Timing and magnitude of C partitioning through a young loblolly pine (Pinus taeda L.) stand using 13C labeling and shade treatments

The dynamics of rapid changes in carbon (C) partitioning within forest ecosystems are not well understood, which limits improvement of mechanistic models of C cycling. Our objective was to inform model processes by describing relationships between C partitioning and accessible environmental or physiological measurements, with a special emphasis on short-term C flux through a forest ecosystem. We exposed eight 7-year-old loblolly pine (Pinus taeda L.) trees to air enriched with (13)CO(2) and then implemented adjacent light shade (LS) and heavy shade (HS) treatments in order to manipulate C uptake and flux. The impacts of shading on photosynthesis, plant water potential, sap flow, basal area growth, root growth and soil CO(2) efflux rate (CER) were assessed for each tree over a 3-week period. The progression of the (13)C label was concurrently tracked from the atmosphere through foliage, phloem, roots and surface soil CO(2) efflux. The HS treatment significantly reduced C uptake, sap flow, stem growth and fine root standing crop, and resulted in greater residual soil water content to 1 m depth. Soil CER was strongly correlated with sap flow on the previous day, but not the current day, with no apparent treatment effect on the relationship. Although there were apparent reductions in new C flux belowground, the HS treatment did not noticeably reduce the magnitude of belowground autotrophic and heterotrophic respiration based on surface soil CER, which was overwhelmingly driven by soil temperature and moisture. The (13)C label was immediately detected in foliage on label day (half-life = 0.5 day), progressed through phloem by Day 2 (half-life = 4.7 days), roots by Days 2-4, and subsequently was evident as respiratory release from soil which peaked between Days 3 and 6. The δ(13)C of soil CO(2) efflux was strongly correlated with phloem δ(13)C on the previous day, or 2 days earlier. While the (13)C label was readily tracked through the ecosystem, the fate of root C through respiratory, mycorrhizal or exudative release pathways was not assessed. These data detail the timing and relative magnitude of C flux through various components of a young pine stand in relation to environmental conditions.     

Effect of an extruded pea or rice diet on postprandial insulin and cardiovascular responses in dogs

Peas are increasing in popularity as a source of carbohydrate, protein and fibre in extruded canine diets. The aim of this study was to test the health effects of two canine diets with identical macronutrient profiles, but containing either yellow field peas or white rice as the carbohydrate source on metabolism, cardiovascular outcomes and adiposity. First, the acute glycemic, insulinemic and cardiovascular responses to the pea‐ or rice‐based diets were determined in normal weight beagles (n = 7 dogs). The glycemic index did not differ between the pea diet (56 ± 12) and rice diet (63 ± 9). Next, obese beagles (n = 9) were fed the yellow field pea diet or white rice diet ad libitum for 12 weeks in a crossover study. Adiposity (measured using computed tomography), metabolic (oral glucose tolerance test, plasma leptin, adiponectin, C‐reactive protein) and cardiovascular assessments (echocardiography and blood pressure) were performed before and after each crossover study period. After 12 weeks on each diet, peak insulin (p = 0.05) and area under the curve (AUC) for insulin after a 10 g oral glucose tolerance test (p = 0.05) were lower with the pea than the rice diet. Diet did not show a significant effect on body weight, fat distribution, cardiovascular variables, adiponectin or leptin. In conclusion, a diet containing yellow field peas reduced the postprandial insulin response after glucose challenge in dogs despite continued obesity, indicating improved metabolic health.     

Movement of aluminium as an inorganic complex in some podzolised soils,New Zealand

Chemical and mineralogical data are presented for three Spodosols (podzols) and a related Inceptisol (yellow-brown loam). Allophane with an Al/Si atomic ratio close to two is identified in the B horizons of all four soils, and minor amounts of imogolite are present in association with allophane in all but one soil where small-particle gibbsite occurs. Parent materials for these soils are essentially non-vitric. Allophane (Al/Si = 2) has been estimated quantitatively in all soils using oxalate-extractable Si (Si₀) and is selected clay fractions using both Si₀ and infrared spectroscopy. Maximum concentrations of allophane (Al/Si = 2) range from 5% to 18% of fine earth (< 2 mm) fractions and all occur in B horizons. Fe₀ values are low relative to Al₀ values except for the upper horizons of the Inceptisol. Al₀ values peak in B horizons and the ratio pyrophosphate-extractable Al to Al₀ decreases from about 1 in A and upper B horizons to 0.1–0.4 in lower B horizons.An interpretation of the data is consistent with recent proposals that the movement of Al in podzolisation is due primarily to the formation of inorganic complexes with Si. Chemical criteria for spodic horizons should be consistent with the total illuviation of Al and Fe (and perhaps Si), rather than just the organic-bound fraction of Al and Fe in these horizons as indicated by amounts in extractants such as pyrophosphate.     

Synaptic transmission between dissociated adult mammalian neurons and attached synaptic boutons

In most studies of synaptic currents in mammalian central neurons, preparations have been used in which synaptic currents are recorded at some distance from the synapse itself. This procedure introduces problems in interpretation of the kinetics and voltage-dependent properties of the synaptic current. These problems have now been overcome by the development of a preparation in which presynaptic vesicle-containing boutons have been coisolated with the soma of individual neurons, thus providing the opportunity to study synaptic currents under conditions of both adequate voltage control and internal ionic perfusion. Spontaneous synaptic currents mediated by gamma-aminobutyric acid and excitatory amino acids were recorded from neurons isolated from a mammalian medial solitary tract nucleus. Calcium- and depolarization-dependent spontaneous currents of several to hundreds of picoamperes occurred with rapid rise times of 0.8 to 3 milliseconds and decays at least ten times as long.     

Rabies surveillance in the United States during 2000.

During 2000, 49 states, the District of Columbia, and Puerto Rico reported 7,364 cases of rabies in nonhuman animals and 5 cases in human beings to the Centers for Disease Control and Prevention, an increase of 4.3% from 7,067 cases in nonhuman animals reported in 1999. Ninety-three percent (6,855 cases) were in wild animals, whereas 6.9% (509 cases) were in domestic species (compared wth 91.5% in wild animals and 8.5% in domestic species in 1999). Compared with cases reported in 1999, the number of cases reported in 2000 increased among bats, dogs, foxes, skunks, and sheep/goats and decreased among cats, cattle, horses/mules, raccoons, and swine. The relative contributions of the major groups of animals were as follows: raccoons (37.7%; 2,778 cases), skunks (30.2%; 2,223), bats (16.8%; 1,240), foxes (6.2%; 453), cats (3.4%; 249), dogs (1.6%; 114), and cattle (1.1%; 83). Ten of the 19 states where the raccoon-associated variant of the rabies virus has been enzootic reported increases in the numbers of cases of rabies during 2000. Among those states that have engaged in extensive wildlife rabies control programs, no cases of rabies associated with the epizootic of rabies in raccoons (or in any other terrestrial species) were reported in Ohio, compared with 6 cases reported in 1999. No rabies cases associated with the dog/coyote variant (compared with 10 cases in 1999, including 5 in dogs) were reported in Texas, and cases associated with the gray fox variant of the virus decreased (58 cases in 2000, including 38 among foxes). Reports of rabid skunks exceeded those of rabid raccoons in Massachusetts and Rhode Island, states with enzootic raccoon rabies, for the fourth consecutive year. Nationally, the number of rabies cases in skunks increased by 7.1% from that reported in 1999. The greatest numerical increase in rabid skunks (550 cases in 2000, compared with 192 in 1999) was reported in Texas. The number of cases of rabies reported in bats (1,240) during 2000 increased 25.4% over the number reported during 1999 (989) and represented the greatest contribution (16.8% of the total number of rabid animals) ever recorded for this group of mammals. Cases of rabies reported in cattle (83) and cats (249) decreased by 38.5% and 10.4%, respectively, whereas cases in dogs (114) increased by 2.7% over those reported in 1999. Reported cases of rabies among horses and mules declined 20% from 65 cases in 1999 to 52 cases in 2000. Four indigenously acquired cases of rabies reported in human beings were caused by variants of the rabies virus associated with bats. One case of human rabies acquired outside the United States that resulted from a dog bite was caused by the canine variant of the rabies virus.     

Patterns of alkaline phosphatase in developing Drosophila

Electrophoretic study of alkaline phosphatase in developing Drosophila shows that different stages are characterized by the appearance and disappearance of organ-specific enzyme bands. A new electrophoretic variant, from adult hindgut, is controlled by the second chromosome locus Aph-2.     

Long chain n-3 polyunsaturated fatty acid concentration and color and lipid stability of muscle from heifers offered a ruminally protected fish oil supplement

Beef heifers (n = 48) were offered, daily, a 1.5 kg ration that contained 0, 69, 138, and 275 g of ruminally protected fish oil (RPFO) fortified with vitamin E (5000 IU/kg). The fatty acid profile of neutral (NL) and polar lipids (PL) of neck muscle was analyzed by GC-FID. Minced muscle was displayed in an 80% O(2):20% CO(2) atmosphere under simulated retail display conditions. Muscle α-tocopherol concentrations did not differ. For PL, the proportions of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) increased (P < 0.05, linearly and quadratically, respectively). For NL, the proportion of EPA was not affected but DHA increased linearly and quadratically (P < 0.05). Supplementation did not affect color stability of ground beef, but lipid oxidation was higher (P < 0.001) for 275 g of RPFO on day 10 of display. In conclusion, supplementation with RPFO increased muscle EPA and DHA with no effect on color stability while lipid oxidation was increased only at the highest level of supplementation, after prolonged display.     

Solar neutrinos: proposal for a new test

The predicted flux on the earth of solar neutrinos has eluded detection, confounding current ideas of solar energy production by nuclear fusion. The dominant low-energy component of that flux can be detected by mass-spectrometric assay of the induced tiny concentration of 1.6 x 10(7) year lead-205 in old thallium minerals. Comments are solicited from those in all relevant disciplines.