Studies on the nutrition of Arthrobotrys oligospora Fres. and A. robusta Dudd: The predaceous phase

The effects of substrate on the predaceous activity in sand cultures of two isolates of the genus Arthrobotrys were measured by expressing the number of non-survivors of a free-living nematode population exposed to the fungi for 4 days as a percentage of a comparable population of nematodes not exposed to predation. This percentage is designated the predacity number. By varying the energy source it was shown that nutrient requirements for the extension of mycelium may differ from those for the expression of predacity. There is a greater reduction in the activity of A. oligospora when nitrogen is supplied as ammonium than when it is presented as nitrate or nitrite. The predacity of A. robusta is greatest on media deficient in biotin and with nitrite as nitrogen source. The relationship of results derived from artificial cultures to results from more direct examination of soils is discussed.     

The active transport of Mg++ and Mn++ into the yeast cell

Certain bivalent cations, particularly Mg⁺⁺ and Mn⁺⁺, can be absorbed by yeast cells, provided that glucose is available, and that phosphate is also absorbed. The cation absorption is stimulated by potassium in low concentrations, but inhibited by higher concentrations. From the time course studies, it is apparent that the absorption rather than the presence of phosphate and the potassium is the important factor. Competition studies with pairs of cations indicate that binding on the surface of the cell is not a prerequisite to absorption. The absorption mechanism if highly selective for Mg⁺⁺ and Mn⁺⁺, as compared to Ca⁺⁺, Sr⁺⁺, and UO₂⁺⁺, whereas the binding affinity is greatest for UO₂⁺⁺, with little discrimination between Mg⁺⁺, Ca⁺⁺, Mn⁺⁺, and Sr⁺⁺. In contrast to the surface-bound cations which are completely exchangeable, the absorbed cations are not exchangeable. It is concluded that Mg⁺⁺ and Mn⁺⁺ are actively transported into the cell by a mechanism involving a phosphate and a protein constituent.     

Neurotransmitter alterations in embryonic succinate semialdehyde dehydrogenase (SSADH) deficiency suggest a heightened excitatory state during development

Background  

SSADH (aldehyde dehydrogenase 5a1 (Aldh5a1); γ-hydroxybutyric (GHB) aciduria) deficiency is a defect of GABA degradation in which the neuromodulators GABA and GHB accumulate. The human phenotype is that of nonprogressive encephalopathy with prominent bilateral discoloration of the globi pallidi and variable seizures, the latter displayed prominently in Aldh5a1^-/- mice with lethal convulsions. Metabolic studies in murine neural tissue have revealed elevated GABA [and its derivatives succinate semialdehyde (SSA), homocarnosine (HC), 4,5-dihydroxyhexanoic acid (DHHA) and guanidinobutyrate (GB)] and GHB [and its analogue D-2-hydroxyglutarate (D-2-HG)] at birth. Because of early onset seizures and the neurostructural anomalies observed in patients, we examined metabolite features during Aldh5a1^-/- embryo development.     

Six new microsatellite markers for the toxic marine dinoflagellate Alexandrium tamarense

We report the characterization of six new microsatellite loci for the toxic marine dinoflagellate Alexandrium tamarense (North American ribotype), using 56 isolates from a range of locations. The numbers of alleles per locus ranged from five to nine and gene diversities ranged from 0.041 to 0.722. We tested primers for these six loci on other A. tamarense ribotypes and on other Alexandrium species; the results suggest that the primers are specific to A. tamarense isolates belonging to the North American ribotype.