AIDS and related diseases

This condition was first recognized in the United States in 1981.There was a huge number of patients with Pneumocystis carinii pneumonia recorded during that period. Center for Disease Control and Prevention (CDC) reported the unexplained occurrence of Pneumocystis carinii pneumonia in previously healthy adult males. Later they were found to be as homosexuals. There was a another set of previously healthy homosexual men developed Kaposi's sarcoma during the same period. Because of this unusual occurrence of above two conditions, health professional have done many investigations and they have found that above affected males were immunocompromised.
Human Immunodeficiency virus was isolated from a blood sample a patient with lymphadenopathy in 1983.The scientists were able to demonstrate that this virus was the causative agent of AIDS, exactly one year after its isolation .In 1985 they were able to develop an investigation to identify the virus. This investigation is known as Enzymelinked immunosorbent assay (ELISA).today this investigation is used as a screening test whereas the investigation called “western blot” is used as the confirmatory test.
Modes of transmission include unsafe sexual behaviors, transfusion of blood and blood products and vertical transmission ( from mother to fetus/baby).still nobody was able to find an effective treatment for this condition. Therefore best thing is the prevention.

Forensic uses of Diatom

The most frequent application of diatoms in forensic science is in the diagnosis of death by drowning. Drowning is a very common accidental and suicidal cause of death, and thousands die each year in this fashion.

The word diatom literally means “ cut in to two”. Diatoms are a type of algae. There are 16000 species of diatoms have been found and recorded but there can be thousands of them yet to be found. These are unicellular organism and they can be found either as single cells or as colonies. The primary feature which is used to distinguish diatoms from other type of algae is the silicified cell wall. Diatoms are widely distributed in both fresh and salt water. Certain species of diatoms are only found in fresh water whereas others are only found in the salt water.

Drowning is the result of totally submersion or partially submersion in a fluid such as water. Mechanism of drowning is complex and is modified by the medium and other factors. In the majority, the inhalation of fluid, thereby obstructing the air passage, is the essential cause of death.

When a person is drowned, fluid containing various micro-organism and the other particles enter the lung. Through the lung these organisms enter the blood stream thereby travel to the various site of the body including liver, kidney and bone marrow. These organisms including diatoms can be isolated by using various tests. This will help to recognize the site of the drowning, time since death and to differentiate accidental drowning from suicidal one.

Plastination

Introduction

Plastination is a new method of preservation of perishable biological specimens, especially for soft, putriable ones with high water contents, for example whole organ like brain, heart, liver, lung and kidney. In zoology, you can also plastinate small animal like chicken embryos, spiders, amphibians and small reptiles. In botany the Plastination of fungus has already been developed for general use, while the plastination of higher plant specimens is still in the experimental stage.

During the plastination process the tissue water and the part of the tissue fat is replaced by polymerize resin. Once the polymerization has taken place inside the specimen, it provides a higher stability than that of freeze dried specimen and paraffined specimen.

History of plastination

This technique is developed at the University of Heidelberg’s Institute of Anatomy in 1977, patented it between 1977 and 1982, and have been continually improving the process ever since.

Even though a major German encyclopedia (the 19th edition of the Brockhaus Encyclopedia, 1992) indicates that the word "Plastination" is derived from the Greek (from plassein = to shape, to form), the term is, in fact, a creation of Gunther von Hagens. He coined the term because "plastification" already had a fixed meaning in the field of polymer chemistry, and the expression used in the original patents of 1977/78 ("Polymer Impregnation of Perishable, Biological Specimens”) was not terribly catchy and was utterly inadequate for popularizing the new technology, particularly abroad. The following will provide an explanation of how Plastination works.

Plastination is carried out in four steps

1. fixation and staining

2. dehydration

3. forced impregnation

4. curing

Fixation and staining

Fixation is carried out using normal fixation techniques such as using formaldehyde solution. Coloration is achieved by injecting colored epoxy resin into the vascular system. Fixed specimens may be stained by microscopic staining methods. Color preservation can be attained by short fixation or utilizing the chemical influence of polymer components of the impregnation bath.

Dehydration

Dehydration of the specimen is necessary prior to impregnation with polymers. The easiest method is freeze-substitution. The specimen is placed in acetone at -25 ºC for several weeks. The acetone is changed until the water content is below 1%.

Forced impregnation

The process of forced impregnation is the central and important step of plastination. After saturation the specimen with a medium of high vapor pressure (low boiling point), it is immersed in a suitable polymer solution whose components have a low vapor pressure (high boiling point). The acetone inside the specimen is removed continuously by a vacuum pump. As the medium is removed from the specimen, a pressure difference will be generated causing the polymer solution to be drawn into the specimen.

The impregnation should be carried out slowly as to allow the polymer solution to penetrate inside the specimen,by which the acetone changes to the gaseous phase and is removed(pumped out “of boiledoff’). The impregnation takes 4 to 14 days depending primarily on the size of the specimen, the density of the tissue and the viscosity of the polymer solution.

Curing

The curing of the impregnated specimen carried out at room temperature or at +50ºC depending on the nature of the polymer used. It is a special method as gas-cure, where the impregnated specimen is brought into contact with a gaseous medium in order to complte polymerization.

Uses

The plastinated specimens are easy to handle as there are no formalin present which causes irritation to the eyes and skin. The specimens are more harder and could not be damaged easily. They can also used for longer period of time.

Biosensors in food analysis

Contents

1. Introduction of biosensors
2. Technology (brief)
3. Electrochemical Biosensors
4. Piezoelectric biosensor
5. Thermometric biosensors
6. Optical biosensors
7. Food analysis and application of biosensors

Introduction of biosensors

Biosensors can be defined as an analytical device containing biological or biologically derived sensing elements. They can also be described as the offspring of biology and electronics. Multidisciplinary skills of biologists, physicists, chemists and engineers have been combined to produce biosensors. In a biosensor the analyte or the sensing element could be a bio catalyst such as an enzyme, organism, tissue or an affinity system such as an antibody, or a nucleic acid.

Technology

As a result of the development of the microprocessor applied technology and rapid growth of biotechnology, production and application of biosensors expanded dramatically. Quality assessment and ensuring compliance with legislation are the two basic needs of food analysis. Although human sense organs are sensitive, instruments provide better quantitative results than them. However conventional instrumental methods are incompatible in cases where quick results are needed. In addition to this, biosensors have various advantages as compared to conventional analytical methods. They are relatively cheap, easy to handle, portable and the user does not require special skills. The term biosensor is used for a whole class of sensors that utilize a biochemical reaction to determine a specific compound.

In a biosensor a bio-receptor molecule is immobilized in a suitable matrix to form a bio-layer which is then placed in the immediate vicinity of a transducer. Depending on the nature of the transducers and the transduced parameter, there are different types such as Electrochemical, Piezoelectric, and Thermometric and Optical biosensors in the analytical field.

Electrochemical Biosensors

An electrochemical biosensor is a self-contained integrated device, which is capable of providing specific quantitative or semi-quantitative analytical information using a biological recognition element (biochemical receptor) which is retained in direct spatial contact with an electrochemical transduction element.

Piezoelectric biosensor

The development of a piezoelectric biosensor based on nucleic acids interaction is presented focusing on the methodology for probe immobilization. This is a key step in any DNA biosensor development. Often, the detection limits and, in general, the analytical performances of the biosensor can be improved by optimizing the immobilization of the receptor on the transducer surface.

Thermometric biosensors

Thermometric biosensors are constructed by combining enzymes with temperature sensors. When the analyte is exposed to the enzyme, the heat of reaction of the enzyme is measured and is calibrated against the analyte concentration.

Optical biosensors

Optical Biosensors provides the most comprehensive analysis of optical biosensors and relevant technologies to date. According to the optical configuration, optical sensors have classified into two modes. When light is reflected at an optical interface where there is a change of refractive index, there is a decay of energy from the point of reflection into the surrounding medium. This energy field which extends into the medium depends upon the medium in which the wave guide is dipped. The resultant changes of luminescence, absorption or fluorescence can hence be determined. When the glass surface of the biosensor is coated with a thin layer of metal (silver, gold), the intensity of the resonance angle changes depending on the concentration of the medium in which electrode is immersed. This phenomenon is called the surface plasma resonance (SPR).

Food analysis and application of biosensors

Dietary habits of people throughout the world are different depending on the availability, ethnicity, cultural influences and the preparation and preferences for food. The range of food analytes comprises of liquid and gases as ionic radical or neutral species. The form of analyte may range from macromolecule to a microelement and heterogeneous distribution of analyte in the food has made the situation worse for the analyst. In most cases, the analyst needs to separate the analyte from the food before detection.

In food industry optic coated with antibodies are commonly used to detect pathogens and food toxins. The light system in these biosensors has been fluorescence, since this type of optical measurement can greatly amplify the signal. The exact wave length of this resonance depends on the amount of antibody, immobilized in the coupling matrix. The antibody-antigen interaction causes a shift in the resonance to longer wavelengths. The amount of the shift can be related to the concentration of antigens. The speed of detection is critical in preventing and diagnosing food related illnesses. It plays an important role in food processing plants by minimizing time gap between two unit operations. In conclusion, biosensors form an interesting part of food analysis, and they have achieved a notable success. However the have not yet reached their full potential and new products are being manufactured every movement.

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Non Alcoholic Steatohepatitis

This is a condition in which histological appearance of the liver is similar to the histological appearance of the alcoholic liver disease. But in this condition alcohol has no role to play. Therefore the term Non-alcoholic Steatohepatitis (NASH) was introduced to define this particular condition. This has happened in 1980. This condition is associated with obesity and type 2 diabetes mellitus. Bad aspect of this condition is that this can lead to the cirrhosis and ultimately into the Hepatocellular carcinoma. It is now clear that NASH is an important part of the metabolic syndrome, which also includes insulin resistance,obesity, hyperlipidaemia and hypertension.
According to the latest studies now it is well recognized that NASH is the most common cause of persistent elevation of liver enzymes (specially alanine aminotransferase (ALT)) in patients in whom no other obvious cause can be found.
Because of the development of the sophisticated technology and investigation methods this condition is diagnosed frequently. This is also partly due to high degree of awareness about this condition among physician as well.

Acromegaly

Acromegaly is a condition which occurs due to the hypersecretion of the Growth Hormone from the somatotrope adenoma. Acromegaly literally means enlarged fingers. Other lesions which can give rise to this condition are mixed mammosomatotrope tumors, acidophilic stem-cell adenomas and some extra pituitary lesions. Rare causes include mixed plurihormonal tumors and ectopic GH secretion by tumors of pancreatic,ovarian, or lung origin.
Typical features of this condition are frontal bossing, increased hand and foot size, mandibular enlargement with prognathism and widened space between the lower incisor teeth. They also have increased heel pad thickness due to the soft tissue swelling. Other commonly encountered clinical features include hyperhidrosis, deep and hollow-sounding voice, oily skin, arthropathy, kyphosis, carpal tunnel syndrome, proximal muscle weakness and fatigue, acanthosis nigricans, and skin tags.
Generalized visceromegaly occurs, including cardiomegaly, macroglossia, and thyroid gland enlargement.
Most of the time diagnosis of this condition is clinical. To confirm the condition, serum GH level can be done. MRI or CT scan of the brain is essential to locate the lesion. Usually mode of treatment is surgical .Now safe surgical procedures are available to remove the tumor.

MOLLUSCUM CONTAGIOSUM

The pox viruses include a large number of related DNA viruses that infect various vertebrate hosts. The pox viruses are responsible for infections in humans, along with the main manifestations of these infections. Systemic human disease can result from infection with smallpox (variola major) virus, a poxvirus that infects only humans or from zoonotic infection with monkey pox virus. Other poxvirus infections cause primarily localized skin disease in humans. Molluscum contagiosum virus (MCV) is an obligate human pathogen that causes distinctive proliferative skin lesions; Molluscum contagiosum is the most frequent human disease resulting from poxvirus infection. Exposure to animals infected with other poxviruses can also cause localized skin disease in humans.

Molluscum contagiosum is generally a benign disease consisting of pearly, flesh colored, and umbilicated skin lesions 2 to 5 mm in diameter with a characteristic dimple at the center. A relative lack of inflammation and necrosis distinguishes these proliferative lesions from other poxvirus lesions. The lesions occur singly or in clusters. MCV is a human poxvirus that is transmitted by close contact, including sexual intercourse. Swimming pools are a common vector for transmission. Atopy and compromise of skin integrity increase the risk of infection. Lesions may be found anywhere on the body except the palms and soles and may be associated with an eczematous rash. The incubation period ranges from 2 weeks to 6 months, with an average of 2 to 7 weeks. In most cases, the disease is self-limited and regresses spontaneously after 3 to 4 months in immunocompetent hosts. There are no systemic complications, but skin lesions may persist for 3 to 5 years. Molluscum contagiosum develops especially often in association with the advanced stages of HIV infection, with a prevalence of 5 to 18% among HIV-infected patients. The disease is often more generalized, severe, and persistent in AIDS patients than in other groups, frequently involving the face and upper body. Extensive Molluscum contagiosum has also been reported in conjunction with other types of immunodeficiency.

The diagnosis of Molluscum contagiosum is typically made by its clinical presentation and can be confirmed by histologic demonstration of the cytoplasmic eosinophilic inclusions, or Molluscum bodies, that are characteristic of poxvirus replication. MCV cannot be propagated in vitro, but electron microscopy and molecular studies can be used for its identification. There is no specific systemic treatment for Molluscum contagiosum, but a variety of techniques for physical ablation have been used. Molluscum contagiosum may respond to effective control of HIV infection with highly active antiretroviral therapy. Cidofovir displays in vitro activity against many poxviruses, including smallpox virus and MCV, and case reports suggest that parenteral or topical Cidofovir may have some efficacy in the treatment of recalcitrant Molluscum Contagiosum in immunosuppressed hosts.