Spectroscopic and computational studies of reduction of the metal versus the tetrapyrrole ring of coenzyme F430 from methyl-coenzyme M reductase

Methyl-coenzyme M reductase (MCR) catalyzes the final step in methane biosynthesis by methanogenic archaea and contains a redox-active nickel tetrahydrocorphin, coenzyme F430, at its active site. Spectroscopic and computational methods have been used to study a novel form of the coenzyme, called F330, which is obtained by reducing F430 with sodium borohydride (NaBH4). F330 exhibits a prominent absorption peak at 330 nm, which is blue shifted by 100 nm relative to F430. Mass spectrometric studies demonstrate that the tetrapyrrole ring in F330 has undergone reduction, on the basis of the incorporation of protium (or deuterium), upon treatment of F430 with NaBH4 (or NaBD4). One- and two-dimensional NMR studies show that the site of reduction is the exocyclic ketone group of the tetrahydrocorphin. Resonance Raman studies indicate that elimination of this pi-bond increases the overall pi-bond order in the conjugative framework. X-ray absorption, magnetic circular dichroism, and computational results show that F330 contains low-spin Ni(II). Thus, conversion of F430 to F330 reduces the hydrocorphin ring but not the metal. Conversely, reduction of F430 with Ti(III) citrate to generate F380 (corresponding to the active MCR(red1) state) reduces the Ni(II) to Ni(I) but does not reduce the tetrapyrrole ring system, which is consistent with other studies [Piskorski, R., and Jaun, B. (2003) J. Am. Chem. Soc. 125, 13120-13125; Craft, J. L., et al. (2004) J. Biol. Inorg. Chem. 9, 77-89]. The distinct origins of the absorption band shifts associated with the formation of F330 and F380 are discussed within the framework of our computational results. These studies on the nature of the product(s) of reduction of F430 are of interest in the context of the mechanism of methane formation by MCR and in relation to the chemistry of hydroporphinoid systems in general. The spectroscopic and time-dependent DFT calculations add important insight into the electronic structure of the nickel hydrocorphinate in its Ni(II) and Ni(I) valence states.

Leitlinien

Now more than ever physicians need effective management of the constantly increasing flood of medical information. The authors discuss possibilities for developing clinical guidelines as a core element of this information management and the requirements of these possibilities. The development of clinical guidelines is a process also suitable for involving patient and consumer expertise in health care. Models of involving patients are described and how these processes can build an important base for shared decision making of physicians and patients.

Cellular neural networks (CNN) with linear weight functions for a prediction of epileptic seizures

In this paper, we present a novel approach to the prediction of epileptic seizures using boolean CNN with linear weight functions. Three different binary pattern occurrence behaviours will be discussed and analysed for several invasive recordings of brain electrical activity. Furthermore analogic binary pattern detection algorithms will be introduced for a possible prediction of epileptic seizures.

Palliative Care f�r Patienten mit fortgeschrittener Demenz: Values Based statt Evidence Based Practice

For the treatment of patients with advanced dementia, we could not find any evidence based guidelines to help in decision making. Individual values and expected quality of life must be the leading goals of any intervention. Symptom control and relieving suffering are core values of palliative care, but the recognition of discomfort needs qualified assessment skills. Pain assessment with common tools like the VAS fails in patients with cognitive impairment and inability to communicate; instruments like Doloplus and ECPA can be helpful to assess behavioral changes as expression of pain. The treatment of acute and chronic pain in advanced dementia is still not sufficient and needs improvement. Oral feeding in advanced dementia becomes more and more difficult. No randomized controlled study has found evidence that tube feeding will reduce the risk of aspiration or prolong life expectancy. Eating may be the only meaningful activity that remains for the patient; artificial feeding cannot serve the same function. All final complications, like pneumonia, call for a decision making process. Those who care for and care about these patients must make decisions. The feelings of the family have to be considered, but the probable will of the patient, his dignity and quality of life must not be overridden.

Do short courses in evidence based medicine improve knowledge and skills? Validation of Berlin questionnaire and before and after study of courses in evidence based medicine

OBJECTIVE

To develop and validate an instrument for measuring knowledge and skills in evidence based medicine and to investigate whether short courses in evidence based medicine lead to a meaningful increase in knowledge and skills.

DESIGN

Development and validation of an assessment instrument and before and after study.

SETTING

Various postgraduate short courses in evidence based medicine in Germany.

PARTICIPANTS

The instrument was validated with experts in evidence based medicine, postgraduate doctors, and medical students. The effect of courses was assessed by postgraduate doctors from medical and surgical backgrounds.

INTERVENTION

Intensive 3 day courses in evidence based medicine delivered through tutor facilitated small groups.

MAIN OUTCOME MEASURE

Increase in knowledge and skills.

RESULTS

The questionnaire distinguished reliably between groups with different expertise in evidence based medicine. Experts attained a threefold higher average score than students. Postgraduates who had not attended a course performed better than students but significantly worse than experts. Knowledge and skills in evidence based medicine increased after the course by 57% (mean score before course 6.3 (SD 2.9) v 9.9 (SD 2.8), P<0.001). No difference was found among experts or students in absence of an intervention.

CONCLUSIONS

The instrument reliably assessed knowledge and skills in evidence based medicine. An intensive 3 day course in evidence based medicine led to a significant increase in knowledge and skills.

(22)Ne(alpha,n)(25)Mg: the key neutron source in massive stars

The excitation function of the reaction (22)Ne(alpha,n)(25)Mg, the key neutron source in the astrophysical s process in massive stars, has been determined from threshold at E(alpha) = 570 up to 1450 keV with an experimental sensitivity of 10(-11) b. For all resonances in this energy range new resonance parameters have been measured. For a possible resonance at about 635 keV a new upper limit omega gamma < 60 neV for the strength was obtained. Based on the new data, improved reaction rates were calculated as a function of temperature. The new uncertainty limits are considerably smaller than in previous determinations, ruling out the large enhancement factors, up to 500, assumed in some stellar model calculations.

[Development of quality assurance criteria for continuing education in evidence-based medicine]

OBJECTIVE

To develop a set of core contents for teaching evidence-based medicine (EBM).

METHOD

Description of basic principles from clinical epidemiology, medical statistics and literature search essential for health care practitioners to perform critical appraisal of the medical literature. Based on textbooks for EBM and clinical epidemiology and guided by the EBM courses at McMaster university and the Oxford Centre for EBM, core contents were defined. Decision on inclusion was made by consensus.

RESULTS

The core contents for the Berlin curriculum in EBM covers 3 areas: 1. General information on the methods of experimental and observational clinical studies, principles of EMB, basic statistical concepts, and literature search. 2. Tools for critical appraisal of primary studies required for medical decision making: therapy, diagnosis, prognosis, and harm. 3. Evidence-based summary reports: meta-analysis and guidelines.

CONCLUSIONS

The contents of EBM can be precisely defined. They are transparent, explicit and communicable and present a reproducible basis for the different forms of teaching EBM.

12C(alpha,gamma)16O: the key reaction in stellar nucleosynthesis

The angular distributions of gamma rays from the 12C(alpha,gamma)16O reaction have been measured at 20 energy points in the energy range E(cm) = 0.95 to 2.8 MeV. The sensitivity of the present experiment compared to previous direct investigations was raised by 1-2 orders of magnitude, by using an array of highly efficient ( 100%) Ge detectors shielded actively with BGOs, as well as high beam currents of up to 500 microA that were provided by the Stuttgart Dynamitron accelerator. The S(E1) and S(E2) factors deduced from the gamma angular distributions have been extrapolated to the range of helium burning temperatures applying the R-matrix method, which yielded S(300)(E1) = (76+/-20) keV b and S(300)(E2) = (85+/-30) keV b.

[Severely injured patients after the initial phase--vegetative state or remaining cognitive functions?]

BACKGROUND

We wanted to quantify improvements in the subacute rehabilitation phase in patients with severe brain injuries classified as vegetative or minimal brain consciousness.

MATERIAL AND METHODS

Five patients were studied during a 12 months period using a method called Coma Recovery Scale (CRS) as described by Giacino et al. (1991). The parameters measured included visual and hearing functions, motor functioning, oromotor/verbal function, communication, and arousal. The observations of the patients and commandos given were standardised in a manual, and the responses achieved from the patients were recorded according to a scale for each parameter.

RESULTS

This procedure for measuring closely the progress over time in these severely brain injured patients, was used for planning a realistic rehabilitation program. It was found to be very practical in communication with relatives of the patients and with the other therapists involved.

INTERPRETATION

By decomposing the cognitive functions by this method using all the available possibilities for inputs, even minimal improvement in the cognitive functions mentioned could be uncovered and recorded.

Studies of symptoms in primary care

Publications on the frequency of defined symptoms in the practice setting, underlying conditions and prognosis have been rare in the past. Also, studies addressing these questions have suffered from several methodological problems. We therefore developed criteria to help investigators improve the quality of study design, implementation and publication. Studies evaluating symptoms in practice can make an important contribution to a more rational approach to diagnostic decision making especially in primary care.

A primate model for discordant pig to primate kidney xenotransplantation without hyperacute graft rejection

Organs transplanted between phylogenetically disparate species, such as from the pig into the primate, are subject to intragraft deposition of preformed recipient immunoglobulin M (IgM) antibodies with subsequent complement activation finally leading to complete and rapid destruction of the xenograft (hyperacute graft rejection, HAR). Current therapeutic strategies for abrogation of HAR include pretransplant antibody absorption by specific or nonspecific extracorporeal column perfusion, ex vivo donor organ perfusion, the administration of substances interfering with complement activation, or even the genetic alteration of the donor. Here, in the pig to cynomolgus monkey species combination, we are describing an experimental model for abrogation of HAR by using large, relative to the recipient weight, oversized donor kidneys as xenotransplants. Porcine kidney xenotransplantation (n = 15) was performed using large white pigs of different weights and ages as organ donors and cynomolgus monkeys as recipients. In grafts with an organ weight below 50 g (20 to 48 g, median 25 g), primary nonfunction (PNF) of the porcine kidney was observed in 11 out of 12 cases and complete HAR in 5 out of 12 experiments. In contrast, none of three grafts with a donor organ weight >70 g showed signs of HAR or PNF. In one animal, a second porcine kidney from the same donor (23 g) was successfully transplanted immediately after HAR and subsequent removal of a first porcine kidney (20 g). By using appropriate immunohistochemistry stainings of reperfusion biopsies, profound deposition of recipient natural antibodies in both small and large xenografts was shown, with only scarce deposition of C3 and C5b-9 in the latter, indicating only incomplete intragraft activation of the complement cascade in these organs. Intraoperative cardiac output (CO) measurements performed in 7 experiments demonstrated a 20 to 50% decrease in CO following reperfusion in 6 out of 7 grafts irrespective of the donor organ weight. The intraoperative decrease in CO was not associated with perioperative morbidity or mortality. The use of oversized doner kidneys can enable the study of a variety of immunologic and physiologic sequela beyond HAR associated with life-supporting discordant primate kidney transplantation.

Practice variations in the evaluation of adult candidates for cadaveric kidney transplantation: a survey of the European Transplant Centers

BACKGROUND

This survey was conducted to investigate similarities and differences in the diagnostic evaluation of adult candidates for cadaveric renal transplantation and the criteria for acceptance to the cadaveric renal transplant waiting-list in the European transplant centers.

METHODS

A questionnaire listing 45 diagnostic procedures (consultations of 9 specialties, 18 imaging techniques and 18 laboratory investigations), 45 medical conditions constituting possible reasons for exclusion from renal transplantation, and 10 properties characterizing the responding transplant center was sent to 214 European transplant centers.

RESULTS

A completed questionnaire was returned by 154 of 214 centers (72%). Significant disagreement (P<0.001) exists about the necessity of 28 of the 45 surveyed diagnostic procedures and about the acceptability of transplant candidates for 15 of the 45 surveyed medical conditions. The influence of center characteristics on the observed practice variations was examined by multinomial logistic regression (factors: Center size, waiting-list pressure, responsibility for organizing the diagnostic work-up, status of transplant center, responsibility for decision about acceptance of candidates and geographic location of center): In 13 of 28 controversial diagnostic procedures, geographic location of the centers turned out to be the only significant determining factor (P<0.001), whereas the dissent about medical conditions is not influenced significantly by the analyzed factors.

CONCLUSION

The detected significant practice variations in the evaluation of renal transplant candidates may either indicate where scientific evidence is missing and more clinical research is needed or where the existing evidence has not been adequately disseminated and convincing guidelines should be established.

Effect of ethanol on dynamic visual acuity during vertical body oscillation in healthy volunteers

Visual orientation is the most important sensory input during locomotion (e.g. walking, driving a car, riding a bicycle). We investigated dynamic visual acuity (DVA) during vertical body-oscillations (amplitude 5 cm; frequency 1.5 Hz) in 12 healthy subjects before and twice after ethanol consumption. During oscillation, vertical eye movements were recorded under two test conditions: with eyes closed (EC) and during DVA testing. A significant increase in vertical eye-amplitude after ethanol ingestion occurred only during EC tests, as a possible sign of vestibular hyperreaction. During vestibular stimulation alone (EC), ethanol did not affect the phase shift between stimulus and eye movements. However, when the subjects were given an additional visual stimulus (DVA), the post-alcohol phase shift rose significantly. Surprisingly, the post-alcohol phase shift values for the two test conditions showed no significant differences. After ethanol ingestion we found no changes in static visual acuity but a significant loss of DVA. Volunteers with a change of DVA threshold (DVAT) showed significantly (P = 0.004) higher post-alcoholic changes in the phase shift. In summary, low doses of ethanol disturbed the visually guided oculomotor response during fixation of an earth-fixed target while the observer was subject to linear vertical acceleration. This effect led to an increasing delay between the beginning of body and eye movements. The consequence was an increasing phase shift and thus a decrease in DVA during whole-body oscillation which was comparable to movements during human locomotion.

The localization of an imaginary target under the influence of caloric vestibular stimulation in healthy adults

It is well known that fixation of an imaginary target (IT) can influence the vestibulo-ocular reflex, but reports on the effect of peripheral vestibular stimulation on the localization of an IT are still lacking. In a prospective study, errors in pointing towards an IT without and after cold caloric vestibular stimulation (VS) were investigated in 24 right-handed volunteers with the head tilted backwards by 60 degrees. After the stationary target had been extinguished for 120 s each subject had to point towards the target position as remembered in darkness. The vestibular response was recorded by electronystagmography. Without VS 73% of the volunteers showed a systematic horizontal pointing error towards the right side. VS led to an increased horizontal pointing error in the direction of the slow phase of the induced nystagmus and the degree of deviation showed a significant (P = 0.001) positive correlation (r = 0.32) with the amplitude of the calorically induced nystagmus. In summary, an IT is not merely a useful visual stimulus for influencing the vestibulo-ocular reflex during linear and angular acceleration. A peripheral vestibular stimulation is itself able to change the position of an IT significantly and the extent of deviation shows a significant correlation with the amplitude of the evoked nystagmus.

Dynamic visual acuity during linear acceleration along the inter-aural axis

We investigated visual-vestibular interactions during linear acceleration along the inter-aural axis. Eighteen healthy volunteers and two patients with central neurological diseases were subjected to transaural linear acceleration in the direction of gravity force (frequency: 0.5-1.5 Hz; amplitude: 5 cm). During linear acceleration, eye movements were recorded under three test conditions: eyes closed (EC), while staring at an imaginary target (IT) and during the testing of dynamic visual acuity (DVA). As parameters of evaluation we used the amplitude of horizontal eye movements, phase shift and the decrease of DVA threshold (DVAT). Under all test conditions, eye amplitude increased with rising stimulus frequency and exceeded, especially in the higher frequency range, a hypothetically calculated eye amplitude for smooth pursuit. The combination of a visual and vestibular input (DVA and IT) led to a better compensation (lower phase shift) than under vestibular stimulation alone (EC). Eye movements during low-frequency stimulation depended more on the visual system while responses in the higher frequency range were mainly triggered by the otolith organ. At 1.5 Hz the compensatory function of the visual-vestibular system was limited (rising phase shift) and DVAT decreased even in a significant number of healthy subjects. Patients with diseases of the central nervous system showed a higher phase shift and thus a stronger decrease of DVAT (two levels) already at a stimulus frequency of 1.25 Hz.