Thyroid agents and Anti-thyroid drugs

Thyroid agents are used to treat Hypothyroidism and Anti-thyroid drugs are used to treat Hyperthyroidism.

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Pilocarpine

Pilocarpine is a Parasympathomimetic agent.

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Homatropine

Homatropine is a mydriatic agent.

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Heparin

Heparin is an anti-coagulant.

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Aminoglycosides

Aminoglycosides belong to the group of Anti-infectives.

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Fermentation

Introduction:
More commonly, fermentation is the conversion of biological materials, by enzymes, into carbon dioxide and alcohol. This is particularly for the utilization of foodstuffs.

The Merriam-webster Dictionary defines fermentation as:
"an enzymatically controlled anaerobic breakdown of an energy-rich compound (as a carbohydrate to carbon dioxide and alcohol or to an organic acid) ; broadly : an enzymatically controlled transformation of an organic compound".

Fermentation is the process of creating energy through the oxidative process of organic compounds, such as carbohydrates, by the use of endogenous electron acceptor. Fermentation is mostly carried out in an anaerobic environment. But some yeast cells also cause fermentation in the presence of oxygen (more or less) as long as sugar is there for consumption.

Reaction:
In the fermentation process, if we take the example of glucose, following reaction takes place:

Glucose (Sugar)----->Ethanol (Alcohol) + CO2 + Energy (in the form of ATP)

The early stages of this reaction follows part of the glycolysis pathway but most of the pathways depends on the sugar involved or used. The later stages of the pathway depends on the product obtained.

Processes of fermentation:
Primary fermentation: This is first step in the fermentation process, which involves the conversion of sugar to alcohol and carbon dioxide. This usually starts when we add yeast (or bacteria) to the organic compound and it starts to multiply and starts feeding on the fermentable sugars. Many of the aroma compounds are also produced durign the primary fermentation process. In human beings also, cells use fermentation as the first step in breaking down sugar.


Secondary fermentation: Stage of fermentation occuring from several weeks to several months. It is also referred to as "Malolactaic fermentation". Here, bacteria converts the malic acid to lactic acid. (2) This lactic acid in human beings is further broken down by the process of respiration and results in carbon dioxide and water. (This lactic acid accumulates in our muscles and causes pain, if we exert ourselves.)

Types of Fermentation:
Photofermentation: This is the type of fermentation that takes place by photosynthetic bacteria in the presence of light and involves the same steps as in the anaerobic conversion.

Dark fermentation: This fermentation takes place in the absence of light and involves the same steps as those of anaerobic conversion.

Thermophilic fermentation: Fermentation takes place in heating environment.

Uses of Fermentation:
(Michael D. Flythe et al.)Mankind has used fermentation to preserve animal feed for thousands of years. (1) Fermentation takes place in the large intestine of almost animals but in carnivores and omnivores, it produces very few calories but in case of herbivores this is the major cause of energy production. (2) Yeasts produce alcohols from sugars and this is used to produce spirits and ethanol. CO2 produced during the fermentation process is used to cause bubbles in bread. Bacteria which are used in the lactic acid formation are used in cheese making process and in making buttermilk, sour cream and yogurt.
(Ghasem Najafpour) In world war I, Germany found that glycerol can be generated from alcoholic fermentation. They developed an industrial scale fermentation process with a yield capacity of 1000 tons of glycerol per month.

References:
(1) http://www.vivo.colostate.edu/hbooks/pathphys/digestion/largegut/ferment.html

(2) http://www.historyoftheuniverse.com/ferment.html

Ghasem Najafpour. Chapter 10 - Application of Fermentation Processes. Biochemical Engineering and Biotechnology, 2007, Pages 252-262.

Michael D. Flythe, James B. Russell. Fermentation acids inhibit amino acid deamination by Clostridium sporogenes MD1 via a mechanism involving a decline in intracellular glutamate rather than protonmotive force. Microbiology 152 (2006), 2619-2624

Further Reading:
Fermentation Microbiology and Biotechnology, Second Edition by E. M. T. El-Mansi, C. F. A. Bryce, Arnold L. Demain and A. R. Allman

Practical Fermentation Technology by Brian McNeil and Linda Harvey

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Penicillins

Penicillins belong to the class of anti-infectives. This diagram may help to give you a bird's eye view of Penicillins.
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Macrolides

Macrolides belong to the class of anti-infectives. This diagram may help to give you a bird's eye view of macrolides.
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Chloramphenicol

Chloramphenicol belong to the class of anti-infectives. This diagram may help you to give you bird's eye view of chloramphenicol.
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Cephalosporins

Cephalosporins belong to the class of anti-infectives. This diagram may help you to give you bird's eye view of cephalosporins.

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Micelles

These are aggregates of surfactant molecules or ions in a solution or liquid colloid. These aggregates are made up of the water loving surface and an inner fatty core.

Micelle formation is done at a well defined concentration that is the critical micelle concentration.

Usually surface active agents behave as normal compounds in dilute solution but at certain reasonably well defined concentrations relatively sharp changes occur in the physical properties of these solutions.


These changes are attributed to the association of the amphipathic molecules or iond into aggregates of colloidal dimensions that are known as micelles.

Ionic and non-ionic substances that exhibit this type of behavior are referred to collectively as association colloids.

Critical Micelle concentration and micellar structure:
The minimum concentration at which physical properties of solutions of association colloids marked changes is known as critical micelle concentration. It is abbreviated as CMC.

Determination of critical micelle concentration:

(H. B. Klevens et al.)Critical micelle concentration (CMC) can be determined:
1. By Conductivity and transport number, which require the application of external electric forces.
2. Spectral dye method.
3. By solubilization studies which require the use of dyes or hydrocarbons.
4. By viscosity which involves the application of a shearing force.

Concept of formation of micelles is introduced to explain the apparent changes in osmotic properties and electrical conductivity with concentration in solutions of ionic associated colloids.

The conductivity indicated that a considerable degree of electrolytic dissociation was occurring in solution whereas the osmotic properties indicated that considerable aggregation of ions into single colligative units was also occurring above CMC.

Types of Micelles:
There are two basic types of micelles:

a. a small approximately spherical charged micelle which existed in all concentration i.e. above and below the CMC and which was largely responsible for the appreciable electrical conductivity and

b. a large undissociated lamellar micelle which only existed above the CMC and was responsible for the low osmotic properties at such concentrations.

Model of micelle:

Hartley’s model of spherical micelle

This model consists of a spherical charged micelle with a radius approximately equal to the chain length of the amphipathic ion.

The spherical type of micelle is now accepted as existing in all solutions of associated colloids at and just above the CMC.

However, in more concentrated solutions physical measurement for example X-ray diffraction, viscosity, light scattering indicate the existence of large asymmetric micelles.

How, large micelles are formed?
The rearrangement from spherical to larger and more widely separated asymmetric micelles has been ascribed to a reaction of the system in an effort to reduce the intermicellar repulsive forces that arise from the closer and closer approach of spherical micelles as the concentration of amphipathic material increases.

Different micellar shapes like rods and lamellae are also formed in different systems.

Stability and size of spherical micelles:
The cohesive force between water molecules is much stronger than either the attraction between the lipophilic parts of the surface active agents or the attraction between water and the lipophilic chains.

Therefore, the surface active agent tends to be squeezed out of solution in order to reduce the large degree of separation of water molecules that would be caused by the presence of many monomeric amphipathic molecules.

This effort which tends to cause a phase separation is counterbalanced to some extent by the hydrophilic nature of the polar groups.

In addition, the attractive forces between water molecules decay very rapidly with distance of separation since they are inversely proportional to somewhere between the fourth and seventh power of the distance.

Thus, the weak of separating water molecules by a relatively large distance of on the formation of a micelle is little different from that involved in the introduction of an amphipathic monomer.

Ionic surface active agent:
The electrical repulsion between adjacent similarly charged ions tends to disrupt the micelles of an ionic surface active agent.

In such a case, micelle formation is therefore dependent on the balance between this disruptive effect and the constructive “squeezing out of solution” effect.

Nonionic micelles:
Since, the electrical repulsive effect is absent in non-ionic micelles. Various suggestions have been made regarding the existence of a factor that would tend to oppose micelle formation for example cross sectional area and solvation of the hydrophilic group.

However, the precise nature of such a factor is still in doubt.

Association of ionic and non-ionic surface active agents:
The association of ionic and nonionic surface active agents is also aided by the “hydrophobic bonding” between the hydrocarbons chains.

This type of bonding involves vander waals forces of attraction, the effect of which is therefore of less significance than those mentioned previously.

In addition, an increase in temperature will have a disruptive effect on the formation of micelles since their rate of deaggregation will be increased.

The size of a spherical micelle depends on the structure of the surface active agent. In the model of the micelle, the radius is approximately equal to the length of the hydrocarbon chain.

If the diameter were to increase beyond this point then the unlikely structure would either include a space in the centre into which the hydrocarbon chains could not reach or the presence of some of the ionic groups between the hydrocarbon chains.

References:

H. B. Klevens. Critical micelle concentration as determined by refraction. The journal of physical chemistry, 1948.

Further Reading:

Dynamics of Surfactant Self-Assemblies: Micelles, Microemulsions, Vesicles and Lyotropic Phases (Surfactant Science) by Raoul Zana

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Chitosan

Chitosan is a product made from chitin. A type of starch found in the skeleton of crustaceans. It is a natural polysachharide and is being widely used as an excipient in pharmaceutical preparations (A. K. Singla et al.). (RINAUDO Marguerite et al.) Chitosan is derived from Chitin.

Properties:
(RINAUDO Marguerite et al.) Chitosan is soluble in acidic aqeous media. (Alberto Di Martino et al.)Its gelling properties make it suitable for pharmaceutical agents in a controlled fashion. Due to its cationic nature it is favourable to be used in orthpaedic tissue engineering. (Shirui Mao et al.)Chitosan having molecular weights which is large are more prone to depolymerization as it depends on the molecular weight.

References:
Alberto Di Martino, Michael Sittinger and Makarand V. Risbud. Chitosan: A versatile biopolymer for orthopaedic tissue-engineering. Journal of Biomaterials, Volume 26, Issue 30, October 2005, Pages 5983-5990

A. K. Singla, M. Chawla. Chitosan: some pharmaceutical and biological aspects–an update. Journal of Pharmacy and Pharmacology , Volume 53, Number 8, 1 August 2001 , pp. 1047-1067(21)

RINAUDO Marguerite. Chitin and chitosan : Properties and applications. Journal of Progress in polymer science, 2006, vol. 31, no7, pp. 603-632

Shirui Mao, Xintao Shuai, Florian Unger, Michael Simon, Dianzhou Bi and Thomas Kissel. The depolymerization of chitosan: effects on physicochemical and biological properties. International Journal of Pharmaceutics, Volume 281, Issues 1-2, 20 August 2004, Pages 45-54

Further Reading:
Frequently Asked Questions: All About Chitosan by Carol N. Simontacchi

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Sulphonamides

Sulphonamides belong to the anti-infective class of drugs.

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Four parameters to be studied in the rabbit's eye experiment in pharmacology

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Acetylcholine

A short illustrated figure for "Acetylcholine".

References:
Remington: The Science and Practice of Pharmacy
Textbook of Medical Physiology by Arthur C. Guyton and John E. Hall
Further Reading:
Rang & Dale's Pharmacology by Humphrey P. Rang, Maureen M. Dale, James M. Ritter and Rod Flower
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Acrylic acid

The Merriam-Webster Dictionary has defined Acrylic Acid as:

"an unsaturated liquid acid C3H4O2 that polymerizes readily to form useful products (as constituents for varnishes and lacquers)".

Other names[2]:
1. 2-Propenoic Acid.
2. Glacial acrylic acid.
3. Propene acid
4. Vinylformic Acid.
5. Acroleaic Acid.
6. Ethylene carboxylic acid.

7. Acide acrylique (French). [3]

8. Acido acrilio (Spanish).

9. Kyselina akrylova(Czech).

Properties of Acrylic Acid:

1. Boiling Range is 143 C and m.p. is 13 C. [1]
2. Solubility at 25 C in Water (parts/100) is infinity.
3. Solubility of water at 25 C, (parts/100 monomer) is infinity.
4. Formula of Acrylic acid is CH2=CH-(C=O)-OH.
5. It is a colourless liquid. [2]
6. Its odor is Acrid and odor threshold is 0.1 ppm.
7. Its vapour pressure is 4 mmHg at 20 C.
8. Its refractive index is 1.4224.
9. Its density is 1.049 g/cc at 20 C.

Preparation of Acrylic Acid:[2]
(oxidation) (oxidation)
1: Propylene -----------------> acrolein -----------> Acrylic Acid.

2. Reppe Process:
( nickel halide salt )
Acetylene + Carbon Monoxide + Water ---------------------> Acrylic Acid + H2.

( Hydrolysis )
3. Acrylonitrile ----------------------> Acrylic Acid

Uses of Acrylic Acid: [2]
It is used in the manufacture of certain esters, resins and salts. The polymeric emulsions prepared from Acrylic Acid are used in the coatings for leather, in paints, polishes and adhesives, and in photographic emulsions. It is used for the formation of polyacrylic acid gels, which are a form of polyanionic hydrogels [4].

References:
[1] Encyclopedia of Chemical Processing and Design: Volume 39 - Pollution: Air: Costs: Part 1. Parameters for Sizing Systems to Polymers: Polyamides: Aliphatic
By John J. McKetta, William A. Cunningham

[2] Health Effect Assessments of the Basic Acrylates (Basic Acrylic Monomer Manufacturers Association) by Elizabeth K. Hunt

[3]http://www.chemicalland21.com/industrialchem/functional%20Monomer/ACRYLIC%20ACID.htm#

[4] Encyclopedia of Surface and Colloid Science, Second Edition (Eight-Volume Set) By Ponisseril Somasundaran, Published by CRC Press, 2006, ISBN 0849396050, 9780849396052, 822 pages.

Further Reading:
Acrylic Acid (Environmental Health Criteria)

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