Memory reactivation during sleep does not act holistically on object memory.

Memory reactivation during sleep is thought to facilitate memory consolidation. Most sleep reactivation research has examined how reactivation of specific facts, objects, and associations benefits their overall retention. However, our memories are not unitary, and not all features of a memory persist in tandem over time. Instead, our memories are transformed, with some features strengthened and others weakened. Does sleep reactivation drive memory transformation? We leveraged the Targeted Memory Reactivation technique in an object category learning paradigm to examine this question. Participants (20 female, 14 male) learned three categories of novel objects, where each object had unique, distinguishing features as well as features shared with other members of its category. We used a real-time EEG protocol to cue the reactivation of these objects during sleep at moments optimized to generate reactivation events. We found that reactivation improved memory for distinguishing features while worsening memory for shared features, suggesting a differentiation process. The results indicate that sleep reactivation does not act holistically on object memories, instead supporting a transformation process where some features are enhanced over others.SIGNIFICANCE STATEMENT This study addresses a critical gap in our understanding of memory consolidation by demonstrating a role for reactivation during sleep in memory transformation. Most research on sleep reactivation has examined how reactivation of specific items benefits retention; the assumption has been that memories are reactivated in whole during sleep and that the entirety of the memory benefits. However, we know that our memories are not unitary elements that improve holistically over time. Instead, they undergo transformation, with some features strengthened and others weakened. We demonstrate that memory reactivation during sleep is causally contributing to this transformation. Our findings provide several novel insights into the dynamics of memory reactivation, advancing our understanding of how sleep shapes memory representations.

Standardization of urinary tract infection diagnosis in the neonatal ICU: Experience at a tertiary care center.

BACKGROUND: Urinary tract infections (UTIs) and antibiotic overexposure are common neonatal problems. Recently, evidence has emerged that a standardized approach to neonatal UTI can reduce unnecessary diagnosis without complications. This quality improvement project aimed to achieve those goals in our neonatal intensive care unit (NICU). METHODS: A UTI diagnosis guideline was adapted from the literature with the goal of maximizing the proportion of diagnosed UTIs that conform to accepted diagnostic criteria: >10,000 CFU/mL of one organism with pyuria, or >50,000 CFU/mL of one organism regardless of pyuria. The guideline was implemented in a level III NICU. Adherence, results, and complications were monitored for 12 months. RESULTS: Guideline adherence after implementation was favorable, as evidenced by increased adoption of urinalysis with microscopy. There was a non-significant increase in diagnostic adherence to criteria, 87% to 93%, and non-significant decrease in the rate of UTI diagnosis, 39% to 36%. Complications were not significantly changed. Most UTIs were due to gram-negative rods, especially E. coli; Enterococcus was a common contaminant. CONCLUSIONS: A guideline for diagnosing UTIs can safely increase uniformity. In contrast to previously published results, no significant changes were seen in the rate of UTI or the proportion of diagnoses conforming to the criteria for UTI. It is likely that guideline effects depend on the established practices of NICU providers. Additionally, a consistent pattern was seen in which organisms were more likely to be judged the source of true UTIs or contaminated cultures, meriting further study.

Memory reactivation during sleep does not act holistically on object memory.

Memory reactivation during sleep is thought to facilitate memory consolidation. Most sleep reactivation research has examined how reactivation of specific facts, objects, and associations benefits their overall retention. However, our memories are not unitary, and not all features of a memory persist in tandem over time. Instead, our memories are transformed, with some features strengthened and others weakened. Does sleep reactivation drive memory transformation? We leveraged the Targeted Memory Reactivation technique in an object category learning paradigm to examine this question. Participants (20 female, 14 male) learned three categories of novel objects, where each object had unique, distinguishing features as well as features shared with other members of its category. We used a real-time EEG protocol to cue the reactivation of these objects during sleep at moments optimized to generate reactivation events. We found that reactivation improved memory for distinguishing features while worsening memory for shared features, suggesting a differentiation process. The results indicate that sleep reactivation does not act holistically on object memories, instead supporting a transformation process where some features are enhanced over others.

Localization of the colchicine-binding site of tubulin.

We have previously shown that rat brain tubulin, a heterodimer consisting of an alpha and beta monomer, can be covalently labeled with [3H]colchicine by near UV irradiation. Most of the label appears in beta-tubulin. We show here that beta-tubulin can be separated and purified from SDS preparative gels and analyzed by proteolysis. Chymotrypsin yielded a labeled approximately 4-kDa band that contained two peptides. Tryptic digestion also yielded an approximately 4-kDa band containing two peptides. Sequence analysis revealed a peptide of residues 1-36 and 213-242 for chymotrypsin and a peptide of residues 1-46 and 214-241 for trypsin. To identify which peptide carried the label, limited hydrolysis of beta-tubulin was done with trypsin; this procedure yielded a labeled 16-kDa N-terminal peptide and a 35-kDa C-terminal peptide, as identified by antibodies. Isolation of these peptides and extensive digestion with trypsin yielded two labeled peptides corresponding to residues 1-46 from the 16-kDa N-terminal fragment and residues 214-241 from the 35-kDa C-terminal fragment. These results show that at least two regions in beta-tubulin are specifically involved in colchicine binding and that the span of the colchicine molecule, < or = 11 A, bridges these two regions in the native beta monomer.

A study of the photodynamic efficiencies of some eye lens constituents.

We have studied the photochemical quantum yields of singlet oxygen production (using the RNO bleaching method) and superoxide production (using the EPR-spin trapping method and the SOD-inhibitable ferricytochrome c reduction spectral assay) of kynurenine (Ky), N-formylkynurenine (NFK), 3-hydroxykynurenine (3HK), kynurenic acid (KUA), and the flavins, riboflavin (RF) and flavin mononucleotide (FMN). Such a study of the photodynamic efficiencies is important since these compounds appear endogenously in the eye. The singlet oxygen quantum yields of the flavins and KUA are high, while Ky and 3HK generate no detectable amounts of singlet oxygen. The superoxide quantum yields of the sensitizers are low compared to their singlet oxygen, and Ky and 3HK produce no detectable amounts of superoxide. The production of the superoxide radical is enhanced in the presence of electron donor molecules such as EDTA and NADH. These results suggest that the production of oxyradicals in the lens may be modulated by the presence of endogenous electron donor molecules such as the coenzymes NADH and NADPH, which are present in significant amounts in some lenses. They also suggest that Ky and 3HK, which are known to be present in aged lenses, might play a protective rather than a deleterious role in the eye.