Characterization of chemoselective surface attachment of the cationic peptide melimine and its effects on antimicrobial activity

Antimicrobial peptides (AMPs) are promising alternatives to current treatments for bacterial infections. However, our understanding of the structural–functional relationship of tethered AMPs still requires further investigation to establish a general approach for obtaining consistent antimicrobial surfaces. In this study, we have systematically examined the effects of surface orientation of a broad-spectrum synthetic cationic peptide, melimine, on its antibacterial activity against Gram-positive and Gram-negative bacteria. The attachment of melimine to maleimide-functionalized glass was facilitated by addition of a single cysteine amino acid into the peptide sequence at the N-terminus (CysN) or C-terminus (CysC), or at position 13 (Cys13, approximately central). The successful attachment of the modified melimine was monitored using X-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectrometry (ToF-SIMS) with principle component analysis. The ToF-SIMS analysis clearly demonstrated structural difference between the three orientations. The peptide density for the modified surfaces was found to be between 3.5–4.0 × 10^?9 mol cm^?2 using a modified Bradford assay. The ability of the surfaces to resist Pseudomonas aeruginosa and Staphylococcus aureus colonization was compared using fluorescence confocal microscopy. Reductions in total P. aeruginosa and S. aureus adhesion of 70% (p < 0.001) and 83% (p < 0.001), respectively, after 48 h were observed for the melimine samples when compared to the blank control. We found that melimine attached via the N-terminus was the most effective in reducing total bacterial adhesion and bacterial viability with two- and four times (p < 0.001) more activity than melimine attached via the C-terminus for P. aeruginosa and S. aureus, respectively. Furthermore, for Cys13, despite having the highest measured peptide density of the three surfaces, the higher concentration did not confer the greatest antibacterial effect. This highlights the importance of orientation of the peptides on the surface to efficacy. Our results suggest that the optimal orientation of the cationic residues is essential for maximum surface activity, whereby the optimal activity is obtained when the cationic portion is more available to interact with colonizing bacteria.     

Dose-dependent effect of histamine on liver function markers in immunized rabbits

ObjectiveThe present study was designed to delineate the hepatotoxicological roles of histamine dose-dependently in immunized rabbits.MethodsThe cohort comprised of three groups (II, III and IV), containing 18 rabbits each, and received subcutaneous histamine 50 μg/kg, 100 μg/kg and 200 μg/kg, respectively for 10 days (b.i.d., starting from 3 days prior to immunization until 7 days after immunization). Group I (control, n = 18) received subcutaneous sterile distilled water for 10 days. They were subsequently immunized at day 3 with intravenous injection of SRBC (1 × 10⁹ cells/ml). Blood samples were collected on pre-immunization (pre-I) day 0, as well as on days 7-, 14-, 21-, 28- and 58-post-immunization (post-I). Biochemical parameters aspartate aminotransferase (AST), alanine aminotransferase (ALT), alkaline phosphatase (ALP) and bilirubin [total bilirubin (TB), direct bilirubin (DB) and indirect bilirubin (IB)] were determined.ResultsGroups II and IV revealed a significant decrease (on day 0-pre-I) and a significant increase (on days 7-, 14-, 21-, 28- and 58-post-I) in ALT and AST levels, when compared with the corresponding values of groups I and III while group II showed a significant increase in ALT and AST levels as compared to group IV. ALP levels in groups II, III and IV showed a significant enhancement when compared with group I. Moreover, results of TB, DB and IB demonstrated increased levels in group III when compared with groups I, II and IV. The results were found statistically significant (p < 0.05).ConclusionShort-term treatment of histamine produces dose-dependent differential patterns of hepatic dysfunctions suggestive mild liver degeneration warranting further long-term studies.     

Complex distal 10q rearrangement in a girl with mild intellectual disability: follow up of the patient and review of the literature of non-acrocentric satellited chromosomes

We report on an intellectually disabled girl with a de novo satellited chromosome 10 (10qs) and performed a review of the literature of the non-acrocentric satellited chromosomes (NASC). Satellites and stalks normally occur on the short arms of acrocentric chromosomes; however, the literature cites several reports of satellited non-acrocentric chromosomes, which presumably result from a translocation with an acrocentric chromosome. This is, to our knowledge, the third report of a 10qs chromosome. The phenotype observed in the proband prompted a search for a structural rearrangement of chromosome 10q. By microsatellite analysis we observed a 4 Mb deletion on the long arm of chromosome 10, approximately 145 kb from the telomere. FISH and array CGH analyses revealed a complex rearrangement involving in range from the centromere to the telomere: A 9.64 Mb 10q26.11-q26.2 duplication, a 1.3 Mb region with no copy number change, followed by a 5.62 Mb 10q26.2-q26.3 deletion and a translocation of satellite material. The homology between the repeat sequences at 10q subtelomere region and the sequences on the acrocentric short arms may explain the origin of the rearrangement and it is likely that the submicroscopic microdeletion and microduplication are responsible for the abnormal phenotype in our patient. The patient presented here, with a 15-year follow-up, manifests a distinct phenotype different from the 10q26 pure distal monosomy and trisomy syndromes.     

Allopurinol and superoxide dismutase protect against leucocyte-endothelium interactions in a novel model of colonic ischaemia-reperfusion

BACKGROUND: Leucocyte recruitment is a key feature in ischaemia-reperfusion (I/R)-triggered tissue injury. However, the mechanisms underlying leucocyte-endothelium interactions in the large bowel remain elusive because of a previous lack of models to examine the colonic microcirculation. The aim of this study was to develop and validate a novel method for studying reperfusion-induced leucocyte-endothelium interactions in the colon. METHODS: The superior mesenteric artery was occluded for 30 min in male C57/Bl6 mice and leucocyte responses were analysed in colonic venules after 30-240 min of reperfusion. Analysis of leucocyte rolling and adhesion in colonic venules was made possible by an inverted approach using intravital fluorescence microscopy. RESULTS: Thirty minutes of ischaemia and 120 min of reperfusion induced the strongest and most reproducible increase in leucocyte rolling and adhesion. This was associated with a significant increase in colonic levels of malondialdehyde (MDA). Administration of allopurinol and superoxide dismutase reduced I/R-induced leucocyte responses in a dose-dependent manner. Pretreatment with allopurinol attenuated the tissue content MDA in the colon by more than 60 per cent. CONCLUSION: A new method for examining I/R-induced leucocyte responses in the colonic microcirculation is described. Oxygen free radicals play an important role in triggering leucocyte rolling and adhesion in colonic venules.     

A comparison of 250 and 500 mL of terminal warm blood cardioplegia after global myocardial ischemia: a prospective randomized study

BACKGROUND: Controlled reperfusion with terminal warm blood cardioplegia (TWBC) improves myocardial performance after global ischemia. However, the optimum volume required is unknown. METHODS: Fifty patients undergoing elective coronary artery bypass graft surgery were prospectively randomized to receive either 250 or 500 mL of TWBC. During TWBC delivery, and for 10 minutes after cross-clamp removal, samples were taken from the aorta and coronary sinus to measure the hydrogen ion, lactate, and oxygen content. RESULTS: At the end of TWBC delivery, the 500 mL group had significantly less hydrogen ion washout (p = 0.006) compared with the 250 mL group. Also, more hydrogen ions (p = 0.02) and lactate (p = 0.02) had been washed out during the entire period of TWBC delivery in the 500 mL group compared with the 250 mL, indicating better metabolic recovery. By 4 minutes after aortic cross-clamp removal, hydrogen ion and lactate washout, as well as oxygen extraction was similar in the two groups. However, the time to return to regular mechanical activity was prolonged in the 500 mL group, 5.8 (3) versus 4.6 (3) minutes in the 250 mL group (p = 0.05). Though there was no difference in postoperative Troponin T levels, eight patients in the 500 mL group versus four in the 250 mL group required ionotropic support (p = 0.1). CONCLUSIONS: A total of 500 mL of hotshot achieves a better metabolic state after hotshot delivery. However, there is no clinical benefit or improvement in the postoperative Troponin T release suggesting that in a short ischemic time, 500 mL TWCB has a limited clinical benefit.     

Annular pancreas - a rare cause of gastric obstruction in an 82-year-old patient

Annular pancreas is an uncommon and rarely reported congenital anomaly and thus is rarely suspected. A case is reported of an 82-year-old patient who presented with a 3-month history of nausea and vomiting associated with weight loss who at laparotomy was found to have an annular pancreas.     

Space exploration--surgical insights and future perspectives

NASA's space exploration initiative envisions a return to the moon by 2020, the construction of inhabited lunar bases and manned missions to Mars. Such an ambitious program harbours increased risks, both logistical and physical (particularly that of trauma) within the context of a microgravity environment. This paper also discusses the cellular response to microgravity and the potential scientific and technological benefits of Space exploration.