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Biomedical subjects

M Meyer

Publications and source records attributed to M Meyer.

At least 289 records · Page 16Linked to original sources
PubMed1997

Prophylactic use of low-dose urodilatin for prevention of renal impairment following liver transplantation: a randomized placebo-controlled study.

Many therapeutic measures have been employed to prevent or at least ameliorate postoperative renal impairment following liver transplantation. Recent clinical phase II studies have demonstrated that the new natriuretic peptide urodilatin has beneficial effects on renal function following heart and liver transplantation. The present study reports the first prospective randomized placebo-controlled trial of prophylactic urodilatin administration following liver transplantation. Seventy consecutive recipients of primary liver transplants were included in the study following randomization, and 33 patients continuously received urodilatin at a dose of 20 ng/kg/min for 7 d. The remaining 37 patients received a placebo infusion for the same time period. The course of serum creatinine and urea did not differ between the two groups nor did the daily urine production. However, the urodilatin group showed a higher preoperative median serum creatinine and a significant reduction on days 1 and 2, whereas this observation was not made in the placebo group. Furthermore, less furosemide was administered to the patients in the urodilatin group during the first 2 d. The incidence of postoperative hemodialysis and the number of treatments did not differ between the groups either (urodilatin group 4, vs. placebo group 6 and 22 for both groups, respectively). Side effects of the urodilatin therapy were not detected. The prophylactic low-dose urodilatin administration resulted in a trend towards amelioration of the renal function, but did not result in significant differences between the two experimental groups. Further studies, using higher doses, will be required to define the value of urodilatin for prevention of renal impairment after liver transplantation.

Adolescent↗
PubMed1997

[Irritable colon].

Irritable Bowel Syndrome (IBS) is a common functional gastrointestinal disorder, defined as a variable combination of chronic or recurrent gastrointestinal symptoms not explained by structural or biochemical abnormalities. It is attributable to the intestine with symptoms of abdominal pain, altered bowel habits and bloating. The diagnosis is primarily based on typical symptoms and prudent use of investigations to exclude organic disorders. The initial positive diagnosis is accurate and on a longterm follow-up its revision rarely required. A change in its clinical manifestation may imply the superimposition of another disorder. Treatment primarily rely on the confidence in the diagnosis and a strong physician-patient relationship. High fiber diets and bulking agents may be effective in alleviating symptoms. Though antispasmodic, antidiarrheal and psychotropic drugs are repeatedly used in patients with moderate to severe symptoms their effects remain uncertain. Psychotherapy, hypnosis and biofeedback may relief symptoms and may be considered for motivated patients with moderate to severe symptoms.

Colonic Diseases, Functional↗
PubMed1997

[Probability and strategy: an event-related potential study of processing syntactic anomalies].

Syntactic ambiguities requiring additional processing usually elicit positive going waveforms with onset latencies between 300 and 600 ms in the event-related potential (ERP). It is still unclear to what extent these components can be viewed either (a) as language specific in nature or (b) as members of the domain-unspecific P300 family of components. The present study investigates this question by means of probability manipulations applied to German sentences with subject-object ambiguities. Non-preferred object-subject (OS) word order requires structural revisions whereas the initially preferred subject-object (SO) word order does not. In the present experiment, the proportions of OS and SO structures were varied across experimental blocks (i.e., .25/.75 vs. .75/.25). The data of 20 participants reveal that ERP components were predominantly influenced when the subjects were explicitly informed about the actual proportions before each single block. In this case an early frontal positive component at about 400 ms and a subsequent posterior positivity were elicited by rare sentence structures irrespective of word order, suggesting that sentence processing was under strategic control. Conversely, participants that were not informed about sentence proportions showed larger positivities to the unpreferred OS sentences. Probability manipulations did not affect this pattern significantly. The data suggest that positivities evoked by syntactic ambiguities respond differently to probability manipulations than the P300 component.

Adult↗
PubMed1997

Effect of respiration and posture on heart rate variability.

The physiological control system of the heart produces a highly complex pattern of cardiac rhythmicity which is reflected in the variability of heart rate. The aim of this study was to analyse the effects of posture and breathing frequency on the cardiac control system by various noninvasive techniques. Seven healthy subjects (24+/-5 years, mean age+/-S.D.) were studied in the supine and sitting positions while breathing spontaneously or at a fixed rate (3, 6, 12, 24, 48, 60 breaths.min(-1)). Time series of instantaneous beat-to-beat heart rates were evaluated by spectral analysis and by the dimensionless approximate entropy parameter. The total spectral power as well as the low (<0.05 Hz) and mid frequency (0.05-0.12 Hz) spectral components were higher in the sitting position. Mean approximate entropy (+/-S.D.) (0.85+/-0.15 in sitting and 0.87+/-0.16 in lying subjects) was unaffected by postural changes or breathing frequencies higher than 6 breaths x min(-1). Analysis in the frequency domain revealed that the activity of the autonomic components controlling heart rate was modified by ventilation and postural changes, whereas approximate entropy, a unique measure of the complexity and integrity of the cardiac control system, was almost unaffected by respiration and posture.

Adult↗
PubMed1997

[Primary cutaneous monomelic B-cell lymphoma].

BACKGROUND: Cutaneous B cell lymphomas, especially when appearing as a monomelic papulonodular eruption, are rare. PATIENT: Ms H. 87-year-old, consulted for a papulonodular eruption of the left lower limb which developed during the past 5 months. This limb had been the site of a lymphedema since a traumatism 8 years ago. Histopathological analysis and immunostaining of a nodule showed that it was a large cell lymphoma of follicular stem cells. There was no extracutaneous involvement and the patient was successfully treated with radiotherapy. Two months after the completed radiotherapy a cutaneous relapse on the trunk and the upper limbs was treated with cyclophosphamide-vincristine-prednisone chemotherapy. DISCUSSION: Lymphedema probably played a role in the genesis of this lymphoma presumably by reducing the local immune response. It may have harmed endothelial cells and maintained an antigenic stimulation leading first to lymphocyte hyperplasia and eventually to a true lymphoma, in the same way this has been proved for some MALT lymphomas.

Aged↗
PubMed1996

Hydrogen bonding and molecular surface shape complementarity as a basis for protein docking.

A geometric docking algorithm based upon correlation analysis for quantification of geometric complementarity between protein molecular surfaces in close interfacial contact has been developed by a detailed optimization of the conformational search of the algorithm. In order to reduce the entire conformation space search required by the method a physico-chemical pre-filter of conformation space has been developed based upon the a priori assumption that two or more intermolecular hydrogen bonds are intrinsic to the mechanism of binding within protein complexes. Donor sites are defined spatially and directionally by the positions of explicitly calculated donor hydrogen atoms, and the vector space within a defined range about the donor atom-hydrogen atom bond vector. Acceptor sites are represented spatially and directionally by the van der Waals molecular surface points having normal vectors within a predefined range of vector space about the acceptor atom covalent bond vector(s). Geometric conditions necessary for the simultaneous hydrogen bonding interaction between both sites of functionally congruent hydrogen bonding site pairs, located on the individual proteins, are then tested on the basis of a transformation invariant parameterization of the site pair spatial and directional properties. Sterically acceptable conformations defined by interaction of functionally, spatially, and directionally compatible site pairs are then refined to a maximum contact of complementary contact surfaces using the simplex method for the angular search and correlation techniques for the translational search. The utility of the spatial and directional properties of hydrogen bonding donor and acceptor sites for the identification of candidate docking conformations is demonstrated by the reliable preliminary reduction of conformation space, the improved geometric ranking of the minimum RMS conformations of some complexes and the overall reduction of CPU time obtained.

Algorithms↗
PubMed1996

Probing native-like orientation of pigments in modified reaction centers from Rhodobacter sphaeroides R26 by linear dichroism.

Site-specific pigment modifications are useful to investigate structure-function relationships in photosynthesis. In reaction centers bearing modified (bacterio)pheophytins, changed electron transfer kinetics have been related to the changed redox potentials of the pigments introduced (Huber, H. et al. (1995) Chemical Physics, Special Issue, vol 197 (Hochstrasser, R.M. and Hofacker, G.L. eds.) pp. 297-305; [1]). In order to analyze potentially interfering structural changes induced in these reaction centers by the exchange procedure, in particular mispositioning or misorientation of the pigments, low-temperature linear dichroism spectra have been measured for reaction centers from Rhodobacter sphaeroides containing modified bacteriopheophytins and bacteriochlorophylls at the sites HA,B and BA,B, respectively. They show that all modified pigments are oriented similar to the native ones, and that they do not affect significantly the linear dichroism of the monomeric bacteriocholorophylls and bacteriopheophytins or of the primary donor.

Bacteriochlorophylls↗
PubMed1996

Diminished post-rest potentiation of contractile force in human dilated cardiomyopathy. Functional evidence for alterations in intracellular Ca2+ handling.

Post-rest contractile behavior of isolated myocardium indicates the capacity of the sarcoplasmic reticulum (SR) to store and release Ca2+. We investigated post-rest behavior in isolated muscle strips from nonfailing (NF) and endstage failing (dilated cardiomyopathy [DCM]) human hearts. At a basal stimulation frequency of 1 Hz, contractile parameters of the first twitch after increasing rest intervals (2-240 s) were evaluated. In NF (n = 9), steady state twitch tension was 13.7 +/- 1.8 mN/mm2. With increasing rest intervals, post-rest twitch tension continuously increased to maximally 29.9 +/- 4.1 mN/mm2 after 120s (P < 0.05) and to 26.7 +/- 4.5 mN after 240 s rest. In DCM (n = 22), basal twitch tension was 10.0 +/- 1.5 mN/mm2 and increased to maximally 13.6 +/- 2.2 mN/mm2 after 20 s rest (P < 0.05). With longer rest intervals, however, post-rest twitch tension continuously declined (rest decay) to 4.7 +/- 1.0 mN/mm2 at 240 s (P < 0.05). The rest-dependent changes in twitch tension were associated with parallel changes in intracellular Ca2- transients in NF and DCM (aequorin method). The relation between rest-induced changes in twitch tension and aequorin light emission was similar in NF and DCM, indicating preserved Ca(2-)-responsiveness of the myofilaments. Ryanodine (1 microM) completely abolished post-rest potentiation. Increasing basal stimulation frequency (2 Hz) augmented post-rest potentiation, but did not prevent rest decay after longer rest intervals in DCM. The altered post-rest behavior in failing human myocardium indicates disturbed intracellular Ca2- handling involving altered function of the SR.

Adult↗
PubMed1996

Skin wounds and severed nerves heal normally in mice lacking tenascin-C.

A large number of functions have been demonstrated for tenascin-C by antibody perturbation assays and in vitro cell culture experiments. However, these results contrast sharply with the lack of any apparent phenotype in mice with a genetic deletion of tenascin-C. A possible explanation for the lack of phenotype would be expression of some altered but functional tenascin-C in the mutant. We report the generation of an independent tenascin-C null mouse and conclude that the original tenascin-C knockout, which is genetically very similar to ours, is also a true null. As found previously, the absence of tenascin-C has no influence on development, adulthood, life span, and fecundity. We have studied in detail two models of wound healing. After axotomy, the regeneration of the sciatic nerve is not altered without tenascin-C. During healing of cutaneous wounds, deposition of collagen I, fibulin-2, and nidogen is identical in mutant and wild-type mice. In contrast. fibronectin appears diminished in wounds of tenascin-C-deficient mice. However, the lack of tenascin-C together with the reduced amount of fibronectin has no influence on the quality of the healing process.

Animals↗
PubMed1996

The complete nucleotide sequence of barley mild mosaic virus RNA1 and its relationship with other members of the Potyviridae.

The complete nucleotide sequence of RNA1 of a French barley mild mosaic bymovirus isolate has been determined. The molecule is composed of 7261 nucleotides and contains a single large open reading frame encoding a protein of 2258 amino acids with a calculated Mr of 256,375. Amino acid sequence comparison with poty- and rymoviruses reveals eight domains corresponding to the potyviral P3, 6K1, Cl, 6K2, Nla-VPg, Nla-Pro, Nlb and capsid proteins, respectively. Seven putative cleavage sites, similar to those mediated by potyvirus Nla proteinases, were identified. The presence of two, so far undescribed putative cleavage sites (6K2/Nla-VPg and Nla-VPg/Nla-Pro) in the polyproteins encoded by RNA1 of barley yellow mosaic virus and wheat spindle streak mosaic virus, was predicted. These data indicate that the bymovirus RNA1 fits the consensus potyviral genetic map downstream of the helper component gene.

Amino Acid Sequence↗
PubMed1996

[An outbreak of Streptococcus pyogenes infections in institutions for the mentally retarded in Greater Copenhagen 1995].

The largest reported outbreak of infections due to Streptococcus pyogenes, M-type 18, in recent years is described. Ninety persons at institutions for mentally retarded (73% residents) had infections due to the epidemic strain. Pharyngitis and scarlatina were the most common infections. Six patients died, five having a streptococcal toxic shock syndrome. During the outbreak an intensive surveillance was carried out together with improved infection control measures and prompt culturing of residents and employees before antimicrobial treatment. The primary outbreak was confined but a secondary outbreak could not be prevented. This was probably due to difficulties in implementing proper isolation precautions in this setting.

Adult↗
PubMed1996

Systematic isolation of circulating human peptides: the concept of peptide trapping.

The structural determination of circulating human peptides is essential to determine their correct posttranslationally processed form. Human hemofiltrate from patients with end stage renal disease is accessible in large quantities and is used as a source for the preparation of circulating peptides. After complete peptide extraction from hemofiltrate, a systematic separation with different chromatographic techniques is achieved. Single peptides are selected according to their mass and chromatographic elution position. Following chromatographic purification, amino acid sequence analysis is performed in combination with data base search. The identification of circulating peptides leads to numerous fragments resulting from cleavage of larger plasma proteins as well as to the discovery of new peptide hormones. The results obtained so far give insight into the degradation of plasma proteins such as fibrinogen, which results in the generation of fragments with biological activity themselves and in the identification of a novel cytokine HCC-1, the first member of beta-defensins in humans, hBD-1, and different peptides not present in any data base.

Amino Acid Sequence↗
PubMed1996

Acute renal failure following cardiac surgery is reverted by administration of Urodilatin (INN: Ularitide).

Acute renal failure (ARF) is a serious complication following cardiac surgery. This first controlled study was undertaken to verify, if Urodilatin (URO) infusion can revert incipient oliguric ARF after cardiac surgery. We conducted a randomized, double blind trial comparing 7 URO (20 ng/kg/min) with 7 placebo patients. Inclusion criterion was oliguria/anuria (< 0.5 ml/kg/hour) refractory to conventional treatment including administration of dopamine and furosemide. No patient in the URO treated group, but 6 patients in the placebo group had to be hemofiltered or hemodialyzed (p < 0.005) during the 7 day treatment period. In the URO group all 7 patients demonstrated a rapid recovery of diuresis after 2 - 8 hours of treatment that persisted throughout the treatment period. In contrast, placebo treated patients remained oliguric. Serum creatinine (SC) decreased in URO treated patients. No adverse effects were observed during URO administration. After termination of URO, 2 patients underwent hemodialysis for elevated blood urea nitrogen (BUN) values. In the postoperative follow-up period of 60 days, 4 out of 7 placebo treated patients died while still on hemodialysis. In contrast, all URO patients survived. URO is an effective drug to reverse oliguric ARF following cardiac surgery. Prolonged renal failure and renal replacement therapy can be avoided.

Acute Kidney Injury↗