Measurable Constitutional Characters and Selective Survival in Hungarian Centenarians

2015 ◽  
pp. 31-39
Author(s):  
Ott� G. Eiben ◽  
�va B. Bodzs�r
Keyword(s):  
Selective Survival

scholarly journals Detecting the Effects of Early-Life Exposures: Why Fecundity Matters

2019 ◽  
Author(s):  
Jenna Nobles ◽  
Amar Hamoudi
Keyword(s):  
Infant Health ◽  
Statistical Significance ◽  
Absolute Magnitude ◽  
Later Life ◽  
Contrast Effects ◽  
Fetal Origins ◽  
Health Trajectories ◽  
Maternal And Infant Health ◽  
Selective Survival ◽  
Early Life Exposures

Prenatal exposures have meaningful effects on health across the lifecourse. Innovations in causal inference have shed new light on these effects. Here, we motivate the importance of innovation in the characterization of fecundity, and prenatal selection in particular. We argue that such innovation is crucial for expanding knowledge of the fetal origins of later life health. Pregnancy loss is common, responsive to environmental factors, and closely related to maternal and fetal health outcomes. As a result, selection into live birth is driven by many of the same exposures that shape the health trajectories of survivors. Lifecourse effects that are inferred without accounting for these dynamics may be significantly distorted by survival bias. We use a set of Monte Carlo simulations with realistic parameters to examine the implications of prenatal survival bias. We find that even in conservatively specified scenarios, true fetal origin effects can be underestimated by 50% or more. In contrast, effects of exposures that reduce the probability of prenatal survival but improve the health of survivors will be overestimated. The absolute magnitude of survival bias can even exceed small effect sizes, resulting in inferences that beneficial exposures are harmful or vice-versa. We also find reason for concern that moderately sized true effects, underestimated due to failure to account for selective survival, are missing from scientific knowledge because they do not clear statistical significance filters. This bias has potential real-world costs; policy decisions about interventions to improve maternal and infant health will be affected by underestimated program impact.

Selective Survival, Aging, and Society

2020 ◽  
pp. 187-205
Author(s):  
Kyriakos S. Markides ◽  
Richard Machalek
Keyword(s):  
Selective Survival

The regulation of metabolic clearance rate of human FSH in mice by variation of the molecular structure of the hormone

1986 ◽  
Vol 112 (3) ◽  
pp. 336-344 ◽  
Author(s):  
Leif Wide
Keyword(s):  
Clearance Rate ◽  
Ovarian Function ◽  
Metabolic Clearance ◽  
Gradual Change ◽  
Metabolic Clearance Rate ◽  
Physiological Importance ◽  
Selective Survival ◽  
Veronal Buffer ◽  
Rapid Clearance ◽  
The Individual

Abstract. The relationship between charge on human FSH (hFSH) molecules and their metabolic clearance rate (MCR) was investigated. The median charge of the hFSH molecules was expressed as their median mobility at electrophoresis in 0.075 m sodium veronal buffer, pH 8.6. MCR was estimated after single iv injection in mice of unfractionated and fractionated extracts of human pituitaries. There was a highly significant (P < 0.001) correlation between charge and MCR both for forms of FSH present within the individual pituitary and for FSH in different pituitaries. After the iv injection there was a gradual change to a more negative median charge of hFSH in plasma. This was explained by the more rapid clearance of the less negatively charged forms of hFSH and thus selective survival of different forms in the circulation. This is a most likely explanation for the differences in median charge between FSH in pituitaries and in sera of men and women of corresponding age. The results suggest that MCR of human FSH is controlled by a gonadal-pituitary feed-back mechanism which involves changes in the structure of the FSH produced by the pituitary. It is suggested that charge is one factor involved in the regulation of the survival of FSH in the circulation and that this is of physiological importance for the control of the ovarian function during the menstrual cycle.

scholarly journals Lack of association between the MTHFR C677T variant and migraine with aura in an older population: Could selective survival play a role?

Cephalalgia ◽  
2012 ◽  
Vol 33 (5) ◽  
pp. 308-315 ◽  
Author(s):  
Ann I Scher ◽  
Gudny Eiriksdottir ◽  
Melissa Garcia ◽  
Preethy Feit ◽  
Albert V Smith ◽  
...  
Keyword(s):  
Risk Factor ◽  
Migraine With Aura ◽  
Multinomial Logistic Regression ◽  
Meta Analysis ◽  
Mthfr C677t ◽  
Clinical Population ◽  
Older Population ◽  
Simple Simulation ◽  
Selective Survival ◽  
Measured Effect

Background: Several studies, but not all, of primarily middle-aged or younger adults have suggested that the common MTHFR C677T variant is a genetic risk factor for migraine with aura (MA). Here, we consider whether this variant is associated with MA risk in an older non-clinical population (AGES-Reykjavik cohort). Methods: Participants are a sub-sample ( n = 1976) of subjects from the Reykjavik Study (RS; mean age 50) and its continuation, AGES-RS (mean age 76). We estimated the relative odds of MA in TT versus CC carriers using multinomial logistic regression. As both MA and the TT genotype may be linked with modestly reduced longevity, we performed a simple simulation to illustrate the effect that selective survival may have had on our observed gene–disease association. Results: TT versus CC carriers were at marginally reduced odds of MA (ORTT 0.55 (0.3–1.0), p = 0.07), significantly for women (ORTT 0.45 (0.2–0.9), p = 0.03). Assuming the ‘true’ (e.g. mid-life) effect of the TT genotype is ORTT 1.26, from a recent meta-analysis, our simulation suggested that if 25-year mortality had been (hypothetically) 13% higher in MA subjects with the TT versus CC genotype, the measured effect of the TT genotype on MA would have been attenuated to non-significance (e.g. ORTT 1.00). Our observed protective effect was consistent with the most extreme selective mortality scenario, in which essentially all of the previously reported increased mortality in MA subjects was (hypothetically) found in CT or TT carriers. Conclusion: The MTHFR 677TT genotype was associated with marginally reduced risk of MA in our older population. Our simulation illustrated how even modest selective survival might obscure the apparent effect of a genetic or other risk factor in older populations. We speculate that some of the heterogeneity previously observed for this particular genetic variant may be due to age range differences in the studied populations.

Selective survival of calretinin- and vasoactive-intestinal-peptide-containing nerve elements in human chagasic submucosa and mucosa

2012 ◽  
Vol 349 (2) ◽  
pp. 473-481 ◽  
Author(s):  
Samir Jabari ◽  
Alexandre B. M. da Silveira ◽  
Enio C. de Oliveira ◽  
Salustiano G. Neto ◽  
Karl Quint ◽  
...  
Keyword(s):  
Vasoactive Intestinal Peptide ◽  
Selective Survival

scholarly journals Ciliary neurotrophic factor induces cholinergic differentiation of rat sympathetic neurons in culture.

1989 ◽  
Vol 108 (5) ◽  
pp. 1807-1816 ◽  
Author(s):  
S Saadat ◽  
M Sendtner ◽  
H Rohrer
Keyword(s):  
Neurotrophic Factor ◽  
Specific Activity ◽  
Sympathetic Neurons ◽  
Ciliary Neurotrophic Factor ◽  
Activity Levels ◽  
Term Survival ◽  
Selective Survival ◽  
Enzyme Molecules

Ciliary neurotrophic factor (CNTF) influences the levels of choline acetyltransferase (ChAT) and tyrosine hydroxylase (TH) in cultures of dissociated sympathetic neurons from newborn rats. In the presence of CNTF both the total and specific activity of ChAT was increased 7 d after culture by 15- and 18-fold, respectively, as compared to cultures kept in the absence of CNTF. Between 3 and 21 d in culture in the presence of CNTF the total ChAT activity increased by a factor of greater than 100. Immunotitration demonstrated that the elevated ChAT levels were due to an increased number of enzyme molecules. In contrast to the increase in ChAT levels, the total and specific activity levels of TH were decreased by 42 and 36%, respectively, after 7 d in culture. Half-maximal effects for both ChAT increase and TH decrease were obtained at CNTF concentrations of approximately 0.6 ng and maximal levels were reached at 1 ng of CNTF per milliliter of medium. The effect of CNTF on TH and ChAT levels were seen in serum-containing medium as well as in serum-free medium. CNTF was shown to have only a small effect on the long-term survival of rat sympathetic neurons. We therefore concluded that the effects of CNTF on ChAT and TH are not due to selective survival of cells that acquire cholinergic traits in vitro, but are rather due to the induction of cholinergic differentiation of noradrenergic sympathetic neurons.

Selective Survival of Double-Walled CNTs after In Situ H2 Plasma Treatment of Vertically-Grown Multi-Walled CNTs

2012 ◽  
Vol 1 (4) ◽  
pp. M24-M26 ◽  
Author(s):  
Y. J. Shin ◽  
S. I. Cha ◽  
H.-Y. Choi ◽  
J. H. Moon ◽  
I. H. Kang ◽  
...  
Keyword(s):  
Plasma Treatment ◽  
Selective Survival ◽  
Walled Cnts
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