Axial Tubules of Rat Ventricular Myocytes Form Multiple Junctions with the Sarcoplasmic Reticulum

Ryanodine receptors (RyRs) are located primarily on the junctional sarcoplasmic reticulum (SR), adjacent to the transverse tubules and on the cell surface near the Z-lines, but some RyRs are on junctional SR adjacent to axial tubules. Neither the size of the axial junctions nor the numbers of RyRs that they contain have been determined. RyRs may also be located on the corbular SR and on the free or network SR. Because determining and quantifying the distribution of RyRs is critical for both understanding and modeling calcium dynamics, we investigated the distribution of RyRs in healthy adult rat ventricular myocytes, using electron microscopy, electron tomography, and immunofluorescence. We found RyRs in only three regions: in couplons on the surface and on transverse tubules, both of which are near the Z-line, and in junctions on most of the axial tubules—axial junctions. The axial junctions averaged 510 nm in length, but they occasionally spanned an entire sarcomere. Numerical analysis showed that they contain as much as 19% of a cell's RyRs. Tomographic analysis confirmed the axial junction's architecture, which is indistinguishable from junctions on transverse tubules or on the surface, and revealed a complexly structured tubule whose lumen was only 26 nm at its narrowest point. RyRs on axial junctions colocalize with Ca_v1.2, suggesting that they play a role in excitation-contraction coupling.     

MULTIVARIATE PHENOTYPIC DIFFERENTIATION AMONG BOTTLENECK LINES OF THE HOUSEFLY

Multivariate phenotypic differentiation in eight morphometric traits was examined in bottleneck lines of the housefly initiated with one, four, or 16 pairs of flies from a natural outbred population. Differentiation was assessed using a Mahalanobis' distance metric in units of additive genetic variance and covariance estimated from the ancestral population (i.e., generalized genetic distance). This distance metric was partitioned into contributions of size and shape to total distance. Bottleneck lines of all sizes diverged significantly from the ancestral line, but the direction of these shifts differed among the lines of different initial founding size. Those populations founded with single pairs diverged from the ancestral line mostly in shape; the 16-pair lines differentiated almost entirely in size, and the four-pair lines were intermediate in the relative contribution of shape to differentiation from the control. Bottlenecks serve to alter the genetic relationships among traits within the derived populations and in doing so could promote speciation by permitting differentiation of the populations along evolutionary trajectories less accessible to the base population.     

Seismic signal transmission between burrows of the Cape mole-rat,Georychus capensis

Summary Both seismic and auditory signals were tested for their propagation characteristics in a field study of the Cape mole-rat (Georychus capensis), a subterranean rodent in the family Bathyergidae. This solitary animal is entirely fossorial and apparently communicates with its conspecifics by alternately drumming its hind legs on the burrow floor. Signal production in this species is sexually dimorphic, and mate attraction is likely mediated primarily by seismic signalling between individuals in neighboring burrows. Measurements within, and at various distances away from, natural burrows suggest that seismic signals propagate at least an order of magnitude better than auditory signals. Moreover, using a mechanical thumper which could be triggered from a tape recording of the mole-rat's seismic signals, we established that the vertically-polarized surface wave (Rayleigh wave) propagates with less attenuation than either of the two horizontally-polarized waves. Thus, we tentatively hypothesize that Rayleigh waves subserve intraspecific communication in this species.Abbreviations PPM pulses per min - SB simulated burrow - SD standard deviation - SPL sound pressure level     

Evaluation of an innate immune reaction to parasites in earthworms

Encapsulation is an essential process of the invertebrate immune system and includes the prophenoloxidase (proPO) cascade. We present an assay for evaluating this immune response, now newly adapted to earthworms. Coelomic fluid is withdrawn and coelomocytes are stained with l-Dopa. We studied assay repeatability and the correlation between number of PO-active cells and infection level of the parasitic protozoan Monocystis sp. in the earthworm Lumbricus terrestris. Our study showed high assay repeatability although the expected negative relationship between PO-active coelomocytes and parasite load was not observed; yet a suggestion toward a positive relationship was detected. This finding is contrary to previous assumptions that presume coelomocyte concentrations to be the independent variable determining parasite load.     

Divalent metal ion complexes of S100B in the absence and presence of pentamidine

As part of an effort to inhibit S100B, structures of pentamidine (Pnt) bound to Ca²⁺-loaded and Zn²⁺,Ca²⁺-loaded S100B were determined by X-ray crystallography at 2.15 Å (R_free = 0.266) and 1.85 Å (R_free = 0.243) resolution, respectively. These data were compared to X-ray structures solved in the absence of Pnt, including Ca²⁺-loaded S100B and Zn²⁺,Ca²⁺-loaded S100B determined here (1.88 Å; R_free = 0.267). In the presence and absence of Zn²⁺, electron density corresponding to two Pnt molecules per S100B subunit was mapped for both drug-bound structures. One Pnt binding site (site 1) was adjacent to a p53 peptide binding site on S100B (± Zn²⁺), and the second Pnt molecule was mapped to the dimer interface (site 2; ± Zn²⁺) and in a pocket near residues that define the Zn²⁺ binding site on S100B. In addition, a conformational change in S100B was observed upon the addition of Zn²⁺ to Ca²⁺-S100B, which changed the conformation and orientation of Pnt bound to sites 1 and 2 of Pnt-Zn²⁺,Ca²⁺-S100B when compared to Pnt-Ca²⁺-S100B. That Pnt can adapt to this Zn²⁺-dependent conformational change was unexpected and provides a new mode for S100B inhibition by this drug. These data will be useful for developing novel inhibitors of both Ca²⁺- and Ca²⁺,Zn²⁺-bound S100B.     

The effect of aortic valve replacement on quality of life in symptomatic patients with severe aortic stenosis

Background

Although symptomatic patients with severe aortic stenosis have a high disease burden and guidelines recommend aortic valve replacement, many are treated conservatively. This study describes to what extent quality of life is changed by aortic valve replacement relative to conservative treatment.

Methods

This observational study followed 132 symptomatic patients with severe aortic stenosis who were subjected to an SF-36v2TM Health Survey.

Results

At baseline 84 patients were treated conservatively, 48 were referred for aortic valve replacement. In the conservatively treated group 15 patients died during a mean follow-up of 18 months (Kaplan-Meier survival was 85 % and 72 % at one and 2 years respectively) and 22 patients crossed over to the surgical group. Of the resulting 70 patients in the surgical group 3 patients died during a mean follow-up of 11 months (survival 95 % at 1 year). Physical functioning, vitality and general health improved significantly 1 year after aortic valve replacement. In conservatively treated patients physical quality of life deteriorated over time while general health, vitality and social functioning showed a declining trend. Mental health remained stable in both groups.

Conclusions

Aortic valve replacement improves physical quality of life, general health and vitality in patients with symptomatic severe aortic stenosis. Besides having a low life expectancy, conservatively treated patients experience deterioration of physical quality of life. Health surveys such as the SF-36v2TM can be valuable tools in monitoring the burden of disease for an individual patient and offer additional help in treatment decisions.     

Markov chain analysis finds a significant influence of neighboring bases on the occurrence of a base in eucaryotic nuclear DNA sequences both protein-coding and noncoding

Summary Sixty-four eucaryotic nuclear DNA sequences, half of them coding and half noncoding, have been examined as expressions of first-, second-, or third-order Markov chains. Standard statistical tests found that most of the sequences required at least second-order Markov chains for their representation, and some required chains of third order. For all 64 sequences the observed one-step second-order transition count matrices were effective in predicting the two-step transition count matrices, and 56 of 64 were effective in predicting the three-step transition count matrices. The departure from random expectation of the observed first- and second-order transition count matrices meant that a considerable sample of eucaryotic nuclear DNA sequences, both protein coding and noncoding, have significant local structure over subsequences of three to five contiguous bases, and that this structure occurs throughout the total length of the sequence. These results suggested that present DNA sequences may have arisen from the duplication, concatenation, and gradual modification of very early short sequences.     

NHE blockade inhibits chemokine production and NF-kappaB activation in immunostimulated endothelial cells

Na⁺/H⁺exchanger (NHE) activation has been documented to contribute toendothelial cell injury caused by inflammatory states. However, therole of NHEs in regulation of the endothelial cell inflammatoryresponse has not been investigated. The present study tested thehypothesis that NHEs contribute to endothelial cell inflammationinduced by endotoxin or interleukin (IL)-1. NHE inhibition usingamiloride, 5-(N-ethyl-N-isopropyl)-amiloride, and5-(N-methyl-N-isobutyl)amiloride as well as thenon-amiloride NHE inhibitors cimetidine, clonidine, and harmalinesuppressed endotoxin-induced IL-8 and monocyte chemoattractant protein(MCP)-1 production by human umbilical endothelial vein cells (HUVECs). The suppressive effect of amiloride on endotoxin-induced IL-8 production was associated with a decreased accumulation of IL-8 mRNA.NHE inhibitors suppressed both inhibitory (I)B degradation andnuclear factor (NF)-B DNA binding, suggesting that a decrease inactivation of the IB-NF-B system contributed to the suppression of HUVEC inflammatory response by NHE blockade. NHE inhibition decreased also the IL-1-induced HUVEC inflammatory response, becauseamiloride suppressed IL-1-induced E-selectin expression on HUVECs.These results demonstrate that maximal activation of the HUVECinflammatory response requires a functional NHE.