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Ever since learning that the shortening of telomeres is linked to aging I've tried to figure out what causes cells to divide, and if it's possible to slow down the rate of cell division through life style changes.
How would, for example, increased or decreased metabolism affect the cell cycle? If we exercise a lot, would it tear on the cells in any way, forcing faster cell division?
My understanding is that telomeres are linked to cell senescence, which is not necessarily the same thing as organism senescence. So even if you could track down a method to slow cell division, it would more likely mess with organ function now rather than extend life.
Here's a nice summary of cell senescence: http://www.ncbi.nlm.nih.gov/books/NBK26877/#A3266
I did look into cell division in muscle, and new muscle cells come from satellite cells, rather than from mitotic division of currently active muscle cells.
Caloric restriction was the hot new way to live longer for a while, but studies in primates found that a sensible diet and good genetics have a bigger effect. Which is pretty much the T-shirt in medical science.
This question was asked last spring as well. Coincidence? Homework?
Metabolism does affect cell cycle. Stress is known to affect ageing.
Mitchell et al., (2014) report that there is a telomere shortening in kids who grow up in disadvantaged social environments.
Metabolism and stress are known to affect longevity and general health. After much research on genomic associations of diabetes, people have come to the conclusion that physical exercise helps.
Physical exercise is also known to stimulate neurogenesis in the hippocampus; the causes are not well understood (van Praag, 2008).
There are more of such reports. If you search you'll find.
WHO defines physical activity as any bodily movement produced by skeletal muscles that requires energy expenditure. Physical activity refers to all movement including during leisure time, for transport to get to and from places, or as part of a person&rsquos work. Both moderate- and vigorous-intensity physical activity improve health.
Popular ways to be active include walking, cycling, wheeling, sports, active recreation and play, and can be done at any level of skill and for enjoyment by everybody.
Regular physical activity is proven to help prevent and manage noncommunicable diseases such as heart disease, stroke, diabetes and several cancers. It also helps prevent hypertension, maintain healthy body weight and can improve mental health, quality of life and well-being.
Physical Activity Facts
Regular physical activity can help children and adolescents improve cardiorespiratory fitness, build strong bones and muscles, control weight, reduce symptoms of anxiety and depression, and reduce the risk of developing health conditions such as: 1
- Heart disease.
- Type 2 diabetes.
- High blood pressure.
- Lead to energy imbalance (e.g., expend less energy through physical activity than consumed through diet) and can increase the risk of becoming overweight or obese. 14
- Increase the risk of factors for cardiovascular disease, including hyperlipidemia (e.g., high cholesterol and triglyceride levels), high blood pressure, obesity, and insulin resistance and glucose intolerance. 1,5,6
- Increase the risk for developing type 2 diabetes. 1,7
- Increase the risk for developing breast, colon, endometrial, and lung cancers. 1
- Lead to low bone density, which in turn, leads to osteoporosis. 1
- Less than one-quarter (24%) of children 6 to 17 years of age participate in 60 minutes of physical activity every day. 8
- In 2017, only 26.1% of high school students participate in at least 60 minutes per day of physical activity on all 7 days of the previous week. 9
- In 2017, 51.1% of high school students participated in muscle strengthening exercises (e.g., push-ups, sit-ups, weight lifting) on 3 or more days during the previous week. 9
- In 2017, 51.7% of high school students attended physical education classes in an average week, and only 29.9% of high school students attended physical education classes daily. 9
- Aerobic: Most of the 60 minutes or more per day should be either moderate- or vigorous-intensity aerobic physical activity and should include vigorous-intensity physical activity on at least 3 days a week.
- Muscle-strengthening: As part of their 60 minutes or more of daily physical activity, children and adolescents should include muscle-strengthening physical activity on at least 3 days a week.
- Bone-strengthening: As part of their 60 minutes or more of daily physical activity, children and adolescents should include bone-strengthening physical activity on at least 3 days a week.
These guidelines state that children and adolescents be provided opportunities and encouragement to participate in physical activities that are appropriate for their age, that are enjoyable, and that offer variety. 3
The national recommendation for schools is to have a comprehensive approach for addressing physical education and physical activity in schools. 10&ndash12 This approach is called Comprehensive School Physical Activity Programs. 13
How Exercise Affects Your Brain
You have probably heard people say something along the lines of &ldquoyour brain is like a muscle.&rdquo That comparison certainly supports the brain training industry (by that I mean school) and keeps millions of youth around the world sitting at desks, doing math problems, writing essays, and dissecting unsuspecting amphibians - but is it true?
Interestingly, the brain-as-a-muscle comparison isn&rsquot all that accurate. If you want to build your glutes, you have to flex your glutes but when it comes to your brain, a more coincidental approach is more accurate. Getting busy working your glutes will also directly benefit your grey matter. Yes, exercising your butt will make you smarter!
Exercise affects the brain in many ways. It increases heart rate, which pumps more oxygen to the brain. It aids the release of hormones which provide an excellent environment for the growth of brain cells. Exercise also promotes brain plasticity by stimulating growth of new connections between cells in many important cortical areas of the brain. Research from UCLA even demonstrated that exercise increased growth factors in the brain which makes it easier for the brain to grow new neuronal connections.
From a more feel-good perspective, the same antidepressant-like effects associated with the "runner's high" has been correlated with a drop in stress hormones. A study from Stockholm showed that the antidepressant effect of running was also associated with more cell growth in the hippocampus, an area of the brain responsible for learning and memory. The study went as far as to say &ldquoThus, suppression of cell proliferation in the hippocampus could constitute one of the mechanisms that underlie depression, and physical activity might be an efficient antidepressant.&rdquo
What Factors Affect the Rate of Diffusion?
Molecules are constantly moving around due to the amount of thermal energy they have. This movement is affected by the size of the particle and the environment the particle is in. Particles will always move around in a medium but the overall rate of diffusion can be affected by many factors.
Concentration: Diffusion of molecules is entirely dependent on moving from an area of higher concentration to an area of lower concentration. In other words, diffusion occurs down the concentration gradient of the molecule in question. If the difference in concentration is higher, then the molecules will go down the concentration gradient faster. If there is not as great of a difference in concentration, the molecules will not move as quickly and the rate of diffusion will decrease.
Temperature: Particles move due to the kinetic energy associated with them. As temperature increases, the kinetic energy associated with each particle also increases. As a result, particles will move faster. If they can move faster, then they can also diffuse faster. Conversely, when the kinetic energy associated with the molecules decreases so does their movement. As a result, the rate of diffusion will be slower.
Mass of Particle: Heavier particles will move more slowly and so will have a slower rate of diffusion. Smaller particles on the other hand will diffuse faster because they can move faster. As is key with all factors affecting diffusion, movement of the particle is paramount in determining if diffusion is slowed down or sped up.
Solvent Properties: Viscosity and density greatly affect diffusion. If the medium that a given particle has to diffuse through is very dense or viscous, then the particle will have a harder time diffusing through it. So the rate of diffusion will be lower. If the medium is less dense or less viscous, then the particles will be able to move more quickly and will diffuse faster.
All of the factors affecting diffusion can have a combined effect. For example, a small ion may diffuse more quickly through a viscous solution than a large sugar molecule. The ion has a smaller size and thus is able to move faster. The large sugar molecule moves slower because of its size. The viscosity of the solution affects both but will compound the slowed diffusion that the larger molecule undergoes.
Any factor that speeds up movement of particles through a medium will result in a faster rate of diffusion.
Decline in physical activity often starts as early as age 7
Overall physical activity starts to decline already around the age of school entry. While the proportion of physically inactive individuals rises with age there still are groups of people who manage to increase their physical activity level in adulthood and old age.
While the level of physical activity varies between individuals, it can also vary within individuals during the life course. A recent study, carried out in collaboration between the University of Jyväskylä and LIKES Research Centre for Physical Activity and Health, systematically reviewed scientific articles identifying distinct subgroups of physical activity and the factors related to these subgroups in the general population in different countries during different life phases.
The proportion of the decreasingly active individuals was exceptionally high during childhood and adolescence. Drop-out from sport participation was prevalent in adolescence while the overall physical activity started to decline already around the age of school entry among highly, moderately and low active children. The studies using self-reported measures of physical activity reported the decline of physical activity to be initiated around the age of ten while studies using modern, objective measures of physical activity found the corresponding age to be as early as seven years of age.
"However, it seems that the physical activity level of those decreasing their physical activity does not approximate to the level of the inactive ones before reaching mid-age or old age," says PhD student Irinja Lounassalo from the Faculty of Sport and Health Sciences at the University of Jyväskylä. "Thus, despite the common declining tendency of physical activity throughout the life course, being physically active in childhood and adolescence may be of high importance since it can postpone the time of becoming inactive later on."
The results support previous findings of the relatively high proportion of persistently inactive individuals at all ages, with this proportion increasing with age. Interestingly, subgroups of increasingly active participants were observed among adults and older adults.
"In the future, special attention should be paid to these individuals who increase their physical activity, because it is important to understand how potential lifelong inactivity could be turned into activity," Lounassalo suggests.
Having parental support for an active lifestyle was associated with increasing physical activity among children and adolescents, low television viewing time with persistent activity among adolescents, smoking cessation with increased activity among adults, and no chronic illnesses, a low mortality rate and good physical functioning with persistent activity among older adults. Generally, male gender, being Caucasian and having higher socioeconomic status were associated with persistent activity.
"Since physical activity behavior stabilizes with age and inactivity is more persistent behavior than activity, interventions should be targeted at children early in life before their habits become stable," emphasizes Lounassalo. "Additionally, supporting schools and sport clubs is crucial for promoting an active lifestyle for all children. Since parents may have an effect on activating their children, parents would need support for finding ways to do that. Building publically available sport facilities and safe bicycling and walkways might help in increasing opportunities for being active regardless of age, nationality, gender or educational level."
Twenty-seven articles published between 2004 and 2018 were included in this systematic review. All of the included studies used the so-called trajectory approach for identifying the distinct subgroups (i.e. trajectory classes) from the data at hand.
"Only in recent years has the number of studies identifying distinct physical activity trajectory classes increased," Lounassalo explains. "In trajectory studies, the target behavior of individuals in the same trajectory class is expected to be similar, while it differs from that of the individuals in the other classes. The studies included in this review most commonly reported three or four physical activity subgroups describing either persistent, increasing or decreasing activity or inactivity."
Molecular Targets and Clinical Cancer Risk Reductive Interventions
Cellular growth requires polyamines, spermidine, spermine, and the diamine, putrescine. 139 Pharmacologic inhibition of polyamines stops cellular growth and proliferation. 139–141 Difluoromethylornithine (DFMO) is a potent, irreversible inhibitor of ornithine decarboxylase, inhibits polyamine metabolism, and prevents tumor promotion in a variety of systems—skin, mammary, colon, cervical, and bladder carcinogenesis models. 139 Synergistic or additive activity with retinoids, butylated hydroxyanisole, tamoxifen, piroxicam, and fish oil has been demonstrated with low concentrations of DFMO. 139,141 DFMO alone has not been proved safe and effective as a cancer risk reductive for common epithelial neoplasms, but in combination with sulindac, DFMO potently inhibits adenoma recurrence. 142
How does surface area to volume ratio affect the rate of diffusion?
Surface area to volume ratio, in simple means the size of surface area to the volume of substance that can pass through it at a particular time.
Amoeba and some bacterias are flat and have large surface area to volume ratio. So the diffusion rate is very high due to large surface area.
Where as humans have small surface area: volume so diffusion is very slow or does not take place at all.
As the ratio gets smaller, it takes longer for items to diffuse.
When the cell increases in size, the volume increases faster than the surface area, because volume is cubed where surface area is squared.
When there is more volume and less surface area, diffusion takes longer and is less effective. This is because there is a greater area that needs to receive the substance being diffused, but less area for that substance to actually enter the cell.
this is actually why cells divide. When they become too large and it takes too long for them to transport materials across the cell, they lose efficiency and divide in half to raise the surface area to volume ratio.
Factors Affecting the Enzyme Activity | Enzymology
The following points highlight the seven major factors affecting the enzyme activity. The factors are: 1. Temperature 2. Hydrogen Ion Concentration (pH) 3. Water 4. Concentration of the Substrate 5. Enzyme Concentration 6. Inhibitors 7. Accumulation of End-Products.
Factor # 1. Temperature:
Usually the activity of the enzymes is optimum at normal body temperature at very low temperature (i.e., about 0°C) the activity of the enzymes is minimum.
An increase in temperature up to a certain limit increases the enzyme activity, maximum being at about 45°C after which the enzyme activity is retarded (Fig. 1.10) Beyond 60°-70°C usually their activity is permanently stopped due to the denaturation of enzymes.
Factor # 2. Hydrogen Ion Concentration (pH):
Enzymes are active only over a limited range of pH. Some enzymes, e.g., trypsin are active in alkaline medium (high pH), diastase in neutral medium, while pepsiti shows optimum activity in acidic medium (low pH).
Factor # 3. Water:
In absence of water the enzyme activity is suppressed so much so that in dry seeds the enzymes are almost inactive.
Proper hydration of the cells is necessary for enzyme activity because (i) water provides medium for enzyme reaction to take place, and (ii) in many cases it is one of the reactants.
Factor # 4. Concentration of the Substrate:
Increase in the concentration, of the substrate brings about an increase in the activity of the enzyme till all the active sites of the enzyme molecules are saturated with substrate. After this the rate of enzyme reaction becomes steady and addition of the substrate will not have positive effect (Fig. 1.11).
Factor # 5. Enzyme Concentration:
Usually a very small amount of the enzyme can consume large amount of the substrate. Increase in the concentration of the enzyme will increase the rate of reaction catalyzed by it provided there is enough concentration of substrate (Fig. 1.12). It is because (i) increased number of enzyme molecules will have more active sites, and (ii) at higher concentration of the enzyme the inhibitors will fall short.
Factor # 6. Inhibitors:
Presence of inhibitors in the reaction mixture inhibits the activity of the enzymes partially or completely depending upon the nature of the inhibitors. Inhibitors are less effective when the concentration of the enzyme and substrate is higher.
Inhibitors are of two types:
(i) Competitive Inhibitors:
Such inhibitors have structural similarity with the substrate both of which compete for the same active site of enzyme. If competitive inhibitor pre-occupies the active site, the substrate molecule will be unable to combine with the enzyme and hence, the enzyme activity will be inhibited. But, this inhibition is of reversible type because removal of the competitive inhibitor restores the activity of the enzyme.
(ii) Non-Competitive Inhibitors:
These are usually poisons which do not compete for the active sites but destroy the structure of the enzyme and cause permanent or irreversible inhibition of the activity of the enzyme.
Factor # 7. Accumulation of End-Products:
Accumulation of the end-products retards the enzymic activity mainly because the active sites of the enzymes are crowded by them and substrate molecules will have comparatively lesser chance of combining with the active sites.
The effect of time-dependent deformation of viscoelastic hydrogels on myogenic induction and Rac1 activity in mesenchymal stem cells
Cell behaviours within tissues are influenced by a broad array of physical and biochemical microenvironmental factors. Whilst 'stiffness' is a recognised physical property of substrates and tissue microenvironments that influences many cellular behaviours, tissues and their extracellular matrices are not purely rigid but 'viscoelastic' materials, composed of both rigid-like (elastic) and dissipative (viscous) elements. This viscoelasticity results in materials displaying increased deformation with time under the imposition of a defined force or stress, a phenomenon referred to as time-dependent deformation or 'creep'. Previously, we compared the behaviour of human mesenchymal stem cells (hMSCs) on hydrogels tailored to have a constant stiffness, but to display varying levels of creep in response to an applied force. Using polyacrylamide as a model material, we showed that on high-creep hydrogels (HCHs), hMSCs displayed increased proliferation, spread area and differentiation towards multiple lineages, compared to their purely stiff analogue, with a particular propensity for differentiation towards a smooth muscle cell (SMC) lineage. In this present study, we investigate the mechanisms behind this phenomenon and show that hMSCs adhered to HCHs have increased expression of SMC induction factors, including soluble factors, ECM proteins and the cell-cell adhesion molecule, N-Cadherin. Further, we identify a key role for Rac1 signalling in mediating this increased N-Cadherin expression. Using a real-time Rac1-FRET biosensor, we confirm increased Rac1 activation on HCHs, an observation that is further supported functionally by observed increases in motility and lamellipodial protrusion rates of hMSCs. Increased Rac1 activity in hMSCs on HCHs provides underlying mechanisms for enhanced commitment towards a SMC lineage and the compensatory increase in spread area (isotonic tension) after a creep-induced loss of cytoskeletal tension on viscoelastic substrates, in contrast to previous studies that have consistently demonstrated up-regulation of RhoA activity with increasing substrate stiffness. Tuning substrate viscoelasticity to introduce varying levels of creep thus equips the biomaterial scientist or engineer with a new tool with which to tune and direct stem cell outcomes.
Keywords: Creep Hydrogel Mechanotransduction Mesenchymal stem cell Smooth muscle cell Viscoelasticity.
Watch the video: Biologie: Die Zellteilung (August 2022).