The epidermis is the tough outer layer that acts as the first line of defense against the external environment. It is composed of stratified squamous epithelial cells that further break down into four to five layers. From superficial to deep, the primary layers are the stratum corneum, stratum granulosum, stratum spinosum, and stratum basale. In the palms and soles, where the skin is thicker, there is an additional layer of skin between the stratum corneum and stratum granulosum called the stratum lucidum. The epidermis regenerates from stem cells located in the basal layer that grow up towards the corneum. The epidermis itself is devoid of blood supply and derives its nutrition from the underlying dermis.
Sudoriferous glands, also known as sweat glands, are further divided into eccrine and apocrine glands. Eccrine glands are distributed throughout the body and primarily produce serous fluid to regulate body temperature.[5] Apocrine glands are present in the axilla and pubic area and produce milky protein-rich sweat.[5] These glands are responsible for odor as bacteria break down the secreted organic substances.
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Mitochondria are highly dynamic [8]. In the cell, they form a tubular network that constantly changes by division and fusion (Additional file 1). Both processes are accomplished by multi-component molecular machineries that include a number of dynamin-related GTPases [9, 10]. When mitochondria are isolated from cells, the network breaks up into fragments that spontaneously reseal. Isolated mitochondria are fully competent for respiration and ATP synthesis [11]. They maintain their membrane composition, organization and membrane potential, as well as the ability to fuse [12] and to import proteins [7]. We owe much of what we know about mitochondria and how they work at the molecular level to in vitro studies with isolated mitochondria, or even mitochondrial membrane fractions, which still carry out oxidative phosphorylation and ATP synthesis [13].
And finally, how exactly are mitochondria implicated in ageing? Why do some cells and organisms live only for days, while others have lifespans of years or decades? Is this genetically programmed or simply a consequence of different levels of oxidative damage? How is this damage prevented or controlled, and how does it affect the function of mitochondrial complexes? Is the breakdown of ATP synthase dimers also an effect of oxidative damage, and is it a cause of ageing?
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Myeloma cells make a substance that tells the osteoclasts to speed up dissolving the bone. So old bone is broken down without new bone to replace it, making the bones weak and easy to break. Fractured bones are a major problem in people with myeloma. This increase in bone break-down can also raise calcium levels in the blood. Problems caused by high calcium levels are discussed in Signs and Symptoms of Multiple Myeloma.
Genetic mutations have been linked to disorders known as the progressive myoclonic epilepsies, which are characterized by ultra-quick muscle contractions (myoclonus) and seizures over time. For example, Lafora disease, a severe, progressive form of myoclonic epilepsy that begins in childhood, has been linked to a gene that helps to break down carbohydrates in brain cells.
Most side effects of antiseizure drugs are relatively minor, such as fatigue, dizziness, or weight gain. Antiseizure medications have differing effects on mood: some may worsen depression, where others may improve depression or stabilize mood. However, severe and life-threatening reactions such as allergic reactions or damage to the liver or bone marrow can occur. Antiseizure medications can interact with many other drugs in potentially harmful ways. Some antiseizure drugs can cause the liver to speed the metabolism of other drugs and make the other drugs less effective, as may be the case with oral contraceptives. Since people can become more sensitive to medications as they age, blood levels of medication may need to be checked occasionally to see if dosage adjustments are necessary. The effectiveness of a medication can diminish over time, which can increase the risk of seizures. Some citrus fruit and products, in particular grapefruit juice, may interfere with the breakdown of many drugs, including antiseizure medications, causing them to build up in the body, which can worsen side effects.
Dietary approaches and other treatments may be more appropriate depending on the age of the individual and the type of epilepsy. A high-fat, very low carbohydrate ketogenic diet is often used to treat medication-resistant epilepsies. The diet induces a state known as ketosis, which means that the body shifts to breaking down fats instead of carbohydrates to survive. A ketogenic diet effectively reduces seizures for some people, especially children with certain forms of epilepsy. Studies have shown that more than 50 percent of people who try the ketogenic diet have a greater than 50 percent improvement in seizure control and 10 percent experience seizure freedom. Some children are able to discontinue the ketogenic diet after several years and remain seizure-free, but this is done with strict supervision and monitoring by a physician.
Developed more than 30 years ago, levodopa is often regarded as the gold standard of Parkinson's therapy. Levodopa works by crossing the blood-brain barrier, the elaborate meshwork of fine blood vessels and cells that filter blood reaching the brain, where it is converted into dopamine. Since blood enzymes (called AADCs) break down most of the levodopa before it reaches the brain, levodopa is now combined with an enzyme inhibitor called carbidopa. The addition of carbidopa prevents levodopa from being metabolized in the gastroinstenal tract, liver and other tissues, allowing more of it to reach the brain. Therefore, a smaller dose of levodopa is needed to treat symptoms. This advance also helps reduce the severe nausea and vomiting often experienced as a side effect of levodopa. For most patients, levodopa reduces the symptoms of slowness, stiffness and tremor. It is especially effective for patients that have a loss of spontaneous movement and muscle rigidity. This medication, however, does not stop or slow the progression of the disease.
This medication slows down the activity of the enzyme monoamine oxidase B (MAO-B), the enzyme that metabolizes dopamine in the brain, delaying the breakdown of naturally occurring dopamine and dopamine formed from levodopa. When taken in conjunction with levodopa, selegiline may enhance and prolong the effectiveness of levodopa.
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Slow cell phone download speeds can be frustrating, and they can all but wreck the functionality of your mobile device. Find out more about why speeds matter, what slows them down and how you might fix the problems below.
One of the most common culprits of slow data on your phone can be your cell signal. A weak signal, regardless of the cause, can slow your data transfers. A poor connection often means that your phone has to continuously send and resend data because the connection keeps interrupting the transfer. When this happens, uploads and downloads end up taking longer than they should.
Prometaphase: In this stage the nuclear envelope breaks down so there is no longer a recognizable nucleus. Some mitotic spindle fibers elongate from the centrosomes and attach to kinetochores, protein bundles at the centromere region on the chromosomes where sister chromatids are joined. Other spindle fibers elongate but instead of attaching to chromosomes, overlap each other at the cell center.
Cytokinesis: The spindle fibers not attached to chromosomes begin breaking down until only that portion of overlap is left. It is in this region that a contractile ring cleaves the cell into two daughter cells. Microtubules then reorganize into a new cytoskeleton for the return to interphase.
We are currently at the tail end of the 4th generation of mobile data technology. The first 4G networks began to come online in 2011, but carriers did not achieve full 4G coverage until 2014. 4G networks are based on all-Internet Protocol (IP) network to achieve up to 1GB download speeds. This network has essentially the same core protocols as the internet.
It would take roughly 40 minutes on 4G to download two full seasons of The Office, which is 5GB in size. It would take over 2 hours to download on 3G. 5G reduces the time it would take to 35 seconds. 4G boasts peak speeds clocking in at 150Mbps upload and 50Mbps download speeds. These are vast improvements over 3G, yet the full promise of 4G has never been realized.
Prophase is the first stage of division. The nuclear envelope is broken down in this stage, long strands of chromatin condense to form shorter more visible strands called chromosomes, the nucleolus disappears, and microtubules attach to the chromosomes at the disc-shaped kinetochores present in the centromere.[20] Microtubules associated with the alignment and separation of chromosomes are referred to as the spindle and spindle fibers. Chromosomes will also be visible under a microscope and will be connected at the centromere. During this condensation and alignment period in meiosis, the homologous chromosomes undergo a break in their double-stranded DNA at the same locations, followed by a recombination of the now fragmented parental DNA strands into non-parental combinations, known as crossing over.[21] This process is evidenced to be caused in a large part by the highly conserved Spo11 protein through a mechanism similar to that seen with toposomerase in DNA replication and transcription.[22] 2ff7e9595c
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