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Biomedical subjects

S Müller

Publications and source records attributed to S Müller.

At least 451 records · Page 25Linked to original sources

Human brainstem auditory evoked potentials (BAEP) before and after MR examinations.

Recently significant changes of human brainstem auditory evoked potentials (BAEP) after exposure to static magnetic fields were reported (L. von Klitzing, Clin. Physiol. Meas. 7(2), 157 (1986); L. Stojan, D. Sperber, and K. Dransfeld, Naturwissenschaften 75, 622 (1988]. We recorded BAEPs of 11 subjects before and after a routine MRI examination at 1.5 T. In addition the BAEP of a healthy volunteer was measured in five different static magnetic fields (0-2.0 T). Our results indicate that routine MRI investigations do not significantly alter the interpeak latencies of the BAEPs.

Electromagnetic Fields↗

Continent appendix stoma: a modification of the Mainz pouch technique.

The submucosally embedded in situ appendix guarantees an ideal continence mechanism in patients with ileocecal urinary reservoirs. To date this modification of the Mainz pouch technique has been performed successfully in 13 patients. The appendicocutaneous stoma was placed at the lower right abdominal quadrant in 12 patients and into the umbilical funnel in 1. Urodynamic investigations of the submucosally embedded appendix showed a maximum closure pressure of more than 80 cm. water in pressure profiles. Only 1 case of stomal stenosis required reoperation.

Adult↗

A method to determine the end point of decalcification of hard tissue and bone.

A method for decalcification end point determination of mineralized tissue is described. The calcium content of the decalcification solution was determined colorimetrically with a "continuous automatic analyzer" with a high degree of accuracy. The end point method used has been tested on two decalcification methods, 5% nitric acid with or without ultrasonic treatment. The results suggest it is possible to quantitate the decalcification process.

Adult↗

[The diagnostic value of captopril radionuclide nephrography for renovascular hypertension in childhood].

In four children the role of captopril-radionuclide nephrography in the diagnosis of renovascular hypertension was studied. Captopril (0.5-1.0 mg/kg orally) did not affect Iodine-123 Hippuran nephrography in two children with mild renal artery stenosis, but induced an accumulation of the tracer within the kidneys in two children with hemodynamically significant renal artery stenosis. As in adults Iodine 123 Hippuran nephrography appears to be a useful tool to identify patients with significant renal artery stenosis.

Adolescent↗

Subacute carbon disulfide exposure modifies adrenergic cardiovascular actions in rats.

The influence of subacute carbon disulfide exposure (1.66 or 3.32 mmol/kg) on cardiovascular actions of epinephrine (1 or 4 micrograms/kg iv) and norepinephrine (2 or 10 micrograms/kg iv) was investigated in the urethane-anesthetized rat model. Hypertensive adrenergic effects were enhanced and inotropic effects were diminished in carbon disulfide exposed rats. Atrioventricular impulse conduction was delayed after carbon disulfide exposure, and we observed an increased number of extrasystoles in these animals. Transient T-wave elevation after catecholamine injection was augmented in carbon disulfide exposed rats. Our results demonstrate that subacute carbon disulfide exposure modifies adrenergic cardiovascular actions in rats.

Animals↗

Identification of an amplification promoting DNA sequence from the hypotrichous ciliate Stylonychia lemnae.

The macronucleus of the hypotrichous ciliate Stylonychia lemnae contains a 1218 bp long DNA molecule which becomes highly amplified during vegetative growth due to a continuous overreplication over a long time range. The region which is located upstream the open reading frame of the overamplified 1.2kbp Stylonychia DNA molecule enabled plasmids containing an inefficiently transcribed thymidine kinase gene to persist and amplify upon transfection into mouse L fibroblasts under selective conditions. This region contains long AT-rich stretches. The AT-rich sequences interact with a previously characterized HMG-I like protein from mouse Ehrlich ascites tumour cells. A binding activity for AT-rich stretches could also be identified in macronuclear extracts from Stylonychia lemnae. We suggest a common mechanism for overamplification in Stylonychia macronuclei during vegetative growth and amplification of plasmid DNA in heterologous mouse cells under the influence of a common element.

Amino Acid Sequence↗

[Dilated cardiomyopathy--heart muscle disease of unknown origin or an autoimmune disease? New aspects of etiology, pathogenesis and clinical practice].

Recent evidence suggests that the most common form of idiopathic cardiomyopathy in our altitudes, the dilated cardiomyopathy (DCM), is a post-infectious autoimmune disease which is triggered by virus infections. In animal experiments, the development of the coxsackie virus B3 myocarditis to a congestive cardiac insufficiency resembling the clinical picture of DCM was demonstrated. In mice, species-dependent varying disease courses could be observed, which point to a genetically different behaviour of the animals' immunological reactions, either humoral or T-cell mediated immune reactions being responsible. In comparison with non-DCM patients, patients with DCM and chronic myocarditis exhibit significantly higher coxsackie virus antibody titres. Obviously, also a differently long viral persistency in the cardiac muscle plays a role, as enterovirus-specific RNA was detected in myocardial biopsies from patients with DCM. Along with myocardial fibroses, endomyocardial biopsies in DCM frequently reveal mononuclear cellular infiltrates, which, however, only in 20-25% of the cases may be regarded as chronic persisting myocarditis. The clinical and paraclinical findings in DCM and in the so-called latent cardiomyopathy are presented. In congestive heart failure, the best therapeutic results are achieved by the ACE inhibitors, along with vasodilator agents, digitalis glycosides and diuretics. Ultima ratio is the orthotopic heart transplantation, as it is only this intervention that will be able to improve the primarily bad prognosis decisively. Whether the treatment with immunosuppressive drugs exerts an influence upon the prognosis, has thus far remained an open question.

Animals↗

[Ventricular late potentials in patients with cardiomyopathies in relation to electrophysiologic and myocardial biopsy findings].

With the noninvasive registration of late ventricular potentials there is the possibility to obtain statements about a regionally delayed excitation of ventricular parts which may refer to an increased inclination to ventricular tachyarrhythmias. Late ventricular potentials in patients with suspicion of primary diseases of the myocardium more frequently appeared both in the case of inducible non-sustained or sustained ventricular tachycardias and in the presence of simultaneous fibrous hypertrophy of the myocardium and interstitial fibrosis in the bioptate of the myocardium than in noninducibility of ventricular tachycardias and in the absence of histological changes of the myocardium. Thus in patients with cardiomyopathies a certain predicting significance seems to be ascribed to the evidence of late potentials in the highly increased signal-averaged ECG both for the ability to evoke ventricular tachycardias by programmed ventricular stimulation and for the presence of more distinct histological changes of the myocardium.

Adult↗

[Malignant melanoma and HIV infection].

Among 1000 patients with HIV infection consecutively examined at our dermatological department during the last 3 years, we diagnosed 4 cases of malignant melanoma. This figure is clearly higher than the statistical incidence of 4-13 cases per 100.000 people a year observed in West Germany. The mean age of our 4 patients and 3 additional cases reported in the literature is 10 years less than the average age found in melanoma patients without HIV infection. These findings indicate an increased risk of malignant melanoma in patients with HIV infection. In most of our patients, the cellular immunity was only marginally impaired, corresponding to the stages WR1 and WR2 (Walter Reed classification). Tumor formation, therefore, does apparently not depend on the severity of decompensation of the immunity.

Acquired Immunodeficiency Syndrome↗

Tachykinins, calcitonin gene-related peptide and neuropeptide Y in nerves of the mammalian thymus: interactions with mast cells in autonomic and sensory neuroimmunomodulation?

By the use of light microscopic (LM) immunohistochemistry the distribution of tachykinin (TK)-, calcitonin gene-related peptide (CGRP)- and neuropeptide Y (NPY)-like immunoreactivity in nerves supplying the mammalian (rat, mouse, guinea-pig, cat) thymus gland has been determined. There were no interspecies variations. Fibres staining for TK and CGRP completely overlapped indicating coexistence. They were present in the capsule, in interlobular septa and in the corticomedullary boundary and occurred in perivascular and paravascular plexus supplying arteries, veins and the microvasculature. Some TK/CGRP-immunoreactive (ir) fibres travelled between lymphoid cells and close contacts with mast cells were frequent. NPY-ir fibres were different from those staining for TK/CGRP and predominated in the perivascular plexus of arterial blood vessels. Only very rarely they coursed in the lymphoid parenchyma. Intimate contacts of NPY-ir fibres with mast cells were less frequent than those of TK/CGRP-ir fibres. We conclude that the NPY innervation is mainly sympathetic noradrenergic while thymic nerves coding for TK and CGRP are most likely of sensory origin. These pathways may play a differential neuroimmunomodulatory role in the thymus, possibly via interaction with mast cells.

Adrenergic Fibers↗

Perturbation of the idiotypic network. I. Induction with multiple alloantigen stimulation.

The effect of hyperimmunization on the immune network with allostimulated syngeneic lymphocytes responding to different haplotypes was analyzed. Ten different haplotypes were used to stimulate syngeneic donor mice. Control mice were multiply immunized with incomplete Freund's adjuvant alone or with syngeneic mixed lymphocyte culture-generated lymphocytes. BALB/c mice were immunized consecutively with alloreactive blasts or allogeneically stimulated spleen cells at 10-day intervals. After a rest period of 2 months, the ratio of T helpers to T suppressors was determined by immunofluorescent staining. The functional network was probed by immunizing the mice with phosphorylcholine (PC) coupled to hemocyanin. The sera were analyzed for anti-PC antibodies and TEPC15 (T15) idiotypic expression. The results demonstrated (i) a decrease in the level of anti-PC antibody titer and T15 idiotypic expression; (ii) a decrease in the number of T helper cells and an increase in the number of T suppressor cells; (iii) a loss of PC epitope specificity; (iv) an increase of IgM antibodies expressing T15 without anti-PC specificity; and (v) an elevated level of preimmune lymphocyte proliferation and Ig secretion. These results reveal a functional network linkage in the regulation of alloreactivity and antigen response and show how repeated exposure to alloantigens can induce a perturbation of the idiotypic network controlling the response of a non-alloantigen-related BALB/c strain dominant idiotype (T15).

Animals↗

Perturbation of the idiotypic network. II. Transfer of suppression to neonatal mice.

The cellular mechanisms which are responsible for idiotype perturbation induced by repeated stimulation with either allogeneic mixed lymphocyte culture-generated syngeneic blasts or allogeneically stimulated syngeneic spleen cells were investigated as described in the preceding article. Using the splenic fragment culture system, the precursor frequencies of T and B cells for anti-phosphorylcholine (PC) antibodies and T15 idiotypic antibodies were determined in allogeneically challenged mice. Adoptive transfers of T cells to neonatal BALB/c mice induced suppression of the T15+ anti-PC responses. In addition, the effect of immunization with internal image-bearing anti-idiotopes on the level of anti-PC antibodies and T15 idiotype was determined. Results from this study demonstrated (i) a decrease in the precursor frequency in the PC-specific and idiotype-specific B cell repertoire; (ii) a decrease in the precursor frequency of T helper cells, which recognize idiotypes and anti-idiotypes; (iii) the possibility to transfer T15 suppression to neonatal mice; and (iv) the possibility to restore T15 dominance by anti-idiotypic antibody immunization. These data indicate that both the T and B compartments are involved in the maintenance of suppression induced by repeated exposure to alloantigen-sensitized syngeneic cells. Collectively these findings show that a nonspecific general suppression induced by allohyperimmunization can perturb the T15+ anti-PC response.

Animals↗

Simultaneous multislice imaging (SIMUSIM) for improved cardiac imaging.

In conventional ECG gated multislice imaging of the heart, slice position and phase in the heart cycle are not independent parameters. This drawback is removed by simultaneous imaging of multiple slices. This paper describes a technique which is based on simultaneous excitation of several slices by multifrequency selective rf pulses. In comparison to conventional cardiac multislice imaging an improved quality of heart images is obtained, because more acquisitions are attributed to the MR signal of the slices. The gain in signal-to-noise ratio per measurement time increases with the square root of the number of slices investigated simultaneously. This is demonstrated using phantom experiments and cardiac images.

Coronary Disease↗

13C spectroscopic imaging. A simple approach to in vivo 13C investigations.

13C spectroscopic imaging (SI) is implemented and tested on a Siemens whole-body MR instrument for in vivo localized 13C spectroscopy. The method provides spectroscopic maps of extended regions of interest. It is found that 13C SI is an ideal field of application for the spectroscopic imaging technique since most other localization methods suffer from chemical-shift or offset artifacts for this nucleus. Applications of 13C SI with a single 13C rf channel as well as in combination with polarization transfer experiments and heteronuclear broadband decoupling are shown.

Carbon Isotopes↗

Simultaneous multivolume spectroscopy (SIMUVOSP) using local techniques.

MR spectra simultaneously acquired from different locations in the human body may be obtained with the SIMUVOSP technique (Simultaneous Multivolume Spectroscopy). SIMUVOSP is based on multifrequency selective RF pulses which encode positional information of the spins into the phase of the MR signal. This paper describes SIMUVOSP strategies for 1H, 31P and 13C spectroscopy. For 1H SIMUVOSP the STEAM experiment may be modified by replacing the selective RF pulses with SIMUFREX pulses (Simultaneous Multifrequency Excitation pulses). This modification allows the simultaneous spectroscopic examination of different regions in the human brain. For 31P SIMUVOSP the ISIS method is combined with SIMUFRIN (Simultaneous Multifrequency Inversion) pulses, which generate the inversion of multiple regions during the RF pulse. An application of 31P SIMUVOSP is the study of the metabolic heterogeneity of the high energy phosphates within the human body. For 13C spectroscopy a localized polarization transfer experiment is combined with multivolume excitation. In this way SIMUVOSP on protons is extended to 13C multivolume spectroscopy.

Brain↗

The Drosophila melanogaster l(2)gl gene encodes a protein homologous to the cadherin cell-adhesion molecule family.

Mutations in the recessive Drosophila tumor gene l(2)gl affect growth and structural properties of neural tissues and imaginal discs during larval development. We have analyzed the cellular localization of transcripts and a 130-kDa protein encoded by the l(2)gl gene, using in situ hybridization and immunofluorescence techniques. Transcripts of maternal origin are detected in freshly laid eggs and are homogeneously incorporated into blastoderm cells. The protein is found at low levels in all embryonic tissues after blastoderm formation. In later stages differential expression of the protein is observed, particularly in cells of the nervous system. The protein is located at the cell surface of dissociated embryonic cells. Anti-l(2)gl sera show cross-reaction to a mouse protein that is localized at cell-cell contact sites in tissue culture cells. Moreover, amino acid sequence homology to deduced amino acid sequences of members of the vertebrate cadherin cell-adhesion molecule family suggests that the l(2)gl gene product may have properties of a cell-adhesion molecule.

Amino Acid Sequence↗