Particle retention in the forestomach of a browsing ruminant, the roe deerCapreolus capreolus

A combination of a flotation/sedimentation experiment and sieve analysis for the reticulorumen (RR) contents of roe deerCapreolus capreolus Linnaeus, 1758, a browsing ruminant, showed that there was no correlation between particle size and particle density. Large particles were present in both the sedimented and the buoyant fraction, which is in accord with the reported absence of stratification of RR contents in browsing ruminants. Comparative sieve analysis of roe deer RR and caecal/rectal material demonstrated that there must be some selective particle retention in the browsing ruminant as well, as a certain fraction of large particles in RR contents does not occur in the caecal/rectal material. These results lead to the explanatory dilemma that, while selective particle retention is observed, it cannot be due to the mechanisms known to work in grazing ruminants.     

AU binding proteins recruit the exosome to degrade ARE-containing mRNAs.

Inherently unstable mammalian mRNAs contain AU-rich elements (AREs) within their 3' untranslated regions. Although found 15 years ago, the mechanism by which AREs dictate rapid mRNA decay is not clear. In yeast, 3'-to-5' mRNA degradation is mediated by the exosome, a multisubunit particle. We have purified and characterized the human exosome by mass spectrometry and found its composition to be similar to its yeast counterpart. Using a cell-free RNA decay system, we demonstrate that the mammalian exosome is required for rapid degradation of ARE-containing RNAs but not for poly(A) shortening. The mammalian exosome does not recognize ARE-containing RNAs on its own. ARE recognition requires certain ARE binding proteins that can interact with the exosome and recruit it to unstable RNAs, thereby promoting their rapid degradation.     

IKKalpha provides an essential link between RANK signaling and cyclin D1 expression during mammary gland development.

To identify functions of the IKKalpha subunit of IkappaB kinase that require catalytic activity, we generated an Ikkalpha(AA) knockin allele containing alanines instead of serines in the activation loop. Ikkalpha(AA/AA) mice are healthy and fertile, but females display a severe lactation defect due to impaired proliferation of mammary epithelial cells. IKKalpha activity is required for NF-kappaB activation in mammary epithelial cells during pregnancy and in response to RANK ligand but not TNFalpha. IKKalpha and NF-kappaB activation are also required for optimal cyclin D1 induction. Defective RANK signaling or cyclin D1 expression results in the same phenotypic effect as the Ikkalpha(AA) mutation, which is completely suppressed by a mammary specific cyclin D1 transgene. Thus, IKKalpha is a critical intermediate in a pathway that controls mammary epithelial proliferation in response to RANK signaling via cyclin D1.     

Phylogeny of Symphytognathidae s.l. (Araneae, Araneoidea)

The paper presents a phylogenetic analysis of Symphytognathidae sensu lato (= sensu Forster 1959): Anapidae, Micropholcommatidae, Mysmenidae and Symphytognathidae sensu stricto. These taxa include the smallest known spiders. Several authors have suggested that their similarities are merely the convergent result of reduction and loss (simplifications, minimization of organs). The data matrix comprises 80 characters scored for 12 ingroup and two outgroup taxa. The value of reduction characters is discussed in general, and the evidence regarding symphytognathids in particular is reviewed. In this case, homology explains the data better than convergence. Although Symphytognathidae s.l . is, in fact, based mainly on characters that might have accompanied miniaturization, the taxon is most probably monophyletic. Anapidae as currently defined is paraphyletic. As it constitutes, together with Micropholcommatidae, a well supported monophyletic group, the latter is herewith synonymised with the former. Mysmenidae should be relimited by transferring four Old World genera to a new family, Synaphridae. Sympyhtognathidae s.s. is also monophyletic, even though the main synapomorphy, fused chelicerae, also occurs in Mysmenidae.     

Technical enzymes produced in transgenic plants

Technical enzymes are used in many industrial applications. Nowadays technical enzymes are often produced in transgenic host organisms. The use of transgenic plants with respect to high level of expression at low costs as a prerequisite for successful commercial production of technical enzymes is discussed. This review summarises recently published examples for production of technical enzymes in plants. In addition, plastid transformation and viral vectors are discussed as methods which might be useful for obtaining high expression level of recombinant proteins in plants.     

Dietary hydroxy fatty acids are absorbed in humans: implications for the measurement of 'oxidative stress' in vivo.

Lipid peroxidation products formed in vivo or originating from the diet may lead to atherosclerosis. However, little is known about the absorption of these products in man. We studied the absorption of fat (30 g) containing 14-15 mg [U-13C]-labeled hydroxy or dihydroxy triglycerides in two groups of six apparently healthy women aged 40 +/- 2 years. Post-prandial 13C-labeled hydroxy fatty acid concentration increased in a pattern somewhat different from that of plasma triglycerides, with peak levels being reached between 4 and 6 h. However, the amount of 13C-labeled oxidized fat absorbed (area under the curve of plasma concentrations from 0 to 8 h) was related to that of plasma triglycerides: 13C hydroxy vs TG (r = 0.88, p <.02), and 13C dihydroxy vs TG (r = 0.85, p <.05). 13C monohydroxy triglycerides appeared to be absorbed to a greater extent than those of 13C dihydroxy triglycerides. Although low levels of 13C hydroxy lipids could be detected in fasting plasma after 24 h, concentrations were very low. Dietary lipid oxidation products are absorbed. The measurement of hydroxy fatty acids in plasma total lipids may not be a valid marker of lipid peroxidation in vivo when subjects are not fasting.     

Detailed chromosomal and radiation hybrid mapping in the proximal part of rat Chromosome 10 and gene order comparison with mouse and human

The rat provides valuable and sometimes unique models of human complex diseases. To fully exploit the rat models in biomedical research, it is important to have access to detailed knowledge of the rat genome organization as well as its relation to the human genome. Rat Chromosome 10 (RNO10) harbors several important cancer-related genes. Deletions in the proximal part of RNO10 were repeatedly found in a rat model for endometrial cancer. To identify functional and positional candidate genes in the affected region, we used radiation hybrid (RH) mapping and single- and dual-color fluorescence in situ hybridization (FISH) techniques to construct a detailed chromosomal map of the proximal part of RNO10. The regional localization of 14 genes, most of them cancer-related (Grin2a, Gspt1, Crebbp, Gfer, Tsc2, Tpsb1, Il9r, Il4, Irf1, Csf2, Sparc, Tp53, Thra1, Gh1), and of five microsatellite markers (D10Mit10, D10Rat42, D10Rat50, D10Rat72, and D10Rat165) was determined on RNO10. For a fifteenth gene, Ppm1b, which had previously been assigned to RNO10, the map position was corrected to RNO6q12-q13.     

Growth and cellular organization of Arabidopsis pollen tubes in vitro

Tricellular pollen tubes of Arabidopsis thaliana were cultured in vitro on solid media and studied with respect to growth, cellular organization and ultrastructure, cytoskeletal organization, organelle movement, deposition and structure of the wall and the occurrence of coated pits, all elements assumed to be relevant for tip growth. For our ultrastructural studies we used freeze fixation and freeze substitution. Although Arabidopsis pollen tubes are broadly similar to those of bicellular species such as Nicotiana tabacum and Lilium spec. and in vivo grown pollen tubes of Arabidopsis, some differences occurred. The density of the equally distributed, relatively small (85 nm) secretory vesicles (SV) in the tip is low (five/µm ²). In between the SV of the tip, membranous material, possibly smooth endoplasmic reticulum, fragments of rough endoplasmic reticulum and loose ribosomes are present. The wall in the tip is not amorphous but layered and a secondary wall is formed already in the flanks of the tip. The general pattern of organelle motion is reverse fountain-like, but individual organelles move in distinct lanes at speeds of up to 2 µm/s, and about half of the organelle population shows a moderate velocity or Brownian movement. These properties are discussed in relation to the low growth rate (10 µm/h) of Arabidopsis pollen grown in vitro. The two similar sperm cells are closely attached and are always found near the vegetative nucleus. No surrounding wall and no cytoskeletal elements were obvious in the sperm cells. The preferential location of the mitochondria at the wall and the large (up to 400 nm) coated pits are unique for angiosperm pollen tubes. The size of the coated pits may allow not only membrane retrieval but also pinocytosis.