Reproductive biology of the nonnative oyster, Crassostrea gigas (Thunber, 1793) as a key for its successful spread along the rocky shores of Northern Patagonia, Argentina

Crassostrea gigas was introduced in Anegada Bay (North Patagonia, Argentina), in 1981 for aquaculture purposes. The species has, since established in the field, covered all available hard substrata in the bay and gradually expanded south along the coast of the neighboring province of Río Negro, 90 km away from its original introduction site. Our work focused on the reproductive dynamics of the species at the introduction site, with emphasis on the thermal thresholds needed for each stage of gonad development. During early spring, the oysters in Anegada Bay go through active gonad proliferation. Maturity extends mainly from October to January. The first spawning occurs in November, when seawater temperature exceeds 17°C, and peaks from December to February, when seawater temperature lies in the range ot 19–21.5°C. The timing of gonad development is size dependent. Larger (≥70 mm) and medium-size oysters begin spawning first, whereas small oysters ( 17°C), and spawning only occurs in those sites where this threshold is reached.Versión del editor

The X-Ray Crystal Structure of Escherichia coli Succinic Semialdehyde Dehydrogenase; Structural Insights into NADP+/Enzyme Interactions

In mammals succinic semialdehyde dehydrogenase (SSADH) plays an essential role in the metabolism of the inhibitory neurotransmitter gamma-aminobutyric acid (GABA) to succinic acid (SA). Deficiency of SSADH in humans results in elevated levels of GABA and gamma-Hydroxybutyric acid (GHB), which leads to psychomotor retardation, muscular hypotonia, non-progressive ataxia and seizures. In Escherichia coli, two genetically distinct forms of SSADHs had been described that are essential for preventing accumulation of toxic levels of succinic semialdehyde (SSA) in cells.Here we structurally characterise SSADH encoded by the E coli gabD gene by X-ray crystallographic studies and compare these data with the structure of human SSADH. In the E. coli SSADH structure, electron density for the complete NADP+ cofactor in the binding sites is clearly evident; these data in particular revealing how the nicotinamide ring of the cofactor is positioned in each active site.Our structural data suggest that a deletion of three amino acids in E. coli SSADH permits this enzyme to use NADP+, whereas in contrast the human enzyme utilises NAD+. Furthermore, the structure of E. coli SSADH gives additional insight into human mutations that result in disease

Benign external hydrocephalus: a review, with emphasis on management

Benign external hydrocephalus in infants, characterized by macrocephaly and typical neuroimaging findings, is considered as a self-limiting condition and is therefore rarely treated. This review concerns all aspects of this condition: etiology, neuroimaging, symptoms and clinical findings, treatment, and outcome, with emphasis on management. The review is based on a systematic search in the Pubmed and Web of Science databases. The search covered various forms of hydrocephalus, extracerebral fluid, and macrocephaly. Studies reporting small children with idiopathic external hydrocephalus were included, mostly focusing on the studies reporting a long-term outcome. A total of 147 studies are included, the majority however with a limited methodological quality. Several theories regarding pathophysiology and various symptoms, signs, and clinical findings underscore the heterogeneity of the condition. Neuroimaging is important in the differentiation between external hydrocephalus and similar conditions. A transient delay of psychomotor development is commonly seen during childhood. A long-term outcome is scarcely reported, and the results are varying. Although most children with external hydrocephalus seem to do well both initially and in the long term, a substantial number of patients show temporary or permanent psychomotor delay. To verify that this truly is a benign condition, we suggest that future research on external hydrocephalus should focus on the long-term effects of surgical treatment as opposed to conservative management