Induction of pregnancy-associated murine protein-1 in dwarf mice by human growth hormone

Pregnancy-associated murine protein-1 (PAMP-1) could not be detected in peripheral blood of female dwarf mice (genotype dw/dw of the DW strain). By contrast the normal size females of the DW strain (genotypes +/+ and +/dw) had PAMP-1 serum levels of 18.9 AU +/- 15.7 AU/ml. Following administration of biosynthetic human growth hormone (hGH) every 2 h for 52 h PAMP-1 was detected in all dwarf females at concentrations of 16.0 AU +/- 3.3 AU/ml. The albumin levels in the circulation of DW females of normal size were significantly higher (P less than 0.05) than those of DW dwarfs, and the hGH administration did not change the serum albumin levels. The present experiment adds weight to the suggestion that the PAMP-1 serum level is regulated by GH.     

Role of lipoxygenase products in the effects of angiotensin II in the isolated aorta and perfused heart of the rat

The objective of this study was to determine whether arachidonate metabolites are involved in the vasoconstrictive effects of angiotensin II in rats. In the isolated perfused heart, dexamethasone (4 mg/kg) significantly suppressed the maximal decreases in coronary flow induced by angiotensin II and vasopressin (reference drug). In the heart, the nonselective lipoxygenase inhibitor nordihydroguaiaretic acid (NDGA, 1 muM) markedly suppressed the angiotensin II-induced decreases in coronary flow. NDGA (10 muM) inhibited both angiotensin II- and methoxamine- (reference drug) induced contractions in aortic rings with (in the presence of L-NAME) and without endothelium. In the heart, the leukotriene synthesis inhibitor MK-886 (0.3 muM) significantly reduced the maximal effects to angiotensin II, but the leukotriene antagonist FPL 55712 (0.1 and 0.3 muM) had no effect. We conclude that in the isolated perfused rat heart angiotensin II-induced decreases in coronary flow are in part mediated by Hpoxygenase products, which might be derived from the 5-Hpoxygenase pathway, but are probably not leukotrienes. Furthermore, endothelium independent Hpoxygenase products mediate part of the contractile responses to angiotensin II in the isolated rat aorta.     

An assessment of feral horse impacts on treeless drainage lines in the Australian Alps

The feral Horse (Equus caballus) is widespread across the Australian Alps. Feral horses degrade alpine and sub‐alpine ecosystems and damage habitat of a range of threatened species. Despite this, there is little published work to document the extent and severity of these impacts. This study investigated impacts of feral horses on treeless drainage lines at 186 sites across the Australian Alps. The study included sites in the Australian Capital Territory, New South Wales and Victoria. We assessed nine variables related to soil and stream stability and vegetation cover, which in turn influence ecosystem function and habitat quality. We found significant differences among horse‐occupied and horse‐free sites for all soil and stream stability variables assessed. For all variables assessed, the average score (and hence, condition) was worse in horse‐occupied areas. The sites in poorest condition were occupied by horses. Impacts from other mammalian herbivores species appeared to be minor. Management intervention is necessary if these impacts of feral horses are to be addressed.     

Visualization by cryo-electron microscopy of genomic RNA that binds to the protein capsid inside bacteriophage MS2

The icosahedrally symmetrized structure of bacteriophage MS2 as determined by cryo-electron microscopy (EM) reveals the presence of genomic RNA that attaches to coat-protein dimers. Earlier X-ray diffraction studies revealed similar interactions between the unique operator hairpin of the MS2 genomic RNA and the coat-protein dimer. This observation leads us to conclude that not only the operator, but also many other RNA sequences in the genome of MS2, are able to bind to the coat-protein dimer. A substantial number of potential coat-protein-dimer binding sites are present in the genome of MS2 that can account for the observed RNA densities in the EM map. Moreover, it appears that these stem-loop structures are able to bind in a similar fashion to the coat protein dimer as the wild-type operator hairpin. The EM map also shows additional density between the potential operator-binding sites, linking the RNA stem-loops together to form an icosahedral network around the 3 and 5-fold axes. This RNA network is bound to the inside of the MS2 capsid and probably influences both capsid stability and formation, supporting the idea that capsid formation and RNA packaging are intimately linked to each other.     

Profiling DNA methylation by melting analysis

The idea of modifying DNA with bisulfite has paved the way for a variety of polymerase chain reaction (PCR) methods for accurately mapping 5-methylcytosine at specific genes. Bisulfite selectively deaminates cytosine to uracil under conditions where 5-methylcytosine remains unreacted. Following conventional PCR amplification of bisulfite-treated DNA, original cytosines appear as thymine while 5-methylcytosines appear as cytosine. Because the relative thermostability of a DNA duplex increases with increasing content of G:C base pairs, PCR products originating from DNA templates with different contents of 5-methylcytosine differ in melting temperature, i.e., the temperature required to convert the double helix into random coils. We describe two methods that resolve differentially methylated DNA sequences on the basis of differences in melting temperature. The first method integrates PCR amplification of bisulfite-treated DNA and subsequent melting analysis by using a thermal cycler coupled with a fluorometer. By including in the reaction a PCR-compatible, fluorescent dye that specifically binds to double-stranded DNA, the melting properties of the PCR product can be examined directly in the PCR tube by continuous fluorescence monitoring during a temperature transition. The second method relies on resolution of alleles with different 5-methylcytosine contents by analysis of PCR products in a polyacrylamide gel containing a gradient of chemical denaturants. Optimal resolution of differences in melting temperature is achieved by a special design of PCR primers. Both methods allow resolution of "heterogeneous" methylation, i.e., the situation where the content and distribution of 5-methylcytosine in a target gene differ between different molecules in the same sample.     

Entrapping ribosomes for viral translation: tRNA mimicry as a molecular Trojan horse

Turnip yellow mosaic virus (TYMV) has a genomic plus-strand RNA with a 5' cap followed by overlapping and different reading frames for the movement protein and polyprotein, while the distal coat protein cistron is translated from a subgenomic RNA. The 3'-untranslated region harbors a tRNA-like structure (TLS) to which a valine moiety can be added and it is indispensable for virus viability. Here, we report about a surprising interaction between TYMV-RNA-programmed ribosomes and 3'-valylated TLS that yields polyprotein with the valine N terminally incorporated by a translation mechanism resistant to regular initiation inhibitors. Disruption of the TLS exclusively abolishes polyprotein synthesis, which can be restored by adding excess TLS in trans. Our observations imply a novel eukaryotic mechanism for internal initiation of mRNA translation.     

Biaryl cannabinoid mimetics--synthesis and structure-activity relationship

Synthesis, in vitro biological evaluation, and structure-activity relationships of a biaryl cannabinoid mimetic 2 are reported. Variations in the substitution pattern yielded a number of agonists with low nanomolar affinity. Replacing the phenol group by a methyl morpholino acetate group led to compound 28, a 500-fold selective CB(2) receptor agonist.     

Longevity determined by developmental arrest genes in Caenorhabditis elegans

The antagonistic pleiotropy theory of aging proposes that aging takes place because natural selection favors genes that confer benefit early on life at the cost of deterioration later in life. This theory predicts that genes that impact development would play a key role in shaping adult lifespan. To better understand the link between development and adult lifespan, we examined the genes previously known to be essential for development. From a pool of 57 genes that cause developmental arrest after inhibition using RNA interference, we have identified 24 genes that extend lifespan in Caenorhabditis elegans when inactivated during adulthood. Many of these genes are involved in regulation of mRNA translation and mitochondrial functions. Genetic epistasis experiments indicate that the mechanisms of lifespan extension by inactivating the identified genes may be different from those of the insulin/insulin-like growth factor 1 (IGF-1) and dietary restriction pathways. Inhibition of many of these genes also results in increased stress resistance and decreased fecundity, suggesting that they may mediate the trade-offs between somatic maintenance and reproduction. We have isolated novel lifespan-extension genes, which may help understand the intrinsic link between organism development and adult lifespan.     

Spatial patterns and predictors of trophic control in marine ecosystems

A key question in ecology is under which conditions ecosystem structure tends to be controlled by resource availability vs. consumer pressure. Several hypotheses derived from theory, experiments and observational field studies have been advanced, yet a unified explanation remains elusive. Here, we identify common predictors of trophic control in a synthetic analysis of 52 observational field studies conducted within marine ecosystems across the Northern Hemisphere and published between 1951 and 2014. Spatial regression analysis of 45 candidate variables revealed temperature to be the dominant predictor, with unimodal effects on trophic control operating both directly (r² = 0.32; P < 0.0001) and indirectly through influences on turnover rate and quality of primary production, biodiversity and omnivory. These findings indicate that temperature is an overarching determinant of the trophic dynamics of marine ecosystems, and that variation in ocean temperature will affect the trophic structure of marine ecosystems through both direct and indirect mechanisms.