The effect of storage on the biomechanical behavior of articular cartilage--a large strain study.

The transplantation of stored shell osteochondral allografts is a potentially useful alternative to total joint replacements for the treatment of joint ailments. The maintenance of normal cartilage properties of the osteochondral allografts during storage is important for the allograft to function properly and survive in the host joint. Since articular cartilage is normally under large physiological stresses, this study was conducted to investigate the biomechanical behavior under large strain conditions of cartilage tissue stored for various time periods (i.e., 3, 7, 28, and 60 days) in tissue culture media. A biphasic large strain theory developed for soft hydrated connective tissues was used to describe and determine the biomechanical properties of the stored cartilage. It was found that articular cartilage stored for up to 60 days maintained the ability to sustain large compressive strains of up to 40 percent or more, like normal articular cartilage. Moreover, the equilibrium stress-strain behavior and compressive modulus of the stored articular cartilage were unchanged after up to 60 days of storage.     

Analysis of Legionella pneumophila serogroup 6 strains isolated from a hospital warm water supply over a three-year period by using genomic long-range mapping techniques and monoclonal antibodies.

Over a period of 3 years, Legionella pneumophila serogroup 6 strains were isolated from warm water outlets and dental units in the Dental Faculty and from the Surgery and Internal Medicine Clinics at the University of Dresden, Dresden, Germany. In the bacteriological unit of the above-mentioned facility, L. pneumophila serogroups 3 and 12 were grown from warm water specimens. The medical facilities are located in separate buildings connected with a ring pipe warm water system. All L. pneumophila serogroup 6 strains isolated from the warm water supply reacted with a serogroup-specific monoclonal antibody, but not with two other monoclonal antibodies which are subgroup specific, reacting with other serogroup 6 strains. The NotI genomic profiles obtained by pulsed-field gel electrophoresis of 25 serogroup 6 strains isolated from the Dental Faculty over a 3-year period, 1 isolate from the Internal Medicine Clinic, and 4 strains from the Surgery Clinic were identical. Furthermore, all these strains hybridized with a 300-kb NotI fragment when a legiolysin (lly)-specific DNA probe was used. The NotI pattern, however, differed from those of six serogroup 6 strains of other origins, one serogroup 12 strain from the bacteriological unit, and another six unrelated strains of serogroups other than serogroup 6. L. pneumophila serogroup 6 strains which can be divided into only two subgroups by the use of monoclonal antibodies are differentiated in at least six NotI cleavage types obtained by pulsed-field electrophoresis.     

Specificity of cytochemical demonstration of adenylate cyclase in liver using adenylate-(beta, gamma-methylene) diphosphate as substrate

Adenylate cyclase activity was demonstrated cytochemically in rat liver for the first time under the light microscope using cryostat sections mounted on glass cover slips and fixed with 1% glutaraldehyde for 1 min. Adenylate-(beta, gamma-methylene)diphosphate (AMP-P(CH2)P) was introduced as a new substrate for adenylate cyclase. It was found that adenylate cyclase was distributed heterogenously within the liver lobule. The enzyme activity was stronger in the area surrounding the central vein. A more specific localization at the plasma membrane and less unspecific background was obtained with AMP-P(CH2)P as compared to adenylylimidodiphosphate (AMP-P(NH)P). The specificity of the enzyme reaction using AMP-P(CH2)P was proved by increased formation of reaction product in the presence of 0.05 mg/ml glucagon and 0.125 mg/ml cholera toxin, as well as by inhibition of the reaction with 0.05 mg/ml alloxan. These effects were also observed at the electron microscopic level. On the other hand, no increase in reaction was observed in the presence of glucagon with AMP-P(NH)P as a substrate for adenylate cyclase, and only a weak activation was observed after adding cholera toxin; alloxan-inhibition was not complete. These effects may be due to the presence of enzymes which hydrolyze AMP-P(NH)P nonspecifically, superimposing on the product of adenylate cyclase activity. We therefore suggest the use of AMP-P(CH2)P as substrate for histochemical adenylate cyclase demonstration in the liver.     

Increased transport of acetyl‐CoA into the endoplasmic reticulum causes a progeria‐like phenotype

The membrane transporter AT‐1/SLC33A1 translocates cytosolic acetyl‐CoA into the lumen of the endoplasmic reticulum (ER), participating in quality control mechanisms within the secretory pathway. Mutations and duplication events in AT‐1/SLC33A1 are highly pleiotropic and have been linked to diseases such as spastic paraplegia, developmental delay, autism spectrum disorder, intellectual disability, propensity to seizures, and dysmorphism. Despite these known associations, the biology of this key transporter is only beginning to be uncovered. Here, we show that systemic overexpression of AT‐1 in the mouse leads to a segmental form of progeria with dysmorphism and metabolic alterations. The phenotype includes delayed growth, short lifespan, alopecia, skin lesions, rectal prolapse, osteoporosis, cardiomegaly, muscle atrophy, reduced fertility, and anemia. In terms of homeostasis, the AT‐1 overexpressing mouse displays hypocholesterolemia, altered glycemia, and increased indices of systemic inflammation. Mechanistically, the phenotype is caused by a block in Atg9a‐Fam134b‐LC3β and Atg9a‐Sec62‐LC3β interactions, and defective reticulophagy, the autophagic recycling of the ER. Inhibition of ATase1/ATase2 acetyltransferase enzymes downstream of AT‐1 restores reticulophagy and rescues the phenotype of the animals. These data suggest that inappropriately elevated acetyl‐CoA flux into the ER directly induces defects in autophagy and recycling of subcellular structures and that this diversion of acetyl‐CoA from cytosol to ER is causal in the progeria phenotype. Collectively, these data establish the cytosol‐to‐ER flux of acetyl‐CoA as a novel event that dictates the pace of aging phenotypes and identify intracellular acetyl‐CoA‐dependent homeostatic mechanisms linked to metabolism and inflammation.     

Interspecific competition alters leaf stoichiometry in 20 grassland species

The extensive use of traits in ecological studies over the last few decades to predict community functions has revealed that plant traits are plastic and respond to various environmental factors. These plant traits are assumed to predict how plants compete and capture resources. Variation in stoichiometric ratios both within and across species reflects resource capture dynamics under competition. However, the impact of local plant diversity on species‐specific stoichiometry remains poorly studied. Here, we analyze how spatial and temporal diversity in resource‐acquisition traits affects leaf elemental stoichiometry of plants (i.e. the result of resource capture) and how flexible this stoichiometry is depending on the functional composition of the surrounding community. Therefore, we assessed inter‐ and intraspecific variations of leaf carbon (C), nitrogen (N), and phosphorus (P) (and their ratios) of 20 grassland species in a large trait‐based plant diversity experiment located in Jena (Germany) by measuring leaf elemental concentrations at the species‐level along a gradient in plant trait dissimilarity. Our results show that plants showed large intra‐ and interspecific variation in leaf stoichiometry, which was only partly explained by the functional group identity (grass or herb) of the species. Elemental concentrations (N, P, but not C) decreased with plant species richness, and species tended to become more deviant from their monoculture stoichiometry with increasing trait dissimilarity in the community. These responses differed among species, some consistently increased or decreased in P and N concentrations; for other species, the negative or positive change in P and N concentrations increased with increasing trait difference between the target species and the remaining community. The strength of this relationship was significantly associated to the relative position of the species along trait gradients related to resource acquisition. Trait‐difference and trait‐diversity thus were important predictors of how species’ resource capture changed in competitive neighbourhoods.     

EARLY STARVATION1 specifically affects the phosphorylation action of starch‐related dikinases

Starch phosphorylation by starch‐related dikinases glucan, water dikinase (GWD) and phosphoglucan, water dikinase (PWD) is a key step in starch degradation. Little information is known about the precise structure of the glucan substrate utilized by the dikinases and about the mechanisms by which these structures may be influenced. A 50‐kDa starch‐binding protein named EARLY STARVATION1 (ESV1) was analyzed regarding its impact on starch phosphorylation. In various in vitro assays, the influences of the recombinant protein ESV1 on the actions of GWD and PWD on the surfaces of native starch granules were analyzed. In addition, we included starches from various sources as well as truncated forms of GWD. ESV1 preferentially binds to highly ordered, α‐glucans, such as starch and crystalline maltodextrins. Furthermore, ESV1 specifically influences the action of GWD and PWD at the starch granule surface. Starch phosphorylation by GWD is decreased in the presence of ESV1, whereas the action of PWD increases in the presence of ESV1. The unique alterations observed in starch phosphorylation by the two dikinases are discussed in regard to altered glucan structures at the starch granule surface.