PubMed · 11010979
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M Markowitz. 2000. Lead poisoning.. https://doi.org/10.1542/pir.21-10-327
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Two light-induced growth reactions in a unicellular cylindrical sporangiophore of Phycomyces blakesleeanus-vertical growth acceleration under symmetrical irradiation (photomecism) and directional growth under unilateral irradiation (phototropism)-share common input light perception as well as common output growth mechanism but have strongly divergent dynamics and other distinctive features. This divergence culminates in the phototropic paradoxes the main of which states that photomecism shows total adaptation, while phototropism does not adapt. The basis for this contradiction is that the phototropic transduction chain, unlike that of photomecism, faces a spatially non-uniform stimulus and processes a series of spatial patterns (light and absorption profiles, adaptation profile, etc.). The only way to resolve the paradoxes and correlate features of both responses within a single transduction chain is to assume non-local signal transduction, e.g. a cross-talk between different azimuthal locations within the cylindrical cell. On the other hand, to establish the presence of an appropriate cross-talk is equivalent of gaining insight into the topology of the transduction chain. This series of two papers contains a review reconsidering the entire field from this viewpoint (Paper 1) and a mathematical model of pattern transduction which unifies features of phototropism and resolves the paradoxes (Paper 2). At the same time, this is the first "proof of concept" for the "activity/pooling (a/p) networks"-a specific mathematical apparatus designed to analyse systemic properties and control in metabolic pathways.
Many aquatic turtles possess paired evaginations of the cloaca called cloacal bursae. Despite more than two centuries of study, little consensus exists as to the function(s) of these organs. We tested a recent suggestion that bursae could function in water uptake ("cloacal drinking"). Turtles (Trachemys scripta) were dehydrated (68-86% of maximum body mass) and given the opportunity to drink orally or cloacally. Dehydration caused increases in hematocrit and osmolality of extracellular fluid (ECF), but only after loss of 10-12% of maximum body mass, suggesting that turtles osmoregulated by reabsorbing water from the urinary bladder. Turtles drank eagerly when they could submerge their heads, and drinking was accompanied by an increase in body mass and a decrease in ECF osmolality. However, dehydrated turtles with tail and anus submerged showed no changes in mass or osmolality, suggesting that water absorption is not a significant function of the cloacal bursae in this species. Evidence for other putative functions is reviewed, leading to a pluralistic view: in cryptodires, bursae apparently function primarily in buoyancy control and secondarily in ion transport and nesting, but several pleurodires have been shown recently to use them in aquatic respiration.
The binding of TNT to a soil and soil components is studied with 2H MAS NMR. This NMR technique clearly shows different interactions for deuterated TNT with soil, quartz, and clays. Basically, this NMR method relies on the well-defined 2H MAS NMR characteristics of a deuterated methyl group attached to an aromatic ring. Stationary rings and rings executing 2- or 3-fold jump motions all yield different NMR spectra. The technique has good sensitivity; these studies were conducted at a TNT loading of 22 mmol/kg. For the soil sample studied, TNT showed binding similar to a TNT/K10-montmorillonite sample.