Comparison of oocyte factors and transforming growth factor-beta in the regulation of DNA synthesis in bovine granulosa cells.

Oocytes are powerful local modulators of follicular cell functions and many of the activities of oocytes are attributed to members of the transforming growth factor-beta (TGF-beta) superfamily. Whilst in the mouse it is known that members of this family are able to mimic many of the effects of oocytes on follicular cells, the relative importance of any of these factors is unknown in bovine follicles. The objectives of this study were to determine if bovine oocytes express and secrete TGF-beta and to compare oocyte-secreted factor(s) to TGF-beta in terms of their capacities to stimulate mural granulosa cell (MGC) DNA synthesis. Bovine ovaries were collected from an abattoir and RNA was extracted from isolated MGC, cumulus cells, cumulus-oocyte complexes and denuded oocytes (DO). Using RT-PCR, all cell types were found to express TGF-beta1 and TGF-beta2 mRNA transcripts. However, no TGF-beta bioactivity could be detected from DO using a sensitive (40 pg/ml) and specific mink lung fibroblast cell bioassay. MGC were cultured with various combinations and doses of TGF-beta2 and DO for 18 h, followed by a 6-h pulse of [3H]-thymidine as an indicator of cellular DNA synthesis. MGC DNA synthesis was stimulated by both TGF-beta2 and DO. However in response to increasing doses of TGF-beta2, [3H]-thymidine levels plateaued at <2-fold above control levels, whereas levels continued to increase over the dose range of DO tested (up to 3.4-fold). Addition of a TGF-beta pan-specific neutralising antibody to MGC cultures eliminated the TGF-beta2-stimulatory effects on DNA synthesis and the TGF-beta2-suppressive effects on progesterone production, but the antibody was unable to neutralise the same responses when induced by DO. These results support a role for TGF-beta1, TGF-beta2 and DO in paracrine/autocrine regulation of bovine granulosa cell function, but indicate that neither TGF-beta1 nor TGF-beta2 can account for the actions of bovine oocytes on granulosa cells.

Evidence for the role of PrP(C) helix 1 in the hydrophilic seeding of prion aggregates.

Prions are mammalian proteins (PrPs) with a unique pathogenic property: a nonendogenous isoform PrP(Sc) can catalyze conversion of the endogenous PrP(C) isoform into additional PrP(Sc). In this work, we demonstrate that PrP(C) helix 1 has certain properties (hydrophilicity, charge distribution) that make it unique among all naturally occurring alpha-helices, and which are indicative of a highly specific model of prion infectivity. The beta-nucleation model proposes that PrP(Sc) is an aggregate with a hydrophilic core, consisting of a beta-sheet-like arrangement of constituent helix 1 components. It is suggested by using structural arguments, and confirmed by using CHARMM energy calculations, that aggregate formation from two PrP(C) molecules is highly unfavorable, but the addition of chains to an existing aggregate is favorable. The beta-nucleation model is shown to be consistent with the prion species-barrier, as well as with infectivity data. Sequence analysis of all known protein structures indicates that PrP is uniquely suited to beta-nucleation, in contrast to the many proteins that readily form less favorable (often nonspecific) hydrophobic aggregates.

Design of proteins with selected thermal properties.

BACKGROUND: Methods of model protein design have until now been largely ad hoc, yielding sequences that are foldable only at some seemingly arbitrary simulation temperature. But real proteins exist and must fold within an imposed thermal environment. The need exists for a sequence design method based on statistical-mechanical first principles, thus containing a rigorous treatment of folding temperature. RESULTS: In this work, we report a method of rational sequence design that takes a target structure and a desired optimal folding temperature TZ and generates a sequence that is predicted to be thermodynamically stable with respect to the target structure at a folding temperature TF approximately TZ. This 'cumulant design method' is based on a mean-field high temperature expansion of the molecular partition function. Folding simulations of the designed sequences confirm that sequences designed at TZ do indeed fold optimally when TF approximately TZ. CONCLUSIONS: The cumulant method is highly successful in designing model proteins. It also provides some insight into the thermal properties of real proteins, illuminating the features that distinguish thermostable and psychotropic (cold-loving) sequences from their mesophilic counterparts.

Liver transplantation at UCLA: report of clinical activities.

Liver transplantation remains the treatment of choice for many forms of end-stage liver disease. In most large series, 5-year actuarial survival is greater than 70%. The majority of the morbidity and mortality occurs in the first 6 months posttransplant; as these figures have improved, so have overall survival rates. Infants under 1 year of age have a survival rate below that of older patients; in addition, a severe organ shortage for these patients continues. The use of reduced grafts has ameliorated the problem to a certain extent; however, further expansion of the donor pool is still necessary. Progress has also been made in the postoperative management of transplant patients. We currently follow AKBR and TNF levels in all patients to aid in the diagnosis of primary nonfunction and acute rejection, respectively. The introduction of additional immunosuppressive agents has instigated several large clinical trials. CsA, however, remains the gold standard to which these drugs must be compared.