Tuesday, January 26, 2016

Zika virus : epidemiology, symptoms, diagnosis, treatment and prevention


What is Zika Virus ?

Zika virus falls under member of Flavivirus.  The vector for Zika vius is Aedes mosquito. Zika virus is an emerging mosquito-borne virus that was first isolated in Zika forest of Uganda in 1947. Since then, it has been observed mainly in Africa, with small and sporadic outbreaks in Asia.
Fig. Zika virus is transmitted by daytime mosquitoes
under the genus Aedes.
Credit: Photo from Wikipedia

Where has Zika virus been found?

·  Prior to 2015, Zika virus outbreaks have occurred in areas of Africa, Southeast Asia, and the Pacific Islands.
·   In May 2015, the Pan American Health Organization (PAHO) issued an alert regarding the first confirmed Zika virus infections in Brazil.
·   Currently, outbreaks are occurring in many countries.
·         Zika virus will continue to spread and it will be difficult to determine how the virus will spread over time.

Monday, December 21, 2015

Photometry: Principle, applications and types



Photometry

Fig. Principle of colorimetry
When light is passed through a coloured solution, certain wavelengths are selectively absorbed giving a plot of the absorption spectrum of the compound in solution. The wavelength at which maximum absorption is called the absorption maximum (λmax) of that compound. The light that is not absorbed is transmitted through the solution and gives the solution its colour.

Photometric instruments measure transmittance, which is defined as follows:



                               Intensity of the emergent (or transmitted) light         Ie
Transmittance (T)= ------------------------------------------------------------- = ------
                                               Intensity of the incident light                    Io

Transmittance is usually expressed on a range of 0 to 100%.

If the concentration of the substance in solution is increased linearly, or if the path length that the light beam has to traverse is increased, transmittance falls exponentially. So a term absorbance is defined so that it is directly proportional to the concentration of the substance.

                                                Ie
Absorbance (A)= log1/T = log  ----
                                                Io

Absorbance has no units. Photometric instruments electronically convert the measured transmittance to absorbance values.

Sunday, December 20, 2015

Cerebrospinal fluid (CSF) : Formation, composition, function, pathological state and biochemical analysis


A. Formation

Cerebrospinal fluid (CSF) is a clear, colourless fluid filling the ventricles and subarachnoid space. CSF production is a result of the combined processes of diffusion, pinocytosis and active transfer. The majority is produced by selective dialysis of blood plasma by a specialized sponge-like structure called the "choroid plexus" of third, lateral and fourth ventricles.

Fig. CSF collection
The anatomy of the ventricular system allows for movement of CSF in and around all the major structures of the brain. From the lateral ventricles located within the cerebral hemisphere, it circulates through the foramina of Monro into the third ventricle. At its caudal end, the third ventricle is connected by aqueduct of Sylvius to the fourth ventricle. CSF then flows into the basal cisterns and subarachnoid space by two lateral foramina of Lusckha and median foramina of Magendie. From the cisterns the CSF flows / throughout the subarachnoid space and over the hemispheric convexities and around the spinal cord.


Thursday, December 17, 2015

Protein separation techniques: Protein fractionation



Fig. Protein purification steps
Proteins differ in their molecular size and charge. They can be separated on the basis of their following properties:
1.       molecular size
2.       solubility
3.       electrical charge
4.       adsorption properties
5.       specific bioaffinity.

Many techniques for protein purification exist, but the emphasis here is on some of the most popular procedures and the principles involved in their use.  Protein fractionation is required to separate and characterize a protein in detail.

Qualitative and qualitative estimation of Proteins



Proteins are the most abundant biomolecules, constituting more than 50% of the dry weight of the cell. They are known to perform many different biological functions.  Qualitative and quantitative estimation of proteins in biological fluids is based on the physico-chemical properties of proteins.

Denaturation of proteins

In each type of protein, the three dimensional structure is essential for its biological function.  A protein in the biologically active form is termed as the native protein and the native state is called “optimum” state. The disruption of the three dimensional structure is called denaturation.  On denaturation, the primary structure remains intact.  It is an all or none phenomenon and does not cause any alteration in the quantity of protein present.

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