An H-2 haplotype possibly derived by crossing-over between the (A α A β ) duplex and the E βlocus

The B10.STA62 strain carries the H-2 ^w27 haplotype derived from a wild mouse captured in the vicinity of Ann Arbor, Michigan. Products of two class II loci composing this haplotype, A and A , are serologically, biochemically (by tryptic peptide mapping), and functionally indistinguishable from products controlled by the A ^b and A ^/b genes of the B10.A(5R) strain. In contrast, the polypeptide chain controlled by the third class II locus, E , is different from that controlled by the E ^/b gene. This E ^/w27 chain lacks an antigenic determinant present on the E^b molecule and carries determinants lacking on the E^b molecule, the E ^/b and E ^/w27 peptide maps differ in at least six peptides, and cytotoxic T cells specific for the E ^b chains do not react with B10.STA62 target cells. This great difference between the E ^/b and E ^/w27 chains suggests that the corresponding genes have not been derived from one another by a direct mutational conversion; instead, H-2 ^w27 appears to be a recombinant haplotype derived by crossing-over between the A A duplex and the E locus. This is the first recombinant discovered separating these class II loci.     

Specificity of binding of the plectin actin-binding domain to beta4 integrin

Plectin is a major component of the cytoskeleton and links the intermediate filament system to hemidesmosomes by binding to the integrin beta4 subunit. Previously, a binding site for beta4 was mapped on the actin-binding domain (ABD) of plectin and binding of beta4 and F-actin to plectin was shown to be mutually exclusive. Here we show that only the ABDs of plectin and dystonin bind to beta4, whereas those of other actin-binding proteins do not. Mutations of the ABD of plectin-1C show that Q131, R138, and N149 are critical for tight binding of the ABD to beta4. These residues form a small cavity, occupied by a well-ordered water molecule in the crystal structure. The beta4 binding pocket partly overlaps with the actin-binding sequence 2 (ABS2), previously shown to be essential for actin binding. Therefore, steric interference may render binding of beta4 and F-actin to plectin mutually exclusive. Finally, we provide evidence indicating that the residues preceding the ABD in plectin-1A and -1C, although unable to mediate binding to beta4 themselves, modulate the binding activity of the ABD for beta4. These studies demonstrate the unique property of the plectin-ABD to bind to both F-actin and beta4, and explain why several other ABD-containing proteins that are expressed in basal keratinocytes are not recruited into hemidesmosomes.     

Current measures of nutrient resorption efficiency lead to a substantial underestimation of real resorption efficiency: facts and solutions

Nutrient resorption is an important process during leaf senescence, which helps plants to minimize nutrient losses. To quantify nutrient resorption, the parameter resorption efficiency is commonly used. This parameter describes the percentage of the nutrient pool withdrawn before leaf abscission. The nutrient pool is generally expressed on the basis of leaf mass or leaf area, assuming that these bases do not change during senescence. In this paper we firstly present a mathematical formula describing the effect of change in measurement basis on the difference between the real resorption efficiency (RRE) value and the measured resorption efficiency (MRE). This formula shows that even moderate senescence-related changes in a measurement basis can lead to considerable underestimation of RRE. Secondly, to estimate the general change in measurement basis we quantified leaf mass loss and leaf shrinkage during senescence from literature data. These data shows that mass loss percentages can be as high as 40%, and leaf shrinkage can be up to 20%. This level of change in basis seriously compromises the MRE when not corrected for. Using our formula and the reported average literature values of changes in leaf mass (21%) and leaf shrinkage (11%) during senescence, we calculated that the average RRE for nitrogen and phosphorous of terrestrial plants is 6% (leaf area) to 10% (leaf mass) higher than the 50%, respectively 52% as reported by Aerts (1996) . This implies that nutrient resorption from senescing leaves is even more important for nutrient retention in terrestrial plants than thought so far. We advocate that preselecting leaves and monitoring the measurement basis throughout the duration of the experiment should minimize the difference between MRE and RRE.     

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.     

Leukocyte mobilization in mice by polyanions. Decline of leukocyte mobilizing capacity after transplantation of lymphoma

The leukocyte mobilizing polyanions dextran sulphate (DS) and polymethacrylic acid (PMAA) were administered to AKR and (C57BL x CBA) F1 mice at various times after transplantation of syngeneic lymphoma cells. In nonleukaemic mice DS and PMAA increased the number of circulating leukocytes 3--4-fold. The extent of leukocyte mobilization in leukaemic mice depended on the interval between transplantation of the lymphoma cells and injection of the polyanion. During the development of leukaemia in AKR as well as in (C57BL x CBA) F1 mice the capacity to react upon injection of polyanions with leukocyte mobilization gradually decreased. For DS, this decrease started before the number of leukocytes increased in the peripheral blood. On the other hand, the capacity for PMAA-induced leukocyte mobilization was fully preserved for several more days. In heavily leukaemic mice neither DS nor PMAA could further increase the number of peripheral blood leukocytes. In such mice the distribution pattern of leukaemic blast cells, small lymphocytes, granulocytes and monocytes was also hardly or not affected by injection of the polyanion.     

Egg-Laying “Intermorphs” in the Ant Crematogaster smithi neither Affect Sexual Production nor Male Parentage

We study male parentage and between-colony variation in sex allocation and sexual production in the desert ant Crematogaster smithi, which usually has only one singly-mated queen per nest. Colonies of this species are known to temporarily store nutrients in the large fat body of intermorphs, a specialized female caste intermediate in morphology between queens and workers. Intermorphs repackage at least part of this fat into consumable but viable male-destined eggs. If these eggs sometimes develop instead of being eaten, intermorphs will be reproductive competitors of the queen but—due to relatedness asymmetries—allies of their sister worker. Using genetic markers we found a considerable proportion of non-queen sons in some, but not all, colonies. Even though intermorphs produce ∼1.7× more eggs than workers, their share in the parentage of adult males is estimated to be negligible due to their small number compared to workers. Furthermore, neither colony-level sex allocation nor overall sexual production was correlated with intermorph occurrence or number. We conclude that intermorph-laid eggs typically do not survive and that the storage of nutrients and their redistribution as eggs by intermorphs is effectively altruistic.