Signal-regulatory protein is selectively expressed by myeloid and neuronal cells

Signal-regulatory proteins (SIRP) are transmembrane glycoproteins with three extracellular Ig-like domains, closely related to Ag receptors Ig, TCR, and MHC, and a cytoplasmic domain with two immunoreceptor with tyrosine-based inhibition motifs that can interact with src homology 2 domain-containing phosphatases. SIRP have previously been shown to inhibit signaling through receptor tyrosine kinases, but their physiologic function is unknown. Here we demonstrate by expression cloning that the mAbs ED9, ED17, and MRC-OX41 recognize rat SIRP. In addition, we show for the first time that rat SIRP is selectively expressed by myeloid cells (macrophages, monocytes, granulocytes, dendritic cells) and neurons. Moreover, SIRP ligation induces nitric oxide production by macrophages. This implicates SIRP as a putative recognition/signaling receptor in both immune and nervous systems.     

Protein stabilization by hydrophobic interactions at the surface

The contribution of the solvent-exposed residue 63 to thermal stability of the thermolysin-like neutral protease of Bacillus stearothermophilus was studied by analyzing the effect of twelve different amino acid substitutions at this position. The thermal stability of the enzyme was increased considerably by introducing Arg, Lys or bulky hydrophobic amino acids. In general, the effects of the mutations showed that hydrophobic contacts in this surface-located region of the protein are a major determinant of thermal stability. This observation contrasts with general concepts concerning the contribution of surface-located residues and surface hydrophobicity to protein stability and indicates new ways for protein stabilization by site-directed mutagenesis.     

Effects of a combination of feed additives on methane production, diet digestibility, and animal performance in lactating dairy cows

Two experiments were conducted to assess the effects of a mixture of dietary additives on enteric methane production, rumen fermentation, diet digestibility, energy balance, and animal performance in lactating dairy cows. Identical diets were fed in both experiments. The mixture of feed additives investigated contained lauric acid, myristic acid, linseed oil, and calcium fumarate. These additives were included at 0.4, 1.2, 1.5, and 0.7% of dietary dry matter, respectively (treatment ADD). Experimental fat sources were exchanged for a rumen inert source of fat in the control diet (treatment CON) to maintain isolipidic rations. Cows (experiment 1, n = 20; experiment 2, n = 12) were fed restricted amounts of feed to avoid confounding effects of dry matter intake on methane production. In experiment 1, methane production and energy balance were studied using open-circuit indirect calorimetry. In experiment 2, 10 rumen-fistulated animals were used to measure rumen fermentation characteristics. In both experiments animal performance was monitored. The inclusion of dietary additives decreased methane emissions (g/d) by 10%. Milk yield and milk fat content tended to be lower for ADD in experiment 1. In experiment 2, milk production was not affected by ADD, but milk fat content was lower. Fat- and protein-corrected milk was lower for ADD in both experiments. Milk urea nitrogen content was lowered by ADD in experiment 1 and tended to be lower in experiment 2. Apparent total tract digestibility of fat, but not that of starch or neutral detergent fiber, was higher for ADD. Energy retention did not differ between treatments. The decrease in methane production (g/d) was not evident when methane emission was expressed per kilogram of milk produced. Feeding ADD resulted in increases of C12:0 and C14:0 and the intermediates of linseed oil biohydrogenation in milk in both experiments. In experiment 2, ADD-fed cows tended to have a decreased number of protozoa in rumen fluid when compared with that in control cows. Total volatile fatty acid concentrations were lower for ADD, whereas molar proportions of propionate increased at the expense of acetate and butyrate.     

In vitro gas and methane production of silages from whole-plant corn harvested at 4 different stages of maturity and a comparison with in vivo methane production

The current study investigated the relationship between in vitro and in vivo CH₄ production by cows fed corn silage (CS)-based rations. In vivo CH₄ production was measured in climate respiration chambers using 8 rumen-cannulated Holstein-Friesian cows. In vitro CH₄ production was measured using rumen fluid from the 8 cows that were fully adapted to their respective experimental rations. The animals were grouped in 2 blocks, and randomly assigned to 1 of the 4 total mixed rations (TMR) that consisted of 75% experimental CS, 20% concentrate, and 5% wheat straw [dry matter (DM) basis]. The experimental CS were prepared from whole-plant corn that was harvested at either a very early (25% DM), early (28% DM), medium (32% DM), or late (40% DM) stage of maturity. The 4 experimental TMR and the corresponding CS served as substrate in 2 separate in vitro runs (each run representing 1 block of 4 animals) using rumen fluid from cows fed the TMR in question. No relationship was found between in vivo CH₄ production and in vitro CH₄ production measured at various time points between 2 and 48 h. None of the in vitro gas production (GP) and CH₄ production parameters was influenced by an interaction between substrate and origin of rumen fluid. In vitro measured 48-h GP was not affected by the maturity of whole-plant corn, irrespective whether CS alone or as part of TMR was incubated in adapted rumen inoculum. Incubation of the experimental TMR did not affect the kinetics parameters associated with gas or CH₄ production, but when CS alone was incubated the asymptote of GP of the soluble fraction was slightly decreased with increasing maturity of CS at harvest. In vitro CH₄ production expressed as a percent of total gas was not affected by the maturity of whole-plant corn at harvest. Several in vitro parameters were significantly affected (GP) or tended to be affected (CH₄) by diet fed to donor cows. It was concluded that the current in vitro technique is not suitable to predict in vivo CH₄ production from CS-based rations.     

Bench-scale WGS membrane reactor for CO2 capture with co-production of H2

This study investigated the water-gas shift reaction in a bench-scale membrane reactor (M-WGS), where three supported Pd membranes of 44 cm in length and ca. 6 μm in thickness were used, reaching a total membrane surface area of 580.6 cm². The WGS reaction was studied with the syngas mixture: 4.0% CO, 19.2% CO₂, 15.4% H₂O, 1.2% CH₄ and 60.1% H₂, under high temperature/pressure conditions: T = 673 K, p_feed = 20–35 bar(a), p_perm = 15 bar(a), mimicking CO₂ capture with co-production of H₂ in a natural gas fired power plant. High reaction pressure and high permeation of Pd membranes allowed for near complete CO conversion and H₂ recovery. Both the membranes and the membrane reactor demonstrated a long-term stability under the investigated conditions, indicating the potential of M-WGS to substitute conventional systems.     

Plant-soil distribution of potentially toxic elements in response to elevated atmospheric CO2

The distribution of contaminant elements within ecosystems is an environmental concern because of these elements' potential toxicity to animals and plants and their ability to hinder microbial ecosystem services. As with nutrients, contaminants are cycled within and through ecosystems. Elevated atmospheric CO2 generally increases plant productivity and alters nutrient element cycling, but whether CO2 causes similar effects on the cycling of contaminant elements is unknown. Here we show that 11 years of experimental CO2 enrichment in a sandy soil with low organic matter content causes plants to accumulate contaminants in plant biomass, with declines in the extractable contaminant element pools in surface soils. These results indicate that CO2 alters the distribution of contaminant elements in ecosystems, with plant element accumulation and declining soil availability both likely explained by the CO2 stimulation of plant biomass. Our results highlight the interdependence of element cycles and the importance of taking a broad view of the periodic table when the effects of global environmental change on ecosystem biogeochemistry are considered.     

Effect of different levels of rapidly degradable carbohydrates calculated by a simple rumen model on performance of lactating dairy cows

Aggregating rumen degradation characteristics of different carbohydrate components into the term modeled rapidly degradable carbohydrates (mRDC) can simplify diet formulation by accounting for differences in rate and extent of carbohydrate degradation within and between feedstuffs. This study sought to evaluate responses of lactating dairy cows to diets formulated with increasing levels of mRDC, keeping the supply of other nutrients as constant as possible. The mRDC content of feedstuffs was calculated based on a simple rumen model including soluble, washable, and nonwashable but potentially degradable fractions, as well as the fractional degradation and passage rates, of sugar, starch, neutral detergent fiber, and other carbohydrates. The mRDC term effectively represents the total amount of carbohydrates degraded in the rumen within 2 h after ingestion. Fifty-two lactating Holstein cows (of which 4 were rumen fistulated) were assigned to 4 treatments in a 4 × 4 Latin square design. Treatments were fed as a total mixed ration consisting of 25.4% corn silage, 23.1% grass silage, 11.6% grass hay, and 39.9% concentrate on a dry matter basis. Differences in mRDC were created by exchanging nonforage neutral detergent fiber-rich ingredients (mainly sugar beet pulp) with starch-rich ingredients (mainly wheat) and by exchanging corn (slowly degradable starch) with wheat (rapidly degradable starch) in the concentrate, resulting in 4 treatments that varied in dietary mRDC level of 167, 181, 194, or 208 g/kg of dry matter. Level of mRDC did not affect dry matter intake. Fat- and protein-corrected milk production and milk fat and lactose yield were greatest at 181 mRDC and decreased with further increases in mRDC. Milk protein yield and concentration increased with increasing mRDC level. Mean rumen pH and diurnal variation in ruminal pH did not differ between treatments. Total daily meal time and number of visits per meal were smaller at 181 and 194 mRDC. Despite milk production responses, increasing dietary mRDC levels, while maintaining net energy and intestinal digestible protein as well as other nutrients at similar levels, did not influence rumen pH parameter estimates and had minor effects on feeding behavior. These results indicate that aggregating rapidly degradable carbohydrate content into one term may be a simple way to further improve predictability of production responses in practical diet formulation for lactating dairy cows.     

Statistical evaluation of mathematical models for microbial growth

The aim of this study was to evaluate the suitability of several mathematical functions for describing microbial growth curves. The nonlinear functions used were: three-phase linear, logistic, Gompertz, Von Bertalanffy, Richards, Morgan, Weibull, France and Baranyi. Two data sets were used, one comprising 21 growth curves of different bacterial and fungal species in which growth was expressed as optical density units, and one comprising 34 curves of colony forming units counted on plates of Yersinia enterocolitica grown under different conditions of pH, temperature and CO(2) (time-constant conditions for each culture). For both sets, curves were selected to provide a wide variety of shapes with different growth rates and lag times. Statistical criteria used to evaluate model performance were analysis of residuals (residual distribution, bias factor and serial correlation) and goodness-of-fit (residual mean square, accuracy factor, extra residual variance F-test, and Akaike's information criterion). The models showing the best overall performance were the Baranyi, three-phase linear, Richards and Weibull models. The goodness-of-fit attained with other models can be considered acceptable, but not as good as that reached with the best four models. Overall, the Baranyi model showed the best behaviour for the growth curves studied according to a variety of criteria. The Richards model was the best-fitting optical density data, whereas the three-phase linear showed some limitations when fitting these curves, despite its consistent performance when fitting plate counts. Our results indicate that the common use of the Gompertz model to describe microbial growth should be reconsidered critically, as the Baranyi, three-phase linear, Richards and Weibull models showed a significantly superior ability to fit experimental data than the extensively used Gompertz.