Soil surface disturbance alters cyanobacterial biocrusts and soil properties in dry grassland and shrubland ecosystems

Plant and Soil - Biological soil crusts (biocrusts) dominate soil surfaces in drylands, providing services that include soil stabilization and carbon uptake. In this study, we investigated the...     

Megabase Length Hypermutation Accompanies Human Structural Variation at 17p11.2

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Effect of adipose tissue site, animal size, and fasting on lipolysis in bovine adipose tissue in vitro.

1. Lipolytic rates expressed as mumol glycerol released per mg protein increased with body weight in Holstein steers. 2. Lipolytic rates were greatest in both inner and outer back fat and lowest in omental, perirenal, and intermuscular fat depots. 3. Epinephrine stimulated overall glycerol release 3-5-fold. 4. Fasting resulted in greater basal lipolytic rates but epinephrine-stimulated rates tended to be greater for nonfasted steer adipose tissue. 5. Lipolytic activity in adipose tissue seems to increase with growth and fattening, and differences in lipolytic rates between various depots diminish with growth.     

Mitochondrial dynamics in the neonatal brain – a potential target following injury?

The impact of birth asphyxia and its sequelae, hypoxic–ischaemic (HI) brain injury, is long-lasting and significant, both for the infant and for their family. Treatment options are limited to therapeutic hypothermia, which is not universally successful and is unavailable in low resource settings. The energy deficits that accompany neuronal death following interruption of blood flow to the brain implicate mitochondrial dysfunction. Such HI insults trigger mitochondrial outer membrane permeabilisation leading to release of pro-apoptotic proteins into the cytosol and cell death. More recently, key players in mitochondrial fission and fusion have been identified as targets following HI brain injury. This review aims to provide an introduction to the molecular players and pathways driving mitochondrial dynamics, the regulation of these pathways and how they are altered following HI insult. Finally, we review progress on repurposing or repositioning drugs already approved for other indications, which may target mitochondrial dynamics and provide promising avenues for intervention following brain injury. Such repurposing may provide a mechanism to fast-track, low-cost treatment options to the clinic.     

Mutagenicity of TCDD in Big Blue transgenic rats

The compound 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) is a significant environmental contaminant resulting from such industrial processes as pulp and paper production. TCDD is a suspected human carcinogen and its ability to induce cancer in laboratory rodents is well documented. Its mechanism of tumor initiation, however, is not well understood and in vitro mutagenicity studies have yielded inconsistent results. In this study, Big Blue lacI transgenic rats were used to assess the mutagenicity of TCDD in both male and female animals. After 6 weeks of exposure to 2 microg/kg TCDD neither an increase in mutation frequency nor any change in mutation spectrum was observed in either male or female animals.     

The Diving Response Mechanism and its Surprising Evolutionary Path in Seals andSea Lions

During the last half century or more, studies of diving physiologyand biochemistry made great progress in mechanistically explainingthe basic diving response of aquatic mammals and birds. Keycomponents of the diving response (apnea, bradycardia, peripheralvasoconstriction, redistribution of cardiac output) were foundin essentially all species analyzed and were generally takento be biological adaptations. By the mid 1970s, this approachto unravelling the diving response had run 'out of steam' andwas in conceptual stasis. The breakthrough which gave renewalto the field at this time was the development of microprocessorbased monitoring of diving animals in their natural environments,which led to a flurry of studies mostly confirming the basicoutlines of the diving response based upon laboratory studiesand firmly placing it into proper biological context, underliningits plasticity and species specificities. Now towards the endof the millenium, despite ever more detailed field monitoringof physiology, behaviour and ecology, mechanistic studies areagain approaching a point of diminishing returns. To avoid anotherconceptual stasis, what seems required are new initiatives whichwe anticipate may arise from two differing approaches. The firstis purely experimental, relying on magnetic resonance imaging(MRI) and spectroscopy (MRS) to expand the framework of theoriginal "diving response" concept. The second—evolutionarystudy of the diving response—is synthetic, linked to bothfield and laboratory studies. To date the evolution of the divingresponse has only been analyzed in pinnipeds and from thesestudies two kinds of patterns have emerged. (1) Some physiologicaland biochemical characters, required and used in diving animals,are highly conserved not only in pinnipeds but in all vertebrates;these traits are necessarily similar in all pinnipeds and includediving apnea, bradycardia, tissue specific hypoperfusion, andhypometabolism of hypoperfused tissues. (2) Another group offunctionally linked characters are more malleable and include(i) spleen mass, (ii) blood volume, and (iii) hemoglobin (Hb)pool size. Increases in any of these traits improve diving capacity.Assuming that conserved physiological function means conservedsequences in specific genes and their products (and that evolvingfunction requires changes in such sequences), it is possibleto rationalize both above trait categories in pinniped phytogeny.However, it is more difficult for molecular evolution theoryto explain how complex regulatory systems like those involvedin bradycardia and peripheral vasoconstriction remain the samethrough phylogenetic time than it is to explain physiologicalchange driven by positive natural selection.     

COVOL: an interactive program for evaluating second virial coefficients from the triaxial shape or dimensions of rigid macromolecules

An interactive program is described for calculating the second virial coefficient contribution to the thermodynamic nonideality of solutions of rigid macromolecules based on their triaxial dimensions. The FORTRAN-77 program, available in precompiled form for the PC, is based on theory for the covolume of triaxial ellipsoid particles [Rallison, J. M., and S.E Harding. (1985). J. Colloid Interface Sci. 103:284-289]. This covolume has the potential to provide a magnitude for the second virial coefficient of macromolecules bearing no net charge. Allowance for a charge-charge contribution is made via an expression based on Debye-Hückel theory and uniform distribution of the net charge over the surface of a sphere with dimensions governed by the Stokes radius of the macromolecule. Ovalbumin, ribonuclease A, and hemoglobin are used as model systems to illustrate application of the COVOL routine.     

Three-dimensional structure analysis of PROSITE patterns

Pattern matches for each of the sequence patterns in PROSITE, a database of sequence patterns, were searched in all protein sequences in the Brookhaven Protein Data Bank (PDB). The three-dimensional structures of the pattern matches for the 20 patterns with the largest numbers of hits were analysed. We found that the true positives have a common three-dimensional structure for each pattern; the structures of false positives, found for six of the 20 patterns, were clearly different from those of the true positives. The results suggest that the true pattern matches each have a characteristic common three-dimensional structure, which could be used to create a template to define a three-dimensional functional pattern.     

Correlation of observed fold frequency with the occurrence of local structural motifs

It is well known that some protein folds (superfolds) occur very frequently. We show that compared to other folds, most superfold structures have a higher proportion of their alpha-helical or beta-strand residues in one of three basic units of supersecondary structure (alpha-hairpin, beta-hairpin or betaalphabeta-unit). Furthermore, by taking into consideration two more complex motifs, the four-stranded Greek-key (beta4) and the betaalpha-Greek key (betaalphabetabeta), we demonstrate that the remaining superfold structures contain many of these higher order units of three-dimensional packing. The implications of these results for folding are discussed.     

Partial characterisation of high-molecular weight glycoconjugates in the trail mucus of the freshwater pond snail Lymnaea stagnalis

We have studied the glycoconjugates in trail mucus of the pond snail Lymnaea stagnalis. The mucus was dissolved with 6 M guanidinium hydrochloride (GuHCl) and the major component was comprised of very high-M_r glycoconjugates that were eluted in the void volume of a Sepharose CL-4B gel-filtration column. This high-M_r material was pooled and thereafter subjected to density gradient centrifugation first in 4 M GuHCl/CsCl and subsequently 0.2 M GuHCl/CsCl to further remove non-glycosylated proteins and DNA. The harvested glycoconjugate pool chromatographed in the void volume of Sepharose CL-2B. However, reduction of disulfide bonds lowered the molecular size of approximately 80% of the void material yielding a major fragment and some minor smaller fragments in gel chromatography. The reduced glycoconjugates were digested with papain and yielded high molecular weight, proteinase-resistant glycopeptides. This fragmentation pattern is similar to that found for oligomeric gel-forming mucins in mammals and the amino acid composition (60% Ser/Thr) and sugar analysis of the glycopeptides is consistent with mucin-like molecules, there being no significant amounts of xylose or uronic acids. The residual 20% of the preparation, which apparently resisted reduction and protease digestion, had a similar amino acid composition to the bulk, but was somewhat different in sugar composition, containing some xylose and a significant amount of glucuronic acid. The two groups of molecules had very different morphologies in the electron microscope. Taken together, these data suggest that trail mucus is a complex mixture of at least two families of protein-glycoconjugate molecules based upon the gel-forming mucin and proteoglycan families, though we cannot rule out that polysaccharides may also be present.