Femoral prosthesis neck fracture following total hip arthroplasty - a systematic review.

PURPOSE: Head-neck modularity was introduced into total hip arthroplasty to provide more intraoperative surgical options. However, modularity led to new problems, such as trunnionosis and fractures of the femoral prosthesis neck. The purpose of this study was to identify risk factors for hip neck fractures and to provide recommendations to prevent damage and fractures of the neck. METHODS: A systematic review of the literature was performed according to the PRISMA guidelines. RESULTS: Thirty-three case studies were included. Methodologically, most included studies were of moderate or good quality. The 80 neck fractures included in the review took place, on average, 7 years after stem placement. Male gender, high body weight, obesity, previous revision surgery, mixing components from different manufacturers, use of long skirted heads, cobalt-chromium (large size) heads were identified as potential risk factors. CONCLUSION: Hip neck fractures occur on average 7 years after stem placement. The etiology of hip neck fractures is multifactorial. This review revealed several preventable implant- and surgeon-related risk factors.

Empirical investigation of preparations produced according to the European Pharmacopoeia monograph 1038.

According to the European Pharmacopoeia monograph 1038 (Praeparationes homoeopathicae), homeopathic preparations are produced by successive dilution and succussion steps. Dilution levels beyond Avogadro's limit, however, render specific effects implausible according to standard scientific knowledge. Accordingly, we were interested in a critical empirical investigation of preparations produced according to this monograph. Within a precursor study we developed a bioassay based on a fingerprint metabolomic analysis of Lepidium sativum seeds germinated in vitro in either homeopathic preparations or controls in a blinded and randomized assignment. Results of the precursor study were not consistent with the hypothesis that the effects of a Stannum metallicum 30x preparation are identical to placebo. In the present study we investigated the reproducibility of these effects after scrutinizing and optimizing experimental procedures. Ten independent experiments were performed in a blinded and randomized assignment in two independent laboratories. Additionally, 10 systematic negative water control experiments were performed in both laboratories to critically assess the stability of the experimental set-up. The effects of the Stannum metallicum 30x treatment were reproduced. The systematic negative control experiments did not yield false-positive results, indicating a stable experimental set-up. We thus repeatedly observed biological effects conflicting with the assumption that Stannum metallicum 30x is identical to placebo. We therefore wish to discuss whether these findings are to be considered a scientific anomaly or whether they might stimulate further investigations to clarify whether application of the European Pharmacopoeia monograph 1038 may result in pharmaceutical preparations with specific effects.

Development of a biocrystallisation assay for examining effects of homeopathic preparations using cress seedlings.

A major challenge in basic research into homeopathic potentisation is to develop bioassays that yield consistent results. We evaluated the potential of a seedling-biocrystallisation method. Cress seeds (Lepidium sativum L.) germinated and grew for 4 days in vitro in Stannum metallicum 30x or water 30x in blinded and randomized assignment. 15 experiments were performed at two laboratories. CuCl(2)-biocrystallisation of seedlings extracted in the homeopathic preparations was performed on circular glass plates. Resulting biocrystallograms were analysed by computerized textural image analysis. All texture analysis variables analysed yielded significant results for the homeopathic treatment; thus the texture of the biocrystallograms of homeopathically treated cress exhibited specific characteristics. Two texture analysis variables yielded differences between the internal replicates, most probably due to a processing order effect. There were only minor differences between the results of the two laboratories. The biocrystallisation method seems to be a promising complementary outcome measure for plant bioassays investigating effects of homeopathic preparations.

Mechanisms of androgen receptor activation and function.

Androgens play a crucial role in several stages of male development and in the maintenance of the male phenotype. Androgens act in their target cells via an interaction with the androgen receptor, resulting in direct regulation of gene expression. The androgen receptor is a phosphoprotein and modulation of the phosphorylation status of the receptor influences ligand-binding and consequently transcription activation of androgen responsive genes. Androgen binding induces a conformational change in the ligand-binding domain, accompanied by additional receptor phosphorylation. Subsequently the liganded androgen receptor interacts with specific androgen response elements in the regulatory regions of androgen target genes, resulting in stimulation of gene expression. Anti-androgens induce a different conformational change of the ligand-binding domain, which does not or only partially result in stimulation of transactivation. Interestingly, different anti-androgens can induce different inactive conformations of the androgen receptor ligand-binding domain. Recent evidence strongly supports a ligand dependent functional interaction between the ligand-binding domain and the NH2-terminal transactivating domain of the androgen receptor. Two regions in the NH2-terminal domain are involved in this interaction, whereas in the ligand-binding domain the AF-2 AD core region is involved.

Functional interactions of the AF-2 activation domain core region of the human androgen receptor with the amino-terminal domain and with the transcriptional coactivator TIF2 (transcriptional intermediary factor2).

Previous studies in yeast and mammalian cells showed a functional interaction between the amino-terminal domain and the carboxy-terminal, ligand-binding domain (LBD) of the human androgen receptor (AR). In the present study, the AR subdomains involved in this in vivo interaction were determined in more detail. Cotransfection experiments in Chinese hamster ovary (CHO) cells and two-hybrid experiments in yeast revealed that two regions in the NH2-terminal domain are involved in the functional interaction with the LBD: an interacting domain at the very NH2 terminus, located between amino acid residues 3 and 36, and a second domain, essential for transactivation, located between residues 370 and 494. Substitution of glutamic acid by glutamine at position 888 (E888Q) in the AF-2 activation domain (AD) core region in the LBD, markedly decreased the interaction with the NH2-terminal domain. This mutation neither influenced hormone binding nor LBD homodimerization, suggesting a role of the AF-2 AD core region in the functional interaction between the NH2-terminal domain and the LBD. The AF-2 AD core region was also involved in the interaction with the coactivator TIF2 (transcriptional intermediary factor 2), as the E888Q mutation decreased the stimulatory effect of TIF2 on AR AF-2 activity. Cotransfection of TIF2 and the AR NH2-terminal domain expression vectors did not result in synergy between both factors in the induction of AR AF-2 activity. TIF2 highly induced AR AF-2 activity on a complex promoter [mouse mammary tumor virus (MMTV)], but it was hardly active on a minimal promoter (GRE-TATA). In contrast, the AR NH2-terminal domain induced AR AF-2 activity on both promoter constructs. These data indicate that both the AR NH2-terminal domain and the coactivator TIF2 functionally interact, either directly or indirectly, with the AF-2 AD core region in the AR-LBD, but the level of transcriptional response induced by TIF2 depends on the promoter context.

Functional in vivo interaction between the amino-terminal, transactivation domain and the ligand binding domain of the androgen receptor.

The ligand binding domain (LBD) and the amino-terminal, transactivation domain (TAD) of the androgen receptor (AR) were separately linked to the GAL4 DNA binding domain (DBD) and to the GAL4(TAD). Resulting constructs were tested in the yeast two-hybrid system for protein-protein interactions. In the presence of androgen [methyltrienolone (R1881) or dihydrotestosterone (DHT)] a transcriptionally active complex was formed, reflecting an association between the AR(LBD) and the AR(TAD). No interactions were found in the presence of low-affinity ligands like estradiol (E2), promegestone (R5020), or progesterone (Pg). Use of the Thr-868-Ala mutated AR(LBD) in the assay resulted not only in a clear AR TAD-LBD interaction in the presence of R1881 and DHT but also in the presence of E2, Pg, and R5020, corresponding to the alteration in ligand specificity induced by the mutation. Coexpression of the fusion protein Gal4(DBD)AR(LBD) and the separate AR(TAD) also gave rise to the formation of a transcriptionally active complex. No interactions were found between two AR LBDs at the low-expression level of the two components. However, LBD-LBD interaction was detectable by application of a high-expression vector for GAL4(TAD)AR(LBD), albeit at high ligand concentrations. To substantiate the observation of the AR LBD-TAD interaction, CHO cells were cotransfected with expression plasmids for a truncated AR, which lacks the TAD [AR(DBD)(LBD)], and for the separate AR(TAD). This resulted in stimulation of a MMTV-LUC reporter gene in the presence of R1881 but not in the absence of hormone. This finding indicates that, like in the yeast system, in mammalian cells, TAD-LBD interactions are of importance for AR activation. In the mammalian system, a maximal AR TAD-LBD interaction was obtained at approximately 10-fold higher ligand concentrations than required for full-length AR activation. In the presence of low-affinity ligands, the AR TAD-LBD interaction as measured by transcriptional activation was considerably weaker than the activity of the full-length AR. From the present results a concept of hormone-dependent AR activation is proposed, which requires a functional, direct or indirect intramolecular interaction between the TAD and the LBD.

Evidence for a large dispensable segment in the subtilisin-like catalytic domain of the Lactococcus lactis cell-envelope proteinase.

The Lactococcus lactis SK11 cell-envelope proteinase contains various inserts, located in external loops of the catalytic domain compared with related subtilisins. In this study, protein engineering was employed to determine the function of the largest loop insertion (residues 238-388) relative to the subtilisin structure. By site-directed mutagenesis we have deleted the fragment of the proteinase gene encoding these 151 residues and analyzed the mutant delta 238-388 proteinase for activity, (auto)processing and cleavage specificity. This extra segment is found to be inessential for activity, and its removal does not inhibit folding as the mutant proteinase is still active. In addition, the N- and C-terminal autoprocessing of the delta 238-388 proteinase appears to be unchanged. However, removal of residues 238-388 altered substantially the caseinolytic specificity of the enzyme, indicating that this extra segment influences substrate specificity. Residues 238-388 were shown to contain a specific epitope for a monoclonal antibody.