Macroglial cells of the teleost central nervous system: a survey of the main types

Following our previous review of teleost microglia, we focus here on the morphological and histochemical features of the three principal macroglia types in the teleost central nervous system (ependymal cells, astrocyte-like cells/radial glia and oligodendrocytes). This review is concerned with recent literature and not only provides insights into the various individual aspects of the different types of macroglial cells plus a comparison with mammalian glia, but also indicates the several potentials that the neural tissue of teleosts exhibits in neurobiological research. Indeed, some areas of the teleost brain are particularly suitable in terms of the establishment of a “simple” but complete research model (i.e. the visual pathway complex and the supramedullary neuron cluster in puffer fish). The relationships between neurons and glial cells are considered in fish, with the aim of providing an integrated picture of the complex ways in which neurons and glia communicate and collaborate in normal and injured neural tissues. The recent setting up of successful protocols for fish glia and mixed neuron-glia cultures, together with the molecular facilities offered by the knowledge of some teleost genomes, should allow consistent input towards the achievement of this aim.     

Relationship between Bacillus sphaericus spore heat resistance and sporulation temperature

Bacillus sphaericus 9602 was grown in batch culture at various temperatures. At 10°C and 12°C the maximum sporulation yield was <10%, while at 15°C, 20°C and 30°C, a sporulation yield of >95% was achieved. However at 40°C B. sphaericus grew only vegetatively. The heat resistances (D values at 90°C) of spores grown at 15°C and 20°C were significantly higher than those grown at 30°C.     

Ant colony optimization for real-world vehicle routing problems

Ant colony optimization (ACO) is a metaheuristic for combinatorial optimization problems. In this paper we report on its successful application to the vehicle routing problem (VRP). First, we introduce the VRP and some of its variants, such as the VRP with time windows, the time dependent VRP, the VRP with pickup and delivery, and the dynamic VRP. These variants have been formulated in order to bring the VRP closer to the kind of situations encountered in the real-world. Then, we introduce the basic principles of ant colony optimization, and we briefly present its application to the solution of the VRP and of its variants.     

Growth form and leaf habit drive contrasting effects of Arctic amplification in long-lived woody species

Current global change is inducing heterogeneous warming trends worldwide, with faster rates at higher latitudes in the Northern Hemisphere. Consequently, tundra vegetation is experiencing an increase in growth rate and uneven but expanding distribution. Yet, the drivers of this heterogeneity in woody species responses are still unclear. Here, applying a retrospective approach and focusing on long-term responses, we aim to get insight into growth trends and climate sensitivity of long-lived woody species belonging to different functional types with contrasting growth forms and leaf habits (shrub vs. tree and deciduous vs. evergreen). A total of 530 samples from 7 species (common juniper, dwarf birch, woolly willow, Norway spruce, lodgepole pine, rowan, and downy birch) were collected in 10 sites across Iceland. We modelled growth trends and contrasted yearly ring-width measurements, filtering in high- and low-frequency components, with precipitation, land- and sea-surface temperature records (1967–2018). Shrubs and trees showed divergent growth trends, with shrubs closely tracking the recent warming, whereas trees, especially broadleaved, showed strong fluctuations but no long-term growth trends. Secondary growth, particularly the high-frequency component, was positively correlated with summer temperatures for most of the species. On the contrary, growth responses to sea surface temperature, especially in the low frequency, were highly diverging between growth forms, with a strong positive association for shrubs and a negative for trees. Within comparable vegetation assemblage, long-lived woody species could show contrasting responses to similar climatic conditions. Given the predominant role of oceanic masses in shaping climate patterns in the Arctic and Low Arctic, further investigations are needed to deepen the knowledge on the complex interplay between coastal tundra ecosystems and land-sea surface temperature dynamics.     

Stability Studies on Random Folded RNAs (‘Never Born RNAs’), Implications for the RNA World

In the last years, we have developed a method for the study of random RNA sequences with the aim of investigating their capacity to assume folded and possibly functionally active (ribozymes) structures. The RNA Foster assay developed in our laboratory is a powerful, simple, and fast method to investigate the structural properties of RNA by assessing the presence of secondary domains and their thermal stability through the combination of S1 nuclease activity at different temperatures. In this work, we investigated the structural properties of totally de novo random RNAs, 97‐nucleotides‐long, of which 60 nucleotides were completely random. The rationale behind this was to assess whether and to what extent random RNAs would acquire a stable fold as a prerequisite for catalytic activity. A library of random sequences was created, and 18 sequences were randomly selected and analyzed. Surprisingly, most of the RNAs were resistant to S1 nuclease digestion at up to 50°, and two sequences were resistant even at 70°, suggesting that these totally random RNA molecules could posses a stable secondary structure over a broad range of temperatures under the conditions used. We discuss the possible relevance of these data for the general scenario of the RNA world.     

Observations on spike sequences from spontaneously active Purkinje cells in the frog

Zusammenfassung Die Frage wird aufgeworfen, inwiefern man aus der Statistik der Impulsfolgen bei Spontanaktivität einzelner Neurone auf die Funktionscharakteristik des Neurons selbst und auf die Art seiner Einschaltung in das Nervennetz schließen kann. Die Untersuchung der Verteilung der Intervalle verschiedener Dauer zwischen aufeinanderfolgenden Aktionspotentialen von Purkinjezellen des Froschkleinhirns ergibt, in Übereinstimmung mit den von anderen Autoren bei anderen Neuronentypen erhobenen Befunden, zwei Arten von Histogrammen: einerseits unimodale, vorwiegend bei Neuronen mit höherer Impulsfrequenz, andererseits bi- und trimodale, vorwiegend bei niedriger Impulsfrequenz. Die Form der unimodalen Verteilungen läßt, unter Annahme einer Gaußschen Verteilung der Erregungsniveaus im Eingang des Neurons, die sich aus der Summation einer großen Anzahl voneinander unabhängiger afferenter Erregungen ergibt, auf einen nichtlinearen Zusammenhang zwischen Erregungsniveaus und Dauer der Intervalle schließen; die unsymmetrische Verteilung der Intervalle wäre demnach als eine Verzerrung der statistisch gegebenen symmetrischen Verteilung der Erregungsniveaus zu verstehen. Diese Erklärung hat den Vorteil, kontinuierlich zu den bei niedriger Impulsfrequenz beobachteten unregelmäßigen Verteilungen überzuleiten, die sich einfach aus dem Zusammenbruch der statistischen Regelmäßigkeit im Falle von einer geringen Anzahl aktiver Fasern im Eingang ergeben. Die Untersuchung von Korrelationen innerhalb der Impulsfolgen mit Hilfe einer Verzögerungs- und Koinzidenzschaltung ergibt scharfe Maxima der Impulswahrscheinlichkeit als Funktion des zeitlichen Abstands von vorhergehenden Impulsen. Da diese Autokorrelogramme bei verschiedenen Neuronen derselben Art (Purkinjezellen des Froschkleinhirns) verschiedene Verläufe zeigen, wird zu ihrer Erklärung weniger eine Eigenschaft des Einzelneurons (Schwellenänderung nach em Aktionspotential) herangezogen, als die Rückwirkung des eurons auf sich selbst auf dem Umweg über andere Neurone es Nervennetzes. Die Korrelation zwischen Impulsreihen in erschiedenen Neuronen desselben Nervennetzes, die auf Grund ieser Annahme zu erwarten ist, wird in einigen Beispielen uch gefunden, wovon eines im Anhang gezeigt wird.

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The research reported in this document has been sponsored in part by the U.S.A.F., Grant AF-EOAR 63–89 and by the National Institute of Health, Grant NB 03922-02.

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Laboratori Nazionali di Frascati del C.N.E.N.     

A sensitive routine assay for urinary albumin based on the competitive binding to anti-albumin antibodies in solid phase

The detection of microalbuminuria has a high prognostic value in diabetic patients with no symptoms of clinical nephropathy. Attention has been focused on the development of a simple, reproducible, specific, and, above all, sensitive method to detect albuminuria in the urine. The method is based on the competitive binding between albumin in the urine to be tested and a fixed amount of radiolabelled albumin to anti-albumin immunoglobulins in solid phase. The immunoglobulin C fraction of a rabbit anti-human albumin antiserum was left to coat highly adsorbent polystyrene microtitre tubes. While the aspecific tube binding was overcome by saturation with a solution of gelatine, increasing dilutions of standard albumin or the diluted urine samples to be tested were left to incubate with an equal volume of radiolabelled albumin at room temperature for 1 hour. The cold/hot albumin mixture was added to anti-albumin immunoglobulin-coated tubes, which had been repeatedly washed, and left to incubate. After washing, radioactivity was assessed. This assay has proved to be fast, simple and highly sensitive since it detects up to 25 ng of albumin per ml and is of value in large-scale screening for microalbuminuria in diabetic patients.