Lifespan analysis of dystrophic mdx fast-twitch muscle morphology and its impact on contractile function

ABSTRACTDuchenne muscular dystrophy is caused by the absence of the protein dystrophin from skeletal muscle and is characterized by progressive cycles of necrosis/regeneration. Using the dystrophin deficient mdx mouse model we studied the morphological and contractile chronology of dystrophic skeletal muscle pathology in fast twitch EDL muscles from animals 4-22 months of age containing 100% regenerated muscle fibers. Catastrophically, the older age groups lost ∼80% of their maximum force after one eccentric contraction of 20% strain, with the greatest loss ∼93% recorded in senescent 22 month old mdx mice. In old age groups there was minimal force recovery ∼24% after 120 minutes, correlated with a dramatic increase in the number and complexity of branched fibers. This data supports our two-stage model where a “tipping point” is reached when branched fibers rupture irrevocably on eccentric contraction. These findings have important implications for pre-clinical drug studies and genetic rescue strategies.

Voluntary oral dosing for precise experimental compound delivery in adult rats

Preclinical drug studies routinely administer experimental compounds to animal models with the goal of minimizing potential adverse events from the procedure. In this study, we assessed the ability to train adult male Long Evans rats to accept daily voluntarily syringe feedings of l-3,4-dihydroxyphenylalanine (L-DOPA) compared to intraperitoneal (IP) injections. Rats were trained to become familiar with the syringe and then fed a training solution that did not contain the experimental compound. If the rat was compliant during the training phase, the dilution of training solution was continuously decreased and replaced with the experimental solution. Voluntary oral dosing compliance was recorded and quantified throughout the study. To assess drug activity within the drug-targeted tissues, the striatum and retina were collected and analyzed for L-DOPA, dopamine and 3,4-dihydroxyphenylacetic acid (DOPAC) levels by high performance liquid chromatography (HPLC). Drug delivery efficiency by oral dosing was directly compared to IP injection by collecting plasma and analyzing L-DOPA levels with HPLC. Adult male rats had high compliance for voluntary oral dosing. HPLC showed that oral administration of the compound at the same dose as IP injection yielded significantly lower plasma levels, and that higher oral L-DOPA doses yield higher plasma L-DOPA content. This study describes detailed methodology to train adult rats to syringe feed experimental compounds and provides important preclinical research on drug dosing and drug delivery to the striatum and retina.

A quick and low-intensity method for oral administration to large numbers of mice: A possible alternative to oral gavage

Oral administration of medication to experimental animals is a cause of significant stress. When coupled to animals who are already under strenuous circumstances due to the disease being modelled, there is a significant risk for increased morbidity and mortality, thus influencing the results. Faced with these constraints, a low-intensity method for oral administration was developed, based solely on the natural behaviour of the animals and minimal conditioning, in which precise doses of medication were administered in a locally available, standard wheat cookie fragment, providing both a palatable vehicle and an absorbent matrix for the medication. Fast administration to large numbers of animals was thus achieved, safeguarding the animals’ welfare and ensuring ease of handling. This method is a promising alternative to oral gavage in pre-clinical drug studies with laboratory mice.

Photocrosslinkable liver extracellular matrix hydrogels for the generation of 3D liver microenvironment models

Liver extracellular matrix (ECM)-based hydrogels have gained considerable interest as biomimetic 3D cell culture environments to investigate the mechanisms of liver pathology, metabolism, and toxicity. The preparation of current liver ECM hydrogels, however, is based on time-consuming thermal gelation and limits the control of mechanical properties. In this study, we used detergent-based protocols to produce decellularized porcine liver ECM, which in turn were solubilized and functionalized with methacrylic anhydride to generate photocrosslinkable methacrylated liver ECM (LivMA) hydrogels. Firstly, we explored the efficacy of two protocols to decellularize porcine liver tissue using varying combinations of commonly used chemical agents such as Triton X-100, Sodium Dodecyl Sulphate (SDS) and Ammonium hydroxide. Then, we demonstrated successful formation of stable, reproducible LivMA hydrogels from both the protocols by photocrosslinking. The LivMA hydrogels obtained from the two decellularization protocols showed distinct mechanical properties. The compressive modulus of the hydrogels was directly dependent on the hydrogel concentration, thereby demonstrating the tuneability of mechanical properties of these hydrogels. Immortalized Human Hepatocytes cells were encapsulated in the LivMA hydrogels and cytocompatibility of the hydrogels was demonstrated after one week of culture. In summary, the LivMA hydrogel system provides a simple, photocrosslinkable platform, which can potentially be used to simulate healthy versus damaged liver for liver disease research, drug studies and cancer metastasis modelling.

Using Dictyostelium to Develop Therapeutics for Acute Respiratory Distress Syndrome

Acute respiratory distress syndrome (ARDS) involves damage to lungs causing an influx of neutrophils from the blood into the lung airspaces, and the neutrophils causing further damage, which attracts more neutrophils in a vicious cycle. There are ∼190,000 cases of ARDS per year in the US, and because of the lack of therapeutics, the mortality rate is ∼40%. Repelling neutrophils out of the lung airspaces, or simply preventing neutrophil entry, is a potential therapeutic. In this minireview, we discuss how our lab noticed that a protein called AprA secreted by growing Dictyostelium cells functions as a repellent for Dictyostelium cells, causing cells to move away from a source of AprA. We then found that AprA has structural similarity to a human secreted protein called dipeptidyl peptidase IV (DPPIV), and that DPPIV is a repellent for human neutrophils. In animal models of ARDS, inhalation of DPPIV or DPPIV mimetics blocks neutrophil influx into the lungs. To move DPPIV or DPPIV mimetics into the clinic, we need to know how this repulsion works to understand possible drug interactions and side effects. Combining biochemistry and genetics in Dictyostelium to elucidate the AprA signal transduction pathway, followed by drug studies in human neutrophils to determine similarities and differences between neutrophil and Dictyostelium chemorepulsion, will hopefully lead to the safe use of DPPIV or DPPIV mimetics in the clinic.

Novel Nitro-Heteroaromatic Antimicrobial Agents for the Control and Eradication of Biofilm-Forming Bacteria

The synthesis and biological activity of several novel nitrothiazole, nitrobenzothiazole, and nitrofuran containing antimicrobial agents for the eradication of biofilm-forming Gram-negative and Gram-positive pathogens is described. Nitazoxanide (NTZ), nitrofurantoin, and furazolidone are commercial antimicrobials which were used as models to show how structural modification improved activity toward planktonic bacteria via minimum inhibitory concentration (MIC) assays and biofilms via minimum biofilm eradication concentration (MBEC) assays. Structure–activity relationship (SAR) studies illustrate the ways in which improvements have been made to the aforementioned antimicrobial agents. It is of particular interest in this regard that the introduction of a chloro substituent at the 5-position of NTZ (analog 1b) resulted in marked activity enhancement, as did the replacement of the 2-acetoxy substituent in the latter compound with a basic amine group (analog 7b). It is also of importance that analog 4a, which is a simple methacrylamide, displayed noteworthy activity against S. epidermidis biofilms. These lead compounds identified to have high activity towards biofilms provide promise as starting points in future pro-drug studies.

Effect of β-Cyclodextrin Stabilized Silver Nanoparticles on Gills, Kidney, Liver of Danio rerio

The silver nanoparticles (AgNP) are applied broadly in medical applications due to their antimicrobial property. However, the toxicity (uptake, translocation, and accumulation) of these AgNPs nanomaterial has not been much explored. Also, cyclodextrin has been used for different pharmaceutical applications due to its various potential properties. Therefore, the toxicity of these AgNPs and cyclodextrin in the model organism such as Danio rerio could be crucial for future nano-drug studies. The main aim of the present research work is to synthesize, characterize biopolymeric silver nanoparticles, and perform histopathological studies of synthesized silver nanoparticles on Danio rerio. The silver nanoparticles of 130nm size have been synthesized successfully using β-Cyclodextrin (β-CD) at room temperature. The various analytical applied to characterized the β-Cyclodextrin (β-CD) reduced silver nanoparticles (β-CD)-SNPs. A histopathological study has been conducted to evaluate the toxicity effect of the synthesized (β-CD)-SNP on the animal model Danio rerio. The (β-CD)-SNPs conc. 30µl/l is affecting and damaged gills and kidney the Danio rerio organs (gills, kidney) exposed after 10 days, yet the liver was found to be healthy. In conclusion, the Danio rerio gills, kidneys, and liver are sensitive to the 130nm-sized (β-CD)-SNPs. The nanoparticles' toxicity depends on concentration; less concentration (30µl/l) accumulates and is absorbed efficiently than the higher concentration (300µl/l). However, no morphological changes were observed on Danio rerio.

Digital chemsex publics: Algorithmic and user configurations of fear and desire on Pornhub

In recent years, chemsex has emerged as both a subcultural vernacular and an orientation device for gay health promotion. Chemsex loosely describes gay men using certain drugs to extend and modulate group sex practice. In line with hegemonic responses to gay sexuality in general, most research has been grounded in problematisation, with discourse mostly returning to the question of containment. Drawing on porn, platform and critical drug studies, this article offers a corrective approach by defining a networked, cultural study of chemsex that is attuned to how chemsex erotics operate in many different (digital) intimate publics. Assembling algorithmic search suggestions, 41 videos and 450 comments, the article finds that the videos and comments found through the search function are vastly different than those found through user-generated playlists. Two competing publics form around the fear/desire-response to drug use: a cautious erotic of disinhibition and a counterpublic erotic of transgression.