Resilience, plasticity and robustness in gene expression during aging in the brain of outbred deer mice.

BACKGROUND: Genes that belong to the same network are frequently co-expressed, but collectively, how the coordination of the whole transcriptome is perturbed during aging remains unclear. To explore this, we calculated the correlation of each gene in the transcriptome with every other, in the brain of young and older outbred deer mice (P. leucopus and P. maniculatus). RESULTS: In about 25 % of the genes, coordination was inversed during aging. Gene Ontology analysis in both species, for the genes that exhibited inverse transcriptomic coordination during aging pointed to alterations in the perception of smell, a known impairment occurring during aging. In P. leucopus, alterations in genes related to cholesterol metabolism were also identified. Among the genes that exhibited the most pronounced inversion in their coordination profiles during aging was THBS4, that encodes for thrombospondin-4, a protein that was recently identified as rejuvenation factor in mice. Relatively to its breadth, abolishment of coordination was more prominent in the long-living P. leucopus than in P. maniculatus but in the latter, the intensity of de-coordination was higher. CONCLUSIONS: There sults suggest that aging is associated with more stringent retention of expression profiles for some genes and more abrupt changes in others, while more subtle but widespread changes in gene expression appear protective. Our findings shed light in the mode of the transcriptional changes occurring in the brain during aging and suggest that strategies aiming to broader but more modest changes in gene expression may be preferrable to correct aging-associated deregulation in gene expression.

Coordination in the unfolded protein response during aging in outbred deer mice.

Endoplasmic reticulum (ER) stress has been linked to various metabolic pathologies, neurodegeneration and aging. Although various mechanistic aspects of the resulting unfolded protein response (UPR) have been elucidated, its regulation in genetically diverse populations remains elusive. In the present study we evaluated the expression of chaperones BiP/GRP78, GRP94 and calnexin (CANX) in the lungs, liver and brain of 7 months old and 2-3 years old outbred deer mice P. maniculatus and P. leucopus. Chaperones' expression was highly variable between species, tissues and ages suggesting that levels of expression of individual chaperones do not change consistently during aging. Despite this variation, a high degree of coordination was maintained between chaperones' expression indicating the tight regulation of the UPR which is consistent with its adaptive activity to maintain homeostasis. In the brain though of older P. maniculatus, at which neurodegenerative changes were detected, loss of coordination was revealed, especially between BiP and either of GRP94 or calnexin which indicates that de-coordination rather than aberrant expression is linked to deregulation of the UPR in aging. These findings underscore the involvement of UPR in the onset of aging-related pathologies and suggest that beyond levels of expression, concerted activation may be of significance to attain homeostasis. These findings emphasize the value of genetically diverse models and suggest that beyond levels of expression of individual targets the coordination of transcriptional networks should be considered when links to pathology are explored.

Variability in the prescribing of intravenous fluids: A cross sectional multicentre analysis of clinical practice.

AIMS: Intravenous (IV) fluid administration continues to be a mainstay of care in General Surgery. Yet if they are prescribed incorrectly significant morbidity including electrolyte abnormalities, renal impairment and cardiac failure can develop. Despite this, it is frequently the responsibility of the most junior staff to prescribe IV fluids. We aim to analyse the understanding of IV fluid prescribing amongst junior doctors and to describe variability in clinical practice. METHODS: We undertook a multicentre questionnaire study. Foundation doctors and specialty trainees were invited to undertake a two part paper-based questionnaire. Part one analysed baseline knowledge of the concentration of commonly prescribed fluids. Part two consisted of four clinical vignettes requiring a IV fluid prescribing decision by the surveyed doctor. RESULTS: A total of 143 Doctors working in 8 hospitals were recruited. 65 (45.5%) doctors correctly stated the daily maintenance fluid requirements of water for an adult (25-30 mls/kg/day), while only 54 (37.8%) knew the sodium concentration of 0.9% NaCl. Lack of postgraduate experience (p = 0.011), qualifying from a medical school outside the United Kingdom (p < 0.0001) and working in one of the eight hospitals in this study (p < 0.0001) were associated with a lower knowledge level. There was limited consensus in prescribing in the responses to the 4 clinical scenarios, with 69 unique combinations of fluid choice, rate and volume prescribed. CONCLUSIONS: Knowledge of the constituents of common IV fluids and routine requirement for fluid and common electrolytes is poor across junior doctors of all grades, driving large variation in clinical practice.