Monday, October 29, 2012

The Components of the Blood and the Immune System

We all have a general idea of what blood is. The heart pumps it through our body, and we need it to live. It is used to swear eternal friendship. We use it to save lives. If we are sick, the doctor can test our blood to find out what is wrong. But how can the blood reflect how we are sick, and why is it so essential to life? In the following article, I will give an overview of the blood components and their function.

What are the components of blood?

Your blood makes up about 7% of your body weight, and in an adult amounts to around 5 liters (= 1.3 gallons) (1). If you lose too much blood, for instance during a trauma or an accident, it can be life-threatening, and you may need a blood transfusion. We are able to donate up to half a liter, which is about 10% of our total blood volume, however such blood donation requires overall good health, and time to rest and recover afterwards. Roughly half of the blood volume consists of various blood cells, while the other half is blood plasma, the liquid which enables your blood to flow throughout your body. Every component in the blood has their own critical function, which will be introduced in this article.

The blood plasma consists of approximately 90 % water (1)

Water is critical for life. A human can survive for days and even weeks without food, but only a few days without water. The reason is that water is a resource that constantly recycles. We lose water from our body both through urine and as evaporation from our skin through sweat. Neither of these processes are something we can consciously control, but they are important processes for temperature control as well as getting rid of waste products. On the other hand, our water intake is under our control. We get water from what we drink, but also through food. Mild dehydration may lead to headache, overheating, or dizziness, but is not life-threatening under normal circumstances. In cases of extreme dehydration, you can get liquid through intravenous transfusions directly into your blood.

The blood plasma contains various soluble components

In addition to giving blood its fluidity, so that blood cells can be transported throughout the body, water is also important as a solvent for transport of nutrients and waste products. Minerals, vitamins, glucose, and various types of proteins, along with the water, make up the blood plasma. Although the color of the blood is red, the color of the blood plasma is actually yellow. The red color comes from the large amount of red bloods cells, as will be described below. The yellow color of the blood plasma comes from the various water-soluble components, such as nutrients and various signaling molecules. Furthermore, your blood is the carrier of various waste products, that are filtered out from the blood to the urine through the kidneys. In addition, the blood contains various proteins that have both structural as well as regulating or signaling roles. One type of important structural proteins are the coagulation factors that are required for proper blood clotting. Insulin is an example of signaling molecule. People suffering from diabetes must closely monitor and adjust the glucose and insulin levels in their blood, to ensure a proper balance.

The cells in our blood

The cells in our blood are divided into two main types: The red blood cells, and the white blood cells. In addition, there are specialized cell fragments, called platelets, that are derived from a specific type of white blood cells, the megakaryocytes. The red blood cells (RBC, also called erythrocytes) take up about 45% of the total blood volume (1). The red color is due to abundant amounts of the protein hemoglobin, which binds and transports oxygen from the lungs throughout our body. The white blood cells are critical for our immune system, which can broadly be divided into the innate and the adaptive immune system. The innate immune system recognizes patterns that are associated with pathogens, and mounts a fast reaction towards infections. The adaptive immune cells recognize specific eptiopes, and can be educated to recognize epitopes associated with disease. The response of adaptive immune cells are initially slower, but the education leads to a "memory" so that upon later encounters, we can quickly recognize and eliminate the threat. Immunization is based on the ability of the adaptive immune system to recognize the pathogen and develop a protective "memory" or immunization. Lastly, the platelets, also called thrombocytes, are not cells, but rather cell fragments. They are critical for blood coagulation, to ensure that upon a cut or damage to a blood vessel, the bleeding will stop.

Auto Refractometers

Discover a new range of constructive refractometers, in the marketplace named auto refractometers widely used as an ophthalmic diagnostic product allowing a more natural measurement. An auto refractor or automated refractor is a computer-controlled machine used during an eye examination to provide an objective measurement of a person's refractive error and prescription for glasses or contact lenses. This is achieved by measuring how light is changed as it enters a person's eye. In some offices this process is used to provide the starting point for the optometrist in subjective refraction tests.

Automated refraction is particularly useful when dealing with non-communicative people such as young children or those with disabilities. It can measure small pupils down to 2 mm in diameter. Pupils of patient all over the world can be measured easily. The ideal refractive measurement can be achieved since the far point is measured while the person is looking at the target in distance.

The Auto Refractometers uses the fogging system for the relaxation of accommodation. It tends to allow instrumental myopia for the person who doesn't accommodate well. This is because the patient is looking at the inside target unnaturally. The Auto Refractometer takes away this weak point by using the open view window. It allows a more natural measurement and satisfactory analysis of the patient's vision. Additionally, a reliable objective refraction measurement is achievable since the far point is measured while the person is looking at the target in distance.

The Auto Refractometers Refractometer is a precision ophthalmic instrument. It can be used to measure the parameters of farsightedness, nearsightedness, astigmatism, axis and pupil-distance for prescription of vision correction. Some key features of the auto refractometer are -

• New color LCD screen 
• Easy to use,convenient to measure 
• More broad measurement range of Min 
• Pupil size to suit the people all over the world

Auto refractometers is acknowledged for its sturdy construction, long lasting performance and precise dimension.

The integrated Auto-Start function automatically starts the measurement as soon as the correct measuring position has been detected. The measurement results are immediately displayed on the large-size color monitor. The monitor can be tilted in three positions to ensure that you can work expediently either standing or sitting. For documentation purposes the measurement results can be optionally printed via the installed printer or output via an interface. The printer also features an automatic cutter which cuts off the printout as soon as printing has been completed. The paper can therefore be removed easily without having to tear it off.

Proven Features

> Quick Measuring Process 
> Active Accommodation Relaxation 
> IOL Measuring Mode 
> Reliable PD Measurement 
> Convenient Adjustable Chin Rest 
> Large Cylinder Measuring Range up to 10 DPT. 
> Measurement as From 2.3 Mm Pupil Diameter.

National Microscope Exchange has been in business since 1991, selling and servicing refractometers, microscopes and inverted microscope. The service staff has 30 years of experience with microscopes, and is the authorized United States service facility for Atago refractometers.

Gene Assembly: DNA Sequencing of Gene-Sized Fragments Using Primer Walking

Next Generation (Next-Gen) sequencing is a new form of technology capable of determining the sequence of DNA the size of a bacterial genome. Despite this capacity to sequence millions of bases, Next-Gen technology is not always efficient or cost effective. Sequencing smaller fragments of DNA is an example of this. Sometimes researchers prefer to sequence a single gene to determine function or fill in gaps left by the more advanced technologies. Primer walking is a common practice still employed for sequencing smaller regions of DNA. Capillary sequencers have improved the capability of sequencing DNA with faster times and longer base read lengths. However, the basic process of primer walking and gene assembly remains the same.

Isolating the DNA Fragment

The first step in sequencing a selected DNA fragment is to isolate the fragment from genomic DNA. Isolation is often performed by amplifying copies of the chosen region using PCR (Polymerase Chain Reaction). PCR produces copies of (amplifies) a region of DNA determined by smaller single stranded oligonucleotides called primers. The primers anneal to the start point on the forward strand and the start point on the reverse strand as amplification proceeds in both directions. Amplification by PCR produces millions of copies of a given region of DNA. However, it requires knowledge of the sequence before and after the region in order to select primers for amplification.

Researchers sometimes choose to sequence the DNA fragment (PCR product) directly. However, many researchers prefer cloning using a bacterial plasmid as an alternative.

Amplifying the DNA Fragment in a Bacterial Plasmid

Once the selected DNA has been amplified by PCR, it is inserted into a bacterial plasmid. The plasmid is a circular DNA molecule with known sequence. The circular DNA is broken with restriction enzymes allowing the unknown DNA fragment to be inserted. Most commercial plasmids contain universal sights from which researchers can select universal primers to sequence the inserted DNA in the forward and reverse directions. Capillary sequencers typically generate 800 to 900 bases for each primer for a single set of sequencing reactions yielding 1600 to 1800 total bases of data. This may cover the entire insert for smaller DNA fragments. However, genes are generally over 5,000 bases. Therefore, one set of sequence results would not complete the sequencing of the entire fragment of DNA.

Sequence Results Provide Templates for Primers

Gene assembly and primer walking involve using known sequence to select primers for additional sequence data. Using a result generated from a universal primer provides the sequence template for designing the next primer. The primer will likely be selected around the 700 base region for a result with 800 bases of quality sequence. The remaining 100 bases will allow overlap with the new generated sequence. Primer walking continues until the forward sequence results intersect with the reverse sequence results. A 5,000 base insert would likely need 5 to 8 results to achieve overlap between the forward and reverse directions. Researchers may sequence both the forward and reverse strands completely to provide the entire sequence of the double stranded molecule to confirm the accuracy of all the bases.

Software Assembles the Sequence Results

There are commercial software programs designed to assemble sequence results in the order of their overlapping regions resulting in a consensus sequence. Many of these programs use chromatogram data that allows base peak calls to be reviewed and corrected if necessary. The chromatogram is a view of the actual data showing the quality of peaks generated during electrophoresis. Some programs simply use the text of the base calls, but this does not allow as detailed a review of the results.

What Are Stem Cells?

Stem cells are unique because they combine two key properties: Pluripotency and self-renewal. Pluripotency means that they can differentiate and give rise to multiple different cell types. In addition, they have the ability to divide and self-renew to maintain the original population.

There are two principally different types of stem cells: Embryonic stem (ES) cells and adult stem cells (or tissue-specific stem cells). In addition, induced pluripotent stem (iPS) cells are very similar to ES cells, and are the focus of intense ongoing research and development.

Embryonic stem cells (ES cells or ESC) arise from the fertilization of an egg by a sperm. The first few rounds of division this fertilized egg undergoes create both the extra-embryonic tissue as well as a pool of identical ESC that eventually will give rise to the new individual. The unique ability of ESC to give rise to absolutely all cell types in the body has lead to increased interest in these cells for both basic and medical research. Such research can improve our understanding of normal development and genetic diseases, and also has a potential for development of tissue regeneration therapy. However, there is also controversy in regards to ethical issues when it comes to the use of human ESC.

Researchers have developed a method where mature differentiated cells can be reprogrammed to become immature pluripotent cells, named induced pluripotent stem cells (iPS cells or iPSC). These iPSC are found to be very similar to primary ESC, but are not identical. These cells provide an alternative source of pluripotent cells. iPSC and ESC therefore remain the focus of intense research, both to understand the mechanisms of pluripotency and to improve the method of reprogramming to create iPSC.

The 2012 Nobel Prize in Physiology or Medicine was awarded to Sir John B. Gordon and Dr. Shinya Yamanaka for "the discovery that mature cells can be reprogrammed to become pluripotent" (source: ), further emphasizing the importance of research on reprogramming and induced pluripotency.

Adult stem cells are also referred to as tissue specific stem cells and can give rise to all cell types within a specific tissue. One example is the hematopoietic stem cell (HSC). In adults, most HSC are found in the bone marrow (BM), but can be immobilized into the blood stream for instance for the purpose of HSC transplantation for treatment of leukemia. HSC are pluripotent and give rise to red blood cells, platelets, and all white blood cells required in the immune system. These stem cells alternate between a quiescent (non-dividing, resting) and a proliferative state (undergoing cell divisions), and provide a life-long source of all blood and immune cells for the individual.

The self-renewal property is crucial for life-long replenishment of the downstream cell types. Exhaustion (or defective self-renewal) of stem cells will lead to disease. For instance, an exhaustion of the HSC, which give rise to all blood cells, will lead to anemia and immunodeficiency. Anemia is the reduction of red blood cells that are crucial for oxygen transport. Immunodeficiency is a defect in any immune cell that is required to protect your body against infection, damage and cancer.

However, the property of self-renewal is also potentially dangerous, as uncontrolled self-renewal is a key feature of cancer cells. Thus, in healthy stem cells, as well as other diving cells, self-renewal is tightly regulated. A critical combination of mutations can lead to loss of this regulation and give rise to cancer. Control of self-renewal is also a major concern and challenge that scientists face in regards to the potential use of ESC or iPSC for tissue regeneration therapy.

One Person, Twelve Bodies

It is obvious that all human beings go through various cycles during their life, progressing from infant to child to adolescent to adult to senior citizen. Each of these stages builds upon previous biology and experience while evolving from one to the next. The concept that the body changes form as it ages has been around ever since early man sat around campfires and compared grandfather to a newborn baby boy. It is obvious change occurs, but no one knew how or why. They did know, even back then, that if that baby boy got fed regularly and stayed out of the mouth of large animals, chances were good that he would someday look like grandfather. Still, it was hard for early man to grasp the idea, and make much sense out of the fact that grandfather was once a tiny baby himself, and that he occupied all the various body shapes and ages in between the two extremes. That was one of life's mysteries that they just blindly accepted.

So the process of aging was known, early on, to involve noticeable and significant changes in body shape and size, hair color, skin texture, strength, weight, stamina, agility, appetite, thinking ability, hearing, vision, sleeping patterns, communication, and perhaps most notably, wellness. As the baby boy grew into adolescence, and then into manhood, and then into middle age, he no doubt suffered the "slings and arrows of outrageous fortune" as Shakespeare might have described it. Perhaps he wore a few scars to prove his more stressful experiences; and most assuredly, he probably grew to know many aches and pains, loss of energy, sickness and disease, weight fluctuations, and all the other curses and afflictions that accompany growing old.

During Shakespeare's time, the average life expectancy was a mere 35 to 40 years, and people thought the body entered a new "age" roughly every five or so years. According to Shakespeare's estimation, a person only had seven bodies. He wrote about this observation in his play, As You Like It, saying that "... man in his time plays many parts, His acts being seven ages."

The concept of seven-year body change cycles has been found in many sources including the Torah, Buddhist lore, Native American tradition, the New Testament, American folk wisdom, the philosophy of the Greek mathematician Pythagoras, traditional Chinese medicine, and the phases of the moon that change every seventh day, which influence women's reproductive rhythms and hormonal pulses.The seven-year body change cycle has its deepest roots in traditional Chinese medicine dating back to 1500 BC, which claims that natural and normal health changes occur at regular seven-year intervals in women and eight-year intervals in men. The two most significant changes in women's bodies occur at around 14 years, when menstruation begins, and around 49 years, when menstruation becomes less frequent and eventually ceases altogether. It is thought in this medical tradition as women age, much of their vital essence and nutrients are lost in their monthly periods and this transforms them eventually into old, stooped grandmothers. The consensus of understanding today, from all these various opinions, is that every seven years individuals grow a new body, but unfortunately; it is not nearly that routine, nor is it accurate.

Recent research reveals that this popular folk notion is not exactly true because, although most cells in the body do, in fact, reproduce and replace dying cells during the aging process, not all cells do. Certain cells replace themselves many times over during a seven-year period, while some cells never change at all. The truth is that different cells have different life spans and rates of regeneration, depending on the kind of tissue or fluid in which they are located. For example, white blood cells have the shortest life expectancy and only last several days, while neurons in the cerebral cortex of the brain are never replaced. Yes, there are no new neurons added to the brain after birth, and any that die during a person's life time are never replaced. Think about that next time you go out drinking. Every time you get intoxicated, you destroy irreplaceable brain cells!

Adults produce their body weight in red blood cells, white cells, and platelets every seven years, but the cells in the stomach lining only last five days. Liver cells regenerate in four to six weeks, but it takes two full years for all the cells of the liver to turnover. Tooth enamel is one of the hardest tissues in the body, and the cells that form permanent teeth, that replace the milk teeth, often last an individual their entire life. Similarly, fat cells are replaced in adults at the average rate of about ten percent each year, or in other words, humans replace all their fat cells roughly every decade.

Cardiomyocyte heart cells, on the other hand, are replaced in the body at a gradually reduced rate as a person ages. Around age 25, for example, about one percent of these cells are replaced annually. Replacement gradually slows to only about 0.5% at age 70. Even in people with much longer life spans, less than half of the cardiomyocyte cells are usually ever replaced by the body, and those that are not, have been in most people since their birth. In the heart, the cardiomyocyte cells comprise the heart muscle, but the heart is also made up of other connective tissues and other cell types that do indeed grow in size, even though some are never replaced.

Scientists from all around the world are currently studying all the major tissues and fluids of the body to determine turnover rates and the aging process as a whole. While it is obvious that skulls and brains and hearts grow larger after birth, how can it be that certain cells do not reproduce? Where then does all that extra mass come from? In the brain, even though no new neurons are replaced in the cerebral cortex as previously stated, research is still ongoing on other parts of the brain as well. It appears there are lots of other kinds of cells that do get added such as glial cells, which may possibly make up about 90% of the cells in the brain, and lest we forget, the brain is composed 78% of water.

Human hair typically grows at a rate of about half an inch per month consistently across the scalp, depending on diet, age, race, gender, and general health. Human hair goes through three stages of growth. The first stage is the anagen phase, where the hair is actively growing for a period of two to six years. During this phase, cells in the hair follicle actively divide, pushing the hair up and out of the skin layer on the scalp. The next phase is the catagen phase in which the rate of growth stops because the follicle grows dormant. The final stage is the telogen phase where the hair falls out to make way for new hair growth. Human hair has a "terminal length" which is the maximum length a hair will grow, and it varies according to the individual. Some people have a terminal length of only a few inches while other individuals may grow their hair several feet long before the hair follicle eventually dies. The average human head has roughly 150,000 single hairs on it and most hairs are in different stages of growth. If a person were to shave their head completely bald and then grow it back in one event, it would take anywhere from a few months to several years depending on their health and the personal characteristics mentioned here.

The most dramatic physical changes to the human body occur within the first two seven-year body cycles. The skeletal system takes, on average, ten years to renew as bone-dissolving and bone-rebuilding cells work in concert to constantly remodel itself over a typical life span. Bones are the primary structural component of a human body and determine the individual's stature. Generally, girls usually grow until a bone age of about 14 years and boys stop growing after a bone age of around 16 years, depending on when they reach puberty. Children grow at a rate of about 2 to 2 ½ inches per year in early childhood up until they begin puberty, at which time their growth will slow to about 1 ½ inches annually. As they reach their peak growth velocity in puberty, there is acceleration in growth to about 3 to 3 ½ inches per year for girls and 4 inches per year for boys. Growth slows down again after puberty to about 2 ½ to 3 inches per year in girls following menarche (the first period) until they reach their adult height. Girls often reach their growth spurt at puberty about two years earlier than boys, which explains why girls are often taller than boys during early adolescence.

Skin is the largest organ on the body and has the ability to constantly regenerate itself. Human skin consists of primarily two main layers: the epidermis, or surface layer, and the dermis, or deeper layer. There are several other smaller layers of skin located within these two main sections. These include the basal and the stratum spinosum layers of the epidermis, which are mostly responsible for skin regeneration. New skin cells are born all the time and rise into the epidermal layer as old skin cells die and fall away on the surface. Young skin regenerates its epidermal surface area about every two to three weeks. As a person ages, the cell turnover rate slows down, but never completely stops. Direct sunlight is a major reason for this slowdown due to several factors. The skin is comprised of collagen, which gives the skin elasticity. Sunlight lessens collagen production which makes the skin thinner and less resilient. This causes skin cells to become disorganized and malformed and ages the skin to eventually form wrinkles and spots.

The regeneration process, unfortunately, doesn't continue forever, nor always works efficiently, because it is influenced by individual lifestyle habits, choices, environmental factors, and behaviors; which all impact cell renewal. Poor lifestyle choices, harsh living conditions, along with heredity, lack of exercise, and improper diet can develop into chronic conditions such as heart disease, diabetes, high cholesterol, high blood pressure, liver disease, and even numerous forms of cancer.

Organs, tissues, and systems of the body are designed by nature to serve a specific purpose, and when not treated properly, they develop disease and dysfunction which impacts the body's homeostasis or metabolic balance and cell regeneration. The liver, for example, the second largest organ in the body, performs many critical functions such as producing immune agents to fight infection; it neutralizes toxins in the blood, and filters out germs and bacteria from the bloodstream. The liver also makes proteins that regulate blood clotting, produces bile to help absorb fats, and stores glucose for when the body requires energy. No one can live long, or well, without proper liver function because it is the metabolic factory of the entire body.

So with all this diversity in tissues and fluids within the human body, and all the corresponding differences in cell regeneration rates, not to mention all the numerous individual differences in the aging process due to influences from heredity, metabolism, digestion, personality, intelligence, sleep, diet, minerals, allergies, exercise, gender, race, disease, injuries, relationships, emotions, medical care, neighborhoods, weather conditions, and immune system function, in general. How would it ever be possible to conclude that the body changes completely every seven years? There are just too many variables and influences affecting a human body to be able to chop it up into nice, crisp intervals like this. It is just not that easy.

There is no disputing the fact that an infant baby transforms into an old man or woman over the course of a life time. However, rather than look at the normal human life span as one big continuum from birth to death, or divided into decade-long intervals, it is much more interesting, and more understandable, to view it as if it were composed of twelve individual and distinct body changes, each spanning seven years. This folk-notion viewpoint is a very useful tool and just makes better sense for understanding the human metamorphosis, even though it may not be 100 percent accurate. I prefer, and advocate, the seven year cycles because they provide more milestones and age groupings which can be viewed, and studied, as distinct separate bodies.