Lipid environment determines the drug-stimulated ATPase activity of P-glycoprotein.

P-glycoprotein (Pgp) is a multidrug transporter that uses the energy from ATP binding and hydrolysis to export from cells a wide variety of hydrophobic compounds including anticancer drugs, and mediates the bioavailability and pharmacokinetics of many drugs. Lipids and cholesterol have been shown to modulate the substrate-stimulated ATPase activity of purified Pgp in detergent solution and the substrate transport activity after reconstitution into proteoliposomes. While lipid extracts from E. coli, liver or brain tissues generally support well Pgp's functionality, their ill-defined composition and high UV absorbance make them less suitable for optical biophysical assays. On the other hand, studies with defined synthetic lipids, usually the bilayer-forming phosphatidylcholine with or without cholesterol, are often plagued by low ATPase activity and low binding affinity of Pgp for drugs. Drawing from the lipid composition of mammalian plasma membranes, we here investigate how different head groups modulate the verapamil-stimulated ATPase activity of purified Pgp in detergent-lipid micelles and compare them with components of E. coli lipids. Our general approach was to assay modulation of verapamil-stimulation of ATPase activity by artificial lipid mixtures starting with the bilayer-forming palmitoyloyl-phosphatidylcholine (POPC) and -phosphatidylethanolamine (POPE). We show that POPC/POPE supplemented with sphingomyelin (SM), cardiolipin, or phosphatidic acid enhanced the verapamil-stimulated activity (Vmax) and decreased the concentration required for half-maximal activity (EC50). Cholesterol (Chol) and more so its soluble hemisuccinate derivative cholesteryl hemisuccinate substantially decreased EC50, perhaps by supporting the functional integrity of the drug binding sites. High concentrations of CHS (>15%) resulted in a significantly increased basal activity which could be due to binding of CHS to the drug binding site as transport substrate or as activator, maybe acting cooperatively with verapamil. Lastly, Pgp reconstituted into liposomes or nanodiscs displayed higher basal activity and sustained high levels of verapamil stimulated activity. The findings establish a stable source of artificial lipid mixtures containing either SM and cholesterol or CHS that restore Pgp functionality with activities and affinities similar to those in the natural plasma membrane environment and will pave the way for future functional and biophysical studies.

Heat-stable spores of carotenoid-producing Bacillus marisflavi and non-pigmented Bacillus subtilis cooperatively promote growth, quality, and gut microbiota of white-leg shrimp.

We evaluated the benefits of heat-stable carotenoid-producing Bacillus marisflavi SH8 spores individually and in combination with non-pigmented Bacillus subtilis SH23 spores on growth, colour change, nutritional content, innate immunity, and gut microbiota of white-leg shrimp. White-leg shrimp (Litopenaeus vannamei; n = 30 per tank; 2 tanks per group) were provided feed without (control group) or with SH8, SH23, or mixed spores (total, 1 × 106 cfu/g pellet) for 28 d. The SH8 and SH8-23 combination groups had significantly higher specific growth rates (9.6 and 11.0%), improved red-colour score (4 scores), astaxanthin concentration (1.8- and 2.3-fold), lipid contents (30 and 50%), and superoxidase dismutase activity (8.5 and 12.3%) than that of the control group. Analysis of shrimp's gut microbiome using 16S rRNA metagenome sequencing revealed increased abundance of four useful species and reduced abundance of four harmful species in the combination group than in the control group. Heat-stable Bacillus spore combination improved growth parameters, nutrient content, red-colour score, live counts, and abundance of useful bacteria in the gut of L. vannamei. This is the first study to show the benefits of combining highly heat-stable pigmented and non-pigmented Bacillus spores and their possible mechanisms in a shrimp model.

A Southeast Asian collaborative Delphi consensus on surveying risk factors for head and neck cancer screening and prevention.

The objective of this study was to determine high value questions for early detection and prevention of head and neck cancer by querying content experts on patient risk factors relevant to local communities in Southeast Asia (i.e., Vietnam, Laos, China, and Singapore). The Delphi method was employed using three rounds of asynchronous surveying which included participants among five different collaborating medical centers. 60 total survey items were assessed for consensus defined by a priori measures on the relative level of value of these questions for use in head and neck cancer screening. 77% of items reached a consensus and no items were concluded to be of low value despite differences in conclusions regarding relative importance. Survey items focused on patient demographic information and physical examination were examined across variables such as expert department affiliation, academic designation, and years of experience and found to be without statistically significant differences. However, with consensus items related to social risk factors, it was determined that participants who had 15 or more years of experience or identified as otolaryngologists rated these items at a relatively lower value than their peers with less experience (p < 0.0001, p = 0.0017) or outside the field of otolaryngology (p = 0.0101). This study explicitly identifies patient variables to consider in head and neck cancer screening that have not previously been comprehensively or methodically assessed in current literature. Increasing awareness of these risk factors may benefit the design and implementation of future head and neck cancer early detection and prevention programs in Southeast Asia and beyond as well as positively impact head and neck cancer outcomes.

Core build-up resin composites: an in-vitro comparative study.

AIM: Resin composite (RC) are commonly used under full crowns. However, independent information is lacking to guide practitioners regarding core RC material selection. This study aimed at comparing the flexural properties of a large selection of commercially-available core build-up RCs (CBU-RC), either light-, self- or dual-cure, to conventional light-cure RCs. METHODS: RCs were injected into a 25 × 2×2mm Teflon mold, and either light-cured during 20 s (materials with claimed light-cure characteristics) or covered by aluminum during 10 min (dual- and self-cure CBU-RCs). They were subjected after a one-week water storage at 37.5 °C to three-point bending, and Flexural modulus (E flex) and Flexural Strength (σ f) were calculated (n = 20). Thermogravimetric analysis (n = 3) was performed to determine inorganic filler content (%). RESULTS: For dual-cure CBU-RCs, both RC (p < .0001) and light-curing (p = .0007) had a significant influence on E flex, while only RC was significant for σ f (p < .0001). Between all conventional RCs and CBU-RCs, significant differences were observed (p < .0001), both regarding E flex and σ f, with values ranging from 3.9 to 15.5 GPa and from 76 to 130.3 MPa, respectively. Higher E flex values were observed for light-cure RCs than for self- and dual-cure ones, while no clear trend was noticed regarding σ f. Good linear correlation was found between inorganic filler content and E flex (R 2=0.85, p < .0001), but not with σ f (R 2=0.08, p = .1609). CONCLUSION: This work demonstrated a positive influence of light-curing on dual-cure CBU-RC's E flex. It also highlighted large differences in flexural properties (especially E flex) among the investigated materials, questioning the use of some CBU-RCs as dentin replacement in case of large tissue loss.

Geriatric dentistry on the Internet: can we reach our elderly patients using cyberspace?

A growing number of older Americans use a computer at home, and half of seniors who own computers also own modems that can connect them to online services; 25% of seniors with computers communicate with online services. Over 70% of online seniors use their computers every day. The dental office can interactively communicate one-on-one with current and prospective patients using an electronic mail newsletter, a Web page newsletter, an "Ask the Dentist" online service, or by making dental appointments online. Dental practitioners can take advantage of this online revolution and promote oral health for seniors using these technologies.

Absorption of epidermal growth factor occurs through the gastrointestinal tract and oral cavity in adult rats.

Introduction of radiolabeled epidermal growth factor (125I-EGF) by gavage or sublingual confinement resulted in a time-dependent uptake and systemic organ dissemination in the adult rat. Intact EGF was recovered primarily from the tongue, parotid, and sublingual/submandibular glands after administration by sublingual lozenge, whereas gastrointestinal administration resulted in 125I-EGF recovery primarily from plasma, stomach, and lung. Recovered radiolabeled EGF retained the ability to bind to the EGF receptor. Sialoadenectomy caused an increase in 125I-EGF in most tissues by both routes of administration. Thus, in the adult rat, at least two pathways exist for the uptake and distribution for salivary gland-derived EGF present in saliva. With further analyses, sublingual absorbance of EGF may therefore provide a potential delivery route for therapeutic use of growth factor, which avoids the hepatic destruction of EGF after oral administration.