Deactivation kinetics and modelling of coke removal under supercritical conditions for the example of ethylbenzene disproportionation

Deactivation kinetics and coke removal kinetics were derived from experimental studies on the disproportionation of ethylbenzene with a protonated Y-faujasite (Z-14) in a loop reactor under supercritical conditions. Derivation of the steady state kinetics of ethylbenzene disproportionation permitted determination of the catalyst activity. At small educt mole fractions of ethylbenzene, owing to the modest removal of coke the deactivation kinetics can be described by a power relationship. The rate of coke removal can be correlated with the activity and the deactivation rate of the catalyst.     

Peroxid-induzierte thioladdition an polybutadien

The free-radical addition of 1-octanediol or 3-(trimethoxysilyl)-1-propanethiol on polybutadiene occurs redox-induced with dibenzoylperoxid (DBPO) at room temperature, without any side-reaction. 1,4-trans double bonds do not undergo thiol reactions, similar to the photochemical addition. The molecular weight distribution of the products is comparable with that of the initial polybutadiene.     

Effects of subchronic administration of metrifonate on cholinergic neurotransmission in rats

The effects of subchronic oral administration of metrifonate, a long-acting cholinesterase (ChE) inhibitor, on cholinergic neurotransmission were assessed in young adult male Wistar rats. Animals were treated twice daily with metrifonate. In a pilot study testing a 100 mg/kg dose of metrifonate for up to 14 days, ChE activity was found to steadily decrease to reach maximum inhibition levels of about 55%, 80% and 35% in brain, erythrocytes and plasma. Steady-state inhibition levels were attained by the 10th day of treatment. When metrifonate-treatment was discontinued, ChE activity in plasma returned to control levels within another day, while erythrocyte and brain ChE activity took more than 2 weeks to recover. In subsequent dose-response studies, metrifonate treatment was given for 3 and 4.5 weeks at doses of 0, 12.5, 25, 50, and 100 mg/kg, to different groups of animals, respectively. Correlation analysis indicted that brain ChE inhibition was more accurately reflected by erythrocyte than by plasma ChE inhibition, although all effects were highly correlated. The changes in ChE activity were not paralleled by changes in other parameters of the cholinergic neurotransmission, such as acetylcholine synthesis rate or acetylcholine receptor binding. It is therefore concluded that repeated administration of metrifonate to rats induces a long-lasting inhibition of ChE activity in a dose-related and predictable manner, which is neither subject to desensitization nor paralleled by counterregulatory downregulation of muscarinic or nicotinic receptor binding sites in brain.     

Can male decorticate rats copulate?

28 hooded sexually experienced or naive male rats, subjected to neocortex removal or neocortex plus hippocampus removal, were paired with female rats for up to 180 days and compared with 14 control rats with respect to success and latency to impregnate the female. All of the controls and half of the brain-damaged Ss successfully impregnated females at least once. Success was not correlated with lesion type or presurgical experience. The brain-damaged Ss took longer to impregnate the females than did controls. Since the ablations were extensive, more than 95% of the neocortex in many Ss, results show that decorticate rats can copulate. Presumably the intact subcortical structures are sufficient for male copulation, but cortical structures in some way facilitate rapid female impregnation. (28 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Involvement of the olfactory bulb in consolidation processes associated with long-term memory in rats.

In a daily training paradigm, rats were trained to discriminate between spatially distinct electrical stimulations delivered to one olfactory bulb. Xylocaine injections were used to disrupt the olfactory bulb functioning in the region close to the electrode tips for 1 hr after each training session. The treatment started either just after the session or 2 hrs later. When compared with the performance of saline-injected rats, the performance of Xylocaine-injected rats was unimpaired except when the treatment started just after the daily session. In that case, acquisition of the task was slightly altered, and retention over a 5-day period was dramatically impaired. It is concluded that, within 1 hr following training, the olfactory bulb is engaged in consolidation processes critical for long-term retention of learned olfactory cues. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

ON-OFF amacrine cells in cat retina

We studied the morphology, photic responses, and synaptic connections of ON-OFF amacrine cells in the cat retina by penetrating them with intracellular electrodes, staining them with horseradish peroxidase, and examining them with the electron microscope. In a sample of seven cells, we found two different morphological types: the A19, which ramifies narrowly in stratum 2 (sublamina a) of the inner plexiform layer, and the A22, which ramifies mostly in stratum 4 (sublamina b) but extends some dendrites to sublamina a. Both of these cell types have axon-like processes that extend > 800 microns from the conventional dendritic arbor. ON-OFF amacrine cells in our sample had receptive fields (1.7 +/- 0.3 mm diameter) that were broader than their dendritic arbors (425 +/- 35 microns diameter) and that extended over the region of axon-like processes. In addition, we found many features in common with ON-OFF amacrine cells in poikilotherm vertebrates: a broad receptive field without surround antagonism, two sizes of spike-like events, narrow dynamic range (1 log unit intensity), and excitatory postsynaptic potentials at light on and light off. Two A19 amacrine cells were examined in the electron microscope: most synaptic inputs (93 and 76%, respectively) to either cell were from amacrine cells, with minor inputs from cone bipolar cells. Synaptic outputs were to bipolar, amacrine, and ganglion cells, including the OFF-alpha cell.     

Progressive atrophy of pyramidal neuron dendrites in autoimmune MRL-lpr mice

The autoimmune-prone MRL-lpr substrain of mice develop an autoimmunity-associated behavioral syndrome (AABS) which resembles in many respects the behavior of animals exposed to chronic stress. The present study examined whether these mice show changes in the morphology of neuronal dendrites, as found in animals exposed to chronic stress. A modified Golgi-Cox procedure was used to visualize the dendrites of pyramidal neurons in the parietal cortex and in the CA1 hippocampal field of 5-week and 14-week old MRL-lpr mice and MRL + / + controls. Reduced dendritic branching and length, and an up to 20% loss of dendritic spines were observed in parietal and hippocampal pyramidal neurons of MRL-lpr mice at both ages. In the parietal cortex, there was an age-dependent potentiation in the reduction of basilar, but not apical, dendrite branching and length, as well as in the loss of spines on basilar segments. Loss of spines in the hippocampus followed an age-related course for apical but not basilar dendrites. Moreover, compared to age-matched controls, brain weight was smaller in MRL-lpr mice at 14 but not 5 weeks of age. Considering that dendritic atrophy becomes more extensive when autoimmune disease is florid in MRL-lpr mice, it is proposed that immune/inflammatory factor(s) produce dendritic loss. Reduced dendritic complexity may represent, at least in part, a structural basis for the altered behavioral profile of MRL-lpr mice.     

Prefrontal cortex and the regulation of food intake in the rat.

Studied the postoperative regulation of food and water intake in a total of 103 male Wistar albino rats with aspiration lesions to either the medial frontal or orbital frontal projection fields of thalamic nucleus medialis dorsalis (prefrontal cortex). These projection fields proved functionally dissociable in that orbital frontal lesions impaired immediate postoperative regulation of food and water intake for up to 2 wks, while medial frontal lesions produced finickiness. Neither lesion affected response to cellular dehydration or recovery from extended deprivation. Data are consistent with data from rhesus monkeys with prefrontal lesions and differ from animals with lateral hypothalamic lesions. (27 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)