[The role of Piwi nuclear localization in the differentiation and proliferation of germline stem cells]

The Piwi protein and its orthologs are considered as the key components of the piRNA machinery implicated in transcriptional silencing of transposons. Неre, we show that nuclear localization of the Piwi protein is required not only for transposon repression, but also for proper differentiation of germline stem cells (GSCs). piwi^(Nt) mutation that causes loss of nuclear Piwi and its retention in the cytoplasm leads to the accumulation of undifferentiated GSC-like cells. The analysis of piwi^(Nt) mutation in combination with a bam gene mutation blocking GSC differentiation shows that the loss of nuclear Piwi decreases GSC proliferation rate. This is accompanied by the accumulation of DNA double-strand breaks in GSCs that may be caused by transposition events. Here, for the first time a set of transposons repressed by Piwi in GSCs and surrounding niche cells has been identified. The present study together with our previous data show that nuclear and cytoplasmic Piwi can regulate different stages of the functioning of germinal cells: cytoplasmic Piwi is sufficient to maintain GSCs, while nuclear Piwi localization is necessary for their proper proliferation and differentiation.

Density-optimized radial exponents for X-ray charge-density refinement from ab initio crystal calculations

Structure factors based on periodic density-functional (DFT) calculations on 25 molecular crystals have been used to evaluate trends in refined values of the kappa and kappa' expansion-contraction parameters of the Hansen-Coppens multipole formalism. As found previously and expected physically, the spherical-valence-shell kappa parameters are closely related to the net atomic charges, negative atoms being expanded and vice versa. kappa' parameters, which scale the radial dependence of the non-spherical deformation functions, are remarkably consistent for particular bonding environments. Systematic trends are observed for both carbon and oxygen, but the values obtained for nitrogen show a larger variation. Average values for oxygen and carbon in different bonding environments are tabulated and can be used whenever refinement of experimental data is affected by lack of uniqueness of the charge-density parameter set. Values for nitrogen must be more finely tuned to the specific bonding environment. The relation between atomic charge and kappa offers the possibility of introducing a constraint in the charge-density refinement of very large molecules, for which reduction of the size of the parameter set may be essential.

The experimental charge-density approach in the evaluation of intermolecular interactions. Application of a new module of the XD programming package to several solids including a pentapeptide

A new module interfaced to the XD programming package has been used in the evaluation of intermolecular interactions and lattice energies of the crystals of p-nitroaniline, L-asparagine monohydrate and the pentapeptide Boc-Gln-D-Iva-Hyp-Ala-Phol (Boc = butoxycarbonyl, Iva = isovaline = ethylalanine, Phol = phenylalaninol). The electrostatic interactions are evaluated with the atom-centered distributed multipoles from KRMM (kappa'-restricted multipole model) refinements, using the Buckingham expression for non-overlapping charge densities. Results for p-nitroaniline are compared with Hartree-Fock (HF), density functional (DFT) and Moller-Plesset (MP2) supermolecular calculations and with HF and DFT periodic calculations. The HF and DFT methods fail to predict the stability of the p-nitroaniline crystal but the results of the experimental charge-density approach (ECDA) are in good agreement with both MP2 interaction energies and the experimental lattice energy. ECDA results for L-asparagine monohydrate compare well with those from DFT supermolecular and periodic HF calculations. The disorder of the terminal group in the pentapeptide, which persists at the experimental temperature of 20 K, corresponds to an energy difference of only 0.35 kJ mol(-1), which is too small to be reproduced with current methods.

Autotransplantation of the greater omentum in the treatment of chronic lymphedema

We evaluated the use of transplantation of the greater omentum in the management of chronic lymphedema in 21 patients. The omentum provides a large surface with fluid absorbing capability and potentially therefore is useful in management of patients with primary or hypoplastic peripheral lymphatics. Based on the angio- and lymphangio-architecture of the gastroepiploic architecture, we used large segments of greater omentum as a free autotransplant with microrevascularization to the femoral or axillary artery and vein thereby avoiding technical drawbacks of a pedicle graft with the feeding vessels traversing the abdomen. Elongation of the omentum must be done properly because omental lymphatic arcades do not consistently follow the blood vascular arcades in its more distal part. Accordingly, if not properly mobilized the blood supply may be retained whereas the lymph circulation is interrupted. We combined omental implantation with lymph nodal-venous anastomoses using an omental vein with a nearby systemic venous tributary. In 19 of the 21 patients followed from 3 months to 2 years after operation, remission of lymphedema was good (reduction in swelling more than 50%) in 14 patients and satisfactory in 5 (approximately 25-50% reduction in swelling) with improvement gradually increasing with the passage of time.

Evaluation of the greater omentum in the treatment of experimental lymphedema

Despite advances in microsurgery, the most suitable operation for primary lymphedema remains unclear. A variety of tissue transplants and artificial substances have been used to facilitate drainage of peripheral lymph. The greater omentum, for example, has absorptive lymph draining capability, fights infection, and is expendable for the abdomen. Previous attempts to use the omentum in treatment of clinical lymphedema have, however, been disappointing. This discrepancy between theory and outcome prompted us to reevaluate the role of the omentum in the treatment of chronic lymphedema. In rabbits, mobilization of omentum was carefully examined by three separate techniques and the presence of natural lymph nodal-venous (L-V) shunts determined by an injection of Evans blue into the omentum with sampling later of plasma from the gastroepiploic venous blood. In dogs after promotion of unilateral chronic hindlimb lymphedema by soft tissue excision and sclerosis, the results of four methods of omental transplantation with or without L-V shunt for relief of lymphedema were compared. The results in rabbits suggest that although the greater omentum can be lengthened without jeopardizing its blood supply, it is inappropriate to lengthen it based on blood vascular arcades alone because the omental lymphatics do not strictly follow these arcades in the more distal portion, and with elongation, may be interrupted even though the blood supply remains intact. Moreover, because there is no natural L-V shunt within the greater omentum, the addition of a L-V shunt in dogs in addition to omental transplantation seems to increase effectiveness of the omentum for draining hindlimb lymph after its autotransplantation.

Enteromesenteric bridge in the treatment o primary lymphedema--a case report

Technical details and associated problems of enteromesenteric bridging operation for primary lymphedema (proximal obstructive hypoplasia) are discussed. The short term results are encouraging.