N'-(3'-monophospho-deoxyguanosin-8-yl)-N-acetylbenzidine formation by peroxidative metabolism

N'-(3'-Monophospho-deoxyguanosin-8-yl)-N-acetylbenzidine (dGp-ABZ) is thought to play an important role in initiation of benzidine-induced bladder cancer in humans. This report assesses the possible formation of this adduct by peroxidatic activation of N-acetylbenzidine (ABZ). Adduct formation was measured by 32P-post-labeling. Ram seminal vesicle microsomes were used as a source of prostaglandin H synthase (PHS). The peroxidatic activity of PHS was compared with that for horseradish peroxidase. Both peroxidases converted ABZ to dGp-ABZ whether DNA or 2'- deoxyguanosine 3'-monophosphate (dGp) was present. Following 32P-post- labeling, the enzymatic and synthetic adduct were extracted from PEI- cellulose plates and were shown to have the same HPLC elution profiles for the bisphosphate adduct (32P-dpGp-ABZ). Treatment of the enzymatic and synthetic bisphosphate adduct with nuclease P1 yielded a product that eluted at the same time from the HPLC (32P-dpG-ABZ). Additional experiments demonstrated that the PHS-derived 5'-monophosphate (dpG- ABZ) and 3'-monophosphate (dGp-ABZ) adducts were also identical to their corresponding synthetic standard. With comparable amounts of total ABZ metabolism, PHS produced approximately 40-fold more dGp-ABZ than horseradish peroxidase (1943 +/- 339 versus 49 +/- 7.8 fmol/mg dGp). Adduct formation was dependent upon the presence of peroxidase and the specific substrate, i.e. arachidonic acid or H2O2. Adduct formation by PHS was inhibited by indomethacin (0.1 mM), ascorbic acid (1 mM) and glutathione (10 mM), but not by 5,5-dimethyl-1-pyrroline N- oxide (DMPO) (100 mM), a radical scavenger. Horseradish peroxidase adduct formation was also inhibited by ascorbic acid and glutathione. In addition, DMPO elicited greater than a 96% inhibition. Results demonstrate peroxidatic metabolism of ABZ to form dGp-ABZ. The mechanism of dGp-ABZ formation by PHS and horseradish peroxidase may be different.      

Optimal pulse motor control

This paper considers the problem of optimal multiple-pulse motor control. Simple pulse-triggering algorithms are derived that are suitable for real-time implementation in air-launched tactical missiles. Two motor designs are addressed. The first is typical of solid radial pulse motor designs, where the number of pulses and the total impulse of each pulse is defined. The second corresponds to a liquid multipulse motor, where the thrust magnitude and total motor impulse are defined and the pulse initiation and pulse termination times are variable. Sensitivity of performance to pulse initiation time and pulse shape is discussed, and simulation results are included to demonstrate the effectiveness of the pulse-triggering algorithms.     

Hepatotoxicity with antibody maytansinoid conjugates: A review of preclinical and clinical findings

Maytansinoids, the potent cytotoxic derivatives of the alkaloid maytansine are used as payloads in antibody maytansinoid conjugates. This article reviews clinical and preclinical hepatotoxicity observed with antibody maytansinoid conjugates used to treat cancer. Specific aspects of drug distribution, metabolism and excretion that may impact hepatotoxicity are reviewed vis‐à‐vis the kind of maytansinoid in the conjugate, cleavable or non‐cleavable linkers, linker–payload combinations, drug to antibody ratio, metabolite formation, hepatic enzyme induction in relation to drug–drug interactions and species, age and gender differences. The article also sheds light on factors that may protect the liver from toxic insults.     

Pilot study of MK-462 in migraine

MK-462 is a potent, selective 5HT_1D receptor agonist which may be useful in treating acute migraine. We conducted a double-blind placebo-controlled inpatient study to assess the preliminary efficacy and safety of oral doses of MK-462 20 mg ( n = 8) and 40 mg ( n =36) vs placebo ( n =21), administered to 65 male and post-menopausal female migraine patients aged 22–51 with moderate or severe migraine headache. Headache severity and functional disability were measured at 0.5, 1, 1.5, and 2 h post-dose. The 20 mg dose was well tolerated and 4/8 patients obtained relief in headache severity at the 2 h time point. The 40 mg dose was well tolerated and was significantly ( p <0.05) superior to placebo at the 1.5 and 2 h time points (with 27/36 or 75% obtaining relief at 2 h compared to 7/21 or 33% for placebo). Adverse events occurred in 50% of patients on 20 mg MK-462, 72% of those on 40 mg MK-462, and in 52% of placebo-treated subjects. The most common adverse events associated with MK-462 were drowsiness (20 mg 12%; 40 mg 44%; placebo 24%), dry mouth (10 mg 36%; placebo 19%), and lightheadedness/dizziness (40 mg 17%; placebo 10%). Based on these preliminary results, MK-462 appears worthy of continued study for the treatment of acute migraine.     

Reduced lysosomal clearance of autophagosomes promotes survival and colonization of Helicobacter pylori

Evasion of autophagy is key for intracellular survival of bacteria in host cells, but its involvement in persistent infection by Helicobacter pylori, a bacterium identified to invade gastric epithelial cells, remains obscure. The aim of this study was to functionally characterize the role of autophagy in H. pylori infection. Autophagy was assayed in H. pylori‐infected human gastric epithelium and the functional role of autophagy was determined via genetic or pharmacological ablation of autophagy in mouse and cell line models of H. pylori infection. Here, we showed that H. pylori inhibited lysosomal function and thereby promoted the accumulation of autophagosomes in gastric epithelial cells. Importantly, inhibiting autophagosome formation by pharmacological inhibitors or genetic ablation of BECN1 or ATG5 reduced H. pylori intracellular survival, whereas inhibition of lysosomal functions exerted an opposite effect. Further experiments demonstrated that H. pylori inhibited lysosomal acidification and the retrograde trafficking of mannose‐6‐phosphate receptors, both of which are known to positively regulate lysosomal function. We conclude that H. pylori subverts autophagy into a pro‐survival mechanism through inhibition of lysosomal clearance of autophagosomes. Disruption of autophagosome formation offers a novel strategy to reduce H. pylori colonization in human stomachs. Copyright © 2018 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.     

Orthotopic aortic transplantation in mice: a new model of allograft arteriosclerosis.

BACKGROUND: Graft arteriosclerosis is a major cause of death after allotransplantation of organs such as the heart or the kidney. Aortic allotransplantation in mice is a useful experimental model to study the mechanisms of this pathology. However, the conventional heterotopic aortic model is limited by a high morbidity and is technically difficult to perform. We developed a new simple method for aortic transplantation in mice. METHODS: The infrarenal aorta from the donor mouse was anastomosed to the recipient's aorta at the same position using a sleeve technique. Orthotopic aortic transplantation was performed in 45 mice, 5 isografts and 40 allografts. No immunosuppression was given, and the mice were killed at day 15 or 30. The graft was examined macroscopically, and several histologic sections were made. RESULTS: The overall survival rate was 78%. The incidence of thrombosis was low (4 cases) compared with previously published series. Histology of aortas revealed typical aspects of rejection in the allografts with a chronic picture at day 30. No significant lesion was observed in isografts. CONCLUSIONS: We have developed a model of orthotopic aortic transplantation in mice. This new model is easy to carry out and has a low incidence of thrombosis, probably because there is no size discrepancy between donor and recipient aortic segment.     

Triple-layer Mesh Plasty for Re-recurrent Ventral Hernia in a Liver Transplant Patient: A Case Report

Ventral hernias often occur in transplanted patients because of weakness of the abdominal wall, poor muscle mass, and ascitis. In this report we describe the case of a re-recurrent ventral hernia seen emergently in a liver transplant recipient, who was treated using a singular 3-layer approach by placement of an intraperitoneal mesh, stressing technical aspects of the plasty as well as the importance of a sublay technique in the reinforcement of a previous prosthetic plasty.     

Load transfer in tilted implants with varying cantilever lengths in an all‐on‐four situation

Background: The aim of this study was to evaluate if tilting of the distal implant at different angulations (30° and 40°) with different cantilever lengths (4 mm and 12 mm) affects the stress and strain distribution in an ‘all‐on‐four’ situation. Methods: A completely edentulous mandible was modelled with four tapered implants placed within the interforaminal region to receive an all acrylic fixed prosthesis. The two posterior implants were tilted at an angle of 30° and 40°. The prosthesis cantilever was given two different variables of 4 mm and 12 mm. For all models, the equivalent von Mises stress and strain was analysed using three‐dimensional finite element analysis. Results: Statistical significance (p < 0.05) was seen when a comparison was made for the stress developed on the implant and cortical bone between the 30° and 40° distally tilted posterior implants in both situations. No significance was seen in the trabecular bone and on the strain developed in these situations. Conclusions: The study shows that increasing the tilt of the distal implants does not increase the stress significantly. It also shows that the architecture of the mandible plays a major role during treatment planning of a completely edentulous patient.     

Liver tissue engineering and cell sources: issues and challenges

Liver diseases are of major concern as they now account for millions of deaths annually. As a result of the increased incidence of liver disease, many patients die on the transplant waiting list, before a donor organ becomes available. To meet the huge demand for donor liver, alternative approaches using liver tissue engineering principles are being actively pursued. Even though adult hepatocytes, the primary cells of the liver are most preferred for tissue engineering of liver, their limited availability, isolation from diseased organs, lack of in vitro propagation and deterioration of function acts as a major drawback to their use. Various approaches have been taken to prevent the functional deterioration of hepatocytes including the provision of an adequate extracellular matrix and co‐culture with non‐parenchymal cells of liver. Great progress has also been made to differentiate human stem cells to hepatocytes and to use them for liver tissue engineering applications. This review provides an overview of recent challenges, issues and cell sources with regard to liver tissue engineering.     

A prenylated flavanone from dalea elegans inhibits rhodamine 6 G efflux and reverses fluconazole-resistance in Candida albicans

In previous studies, 2',4'-dihydroxy-5'-(1',1'-dimethylallyl)-6-prenylpinocembrin, a prenylated flavonoid isolated from Dalea elegans roots, showed activity against multiresistant Staphylococcus aureus and Candida albicans, as well as an uncoupling effect on mitochondria and antioxidant activity. The aim of this study was to evaluate the inhibitory effects of 2',4'-dihydroxy-5'-(1',1'-dimethylallyl)-6-prenylpinocembrin and fluconazole on the efflux of rhodamine 6 G in azole-resistant C. albicans 12-99 that expresses multidrug transporters Cdr1p, Cdr2p, and Mdr1p. The effect of fluconazole and 2',4'-dihydroxy-5'-(1',1'-dimethylallyl)-6-prenylpinocembrin on rhodamine 6 G efflux was assessed in both azole-sensitive and azole-resistant C. albicans. Between 1 and 1000 μM, 2',4'-dihydroxy-5'-(1',1'-dimethylallyl)-6-prenylpinocembrin inhibited rhodamine 6 G efflux only in azole-resistant C. albicans 12-99 in a concentration-dependent manner (IC50 = 119 μM); a competitive effect was observed. It also showed selectivity of action in comparison with other flavanones (6-prenylpinocembrin, isolated from aerial parts of D. elegans, pinocembrin, naringenin, and hesperetin, all at 250 μM). To check the possible implications of the inhibition of azole efflux on cell growth, antifungal assays were conducted. Minimal inhibitory concentration values were 150 μM for 2',4'-dihydroxy-5'-(1',1'-dimethylallyl)-6-prenylpinocembrin and higher than 400 μM for fluconazole. The combination of both compounds at either inhibitory or subinhibitory concentrations was significantly more effective than each compound separately. Minimal inhibitory concentration for fluconazole decreased by more than 400 times in the presence of 100 μM 2',4'-dihydroxy-5'-(1',1'-dimethylallyl)-6-prenylpinocembrin, reversing azole resistance and giving values similar to those of azole-sensitive C. albicans. These data are consistent with a dual action of 2',4'-dihydroxy-5'-(1',1'-dimethylallyl)-6-prenylpinocembrin: direct antifungal effect on azole-resistant C. albicans 12-99 and inhibition of azole transporters, which results in reversion of fluconazole resistance.