Resistance to radial expansion limits muscle strain and work

The collagenous extracellular matrix (ECM) of skeletal muscle functions to transmit force, protect sensitive structures, and generate passive tension to resist stretch. The mechanical properties of the ECM change with age, atrophy, and neuromuscular pathologies, resulting in an increase in the relative amount of collagen and an increase in stiffness. Although numerous studies have focused on the effect of muscle fibrosis on passive muscle stiffness, few have examined how these structural changes may compromise contractile performance. Here we combine a mathematical model and experimental manipulations to examine how changes in the mechanical properties of the ECM constrain the ability of muscle fibers and fascicles to radially expand and how such a constraint may limit active muscle shortening. We model the mechanical interaction between a contracting muscle and the ECM using a constant volume, pressurized, fiber-wound cylinder. Our model shows that as the proportion of a muscle cross section made up of ECM increases, the muscle’s ability to expand radially is compromised, which in turn restricts muscle shortening. In our experiments, we use a physical constraint placed around the muscle to restrict radial expansion during a contraction. Our experimental results are consistent with model predictions and show that muscles restricted from radial expansion undergo less shortening and generate less mechanical work under identical loads and stimulation conditions. This work highlights the intimate mechanical interaction between contractile and connective tissue structures within skeletal muscle and shows how a deviation from a healthy, well-tuned relationship can compromise performance.     

Genetic markers in studies on dreissenides (Dreissenidae,Bivalvia)

This review summarizes published data on the genetic markers used in studies of dreissenide invasions. Causes of genetic differences between local populations are discussed. It is shown that information about the genetic diversity of populations obtained by marker polymorphism analysis should be compared to study invasion directions.     

Influence of Phytase Transgenic Corn on the Intestinal Microflora and the Fate of Transgenic DNA and Protein in Digesta and Tissues of Broilers

An experiment was conducted to investigate the effect of phytase transgenic corn (PTC) on intestinal microflora, and the fate of transgenic DNA and protein in the digesta and tissues of broilers. A total of 160 1-day-old Arbor Acres commercial male broilers were randomly assigned to 20 cages (8 chicks per cage) with 10 cages (replicates) for each treatment. Birds were fed with a diet containing either PTC (54.0% during 1–21 days and 61.0% during 22–42 days) or non-transgenic isogenic control corn (CC) for a duration of 42 days. There were no significant differences (P>0.05) between birds fed with the PTC diets and those fed with the CC diets in the quantities of aerobic bacteria, anaerobic bacteria, colibacillus and lactobacilli, or microbial diversities in the contents of ileum and cecum. Transgenic phyA2 DNA was not detected, but phyA2 protein was detected in the digesta of duodenum and jejunum of broilers fed with the PTC diets. Both transgenic phyA2 DNA and protein fragments were not found in the digesta of the ileum and rectum, heart, liver, kidney, and breast or thigh muscles of broilers fed with the PTC diets. It was concluded that PTC had no adverse effect on the quantity and diversity of gut microorganisms; Transgenic phyA2 DNA or protein was rapidly degraded in the intestinal tract and was not transferred to the tissues of broilers.     

The role of the epidermal growth factor-1 and hydrophobic stack domains of human factor IX in binding to endothelial cells.

To determine the function and specificity in factor IX of the first epidermal growth factor (EGF)-like domain and the eight-amino acid hydrophobic stack encoded by exon C (residues 39-46), these domains were replaced by the corresponding polypeptide regions of factor X and chimeric proteins were produced in human embryo kidney cells. Both chimeras were activated by factor XIa at a rate similar to plasma factor IX and exhibited calcium-dependent fluorescence quenching similar to plasma factor IX. Both chimeras competed equally for binding to the endothelial cell receptor. Our findings make it unlikely that the first EGF-like domain or the hydrophobic stack of factor IX are responsible for the specific binding of factor IX to its endothelial cell receptor.     

Antiatherogenic action of corn oil in experimental atherosclerosis]

Therapeutic effect of corn oil was studied in rabbits with alimentary atherosclerosis. Corn oil was administered (2 ml/kg, 30 days) after the completion of cholesterol diet unlike studies, where they were administered simultaneously. Total cholesterol, apoB-lipoprotein cholesterol and triglycerides decreased more intensively in rabbits fed by corn oil than in control group. No changes in high-density lipoprotein cholesterol were observed. The most pronounced effect was noted in aorta morphological analysis: an aorta damage degree was 4.8% as compared with 52.9% in the control group. The results show that available plant oils with omega-6 polyunsaturated fatty acids (PUFA), in particular corn oil, may as well as omega-3 PUFA be used as the base for antiatherogenic preparations.     

Comparative study of the changes in microanatomical organization of lymph nodes located and functioning in the area of venous congestion

By the morphometric method the microanatomical organization of the popliteal and kidney lymph nodes of the type Vi was studied in venous congestion. In the first experimental series (lymph nodes localize in venous congestion area) the venous congestion in the popliteal lymph nodes was created by the ligature of caudal vena cava. In the second experimental series (lymph nodes, which clean the venous congestion area--the kidney vena was tied up. The small and short time increase of the marginal sinus volume and hypertrophy of the medullary cords, which seemed about medullary substance B-zone stimulation were characteristically for the lymph nodes, localize in the venous congestion area. The sharp increase of the marginal sinus volume during the long experimental time and paracortical T-zone hyperplasia were characteristically for the lymph nodes, which clean the venous congestion area.