Engineering Dehydrated Amino Acid Residues in the Antimicrobial Peptide Nisin

The small antimicrobial peptide nisin, produced by Lactococcus lactis, contains the uncommon amino acid residues dehydroalanine and dehydrobutyrine and five thio ether bridges. Since these structures are posttranslationally formed from Ser, Thr, and Cys residues, it is feasible to study their role in nisin function and biosynthesis by protein engineering. Here we report the development of an expression system for mutated nisin Z (nisZ) genes, using nisin A producing L. lactis as a host. Replacement by site-directed mutagenesis of the Ser-5 codon in nisZ by a Thr codon, led to a mutant with a dehydrobutyrine instead of a dehydroalanine residue at position 5, as shown by NMR. Its antimicrobial activity was 2-10-fold lower relative to wild-type nisin Z, depending on the indicator strain used. In another mutagenesis study a double mutation was introduced in the nisZ gene by replacing the codons for Met-17 and Gly-18 by codons for Gln and Thr, respectively, as in the third lanthionine ring of the related antimicrobial peptide subtilin from Bacillus subtilis. This resulted in the simultaneous production of two mutant species, one containing a Thr residue and the other containing a dehydrobutyrine residue at position 18, both having different bacteriocidal properties.

Neo-adjuvant chemotherapy followed by surgery and chemotherapy or by surgery and chemoradiotherapy for patients with resectable gastric cancer (CRITICS)

<p>Abstract</p> <p>Background</p> <p>Radical surgery is the cornerstone in the treatment of resectable gastric cancer. The Intergroup 0116 and MAGIC trials have shown benefit of postoperative chemoradiation and perioperative chemotherapy, respectively. Since these trials cannot be compared directly, both regimens are evaluated prospectively in the CRITICS trial. This study aims to obtain an improved overall survival for patients treated with preoperative chemotherapy and surgery by incorporating radiotherapy concurrently with chemotherapy postoperatively.</p> <p>Methods/design</p> <p>In this phase III multicentre study, patients with resectable gastric cancer are treated with three cycles of preoperative ECC (epirubicin, cisplatin and capecitabine), followed by surgery with adequate lymph node dissection, and then either another three cycles of ECC or concurrent chemoradiation (45 Gy, cisplatin and capecitabine). Surgical, pathological, and radiotherapeutic quality control is performed. The primary endpoint is overall survival, secondary endpoints are disease-free survival (DFS), toxicity, health-related quality of life (HRQL), prediction of response, and recurrence risk assessed by genomic and expression profiling. Accrual for the CRITICS trial is from the Netherlands, Sweden, and Denmark, and more countries are invited to participate.</p> <p>Conclusion</p> <p>Results of this study will demonstrate whether the combination of preoperative chemotherapy and postoperative chemoradiotherapy will improve the clinical outcome of the current European standard of perioperative chemotherapy, and will therefore play a key role in the future management of patients with resectable gastric cancer.</p> <p>Trial registration</p> <p>clinicaltrials.gov <a href="http://www.clinicaltrials.gov/ct2/show/NCT00407186">NCT00407186</a></p

Voluntary disclosure of corporate strategy: determinants and outcomes. An empirical study into the risks and payoffs of communicating corporate strategy.

Business leaders increasingly face pressure from stakeholders to be transparent. There appears however little consensus on the risks and payoffs of disclosing vital information such as corporate strategy. To fill this gap, this study analyzes firm-specific determinants and organisational outcomes of voluntary disclosure of corporate strategy. Stakeholder theory and agency theory help to understand whether companies serve their interest to engage with stakeholders and overcome information asymmetries. I connect these theories and propose a comprehensive approach to measure voluntary disclosure of corporate strategy. Hypotheses from the theoretical framework are empirically tested through panel regression of data on identified determinants and outcomes and of disclosed strategy through annual reports, corporate social responsibility reports, corporate websites and corporate press releases by the 70 largest publicly listed companies in the Netherlands from 2003 through 2008. I found that industry, profitability, dual-listing status, national ranking status and listing age have significant effects on voluntary disclosure of corporate strategy. No significant effects are found for size, leverage and ownership concentration. On outcomes, I found that liquidity of stock and corporate reputation are significantly influenced by voluntary disclosure of corporate strategy. No significant effect is found for volatility of stock. My contributions to theory, methodology and empirics offers a stepping-stone for further research into understanding how companies can use transparency to manage stakeholder relations

The polio eradication effort has been a great success--let's finish it and replace it with something even better.

The polio eradication campaign has greatly reduced the effects of this disease, but many new challenges have emerged. These challenges include the occurrence of polio outbreaks caused by wild-type polioviruses or circulating vaccine-derived polioviruses (cVDPVs) in areas where vaccination coverage is low, the existence of people who excrete poliovirus persistently, and the inability to know definitely that poliovirus has gone. As a result, there is uncertainty about if, when, and how we can end polio immunisation. In this article, we discuss several scenarios for the future of polio control. Because the emergence of cVDPVs necessitates discontinuing the use of live oral polio vaccine, we propose to strive towards a global coverage of near 100% vaccination against all major childhood infections using combination vaccines that contain inactivated poliovirus vaccine. Such a policy will present multiple challenges

Modifications of the 3′-UTR stem–loop of infectious bursal disease virus are allowed without influencing replication or virulence

Many questions regarding the initiation of replication and translation of the segmented, double-stranded RNA genome of infectious bursal disease virus (IBDV) remain to be solved. Computer analysis shows that the non-polyadenylated extreme 3′-untranslated regions (UTRs) of the coding strand of both genomic segments are able to fold into a single stem–loop structure. To assess the determinants for a functional 3′-UTR, we mutagenized the 3′-UTR stem–loop structure of the B-segment. Rescue of infectious virus from mutagenized cDNA plasmids was impaired in all cases. However, after one passage, the replication kinetics of these viruses were restored. Sequence analysis revealed that additional mutations had been acquired in most of the stem–loop structures, which compensated the introduced ones. A rescued virus with a modified stem–loop structure containing four nucleotide substitutions, but preserving its overall secondary structure, was phenotypically indistinguishable from wild-type virus, both in vitro (cell culture) and in vivo (chickens, natural host). Sequence analysis showed that the modified stem–loop structure of this virus was fully preserved after four serial passages. Apparently, it is the stem–loop structure and not the primary sequence that is the functional determinant in the 3′-UTRs of IBDV

Type-specific human papillomavirus infections among young heterosexual male and female STI clinic attendees

BACKGROUND: Baseline genotype-specific human papillomavirus (HPV) prevalence rates and associated risk factors per gender enable future assessment of the impact of vaccination on HPV dynamics. METHODS: Before the start of national HPV vaccination for girls, data were collected cross-sectionally in nationwide Dutch sexually transmitted infections (STI) clinics among heterosexual males (n = 430) and females (n = 1136) aged 16 to 24 years. Self-collected vaginal or penile swabs were analyzed by a sensitive polymerase chain reaction (SPF10) and genotyped with line probe assay. Logistic regression was applied to estimate determinants of HPV prevalent infections. RESULTS: HPV prevalence was 54% among males and 72% among females. High-risk (HR) HPV was present in males and females, 40% and 58%, respectively. Independent risk factors for HR-HPV infection were female gender, number of lifetime sex partners and a history of chlamydia or gonorrhea. In addition, not having a casual partner and consistent condom use were protective factors in women, but not in men. For low-risk (LR) HPV, the odds were smaller. Multiple HR-HPV and sexual risk behavior showed a stronger association compared with a single HR-HPV infection. CONCLUSIONS: Prevalence of HR-HPV is high in both genders. Infection with multiple HR-HPV types was more associated with high-risk sexual behavior than infection with LR-HPV types or a single HR-HPV type