Ultrafast Torsional Relaxation from the Barrier Region for an Excited-State Isomerization in Solution: 9-Carbonylanthracenes

The class of compounds containing a carbonyl group substituted at the 9 position of anthracene have been studied as new model systems for torsional isomerization in solution. Franck-Condon excitation yields an excited-state distribution near the barrier for isomerization in S₁. Using time-resolved fluorescence spectroscopy, we have determined that the relaxation from the barrier region is subpicosecond for three different compounds in all solvents studied. In fact, the relaxation seems to be almost independent of solvent at room temperature, indicating that most of the local friction felt by the twisting carbonyl is internal friction rather than solvent friction. Apparently the small carbonyl is effectively shielded from the solvent by the anthracene ring so the solvent friction is not strong. In contrast to the weak solvent coupling, previously reported gas-phase spectra indicate that the torsion may be strongly coupled to the other vibrational modes of the molecule. Energy flow out of the torsion into these other vibrational modes appears to occur on the subpicosecond time scale.     

Neurotensin--structure, origin and biological function

We have developed a least-squares refinement procedure that in an automated way performs three-dimensional alignment and averaging of objects from multiple reconstructions. The computer implementation aligns the three-dimensional structures by a two-step procedure that maximizes the density overlap for all objects. First, an initial average density is built by successive incorporation of individual objects, after a global search for their optimal three-dimensional orientations. Second, the initial average is subsequently refined by excluding individual objects one at a time, realigning them with the reduced average containing all other objects and including them into the average again. The refinement is repeated until no further change of the average occurs. The resulting average model is therefore minimally biased by the order in which the individual reconstructions are incorporated into the average. The performance of the procedure was tested using a synthetic data set of randomly oriented objects with Poisson-distributed noise added. The program managed well to align and average the objects at the signal/noise ratio 1.0. The increase in signal/noise ratio was in all investigated cases almost equal to the expected square root of the number of objects. The program was also successfully tested on a set of authentic three-dimensional reconstructions from an in situ specimen containing Escherichia coli 70S ribosomes, where the immediate environment of the reconstructed objects may also contain variable amounts of other structures.     

Expression of Ca2+-dependent (classical) PKC mRNA isoforms after transient cerebral ischemia in gerbil hippocampus

Cerebral ischemia is known to modify the expression of genetic information in the brain. To complement this knowledge, in the present study we have estimated the expression of calcium- and phospholipid-dependent (classical) protein kinase C (c PKC) isoform mRNAs (alpha, beta1 and gamma) at different time following ischemia. Forebrain cerebral ischemia was performed on Mongolian gerbils by 5 minutes bilateral occlusion of common carotid arteries. At the pointed time the cytoplasmic RNA was extracted from hippocampus and the expression of PKC mRNA quantified by RT PCR technique using GAPDH expression as an internal standard. Results indicate that only one gamma isoform of cPKC mRNA expression becomes significantly modified in postischemic hippocampus. A transient increase up to 145% of control within the first 3 h was followed by its decline to 60-65% at a longer recirculation period. This lowered levels returned back to control at 72 h postischemic recovery. This result indicates that gamma PKC could be particularly sensitive to ischemic insult and would react in accordance with the other early signals determining ischemic outcome.     

Respiratory potentials recorded from the human hindbrain

OBJECTIVES: An experimental study has been conducted to investigate testicular blood flow alterations through acute biochemical changes during unilateral testicular torsion and detorsion. METHODS: One hundred twenty male albino rats were divided into 12 groups, each containing 10 rats. One group served to determine basal values of biochemical parameters, 4 groups were subjected to varying periods of unilateral testicular torsion (3, 6, 12, and 24 hours, respectively), 3 groups were subjected to detorsion following varying periods of torsion (6, 12, and 24 hours, respectively), and 4 groups underwent sham operations as controls. Levels of lactic acid, hypoxanthine, and lipid peroxidation products were determined in testicular tissues. RESULTS: Values of these 3 parameters obtained from sham operation control groups did not differ significantly from basal values (p > 0.05). All 3 parameters were increased significantly in both ipsilateral torted and contralateral nontorted testes after unilateral testicular torsion when compared with basal values (p < 0.05). Detorsion did not cause significant changes in levels of lipid peroxidation products in both ipsilateral torted and contralateral nontorted testes when compared with values obtained after torsion (p > 0.05). CONCLUSIONS: Ipsilateral testicular torsion causes a decrease not only in the ipsilateral torted but also in the contralateral nontorted testicular perfusion. The clues of reperfusion injury do not become evident following detorsion of testicular torsion lasting more than 6 hours.     

Early cellular and humoral response after vascular prosthesis implantation in the arterial system]

The aim of the study was to determine the level of leukocytes activation after the implantation of vascular graft. As an experimental model we used 20 dogs. The aorto-iliac unilateral graft (dacron 6 mm) was implanted to all animals. The adhesion and migration of the leukocytes was estimated postoperatively by scintigraphy using Tc99 labeled leukocytes. The increased migration and adhesion was found in both proximal and distal anastomoses till the 30th postoperative day and it was more intensive in the distal anastomosis.     

Interhemispheric extracranial and intracranial tumor of parietal area (chondromyxoid fibroma) in a 13-year-old child with 7 years of follow-up

A case of extra-intracranial, parietal chondromyxoid fibroma in a 13-year old girl operated successfully and followed by 7-years observation is presented. Apart from infrequent occurrence of the tumour diagnostic difficulties due to atypical cranial location are emphasized.     

Automatic regulation of sinus rhythm in patients with migraine

The clinical symptoms of migraine point to autonomic disturbances, especially to disrupted regulation of the circulatory system and autonomic balance. Searching for more accurate autonomic system studies we turned to the spectral analysis of cardiac rhythm changes, that allows to estimate the autonomic balance in sinus node. 44 patients with migraine were studied and the results were compared with those obtained in 74 healthy subjects. The reduced influence of both sympathetic and parasympathetic part of autonomic system on the sinus rhythm in migraine patients was found. The autonomic balance is shifted to the parasympathetic innervation side in patients with migraine.     

Effects of lysozyme dimer on humoral response to sheep erythrocytes in non-treated and cyclophosphamide-immunosuppressed mice

The effects of lysozyme dimer on humoral response to sheep erythrocytes (SRBC) and restoration of the response impaired by a single cyclophosphamide dose (200 mg/kg) were tested on mice. The effect of lysozyme dimer on the humoral response to SRBC in non-treated with cyclophosphamide mice was determined in relation to doses (0.2, 2, 20 or 200 micrograms/kg) and the time of the drug administration with respect to the antigen before or after SRBC immunization. Moreover, the effect of lysozyme dimer on the humoral response in cyclophosphamide-treated mice was studied depending on the dose applied and time of exposure to the drug in relation to SRBC. It has been found that lysozyme dimer potentiates the humoral response to SRBC in mice, resulting in an increased number of splenocytes producing haemolytic antibodies (PFC) and the total and 2-mercaptoethanol resistant level of anti-SRBC antibodies. A single exposure to lysozyme dimer gave the strongest stimulating action on SRBC when the doses of 2 or 20 micrograms/kg were administered 2 h prior to the antigen. The potentiating effect of the drug was reduced when it was administered 24 h before the antigen and also when single doses were as high as 200 micrograms/kg and as low as 2 micrograms/kg. Exposure to four doses of lysozyme dimer at 24 h intervals was more activating than a single injection. A strong potentiating effect on the specific response to SRBC was noted after four injections of lysozyme dimer at doses from 0.2 to 20 micrograms/kg. The effect of the drug did not depend on the time of exposure to the antigen. It has also been found that lysozyme dimer significantly reduces the suppressive effect of a high cyclophosphamide dose (200 mg/kg) on the humoral response of SRBC-immunized mice. The protective action of lysozyme dimer was dose- and time-dependent. The strongest protection was observed after three doses of 20 micrograms/kg administered prior to pharmacological immunosuppression. Reduction in the dose to 2 micrograms/kg and shorter treatment resulted in reduced protective effects. We have also found that the protective action of three doses of lysozyme dimer (2 or 20 micrograms/kg each) administered between cyclophosphamide injection and the antigen, or after antigen administration is weaker than such a treatment prior to cyclophosphamide immunosuppression.