Monoclonal antibody 18B8, which detects synapse-associated antigens, binds to ganglioside GT3 (II3 (NeuAc)3LacCer)

By immunofluorescence, mouse monoclonal antibody 18B8 detects developmentally regulated antigens in chick neural retina. In older embryos and in adults these antigens are localized in discrete laminae within the inner and outer synaptic layers. The antibody binds to several gangliosides that undergo both qualitative and quantitative changes during neuronal development (Grunwald, G.B., Fredman, P., Magnani, J.L., Trisler, D., Ginsburg, V., and Nirenberg, M. (1985) Proc. Natl. Acad. Sci. U.S.A. 82, 4008-4012). The simplest of these gangliosides was isolated from lipid extracts of 10-day chick embryonic retinas by DEAE-Sepharose and silicic acid column chromatography. About 300 micrograms was obtained from 9.3 g (wet weight) of retina. The isolated ganglioside was identified as GT3 by enzymatic analysis and by a comparison of its properties with the authentic ganglioside. By immunostaining thin-layer chromatograms with antibody 18B8, GT3 was detected in gangliosides from human neural tissue including cerebellum, optic nerve, and spinal cord, but not in gangliosides from human liver, pancreas, small intestine, adrenals, thyroid, or erythrocytes. GT3 was also found in five of seven human melanoma cell lines.     

Memory of a choice direction in a T maze as measured by spontaneous alternation in mice: Effects of intertrial interval and reward

Spontaneous alternation in a T maze was studied as a one trial learning paradigm in mice of the BALB/c strain. In the first experiment the combined effects of time interval between the first and second trial (intertrial interval: ITI), food deprivation and feeding given during the first trial, were shown to affect performance. Thus, on the one hand, the percentage of spontaneous alternation decreased as ITI increased; on the other hand, food reward dramatically improved spontaneous alternation for the 24-h ITI, but had no significant effect for 30-sec and 1-h ITI. Since the effect of feeding might be due either to an increase of arousal, thus favoring input of informations associated with the first choice, or to an improvement in memory consolidation, a second experiment was aimed at testing the effect of food given after the first trial. It was shown that, as in the first experiment, post-trial feeding improved spontaneous alternation on the second trial given 24 hours later with a temporal gradient of effect less than 30 min. These results clearly showed that the reinforcement of run to one side (first trial) increased the tendency to go to the other side 24 hours later. It is concluded that reinforcement might have two distinct effects: (i) according to SR theory, reinforcement increases conditioned responses and (ii), as shown here, acts on memory processes by preventing memory traces from fading. The fact that this last effect was only observed for long ITI suggests that short-term or transient memory and long-term memory are two relatively independent processes.     

Les cellules ciliées de l'antéhypophyse

Résumé Deux types de cils sont décrits dans les cellules de l'antéhypophyse du Hamster doré et du Hérisson: l'un de ces types est défini par la formule 9 + 0 et s'observe dans les cellules glandulaires sécrétrices; l'autre type est caractérisé par la formule 9 + 2 et se localise dans les cellules bordantes des plages colloïdales. En fonction des données bibliographiques, la répartition et la signification fonctionnelle des deux types de cils sont discutées.

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The ciliated cells of antehypophysisElectron-microscopic study

Summary Two types of cilia occur in golden hamster and hedgehog pituitary cells: one (9 + 0 pattern) is obseryed in secretory cells, the other (9 + 2 pattern) is found in colloid bordering cells. Distribution and functional significance of the two types of cilia are discussed in reference to the literature.

     

Improving eDNA-based protist diversity assessments using networks of amplicon sequence variants

Effective and precise grouping of highly similar sequences remains a major bottleneck in the evaluation of high-throughput sequencing datasets. Amplicon sequence variants (ASVs) offer a promising alternative that may supersede the widely used operational taxonomic units (OTUs) in environmental sequencing studies. We compared the performance of a recently developed pipeline based on the algorithm DADA2 for obtaining ASVs against a pipeline based on the algorithm SWARM for obtaining OTUs. Illumina-sequencing of 29 individual ciliate species resulted in up to 11 ASVs per species, while SWARM produced up to 19 OTUs per species. To improve the congruency between species diversity and molecular diversity, we applied sequence similarity networks (SSNs) for second-level sequence grouping into network sequence clusters (NSCs). At 100% sequence similarity in SWARM-SSNs, NSC numbers decreased from 7.9-fold overestimation without abundance filter, to 4.5-fold overestimation when an abundance filter was applied. For the DADA2-SSN approach, NSC numbers decreased from 3.5-fold to 3-fold overestimation. Rand index cluster analyses predicted best binning results between 97% and 94% sequence similarity for both DADA2-SSNs and SWARM-SSNs. Depending on the ecological questions addressed in an environmental sequencing study with protists we recommend ASVs as replacement for OTUs, best in combination with SSNs.     

LRF producing cells of the mammalian hypothalamus

Summary The demonstration of perikarya of mediocellular neurones producing LRF, using indirect immunofluorescence on slides and anti synthetic LRF antibodies, requires both their activation and the inhibition of their axoplasmic transport. This fact suggests that LRF is present in an immunoreactive form, but usually in very low concentrations. Perikarya of neurons producing LRF are found principally in the preoptic and septal areas of the rat and decrease caudally, particularly beyond the retrochiasmatic area. Most of the axons coming from these perikarya are incorporated in the hypothalamoinfundibular tract and terminate around the capillaries of the primary portal plexus, particularly those of interealar plexus. Other axons (or axon collaterals) may be found in various areas (suprachiasmal crista, epithalamus, amygdala, mesencephalon) and form circuits recalling the “extrahypophyseal pathways” described for the magnocellular Gomori-positive neurons of the SON and PVN. These axons are probably concerned in intersegmental regulations involving “neurosecretory synapses”, particularly of the axosomatic type. The placement of stereotaxic lesions was used to determine the topography and direction of axoplasmic flow of the axons transporting LRF. The infundibular immunoreactive material, already discernible at the end of gestation in the foetus, shows considerable variations between birth and puberty, during the estrous cycle and under various other physiological or experimental conditions. The observations made under various experimental or physiological conditions suggest that, in the guinea-pig in particular, the greater part of the hypothalamic immunoreactive material is concentrated in the infundibular area. This area of accumulation is comparable to the distal neurohypophysis of the Gomori-positive neurosecretory system coming from the SON and PVN. This work was financed by the D.G.R.S.T. Contract No. 72-7-0375.     

Dedifferentiated variants of a rat hepatoma: Reversion analysis

Revertants of dedifferentiated variants of Reuber H35 rat hepatoma cells can be readily detected, for they acquire the ability to proliferate in G^? (glucose-free) medium owing to the production of phosphoenolpyruvate carboxykinase and fructose diphosphatase, two liver-specific enzymes required for the gluconeogenic pathway. We have tried to obtain both spontaneous and mutagen-induced revertants of two independent variant lines of hepatoma cells, H5 and Faofl, both characterized by the absence of expression of all or most of the seven liver-specific functions analyzed. No spontaneous or mutagen-induced revertant of 1s or 2s H5 cells has been obtained among a total of 3.3 × 10⁹ cells challenged with G^? medium; we conclude that multiple and/or irreversible changes underlie the dedifferentiation of H5 cells. Three out of five subclones of Faofl cells gave rise to revertants, at frequencies of 1–7 × 10^?8. FaoflC2 cells were treated with EMS, X-rays or ICR-191G; the numbers of revertants in the treated populations were not above background. All the Faofl revertants are of one phenotypic class: they express not only the two gluconeogenic enzymes necessary for survival in G^? medium but also all of the other liver functions examined. We conclude that reversion of Faofl cells involves modification in activity of genes responsible for regulation of the entire group of liver functions, and that this change is not provoked by mutagens.