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C Heide

Publications and source records attributed to C Heide.

8 recordsLinked to original sources

Spin currents in magnetic films.

Spin currents injected into magnetic thin films may noticeably change the magnetization of the films. To describe this effect, exchange coupled Landau-Lifshitz equations for the local magnetization and the spin-polarized charge carriers are combined with transport equations for charge and spin currents. For steady state transport one obtains two different instability conditions. Both conditions are supported by recent experimental data on current induced magnetization reversal and spin-wave excitations. No second ferromagnetic layer is needed for excitations due to spin transfer.

Journal Article↗

Purine N7 groups that are crucial to the interaction of Escherichia coli rnase P RNA with tRNA.

We have detected by nucleotide analog interference mapping (NAIM) purine N7 functional groups in Escherichia coli RNase P RNA that are important for tRNA binding under moderate salt conditions (0.1 M Mg2+, 0.1 M NH4+). The majority of identified positions represent highly or universally conserved nucleotides. Our assay system allowed us, for the first time, to identify c7-deaza interference effects at two G residues (G292, G306). Several c7-deazaadenine interference effects (A62, A65, A136, A249, A334, A351) have also been identified in other studies performed at very different salt concentrations, either selecting for substrate binding in the presence of 0.025 M Ca2+ and 1 M NH4+ or self-cleavage of a ptRNA-RNase P RNA conjugate in the presence of 3 M NH4+ or Na+. This indicates that these N7 functional groups play a key role in the structural organization of ribozyme-substrate and -product complexes. We further observed that a c7-deaza modification at A76 of tRNA interferes with tRNA binding to and ptRNA processing by E. coli RNase P RNA. This finding combined with the strong c7-deaza interference at G292 of RNase P RNA supports a model in which substrate and product binding to E. coli RNase P RNA involves the formation of intermolecular base triples (A258-G292-C75 and G291-G259-A76).

Base Sequence↗

Distinct modes of mature and precursor tRNA binding to Escherichia coli RNase P RNA revealed by NAIM analyses.

We have analyzed by nucleotide analog interference mapping (NAIM) pools of precursor or mature tRNA molecules, carrying a low level of Rp-RMPalphaS (R = A, G, I) or Rp-c7-deaza-RMPalphaS (R = A, G) modifications, to identify functional groups that contribute to the specific interaction with and processing efficiency by Escherichia coli RNase P RNA. The majority of interferences were found in the acceptor stem, T arm, and D arm, including the strongest effects observed at positions G19, G53, A58, and G71. In some cases (interferences at G5, G18, and G71), the affected functional groups are candidates for direct contacts with RNase P RNA. Several modifications disrupt intramolecular tertiary contacts known to stabilize the authentic tRNA fold. Such indirect interference effects were informative as well, because they allowed us to compare the structural constraints required for ptRNA processing versus product binding. Our ptRNA processing and mature tRNA binding NAIM analyses revealed overlapping but nonidentical patterns of interference effects, suggesting that substrate binding and cleavage involves binding modes or conformational states distinct from the binding mode of mature tRNA, the product of the reaction.

Anticodon↗

Guanosine 2-NH2 groups of Escherichia coli RNase P RNA involved in intramolecular tertiary contacts and direct interactions with tRNA.

We have identified by nucleotide analog interference mapping (NAIM) exocyclic NH2 groups of guanosines in RNase P RNA from Escherichia coli that are important for tRNA binding. The majority of affected guanosines represent phylogenetically conserved nucleotides. Several sites of interference could be assigned to direct contacts with the tRNA moiety, whereas others were interpreted as reflecting indirect effects on tRNA binding due to the disruption of tertiary contacts within the catalytic RNA. Our results support the involvement of the 2-NH2 groups of G292/G293 in pairing with C74 and C75 of tRNA CCA-termini, as well as formation of two consecutive base triples involving C75 and A76 of CCA-ends interacting with G292/A258 and G291/G259, respectively. Moreover, we present first biochemical evidence for two tertiary contacts (L18/P8 and L8/P4) within the catalytic RNA, whose formation has been postulated previously on the basis of phylogenetic comparative analyses. The tRNA binding interference data obtained in this and our previous studies are consistent with the formation of a consecutive nucleotide triple and quadruple between the tetraloop L18 and helix P8. Formation of the nucleotide triple (G316 and A94:U104 in wild-type E. coli RNase P RNA) is also supported by mutational analysis. For the mutant RNase P RNA carrying a G94:C104 double mutation, an additional G316-to-A mutation resulted in a restoration of binding affinity for mature and precursor tRNA.

Base Sequence↗

The inflammatory response system and the availability of plasma tryptophan in patients with primary sleep disorders and major depression.

BACKGROUND: It is now well established that major depression is accompanied by an immune-inflammatory system response and that indicators of the latter are inversely correlated with lower availability of plasma tryptophan in depression. Inflammation and infection can alter sleep architecture, whereas sleep disturbances can impair immune functions. AIMS AND METHODS: The aims of the present study were to examine: (i) immune-inflammatory markers, i.e. serum interleukin-6 (IL-6), IL-8, IL-6 receptor (IL-6R), IL-1R antagonist (IL-1RA), gp130, and prostaglandin E2 (PGE2) production by mitogen-stimulated whole blood and the availability of plasma tryptophan in patients with primary sleep disorders, major depression and healthy volunteers; and (ii) the relationships between the availability of tryptophan and indicators of the immune-inflammatory response system. RESULTS: Mitogen-stimulated release of PGE2, and serum IL-6 and IL-8, were significantly increased in both depressed and sleep disordered patients compared to normal controls. Serum IL-1RA was significantly higher in depressed patients than in normal controls. Patients with depression and sleep disorders had a significantly lower availability of tryptophan than normal controls. There were significant and inverse relationships between the availability of plasma tryptophan and serum IL-1RA, IL-6 and IL-8. CONCLUSIONS: The results suggest that (i) there is an activation of the immune-inflammatory response system in primary sleep disorders and depression; and (ii) the decreased availability of plasma tryptophan may be related to the inflammatory system response.

Adult↗

[Early detection of TUR(transurethral resection) syndrome--ethanol measurement in ventilated patients].

A major complication of transurethral resection of the prostate (TURP) is the excessive absorption of irrigation solution resulting in hypervolemia and dilutional hyponatremia. Marking the irrigation fluid with ethanol is a method for the early detection of fluid absorption. Currently this method is being used in spontaneously breathing patients undergoing regional anaesthesia. The goal of this study was to determine whether this method is also reliable for patients undergoing general anaesthesia. Fifty-nine patients underwent TURP in either spinal anaesthesia (SPA), or general anaesthesia with semi-open (ITNO) and semi-closed (ITNC) systems. Plasma alcohol concentrations ([Eth]p), exhaled ethanol ([Eth]e), plasma sodium concentration ([Na+]), and central venous pressure (CVP) were measured. The irrigation fluid contained ethanol in an concentration of approx. 1%. We assumed that significant fluid absorption took place when [Eth]p exceeded 0.1/1000. Measurements were performed immediately prior to and during surgery at 10-minute intervals. [Eth]p correlated directly with [Eth]e for both forms of anaesthesia. [Eth]p and [Na+] correlated inversely both for SPA and ITNC. Changes in [Eth]p did not parallel changes in CVP. Clinically relevant episodes of fluid absorption were accompanied by the detection of exhaled ethanol in all groups. We conclude that measuring exhaled ethanol is a minimal invasive monitoring technique that allows the detection of significant fluid absorption in both spontaneously breathing as well as ventilated patients with sufficient sensitivity. The ethanol levels are not predictive of the sodium concentration both in SPA and general anaesthesia. Thus, additional determinations of [Na+] is recommended whenever [Eth]e exceeds 0.2/1000.

Anesthesia, General↗

[A comparative study of intravenous opioid analgesia. Sufentanil and alfentanil for extracorporeal shock-wave lithotripsy in urologic patients].

UNLABELLED: Extracorporeal shock-wave lithotripsy (ESWL) is the method of choice for the treatment of solitary stones in the kidney or ureter. Early lithotripters required prolonged immobility of the patient and caused considerable pain, necessitating general or epidural anaesthesia during the procedure. Modern lithotripters are quicker, but still require analgesia. Intravenous opioids are currently the drugs in favour. The opioids most commonly used are fentanyl and its shorter-acting analogue, alfentanil. The latter has a more rapid onset and, because of its reduced lipid solubility, is less cumulative. Sufentanil is a new opioid that is also of the phenylpiperidone group and has been recently licensed and introduced in Germany. Its pharmacokinetic and pharmacodynamic properties suggest an intermediate duration of action, high analgesic potency, and cardiovascular stability with diminished respiratory depression. In this prospective double-blind study, the effects of alfentanil and sufentanil on cardiovascular and respiratory parameters, the quality of analgesia, degree of sedation and the number and type of side-effects were compared. PATIENTS AND METHODS: After giving informed consent and with the approval of the hospital ethics committee, 62 patients (ASA I or II) were investigated. They were randomly allocated to two groups, either receiving sufentanil (n = 32) or alfentanil (n = 30) during ESWL. No premedication was given. Excluded were patients with pain prior to treatment, patients treated with a spasmolytic or analgesic drug and those who had undergone ESWL within the last 6 months. The loading dose was given as a 5-min infusion to each group. The heart rate, systolic and diastolic blood pressure, percutaneous oxygen saturation (SpO2), and the transcutaneous capillary carbon dioxide tension (PicCO2) were recorded prior to the procedure (i.e. before administration of opioid), after 1000 and after 2000 shock waves and then 1 and 2 h after the end of lithotripsy. After 1000 and 2000 shock waves, and 1 an 2 h after the treatment, the patients were asked to express their degree of tiredness and pain on a visual analogue scale (VAS). The occurrence of side-effects such as nausea, vomiting, pruritus or other unpleasant sensations were noted by an anaesthesia nurse. Simultaneously, the anaesthetist recorded his/her impression of the patient's tiredness and degree of pain, both by using the VAS. He was not allowed to question the patient, nor was he aware of the patient's own scores. At the end of the observation period both the patient and the anaesthetist related their overall satisfaction with the anaesthetic procedure, again by using the VAS. Data were analysed with the Mann-Whitney-U for comparisons between groups and with the Wilcoxon test within each group. The side-effects were analysed with the Chi-square test. RESULTS: The systolic and diastolic blood pressure remained stable in both groups during and after treatment. The mean heart rate was different between the two groups at the beginning, and after the end of the treatment it dropped in both groups, but no significant difference was seen between groups. The PicCO2 rose from an initial mean of 36.8 mm Hg to a maximum of 44.6 mm Hg after 1000 shock waves in the sufentanil group, and from 37.8 mm Hg to 46.0 mm Hg after 2000 shock waves in the alfentanil group. The differences were significant within groups until 1 h after the end of the treatment, but there was no significant difference between groups. The oxygen saturation SpO2 dropped slightly in both groups. The differences were not significant between groups. In the alfentanil group, one patient had a maximum carbon dioxide tension of 83 mm Hg after 2000 shock waves, whereas in the sufentanil treated group the oxygen saturation fell to 72% in one case. (ABSTRACT TRUNCATED)

Alfentanil↗

Characterisation of the solution conformation of a cyclic RGD peptide analogue by NMR spectroscopy allied with a genetic algorithm approach and constrained molecular dynamics.

The solution conformation of a cyclic RGD peptide analogue, cyclo-(S,S)-2-mercaptobenzoate-arginine-glycine-aspartate-2-mer captoanilide, has been determined via two independent approaches for the searching of conformational space and identification of conformations consistent with NMR and CD spectroscopic data: (i) the use of a binary genetic algorithm and (ii) a molecular dynamics simulation. Inter-proton distances were obtained via analysis of cross-peak volumes from a two-dimensional ROESY NMR spectroscopy experiment at 600 MHz and were used as constraints for the computational calculations. The mercaptoanilide amide proton resonance chemical shift had a very small temperature coefficient, indicating that this proton was hydrogen-bonded. Circular dichroism data showed that, in solution, the torsion angle about the disulfide bond was negative, consistent with one of the distinct conformations around this bond in the 200 ps molecular dynamics simulation. The backbone conformations of the structures resulting from the two different approaches were very similar.

Amides↗