Showing posts with label an. Show all posts
Showing posts with label an. Show all posts
Friday, November 28, 2014
Is 3D printing an environmental win
Jeremy Faludi at GreenBiz.com has a look at the environmental impact of 3d printing - Is 3D printing an environmental win ?. 
Read More..
Technophilic environmentalists, including myself, tout the 3D printing revolution as a boon that could eliminate waste in manufacturing. But is that really true? Even if it is true, does it matter compared to the extra energy used? And what about toxins — does it release more, or less? No one has done this comparison before in a comprehensive, quantitative way, so some colleagues and I in the UC Berkeley mechanical engineering department set out to find the answers. The results were tricky and surprising.First, lets bust a myth: 3D printing does not mean zero waste. There are many kinds of 3D printers, making things in very different ways; we measured two kinds. An "FDM" machine (such as a RepRap or Makerbot, sort of a hot glue gun with XYZ controls), actually can have a negligible percent waste, if your model doesnt need any support material to shore it up while printing. (Thats a big "if.") But we found that an inkjet 3D printer (which lays down polymeric ink and UV-cures it layer by layer) wastes 40 to 45 percent of its ink, not even counting support material, and it cant be recycled. Other researchers studying other kinds of 3D printers have found significant waste in some of them as well.
To see whether 3D printing will be a sustainability win, we compared it to machining by a computer-controlled mill (starting with a block of stuff and cutting away everything you dont want). We only looked at machining things out of plastic, because thats what these FDM and inkjet 3D printers do. Lets be clear: most plastic consumer products are not machined; theyre injection-molded. But 3D printing is not going to replace injection-molding for mass-manufactured products (plastic parts made in the millions). It is replacing machining for smaller runs (1 unit, 10 units, maybe 1,000 units).
We compared them by doing a life-cycle assessment (LCA) of the two 3D printers and the CNC mill, including the materials and manufacturing of the machines themselves, transportation, energy use, material in the final parts, material wasted, and the end-of-life disposal of the machines. ...
The 3D printers impacts mostly came from electricity use, which is simply a function of time, so anything that reduces the time spent running also reduces eco-impacts. The mills impacts were mostly from material use and waste, but energy use was significant too. The resources and manufacturing to make the machines themselves was a small portion of impacts when they run at high utilization, as shown above; but if you only make one part per week, those embodied impacts can be significant for the FDM and the mill.
The final verdict, then, is that 3D printing can be greener, if its the right kind (FDM); but again, the biggest environmental win comes from sharing the fewest tools so each has the most utilization. If you want to know more, the full study (with far more detail in methodology and results, including breakdowns of impacts by source for all 22 scenarios studied) has been submitted to the Journal of Rapid Prototyping. Be patient, though; peer-reviewed academic publications take a year or more to get published.
Sunday, September 14, 2014
What does marathon running do to an athletes cells
If youve ever taken up running as a form of exercise, or even thought about it, theres a certain paradox that may have occurred to you. The health benefits of aerobic exercise are well-documented. (See here, for example.) In particular such exercise has been shown to reduce risks of cardiovascular disease, diabetes, and some forms of cancer. Beneficial physiological effects include reduction of high blood pressure, better control of blood sugar, and reducing blood levels of low-density lipoprotein while raising levels of high-density lipoprotein.
On the other hand, exercise necessarily increases a persons rate of metabolism, as food is processed to provide energy expended through exercise. An inevitable side-effect of metabolism is the production of reactive oxygen species (ROS) and "free radicals" that can damage DNA and other cellular constituents. This cellular damage can lead to either cancer or accelerated aging due to cell senescence and cell death.
The paradox, then, is that the health benefits of exercise do not seem to be canceled out by the side-effects of higher rates of metabolism. Its an important issue not just for humans who are trying to stay healthy, but even more important in animals like birds that may need to expend energy continuously over significant periods of time.
So whats going on here? Perhaps this research has some of the answer:
The effect of marathon on mRNA expression of anti-apoptotic and pro-apoptotic proteins and sirtuins family in male recreational long-distance runners
There are two main findings here, related to apoptosis and sirtuin expression. Lets take them in order.
Apoptosis is a form of programmed cell death that has several purposes. The invocation of a cells apopotosis program isnt necessarily an indication that something is wrong. For example, it occurs normally during embryonic development. Early in the development process embryos of all tetrapods have tissues between what will become the fingers and toes of their hands and feet. But since animals that have left an aquatic environment are usually better off without this extra tissue, evolution has led to signals at a certain stage of embryonic development that cause apoptosis in the cells of the relevant tissue. This is an example of whats known as the "extrinsic" apoptotic pathway.
But for our present purposes theres a second pathway – the "intrinsic" pathway – which is used whenever a cell either detects internal damage (usually to its DNA) or some stressful condition, such as an excessive level of reactive oxygen species. A ROS is a chemically-reactive molecule containing oxygen, including what are sometimes called "free radicals".
This condition of excess ROS is called oxidative stress. It can occur for various reasons, including exposure to high levels of heat or ultraviolet radiation – or abnormally rapid cell metabolism due to vigorous exercise. Cells recognize the condition of oxidative stress indirectly though signaling involving various other molecules that are produced in response to particular ROS molecules. Among such indicators are proteins called heat shock proteins. Two members of this family that were measured in the research under discussion were HSP70 and HSP32.
Signals of oxidative stress trigger the second, "intrinsic" apoptotic pathway, which involves a cells energy-producing organelles, the mitochondria. The main players in the intrinsic pathway are proteins called, generically, "caspases" – short for "cysteine-rich aspartate proteases". Caspases are enzymes that cleave proteins at aspartate units. (Cysteine and aspartate are two of the 21 amino acids that normally make up proteins.)
Caspases are fairly active enzymes, so they dont ordinarily occur at significant concentrations within cells. Instead, they are produced when needed from other protein enzymes called procaspases. One of these, procaspase-9 is found normally within mitochondria, along with another protein, cytochrome c. Most of the time these proteins are confined within the mitochondria. However, under certain conditions some channels in a mitochondrions membrane can open and allow the release of procaspase-9 and cytochrome c. Once these proteins enter the cytosol (cell fluid) outside a mitochondrion, they can team up with another protein (Apaf-1: "apoptotic protease activating factor 1") to convert the procaspase-9 into the caspase known as caspase-9. The latter is an active enzyme that leads to the production of other caspases, with cell apoptosis as the eventual result.
Since a cell does not want to have apoptosis going on normally, the process must be tightly regulated. This is done (partly) by another pair of proteins, Bcl-2 and Bax. These two proteins have structural similarities and are considered to be in the same family, the Bcl-2 family. They are always present in the cytosol, and the relative concentration between Bcl-2 and Bax is what controls whether mitochondrial membrane channels will allow release of procaspase-9 and cytochrome c. If the ratio favors Bcl-2, the channels are essentially closed – the normal case – but if the ratio favors Bax, the channels open... and apoptosis may follow.
The present research measured the levels of certain proteins in 10 individuals before and after a marathon run. (The measurement was done indirectly by measuring levels of mRNA transcripts of the associated genes.) A key finding was that the ratio of Bcl-2 to Bax shifted in favor of Bcl-2 from the before to the after measurement. In other words, there was an anti-apoptotic effect, which countered the pro-apoptotic effects of ROS molecules produced by vigorous exercise. Although ROS levels were not measured (since there was no corresponding mRNA), levels of superoxide dismutase (SOD) antioxidants (Mn-SOD and Cu-Zn-SOD) increased after the marathons, reflecting ROS production.
Analysis of the results indicates that apoptosis actually was inhibited, though less in some experimental subjects than others. An increase in levels of procaspase-9 was not observed. Further, in 7 of the 10 experimental subjects, there was little evidence of DNA fragmentation (a consequence of apoptosis). In the other 3 subjects, there was some evidence of DNA fragmentation, but also smaller changes in the Bcl-2 to Bax ratios.
Most interestingly, there was a significant positive correlation in after marathon measurements between levels of Bcl-2 and both HSP70 and HSP32. This suggests that the expected increases of HSP70 and HSP32 may play some part in increased Bcl-2 levels. There was also a positive correlation post-marathon between HSP70 and Mn-SOD levels.
These findings, especially given the small sample size, certainly arent conclusive. But, as the paper says, "Here, we have found a significant relationship between HSP70 and bcl-2 RNA ... following marathon, but the underlying cellular and molecular mechanisms involved in this [sic] exercise induced adaptations in apoptosis and HSP70 are unknown and require further investigation."
Expression of the sirtuins SIRT1, SIRT3, and SIRT4 pre- and post-marathon were also measured. (Weve discussed the sirtuins on a number of occasions.) Theres an extensive history of research on SIRT1, concerning its connections with such things as cellular metabolism, cell survival under stress, and antioxidant activity. Research on other sirtuins like SIRT3 and SIRT4 is less extensive. However, members of this family have various things in common. All are enzymes. SIRT1 and SIRT3 are histone deacetylases (HDACs), so have epigenetic roles in affecting gene expression. SIRT3 and SIRT4 occur in mitochondria.
Although its possible to make various speculations about how sirtuins could be involved with apoptosis and metabolic consequences of exercise, not all that much is known about specific molecular mechanisms. Nevertheless, its interesting that the present research does show an effect of strenuous exercise on SIRT1, SIRT3, and SIRT4 expression. The paper notes that "the RNA contents of SIRT1 increased substantially in the group after marathon.... On the other hand, the RNA contents of SIRT3 and SIRT4 decreased in the group after marathon."
Further research into these connections could be very interesting.
Further reading:
Running a marathon halts cellular suicide (5/11/10)
Articles related to sirtuins:
Sirtuin proteins (11/16/07)
The discovery of sirtuins, part 1 (11/17/07)
The discovery of sirtuins, part 2 (11/20/07)
Sirtuin news (1/21/08)
SIRT1 and cancer (10/26/08)
Read More..
On the other hand, exercise necessarily increases a persons rate of metabolism, as food is processed to provide energy expended through exercise. An inevitable side-effect of metabolism is the production of reactive oxygen species (ROS) and "free radicals" that can damage DNA and other cellular constituents. This cellular damage can lead to either cancer or accelerated aging due to cell senescence and cell death.
The paradox, then, is that the health benefits of exercise do not seem to be canceled out by the side-effects of higher rates of metabolism. Its an important issue not just for humans who are trying to stay healthy, but even more important in animals like birds that may need to expend energy continuously over significant periods of time.
So whats going on here? Perhaps this research has some of the answer:
The effect of marathon on mRNA expression of anti-apoptotic and pro-apoptotic proteins and sirtuins family in male recreational long-distance runners
Background
A large body of evidence shows that a single bout of strenuous exercise induces oxidative stress in circulating human lymphocytes leading to lipid peroxidation, DNA damage, mitochondrial perturbations, and protein oxidation.
In our research, we investigated the effect of physical load on the extent of apoptosis in primary cells derived from blood samples of sixteen healthy amateur runners after marathon (a.m.).
Results
Blood samples were collected from ten healthy amateur runners peripheral blood mononuclear cells (PBMCs) were isolated from whole blood and bcl-2, bax, heat shock protein (HSP)70, Cu-Zn superoxide dismutase (SOD), Mn-SOD, inducible nitric oxide synthase (i-NOS), SIRT1, SIRT3 and SIRT4 (Sirtuins) RNA levels were determined by Northern Blot analysis. Strenuous physical load significantly increased HSP70, HSP32, Mn-SOD, Cu-Zn SOD, iNOS, GADD45, bcl-2, forkhead box O (FOXO3A) and SIRT1 expression after the marathon, while decreasing bax, SIRT3 and SIRT4 expression (P < 0.0001).
Conclusion
These data suggest that the physiological load imposed in amateur runners during marathon attenuates the extent of apoptosis and may interfere with sirtuin expression.
There are two main findings here, related to apoptosis and sirtuin expression. Lets take them in order.
Apoptosis is a form of programmed cell death that has several purposes. The invocation of a cells apopotosis program isnt necessarily an indication that something is wrong. For example, it occurs normally during embryonic development. Early in the development process embryos of all tetrapods have tissues between what will become the fingers and toes of their hands and feet. But since animals that have left an aquatic environment are usually better off without this extra tissue, evolution has led to signals at a certain stage of embryonic development that cause apoptosis in the cells of the relevant tissue. This is an example of whats known as the "extrinsic" apoptotic pathway.
But for our present purposes theres a second pathway – the "intrinsic" pathway – which is used whenever a cell either detects internal damage (usually to its DNA) or some stressful condition, such as an excessive level of reactive oxygen species. A ROS is a chemically-reactive molecule containing oxygen, including what are sometimes called "free radicals".
This condition of excess ROS is called oxidative stress. It can occur for various reasons, including exposure to high levels of heat or ultraviolet radiation – or abnormally rapid cell metabolism due to vigorous exercise. Cells recognize the condition of oxidative stress indirectly though signaling involving various other molecules that are produced in response to particular ROS molecules. Among such indicators are proteins called heat shock proteins. Two members of this family that were measured in the research under discussion were HSP70 and HSP32.
Signals of oxidative stress trigger the second, "intrinsic" apoptotic pathway, which involves a cells energy-producing organelles, the mitochondria. The main players in the intrinsic pathway are proteins called, generically, "caspases" – short for "cysteine-rich aspartate proteases". Caspases are enzymes that cleave proteins at aspartate units. (Cysteine and aspartate are two of the 21 amino acids that normally make up proteins.)
Caspases are fairly active enzymes, so they dont ordinarily occur at significant concentrations within cells. Instead, they are produced when needed from other protein enzymes called procaspases. One of these, procaspase-9 is found normally within mitochondria, along with another protein, cytochrome c. Most of the time these proteins are confined within the mitochondria. However, under certain conditions some channels in a mitochondrions membrane can open and allow the release of procaspase-9 and cytochrome c. Once these proteins enter the cytosol (cell fluid) outside a mitochondrion, they can team up with another protein (Apaf-1: "apoptotic protease activating factor 1") to convert the procaspase-9 into the caspase known as caspase-9. The latter is an active enzyme that leads to the production of other caspases, with cell apoptosis as the eventual result.
Since a cell does not want to have apoptosis going on normally, the process must be tightly regulated. This is done (partly) by another pair of proteins, Bcl-2 and Bax. These two proteins have structural similarities and are considered to be in the same family, the Bcl-2 family. They are always present in the cytosol, and the relative concentration between Bcl-2 and Bax is what controls whether mitochondrial membrane channels will allow release of procaspase-9 and cytochrome c. If the ratio favors Bcl-2, the channels are essentially closed – the normal case – but if the ratio favors Bax, the channels open... and apoptosis may follow.
The present research measured the levels of certain proteins in 10 individuals before and after a marathon run. (The measurement was done indirectly by measuring levels of mRNA transcripts of the associated genes.) A key finding was that the ratio of Bcl-2 to Bax shifted in favor of Bcl-2 from the before to the after measurement. In other words, there was an anti-apoptotic effect, which countered the pro-apoptotic effects of ROS molecules produced by vigorous exercise. Although ROS levels were not measured (since there was no corresponding mRNA), levels of superoxide dismutase (SOD) antioxidants (Mn-SOD and Cu-Zn-SOD) increased after the marathons, reflecting ROS production.
Analysis of the results indicates that apoptosis actually was inhibited, though less in some experimental subjects than others. An increase in levels of procaspase-9 was not observed. Further, in 7 of the 10 experimental subjects, there was little evidence of DNA fragmentation (a consequence of apoptosis). In the other 3 subjects, there was some evidence of DNA fragmentation, but also smaller changes in the Bcl-2 to Bax ratios.
Most interestingly, there was a significant positive correlation in after marathon measurements between levels of Bcl-2 and both HSP70 and HSP32. This suggests that the expected increases of HSP70 and HSP32 may play some part in increased Bcl-2 levels. There was also a positive correlation post-marathon between HSP70 and Mn-SOD levels.
These findings, especially given the small sample size, certainly arent conclusive. But, as the paper says, "Here, we have found a significant relationship between HSP70 and bcl-2 RNA ... following marathon, but the underlying cellular and molecular mechanisms involved in this [sic] exercise induced adaptations in apoptosis and HSP70 are unknown and require further investigation."
Expression of the sirtuins SIRT1, SIRT3, and SIRT4 pre- and post-marathon were also measured. (Weve discussed the sirtuins on a number of occasions.) Theres an extensive history of research on SIRT1, concerning its connections with such things as cellular metabolism, cell survival under stress, and antioxidant activity. Research on other sirtuins like SIRT3 and SIRT4 is less extensive. However, members of this family have various things in common. All are enzymes. SIRT1 and SIRT3 are histone deacetylases (HDACs), so have epigenetic roles in affecting gene expression. SIRT3 and SIRT4 occur in mitochondria.
Although its possible to make various speculations about how sirtuins could be involved with apoptosis and metabolic consequences of exercise, not all that much is known about specific molecular mechanisms. Nevertheless, its interesting that the present research does show an effect of strenuous exercise on SIRT1, SIRT3, and SIRT4 expression. The paper notes that "the RNA contents of SIRT1 increased substantially in the group after marathon.... On the other hand, the RNA contents of SIRT3 and SIRT4 decreased in the group after marathon."
Further research into these connections could be very interesting.
 | Marfe, G., Tafani, M., Pucci, B., Di Stefano, C., Indelicato, M., Andreoli, A., Russo, M., Sinibaldi-Salimei, P., & Manzi, V. (2010). The effect of marathon on mRNA expression of anti-apoptotic and pro-apoptotic proteins and sirtuins family in male recreational long-distance runners BMC Physiology, 10 (1) DOI: 10.1186/1472-6793-10-7 |
Further reading:
Running a marathon halts cellular suicide (5/11/10)
Articles related to sirtuins:
Sirtuin proteins (11/16/07)
The discovery of sirtuins, part 1 (11/17/07)
The discovery of sirtuins, part 2 (11/20/07)
Sirtuin news (1/21/08)
SIRT1 and cancer (10/26/08)
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