Corrigendum: Building a realistic, scalable memory model with independent engrams using a homeostatic mechanism.

[This corrects the article DOI: 10.3389/fninf.2024.

Building a realistic, scalable memory model with independent engrams using a homeostatic mechanism.

Memory formation is usually associated with Hebbian learning and synaptic plasticity, which changes the synaptic strengths but omits structural changes. A recent study suggests that structural plasticity can also lead to silent memory engrams, reproducing a conditioned learning paradigm with neuron ensembles. However, this study is limited by its way of synapse formation, enabling the formation of only one memory engram.

Characterization of the cystargolide biosynthetic gene cluster and functional analysis of the methyltransferase CysG.

Cystargolides are natural products originally isolated from Kitasatospora cystarginea NRRL B16505 as inhibitors of the proteasome. They are composed of a dipeptide backbone linked to a β-lactone warhead. Recently, we identified the cystargolide biosynthetic gene cluster, but systematic genetic analyses had not been carried out because of the lack of a heterologous expression system.

Structure of Staphylococcus aureus ClpP Bound to the Covalent Active-Site Inhibitor Cystargolide A.

The caseinolytic protease is a highly conserved serine protease, crucial to prokaryotic and eukaryotic protein homeostasis, and a promising antibacterial and anticancer drug target. Herein, we describe the potent cystargolides as the first natural β-lactone inhibitors of the proteolytic core ClpP. Based on the discovery of two clpP genes next to the cystargolide biosynthetic gene cluster in Kitasatospora cystarginea, we explored ClpP as a potential cystargolide target.

Discovery of a Cryptic Nitro Intermediate in the Biosynthesis of the 3-(-2'-Aminocyclopropyl)alanine Moiety of Belactosin A.

Belactosin A, a β-lactone proteasome inhibitor, contains a unique 3-(-2'-aminocyclopropyl)alanine moiety. We recently identified the biosynthetic gene cluster of the belactosin series from sp. UCK14.

Serendipitous Discovery of a Novel Murine Astrovirus Contaminating a Murine Helper T-cell Line and Incapable of Infecting Highly Immunodeficient Mice.

The unexpected seroconversion of sentinel mice in our facility to murine T lymphotrophic virus (MTLV) positivity led to our identification of a novel murine astrovirus that we designated murine astrovirus 2 (MuAstV-2). During our investigation, MuAstV-2 was found to be a contaminant of the T helper cell line (D10. G4.

Phosphorylation-Dependent Differences in CXCR4-LASP1-AKT1 Interaction between Breast Cancer and Chronic Myeloid Leukemia.

The serine/threonine protein kinase AKT1 is a downstream target of the chemokine receptor 4 (CXCR4), and both proteins play a central role in the modulation of diverse cellular processes, including proliferation and cell survival. While in chronic myeloid leukemia (CML) the CXCR4 is downregulated, thereby promoting the mobilization of progenitor cells into blood, the receptor is highly expressed in breast cancer cells, favoring the migratory capacity of these cells. Recently, the LIM and SH3 domain protein 1 (LASP1) has been described as a novel CXCR4 binding partner and as a promoter of the PI3K/AKT pathway.

Biosynthetic reconstitution of deoxysugar phosphoramidate metalloprotease inhibitors using an N-P-bond-forming kinase.

Phosphoramidon is a potent metalloprotease inhibitor and a widespread tool in cell biology research. It contains a dipeptide backbone that is uniquely linked to a 6-deoxysugar a phosphoramidate bridge. Herein, we report the identification of a gene cluster for the formation of phosphoramidon and its detailed characterization.

Characterization of the Actinonin Biosynthetic Gene Cluster.

The hydroxamate moiety of the natural product actinonin mediates inhibition of metalloproteinases because of its chelating properties towards divalent cations in the active site of those enzymes. Owing to its antimicrobial activity, actinonin has served as a lead compound for the development of new antibiotic drug candidates. Recently, we identified a putative gene cluster for the biosynthesis of actinonin.

Warhead biosynthesis and the origin of structural diversity in hydroxamate metalloproteinase inhibitors.

Metalloproteinase inhibitors often feature hydroxamate moieties to facilitate the chelation of metal ions in the catalytic center of target enzymes. Actinonin and matlystatins are  potent metalloproteinase inhibitors that comprise rare N-hydroxy-2-pentyl-succinamic acid warheads. Here we report the identification and characterization of their biosynthetic pathways.

Biosynthesis of the β-Lactone Proteasome Inhibitors Belactosin and Cystargolide.

Belactosins and cystargolides are natural product proteasome inhibitors from Actinobacteria. Both feature dipeptidic backbones and a unique β-lactone building block. Herein, we present a detailed investigation of their biosynthesis.

Synthesis of Phenylpropanoids via Matsuda-Heck Coupling of Arene Diazonium Salts.

The Pd-catalyzed Heck-type coupling (Matsuda-Heck reaction) of electron rich arene diazonium salts with electron deficient olefins has been exploited for the synthesis of phenylpropanoid natural products. Examples described herein are the naturally occurring benzofurans methyl wutaifuranate, wutaifuranol, wutaifuranal, their 7-methoxy derivatives, and the O-prenylated natural products boropinols A and C.

Systematic Investigation into the Matsuda-Heck Reaction of α-Methylene Lactones: How Conformational Constraints Direct the β-H-Elimination Step.

α-Methylene-γ-butyrolactone and α-methylene-δ-valerolactone undergo Pd-catalyzed Matsuda-Heck couplings with arene diazonium salts to α-benzyl butenolides or pentenolides, respectively, or to α-benzylidene lactones. The observed regioselectivity is strongly ring size dependent, with six-membered rings giving exclusively α-benzyl pentenolides, whereas the five-membered α-methylene lactone reacts to mixtures of regioisomers with a high proportion of (E)-α-benzylidene-γ-butyrolactones. DFT calculations suggest that the reasons for these differences are not thermodynamic but kinetic in nature.

Stability of Doxycycline in Feed and Water and Minimal Effective Doses in Tetracycline-Inducible Systems.

Despite the extensive use of doxycycline in tetracycline-inducible rodent models, little is known regarding its stability in feed or water or the most effective route or dose. We assessed the concentrations of doxycycline in reverse-osmosis-purified (RO; pH 6.0) and acidified RO (pH 2.

Overproduction of Ristomycin A by activation of a silent gene cluster in Amycolatopsis japonicum MG417-CF17.

The emergence of antibiotic-resistant pathogenic bacteria within the last decades is one reason for the urgent need for new antibacterial agents. A strategy to discover new anti-infective compounds is the evaluation of the genetic capacity of secondary metabolite producers and the activation of cryptic gene clusters (genome mining). One genus known for its potential to synthesize medically important products is Amycolatopsis.

Corynebacterium bovis: epizootiologic features and environmental contamination in an enzootically infected rodent room.

Corynebacterium bovis is a common pathogen in athymic nude mouse colonies. Control and eradication of the organism are challenging because depopulation and restricted colony access are often not options within vivaria. We evaluated potential sources and dissemination routes of C.

Strategies to prevent, treat, and provoke Corynebacterium-associated hyperkeratosis in athymic nude mice.

Athymic nude mice infected with Corynebacterium bovis typically exhibit transient hyperkeratotic dermatitis. Our vivarium experienced an increased incidence of disease characterized by persistent skin lesions and increased mortality, leading to this study. For detection of infection, skin and buccal swab methods showed comparable sensitivities in nude mice.

Treatment and eradication of murine fur mites: III. Treatment of a large mouse colony with ivermectin-compounded feed.

We determined the efficacy of ivermectin-compounded feed against fur mites in mice and describe its use to eradicate mites in vivaria holding approximately 30,000 cages. C57BL/6NCrl mice infested with Myobia musculi and Myocoptes musculinus were treated with ivermectin-compounded feed (approximate ingested dose, 1.3 mg/kg) for 1, 4, or 8 consecutive weeks.

Treatment and eradication of murine fur mites: II. Diagnostic considerations.

Fur mites are a persistent problem in contemporary laboratory mouse colonies. We conducted several studies to evaluate fur mite diagnostic methodologies and interpretation of results. Retrospective analysis of test results from sentinel mice exposed to soiled bedding collected from colonies infested with Myobia musculi and Myocoptes musculinus revealed the skin scrape test to be more reliable than pelt examination, provided that both the head and dorsal thoracolumbar regions were sampled.

Treatment and eradication of murine fur mites: I. Toxicologic evaluation of ivermectin-compounded feed.

Fur mite outbreaks remain a persistent problem in laboratory mouse colonies. All currently published treatment methods are labor-intensive, expensive, or unreliable. During a recent outbreak with Myobia musculi and Myocoptes musculinus in a large colony (approximately 30,000 cages), we developed a feed-based treatment regime in which ivermectin was the active ingredient.

Euthanasia by CO₂ inhalation affects potassium levels in mice.

We and others frequently have noted serum potassium levels of 8.0 +/- 0.85 mEq/L or greater in laboratory mice; this concentration has even been published as the upper limit of a 'normal' reference range.

Seroprevalence of West Nile virus in nonhuman primates as related to mosquito abundance at two national primate research centers.

West Nile virus (WNV) surfaced as an emerging infectious disease in the northeastern United States in 1999, gradually spread across the continent, and is now endemic throughout North America. Outdoor-housed nonhuman primates at the Tulane National Primate Research Center (TNPRC) in Louisiana were documented with a relatively high prevalence (36%) of antibodies to West Nile virus. We examined the prevalence of antibodies to WNV in a nonhuman primate population housed in outdoor colonies at the Yerkes National Primate Research Center Field Station located near Atlanta, Georgia.

Animalfree screening of biological materials for contamination by rodent viruses.

Pathogenic bacteria and viruses may be transmitted to laboratory rodents by contaminated biological materials potentially causing disease and confounding research results. Biological materials have historically being screened by using the mouse antibody production (MAP) test. We developed an alternative assay using polymerase chain reaction (PCR/real-time-PCR) technology to detect viral contamination directly in biological material.