The awakening of dormant neuronal precursors in the adult and aged brain

Beyond the canonical neurogenic niches, there are dormant neuronal precursors in several regions of the adult mammalian brain. Dormant precursors maintain persisting post-mitotic immaturity from birth to adulthood, followed by staggered awakening, in a process that is still largely unresolved. Strikingly, due to the slow rate of awakening, some precursors remain immature until old age, which led us to question whether their awakening and maturation are affected by aging. To this end, we studied the maturation of dormant precursors in transgenic mice (DCX-CreER^T2/flox-EGFP) in which immature precursors were labelled permanently in vivo at different ages. We found that dormant precursors are capable of awakening at young age, becoming adult-matured neurons (AM), as well as of awakening at old age, becoming late AM. Thus, protracted immaturity does not prevent late awakening and maturation. However, late AM diverged morphologically and functionally from AM. Moreover, AM were functionally most similar to neonatal-matured neurons (NM). Conversely, late AM were endowed with high intrinsic excitability and high input resistance, and received a smaller amount of spontaneous synaptic input, implying their relative immaturity. Thus, late AM awakening still occurs at advanced age, but the maturation process is slow.     

The relative contribution of somatomedin to the serum-stimulated growth of human fibroblasts

Culture conditions were defined allowing to demonstrate a stimulatory effect of both serum-contained and purified Somatomedin activity on incorporation of [3H]thymidine and replication of cultured normal human fibroblasts. The use of dialyzed human serum in MEM medium supplemented by 0.2 mM serine offered the necessary and sufficient culture conditions. A significant difference between normal and hypopituitary patients sera was found in their effect on the rate of [3H]thymidine incorporation (p < 0.0001) and on cell replication (p < 0.01). Purified Somatomedin-C, in MEM without serum, is a poor mitogen. Its activity was strongly enhanced by the addition of 0.1 % dialyzed serum and 0.2 mM serine without, however, exceeding the stimulatory level of 1 % whole normal serum. The requirement of concomitant presence, for optimal $\text{in}\text{vitro}$ cell growth, of different low and high MW serum components is discussed.     

Characterisation of a chromosomally encoded catechol 1,2-dioxygenase (E.C. 1.13.11.1) from Alcaligenes eutrophus CH34

Alcaligenes eutrophus CH34 used benzoate as a sole source of carbon and energy, degrading it through the 3-oxoadipate pathway. All the enzymes required for this degradation were shown to be encoded by chromosomal genes. Catechol 1,2-dioxygenase activity was induced by benzoate, catechol, 4-chlorocatechol, and muconate. The enzyme is most likely a homodimer, with an apparent molecular weight of 76,000 ± 500. According to several criteria, its properties are intermediate between those of catechol 1,2-dioxygenases (CatA) and chlorocatechol 1,2-dioxygenases (ClcA). The determined K _m for catechol is the lowest among known catechol and chlorocatechol dioxygenases. Similar K _m values were found for para-substituted catechols, although the catalytic constants were much lower. The catechol 1,2-dioxygenase from strain CH34 is unique in its property to transform tetrachlorocatechol; however, excess substrate led to a marked reversible inhibition. Some meta- and multi-substituted catechols behaved similarly. The determined K _m (or K _i) values for para- or meta-substituted catechols suggest that the presence of an electron-withdrawing substituent at one of these positions results in a higher affinity of the enzyme for the ligand. Results of studies of recognition by the enzyme of various nonmetabolised aromatic compounds are also discussed. Received: 20 November 1996 / Accepted: 11 April 1996     

Reading the landscape: Legible environments and hominin dispersals

Wayfinding, or the ability to plan and navigate a course over the landscape, is a subject of investigation in geography, neurophysiology, psychology, urban planning, and landscape design. 1 - 4 With the prevalence of GPS‐assisted navigation systems, or “wayfinders,” computer scientists are also increasingly interested in understanding how people plan their movements and guide others. However, the importance of wayfinding as a process that regulates human mobility has only recently been incorporated into archeological research design. 5 , 6 Hominin groups were able to disperse widely during the course of prehistory. The scope of these dispersals speaks to the innate navigation abilities of hominins. Their long‐term success must have depended on an ability to communicate spatial information effectively. Here, we consider the extent to which some landscapes may have been more conducive to wayfinding than others. We also describe a tool we have created for quantifying landscape legibility (sensu Gollege 2 ), a complex and under‐explored concept in archeology, with a view to investigating the impact of landscape structure on human wayfinding and thus, patterns of dispersal during prehistory. To this end, we have developed a method for quantifying legibility using a Geographic Information System (GIS) and apply it to a test case in prehistoric Iberia.     

Validation of a general method for activity estimation of cyanide evolving oxidoreductases

Ethylene is a key molecule in organic synthesis currently produced by steam cracking of fossil hydrocarbons. In nature, ethylene is produced in higher plants by 1-aminocyclopropane-1-carboxylic acid oxidase (ACCO). Biocatalytic alternatives for ethylene production are still far from being competitive with traditional production plants. Furthermore, data dispersion shown in the literature adds uncertainty to the introduction of ACCO as a biocatalyst, especially when larger numbers of isoforms or mutants are to be compared. Here we propose a new method for measuring ACCO activity based on cyanide detection. Data provided here indicate that cyanide detection is more precise, more responsive, and much more stable than any other method tested for ACCO activity estimation so far. Briefly, enzymatically produced cyanide can be detected by its derivatization with naphthalene-2,3-dicarboxyaldehide (NDA) to generate 1-cyanobenz[f]isoindole (CBI), which is further detected by high-performance liquid chromatography (HPLC) coupled with a fluorescence detector. Cyanide can be detected in the range between 0.99 and 60.17 pmol, which is three orders of magnitude more sensitive than the currently used ethylene estimation method.     

Common fronto-temporal effective connectivity in humans and monkeys

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