Developed in concert with the Learning Disabilities Association of America (LDA), this White Paper regarding specific learning disabilities identification and intervention represents the expert consensus of 58 accomplished scholars in education, psychology, medicine, and the law. Survey responses and empirical evidence suggest that five conclusions are warranted: 1) The SLD definition should be maintained and the statutory requirements in SLD identification procedures should be strengthened; 2) neither ability-achievement discrepancy analysis nor failure to respond to intervention alone is sufficient for SLD identification; 3) a “third method” approach that identifies a pattern of psychological processing strengths and weaknesses, and achievement deficits consistent with this pattern of processing weaknesses, makes the most empirical and clinical sense; 4) an empirically-validated RTI model could be used to prevent learning problems, but comprehensive evaluations should occur for SLD identification purposes, and children with SLD need individualized interventions based on specific learning needs, not merely more intense interventions; and 5) assessment of cognitive and neuropsychological processes should be used for both SLD identification and intervention purposes.
Lipoteichoic and wall teichoic acids (TA) are highly anionic cell envelope-associated polymers containing repeating polyglycerol/ribitol phosphate moieties. Substitution of TA with D-alanine is important for modulation of many cell envelope-dependent processes, such as activity of autolytic enzymes, binding of divalent cations, and susceptibility to innate host defenses. D-Alanylation of TA is diminished when bacteria are grown in medium containing increased NaCl concentrations, but the effects of increased salt concentration on expression of the dlt operon encoding proteins mediating D-alanylation of TA are unknown. We demonstrate that Staphylococcus aureus transcriptionally represses dlt expression in response to high concentrations of Na The cell envelope provides a protective barrier and regulates communication between the inside and outside of the cell. In nonencapsulated gram-positive bacteria, the cell envelope consists of the cytoplasmic membrane and cell wall peptidoglycan layers, to which proteins and teichoic acids (TA) are covalently linked. The covalently linked wall teichoic acid (WTA) and cell membrane-anchored lipoteichoic acid (LTA) contain repeating units of ribitol or glycerol-phosphate (29). Together, TA represent the most abundant polyanions of the gram-positive bacterial cell envelope (8). The charge properties of these polymers can be modified by substitution for the ribitol or glycerol-phosphate units by glycosyl substituents or D-alanine esters (29). As judged by comparison of wild-type and mutant strains, esterification of D-alanine to TA has pleiotropic effects, including effects on regulation of the activity of autolytic enzymes (33, 42), binding of cations (e.g., Na ϩ , Mg 2ϩ , and Ca 2ϩ ) to the cell envelope (16,26,35), resistance to many antimicrobial cationic peptides/proteins (23, 32), and virulence (4). D-Alanylation of TA also promotes coaggregation, biofilm formation, and adhesion of bacteria on artificial surfaces (3, 13). In addition, D-alanylation increases the proinflammatory activity of LTA (5).An operon, including dltABCD, is necessary for D-alanylation of both LTA and WTA in Staphylococcus aureus. DAlanyl carrier protein ligase (Dcl; dltA) activates D-alanine using ATP. With assistance of DltD (dltD), this activated complex is delivered to the D-alanine carrier protein (Dcp) encoded by dltC. DltB (dltB) is predicted to be a transmembrane protein and is thought to be involved in passage of the Dalanyl-Dcp complex across the cytoplasmic membrane, where D-alanine is transferred to the glycerol phosphate backbone of LTA (29). D-Alanine esterified to LTA is the precursor for D-alanylation of WTA (15).Relatively little is known about the regulation of D-alanylation of TA in S. aureus. It is known that the degree of Dalanylation of TA varies depending on several different environmental factors such as pH, temperature, and salt (e.g., NaCl) concentration (16,19,28). An increase in pH, temperature, or NaCl concentration lowers the degree of D-alanylation of TA. For example, the...
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.