The Death of Plants in Animals

It is necessary first to understand some of the basic concepts associated with the digestion of the plant biomass within the rumen when considering mechanisms for altering/enhancing N-conversion efficiency in the forage-fed ruminant. Although it is generally assumed that breakdown of plant proteins in the rumen is mediated by microbial enzymes, there is increasing evidence to suggest that both plant and microbial proteases are active during degradation of ingested fresh forage (Beha et al., 2002; Kingston-Smith & Theodorou, 2000; Kingston-Smith et al., 2003, 2004). After fresh plant biomass enters the rumen and prior to extensive plant cell wall degradation, there is often a phase of rapid proteolysis in excess of that needed to maintain the rumen microbial population and we now believe that plant enzymes largely mediate this initial proteolysis. Recent evidence also suggests a role for plant lipases in the rumen (Lee et al., 2003). An understanding of the mechanisms that underlie these processes is essential if we are to devise plant-based strategies to manipulate them. This paper presents a new rumen model which, by taking account of the plants biological attributes, provides us with a novel framework for describing the plant contribution to rumen function in grazing livestock

Numerical renormalization-group study of spin correlations in one-dimensional random spin chains

We calculate the ground-state two-spin correlation functions of spin-1/2 quantum Heisenberg chains with random exchange couplings using the real-space renormalization group scheme. We extend the conventional scheme to take account of the contribution of local higher multiplet excitations in each decimation step. This extended scheme can provide highly accurate numerical data for large systems. The random average of staggered spin correlations of the chains with random antiferromagnetic (AF) couplings shows algebraic decay like $1/r^2$, which verifies the Fisher's analytic results. For chains with random ferromagnetic (FM) and AF couplings, the random average of generalized staggered correlations is found to decay more slowly than a power-law, in the form close to $1/\ln(r)$. The difference between the distribution functions of the spin correlations of the random AF chains and of the random FM-AF chains is also discussed.Comment: 14 pages including 8 figures, REVTeX, submitted to Physical Review

Efficiency of Nitrogen Use in Dairy Cows Grazing Ryegrass with Different Water Soluble Carbohydrate Concentrations

This experiment is one of a series designed to investigate the efficiency of nitrogen (N) use in Holstein-Friesian dairy cows grazing perennial ryegrass (Lolium perenne) which has been bred to express high water soluble carbohydrate (WSC) concentrations. Animals grazed either a High Sugar (HS) grass or a Control (C) variety chosen on the basis of heading date compatibility. Dry matter (DM) intakes were estimated using herbage mass. Milk yields, milk constituent concentrations and plasma concentrations of b-hydroxybutyrate, glucose, total protein, albumin and urea were also measured. Forage DM intakes were similar for the two grasses. However, because of differences in the nitrogen content of the varieties (128 vs 176 g crude protein (CP) kg-1 DM; s.e.d. 10.5; P \u3c 0.01) the animals consuming the C diet received ca. 35% more dietary N. Despite this, milk yields and outputs of milk fat, lactose and total protein were similar between treatments. These data indicate that the partition of dietary N for milk protein biosynthesis was much higher (P \u3c 0.01) in animals consuming the HS grass, which is reflected by the lower plasma urea concentrations in these animals. It is proposed that by providing grass varieties with a better match of readily available energy and protein, significant improvements in N use efficiency can be achieved

Anomalous pinning behavior in an incommensurate two-chain model of friction

Pinning phenomena in an incommensurate two-chain model of friction are studied numerically. The pinning effect due to the breaking of analyticity exists in the present model. The pinning behavior is, however, quite different from that for the breaking of analyticity state of the Frenkel-Kontorova model. When the elasticity of chains or the strength of interchain interaction is changed, pinning force and maximum static frictional force show anomalously complicated behavior accompanied by a successive phase transition and they vanish completely under certain conditions.Comment: RevTex, 9 pages, 19 figures, to appear in Phys. Rev. B58 No.23(1998

A molecular dynamics simulation of polymer crystallization from oriented amorphous state

Molecular process of crystallization from an oriented amorphous state was reproduced by molecular dynamics simulation for a realistic polyethylene model. Initial oriented amorphous state was obtained by uniaxial drawing an isotropic glassy state at 100 K. By the temperature jump from 100 K to 330 K, there occurred the crystallization into the fiber structure, during the process of which we observed the developments of various order parameters. The real space image and its Fourier transform revealed that a hexagonally ordered domain was initially formed, and then highly ordered crystalline state with stacked lamellae developed after further adjustment of the relative heights of the chains along their axes.Comment: 4 pages, 3 figure

Retrotransposon activation contributes to neurodegeneration in a Drosophila TDP-43 model of ALS

Amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration (FTLD) are two incurable neurodegenerative disorders that exist on a symptomological spectrum and share both genetic underpinnings and pathophysiological hallmarks. Functional abnormality of TAR DNA-binding protein 43 (TDP-43), an aggregation-prone RNA and DNA binding protein, is observed in the vast majority of both familial and sporadic ALS cases and in ~40% of FTLD cases, but the cascade of events leading to cell death are not understood. We have expressed human TDP-43 (hTDP-43) in Drosophila neurons and glia, a model that recapitulates many of the characteristics of TDP-43-linked human disease including protein aggregation pathology, locomotor impairment, and premature death. We report that such expression of hTDP-43 impairs small interfering RNA (siRNA) silencing, which is the major post-transcriptional mechanism of retrotransposable element (RTE) control in somatic tissue. This is accompanied by de-repression of a panel of both LINE and LTR families of RTEs, with somewhat different elements being active in response to hTDP-43 expression in glia versus neurons. hTDP-43 expression in glia causes an early and severe loss of control of a specific RTE, the endogenous retrovirus (ERV) gypsy. We demonstrate that gypsy causes the degenerative phenotypes in these flies because we are able to rescue the toxicity of glial hTDP-43 either by genetically blocking expression of this RTE or by pharmacologically inhibiting RTE reverse transcriptase activity. Moreover, we provide evidence that activation of DNA damage-mediated programmed cell death underlies both neuronal and glial hTDP-43 toxicity, consistent with RTE-mediated effects in both cell types. Our findings suggest a novel mechanism in which RTE activity contributes to neurodegeneration in TDP-43-mediated diseases such as ALS and FTLD