Effects of Weight Loss and Physical Activity on Muscle Lipid Content and Droplet Size

Objectives : To address the potential effects of weight loss and physical activity (WL + Ex) on intramyocellular lipid (IMCL) and lipid droplet size in overweight and obese previously sedentary individuals. Research Methods and Procedures : IMCL and lipid droplet size was determined in vastus lateralis, obtained by percutaneous biopsy, from 21 obese volunteers (9 men/12 women), using Oil Red O staining, along with succinate dehydrogenase histochemistry and mitochondrial immunohistochemistry as measures of skeletal muscle oxidative capacity. Insulin sensitivity (IS) was determined by glucose clamp. Results : A 4‐month WL + Ex intervention resulted in ～10% WL and ～15% increase in maximal oxygen uptake, leading to a 46% increase in IS (all p < 0.01). IMCL did not significantly change (p = 0.36). However, the size of lipid droplets decreased after WL + Ex (p < 0.01), and this decrease in lipid droplet size correlated with increased IS (p < 0.01) and the amount of physical activity (p < 0.05). Succinate dehydrogenase activity and mitochondrial labeling increased significantly (p < 0.01), without a significant shift in fiber type distribution. Discussion : In summary, IMCL does not decrease in response to WL + Ex in obese, previously sedentary individuals, yet the lipid within muscle is dispersed into smaller droplets. This change in the size of lipid droplets, likely coupled with a concomitant increase in oxidative enzyme capacity, is correlated to improved IS.     

β1 integrin regulates MMP-10 dependant tubulogenesis in human lymphatic endothelial cells

Lymphatic vessel growth requires extensive remodeling of the extracellular matrix, a process hypothesized to be related to the expression and function of the matrix metalloproteinases. We used a protein based screening strategy to demonstrate increased matrix matalloproteinase-10 expression in human lymphatic endothelial cells undergoing collagen I induced tubulogenesis. Knock-down experiments showed that matrix metalloproteinase-10 regulated lymphatic endothelial cell tubulogenesis. β1 integrin signaling via the ERK/MAPK pathway increased matrix metalloproteinase-10 mRNA and protein expression in human lymphatic endothelial cells. These findings demonstrate a novel mechanism by which β1 integrin regulates matrix metalloproteinase-10 expression during lymphatic vessel remodeling.     

Vocal mimicry in male bowerbirds: who learns from whom?

Vocal mimicry is one of the more striking aspects of avian vocalization and is widespread across songbirds. However, little is known about how mimics acquire heterospecific and environmental sounds. We investigated geographical and individual variation in the mimetic repertoires of males of a proficient mimic, the spotted bowerbird Ptilonorhynchus maculatus. Male bower owners shared more of their mimetic repertoires with neighbouring bower owners than with more distant males. However, interbower distance did not explain variation in the highly repeatable renditions given by bower owners of two commonly mimicked species. From the similarity between model and mimic vocalizations and the patterns of repertoire sharing among males, we suggest that the bowerbirds are learning their mimetic repertoire from heterospecifics and not from each other.     

Lack of association between glucocorticoid use and presence of the metabolic syndrome in patients with rheumatoid arthritis: a cross-sectional study

Lupus nephritis is a major contributor to morbidity and mortality in systemic lupus erythematosus, but little is known about the pathogenic processes that underlie the progressive decay in renal function. A common finding in lupus nephritis is thickening of glomerular basement membranes associated with immune complex deposition. It has been speculated that alterations in the synthesis or degradation of membrane components might contribute to such changes, and thereby to initiation and progression of nephritis through facilitation of immune complex deposition. Matrix metalloproteinases (MMPs) are enzymes that are intimately involved in the turnover of major glomerular basement membrane constituents, including collagen IV and laminins. Alterations in the expression and activity of MMPs have been described in a number of renal diseases, suggesting their relevance to the pathogenesis of various glomerulopathies. The same is true for their natural inhibitors, the tissue inhibitor of metalloproteinase family. Recent data from our group have identified an increase in proteolytic activity within the glomerulus coinciding with the development of proteinuria in the mouse model of systemic lupus erythematosus. (NXB × NZW)F₁ Here we review current understanding of MMP/tissue inhibitor of metalloproteinase function within the kidney, and discuss their possible involvement in the development and progression of lupus nephritis.     

Survival Response of <Emphasis Type="Italic">Bacteriovorax</Emphasis> in Surface Biofilm Versus Suspension when Stressed by Extremes in Environmental Conditions

The Bacteriovorax, previously in the genus Bdellovibrio, are prokaryotes that prey upon many Gram-negative bacteria. They are ubiquitous in salt-water environments and have been reported to have a strong association with biofilms. The purpose of this study was to test the hypothesis that this association affords protection for the Bacteriovorax and enhances their survival in nature when exposed to extreme environmental conditions. Experiments were designed to compare their survival in biofilms versus in suspension when exposed to extremes in salinity and temperature. Natural mixed-population biofilms generated in moderate-salinity (16‰) Patuxent River water and containing Bacteriovorax were exposed to drastic changes in salinity by placing in low-salinity (1‰) river water and salt-free (no measurable salinity) distilled water for up to 14 days. In a separate trial, the biofilm was exposed to extremes in temperature, 5°C and 35°C, for up to 12 weeks in aquarium mesocosms. Simultaneously, suspensions of the Bacteriovorax were exposed to the same extremes in salinity and temperature as biofilms. The results revealed that the Bacteriovorax typically were able to survive for a week or longer while in association with biofilms than when in suspension. These results are consistent with observations from nature and establish that biofilms are important in the survival and ecology of the Bacteriovorax.     

Molecular form of adenosine deaminase in severe combined immunodeficiency

The specific activity of adenosine deaminase was reduced to approximately 0.5% of normal in splenic tissue obtained from a patient with severe combined immunodeficiency. Sedimentation analysis of splenic homogenate from this patient revealed a major peak of adenosine deaminase activity which corresponded with respect to the sedimentation coefficient of one of three molecular species observed in control spleens but had markedly reduced activity. These findings suggest that the molecular heterogeneity of human adenosine deaminase is under the control of a single genetic locus and that the deficiency of adenosine deaminase activity in severe combined immunodeficiency is not due to a genetic deletion.     

The methylated constituents of L cell messenger RNA: evidence for an unusual cluster at the 5' terminus.

An analysis of the methylated constituents of L cell mRNA by a combination of chromatographic methods and enzymatic treatments indicates that they comprise both 2'-O-methyl nucleosides and N6-methyl adenine, and/or 1-methyl adenine, and suggests that the 2'-O-methyl nucleotides, Ym, are part of an unusual class of sequences forming the 5' terminus of mRNA. These sequences seem to contain two 2'-O-methyl residues and a terminal residue that is not phosphorylated but, nevertheless, is blocked with respect to polynucleotid kinase reactivity. A strong candidate is a sequence of the type XppY1mpY2mpZp..., where X represents a blocking group which is itself occasionally methylated. The sequences isolated from total poly(A)+ mRNA contain all four species of 2'-O-methylated nucleoside, indicating some variability among different mRNA species. The methylated sequences do not appear to be enriched in the mRNA which hybridizes with repetitive DNA. The average L cell mRNA molecule also contains three residues of N6-methyl adenine. These residues are not part of the poly(A) segment, but appear to be located internal to the poly(A) near the 3' end of the mRNA molecules.     

Effects of different alleles of the E. coli K12 polA gene on the replication of non-transferring plasmids

Summary The effects of eight different polA ^-alleles on the replication of six different non-transferring enterobacterial plasmids have been tested. Using phage P1CM transduction, different allelic polA ^- mutations were introduced into E. coli K12 strains carrying one of several antibiotic resistance plasmids. Plasmid stability in the transductants was examined by testing clones for drug resistance after growth under various conditions. From the results, the R factors may be divided into three different classes. One plasmid is only affected by PolA^- conditions which inhibit host cell growth, three plasmids (from the same compatibility group) are unstable under conditions in which the cells are severely deficient in DNA polymerase I and two other plasmids (compatible with each other and with the other four) are immediately lost from such transductants and are unstable in a number of others. Furthermore, the plasmids which are most dependent on DNA polymerase I have been shown to replicate in the presence of chloramphenicol and therefore typify a class of plasmids which includes bacteriocinogenic factors such as ColE1 and CloDF13, resistance determinant RSF1030 and the E. coli 15 minicircular plasmid.