Much attention in biogerontology is paid to the deceleration of mortality rate increase with age by the end of a species-specific lifespan, e.g. after ca. 90 years in humans. Being analyzed based on ...the Gompertz law
µ
(
t
)=
µ
0
e^
γt
with its inbuilt linearity of the dependency of ln
µ
on
t
, this is commonly assumed to reflect the heterogeneity of populations where the frailer subjects die out earlier thus increasing the proportions of those whose dying out is slower and leading to decreases in the demographic rates of aging. Using Human Mortality Database data related to France, Sweden and Japan in five periods 1920, 1950, 1980, 2018 and 2020 and to the cohorts born in 1920, it is shown by LOESS smoothing of the ln
µ
-vs-
t
plots and constructing the first derivatives of the results that the late-life deceleration of the life-table aging rate (LAR) is preceded by an acceleration. It starts at about 65 years and makes LAR at about 85 years to become 30% higher than it was before the acceleration. Thereafter, LAR decreases and reaches the pre-acceleration level at ca. 90 years. This peculiarity cannot be explained by the predominant dying out of frailer subjects at earlier ages. Its plausible explanation may be the acceleration of the biological aging in humans at ages above 65–70 years, which conspicuously coincide with retirement. The decelerated biological aging may therefore contribute to the subsequent late-life LAR deceleration. The biological implications of these findings are discussed in terms of a generalized Gompertz-Makeham law
µ
(
t
) =
C
(
t
)+
µ
0
e^f(
t
).
According to the Gompertz law, the age-dependent change in the logarithm of mortality (life-table aging rate, LAR) is equal to the population-averaged age-independent biological aging rate (γ), and ...LAR would be constant if aging were the only cause of mortality increase. However, LAR is influenced by population exposures to the external hazards. If they were constant, according to the Gompertz-Makeham law (GML), LAR would be below γ at lower ages and asymptotically and monotonically approach γ with increasing age. Actually, LAR trajectories derived from data on mortality in different countries and historical periods feature systematic undulations. In the present investigation, mortality-vs.-age trajectories were modeled based on a generalized GML (gGML). Unlike the canonical GML terms, which are population-specific constants, the respective terms of the gGML are represented with some population-specific functions of age. Invariant in gGML are the modes of translation of these functions into the dependency of mortality on age: linear for population exposure to the irresistible external hazards or exponential for population-averaged ability to withstand the resistible external and internal hazards. Modeling suggests that, at earlier ages, LAR undulations are attributable to changes in population exposures to the former hazards. However, only their unrealistically high levels can produce the transient increase in LAR at about 65 to 90 years. This pervasive undulation of LAR-vs.-age trajectory is rather caused by an increment in γ. Reasons to regard gGML as a genuine natural law, which defines relations between mortality, aging and environment, are discussed.According to the Gompertz law, the age-dependent change in the logarithm of mortality (life-table aging rate, LAR) is equal to the population-averaged age-independent biological aging rate (γ), and LAR would be constant if aging were the only cause of mortality increase. However, LAR is influenced by population exposures to the external hazards. If they were constant, according to the Gompertz-Makeham law (GML), LAR would be below γ at lower ages and asymptotically and monotonically approach γ with increasing age. Actually, LAR trajectories derived from data on mortality in different countries and historical periods feature systematic undulations. In the present investigation, mortality-vs.-age trajectories were modeled based on a generalized GML (gGML). Unlike the canonical GML terms, which are population-specific constants, the respective terms of the gGML are represented with some population-specific functions of age. Invariant in gGML are the modes of translation of these functions into the dependency of mortality on age: linear for population exposure to the irresistible external hazards or exponential for population-averaged ability to withstand the resistible external and internal hazards. Modeling suggests that, at earlier ages, LAR undulations are attributable to changes in population exposures to the former hazards. However, only their unrealistically high levels can produce the transient increase in LAR at about 65 to 90 years. This pervasive undulation of LAR-vs.-age trajectory is rather caused by an increment in γ. Reasons to regard gGML as a genuine natural law, which defines relations between mortality, aging and environment, are discussed.
Neuron-Specific Enolase-What Are We Measuring? Babkina, Anastasiya S; Lyubomudrov, Maxim A; Golubev, Mikhail A ...
International journal of molecular sciences,
05/2024, Letnik:
25, Številka:
9
Journal Article
Recenzirano
Odprti dostop
Since the discovery of the neuron-specific protein by Moore and McGregor in 1965, tens of thousands of studies have investigated the basic and applied significance of neuron-specific enolase (NSE). ...This promising biomarker, according to many researchers, has not found widespread use in clinical practice, particularly in acute cerebrovascular accidents. Moreover, the several studies refuting the usefulness of serum NSE measurement in critically ill patients leads us to consider the reasons for such contradictory conclusions. In this article, we have analyzed the main directions in the study of NSE and expressed our perspective on the reasons for the contradictory results and the difficulties in implementing the results of these studies in clinical practice. In our opinion, the method of the enzyme-linked immunosorbent assay (ELISA) used in the majority of the studies is inappropriate for the evaluation of NSE as a marker of central nervous system damage, because it does not allow for the differentiation of heterodimers of enolases and the assessment of the enzymatic activity of this group of enzymatic proteins. Therefore, the methodological approach for the evaluation of NSE (γγ-enolase) as a biomarker needs to be elaborated and improved. Furthermore, the specificity of the applied research methods and the appropriateness of the continued use of the term "neuron-specific enolase" must be addressed.
When mortality (
μ
), aging rate (
γ
) and age (
t
) are treated according to the Gompertz model
μ
(
t
) =
μ
0
e
γt
(GM), any mean age corresponds to a manifold of paired reciprocally changing
μ
0
...and
γ
. Therefore, any noisiness of data used to derive GM parameters makes them negatively correlated. Besides this artifactual factor of the Strehler–Mildvan correlation (SMC), other factors emerge when the age-independent mortality
C
modifies survival according to the Gompertz–Makeham model
μ
(
t
) =
C
+
μ
0
e
γt
(GMM), or body resources are partitioned between survival and protection from aging the compensation effect of mortality (CEM). Theoretical curves in (
γ
, log
μ
0
) coordinates show how
μ
0
decreases when
γ
increases upon a constant mean age. Within a species-specific range of
γ
, such “isoage” curves look as nearly parallel straight lines. The slopes of lines constructed by applying GM to survival curves modeled according to GMM upon changes in
C
are greater than the isoage slopes. When CEM is modeled, the slopes are still greater. Based on these observations, CEM is shown to contribute to SMC associated with sex differences in lifespan, with the effects of several life-extending drugs, and with recent trends in survival/mortality patterns in high-life-expectancy countries; whereas changes in
C
underlie differences between even high-life-expectancy countries, not only between high- and low-life-expectancy countries. Such interpretations make sense only if GM is not merely a statistical model, but rather reflects biological realities. Therefore, GM is discussed as derivable by applying certain constraints to a natural law termed the generalized Gompertz–Makeham law.
A panel of published distributions of cell interdivision times (IDT) comprising 77 datasets related to 16 cell types, some studied under different conditions, was used to evaluate their conformance ...to the exponentially modified gamma distribution (EMGD) in comparison with distributions suggested for IDT data earlier. Lognormal, gamma, inverse Gaussian, and shifted Weibull and gamma distributions were found to be generally inferior to EMGD. Exponentially modified Gaussian (EMG) performed equally well. Although EMGD or EMG may be worse than some other distributions in specific cases, the reason that IDT distributions must be generated by a common mechanism of the cell cycle makes it unlikely that they differ essentially in different cell types. Therefore, exponentially modified peak functions, such as EMGD or EMG, are most appropriate if the use of a single distribution for IDT data is reasonable. EMGD is also shown to be the best descriptive tool for published data on the distribution of times between the bursts of mRNA synthesis at defined genes in single cells. EMG is inadequate to such data because its Gaussian component markedly extends to the negative time domain. The applicability of EMGD to comparable features of cells and genes behaviors are discussed to support the validity of the transition probability model and to relate the exponential component of EMGD to the times of cell dwelling in the restriction point of the cell cycle.
•A closed form formula for convolved gamma and exponent distributions is suggested.•It fits cell interdivision time distributions better than other functions do.•It fits as well the distributions of times between gene expression bursts.•Implications of fitting the two distributions with one function are discussed.
We report on a precision energy loss measurement and theoretical investigation of 100 keV/u helium ions in a hydrogen-discharge plasma. Collision processes of helium ions with protons, free ...electrons, and hydrogen atoms are ideally suited for benchmarking plasma stopping-power models. Energy loss results of our experiments are significantly higher than the predictions of traditional effective charge models. We obtained good agreement with our data by solving rate equations, where in addition to the ground state, also excited electronic configurations were considered for the projectile ions. Hence, we demonstrate that excited projectile states, resulting from collisions, leading to capture-, ionization-, and radiative-decay processes, play an important role in the stopping process in plasma.
During the primary treatment of oil, gas and water, complications arise associated with the presence of hard water-oil emulsions, which cause an increase in fluid pressure in the gathering systems, ...pipeline damage, as well as difficulties in gas separation and preliminary water discharge at the preliminary discharge unit (PRU). Additional problems arise during transportation of highly paraffinic oils associated with the crystallization of paraffin in the flow path of the oilfield equipment and on the inner surface of pipes, leading to a drop in the productivity of pipelines.
Article discusses the technology of magnetic-reagent treatment of water-oil media, which allows intensifying the processes of primary oil treatment at the facilities of its production. Bench and pilot tests have shown the ability of the magnetic field to accelerate oil demulsification processes, increasing the percentage of separated water during subsequent settling, and to reduce asphalt-resin-paraffin deposits (ARPD) on the inner surface of oil and gas field equipment.
Mechanism of the magnetic field effect on water-oil media is described. Effect of treatment on the integrity of the armour shells of oil-water emulsions was studied. Various modes of magnetic treatment have been investigated with evaluation of its effectiveness. It is shown that the best effect is achieved with the combined use of reagents and a magnetic field. Synergistic effect is observed, which consists in increasing their effectiveness. This made it possible to conclude that this method can be applied to reduce the consumption of reagents used in oil production while maintaining the treatment efficiency.
The physicochemical characteristics and functional properties of pumpkin (Cucurbita maxima D. var. Cabello de Ángel) pectin obtained by cavitation facilitated extraction from pumpkin pulp have been ...evaluated and compared with commercial citrus and apple pectins. C. maxima pectin had an Mw value of 90 kDa and a high degree (72%) of esterification. The cytoprotective and antioxidant effects of citrus, apple and pumpkin pectin samples with different concentrations were studied in vitro in cell lines HT-29 (human colon adenocarcinoma) and MDCK1 (canine kidney epithelium). All pectin samples exhibited cytoprotective effect in HT-29 and MDCK1 cells after incubation with toxic concentrations of cadmium and mercury for 4 h. Pumpkin pectin increased the proliferation of cadmium-treated MDCK1 cells by 210%. The studied pectins also inhibited oxidative stress induced by 2,2'-azobis(2-methylpropionamidine) dihydrochloride (AAPH) in cell cultures, as determined by measuring the production of intracellular reactive species using dihydrochlorofluorescein diacetate (DCFH-DA). Pectin from pumpkin pomace had the highest (p < 0.05) protective effect against reactive oxygen species generation in MDCK1 cells induced by AAPH. Distinctive features of pumpkin pectin were highly branched RG-I regions, the presence of RG-II regions and the highest galacturonic acid content among the studied samples of pectins. This correlates with a considerable protective effect of C. maxima pectin against oxidative stress and cytotoxicity induced by heavy metal ions. Thus, C. maxima pectin can be considered as a source of new functional foods of agricultural origin.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Positively skewed distributions common in biology are often approximated with lognormal or gamma functions. It is shown here that for some classes of phenomena, including intermitotic time and ...protein expression variabilities, exponentially modified Gaussian (EMG) may provide better fit. EMG is generated by processes involving normally distributed entry rates and exponentially distributed exit rates; therefore, its parameters may be straightforwardly interpreted in biologically meaningful terms and thus may help to choose between theoretical models of the respective phenomena. In particular, EMG is consistent with the transition probability model of cell cycle and may be used to estimate its deterministic and probabilistic parts. EMG is also consistent with the assumption that the probabilistic part is determined by competing stochastic transcriptional events committing cells to proliferative mitoses, differentiation, or apoptosis. Discrete event simulation modelling of this situation suggests that cell differentiation rate is primarily increased by decreasing the frequencies of the events that result in the realisation of the competing options, including proliferation, rather than by the direct changes in the differentiation-inducing events.
Abstract
This paper deals with an optimal motion planning method for mechanical systems subjected to velocity and acceleration constraints in the presence of dynamical geometric obstacles. Using a ...state parametrization method based on time polynomials the trajectory planning problem is reformulated as a constrained nonlinear optimization problem which is solved using a numerical optimization toolbox. Quadrotor motion planning in the horizontal plane is considered as an illustration example.
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