplantation (LTx). Fifty-eight patients received Ambisome prophylactically after LTx. Ambisome (1 mg kg-1 day-1) was given intravenously for 7 days after LTx. Immunosuppressive prophylaxis was cyclosporin A (CsA) based in 11 patients. Forty-seven patients had a tacrolimus-based immunosuppressive regimen. CsA and tacrolimus dosages were adjusted to trough levels of 150-250 ng ml-1 (EMIT) and 5-15 ng ml-1 (MEIA II) respectively. Three patients died from sepsis due to Aspergillus fumigatus infection. Reasons for a fatal outcome were foudroyant Aspergillus pneumonia in a patient transplanted for fulminant hepatic failure on post-operative day (pod) 8; Aspergillus sepsis with severe endocardidtis in a patient with two retransplantations for graft non/dysfunction on pod 24; and disseminated aspergillosis due to Aspergillus fumigatus in a patient retransplanted for primary non-function (pod 19). All three patients underwent haemofiltration for renal failure. One patient with Candida albicans sepsis (pod 4) recovered under increased dosage of Ambisome (3 mg kg-1 per day). Ambisome (1 mg kg-1 per day) seems to be beneficial against systemic Candida infections. However, the onset of systemic Aspergillus infections could not be prevented. Obviously, higher Ambisome doses appear to be necessary against Aspergillus. We recommend the use of Ambisome (3 mg kg-1 per day) for patients with risk factors such as graft dys-/non-function, retransplantation, haemofiltration and complicated acute liver failure to prevent invasive aspergillosis.
The inhibition of LDL-oxidation by 17-alpha estradiol was assessed in vitro by the determination of the duration of the lag-phase in copper ion-induced oxidation and compared to that of 17-beta estradiol, estriol, and probucol. Addition of 0.2, 0.4, and 1 micromol/l of the test substances prolonged the lag-phase of LDL-oxidation 1.3-(+/-0.09 SD), 1.7-(+/-0.14 SD), and 2.7-(+/-0.25 SD) fold for 17-alpha estradiol; 1.4-(+/-0.14 SD), 1.8-(+/-0.1 SD), and 2.6-(+/-0.16 SD) fold for 17-beta estradiol; 1.1-(+/-0.07 SD), 1.4-(+/-0.11 SD), and 1.6-(+/-0.11 SD) fold for estriol as well as 1.4-(+/-0.14 SD), 1.6-(+/-0.1 SD), and 3.0-(+/-0.21) fold for probucol, thus proving that 17-alpha estradiol is as effective as 17-beta estradiol or similar to probucol and more effective than estriol (n = 6 in all cases). These data demonstrate that 17-alpha estradiol is able to delay LDL-oxidation, hence providing a basis for clinical examination of the protective effects of 17-alpha estradiol against atherosclerosis in patients where hormonal effects of 17-beta estradiol are undesirable.
Crataegus extract is used in cardiology for the treatment of mild to moderate heart failure (NYHA II) in Germany. However, little is known about the electrophysiological actions of Crataegus extract in the heart. Recently, it was shown that Crataegus extract prolongs the refractory period in isolated perfused hearts and increases action potential duration in guinea pig papillary muscle. It was the aim of this study to find out the mechanism of the increase in action potential duration caused by Crataegus extract. Using the patch-clamp technique, we measured the effects of Crataegus extract (10 mg/l; flavonoid content: 2.25%, total procyanidin content: 11.3 +/- 0.4%) on the inward rectifier and the delayed rectifier potassium current in isolated guinea pig ventricular myocytes. To get some insight into the mechanism underlying the positive inotropic effect of Crataegus extract, we also looked for effects on the L-type calcium current. Crataegus extract slightly blocked both the delayed and the inward rectifier potassium current. The inhibition amounted to 25% and about 15%, respectively. This amount of inhibition of these repolarising currents is sufficient to explain the prolongation of action potential duration caused by Crataegus extract. To our surprise we could not detect any influence of Crataegus extract on the L-type calcium current. In summary, our results show that Crataegus extract blocks repolarising potassium currents in ventricular myocytes. This effect is similar to the action of class III antiarrhythmic drugs and might be the basis of the antiarrhythmic effects described for Crataegus extract. Our measurements of the L-type calcium current indicate that Crataegus extract's positive inotropic effect is not caused by phosphodiesterase inhibition or a beta-sympathomimetic effect.
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OBJECTIVE: Regarding interactions between pro-inflammatory cytokines and bone metabolism in rheumatoid arthritis (RA), we investigated the relationship between the serum levels of interleukin (IL)-1beta, IL-6, soluble interleukin-2 receptor (sIL-2r), C-reactive protein (CRP), the vitamin D metabolites 25-hydroxyvitamin D3 (25OHD3) and 1,25-dihydroxyvitamin D3 [1,25(OH)2D3], intact parathyroid hormone (iPTH) as well as serum and urinary parameters of bone turnover in 74 post-menopausal women with RA. RESULTS: SIL-2r correlated negatively with 1,25(OH)2D3 (P < 0.01), whereas IL-6 showed a positive correlation with urinary excretion of deoxypyridinoline collagen cross-links (P < 0.01). 1,25(OH)2D3 (P < 0.01) and iPTH (P < 0.01) were negatively related to CRP, whereas the urinary excretion of pyridinoline (P < 0.01) and deoxypyridinoline (P < 0.01)-collagen cross-links showed a positive correlation with CRP. 1,25(OH)2D3 (P < 0.01) and iPTH (P < 0.05) were positively related to bone alkaline phosphatase as a marker of osteoblast function. CONCLUSION: Our data indicate that IL-6 is a critical determinant of increased bone resorption in post-menopausal RA women with high disease activity and that serum levels of 1,25(OH)2D3 are inversely related to T-cell activation.
Defibrillation shocks are commonly used after cardiac surgery or during defibrillator implantation. The hemodynamic consequences of countershocks on circulatory dynamics are not completely understood, and there is a lack of information concerning the effects on ventriculoarterial interaction. The study presented here was performed to assess the influence of defibrillation shocks on arterial hemodynamics and ventriculoarterial coupling. Eight mongrel dogs (weight 15-18 kg) were anesthetized and median thoracotomy was performed. Pressure in the ascending aorta and the left ventricle and flow in the ascending aorta were continuously monitored. After induction of atrial or ventricular fibrillation, termination was achieved by epicardial low energy shocks (atrium, 3J; ventricle, 51). In an additional attempt ventricular fibrillation was terminated by a high energy shock (34J). Aortic input impedance was calculated by fast-Fourier-transformation of aortic flow and pressure signals, while ventriculoarterial coupling was expressed by the ratio of aortic and ventricular end systolic elastance (Ea/Ees). Defibrillation by low energy shocks of atrial or ventricular fibrillation did not result in changes of the aortic impedance spectrum, and ventriculoarterial coupling remained unaltered compared to control conditions. High energy defibrillation, however, resulted in a marked rise in total peripheral resistance (P < 0.03). The ratio of Ea/Ees increased significantly (P < 0.005). These effects were reversible within 15 minutes. Low energy defibrillation does not alter arterial hemodynamics and ventriculoarterial coupling in this experimental setup. High energy defibrillation, however, results in a temporary increase of ventricular load. This finding may be of particular interest in patients with poor left ventricular function.
The diagnosis of intestinal microsporidiosis has traditionally depended on direct visualization of the parasite in stool specimens or intestinal biopsy samples by light and/or electron microscopy. Limited information about the specificity and sensitivity of PCR for the detection microsporidia in clinical stool specimens is available. To establish a sensitive and specific method for the detection of microsporidia in clinical samples, we studied clinical stool specimens of 104 randomly selected human immunodeficiency virus-infected patients with diarrhea to compare light microscopy and PCR. Fluorochrome Uvitex 2B staining was used for light microscopy. To raise the sensitivity of PCR, we used a powerful and fast DNA extraction method including stool sedimentation, glass bead disruption, and proteinase K and chitinase digestion. PCR was performed with primer pairs V1-PMP2, V1-EB450, and V1-SI500, and the nature of the PCR products was confirmed by Southern blot hybridization. Microsporidiosis was diagnosed by light microscopy in eight patients. Ten patients tested positive for microsporidiosis by PCR. Enterocytozoon bieneusi was found in seven cases, and Encephalitozoon intestinalis was found in four cases. In one case a double infection with E. bieneusi and E. intestinalis was diagnosed by PCR, whereas light microscopy showed only E. bieneusi infection. PCR testing of stool specimens is useful for diagnosis and species differentiation of intestinal microsporidiosis in HIV patients.
Microsporidia are obligate intracellular protozoan parasites that infect a broad range of vertebrates and invertebrates. These parasites are now recognized as one of the most common pathogens in human immunodeficiency virus-infected patients. For most patients with infectious diseases, microbiological isolation and identification techniques offer the most rapid and specific determination of the etiologic agent. This is not a suitable procedure for microsporidia, which are obligate intracellular parasites requiring cell culture systems for growth. Therefore, the diagnosis of microsporidiosis currently depends on morphological demonstration of the organisms themselves. Although the diagnosis of microsporidiosis and identification of microsporidia by light microscopy have greatly improved during the last few years, species differentiation by these techniques is usually impossible and transmission electron microscopy may be necessary. Immunfluorescent-staining techniques have been developed for species differentiation of microsporidia, but the antibodies used in these procedures are available only at research laboratories at present. During the last 10 years, the detection of infectious disease agents has begun to include the use of nucleic acid-based technologies. Diagnosis of infection caused by parasitic organisms is the last field of clinical microbiology to incorporate these techniques and molecular techniques (e.g., PCR and hybridization assays) have recently been developed for the detection, species differentiation, and phylogenetic analysis of microsporidia. In this paper we review human microsporidial infections and describe and discuss these newly developed molecular techniques.
The potential use as vaccine delivery system of Salmonella typhimurium strains harboring defined mutations in the sseC (HH104) and sseD (MvP101) genes, which encode putative effector proteins of the type III secretion system of Salmonella pathogenicity island 2, was evaluated and compared with that of the well-characterized aroA mutant strain SL7207 by using beta-galactosidase (beta-Gal) as a model antigen. When orally administered to immune-competent or gamma interferon-deficient (IFN-gamma-/-) BALB/c mice, both mutants were found to be highly attenuated (50% lethal dose, >10(9) bacteria). Both strains were also able to efficiently colonize and persist in Peyer's patches. Immunization with HH104 and MvP101 triggered beta-Gal-specific serum and mucosal antibody responses equivalent to or stronger than those observed in SL7207-immunized mice. Although immunoglobulin G2 (IgG2) serum antibodies were dominant in all groups, IgG1 was also significantly increased in mice vaccinated with MvP101 and SL7207. Comparable beta-Gal-specific IgA and IgG antibodies were detected in intestinal lavages from mice immunized with the different strains. Antigen-specific CD4(+) T-helper cells were generated after vaccination with all vaccine prototypes; however, responses were significantly more efficient when HH104 and MvP101 were used (P < 0.05). Significantly higher levels of IFN-gamma were produced by restimulated spleen cells from mice immunized with HH104 than from those vaccinated with the MvP101 or SL7207 derivatives (P </= 0.05). Interestingly, the three strains induced major histocompatibility complex class I-restricted CD8(+) cytotoxic T cells against beta-Gal; however, cytotoxic T-lymphocyte responses were significantly stronger after immunization with HH104 (P < 0.05). These novel S. typhimurium attenuated strains constitute promising delivery systems for vaccine antigens. The qualitative differences observed in the obtained responses with different carriers may be useful for those applications in which a targeted immunomodulation is required.
Measurement of gap junction conductance (gj) with patch-clamp amplifiers can, due to series resistance problems, be subject to considerable errors when large currents are measured. Formulas developed to correct for these errors unfortunately depend on exact estimates of series resistance, which are not always easy to obtain. Discontinuous single-electrode voltage-clamp amplifiers (DSEVCs) were shown to overcome series resistance problems in single whole cell recording. With the use of two synchronized DSEVCs, the simulated gj in a model circuit can be measured with a maximum error of <5% in all recording situations investigated (series resistance, 5-47 MOmega; membrane resistance, 20-1,000 MOmega; gj, 1-100 nS). At a very low gj of 100 pS, the error sometimes exceeded 5% (maximum of 15%), but the error was always <5% when membrane resistance was >100 MOmega. The precision of the measurements is independent of series resistance, membrane resistance, and gj. Consequently, it is possible to calculate gj directly from Ohm's law, i.e., without using correction formulas. Our results suggest that DSEVCs should be used to measure gj if large currents must be recorded, i.e., if cells are well coupled or if membrane resistance is low.