End-of-life cell cycle arrest contributes to stochasticity of yeast replicative aging.

There is growing evidence that stochastic events play an important role in determining individual longevity. Studies in model organisms have demonstrated that genetically identical populations maintained under apparently equivalent environmental conditions display individual variation in life span that can be modeled by the Gompertz-Makeham law of mortality. Here, we report that within genetically identical haploid and diploid wild-type populations, shorter-lived cells tend to arrest in a budded state, while cells that arrest in an unbudded state are significantly longer-lived. This relationship is particularly notable in diploid BY4743 cells, where mother cells that arrest in a budded state have a shorter mean life span (25.6 vs. 35.6) and larger coefficient of variance with respect to individual life span (0.42 vs. 0.32) than cells that arrest in an unbudded state. Mutations that cause genomic instability tend to shorten life span and increase the proportion of the population that arrest in a budded state. These observations suggest that randomly occurring damage may contribute to stochasticity during replicative aging by causing a subset of the population to terminally arrest prematurely in the S or G2 phase of the cell cycle.

Changing Characteristics of Children With COVID-19 in Colorado Admitted During Different Variant Periods.

BACKGROUND: Data are lacking on the impact of different severe acute respiratory syndrome coronavirus 2 variants in children and on pediatric vaccine effectiveness. We examined differences among children requiring hospital admission associated with coronavirus disease 2019 (COVID-19) during wild type, Delta and Omicron variant periods and calculated vaccine effectiveness at preventing symptomatic hospitalization during the Delta and Omicron variant periods. METHODS: We conducted a retrospective review of children younger than 21 years of age hospitalized with symptomatic COVID-19. Characteristics were compared between variant periods using Kruskal-Wallis or generalized Fisher exact tests. We estimated vaccine effectiveness in preventing symptomatic hospitalization. RESULTS: We included 115 children admitted during the wild type period, 194 during Delta and 226 during the Omicron periods. Median age (years) decreased (12.2 wild type, 5.9 Delta, 1.3 Omicron periods, P < 0.0001) over time. Children were less likely to have a comorbid condition, including diabetes or obesity, and had shorter admissions during Omicron compared with the wild type and Delta periods. Intensive care unit admissions and respiratory support requirements were highest during the Delta period ( P = 0.05). Among children ≥12 years, adjusted vaccine effectiveness at preventing symptomatic hospitalization was 86% during Delta and 45% during Omicron periods. CONCLUSIONS: Children hospitalized with COVID-19 during later variant periods were younger and less likely to have comorbidities. Children admitted during the Delta variant period required more intensive care and respiratory support compared to other variant periods. Vaccination was less effective at preventing symptomatic hospital admission during the Omicron period compared to the Delta period.

An international survey on advanced practice nursing education, practice, and regulation.

PURPOSE: To describe international trends on the developing role of the nurse practitioner-advanced practice nurse (NP-APN), including nomenclature, levels and types of NP-APN education, practice settings, scope of practice, regulatory policies, and political environment. DESIGN: A cross-sectional, descriptive Web-based survey sent in February and March 2008 to a total of 174 key informants and active members of the International Nurse Practitioner-Advanced Practice Nursing Network of the International Council of Nurses. METHODS: An international Web-based survey preceded by a pilot survey. FINDINGS: Ninety-one nurses from 32 countries responded. Thirteen titles were identified on nomenclature for the NP-APN in different countries. NP-APN education was available in 71% of the 31 countries responding to this item, with 50% identifying the master's degree as the most prevalent credential. Twenty-three countries had formal recognition of the NP-APN role. Of these, 48% had licensure maintenance or renewal requirements for the NP-APN, with most requiring continuing education or clinical practice. The greatest support for the NP-APN role came from domestic nursing organizations (92%), individual nurses (70%), and the government (68%), while opposition came primarily from domestic physician organizations (83%) and individual physicians (67%). CONCLUSIONS: Interest in the NP-APN role has been gaining ground worldwide. This study presents a snapshot of education, practice, and regulation for NP-APNs as they develop their unique role in delivering health care in various countries. Areas that may require more support are highlighted. CLINICAL RELEVANCE: The NP-APN role in healthcare systems is expanding and will benefit from international networking and support.

Use of Antibiotics Reserved for Resistant Gram-Negative Infections at Freestanding U.S. Children's Hospitals from 2004 to 2014.

We used the Pediatric Health Information System database to assess the use of antibiotics reserved for the treatment of resistant Gram-negative infections in children from 2004 to 2014. Overall, use of these agents increased in children from 2004 to 2007 and subsequently decreased. Infect Control Hosp Epidemiol 2016:37:967-970.

A Comprehensive Analysis of Replicative Lifespan in 4,698 Single-Gene Deletion Strains Uncovers Conserved Mechanisms of Aging.

Many genes that affect replicative lifespan (RLS) in the budding yeast Saccharomyces cerevisiae also affect aging in other organisms such as C. elegans and M. musculus. We performed a systematic analysis of yeast RLS in a set of 4,698 viable single-gene deletion strains. Multiple functional gene clusters were identified, and full genome-to-genome comparison demonstrated a significant conservation in longevity pathways between yeast and C. elegans. Among the mechanisms of aging identified, deletion of tRNA exporter LOS1 robustly extended lifespan. Dietary restriction (DR) and inhibition of mechanistic Target of Rapamycin (mTOR) exclude Los1 from the nucleus in a Rad53-dependent manner. Moreover, lifespan extension from deletion of LOS1 is nonadditive with DR or mTOR inhibition, and results in Gcn4 transcription factor activation. Thus, the DNA damage response and mTOR converge on Los1-mediated nuclear tRNA export to regulate Gcn4 activity and aging.

Stress profiling of longevity mutants identifies Afg3 as a mitochondrial determinant of cytoplasmic mRNA translation and aging.

Although environmental stress likely plays a significant role in promoting aging, the relationship remains poorly understood. To characterize this interaction in a more comprehensive manner, we examined the stress response profiles for 46 long-lived yeast mutant strains across four different stress conditions (oxidative, ER, DNA damage, and thermal), grouping genes based on their associated stress response profiles. Unexpectedly, cells lacking the mitochondrial AAA protease gene AFG3 clustered strongly with long-lived strains lacking cytosolic ribosomal proteins of the large subunit. Similar to these ribosomal protein mutants, afg3Δ cells show reduced cytoplasmic mRNA translation, enhanced resistance to tunicamycin that is independent of the ER unfolded protein response, and Sir2-independent but Gcn4-dependent lifespan extension. These data demonstrate an unexpected link between a mitochondrial protease, cytoplasmic mRNA translation, and aging.

Dietary restriction and mitochondrial function link replicative and chronological aging in Saccharomyces cerevisiae.

Chronological aging of budding yeast cells results in a reduction in subsequent replicative life span through unknown mechanisms. Here we show that dietary restriction during chronological aging delays the reduction in subsequent replicative life span up to at least 23days of chronological age. We further show that among the viable portion of the control population aged 26days, individual cells with the lowest mitochondrial membrane potential have the longest subsequent replicative lifespan. These observations demonstrate that dietary restriction modulates a common molecular mechanism linking chronological and replicative aging in yeast and indicate a critical role for mitochondrial function in this process.

Molecular mechanisms underlying genotype-dependent responses to dietary restriction.

Dietary restriction (DR) increases lifespan and attenuates age-related phenotypes in many organisms; however, the effect of DR on longevity of individuals in genetically heterogeneous populations is not well characterized. Here, we describe a large-scale effort to define molecular mechanisms that underlie genotype-specific responses to DR. The effect of DR on lifespan was determined for 166 single gene deletion strains in Saccharomyces cerevisiae. Resulting changes in mean lifespan ranged from a reduction of 79% to an increase of 103%. Vacuolar pH homeostasis, superoxide dismutase activity, and mitochondrial proteostasis were found to be strong determinants of the response to DR. Proteomic analysis of cells deficient in prohibitins revealed induction of a mitochondrial unfolded protein response (mtUPR), which has not previously been described in yeast. Mitochondrial proteotoxic stress in prohibitin mutants was suppressed by DR via reduced cytoplasmic mRNA translation. A similar relationship between prohibitins, the mtUPR, and longevity was also observed in Caenorhabditis elegans. These observations define conserved molecular processes that underlie genotype-dependent effects of DR that may be important modulators of DR in higher organisms.

pH neutralization protects against reduction in replicative lifespan following chronological aging in yeast.

Chronological and replicative aging have been studied in yeast as alternative paradigms for post-mitotic and mitotic aging, respectively. It has been known for more than a decade that cells of the S288C background aged chronologically in rich medium have reduced replicative lifespan relative to chronologically young cells. Here we report replication of this observation in the diploid BY4743 strain background. We further show that the reduction in replicative lifespan from chronological aging is accelerated when cells are chronologically aged under standard conditions in synthetic complete medium rather than rich medium. The loss of replicative potential with chronological age is attenuated by buffering the pH of the chronological aging medium to 6.0, an intervention that we have previously shown can extend chronological lifespan. These data demonstrate that extracellular acidification of the culture medium can cause intracellular damage in the chronologically aging population that is asymmetrically segregated by the mother cell to limit subsequent replicative lifespan.

Sir2 deletion prevents lifespan extension in 32 long-lived mutants.

Activation of Sir2 orthologs is proposed to increase lifespan downstream of dietary restriction. Here, we describe an examination of the effect of 32 different lifespan-extending mutations and four methods of DR on replicative lifespan (RLS) in the short-lived sir2Δ yeast strain. In every case, deletion of SIR2 prevented RLS extension; however, RLS extension was restored when both SIR2 and FOB1 were deleted in several cases, demonstrating that SIR2 is not directly required for RLS extension. These findings indicate that suppression of the sir2Δ lifespan defect is a rare phenotype among longevity interventions and suggest that sir2Δ cells senesce rapidly by a mechanism distinct from that of wild-type cells. They also demonstrate that failure to observe lifespan extension in a short-lived background, such as cells or animals lacking sirtuins, should be interpreted with caution.