I want to help you guys - rachana

[ArchivalUser]

Zero Order Elimination
Why if I have 10 pints of beer before midnight will I fail a breathalyser test at 8 am the following morning? Either this is due to alcohol having a very long half life (which it does not) or that alcohol is cleared in a different way.
What happens is that the metabolic pathways responsible for alcohol metabolism are rapidly saturated and that clearance is determined by how fast these pathways can work. The metabolic pathways work to their limit. This is known as zero order kinetics: a constant amount of drug is eliminated per unit time. This form of kinetics occours with several important drugs at high dosage concentrations: phenytoin, salicylates, theophylline, and thiopentone (at very large doses). Because high dose thio is very slow to clear, we no longer use it in infusion for status epilepticus (as it takes ages for the patient to wake up!).

[ArchivalUser]

Primary Brain Tumors
Tumors that begin in brain tissue are known as primary brain tumors and are classified by the type of tissue in which they originate. The most common brain tumors are gliomas, which begin in the glial or supportive tissue. There are several types of gliomas:
¢Astrocytomas ” These tumors arise from small, star-shaped cells called astrocytes. They may grow anywhere in the brain or spinal cord. In adults, astrocytomas most often arise in the cerebrum. In children, they occur in the brain stem, the cerebrum and the cerebellum. A grade III astrocytoma is sometimes called anaplastic astrocytoma. A grade IV astrocytoma is usually called glioblastoma multiforme.
¢Brain stem gliomas ” These tumors occur in the lowest, stem-like part of the brain. The brain stem controls many vital functions. Most brain stem gliomas are high-grade astrocytomas.
¢Ependymomas ” These tumors usually develop in the lining of the ventricles. They may also occur in the spinal cord. Although these tumors can develop at any age, they are most common in childhood and adolescence.
¢Oligodendrogliomas ” These tumors occur in the cells that produce myelin, the fatty covering that protects nerves. These tumors usually arise in the cerebrum. They are rare, grow slowly and usually do not spread into surrounding brain tissue. They occur most often in middle-aged adults but have been found in people of all ages.

There are other types of brain tumors that do not begin in glial tissue. Some of the most common are described below:
¢Medulloblastomas ” These tumors were once thought to develop from glial cells. However, recent research suggests that these tumors develop from primitive or developing nerve cells that normally do not remain in the body after birth. For this reason, medulloblastomas are sometimes called primitive neuroectodermal tumors (PNET). Most medulloblastomas arise in the cerebellum; however, they may occur in other areas as well. These tumors occur most often in children and are more common in boys than in girls.
¢Meningiomas ” These tumors grow from the meninges, or membranes that enclose the brain and spinal cord. They are usually benign. Because these tumors grow very slowly, the brain may be able to adjust to their presence. Meningiomas often grow quite large before they cause symptoms. They occur most often in women between 30 and 50 years of age.
¢Schwannomas ” These tumors are benign and begin in Schwann cells, which produce the myelin that protects the acoustic nerve, or the nerve of hearing. They occur mainly in adults. These tumors affect women twice as often as men.
¢Craniopharyngiomas ” These tumors develop in the region of the pituitary gland near the hypothalamus. They are usually benign but are sometimes considered malignant because they can press on or damage the hypothalamus, a region of the brain, and affect vital functions. These tumors occur most often in children and adolescents.
¢Germ cell tumors ” These tumors arise from developing sex cells or germ cells. The most frequent type of germ cell tumor in the brain is the germinoma.
¢Pineal region tumors ” These tumors occur in or around the pineal gland, a tiny organ near the center of the brain. The tumor can be slow growing (pineocytoma), or fast growing (pineoblastoma). The pineal region is very difficult to reach, and these tumors often cannot be removed.

Secondary Brain Tumors
Metastasis is the spread of cancer. Cancer that begins in other parts of the body may spread to the brain and cause secondary tumors. These tumors are not the same as primary brain tumors. Cancer that spreads to the brain is the same disease and has the same name as the original or primary cancer. For example, if lung cancer spreads to the brain, the disease is called metastatic lung cancer because the cells in the secondary tumor resemble abnormal lung cells, not abnormal brain cells.
Treatment for secondary brain tumors depends on where the cancer started and the extent of the spread as well as other factors, including the patient's age, general health and response to previous treatment.

[ArchivalUser]

thanx rachana.... appreciate all your effort....GL.

[ArchivalUser]

Great work rachana.. thanks a ton..
when are u planning to take the step1? i mite give it around may end-june..

tc

[ArchivalUser]

Iam not confident still to even fix a date for exam ...Iam doing masters in USA so busy with the course load but I just want to help to those who are preparing to save their time and also make myself to study ... Hope one day I will reach to your preparation level...

[ArchivalUser]

arey noo re.. i am still not confident,,, infact im too doing masters here ... and have a few presentations next mnth,, jus trying to push as much as i can this mnth an in may,, will review my prep mid may n decide,,
and its damn nice of u to take out time and answer these qns,,

YOU GO GIRL!

[ArchivalUser]

great !!!!!!!!!!!!
thanx rachana.
Would you explain about ---bacterial genetic material stuff like insertion,transposons, recombination, transformation, conjugation, transduction etc. I really have a hard time with microbial genetics and drug resistance.
thanks

[ArchivalUser]

Transduction ------ A method of gene transfer between bacteria in which the bacterial donor DNA is carried by a phage. There are two types of transduction: generalized transduction and specialized transduction. Generalized transduction can transfer of any region of the chromosome from the bacterial host into a recipient cell. Specialized transduction can only transfer regions of DNA adjacent to an integrated phage (prophage).
Transformation -------Transfer of naked donor DNA into a cell.
Transposition --------The movement of a discrete segment of DNA from one location in the genome to another.
Insertion -------- A fragment of DNA integrated into a cloning vector.
Conjugation ---- The establishment of a bridge between a donor and a recipient cell and the transfer of DNA from one cell to the other. Conjugation is mediated by certain plasmids and transposons. Conjugation requires direct contact between the donor and recipient cells.
Recombination ----- Genetic exchange resulting from a cross-over between two different DNA molecules or different regions of a DNA molecule

[ArchivalUser]

Genetic Insertion------ is the addition of one or more nucleotide base pairs into a genetic sequence. This can often happen in microsatellite regions due to the DNA polymerase slipping.
On a chromosome level, an insertion refers to the insertion of a larger sequence into a chromosome. This can happen due to unequal crossover during meiosis.
N region addition is the addition of non-coded nucleotides during recombination by terminal deoxynucleotidyl transferase.
P nucleotide insertion is the insertion of palindromic sequences encoded by the ends of the recombining gene segments

[ArchivalUser]

Thanks Rachana>>>