Crystal structures of Staphylococcusaureus methionine aminopeptidase complexed with keto heterocycle and aminoketone inhibitors reveal the formation of a tetrahedral intermediate

High-resolution crystal structures of Staphylococcus aureus methionine aminopeptidase I in complex with various keto heterocycles and aminoketones were determined, and the intermolecular ligand interactions with the enzyme are reported. The compounds are effective inhibitors of the S. aureus enzyme because of the formation of an uncleavable tetrahedral intermediate upon binding. The electron densities unequivocally show the enzyme-catalyzed transition-state analogue mimicking that for amide bond hydrolysis of substrates.     

The relationship between axonal spike shape and functional modality in cutaneous C-fibres in the pig and rat

Axonal spike shape was examined in identified cutaneous C-fibres dissected from the saphenous nerves of anaesthetized pigs and rats, and was found to vary with functional class. In the pig, the action potential duration for heat nociceptor units (duration at half peak amplitude, 1.25 +/- 0.16 ms, mean +/- S.E.M., n=32) was significantly longer than the duration for polymodal nociceptive units (0.88 +/- 0.11 ms, n=32). Both classes of nociceptive C-fibre had action potentials of longer duration than the low-threshold mechanoreceptor units (0.49 +/- 0.04 ms, n=24) and the inexcitable C-fibres (0.56 +/- 0.06 ms, n=19). Undershoot durations were also longer in nociceptive than non-nociceptive C-fibres. In contrast, spike amplitudes were similar in all classes of C-afferent. In the rat, as in the pig, the polymodal nociceptor units had action potentials of longer duration (0.75 +/- 0.05 ms, n=73) than the mechanoreceptor units (0.60 +/- 0.01 ms, n=23). C-fibres identified as spontaneously active sympathetic efferent units had wider action potentials (main initial peak: 1.01 +/- 0.12 ms, n=22; undershoot: 4.1 +/- 1.23 ms, n=20) than the afferent C-fibres (main peak: 0.69 +/- 0.03 ms, n=130; undershoot: 1.4 +/- 0.09 ms, n=111). All rat C-fibre types had action potentials with main initial peaks of a similar height. However, cold thermoreceptor units had spikes with significantly smaller undershoots compared to nociceptive or inexcitable C-fibres. It is concluded that there are clear differences in axonal spike shape between the different functional classes of C-fibre and, in particular, that nociceptive C-afferents tend to have axonal action potentials of longer duration than non-nociceptive afferents. The ion channels responsible for the longer duration action potentials may provide a target for the development of highly selective analgesic drugs.     

Morphological and electrophysiological aspects of dissociated cultures of rat CNS

Rat central nervous system has been cultured up to 6 weeks after complete dissociation. Maturation of different cell types has been followed in the quasi monolayer by phase contrast microscopy. Dorsal root ganglion (DRG) neurones usually differed from central nervous system (CNS) neurones by their spherical shape accompanied by only one or two processes, exact identification of cell types, however, was usually only possible by combining morphology with electrophysiology. Scanning electron-microscopy revealed a more extensive arborization of neurites and a higher number of presumed synaptic structures in cultures after 2 weeks of culturing. Layers of ependymal cells were also found. The different cell types were further identified by determining their membrane properties. Glial cells had higher resting membrane potentials (-56 +/- 9.7 mV) than CNS neurones (-49 +/- 10.2 mV), while the membrane potential of DRG neurones lay in-between the two (-53 +/- 1.7 mV). The sequence for input resistance was: DRG neurones (30 +/- 9.3 M omega) greater than CNS neurones (18 +/- 10.5 M omega) greater than glial cells (9.3 +/- 5.2 M omega). In CNS neurones the input resistance is correlated with the membrane potential, which is not the case for glial cells. Action potentials of DRG neurones exhibited delayed repolarisation increasing the spike duration to three times that of CNS neurones.     

Presynaptic action of beta(4-chlorophenyl)-gaba.

Spinal presynaptic inhibition is thought to be mediated by γ-aminobutyric acid (GABA). Because of the relative impermeability of GABA through the blood-brain barrier, the GABA-derivative, β(4-chlorophenyl)-GABA (Lioresal), was used to investigate possible presynaptic function. In eight cats anesthetized with sodium pentobarbital the administration of Lioresal (1 mg/kg, iv) attenuated the dorsal root potential and dorsal root reflex. Both dorsal root potential and reflex are thought to reflect presynaptic inhibition. The decrease of the dorsal root potential was accompanied by a d-c shift of the potential between the dorsal root and the spinal cord. Using condition and test stimulation of the dorsal root, Lioresal attenuated the unconditioned ventral root reflex, but first increased the conditioned reflex before it finally diminished the conditioned ventral root reflex as well. These results suggest that Lioresal maximally depolarizes the afferent terminals, thereby blocking the dorsal root potential and dorsal root reflex as well as presynaptically inhibiting motoneuron reflexes. These data support the notion that the therapeutic use of Lioresal for the treatment of spasticity can be attributed to the presynaptic inhibitor mechanisms.     

Über die Wirkung von Morphin und einigen zentral-erregenden Stoffen auf den Miktionsreflex

Zusammenfassung An Katzen und Kaninchen wurde die Wirkung von Morphin, Strychnin, Cardiazol, Pikrotoxin und Pervitin auf den Miktionsreflex untersucht. Der Miktionsreflex wird durch Morphin schon in kleinen Gaben, durch die zentralerregenden Pharmaka in krampferzeugender Dosierung, unterdrückt.Decerebrierung in verschiedenen Höhen verändert diese Wirkung nicht.Mit 8 Textabbildungen     

Effect of ouabain and potassium-free solution on mammalian thermosensitive afferents in vitro

Summary Studies have been performed on the afferent fibers innervating the scrotal skin of the rat to test the hypothesis that the generator potential mechanism underlying cold thermosensitivity of these afferent fibers is an electrogenic sodium pump. In these experiments a pudendal nerve-scrotal skin preparation was isolated from the animal and, maintained in oxygenated mammalian Ringer's where composition could be varied and drugs added. Application of ouabain resulted in an increase in the discharge of cold sensitive afferent fibers which was more pronounced at 38–41° C than at temperatures below 30° C. In most of the cases transient accelerations on cooling were reduced, but often a transient response to warming appeared. The effects of ouabain administration were reversible. Removal of extracellular K at 35° C resulted in an increased discharge of cold sensitive afferents. This observation is consistent with the effects of ouabain, since removal of extracellular K also blocks Na transport. The generator potential mechanism underlying cold sensitivity of these afferent fibers appears to be an electrogenic Na pump.     

Dying at home or in the hospital? An observational study in German general practice

Background Although determinants of place of death have been investigated in several studies, there is a lack of knowledge on factors associated with dying at home from the general practice perspective.

Objectives To identify factors associated with dying at home for patients in German general practice.

Methods In a retrospective study, general practitioners of 30 general practices were asked to provide data for all patients aged 18 years or older who died within the last 12 months, using a self-developed questionnaire. ‘Dying in hospital’ was defined as dying in hospital or hospice and ‘dying at home’ as dying at one’s usual residence including the nursing home. Multiple logistic regression analyses were used to determine factors associated with ‘dying at home’; odds ratios (ORs) and their 95% confidence intervals (CI) were calculated as measures of effect size.

Results Of 439 deceased patients, 52.2% died at home, and 47.8% died in hospital or hospice. Determinants for dying at home were patients’ care in the last 48 hours of life by family members (OR: 7.8, 95% CI: 3.4–18.0), by general practitioners (GPs) (OR: 7.3, 4.2–12.9) and living in a nursing home (OR: 3.8, 1.7–8.3). In the adjusted model, low comorbidity was positively associated (OR: 3.2, 1.4–7.0), and low functional health status (Karnofsky performance status) was negatively associated with dying at home (OR: 0.3, 0.1–0.7).

Conclusion Apart from patient-related factors such as comorbidity and health status, care by family members and GPs respectively, were determinants of dying at home.