Biosolutions

Endotracheal intubation for artificial ventilation

2012-05-21T12:27:00.006+05:30

Digestion Process Animation

2012-05-20T03:49:00.000+05:30

Effects of Alzheimer's Disease

2012-05-20T03:37:00.000+05:30

A Healthy Brain The healthy brain is made up of millions of interconnecting nerve cells, called neurons. Neurons constantly communicate with each other by sending signals through tentacle-like connections called axons and dendrites. How Alzheimer's Disease Affects the Brain The brain of a patient with Alzheimer's disease is much different. The orderly, organized arrangement of nerve cells found in a healthy brain become entangled, full of senile plaques and neurofibrillary tangles. The plaques and tangles interfere with the normal activity between neurons in the area of the brain responsible for intellectual thought. Symptoms of Alzheimer's Disease Alzheimer's disease affects people in different ways. The disease is slowly progressive from onset. Memory loss, confusion, disorientation, and poor judgment are a few of the symptoms of Alzheimer's disease.

Migraine Pathophysiology

2012-05-20T03:16:00.000+05:30

Migraines are believed to be a neurovascular disorder.The phenomenon known as cortical spreading depression, which is associated with the aura of migraine, has been theorized as a possible cause of migraines. In cortical spreading depression, neurological activity is initially activated, then depressed over an area of the cerebral cortex. This situation has been suggested to result in the release of inflammatory mediators leading to irritation of cranial nerve roots, most particularly the trigeminal nerve, which conveys the sensory information for the face and much of the head. This theory is, however, speculative, without any supporting evidence, and there are indeed cogent arguments against it. First, only about one third of migraineurs experience an aura, and those who do not experience aura do not have cortical spreading depression.[citation needed] Second, many migraineurs have a prodrome (see above), which occurs up to three days before the aura.

Eukaryotic transcription

2012-05-18T03:05:00.000+05:30

Eukaryotic transcription is more complex than prokaryotic transcription. For instance, in eukaryotes the genetic material (DNA), and therefore transcription, is primarily localized to the nucleus, where it is separated from the cytoplasm (in which translation occurs) by the nuclear membrane. DNA is also present in mitochondria in the cytoplasm and mitochondria utilize a specialized RNA polymerase for transcription. This allows for the temporal regulation of gene expression through the sequestration of the RNA in the nucleus, and allows for selective transport of RNAs to the cytoplasm, where the ribosomes reside.

The basal eukaryotic transcription complex includes the RNA polymerase and additional proteins that are necessary for correct initiation and elongation.

Subscribe in a reader

Initiation

Among eukaryotes that regulate the transcription of individual genes, the core promoter of protein-encoding gene contains binding sites for the basal transcription complex and RNA polymerase II, and is normally within about 50 bases upstream of the transcription initiation site. Further transcriptional regulation is provided by upstream control elements (UCEs), usually present within about 200 bases upstream of the initiation site. The core promoter for Pol II sometimes contains a TATA box, the highly conserved DNA recognition sequence for the TATA box binding protein, TBP, whose binding initiates transcription complex assembly at the promoter.

Some genes also have enhancer elements that can be thousands of bases upstream or downstream of the transcription initiation site. Combinations of these upstream control elements and enhancers regulate and amplify the formation of the basal transcription complex.

Transcription process Eukaryotes have three nuclear RNA polymerases, each with distinct roles and properties:

Name	Location	RNA transcribed
RNA Polymerase I (Pol I, Pol A)	nucleolus	Larger ribosomal RNA (rRNA) (28S, 18S, 5.8S)
RNA Polymerase II (Pol II, Pol B)	nucleus	messenger RNA (mRNA) and most small nuclear RNAs (snRNAs)
RNA Polymerase III (Pol III, Pol C)	nucleus (and possibly the nucleolus-nucleoplasm interface)	transfer RNA (tRNA) and other small RNAs (including the small 5S rRNA)

Transcription regulation The regulation of gene expression is achieved through the interaction of several levels of control including the regulation of transcription initiation. Most (not all) eukaryotes possess robust methods of regulating transcription initiation on a gene-by-gene basis. The transcription of a gene can be regulated by cis-acting elements within the regulatory regions of the DNA, and trans-acting factors that include transcription factors and the basal transcription complex. Splicing Two types of splicing, cis-splicing and trans-splicing, use the same splicing machinery to cleave RNAs at specific points and rejoin them to form new combinations once transcribed. Although most eukaryotes possess splicing machinery the extent of cis- and trans-splicing varies from organism to organism. Cis-splicing

Primary (initial) mRNA transcripts are synthesized as larger precursor RNAs that are processed by splicing out introns (non-coding sequences) and ligating exons (non-contiguous coding sequences) into the mature mRNA. Primary transcripts for some genes can be large. The primary transcripts of the neurexin genes, for instance, are as large as 1.7 megabases (1,700,000 bases), while the mature (processed) neurexin mRNAs are under 10 kilobases (10,000 bases), with as many as 24 exons and thousands of possible alternative splice variants that produce proteins with different activities. Alternative splicing is now incorporated in as much as 60% of human genetic coding, drastically increasing the potential variety of actual proteins produced.

Trans-splicing

Observed in range of different eukaryotes (including most conspicuously the worm C. elegans and a group of parasitic protists called kinetoplastids), trans-splicing occurs whereby an exon from one RNA molecule is spliced onto the 5' end of a completely separate molecule post-transcriptionally. While relatively unimportant to many eukaryotes, the role of this process in the biology of some organisms is ubiquitous. In kinetoplastids, for example, every single nuclear-encoded message must be trans-spliced before translation of the message can occur.

TamiFlu

2012-04-30T17:39:00.000+05:30

Tamiflu (oseltamivir phosphate) is an antiviral drug marketed by the Swiss pharmaceutical company Roche. It belongs to a group of drugs called neuraminidase inhibitors and can shorten the duration and lessen the severity of the type A and B strains of the flu, as well as bird flu.

How neuraminidase inhibitors works

Tamiflu targets a protein called neuraminidase that lives on the flu virus cells. This protein helps the flu virus break through the cell walls so it can move on to other cells and replicate itself. Tamiflu inhibits the neuraminidase protein, so that the virus can't leave the cell to infect other cells. Eventually, the virus dies.

How Tamiflu kills the virus

Tamiflu can't stop the flu entirely. However, studies have shown that if you take it within 48 hours of showing symptoms, it can shorten the duration of the flu (strains A and B). Patients with the flu who took it felt better 30 percent (or 1.3 days) faster than people who didn't take it . The drug also can help protect you from getting the flu if you're exposed to someone who has it. But Tamiflu can't prevent the spread of the disease, and it won't stop illnesses (like the common cold) that resemble the flu.

GST-fusion Protein Purification

2012-04-19T10:23:00.000+05:30

PROCEDURE

1. In a 125 mL flask containing 10 mL of LB and 10 mL ofAmpicillin (100 mg/mL -for pGEX vectors, Life Technologies), transfer a single colony and Grow overnight

2. Transfer 5 mL of ON culture to a 250 mL flask with 45 mL of LB and 50 mL of Ampicillin (100 mg/mL)

3. Incubate at 28-37oC until A600 reaches 0.7 (best) - 0.8 (up to ~1.0). Induce with 10 mL of 1M IPTG/50 mL culture*. Incubate at 28oC (can also try at 37oC) for >2 hours at 250 rpms (longer incubations are OK if the GST-protein is stable and/or growing in BL21-DE3 proteolysis- cells)

*NOTE: varying the concentrations of IPTG may increase the yield of your protein (5 - 25mL of 1M IPTG/50 mL culture)

NOTE: growth of the expressed protein at 28oC after induction is supposed to reduce aggregation of the fusion protein

4. Centrifuge at 8,000 g for 10 mins at 4oC and discard the supernatant

Note: the pellet can be stored at -80oC for weeks

5. Resuspend pellet with 10 mL of cold buffer + 10 µL of 100 mM PMSF at 4oC.

BEST: in addition to the PMSF, other protease inhibitors should be added. A good cocktail of protease inhibitors is Complete (from Roche). This cocktail comes as a tablet that can be dissolved in 10 mL of buffer and provides good inhibition against 5 of the main proteases (at pH 7.8)

6. Lyze cells by 2-3 passages through a French press (4oC) at a pressure no lower than 1100 psi (keep pressure around 1100-1200 rpms) (cell lysis can be detected by clearing of suspension unless a high concentration of inclusion bodies is present)

NOTE: other means of cell lysis, like sonication, are not as good as a French press. In my hands, purifying the proteins I have purified, French-pressed samples yield more purified protein when compared to other extraction procedures. In a study I performed, 10 times more protein was obtained using a French-pressed sample as compared to a sonicated one

7. Add 0.5 mL of 20% Triton X-100/10 mL of lysate (to 1%Triton X-100). Mix on a rocker for 30-60 mins at 4oC (longer incubations may reduce the amount of inclusions bodies)

8. Centrifuge at 12,000 g for 20 minutes at 4oC and save the supernatant (can be stored at -80oC). This is termed total soluble protein = T

Optional: Inclusion Body (IB) proteins can be solubilized. Add 1 mL/50 mL culture pellet of IB buffer, sonicate (2-4x for 10-15 secs in a water bath somicator), resuspend and mix on a shaker for >30-60 mins at 4oC. Centrifuge at 12,000 g for 15 mins and save IB supernatant

9. Equilibrate a 50% slurry of Glutathione Sepharose 4B (Pharmacia Biotech, catalog # 27-4574-01) with PBS for 10 mins, spin for 2 mins at 500 g and discard wash. Add 10 mL of T / 2 mL of 50% slurry

Glutathione Sepharose 4B: store in 20% ethanol. 200-400 mmol Glutathione Sepharose per g dried substance. Spherical beads, 45-165 mm wet diameter. Spacer arm: 12 atoms (10 carbons)

10. Rock for >20 minutes at RT

11. Centrifuge at 500 g for 1 min. Save an aliquot of solution (Flow Through = FT)

12. Aspirate off supernatant withough getting too close to the beads and wash 4 times with 1X PBS/Wash solution each for <1 minute, namely invert the tube until the beads are resuspended (centrifuge for 2 mins at 500 g to pellet beads).

Mechanisms of Musculoskeletal Pain

2012-04-19T10:06:00.000+05:30

Musculoskeletal pain is pain that affects the muscles, ligaments and tendons, along with the bones.The causes of musculoskeletal pain are varied. Muscle tissue can be damaged with the wear and tear of daily activities. Trauma to an area (jerking movements, auto accidents, falls, fractures, sprains, dislocations, and direct blows to the muscle) also can cause musculoskeletal pain. Other causes of pain include postural strain, repetitive movements, overuse, and prolonged immobilization. Changes in posture or poor body mechanics may bring about spinal alignment problems and muscle shortening, therefore causing other muscles to be misused and become painful. Musculoskeletal pain affects the bones, muscles, ligaments, tendons, and nerves. It can be acute (having a rapid onset with severe symptoms) or chronic (long-lasting). Musculoskeletal pain can be localized in one area, or widespread. Lower back pain is the most common type of musculoskeletal pain. Other common types include tendonitis, myalgia (muscle pain), and stress fractures.

Nociceptive Pain Animation

2012-04-19T09:59:00.001+05:30

Nociceptive pain is caused by stimulation of peripheral nerve fibers that respond only to stimuli approaching or exceeding harmful intensity (nociceptors), and may be classified according to the mode of noxious stimulation; the most common categories being "thermal" (heat or cold), "mechanical" (crushing, tearing, etc.) and "chemical" (iodine in a cut, chili powder in the eyes).

Nociceptive pain may also be divided into "visceral," "deep somatic" and "superficial somatic" pain. Visceral structures are highly sensitive to stretch, ischemia and inflammation, but relatively insensitive to other stimuli that normally evoke pain in other structures, such as burning and cutting. Visceral pain is diffuse, difficult to locate and often referred to a distant, usually superficial, structure. It may be accompanied by nausea and vomiting and may be described as sickening, deep, squeezing, and dull.[15] Deep somatic pain is initiated by stimulation of nociceptors in ligaments, tendons, bones, blood vessels, fasciae and muscles, and is dull, aching, poorly-localized pain. Examples include sprains and broken bones. Superficial pain is initiated by activation of nociceptors in the skin or other superficial tissue, and is sharp, well-defined and clearly located. Examples of injuries that produce superficial somatic pain include minor wounds and minor (first degree) burns.

Central Nervous System Mechanisms of Pain Modulation

2012-04-19T09:51:00.000+05:30

Animation on Pain Modulation in central nervous systems

Opiates Action against pain

2012-04-19T09:41:00.000+05:30

A good Animation on how Opiates act against pain

Malaria (Plasmodium) life cycle Video

2012-04-19T09:27:00.000+05:30

Complex life cycle of Plasmodium parasite. Life Cycle of the Malaria Parasite A female Anopheles mosquito carrying malaria-causing parasites feeds on a human and injects the parasites in the form of sporozoites into the bloodstream. The sporozoites travel to the liver and invade liver cells. Over 5-16 days*, the sporozoites grow, divide, and produce tens of thousands of haploid forms, called merozoites, per liver cell. Some malaria parasite species remain dormant for extended periods in the liver, causing relapses weeks or months later.

The merozoites exit the liver cells and re-enter the bloodstream, beginning a cycle of invasion of red blood cells, asexual replication, and release of newly formed merozoites from the red blood cells repeatedly over 1-3 days*. This multiplication can result in thousands of parasite-infected cells in the host bloodstream, leading to illness and complications of malaria that can last for months if not treated. Some of the merozoite-infected blood cells leave the cycle of asexual multiplication. Instead of replicating, the merozoites in these cells develop into sexual forms of the parasite, called male and female gametocytes, that circulate in the bloodstream. When a mosquito bites an infected human, it ingests the gametocytes. In the mosquito gut, the infected human blood cells burst, releasing the gametocytes, which develop further into mature sex cells called gametes. Male and female gametes fuse to form diploid zygotes, which develop into actively moving ookinetes that burrow into the mosquito midgut wall and form oocysts. Growth and division of each oocyst produces thousands of active haploid forms called sporozoites. After 8-15 days*, the oocyst bursts, releasing sporozoites into the body cavity of the mosquito, from which they travel to and invade the mosquito salivary glands. The cycle of human infection re-starts when the mosquito takes a blood meal, injecting the sporozoites from its salivary glands into the human bloodstream .

F1 making ATP

2012-04-19T09:21:00.000+05:30

Watch the F1 component of the ATP Synthase molecule make ATP. The rotational force produce by the F0 component (not seen here) allows the rotation of the gamma component to move similar to a cam-shaft on an auto. This rotation allows the F1 component to open and close. The action of the opening and closing allows the ADP and Pi to enter, be brought into proximity and joined to make ATP. Watch the sequence.

Depolarization: Phase 1 of the Action Potential

2012-04-17T13:25:00.002+05:30

Potassium Channel

2012-04-17T13:24:00.003+05:30

What is Gibbs-Donnan Equilibrium

2012-04-17T13:23:00.000+05:30

The Gibbs–Donnan effect (also known as the Donnan effect, Donnan law, Donnan equilibrium, or Gibbs–Donnan equilibrium) is a name for the behavior of charged particles near a semi-permeable membrane to sometimes fail to distribute evenly across the two sides of the membrane. The usual cause is the presence of a different charged substance that is unable to pass through the membrane and thus creates an uneven electrical charge. For example, the large anionic proteins in blood plasma are not permeable to capillary walls. Because small cations are attracted, but are not bound to the proteins, small anions will cross capillary walls away from the anionic proteins more readily than small cations.

Staining of a Gram-Negative Bacterium

2012-04-15T02:54:00.003+05:30

Staining of a Gram-Positive Bacterium

2012-04-15T02:52:00.001+05:30

Measuring Serum Antibody with an Agglutination Assay

2012-04-15T02:46:00.001+05:30

This short animation demonstrates measuring serum antibody with an agglutination assay.

Agglutination assay to detect antigens

2012-04-15T02:42:00.000+05:30

Agglutination assays are based upon the premise that antibody or antigen coated particles are agglutinated in the presence of the complementary soluble antigen or antibody. The tests are usually performed in microwells and the results are read, usually by eye or sometimes by automated pattern reading, simply by looking for agglutination in the bottom of the microwe

Immunfluorescence

2012-04-15T02:33:00.000+05:30

Immunofluorescence is a technique used for light microscopy with a fluorescence microscope and is used primarily on biological samples. This technique uses the specificity of antibodies to their antigen to target fluorescent dyes to specific biomolecule targets within a cell, and therefore allows visualisation of the distribution of the target molecule through the sample. Immunofluorescence is a widely used example of immunostaining and is a specific example of immunohistochemistry that makes use of fluorophores to visualise the location of the antibodies.

Developing Egg Cells

2012-04-15T02:25:00.000+05:30

Action Potentials and Muscle Contraction

2012-04-13T01:47:00.000+05:30

A muscle contraction (also known as a muscle twitch or simply twitch) occurs when a muscle fiber generates tension through the action of actin and myosin cross-bridge cycling. While under tension, the muscle may lengthen, shorten or remain the same. Though the term 'contraction' implies a shortening or reduction, when used as a scientific term referring to the muscular system contraction refers to the generation of tension by muscle fibers with the help of motor neurons. Locomotion in most higher animals is possible only through the repeated contraction of many muscles at the correct times. Contraction is controlled by the central nervous system (CNS), which comprises the brain and spinal cord. Voluntary muscle contractions are initiated in the brain, while the spinal cord initiates involuntary reflexes.

An action potential originating in the CNS reaches an alpha motor neuron, which then transmits an action potential down its own axon.
The action potential activates voltage-dependent calcium channels on the axon, and calcium rushes in.
Calcium causes vesicles containing the neurotransmitter acetylcholine to fuse with the plasma membrane, releasing acetylcholine into the synaptic cleft between the motor neuron terminal and the motor end plate of the skeletal muscle fiber.
The acetylcholine diffuses across the synapse and binds to and activates nicotinic acetylcholine receptor on the motor end plate. Activation of the nicotinic receptor opens its intrinsic sodium/potassium channel, causing sodium to rush in and potassium to trickle out. Because the channel is more permeable to sodium, the muscle fiber membrane becomes more positively charged, triggering an action potential.
The action potential spreads through the muscle fiber's network of T-tubules, depolarizing the inner portion of the muscle fiber.
The depolarization activates L-type voltage-dependent calcium channels (dihydropyridine receptors) in the T tubule membrane, which are in close proximity to calcium-release channels (ryanodine receptors) in the adjacent sarcoplasmic reticulum.
Activated voltage-gated calcium channels physically interact with calcium-release channels to activate them, causing the sarcoplasmic reticulum to release calcium.
The calcium binds to the troponin C present on the actin-containing thin filaments of the myofibrils. The troponin then allosterically modulates the tropomyosin. Normally the tropomyosin sterically obstructs binding sites for myosin on the thin filament; once calcium binds to the troponin C and causes an allosteric change in the troponin protein, troponin T allows tropomyosin to move, unblocking the binding sites.
Myosin (which has ADP and inorganic phosphate bound to its nucleotide binding pocket and is in a ready state) binds to the newly uncovered binding sites on the thin filament (binding to the thin filament is very tightly coupled to the release of inorganic phosphate). Myosin is now bound to actin in the strong binding state. The release of ADP and inorganic phosphate are tightly coupled to the power stroke (actin acts as a cofactor in the release of inorganic phosphate, expediting the release). This will pull the Z-bands towards each other, thus shortening the sarcomere and the I-band.
ATP binds myosin, allowing it to release actin and be in the weak binding state (a lack of ATP makes this step impossible, resulting in the rigor state characteristic of rigor mortis). The myosin then hydrolyzes the ATP and uses the energy to move into the "cocked back" conformation. In general, evidence (predicted and in vivo) indicates that each skeletal muscle myosin head moves 10-12 nm each power stroke, however there is also evidence (in vitro) of variations (smaller and larger) that appear specific to the myosin isoform.
Steps 9 and 10 repeat as long as ATP is available and calcium is present on thin filament.
While the above steps are occurring, calcium is actively pumped back into the sarcoplasmic reticulum. When calcium is no longer present on the thin filament, the tropomyosin changes conformation back to its previous state so as to block the binding sites again. The myosin ceases binding to the thin filament, and the contractions cease.
The calcium ions leave the troponin molecule in order to maintain the calcium ion concentration in the sarcoplasm. The active pumping of calcium ions into the sarcoplasmic reticulum creates a deficiency in the fluid around the myofibrils. This causes the removal of calcium ions from the troponin. Thus the tropomyosin-troponin complex again covers the binding sites on the actin filaments and contraction ceases.

ACNE

2012-04-13T01:45:00.000+05:30

Acne vulgaris (commonly called Acne) is a skin disease, caused by changes in the pilosebaceous units (skin structures consisting of a hair follicle and its associated sebaceous gland). Severe acne is inflammatory, but acne can also manifest in noninflammatory forms. Acne lesions are commonly referred to as pimples, spots, or zits. Acne is most common during adolescence, affecting more than 85% of teenagers, and frequently continues into adulthood. For most people, acne diminishes over time and tends to disappear, or at least decrease, after one reaches his or her early twenties. There is, however, no way to predict how long it will take for it to disappear entirely, and some individuals will continue to suffer from acne decades later, into their thirties and forties and even beyond. The term acne comes from a corruption of the Greek άκμή (acme in the sense of a skin eruption) in the writings of Aëtius Amidenus. The vernacular term bacne or backne is often used to indicate acne found specifically on one's back.

Subscribe in a reader

Symptoms
The most common form of acne is known as "acne vulgaris", meaning "common acne". Many teenagers get this type of acne. The face and upper neck are the most commonly affected, but the chest, back and shoulders may have acne as well. The upper arms can also have acne, but lesions found there are often keratosis pilaris, not acne. The typical acne lesions are comedones and inflammatory papules, pustules, and nodules. Some of the large nodules were previously called "cysts" and the term nodulocystic has been used to describe severe cases of inflammatory acne.

Aside from scarring, its main effects are psychological, such as reduced self-esteem and, according to at least one study, depression or suicide. Acne usually appears during adolescence, when people already tend to be most socially insecure. Early and aggressive treatment is therefore advocated by some to lessen the overall impact to individuals.

Causes of acne
Acne develops as a result of blockages in follicles. Hyperkeratinization and formation of a plug of keratin and sebum (a microcomedo) is the earliest change. Enlargement of sebaceous glands and an increase in sebum production occur with increased androgen (DHEA-S) production at adrenarche. The microcomedo may enlarge to form an open comedo (blackhead) or closed comedo (whitehead). In these conditions the naturally occurring largely commensual bacteria Propionibacterium acnes can cause inflammation, leading to inflammatory lesions (papules, infected pustules, or nodules) in the dermis around the microcomedo or comedo, which results in redness and and may result in scarring or hyperpigmentation.

Primary causes
Exactly why some people get acne and some do not is not fully known. It is known to be partly hereditary. Several factors are known to be linked to acne: * Family/Genetic history. The tendency to develop acne runs in families. For example, school-age boys with acne have other members of their family with acne. A family history of acne is associated with an earlier occurrence of acne and an increased number of retentional acne lesions. * Hormonal activity, such as menstrual cycles and puberty. During puberty, an increase in male sex hormones called androgens cause the glands to get larger and make more sebum. * Stress, through increased output of hormones from the adrenal (stress) glands. * Hyperactive sebaceous glands, secondary to the three hormone sources above. * Accumulation of dead skin cells. * Bacteria in the pores. Propionibacterium acnes (P. acnes) is the anaerobic bacterium that causes acne. In-vitro resistance of P. acnes to commonly used antibiotics has been increasing. * Skin irritation or scratching of any sort will activate inflammation. * Use of anabolic steroids. * Any medication containing halogens (iodides, chlorides, bromides), lithium, barbiturates, or androgens. * Exposure to certain chemical compounds. Chloracne is particularly linked to toxic exposure to dioxins, namely Chlorinated dioxins. Several hormones have been linked to acne: the androgens testosterone, dihydrotestosterone (DHT) and dehydroepiandrosterone sulfate (DHEAS), as well as insulin-like growth factor 1 (IGF-I). In addition, acne-prone skin has been shown to be insulin resistant. Development of acne vulgaris in later years is uncommon, although this is the age group for Rosacea which may have similar appearances. True acne vulgaris in adults may be a feature of an underlying condition such as pregnancy and disorders such as polycystic ovary syndrome or the rare Cushing's syndrome. Menopause-associated acne occurs as production of the natural anti-acne ovarian hormone estradiol fails at menopause. The lack of estradiol also causes thinning hair, hot flashes, thin skin, wrinkles, vaginal dryness, and predisposes to osteopenia and osteoporosis as well as triggering acne (known as acne climacterica in this situation).

Sarcoplasmic Reticulum

2012-04-11T01:42:00.000+05:30

Sarcoplasmic Reticulum(SR) is a special type of smooth ER found in smooth and striated muscle. The only structural difference between this organelle and the smooth endoplasmic reticulum is the medley of protein they have, both bound to their membranes and drifting within the confines of their lumens. This fundamental difference is indicative of their functions: the smooth ER synthesizes molecules and the sarcoplasmic reticulum stores and pumps calcium ions. The sarcoplasmic reticulum contains large stores of calcium, which it sequesters and then releases when the cell is depolarized. This has the effect of triggering muscle contraction.

Sarcoplasmic Reticulum is physically separate from the sarcolemma and surrounds each myofibril. Sarcoplasmic reticulum membrane contains high levels of calcium ATPase. The sarcoplasmic reticulum functions to uptake calcium from the sarcoplasm and to release calcium into the sarcoplasm to initiate contraction and sequester it during relaxation.

it has been implicated as a major contributor to the depressed function in heart failure. The SR acts as a calcium source during contraction and a calcium sink during relaxation. Relaxation is mediated by the transport of calcium into the sarcoplasmic reticulum lumen by a Ca-ATPase, which is under reversible regulation by phospholamban, a low molecular weight phosphoprotein. Calcium then binds to calsequestrin in the lumen of the SR. For the initiation of contraction, calcium is released through the calcium channels or ryanodine receptors, which are under regulation by junctin, triadin and partially by a novel protein, the histidine rich calcium-binding protein. Thus, the SR is the major regulator of Ca2+-handling and contractility in muscle