This is an open access article under the terms of the Creat ive Commo ns Attri bution-NonCo mmercial License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes.

Background The globally devastating effects of COVID‐19 breach not only the realm of public health, but of psychosocial interaction and communication as well, particularly with the advent of mask‐wearing. Methods A review of the literature and understanding of facial anatomy and expressions as well as the effect of botulinum toxin on emotions and nonverbal communication. Results Today, the mask has become a semi‐permanent accessory to the face, blocking our ability to express and perceive each other’s facial expressions by dividing it into a visible top half and invisible bottom half. This significantly restricts our ability to accurately interpret emotions based on facial expressions and strengthens our perceptions of negative emotions produced by frowning. The addition of botulinum toxin (BTX)–induced facial muscle paralysis to target the muscles of the top (visible) half of the face, especially the corrugator and procerus muscles, may act as a therapeutic solution by its suppression of glabellar lines and our ability to frown. The treatment of the glabella complex not only has been shown to inhibit the negative emotions of the treated individual but also can reduce the negative emotions in those who come in contact with the treated individual. Conclusions Mask‐wearing in the wake of COVID‐19 brings new challenges to our ability to communicate and perceive emotion through full facial expression, our most effective and universally shared form of communication, and BTX may offer a positive solution to decrease negative emotions and promote well‐being for both the mask‐wearer and all who come in contact with that individual.

Background The literature on botulinum neurotoxin type A (BoNT‐A) is extensive, often contradictory, and confounded by a competitive market of products and research attempting to distinguish brand individuality. Methods A comprehensive review of literature on the principles of BoNT‐A in aesthetics as well as clinical examples. Results In 2017, the Eight Key Clinical Postulates were formulated as a guide for the aesthetic practitioner in understanding BoNT‐A pharmacodynamics and to compare different toxins. These are now updated to include (a) All type A toxins act identically; (b) The mathematical relationship between toxin and receptor is the basis of efficacy, and clinical efficacy is influenced by molecular potency and patient attributes including muscle mass, gender, age, and ethnicity; (c) Efficacy, onset, and duration are functions of “molecular potency” defined as the number of active 150 kDa molecules available for binding; (d) “Molecular potency” is difficult to objectively quantify for commercially available toxins; (e) Up to a point, increased molecular potency decreases time to onset and increases duration of effect, and the “Molecular Potency Quotient” is a construct for comparing molecular potency commercial cost; (f) The area of effect of a toxin injection is dependent upon molecular potency, diffusion (passive), and spread (active); (g) Differing reconstitution volumes; and (h) Increased number of injection sites can affect spread, onset, and duration of effect. Conclusions The principles of BoNT‐A use in aesthetics are complex yet understandable as outlined in the framework of the updated Eight Key Clinical Postulates and serves as a useful tool for providing the most effective treatment and interpreting research on present and future toxin formulations.

This is an open access article under the terms of the Creat ive Commo ns Attri bution-NonCo mmercial License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes.

A large proportion of the metabolites formed from benzo[a]pyrene (BP) in cell cultures from rodents, fish and humans result from conjugation of an oxidized metabolite of BP with sulfate, glucuronic acid or glutathione (GSH). To improve the analysis of these metabolites, a reversed-phase ion-pair h.p.l.c. system using a step gradient of methanol:tetrabutyl-ammonium bromide in ammonium formate buffer has been developed for the separation of these three classes of conjugates. This system separated 3-hydroxy-BP glucuronide and sulfate conjugates and resolved them from GSH conjugates of BP 4,5-oxide, 7,8-oxide and 7,8-diol-9,10-epoxide. Cultures of early passage Syrian hamster, Wistar rat and Sencar mouse embryo cells, a bluegill fry (BF-2) cell line and a human hepatoma cell line (HepG2) were exposed to [3H]BP for 24 h. Medium samples from each were extracted with chloroform: methanol:water, and the water-soluble metabolites were analyzed by ion-pair h.p.l.c. The largest peak of metabolites in the media from cell cultures from rodents and the bluegill fry cell line co-eluted with the glucuronic acid conjugate of 3-hydroxy-BP. These phenol-glucuronides represented 48-62% of the total water-soluble metabolites in the fish and rodent cell cultures. Treatment of this material with beta-glucuronidase released 3-hydroxy-BP and 9-hydroxy-BP in ratios from 3:4 to 13.3:1 in various cultures. Media from the bluegill fry cell line and the mouse embryo cell cultures also contained a peak of BP-diol glucuronides; treatment of these peaks with beta-glucuronidase released mainly BP-7,8-diol. In HepG2 cells, 40% of the water-soluble metabolites were identified as sulfate conjugates of 3-hydroxy-BP and 9-hydroxy-BP. No glucuronic acid conjugates of BP metabolites were detected in HepG2 cells. Only small amounts of the water-soluble metabolites from these cell cultures eluted in the same volumes as the synthetic GSH conjugate of BP-4,5-oxide, BP-7,8-oxide and BP-7,8-diol-9,10-oxide. These studies indicate that conjugation with glucuronic acid represents a major pathway of formation of water-soluble metabolites from BP in cells derived from a number of species and demonstrate the value of this ion-pair h.p.l.c. system for the analysis of conjugates formed from BP.