Calcium in hippocampus following lidocaine induced seizures: an electron cytochemical study

The effect of lidocaine seizures on cellular accumulation of calcium was studied in hippocampal subfields CA1 and CA3 and the dentate gyrus of rats, using the combined oxalate-pyroantimonate method. The specificity of the reaction was ascertained by EGTA treatment and X-ray microanalysis. In control rats, calcium was visualized between myelin lamellae of axons, in synaptic vesicles and in some lysosomes. Two hours after onset of lidocaine seizures selective neuronal degenerations appeared in hippocampal subfields CA1 and CA3 but not in the dentate gyrus. Calcium deposits were present in numerous mitochondria of pyramidal cells and, occasionally, also of neuroglial cells. Many of these mitochondria exhibited ultrastructural alterations. Calcium uptake was most prominent in the CA3 sector but was also present in the CA1 subfield as well as the dentate gyrus. Intracellular calcium uptake, in consequence, is not the unique attribute of selectively vulnerable hippocampal neurons.     

Partial 1p monosomy in a physically and mentally retarded boy

An 8-year-old boy is reported with marked mental and physical retardation, microcephaly, hypertelorism, mongoloid palpebral fissures, hypoplasia of the maxillary portion of the face, and other discrete anomalies. Deletion of the distal portion of the short arm of the chromosome 1 and the karyotype 46,XY, del(1)(p33----pter) was detected.     

Methylamine does not inhibit rates of endogenous lipolysis in isolated myocardial cells from rat heart

Triacylglycerol lipase activity with a pH optimum of 5 was present in homogenates of myocardial cells from rat heart. Acid lipase activity was inhibited by serum, heparin, and increased ionic strength. Methylamine, a lysosomotropic agent, did not inhibit the basal or isoproterenol-stimulated rate of endogenous lipolysis as measured by glycerol output from control myocytes. Similarly, accelerated rates of glycerol output that are a consequence of an elevation in the intracellular stores of triacylglycerols in myocytes from diabetic rat hearts and from myocytes prepared with free fatty acids in the isolation solutions were not reduced by methylamine. Therefore, the acid lysosomal triacylglycerol lipase must not be involved in the mobilization of endogenous triacylglycerols in myocardial cells from rat heart.     

Testing a model of excitatory interactions between oscillators

The experimentally observed influence of regularly arriving tugs upon the AP discharge of the slowly-adapting stretch receptor organ (SAO) of crayfish was compared to a model of pacemaker excitatory synaptic interactions (Segundo and Kohn 1981). Criteria for compliance referred to facets as A) the excitation, B) the postulates, and C) the behavior. A) Excitation was implied primarily by the tug initially increasing the AP rate (it subsequently decreased it). B) The pacemaker AP discharges, and with more reason the electronically driven tugs, were considered acceptably regular sequence (postulate i). Tugs advanced the next AP (postulate ii); the "delay function" plots of delays vs. phases, i.e. interval shortenings vs. the time from the last AP to the tug, were close to the V of postulate iii, even though the shortest phases tended to postpone the next AP and the longest ones did not trigger immediately but with an around 5 ms latency. These effects were displayed also as "old phase vs. new phase" plots. The interval following that with the tug tended to be lengthened, but the pre-tug timing was not recovered. C) Behavior during a train of excitatory events, both in model and experiments, went through very similar initial settlings and eventual steady-states. The latter were characterized in the model by 1. an average excitatory vs. excited rate display formed by an endless number of segments with all positive rational slopes separated by negative-going discontinuities, 2. locking in the sense of preferential phases, and 3. periodic repetition of the same phases and inter-AP intervals. Experimental results were compatible with this. Such behavior was absent when the tug sequence was highly irregular. The initial settling, in the SAO as in the model, depended jointly on the first phase phi 1 and the intertug interval E. If the former was under lambda, it went through one or two monotonic phase-decreasing stages (one smaller, the other larger, than lambda), or through a single increasing one, depending on E being smaller or greater than, respectively, an estimated but never actually observed E leading to unstable lockings. If the initial phase was greater than lambda, settling with E's under rN + lambda involved jumps between larger than and smaller than lambda phases; with E's over rn + lambda, it involved an intermediate stable locking with phi = E-rN.(ABSTRACT TRUNCATED AT 400 WORDS)     

Humic acids inhibit the formation but not the mutagenicity of N-methyl-N-nitrosourea

Humic acids in the form of potassium humate (KH), at concentrations exerting a strong inhibitory effect on the formation of N-methyl-N-nitrosourea (MNU) when present during the nitrosation of N-methylurea (MU) at pH 3, did not reduce the mutagenicity of preformed MNU in Tradescantia, clone 4430. The inhibitory effect of 20 mg/ml KH corresponds approximately to that of 3.75 mM (0.66 mg/ml) ascorbic acid towards the formation of MNU from the mixture of 7.5 mM MU + 7.5 mM NaNO2.     

Cytochemical localization of calcium in renal sac nephrocytes of Helix aspersa

In renal sac nephrocytes of Helix aspersa, intracellular calcium has been localized using the oxalate-pyroantimonate (OPA) and phosphate-pyroantimonate (PPA) methods. Pyroantimonate precipitates are preferentially localized in the excretory spherule and in vesicles located in the basal and lateral regions of the nephrocyte. Such vesicles appear to release their content into the excretory vacuole. Calcium may interact with diverse types of molecules present in the excretory vacuole, thus favouring stabilization and packaging of the excretory spherule.     

Germination of concentrated suspensions of spores from Aspergillus niger

Summary Germination of condiospores fromA.niger in very concentrated suspension was required to inoculate solid fermentation media, but a germination self-inhibitor was detected in spores. It was found that the inhibitory effect depended on the composition of the medium and was reduced when glucose was used as a carbon source. The effect of the self-inhibitor was eliminated by washing the spores and using glucose and a protein nitrogen source in the germination medium. By this method it was possible to increase about 100 times (10⁶ to 10⁸) spore concentration, keeping more than 90% germination.     

Functional alpha 2-adrenoceptors in rat adipocytes: inhibition of cyclic AMP accumulation

Alpha 2-adrenoceptor activation inhibits cyclic AMP accumulation in fat cells from many species. However, the presence of alpha 2-adrenoceptors in rat adipocytes has been difficult to demonstrate. We observed that alpha 2-adrenergic activation inhibits forskolin-stimulated cyclic AMP accumulation both in rat and hamster adipocytes; UK 14304, p-amino clonidine and clonidine were the agents with higher efficacy. The effect of UK 14304 was blocked by yohimbine but not by prazosin demonstrating the involvement of alpha 2-adrenoceptors. Pertussis toxin blocked the alpha 2-adrenergic effect. Our results demonstrate the presence in rat fat cells of alpha 2-adrenoceptors coupled to adenylate cyclase via "Gi".     

Effect of prenatal exposure to alcohol on membrane-bound enzymes during astrocyte development in vivo and in primary culture

In the present work we have analyzed the effect of prenatal ethanol exposure on the activity of several glial marker and functional enzymes during the development of astrocytes isolated from rat brain as well as in primary culture. The activity of marker enzymes glutamine synthetase and butylcholinesterase showed no differences between isolated astrocytes from 15 and 70 day old control rats. However, the activity of the membrane-bound enzymes (Na+K)ATPase and 5'-nucleotidase was higher in astrocytes from 70 day old control rats than in those from 15 day old animals. Although the pattern found in astrocytes from alcohol-exposed rats was similar to that of controls, the levels of activity of the enzymes were lower in alcoholic than in control animals. When control astrocytes in primary culture were used, the activity of (Na+K)ATPase and 5'-nucleotidase increased throughout the entire culture period. In contrast, the maximal activity of glutamine synthetase was found at 7 days of culture. Ethanol also induced a decrease in the activity of all enzymes, which was more evident at the end of the culture period. These results indicate that the activity of the enzyme markers analyzed increased mainly during the first weeks of life and remained constant after this period. By contrast, the membrane-bound enzymes studied showed a progressive increase with age. In conclusion, since these astrocyte enzymes are important in the regulation of several neuronal functions through the control of the composition of extracellular fluid, the effect of ethanol on their activities could explain some of the neuronal alterations reported in children and animals exposed to ethanol during development.