Investigation of a catalytic zinc binding site in Escherichia coli L-threonine dehydrogenase by site-directed mutagenesis of cysteine-38

We studied block of the internal pore of the ROMK1 inward-rectifier K+ channel by Mg2+ and five quaternary ammoniums (tetramethylammonium, tetraethylammonium, tetrapropylammonium, tetrabutylammonium, and tetrapentylammonium). The apparent affinity of these blockers varied as a function of membrane voltage. As a consequence, the channel conducted K+ current more efficiently in the inward than the outward direction; i.e., inward rectification. Although the size of some monovalent quaternary ammoniums is rather large, the zdelta values (which measure voltage dependence of their binding to the pore) were near unity in symmetric 100 mM K+. Furthermore, we observed that not only the apparent affinities of the blockers themselves, but also their dependence on membrane voltage (or zdelta), varied as a function of the concentration of extracellular K+. These results suggest that there is energetic coupling between the binding of blocking and permeating (K+) ions, and that the voltage dependence of channel blockade results, at least in part, from the movement of K+ ions in the electrical field. A further quantitative analysis of the results explains why the complex phenomenon of inward rectification depends on both membrane voltage and the equilibrium potential for K+.     

The transformation of acute viral hepatitis B into chronic

500 patients with hepatitis B have been followed up from the acute onset to long-term outcome. As for chronic transformation of the disease, at higher risk are patients with mild form, progredient run and inadequate immune response. Of the highest value for identification and prognostication was a dynamic quantitative control over the system HBeAg-anti-HBe providing separate prognosis of establishment of replicative or integrative variants of chronic hepatitis B. In progredient infection an early administration of reaferon in combination with thymogen is thought valid which in many patients is sufficient to prevent the disease transformation into a chronic form.     

Redistribution of Block Copolymer Chains between Mixed Micelles in Solution

The evolution of polymolecular micelles formed by two different poly(2-vinylpyridine)-polystyrene (PVP-PS) block copolymers dissolved in toluene is studied by means of transmission electron microscopy (TEM). The two PVP-PS diblock copolymers differ in composition, namely in the length of PVP block. Upon dissolution, a rapid formation of mixed polymolecular micelles takes place. As a result, the micellar size distribution observed is rather broad already at this initial stage. Due to the presence of two different diblock copolymers, the process of micellar growth involves not only the fusion of micelles but also the chain exchange between polymolecular micelles of different composition, which may slow the equilibration process. After a considerable aging time, the block copolymers seem to reach the equilibrium state, and an almost perfect bimodal size distribution is observed. According to the theoretical analysis given, both "pure" and "mixed" micelles constitute the micellar size distribution.     

Migration of the dominant pacemaker region in the rat sinoatrial node

"Early onset sarcoidosis" is a chronic granulomatous disease occurring in children younger than 5 years of age, and characterized by a classic symptom triad consisting of skin, eye and joint lesions, with on rare occasion pulmonary involvement. The disorder often goes unrecognized because of its rarity and, since polyarthritis and uveitis are the predominant symptoms, most of these children are misdiagnosed as having juvenile chronic arthritis (JCA). A child with erythema nodosum at 7 months of age, later diagnosed as JCA and definitively recognized as "early onset sarcoidosis" is reported. This case shows that, whenever possible, a biopsy showing the typical picture of sarcoid granulomas is crucial to distinguish these clinical conditions.     

Treatment planning for enhanced dynamic wedge with the CMS focus/Modulex treatment planning system

BACKGROUND: Visual disturbances after high altitude exposure were first reported in 1969. Later, the term "High Altitude Retinal Hemorrhage-HARH" has been used for the ensuing retinal hemorrhages and vascular engorgement. CASE REPORT: A 31-year-old Caucasian male presented to our outpatient department 1 week after climbing Mt. Gosainthan in the Himalayas. He had spent 25 days without oxygen supply above 5000 meters, with a maximum of 8046 meters. He now complained of glare and decreased vision in twilight. Visual acuity was 20/25 OD and 20/20 OS. Ophthalmoscopy revealed intraretinal hemorrhages and tortuosity of dilated arterioles and venoles. After 6 weeks of gradual improvement, visual acuity was 20/20 OD and 20/16 OS with normal visual fields. DISCUSSION: The hypoxia at high altitude causes increased retinal blood flow and blood volume possibly via autoregulatory mechanisms. Furthermore, retinal venous pressure can be increased by extreme physical exertion and Valsalva maneuvers during mountain climbing. A hypoxic retinal capillary bed exposed to increased retinal venous pressure predisposes to intraretinal hemorrhage. Retinal changes include marked increase of retinal vessel diameter with tortuosity of arterioles and venoles and hyperemia or edema of the optic disc. The intra- or preretinal hemorrhages often spare the macular area. These patients do not experience debilitating symptoms unless vitreous hemorrhage occurs. This may be potentially hazardous when the patient is still in the high mountains. Clinically, all these retinal changes are reversible within weeks. To prevent high altitude retinopathy, ascending slowly and use of supplemental oxygen is recommended.