Relationship of physical fitness, hormone replacement therapy, and hemostatic risk factors in postmenopausal women.

This cross-sectional study evaluated the relationship of physical fitness, hormone replacement therapy (HRT), and hemostatic profiles at rest and after an acute bout of maximal exercise in 48 healthy postmenopausal women. Subjects were categorized by fitness and HRT user status into four groups: unfit nonusers, fit nonusers, unfit users, and fit users. Fibrinolytic variables tissue plasminogen activator (tPA), plasminogen activator inhibitor-1 (PAI-1) activity, and antigen and prothrombin fragment 1 + 2, a molecular marker of in vivo thrombin generation, were measured before and after maximal exercise. Fibrinogen was also measured at rest. Higher tPA and lower PAI-1 activities (P <0.05) were seen in HRT users and fit groups. tPA and PAI-1 antigens were lower in HRT and fit groups (P <0.05) but not after correction for body mass index. Prothrombin fragment 1 + 2 was lower in the fit groups regardless of HRT status (P <0.05). Fibrinogen was similar in all groups. Favorable hemostatic profiles were observed in physically fit compared with unfit women, especially in HRT nonusers. Thus fitness is more strongly related to these hemostatic risk factors compared with HRT since HRT did not affect these hemostatic variables in fit postmenopausal women.     

Optimizing purebred selection for crossbred performance using QTL with different degrees of dominance

A method was developed to optimize simultaneous selection for a quantitative trait with a known QTL within a male and a female line to maximize crossbred performance from a two-way cross. Strategies to maximize cumulative discounted response in crossbred performance over ten generations were derived by optimizing weights in an index of a QTL and phenotype. Strategies were compared to selection on purebred phenotype. Extra responses were limited for QTL with additive and partial dominance effects, but substantial for QTL with over-dominance, for which optimal QTL selection resulted in differential selection in male and female lines to increase the frequency of heterozygotes and polygenic responses. For over-dominant QTL, maximization of crossbred performance one generation at a time resulted in similar responses as optimization across all generations and simultaneous optimal selection in a male and female line resulted in greater response than optimal selection within a single line without crossbreeding. Results show that strategic use of information on over-dominant QTL can enhance crossbred performance without crossbred testing.     

ECM Protein Nanofibers and Nanostructures Engineered Using Surface-initiated Assembly

The extracellular matrix (ECM) in tissues is synthesized and assembled by cells to form a 3D fibrillar, protein network with tightly regulated fiber diameter, composition and organization. In addition to providing structural support, the physical and chemical properties of the ECM play an important role in multiple cellular processes including adhesion, differentiation, and apoptosis. In vivo, the ECM is assembled by exposing cryptic self-assembly (fibrillogenesis) sites within proteins. This process varies for different proteins, but fibronectin (FN) fibrillogenesis is well-characterized and serves as a model system for cell-mediated ECM assembly. Specifically, cells use integrin receptors on the cell membrane to bind FN dimers and actomyosin-generated contractile forces to unfold and expose binding sites for assembly into insoluble fibers. This receptor-mediated process enables cells to assemble and organize the ECM from the cellular to tissue scales. Here, we present a method termed surface-initiated assembly (SIA), which recapitulates cell-mediated matrix assembly using protein-surface interactions to unfold ECM proteins and assemble them into insoluble fibers. First, ECM proteins are adsorbed onto a hydrophobic polydimethylsiloxane (PDMS) surface where they partially denature (unfold) and expose cryptic binding domains. The unfolded proteins are then transferred in well-defined micro- and nanopatterns through microcontact printing onto a thermally responsive poly(N-isopropylacrylamide) (PIPAAm) surface. Thermally-triggered dissolution of the PIPAAm leads to final assembly and release of insoluble ECM protein nanofibers and nanostructures with well-defined geometries. Complex architectures are possible by engineering defined patterns on the PDMS stamps used for microcontact printing. In addition to FN, the SIA process can be used with laminin, fibrinogen and collagens type I and IV to create multi-component ECM nanostructures. Thus, SIA can be used to engineer ECM protein-based materials with precise control over the protein composition, fiber geometry and scaffold architecture in order to recapitulate the structure and composition of the ECM in vivo.     

Effect of postnatal development on calcium currents and slow charge movement in mammalian skeletal muscle

Single- (whole-cell patch) and two-electrode voltage-clamp techniques were used to measure transient (Ifast) and sustained (Islow) calcium currents, linear capacitance, and slow, voltage-dependent charge movements in freshly dissociated fibers of the flexor digitorum brevis (FDB) muscle of rats of various postnatal ages. Peak Ifast was largest in FDB fibers of neonatal (1-5 d) rats, having a magnitude in 10 mM external Ca of 1.4 +/- 0.9 pA/pF (mean +/- SD; current normalized by linear fiber capacitance). Peak Ifast was smaller in FDB fibers of older animals, and by approximately 3 wk postnatal, it was so small as to be unmeasurable. By contrast, the magnitudes of Islow and charge movement increased substantially during postnatal development. Peak Islow was 3.6 +/- 2.5 pA/pF in FDB fibers of 1-5-d rats and increased to 16.4 +/- 6.5 pA/pF in 45-50-d-old rats; for these same two age groups, Qmax, the total mobile charge measurable as charge movement, was 6.0 +/- 1.7 and 23.8 +/- 4.0 nC/microF, respectively. As both Islow and charge movement are thought to arise in the transverse-tubular system, linear capacitance normalized by the area of fiber surface was determined as an indirect measure of the membrane area of the t-system relative to that of the fiber surface. This parameter increased from 1.5 +/- 0.2 microF/cm2 in 2-d fibers to 2.9 +/- 0.4 microF/cm2 in 44-d fibers. The increases in peak Islow, Qmax, and normalized linear capacitance all had similar time courses. Although the function of Islow is unknown, the substantial postnatal increase in its magnitude suggests that it plays an important role in the physiology of skeletal muscle.     

Calmodulin isoforms in Arabidopsis encoded by multiple divergent mRNAs

Three new, unique cDNA sequences encoding isoforms of calmodulin (CaM) were isolated from an Arabidopsis cDNA library cloned in gt10. These sequences (ACaM-4, -5, and -6) represent members of the Arabidopsis CaM gene family distinct from the three DNA sequences previously reported. ACaM-4 and -6 encode full-length copies of CaM mRNAs of ca. 0.75 kb. The ACaM-5 sequence encodes a partial length copy of CaM mRNA that is lacking sequences encoding the amino-terminal 10 amino acids of mature CaM and the initiator methionine. The derived amino acid sequence of ACaM-5 is identical to the sequences encoded by two of the previously characterized ACaM cDNAs, and is identical to TCH-1 mRNA, whose accumulation was increased by touch stimulation. The polypeptides encoded by ACaM-4 and -6 differ from that encoded by ACaM-5 by six and two amino acid substititions, respectively. Most of the deduced amino acid sequence substitutions in the Arabidopsis CaM isoforms occurred in the fourth Ca²⁺-binding domain. Polymerase chain reaction amplification assays of ACaM-4, -5 and -6 mRNA sequences indicated that each accumulated in Arabidopsis leaf RNA fractions, but only ACaM-4 and -5 mRNAs were detected in silique total RNA. The six different CaM cDNA sequences each hybridize with unique Eco RI restriction fragments in genomic Southern blots of Arabidopsis DNA, indicating that these sequences were derived from distinct structural genes. Our results suggest that CaM isoforms in Arabidopsis may have evolved to optimize the interaction of this Ca²⁺-receptor protein with specific subsets of response elements.     

Effect of the pacing interval and extrasystole on amplitude and damping of diastolic oscillations in the rabbit papillary muscle

Diastolic mechanical oscillations of right ventricular rabbit papillary muscles investigated at 15 degrees C in the perfusion chamber were analysed using a relaxation model with 6 parameters. From this analysis follows that the first diastolic oscillation amplitude plotted against the driving interval ("interval amplitude curve" of the first diastolic oscillation) shows tow maxima thus differing from the shape of the interval strength curve of the preceding driven contraction. It is concluded that the amplitude of diastolic oscillations is less determined by the Ca-amount released from the sarcoplasmic reticulum during the action potential than by the frequency of processes which effect the Ca release and the Ca-sequestration. The damping ratio varies within the range of tested driving intervals (0.36 to 10 s). After an extrasystole damping ratio and period of diastolic oscillation are diminished compared with the values after regularly driven contractions.     

Human retinal vascular cells differ from umbilical cells in synthetic functions and their response to glucose.

Cell culture systems have commonly been used to study mechanisms implicated in the pathogenesis of diabetic retinopathy, but the great majority of cell preparations used have been either of nonhuman retinal origin or nonretinal human origin. Because of questions of species and organ specificity in the function of cells of vascular origin, in this study, cultured microvascular endothelial cells (HREC), pericytes (HRPC), and pigment epithelial cells from the postmortem human retina, and endothelial cells from human umbilical vein (HUVEC) were evaluated with respect to cell proliferation, and secretory products potentially important in diabetic retinopathy, i.e., prostaglandins (PG) and plasminogen activators (PA), normalized to DNA content/well, under both basal (5 mM) and high (25 mM) glucose conditions. Glucose (25 mM) reduced DNA content similarly in both types of endothelial cells, had a lesser effect on HRPC, and did not significantly alter the proliferation of pigment epithelial cells. Basal secretion of PGI2 (measured as 6-keto-PGF1 alpha) was in the order HRPC much greater than HREC greater than HUVEC, whereas PGE2 secretion was in the order HREC much greater than HRPC greater than HUVEC. Glucose (25 mM) stimulated PGI2 secretion by HRPC, but not by either type of endothelial cell, and enhanced PGE2 secretion by HREC, but not by HUVEC or HRPC. Release of plasminogen activator activity differed between HUVEC and HREC under basal conditions and addition of 25 mM glucose stimulated release only from HREC. Glucose (25 mM) stimulated PA secretion by HREC, but not by HUVEC. These findings provide evidence that human retinal pericytes are an important source of prostacyclin, and that there are differences between HREC and HUVEC with respect to secretory functions and their modulation by glucose, indicating regional specificity of these functions. Extrapolation to human retinal vascular cells from experiments using cells from heterologous vascular beds to draw inferences about the pathophysiology of diabetic retinopathy are not valid for these cellular functions.     

A study on the minimum number of loci required for genetic evaluation using a finite locus model

For a finite locus model, Markov chain Monte Carlo (MCMC) methods can be used to estimate the conditional mean of genotypic values given phenotypes, which is also known as the best predictor (BP). When computationally feasible, this type of genetic prediction provides an elegant solution to the problem of genetic evaluation under non-additive inheritance, especially for crossbred data. Successful application of MCMC methods for genetic evaluation using finite locus models depends, among other factors, on the number of loci assumed in the model. The effect of the assumed number of loci on evaluations obtained by BP was investigated using data simulated with about 100 loci. For several small pedigrees, genetic evaluations obtained by best linear prediction (BLP) were compared to genetic evaluations obtained by BP. For BLP evaluation, used here as the standard of comparison, only the first and second moments of the joint distribution of the genotypic and phenotypic values must be known. These moments were calculated from the gene frequencies and genotypic effects used in the simulation model. BP evaluation requires the complete distribution to be known. For each model used for BP evaluation, the gene frequencies and genotypic effects, which completely specify the required distribution, were derived such that the genotypic mean, the additive variance, and the dominance variance were the same as in the simulation model. For lowly heritable traits, evaluations obtained by BP under models with up to three loci closely matched the evaluations obtained by BLP for both purebred and crossbred data. For highly heritable traits, models with up to six loci were needed to match the evaluations obtained by BLP.     

Various critical comments on the interpretation of staircase- and potentiation phenomena in the rabbit heart muscle]

Some critical remarks on the interpretation of staircase and potentiation phenomena (rabbit heart muscle). Isometric contractions of rabbit papillary muscles and atrial strips were investigated at temperatures from 13.2 degrees C to 35 degrees C after rests of different duration at constant stimulation frequency before rest, in a period after rest and in a transition phase following a step of stimulation frequency. Changes in potentiation as well as changes in dynamics after rest and dynamics after steps of stimulation frequency are caused by lowering the temperature. Any hypothesis on the subject of Ca-movements between intracellular stores would have to account for changes in potentiation, staircase phenomena and the development of after-contractions at low temperatures.