Synthesis, Electrochemistry, and Bioactivity of the Cyanobacterial Calothrixins and Related Quinones

The calothrixins are quinone-based natural products isolated from Calothrix cyanobacteria which show potent antiproliferative properties against several cancer cell lines. Preliminary mechanistic studies suggest that the biological mode of action of the calothrixins may be linked to their ability to undergo redox cycling. In this study we compare the bioactivities of the calothrixins with those of structurally related quinones in order to identify the structural features in the calothrixins essential for biological activity. In particular, the reduction potentials of the calothrixins and some related quinones were measured electrochemically. Our studies indicate that while there is no direct correlation between the reduction potentials and biological activities of the studied compounds, in all cases quinones with EC(50) values <1.6 microM undergo reduction to their respective semiquinones readily, with their E(1/2) values being more positive than -0.5 V versus the standard hydrogen electrode (SHE).

A novel redox mechanism for the glutathione-dependent reversible uptake of a fungal toxin in cells

The fungal metabolite gliotoxin is characterized by an internal disulfide bridge and can exist in either disulfide or dithiol forms. Gliotoxin and other members of the epipolythiodioxopiperazine class of toxins have immunosuppressive properties and have been implicated in human and animal mycotoxicoses. The bridged disulfide moiety is thought to be generally essential for biological activity. Here we show that only the natural (oxidized) form of gliotoxin is actively concentrated in a cell line in a glutathione-dependent manner. Intracellular levels of the toxin can be up to 1500-fold greater than the applied concentration, and toxin in the cells exists almost exclusively in the reduced form. A simple model of toxin entry followed by reduction to the cell-impermeant dithiol explains active uptake, cell density dependence of EC50 values and predicts a value for the maximum concentration of toxin at limiting cell density in agreement with the experiment. Oxidation of the intracellular toxin results in rapid efflux from the cell that also occurs when glutathione levels fall following induction of apoptotic cell death by the toxin. This mechanism allows for minimal production of the toxin while enabling maximal intracellular concentration and thus maximal efficacy of killing in a competitor organism initially present at low cell density. The toxin effluxes from the apoptotic cell exclusively in the oxidized form and can further enter and kill neighboring cells, thus acting in a pseudocatalytic way.

Structure–activity delineation of quinones related to the biologically active Calothrixin B

Quinones such as Calothrixins A and B display a range of biological properties. As part of our ongoing studies to elucidate the mechanism of action of the Calothrixins, several related quinones were synthesized and tested for biological activity. The results of the structure-activity relationship (SAR) studies are reported here.

Friedel−Crafts Acylation and Metalation Strategies in the Synthesis of Calothrixins A and B

The total syntheses of calothrixins A and B starting from readily available indole and the acid chloride 4 are described.

Structural insights into the design of small molecule inhibitors that selectively antagonize Mcl-1

The screening of a small focused library of rhodanine derivatives as inhibitors of Bcl-2 proteins led to the discovery of two structurally related compounds with different binding profiles against the Bcl-XL and the Mcl-1 proteins. Subsequent NMR studies with mutant proteins and in silico docking studies provide a possible rationale for the observed specificity.

The efficacy and safety of daptomycin vs. vancomycin for the treatment of cellulitis and erysipelas

BACKGROUND

Results from previous trials suggest that daptomycin may result in faster clinical improvement than penicillinase-resistant penicillins or vancomycin for patients with complicated skin and skin structure infections.

OBJECTIVE

The objective was to evaluate whether daptomycin treatment of cellulitis or erysipelas would result in faster resolution compared with vancomycin.

DESIGN

The study was a prospective, evaluator-blinded, multi-centre trial. Patients were randomised to receive daptomycin 4 mg/kg once daily or vancomycin according to standard of care for 7-14 days.

PATIENTS

Adults diagnosed with cellulitis or erysipelas requiring hospitalisation and intravenous antibiotic therapy were eligible for enrolment.

RESULTS

The clinical success rates were 94.0% for daptomycin and 90.2% for vancomycin (95% confidence interval for the difference, -6.7%, 14.3%). There were no statistically significant differences between treatment arms in the time to resolution or improvement in any of the predefined clinical end-points. Both daptomycin and vancomycin were well tolerated.

CONCLUSIONS

There was no difference in the rate of resolution of cellulitis or erysipelas among patients treated with daptomycin or vancomycin. Daptomycin 4 mg/kg once daily appeared to be effective and safe for treating cellulitis or erysipelas.

Multiple spinal nerve enlargement and SOS1 mutation: Further evidence of overlap between neurofibromatosis type 1 and Noonan phenotype

Neurofibromatosis type 1 (NF1) has long been considered a well-defined, recognizable monogenic disorder, with neurofibromas constituting a pathognomonic sign. This dogma has been challenged by recent descriptions of patients with enlarged nerves or paraspinal tumors, suggesting that neurogenic tumors and hypertrophic neuropathy may be a complication of Noonan syndrome with multiple lentigines (NSML) or RASopathy phenotype. We describe a 15-year-old boy, whose mother previously received clinical diagnosis of NF1 due to presence of bilateral cervical and lumbar spinal lesions resembling plexiform neurofibromas and features suggestive of NS. NF1 molecular analysis was negative in the mother. The boy presented with Noonan features, multiple lentigines and pectus excavatum. Next-generation sequencing analysis of all RASopathy genes identified p.Ser548Arg missense mutation in SOS1 in the boy, confirmed in his mother. Brain and spinal magnetic resonance imaging scans were negative in the boy. No heart involvement or deafness was observed in proband or mother. This is the first report of a SOS1 mutation associated with hypertrophic neuropathy resembling plexiform neurofibromas, a rare complication in Noonan phenotypes with mutations in RASopathy genes. Our results highlight the overlap between RASopathies, suggesting that NF1 diagnostic criteria need rethinking. Genetic analysis of RASopathy genes should be considered when diagnosis is uncertain.

Evidence for gliotoxin-glutathione conjugate adducts

The equilibrium constant for the gliotoxin/glutathione pair was found to be 1200+/-100 M(-1) at pH 7.0 at 25 degrees C. Under conditions where the reaction was quenched rapidly with the addition of acid, gliotoxin-glutathione conjugate adducts were detected.

CLEVER: pipeline for designing in silico chemical libraries

Advances in virtual screening have created new channels for expediting the process of discovering novel drugs. Of particular relevance and interest are in silico techniques that enable the enumeration of combinatorial chemical libraries, generation of 3D coordinates and assessment of their propensity for drug-likeness. In a bid to provide an integrated pipeline that encompasses the common components functional for designing, managing and analyzing combinatorial chemical libraries, we describe a platform-independent, standalone Java application entitled CLEVER (Chemical Library Editing, Visualizing and Enumerating Resource). CLEVER supports chemical library creation and manipulation, combinatorial chemical library enumeration using user-specified chemical components, chemical format conversion and visualization, as well as chemical compounds analysis and filtration with respect to drug-likeness, lead-likeness and fragment-likeness based on the physicochemical properties computed from the derived molecules. Also provided is an integrated property-based graphing component that visually depicts the diversity, coverage and distribution of selected compound collections. When deployed in conjunction with large-scale virtual screening campaigns, CLEVER can offer insights into what chemical compounds to synthesize, and more importantly, what not to synthesize. The software is available at http://datam.i2r.a-star.edu.sg/clever/.

A Novel Itera-Like Densovirus Isolated by Viral Metagenomics from the Sea Barley Hordeum marinum

Densoviruses (DVs) infect arthropods and belong to the Parvoviridae family. Here, we report the complete coding sequence of a novel DV isolated from the plant Hordeum marinum (Poaceae) by viral metagenomics, and we confirmed reamplification by PCR. Phylogenetic analyses showed that this novel DV is related to the genus Iteradensovirus.

In silico design of small molecules

Computational methods now play an integral role in modern drug discovery, and include the design and management of small molecule libraries, initial hit identification through virtual screening, optimization of the affinity and selectivity of hits, and improving the physicochemical properties of the lead compounds. In this chapter, we survey the most important data sources for the discovery of new molecular entities, and discuss the key considerations and guidelines for virtual chemical library design.

In vitro dissolution and in vivo bioavailability of commercial levothyroxine sodium tablets in the hypothyroid dog model

The objective of this study was to determine whether a correlation exists between the rate of in vitro dissolution and bioavailability of levothyroxine sodium (T4) tablets. Dissolution versus time profiles for Synthroid, the Flint brand of levothyroxine sodium, and two competitors' tablets (brands A and B) were generated using an official dissolution apparatus (USP), and 0.05 M phosphate buffer (pH 7.4) as the medium. These tablets were also utilized in single-dose crossover bioavailability studies in the hypothyroid dog model (n = 6). The average areas under the serum T4 concentration versus time curve from 0 to 8 h (AUC) for Synthroid, brand A, and brand B were 8.22, 6.32, and 8.70 ng-h/mL per dose (micrograms per kg body weight), respectively. Respective peak serum concentrations (Cmax) for each tablet formulation were 1.26, 1.07, and 1.36 ng/mL per dose. The corresponding dissolution rates, expressed as t50%, were 20.5, 3.06, and 14.1 min, respectively. Data analysis indicated no correlation between dissolution kinetic parameters and the bioavailability parameters AUC and Cmax. However, a linear relationship was observed between dissolution kinetics and both the time to reach maximal serum concentration (tmax) and the observed absorption rate constant (ka).

Neuropsychiatric syndrome with myoclonus after SARS-CoV-2 infection in a paediatric patient

We report the case of a 12-years-old patient who subacutely developed a positive and negative myoclonus of limbs and face, drowsiness and memory deficits after getting infected by SARS-CoV-2. On admission, nasopharyngeal swab for SARS-CoV-2, brain and spinal MRI with and without contrast, EEG, chest X-ray and abdominal ultrasound were negative. CSF physical-chemical examination, culture, PCR testing for SARS-CoV-2 and other pathogens, and oligoclonal IgG bands were negative as well. A full panel blood test, including clotting, autoimmunity and paraneoplastic blood studies, did not show any alteration. The neuropsychological examination showed an impairment in memory, visual-motor coordination, inductive reasoning skills, attention, and concentration. The patient was first treated with clonazepam and then with intravenous methylprednisolone for five days, with poor response. For this reason, he then received a cycle of IVIG, thus reaching a gradual and complete recovery. To date, this is the first case of a COVID-19 associated myoclonus affecting a paediatric patient.

Investigation of the helicopter downwash effect on pedestrian comfort using CFD

This study employed computational fluid dynamics (CFD) to investigate the impact of helicopter downwash on pedestrian comfort in a representative low-rise streetscape. A time-averaged approach was adopted, where propulsion from the helicopter blades was included using the so-called rotor disc method, as implemented in the open-source software OpenFoam. The modelling approach was validated by comparing downstream air velocities with experimental measurements. The effect of helicopter downwash on pedestrian comfort in a low-rise built environment, representative of an Irish city streetscape, was then analysed. It was found that pedestrian comfort significantly decreased in the immediate vicinity of the helicopter, while minor propagating effects were felt further downstream. The effects of building height, street width and prevailing winds were then examined. In general, it was found that taller buildings tended to improve street-level pedestrian comfort, while narrow streets surrounded by tall buildings tended to funnel the downwash towards the street level, decreasing pedestrian comfort. The main conclusion is that although the effect of helicopter downwash is smaller in magnitude compared with that of prevailing winds, a local mitigation must be established to deal with it.

[Patterns of ventricular late potentials in systemic sclerosis: a noninvasive method in the study of cardiac involvement]

The aim of our study was to ascertain the prevalence of ventricular late potentials (VLP) in systemic sclerosis (SSc) and their correlation with the immunologic patterns and cutaneous and pulmonary involvement of the disease. Ventricular late potentials, which are low-amplitude high-frequency signals present in the terminal portion of the QRS complex, express the delayed and fragmented depolarization of ventricular myocardial fibers. Observed in myocardial interstitial fibrosis, they are characteristic of the myocardial alterations occurring in SSc. Twenty-six patients with SSc (1 man, 25 women) with a confirmed lack of cardiac involvement (negative history and normal clinical, electrocardiographic, and echocardiographic findings) underwent signal averaged high resolution electrocardiography. Pulmonary involvement was evaluated by pulmonary function tests and high resolution computed tomography. The degree of cutaneous involvement was assessed by skin score. In the patients with SSc, VLP presence with time-domain analysis was 30.8% when a 25-250 Hz pass-band filter was used and 26.9% when a 40-250 Hz pass-band filter was used whereas with frequency domain analysis it was 23.1%. Ventricular late potentials were confirmed in 7.7% of the control subjects, no matter what filter or technique was used. No significant correlations among VLP, pulmonary involvement, skin score and specific antibody patterns were found. Although this technique requires further consolidation, it seems to have the potential for use as an early index of myocardial fibrosis.

[Good response to azidothymidine in 3 patients with vacuolar myelopathy]

We report 3 drug abusers with human immunodeficiency virus (HIV) infection who had presented with myelopathic symptoms. A diagnosis of vacuolar myelopathy associated with HIV was made. The patients had a favorable response to azidothymidine. They were followed up as outpatients, and they showed a significant clinical improvement within 1-3 months of therapy. They remained stable 11 months afterwards. The patients with this type of disease may benefit from azidothymidine therapy.

Salt reduction strategies for dry cured meat products: The use of KCl and microencapsulated spices and aromatic plant extracts

The World Health Organization set a goal of reducing salt intake by 30 % by 2025. This study investigates the impact of replacing 33 % NaCl with KCl and microencapsulated spices and aromatic plant extracts (ME) in a dry-cured meat sausage (CMS). Microbial, physico-chemical, and sensory analyses were conducted throughout processing and storage. Three batches of CMS were prepared with four formulations: Control (1.5 % NaCl), F1 (1 % NaCl, 0.5 % KCl), F2 (1 % NaCl, 0.5 % ME, 0.3 % KCl), and F3 (1 % NaCl, 0.5 % ME). The absence of Listeria monocytogenes was confirmed. The formulations did not affect the growth of lactic acid bacteria (7.8 log cfu/g), Enterococci (6.5 log cfu/g), and coagulase-negative staphylococci (5.6 log cfu/g). Biogenic amines increased significantly (P < 0.05) during storage, with cadaverine (from 166 to 456 mg/kg), tyramine (163 to 424 mg/kg) and putrescine (from 31.0 to 90.5 mg/kg), being the most abundant. All low sodium CMS had lower TBARS values (F1 = 0.59 mg MDA/kg, F2 = 0.56 mg MDA/kg and F3 = 0.47 mg MDA/kg) compared to control (0.78 mg MDA/kg). Colour parameters lightness (L*) and yellowness (b*) remained stable (P > 0.05) while sausages with KCl and/or ME were redder. CMS F1 was considered with the ideal saltiness by 54 % consumers, that is usually considered enough to launch the product in the market. The use of ME in CMS has potential but still requires optimization. The study demonstrates that a 33 % NaCl replacement with KCl is feasible without jeopardize the organoleptic characteristics or safety of CMS.