Noble gas radionuclides in RBMK-1500-type reactor.

The presence of noble gas and other short-lived radionuclides in air borne effluents from RBMK-1500-type reactor has been investigated using experimental and theoretical instrumentation for detection purposes. Activity concentrations of (85m)Kr, (87)Kr, (88)Kr, (135m)Xe, (135)Xe, (133)Xe and (41)Ar were measured in air emissions from Ignalina NPP using a special method and special equipment. Theoretical detection of reactor-borne radionuclides and investigation of their behaviour in a nuclear fuel during operation of nuclear reactor was performed using an analytical model based on reactor physics. An innovative method for the estimation of noble gas flow time from the defective nuclear fuel element through the ventilation stack of NPP to the atmosphere based on comparison of the experimentally and theoretically evaluated activity ratios of (88)Kr/(85m)Kr; (135)Xe/(133)Xe has been proposed. The estimated flow time of noble gas provides an excellent possibility to obtain modelling-based information about the qualitative and quantitative content of atmospheric releases from NPP.     

Anatomical study of the neural ganglionated plexus in the canine right atrium: Implications for selective denervation and electrophysiology of the sinoatrial node in dog

The aim of the present study was to elucidate the topography and architecture of the intrinsic neural plexus (INP) in the canine right atrium because of its importance for selective denervation of the sinoatrial node (SAN). The morphology of the intrinsic INP was revealed by a histochemical method for acetylcholinesterase in whole hearts of 36 mongrel dogs and examined by stereoscopic, contact, and electron microscopes. At the hilum of the heart, nerves forming a right atrial INP were detected in five sites adjacent to the right superior pulmonary veins and superior vena cava (SVC). Nerves entered the epicardium and formed a INP, the ganglia of which, as a wide ganglionated field, were continuously distributed on the sides of the root of the SVC (RSVC). The epicardiac ganglia located on the RSVC were differentially involved in the innervation of the sinoatrial node, as revealed by epicardiac nerves emanating from its lower ganglia that proceed also into the atrial walls and right auricle. The INP on the RSVC (INP‐RSVC) varied from animal to animal and in relation to the age of the animal. The INP‐RSVC of juvenile dogs contained more small ganglia than that of adult animals. Generally, the canine INP‐RSVC included 434 ± 29 small, 17 ± 4 medium‐sized, and 3 ± 1 large epicardiac ganglia that contained an estimated 44,700, 6,400, and 2,800 neurons, respectively. Therefore, the canine right atrium, including the SAN, may be innervated by more than 54,000 intracardiac neurons residing mostly in the INP‐RSVC. In conclusion, the present study indicates that epicardiac ganglia that project to the SA‐node are distributed more widely and are more abundant than was previously thought. Therefore, both selective and total denervation of the canine SAN should involve the whole region of the RSVC containing the INP‐RSVC. Anat Rec 255:271–294, 1999. © 1999 Wiley‐Liss, Inc.     

Kutznerides 1-4, depsipeptides from the actinomycete Kutzneria sp. 744 inhabiting mycorrhizal roots of Picea abies seedlings

Bioassay-guided fractionation of culture supernatants of the actinomycete Kutzneria sp. 744 resulted in the isolation of four new depsipeptides (1-4). Structure analysis revealed the general structure: cyclo[2-(1-methylcyclopropyl)-D-glycine-(2S,3aR,8aS)-6,7-dichloro-3a-hydroxy-1,2,3,3a,8,8a-hexahydropyrrolo[2,3-b]indole-2-carboxylic acid-3-hydroxy-D-glutamic acid-O-methyl-L-serine-L-piperazic acid-(S)-2-hydroxy-3,3-dimethylbutanoic acid]. The 3-hydroxy-d-glutamic acid was present as its threo-isomer in 1 and 2 and as its erythro-isomer in 3 and 4. The piperazic acid was modified to its (R)-4-chloro analogue in 2 and to its C-5/N unsaturated analogue in 4. Compounds 1-4 displayed moderate spore germination inhibiting activity against several common root-rotting fungi.     

Compression, adaptation and efferent control in a revised outer hair cell functional model

In the cochlea of the inner ear, outer hair cells (OHC) together with the local passive structures of the tectorial and basilar membranes comprise non-linear resonance circuits with the local and central (afferent-efferent) feedback. The characteristics of these circuits and their control possibilities depend on the mechanomotility of the OHC. The main element of our functional model of the OHC is the mechanomotility circuit with the general transfer characteristic y=ktanh(x-a). The parameter k of this characteristic reflects the axial stiffness of the OHC, and the parameter a working position of the hair bundle. The efferent synaptic signals act on the parameter k directly and on the parameter a indirectly through changes in the membrane potential. The dependences of the sensitivity and selectivity on changes in the parameters a and k are obtained by the computer simulation. Functioning of the model at low-level input signals is linear. Due to the non-linearity of the transfer characteristic of the mechanomotility circuit the high-level signals are compressed. For the adaptation and efferent control, however, the transfer characteristic with respect to the initial operating point should be asymmetrical (a>0). The asymmetry relies on the deflection of the hair bundle from the axis of the OHC.     

New method of sedation in oral surgery

Local anesthesia, the well-known method of sedation, usually is insufficient for dental implantation and the augmentation of the alveolar ridge, because the operations last for 1 to 2 hours and patients may experience fear and strain. This article examines a new complex sedation method using ketorolac, midazolam, and a local anesthetic 4% solution of articaine hydrochloride and epinephrine (Septanest) in combination with a vasoconstrictor. This method was applied to 67 patients operated on for dental implantation with screw implants or for the alveolar ridge augmentation with biocompatible materials. The control group, which consisted of 20 patients, received local anesthesia with articaine-epinephrine only. Most of the control patients were found to have experienced fear and strain during the aforementioned surgical procedures; their blood pressure and pulse rate increased, and more than half of them experienced pain. No disorders of hemodynamics or the psychoemotional status of the patients were observed during sedation with ketorolac, midazolam, and articaine-epinephrine. Furthermore, anterograde amnesia was determined for the 80% of the patients in the test group.