Mineral cycling in a tropical palm forest

Nutrient cycling and biomass characteristics of a tropical palm forest dominated byOrbignya cohune were found to be different from thsoe of hardwood dominated forests. The cohune palm forest had a high proportion of biomass in leaves (5%), a reduced sapling layer, a large amount of standing forest litter and an exceptionally low decomposition rate factor (0.1 year^–1). Mineral concentrations in palm leaves were generally lower than in hardwood species with the exception of Na, which was exceptionally high inOrbignya cohune. Biomass was estimated at 226 tons ha^–1 containing 1173 kg ha^–1 N; 126 kg ha^–1 P; 437 kg ha^–1 K; 1869 kg ha^–1 Mg; 125 kg ha^–1 Ca, and 2177 kg ha^–1 Na. Soils of cohune association did not differ significantly from those of neighbouring hardwood dominated associations with the exception of Na which occurred in higher concentration because of bioaccumulation in the dominant. The results suggest that the growth habits and physiology of a dominant can strongly influence some of the ecological parameters used to describe aforest association.     

Nitrogen distribution in hybrid and local corn varieties and its possible relationship to a declining soil nitrogen pool under shifting agriculture at Indian Church,Belize

Nitrogen levels at harvest in hybrid corn and weeds were determined over a three year period. Nitrogen losses due to grain removal accounted for 45% of all assimilated-N in the milpa. Percent N and percent P levels in the hybrid and a local black corn were also determined. Uptake of nitrogen and phosphorus in roots and leaves of both varieties were sigmoid until reproductive growth was initiated, at which time the percentage of both nutrients in the leaves declined rapidly. Levels in the seed at maturity in the hybrid variety accounted for 78% N and 52% P; levels were 58% N and 50% P in the local corn. Hybrid corn was not considered suitable for local farmers because a high percentage of total-N was removed at harvest and the hybrid had a high susceptibility to weevil attack.     

Molecular size of nerve growth factor in dilute solution.

Nerve growth factor (NGF) is a protein composed of two identical chains of mass 13,259. An analysis of the sedimentation equilibrium, sedimentation velocity, and gel filtration behavior of dilute solutions of NGF indicates the existence of a rapidly reversible monomer in equilibrium dimer equilibrium and that the association constant K for the reaction at neutral pH is 9.4 X 10(6)M-1. Reaction mixtures consist of equal concentrations of monomer and dimer at a total protein concentration as high as 1.4 mug/ml, and at 1 ng/ml, monomer accounts for greater than 99% of the total. The latter concentration is 20 to 30 times that required for the biological activity of NGF. Several lines of evidence suggest that the dimerization reaction is highly stereospecific, although its biological significance is not known.     

Five batches representative of Ontario-grown American ginseng root produce comparable reductions of postprandial glycemia in healthy individuals

Evidence indicates that the glycemia-lowering effect of American ginseng root may be batch dependent. We therefore evaluated the effect of 5 root batches, representative of Ontario-grown American ginseng, on postprandial glucose and insulin indices. Twelve healthy subjects (5 male, 7 female), mean +/- SE age 26.5 +/- 2 years, body mass index 23.96 +/- 3.41 kg/m2, fasting blood glucose 4.77 +/- 0.04 mmol/L, were assigned to consume 9 g of American ginseng from 5 farms (A-E), administered in randomized sequence on 5 separate visits, and a water-control during the 6th and last visit. Treatments were consumed 40 min before a 2-hour 75-gram oral glucose tolerance test. Plasma glucose and insulin were measured at baseline, before, and during the test. Compared with control, batches A and C reduced glucose incremental area under the curve (IAUC) by 35.2% (156 vs. 240 mmol.min/L) and 32.6% (162 vs. 240 mmol.min/L), respectively. Batches A, C, and E reduced incremental peak glucose by 1.3, 1.2, and 1.1 mmol/L, respectively. Batch C reduced the insulin IAUC by 27.7% (15.8 vs. 21.8 nmol.min/L). Effects on glucose and insulin parameters were not different across ginseng treatments. The mean of the 5 ginseng treatments reduced peak postprandial glucose by 1.0 mmol/L, glucose IAUC by 27.7% (173 vs. 240 mmol.min/L), and insulin IAUC by 23.8% (16.6 vs. 21.8 nmol.min/L) relative to control. (All results statistically significant at p < 0.05.) American ginseng decreased postprandial glycemia and insulinemia; however, 40% of the batches did not reduce glycemia with the anticipated magnitude, irrespective of their saponin composition.     

Functional and antigenic characterization of human, rhesus macaque, pigtailed macaque, and murine DC-SIGN

DC-SIGN, a type II membrane protein with a C-type lectin binding domain that is highly expressed on mucosal dendritic cells (DCs) and certain macrophages in vivo, binds to ICAM-3, ICAM-2, and human and simian immunodeficiency viruses (HIV and SIV). Virus captured by DC-SIGN can be presented to T cells, resulting in efficient virus infection, perhaps representing a mechanism by which virus can be ferried via normal DC trafficking from mucosal tissues to lymphoid organs in vivo. To develop reagents needed to characterize the expression and in vivo functions of DC-SIGN, we cloned, expressed, and analyzed rhesus macaque, pigtailed macaque, and murine DC-SIGN and made a panel of monoclonal antibodies (MAbs) to human DC-SIGN. Rhesus and pigtailed macaque DC-SIGN proteins were highly similar to human DC-SIGN and bound and transmitted HIV type 1 (HIV-1), HIV-2, and SIV to receptor-positive cells. In contrast, while competent to bind virus, murine DC-SIGN did not transmit virus to receptor-positive cells under the conditions tested. Thus, mere binding of virus to a C-type lectin does not necessarily mean that transmission will occur. The murine and macaque DC-SIGN molecules all bound ICAM-3. We mapped the determinants recognized by a panel of 16 MAbs to the repeat region, the lectin binding domain, and the extreme C terminus of DC-SIGN. One MAb was specific for DC-SIGN, failing to cross-react with DC-SIGNR. Most MAbs cross-reacted with rhesus and pigtailed macaque DC-SIGN, although none recognized murine DC-SIGN. Fifteen of the MAbs recognized DC-SIGN on DCs, with MAbs to the repeat region generally reacting most strongly. We conclude that rhesus and pigtailed macaque DC-SIGN proteins are structurally and functionally similar to human DC-SIGN and that the reagents that we have developed will make it possible to study the expression and function of this molecule in vivo.     

HPLC-PAD-APCI/MS assay of phenylpropanoids in cereals

A new, rapid HPLC-PAD-APCI/MS assay has been developed in order to measure accurately the amount of p-coumaric, E- and Z-ferulic acid and the dehydrodimers of ferulic acid in cereal grain. In the positive ionisation mode, MS patterns gave additional information for the identification of the dimers. The time required and the quantities of solvents employed in the developed analytical method are much lower than those involved in previously available assays of these compounds, thus making the method suitable for the screening of cereal genotypes. Application of the method to accessions of maize, wheat and sorghum showed that E-ferulic was the most abundant phenylpropanoid, whilst the major dimer was 8-O-4' dehydrodimer of ferulic acid followed by the 5-5' and then the 8-5' forms. Maize grains, especially of the Mexican landraces, contained the highest levels of these dimers.     

Marsupial relationships and a timeline for marsupial radiation in South Gondwana

Recent marsupials include about 280 species divided into 18 families and seven orders. Approximately 200 species live in Australia/New Guinea. The remaining species inhabit South America with some of these secondarily ranging into North America. In this study, we examine marsupial relationships and estimate their divergences times using complete mitochondrial (mt) genomes. The sampling, which includes nine new mtDNAs and a total number of 19 marsupial genomes, encompasses all extant orders and 14 families. The analysis identified a basal split between Didelphimorphia and remaining orders about 69 million years before present (MYBP), while other ordinal divergences were placed in Tertiary times. The monotypic South American order Microbiotheria (Dromiciops gliroides, Monito del Monte) was solidly nested among its Australian counterparts. The results suggest that marsupials colonized Australia twice from Antarctica/South America and that the divergence between Microbiotheria and its Australian relatives coincided with the geological separation of Antarctica and Australia. Within Australia itself, several of the deepest divergences were estimated to have taken place close to the Eocene/Oligocene transition.     

Extent of mitochondrial DNA sequence variation in Atlantic cod from the Faroe Islands: a resolution of gene genealogy

Variation in a 250 base pair (bp) fragment of the mitochondrial cytochrome b (cyt b) has been used extensively for population studies in Atlantic cod Gadus morhua. To study the shape of the gene genealogy and the nature of the polymorphism, sequences of another region of the cyt b gene and the TP intergenic spacer were added, making a total of 566 bp from 74 cod from the Faroe Islands. A total of 44 segregating sites defined 41 haplotypes, many at frequencies greater than 5%. Haplotype diversity was 0.97 and nucleotide diversity 0.73% per base. A topology referred to as a constellation gene genealogy was observed with four major haplotypes at high frequencies, from each of which a number of rare variants were derived. A young relative age of the haplotypes was gauged from the structure of the genealogy. The variation was mostly at synonymous sites within the coding region and thus likely to be neutral or under weak purifying selection. By comparative analysis this also applies to the TP spacer. Applying the locus to study population variation in the Faroe Islands by AMOVA revealed that the overall areas and localities within areas accounted for none of the variation, and all the variation was due to differences among individuals.