A Temporally Explicit Production Efficiency Model for Fuel Load Allocation in Southern Africa

Abstract We present a regional fuel load model (1 km² spatial resolution) applied in the southern African savanna region. The model is based on a patch-scale production efficiency model (PEM) scaled up to the regional level using empirical relationships between patch-scale behavior and multi-source remote sensing data (spatio-temporal variability of vegetation and climatic variables). The model requires the spatial distribution of woody vegetation cover, which is used to determine separate respiration rates for tree and grass. Net primary production, grass and tree leaf death, and herbivory are also taken into account in this mechanistic modeling approach. The fuel load model has been calibrated and validated from independent measurements taken from savanna vegetation in Africa southward from the equator. A sensitivity analysis on the effect of climate variables (incoming radiation, air temperature, and precipitation) has been conducted to demonstrate the strong role that water availability has in determining productivity and subsequent fuel load over the southern African region. The model performance has been tested in four different areas representative of a regional increasing rainfall gradient—Etosha National Park, Namibia, Mongu and Kasama, Zambia, as well as in Kruger National Park, South Africa. Within each area, we analyze model output from three different magnitudes of canopy coverage (<5, 30, and 50%). We find that fuel load ranges predicted by the model are globally in agreement with field measurements for the same year. High rainfall sustains green herbaceous production late in the dry season and delays tree leaf litter production. Effect of water on production varies across the rainfall gradient with delayed start of green material production in more arid regions.     

A molecular genetic linkage map of mouse chromosome 18 reveals extensive linkage conservation with human chromosomes 5 and 18

An interspecific backcross between C57BL/6J and Mus spretus was used to generate a molecular genetic linkage map of mouse chromosome 18 that includes 23 molecular markers and spans approximately 86% of the estimated length of the chromosome. The Apc, Camk2a, D18Fcr1, D18Fcr2, D18Leh1, D18Leh2, Dcc, Emb-rs3, Fgfa, Fim-2/Csfmr, Gnal, Grl-1, Grp, Hk-1rs1, Ii, Kns, Lmnb, Mbp, Mcc, Mtv-38, Palb, Pdgfrb, and Tpl-2 genes were mapped relative to each other in one interspecific backcross. A second interspecific backcross and a centromere-specific DNA satellite probe were used to determine the distance of the most proximal chromosome 18 marker to the centromere. The interspecific map extends the known regions of linkage homology between mouse chromosome 18 and human chromosomes 5 and 18 and identifies a new homology segment with human chromosome 10p. It also provides molecular access to many regions of mouse chromosome 18 for the first time.     

Mouse Chromosome 13

Chair of Committee for Mouse Chromosome 13     

Oxalate digestibility in Neotoma albigula and Neotoma mexicana

Summary The cactus specialist, Neotoma albigula, tolerates high concentrations of potentially harmful oxalate compounds in its diet. Previous research has shown that oxalate compounds are broken down by intestinal micro-organisms. Thus the ability of N. albigula to utilize a diet high in oxalates may be a consequence of the adaptation of the microflora rather than its own evolution. To test this hypothesis, the oxalate degradation ability of N. albigula was compared with that of N. mexicana, a generalist herbivore. Apparent oxalate digestibility was not significantly different in the two species, when tested using field-acclimated individuals. Analysis of scats recovered from traps indicated that both species were consuming oxalates in the wild. I conclude that the ability of these herbivores to tolerate oxalates is a natural consequence of the utilization of microbial fermentation to degrade the structural carbohydrates of plants coupled with the high adaptive and evolutionary potential of the microflora.     

A 9.6 S protein is the third calcium-insoluble component of the sea urchin hyaline layer.

A third major, calcium-insoluble component of the sea urchin (Strongylocentrotus purpuratus) hyaline layer has been purified and physically characterized. In the absence of divalent cations, the native, soluble protein has a sedimentation coefficient of 9.6 S and a molecular weight of 4.5 +/- 0.1 x 10(5). These data indicate that this large protein assumes an elongated, nonspherical conformation in solution. Its sedimentation behavior and its mobility on nondenaturing electrophoretic gels distinguish the 9.6 S protein from the 11.6 S and 6.4 S hyalin proteins we have previously characterized. That the 6.4 S, 9.6 S, and 11.6 S proteins are the major calcium-insoluble structural components of the hyaline layer is supported by the fact that we have found them in a variety of hyalin protein fractions prepared by a number of standard approaches. All three proteins are precipitated by calcium ions, thus fitting the operational definition of hyalin. Evidence is presented that the 11.6 S protein may overlie the 9.6 S protein in the hyaline layer.     

Phylogenetic diversification of immunoglobulin genes and the antibody repertoire

Immunoglobulins are encoded by a large multigene system that undergoes somatic rearrangement and additional genetic change during the development of immunoglobulin-producing cells. Inducible antibody and antibody-like responses are found in all vertebrates. However, immunoglobulin possessing disulfide-bonded heavy and light chains and domain-type organization has been described only in representatives of the jawed vertebrates. High degrees of nucleotide and predicted amino acid sequence identity are evident when the segmental elements that constitute the immunoglobulin gene loci in phylogenetically divergent vertebrates are compared. However, the organization of gene loci and the manner in which the independent elements recombine (and diversify) vary markedly among different taxa. One striking pattern of gene organization is the "cluster type" that appears to be restricted to the chondrichthyes (cartilaginous fishes) and limits segmental rearrangement to closely linked elements. This type of gene organization is associated with both heavy- and light-chain gene loci. In some cases, the clusters are "joined" or "partially joined" in the germ line, in effect predetermining or partially predetermining, respectively, the encoded specificities (the assumption being that these are expressed) of the individual loci. By relating the sequences of transcribed gene products to their respective germ-line genes, it is evident that, in some cases, joined-type genes are expressed. This raises a question about the existence and/or nature of allelic exclusion in these species. The extensive variation in gene organization found throughout the vertebrate species may relate directly to the role of intersegmental (V<==>D<==>J) distances in the commitment of the individual antibody-producing cell to a particular genetic specificity. Thus, the evolution of this locus, perhaps more so than that of others, may reflect the interrelationships between genetic organization and function.      

Therapeutic Role of Fibroblast Growth Factor 21 (FGF21) in the Amelioration of Chronic Diseases

International Journal of Peptide Research and Therapeutics - Fibroblast growth factor-21 (FGF21) is a member of the family of fibroblast growth factors (FGFs). FGF21 (synthesized by many organs)...