Friday, 11 September 2015

Vitamin-B 12 (Cyanocobalamin)-An Update

Vitamin-B 12 (Cyanocobalamin)-An Update
Vitamin B12 may be found in liver, kidney, fish, and fortified milk and helps convert folic acid into its active form. Vitamin B12 is essential to synthesize DNA and promotes cellular division and is required for hematopoiesis (development of red blood cells in bone marrow) and to maintain the integrity of the nervous system. 
Vitamin B12 is absorbed in the intestine with the aid of an intrinsic factor produced by gastric parietal cells. Once absorbed, vitamin B12 binds to the transcobalamin II protein and is then transferred to tissues. Vitamin B12 is stored in the liver for up to three years during which time it is slowly excreted in urine. 
Vitamin B12 deficiency is common in patients who are strict vegetarians and in patients who have malaborption syndromes (cancer, celiac disease), gastrectomy, Crohn’s disease, and liver and kidney diseases. Vitamin B12 (cyanocobalmin) administered both orally and parenterally is equally effective in treating anemia from vitamin B12 deficiency. 
However, use of parenteral cyanacobalamin is the most common method of vitamin B12 replacement because it may be more reliable and practical. Subcutaneous or intramuscular administration is appropriate. Vitamin B12 is absorbed completely following parenteral administration, whereas oral vitamin B12 is absorbed poorly via the GI tract. 
Furthermore, use of parenteral vitamin B12 to treat megaloblastic anemia may circumvent the need to perform a Schilling test to diagnose lack of intrinsic factor. A typical cyanocobalmin dosing regimen is 800 to 1000 mcg/day for 1 to 2 weeks, followed by 100 to 1000 mcg/day every week until the Hgb/Hct normalizes and maintenance of 100 to 1000 mcg monthly for life. However, a number of dosing regimens exist. In addition, a number of oral vitamin B12 preparations are available, including many over-the-counter formulations. 
A common oral dosing regimen is from 1000 to 2000 mcg/day. If parenteral cyanocobalmin is used initially, oral vitamin B12 can be useful as maintenance therapy. Typically, the response to therapy is quick. Neurologic symptoms and megaloblastic cells disappear within a few days, and hemoglobin levels increase after a week of therapy.Vitamin B12 generally is well tolerated and exhibits minimal adverse effects. Injection-site pain, pruritus, rash, and diarrhea have been reported. Drug interactions have been observed with omeprazole and ascorbic acid that decrease oral absorption.

Tuesday, 7 April 2015



DNA Cloning

Creating the clone

Isolating the clone

DNA sequencing



Sunday, 8 March 2015

Absorption of Drugs
General definitions in Pharmacology

  •  Pharmacology is the study of the interaction of chemicals with living systems.
  •    Drugs are chemicals that act on living systems at the chemical (molecular) level.
  • Medical pharmacology is the study of drugs used for the diagnosis, prevention, and treatment of disease.
  • Toxicology is the study of the untoward effects of chemical agents on living systems. It is usually considered an area of pharmacology
  • Pharmacodynamic properties of a drug describe the action of the drug on the body, including receptor interactions, dose-response phenomena, and mechanisms of therapeutic and toxic action.
  • Pharmacokinetic properties describe the action of the body on the drug, including absorption, distribution, metabolism, and excretion. Elimination of a drug may be achieved by metabolism or by excretion.


A.    Size. The great majority of drugs lie in the range from molecular weight 100 to 1,000. Drugs in this range are large enough to allow selectivity of action and small enough to allow adequate movement within the various compartments in the body.
B.      Chemistry and reactivity. Drugs may be small, simple molecules (amino acids, simple amines, organic acids, alcohols, esters, ions, etc.), carbohydrates, lipids, or even proteins. Binding of drugs to their receptors. the specific molecules in a biologic system that mediate drug effects, is usually by noncovalent bonds (hydrogen bonds, van de Waals attractions, and ionic bonds), and less commonly by covalent bonds. Weaker, noncovalent bonds require a better fit of the drug to the receptor binding site and, usually, a reversible type of action. Very strong bonding, eg, covalent bonds, usually involves less selectivity and an irreversible interaction.
C.     Shape. The overall shape of a drug molecule is important for the fit of the drug to its receptor. Between a quarter and a half of all drugs in use exist as stereoisomers. In most cases the stereoisomers are chiral enantiomers. Enantiomers are mirrored image twin molecules that result from the presence of an asymmetric carbon, or in a few cases, other asymmetric atoms in their structures. Chiral enantiomers often differ in their ability to bind to and alter the function of receptors. They also can differ in their rates of elimination and in their toxicity.


Pharmacokinetics concerns the effects of the body on the administered drug. It can be pictured as the processes of absorption, distribution, and elimination. Elimination includes both metabolism and excretion. All of these processes involve movement of drug molecules through various body compartments and across the barriers separating those compartments.

 A. Absorption of Drugs. Drugs usually enter the body at sites remote from the target tissue and are carried by the circulation to the intended site of action. Before a drug can enter the bloodstream, it must be absorbed from its site of administration. The rate and efficiency of absorption differs depending on the route of administration. Common routes of administration of drugs and some of their features include:

Oral (swallowed). Maximum convenience but may be slower and less complete than parenteral (non-oral) routes. Dissolution of solid formulations (eg, tablets) must occur first. The drug must survive exposure to stomach acid. This route of administration is subject to the first pass effect (metabolism of a significant amount of drug in the gut wall and the liver, before it reaches the systemic circulation).

Sublingual (under the tongue). Permits direct absorption into the systemic venous circulation thus avoiding the first pass effect. May be fast or slow depending on the physical formulation of the product. Nitroglycerin is administered by this route in the treatment of angina.

Rectal (suppository). Same advantage as sublingual route; larger amounts are feasible. Useful for patients who cannot take oral medications (eg, because of nausea and vomiting).

Intramuscular. Absorption is sometimes faster and more complete than after oral administration. Large volumes (eg, 5 - 10 mL) may be given. Requires an injection. Generally more painful than subcutaneous injection. Vaccines are usually administered by this route.

Subcutaneous. Slower absorption than intramuscular. Large volumes are not feasible. Requires an injection. Insulin is administered by this route.

Inhalation. For respiratory diseases, this route deposits drug close to the target organ; when used for systemic administration (e.g., nicotine Susan Masters, PhD 63 in cigarettes, inhaled general anesthetics) it provides rapid absorption because of the large surface area available in the lungs.

Topical. Application to the skin or mucous membrane of the nose, throat, airway, or vagina for a local effect. It is important to note that topical drug administration can result in significant absorption of drug into the systemic circulation. Drugs used to treat asthma are usually administered this way.

Transdermal. application to the skin for systemic effect. Transdermal preparations generally are patches that stick to the skin and are worn for a number of hours or even days. To be effective by the transdermal route, drugs need to be quite lipophilic. Nicotine is available as a transdermal patch for those who are trying to stop cigarette smoking.

Intravenous. Instantaneous and complete absorption (by definition, 100%); potentially more dangerous because the systemic circulation is transiently exposed to high drug concentrations.

Wednesday, 25 February 2015

 (General principles of microbial concepts)

Microorganisms (Latin micro = small) are living beings so small (< 40 µm or 0.04 mm) that they are not visible by the naked eye. Microorganisms related to human health include certain bacteria, viruses, fungi and parasites.

Types of Microorganisms:

Microorganisms can be, according to their characteristics, divided into several groups:
  • bacteria, viruses, certain fungi and parasites
  • pathogenic (capable of causing disease), non-pathogenic, and opportunistic (causing disease when they have an opportunity, like in people with low immune system)
  • acellular (without cell, like viruses), unicellular (bacteria, yeasts and certain parasites), or multi-cellular (molds)

 1. Bacteria
Bacteria are unicellular organisms, about few microns in size (1 micron (µm) = 1/1,000 of a millimetre), consisting of DNA, cytoplasm, structures needed for metabolism and reproduction, cell membrane, cell wall and capsule .Certain bacteria use flagella, tail-like appendages, to propel themselves.

  Bacterial structure

Bacteria multiply asexually by dividing into two daughter cells
Bacteria can be divided into several groups:
  • Spheres or cocci (like Staphylococcus aureus), rods or bacilli (like Lactobacillus acidophilus), spirals or spirochetes (like Treponema pallidum); bacterial shape can help in their recognizing under the microscope
  • Aerobic bacteria, like Mycobacterium tuberculosis, need oxygen to thrive, while  anaerobic, like Clostsridium difficile, do not. Facultative anaerobic bacteria, like Pseudomonas aureginosa, can live in aerobic and anaerobic environment.
  • Gram positive (G+) bacteria, like Streptococcus, and Gram negative (G-) bacteria, like Klebsiella
  • Pathogenic and non-pathogenic bacteria

Certain bacteria can form endospores, a kind of encapsulated bunkers within a bacteria that enable vital parts of bacteria to survive in harsh conditions, like freezing or boiling water, dessication, lack of nutrients, etc. Some bacteria can survive weeks, and some millions of years in this form.
In the human body, bacteria usually cause localized infections, like pneumonia or skin infections. Bacterial infections can be diagnosed by growing a bacterial culture from a sample of infected body fluid (e.g. urine, blood), stool, discharge (e.g. sputum) or tissue (e.g. mucosal layer of the stomach). Most of bacterial infections can be successfully treated by anti-bacterial drugs – antibiotics.
Examples of bacteria pathogenic for a human are:
  • Staphylococcus aureus, causing skin infections, pneumonia, and infection of the heart valves, etc.
  • Streptococcus pyogenes, causing “strep throat”, cellulitis, etc.
  • Neisseria gonorrheae, causing gonorrhea
  • Salmonella, causing diarrhea in food poisoning
  • Helicobacter pylori, causing chronic gastritis
  • Mycoplasma, causing atypical pneumonia

Examples of non-pathogenic bacteria:
  • Staphylococcus epidermidis, a part of normal skin flora
  • Lactobacillus acidophilus, a part of normal intestinal flora
Examples of opportunistic bacteria:
  • Certain intestinal bacteria, like Escherichia coli and Enterobacter live in the human intestine without causing any symptoms, but in a person with lowered immune system they may overgrow and cause a bowel infection.

2. Viruses

Viruses are simple microorganisms, containing only DNA or RNA molecule and capsule. They cannot survive outside the host for long periods, so they are mainly transmitted by blood-to-blood or stool-to-mouth route. In the human body, they have to invade the cells to multiply

Virus cycle: entry of herpes simplex virus (HSV) into the cell (on the left), multiplying within the cell and release (right) from the cell 

Viruses usually cause systemic infections, affecting the whole body. Examples of viruses, pathogenic for a human:
  • Rhinovirus, causing common cold
  • Influenzavirus, causing flu, bird flu, swine flu
  • Herpes simplex virus causing herpes labialis (cold sore) or herpes genitalis
  • HIV, causing AIDS
  • Ebolavirus, causing hemorrhagic fever
Viruses can be diagnosed by finding specific antibodies in the sample of blood (serologic tests). Vaccination against several virus infections is possible; only few viral infections can be treated by anti-viral medications, though.

3. Fungi

Fungi are widely present in the environment and also on the human skin, gut and vagina.
The three major groups of fungi are:
·         multicellular filamentous moulds
·         single celled microscopic yeasts

4. Parasites


 1),Cryptosporidium (crypto) and Cyclospora, utilize nutrients from the stool. They belong to a living kingdom Protozoa (Gk. protos = first; zoa = animals). They may cause inflammation of thesmall intestine thus hampering absorption of nutrients. Entamoeba hystolytica lives predominantly in the colon.

Intestinal Worms (Helminths):

Intestinal worms (helminths), like roundworms (hookworms), whipworms,  Ascaris andTrichinella), tapeworms and flukes, are few millimeters to several meters in size, they eat the bowel content or suck the blood from the intestinal wall and can cause about the same symptoms as one-cell parasites.


Beneficial Microorganisms

Microorganisms, like certain bacteria and yeasts, living on the human skin or in the nose, mouth, throat, small and large intestine and vagina, are part of the normal human flora; they prevent overgrowth of harmful microorganisms. Some of these microbes, when overgrow, may become pathogenic, though.

Harmful or Pathogenic Microorganisms

Pathogenic means capable of causing disease. An actual harmful effect of a microbe to the body depends on:

  • Microbial virulence - a relative ability of a microbe to cause a disease; for example, a certain, highly virulent subtype of influenza virus may cause a bird flu, which is deadly in a high percent, while “usual” influenza virus is not.
  • Invasion through the body’s barriers; staph bacteria might not cause any harm to a person with an intact skin, but can cause a severe infection of a skin wound.
  • Amount of microbes; eating few bites of food contaminated with staph bacteria may go unnoticed, while eating the whole portion of the same food may cause a severe food poisoning.
  • Body’s defense (immune) system; patients with a weak immune system, like those receiving corticosteroids, often get oral thrush (candida infection of the mouth), while otherwise healthy people do not.

Tuesday, 17 February 2015

 Physiology of Nervous system

The nervous system has two major parts: the central nervous system (CNS) and the peripheral nervous system (PNS). The central system is the primary control center for the body and is composed of the brain and spinal cord. The peripheral system consists of a network of nerves that connects the rest of the body to the CNS.
In most cases, the brain is the destination for information gathered by the rest of the nervous system. Once data arrives, the brain sorts and files it before sending out any necessary commands.
The PNS can also be divided into smaller pieces: the somatic and autonomic systems. The somatic involves parts of the body a person can command at will, and the autonomic helps run involuntary functions such as pumping blood.

The nervous system can suffer from a number of afflictions, including cancer. Other problems include multiple sclerosis, in which damaged nerves prevent signals from traveling along them, and meningitis, which causes an inflammation of the membranes surrounding the brain and spinal cord.