A method to determine reactive oxygen species production in intestinal and liver cell cultures using the 2',7'-dichlorodihydrofluorescein diacetate assay

Exposure to xenobiotics can increase the production of reactive oxygen species (ROS). When detoxification organs such as the intestines and liver cannot neutralise these xenobiotics, it can induce oxidative stress and cause damage to tissues. Therefore, cell-based bioassays that indicate intracellular ROS production are a useful screening tool to evaluate the effect of these chemicals. Although flow cytometry is commonly used to measure ROS in cells, many research laboratories in the Global South do not always have access to such specialised instrumentation. Therefore, we describe a sensitive but low-cost method that can easily be used to determine ROS production in vitro. This method employs the fluorogenic dye, 2',7'-dichlorodihydrofluorescein diacetate (H2DCF-DA), which emits fluorescence after being oxidised to a fluorescent derivative. Since the H2DCF-DA bioassay indicates non-specific ROS production it can be used as a marker of overall oxidative stress. This method was validated by exposing human duodenum epithelial adenocarcinoma (HuTu-80) and rat liver epithelial hepatoma (H4IIE-luc) cells to agricultural soil samples.•Production of ROS can be determined in vitro in intestinal and liver cells.•This method is inexpensive and can be easily performed in standard laboratories.•The method provides a tool for the high-throughput screening of environmental samples.

Determining superoxide dismutase content and catalase activity in mammalian cell lines

Traditional methods for determining superoxide dismutase (SOD) content and catalase (CAT) activity rely on measuring the absorbance of individual tissue (biological) samples using a cuvette and spectrophotometer, rather than cell cultures. Although there are kits available for SOD and CAT assays, these allow for high-throughput analysis of samples and might be too expensive for research laboratories in countries from the Global South, such as South Africa. This paper describes a simple and cost-effective method to determine SOD content and CAT activity in mammalian cell cultures following exposure to environmental chemical mixtures by measuring absorbance in 96-well microplates. Moreover, the equipment used for this method is considered standard for cell culture laboratories, while the reagents and consumables are easily obtainable.•Antioxidant enzyme levels can be measured in vitro in cell cultures.•The supernatant obtained can be used to determine protein concentration, SOD content, and CAT activity.•This method is simple and affordable, allowing for the analysis of multiple samples (up to 32 samples per microplate).

A method to determine the combined effects of climate change (temperature and humidity) and eggshell thickness on water loss from bird eggs

Differences in bird eggshell thicknesses occur due to numerous factors, including thinning due to persistent organic pollutants. Not only does thinning weaken the shell; weaker shells combined with elevated ambient temperature and changes in humidities may result in changes in water loss rates from the egg contents. Therefore, thinner eggshells raise concern of water being lost faster than normal at lower relative humidities, which may affect hatching. To investigate the combined effects, we developed and tested an effective method that measures water loss through different thickness eggshells at controlled temperatures and relative humidities to assist in ascertaining the combined effects of climate change (temperature and humidity) and changes in eggshell thickness on bird reproduction. The fastest rate of loss was at 40% RH at 40 °C (0.1 mL/cm²/day), and the slowest was at 22 °C at 80% RH (0.02 mL/cm²/day). Eggshell thickness had a significant effect on water loss at all humidity treatments, except at the highest temperature and humidity treatment (80% RH and 40 °C). Temperature explained 40% of the variance, RH explained 20%, and interactions between temperature and humidity explained 15% of the variance (repeated-measures, two-way ANOVA). Generalized linear analyses revealed that both factors temperature and humidity contributed significantly in any two-way combinations. We have laid the ground for a system to test the combined effects of temperature and humidity changes associated with climate change and eggshell thinning associated with pollutants, on water loss across eggshells.

A new forest dwelling button spider from South Africa (Araneae, Theridiidae, Latrodectus)

The medically important spider genus Latrodectus Walckenaer 1805, commonly referred to as "button spiders" in South Africa, is represented by six species in the country. Using morphology and the COI barcoding gene we describe a new forest dwelling species, Latrodectus umbukwane n. sp. Wright, Wright, Lyle and Engelbrecht. Females have red markings on both the ventral and posterior dorsal surfaces of the abdomen, parallel spermathecae and three loops of the copulatory ducts. Males have an embolus with four loops and diagnostic white markings on the ventral surface of the abdomen that darken with age. Egg sacs are smooth, large, and bright purple when freshly laid, turning shiny grey with time. Latrodectus umbukwane n. sp. is known only from sand forest vegetation types in northern Zululand, KwaZulu-Natal, South Africa. A predicted geographic distribution for this species is provided based on cartographic mapping of known habitat and altitudinal preference, from which area of occupancy (AOO; 698 km2) and extent of occurrence (EOO; 4963 km2) were calculated to assess potential IUCN Red List status. Due to the uncertainty of the distribution of this species, a Red List status of Data Deficient (DD) is recommended. An updated key to the southern African species of Latrodectus is provided.

A multinational, randomised, 12-week, comparative study of donepezil and rivastigmine in patients with mild to moderate Alzheimer's disease

This 12-week, multinational study compared the tolerability and cognitive effects of donepezil (up to 10 mg once daily) and rivastigmine (up to 6 mg twice daily) in 111 patients with mild to moderate Alzheimer's disease. Both medications were administered open label according to recommended dosing regimens from the respective product labelling available during the conduct of the study. More patients in the donepezil group (89.3%) completed the study compared with the rivastigmine group (69.1%; p=0.009), and 10.7% of the donepezil group and 21.8% of the rivastigmine group discontinued due to adverse events (AEs); 87.5% of donepezil-treated patients and 47.3% of rivastigmine-treated patients remained on the maximum approved dose of each drug at the last study visit. Both groups showed comparable improvements on the ADAS-cog administered by raters blind to study medication at weeks 4 and 12. Thus, using the recommended dosing schedules, donepezil was better tolerated with fewer discontinuations due to AEs, and both agents improved cognition to a similar extent.

Antibodies to high molecular weight polypeptides of desmosomes: specific localization of a class of junctional proteins in cells and tissue

Desmosome-enriched fractions were isolated from bovine muzzle epidermis either as desmosome-tonofilament complexes using a procedure involving treatment at pH9 or in the form of desmosomal residue fractions using a modification of the citric acid buffer (pH 2.3) method of Skerrow and Matoltsy [1]. Major polypeptides of high molecular weights (mol. wt.) were separated by gel electrophoresis, individual polypeptide bands were excised, and protein was eluted and used for immunization. Guinea pig antibodies raised against two prominent polypeptides of high mol. wt. (250,000 and 215,000) showed, on nitrocellulose paper blots of desmosome-tonofilament polypeptides separated by gel electrophoresis, extensive cross-reaction between a group or large polypeptides characteristic of desmosome-containing fractions, most notably polypeptides of 250 K, 215 K, 200 k, 175 K, and 164 K. These antibodies allowed, when used in immunofluorescence microscopy, the specific localization of desmosomal junctions (i) in sections through epithelia-containing tissue (e.g., epidermis, mucosae of tongue and esophagus, cornea, mammary gland, small intestine, liver, thymus, urothelium of bladder) and myocardium; (ii) on dissociated cells from these tissues; (iii) on various epithelial cells grown in culture; an (iv) in tumor-like proliferations of cultured epithelial cells injected into nude mice. Individual desmosomes could be visualized and resolved at the light microscopic level. No reaction was found in cells devoid of desmosomes and on other classes of intercellular junctions. Electron microscopic localization using immunoperoxidase techniques indicated that these proteins are located in, or close to, the desmosomal plague structure. It is proposed to use such antibodies against desmosomal proteins as markers specific to this so far only morphologically define class of junctions. Use of these markers will (i) improve identification and classification of intercellular junctions; (ii) facilitate determinations of the specific patterns of distributions of desmosomes and desmosomal protein in various cells and tissue; (iii) allow studies of formation and disintegration of desmosomes, and of the biosynthesis and possible recycling of their constituents; and (iv) provide tissue group-specific markers valuable in histology and diagnosis, especially for identification of epithelial and carcinoma cells.