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.     

Isoforms of myosin and actin in human, monkey and rat myometrium. Comparison of pregnant and non-pregnant uterus proteins

Using several electrophoretic procedures, we have compared the forms of myosin and actin in pregnant and non-pregnant uterus of woman, monkey (Macaca fascicularis) and rat. On non-dissociating gels, native myosin of the three species migrates as a single band, of identical mobility independently of the physiological state. Remigration of this band in dissociating conditions shows that it is constituted of two heavy chains of respectively 201 kDa and 205 kDa; the relative proportions of these two bands are different for the three animal species but do not vary during pregnancy. Using two-dimensional gel electrophoresis, we found that the 17-kDa light chain of purified uterus myosin exists under two isoelectric forms, the more acidic one becoming progressively predominant at the end of pregnancy in the human as in the monkey uterus, while we observed no changes in the rat. In two-dimensional gel electrophoresis, actin of human, monkey and rat uterus is present under three isoforms, the most basic one (the gamma form) increasing early in pregnancy in the two primate species but being always the most abundant form in the rat. The ATPase activity of human uterus myosin was found to be similar for the protein extracted from both pregnant and non-pregnant uterus. The changes observed in the 17-kDa light chain and in the actin isoforms might nevertheless participate in the modifications of contractility of the uterus during pregnancy of the primates.     

Quantitative analysis of the temporal pattern of somite formation in the mouse and rat. A simple and accurate method for age determination

The relation between the logarithm of the volume of the embryo and the number of somites was studied in the mouse and rat in the period of about 0-43 somites, a period characterized by a very rapid volume increase. A linear relation was found, and the variability of the individual observations around the straight line was rather small. Using a previously defined age estimate, i.e. the 'developmental age' based on the embryonic volume, we also found a linear relation between this age estimate and the number of somites. With the help of this straight line, the developmental age can be estimated from the number of somites with an accuracy of less than 0.1 day. Therefore, the developmental age can be considered a better age estimate than those based on the usual methods. The time needed to form a new somite was found to be constant in both species during the period studied. The length of the period differed, and was 1.68 h in the mouse and 2.24 h in the rat. However, the volume of the embryo at the time when a specific somite was formed (for instance the 25th) appeared to be the same in both species. Comparison of the volume of embryos, embedded in paraffin and Epon and sectioned, enabled us to estimate the shrinkage in Epon embryos. The volume after processing was approximately 62% of the original volume.     

Environmental regulation of surface conductance for evaporation from vegetation

We examine conductances for evaporation from both vegetation and soil in response to environmental variables. Data from a vertically-structured pristine forest of Nothofagus are presented as an example of the effects of biodiversity on the scaling of conductances between tiers of plant organisation. Available data sets of maximum leaf stomatal conductances (g _lmax ) and bulk vegetation surface conductances (G _smax ) are compared. Overall, the ratio G _smax /g _lmax is consistently close to 3 for seven major vegetation types of diverse structure. An analytical model accounts for this close relationship, and in particular how G _smax is conservative against changes in leaf area index because of the compensating decrease in plant canopy transpiration and increase in soil evaporation as leaf area index diminishes. The model is also successfully tested by comparison with canopy conductances of emergent trees measured in the Nothofagus forest. The constraint of vegetation surface conductance and evaporation via environmental regulation by irradiance, air saturation deficit and root zone water supply are discussed.     

Application of a new slot comb to electrophoretic analysis.

In the present experiment, a new slot comb was designed in order to form a wide and sloped sample well on the stacking gel of electrophoresis. Using this slot comb, a gradient of the reagent layer of interest can be easily formed transversely on the gel that is perpendicular to the direction of electrophoresis. Thus, the protein sample overlaid on the agent migrates across the gradient layer during electrophoresis to produce a continuous electrophoretic band reflecting the interaction between the protein and reagent. This new slot comb (tentatively called slope comb) was applied to the following two experiments. In the first experiment, in combination with this comb and a reducing agent, 2-mercaptoethanol, the reducing steps of cross-linked axonemal proteins with o-iodosobenzoic acid (OIBA) were analyzed electrophoretically, enabling visualization of the reducing pattern of each axonemal protein in a single experiment. The results obtained indicate that alpha and beta tubulins are cross-linked differently by OIBA. In the second experiment, the formation of the Ca2+ gradient layer using this slope comb could electrophoretically differentiate the Ca2+ sensitivity of three Ca(2+)-binding proteins.     

Partial deficiency of hypoxanthine-guanine phosphoribosyltransferase with reduced affinity for PP-ribose-P in four related males with gout

Summary A family is described in which four affected males, spanning two generations, have hyperuricemia and gout accompanied by hematuria but are without severe neurologic involvement. The affected males were found to have markedly reduced levels of erythrocytic hypoxanthine-guanine phosphoribosyltransferase (HGPRT) activity; these were 5–12% with hypoxanthine and 0.5–3% with guanine as compared to controls. Erythrocytic adenine phosphoribosyltransferase (APRT) was approximately three-fold elevated in the affected individuals.The residual HGPRT activity in affected males enabled characterization of some of the properties of this mutation. The apparent Michaelis constants (km) for both hypoxanthine and guanine were essentially unchanged, whereas the km for PP-ribose-P was approximately 10–20-fold elevated for all four affected males. The enzyme was more sensitive to product inhibition by IMP and GMP than controls, and exhibited greater thermal lability at 65°C than found with control lysates.