Poly(amidoamine) dendrimers as ophthalmic vehicles for ocular delivery of pilocarpine nitrate and tropicamide.

The purpose of this study was to determine the influence of a controlled incremental increase in size, molecular weight and number of amine, carboxylate and hydroxyl surface groups in several series of poly(amidoamine) (PAMAM) dendrimers for controlled ocular drug delivery. The duration of residence time was evaluated after solubilization of several series of PAMAM dendrimers (generations 1.5 and 2-3.5 and 4) in buffered phosphate solutions containing 2 per thousand (w/v) of fluorescein. The New Zealand albino rabbit was used as an in vivo model for qualitative and quantitative assessment of ocular tolerance and retention time after a single application of 25 microl of dendrimer solution to the eye. The same model was also used to determine the prolonged miotic or mydriatic activities of dendrimer solutions, some containing pilocarpine nitrate and some tropicamide, respectively. Residence time was longer for the solutions containing dendrimers with carboxylic and hydroxyl surface groups. No prolongation of remanence time was observed when dendrimer concentration (0.25-2%) increased. The remanence time of PAMAM dendrimer solutions on the cornea showed size and molecular weight dependency. This study allowed novel macromolecular carriers to be designed with prolonged drug residence time for the ophthalmic route.     

Lateral hypothalamic sites in cats for stimulation of gastric antral contractions

Electrical stimulation through a bipolar electrode introduced into either the left or right lateral hypothalamus of anesthetized cats by means of a stereotaxic instrument elicited stimulus-bound phasic antral contractions in the anesthetized cat's stomach of much greater force than recorded under basal conditions. There was no change in gastric acid output. The response was abolished by bilateral cervical vagotomy or atropine. Stimulation during an intravenous infusion of pentagastrin did not alter the gastric acid secretory response. A hypothalamic vagal and cholinergic excitatory gastric antral motor pathway to the stomach has been demonstrated, independent of an acid secretory response.     

Omicron mutations enhance infectivity and reduce antibody neutralization of SARS-CoV-2 virus-like particles

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Omicron variant contains extensive sequence changes relative to the earlier-arising B.1, B.1.1, and Delta SARS-CoV-2 variants that have unknown effects on viral infectivity and response to existing vaccines. Using SARS-CoV-2 virus-like particles (VLPs), we examined mutations in all four structural proteins and found that Omicron and Delta showed 4.6-fold higher luciferase delivery overall relative to the ancestral B.1 lineage, a property conferred mostly by enhancements in the S and N proteins, while mutations in M and E were mostly detrimental to assembly. Thirty-eight antisera samples from individuals vaccinated with Pfizer/BioNTech, Moderna, or Johnson & Johnson vaccines and convalescent sera from unvaccinated COVID-19 survivors had 15-fold lower efficacy to prevent cell transduction by VLPs containing the Omicron mutations relative to the ancestral B.1 spike protein. A third dose of Pfizer vaccine elicited substantially higher neutralization titers against Omicron, resulting in detectable neutralizing antibodies in eight out of eight subjects compared to one out of eight preboosting. Furthermore, the monoclonal antibody therapeutics casirivimab and imdevimab had robust neutralization activity against B.1 and Delta VLPs but no detectable neutralization of Omicron VLPs, while newly authorized bebtelovimab maintained robust neutralization across variants. Our results suggest that Omicron has similar assembly efficiency and cell entry compared to Delta and that its rapid spread is due mostly to reduced neutralization in sera from previously vaccinated subjects. In addition, most currently available monoclonal antibodies will not be useful in treating Omicron-infected patients with the exception of bebtelovimab.

Understanding the molecular determinants of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) viral fitness is central to effective vaccine and therapeutic development. The emergence of viral variants including Delta and Omicron underscores the need to assess both infectivity and antibody neutralization, but biosafety level 3 handling requirements slow the pace of research on intact SARS-CoV-2. Although vesicular stomatitis virus and lentivirus pseudotyped with the SARS-CoV-2 spike (S) protein enable evaluation of S-mediated cell binding and entry via the ACE2 and TMPRSS2 receptors, they cannot determine effects of mutations outside the S gene (1, 2). To address these challenges, we developed SARS-CoV-2 virus-like particles (SC2-VLPs) comprising the S, N, M, and E structural proteins and a packaging signal-containing messenger RNA (mRNA) that together form RNA-loaded capsids capable of spike-dependent cell transduction (3). This system faithfully reflects the impact of mutations in structural proteins that are observed in infections with virus isolates, enabling rapid testing of SARS-CoV-2 structural gene variants for their impact on both infection efficiency and antibody or antiserum neutralization.     

Pediatric stroke: the child is not merely a small adult

Arterial ischemic stroke and sinovenous thrombosis are a significant yet under-recognized causes of mortality and morbidity in the pediatric population. With increasingly complex etiologies yet urgency for rapid diagnosis and treatment, pediatric stroke teams likely will become the standard of care. A common terminology must be developed to avoid confusing types of acute cerebral insults--such as focal arterial ischemic stroke and global hypoxia and ischemia--that have different causes and pathophysiologic mechanisms of injury. Increased awareness of unique pediatric stroke subtypes, their clinical presentation, and their imaging findings will facilitate early identification and development of optimal treatment strategies.