Bacterial and Viral Meningitis

Introduction :
Infection of the membrane (meninges) that covers the brain and spinal cord.


Types :
Bacterial (septic) and viral (aseptic) infections may occur.


Cause :
Between the brain and the skull is a fibrous sheet of material called the meninges. The meninges wrap all the way around the brain, and act to contain the fluid in which the brain is supported (the cerebrospinal fluid - CSF), and to protect the brain. If the meninges become infected, the patient is said to suffer from meningitis. If the brain itself is infected, the patient has encephalitis. Viral (or aseptic) meningitis is a relatively benign condition that may be caught like any other viral infection, or be a complication of diseases such as mumps, glandular fever and herpes. Bacterial meningitis is a much more serious condition, with the severity and symptoms varying depending upon which type of bacteria is infecting the meninges. These bacterial infections are caught from people who are carriers of the bacteria, but the victims are usually weak, ill, under stress or have their ability to resist infection reduced in some way.


Incidence :
Viral meningitis is uncommon, while bacterial meningitis is rare, but occurs in epidemics every decade or so.


Prevention :
One of the most common forms of bacterial meningitis caused by Haemophilus influenzae B (HiB) can be prevented by a vaccine. Viral meningitis that occurs as a complication of mumps can also be prevented by vaccination. Other forms of bacterial and viral meningitis cannot be prevented.


Investigations :
The diagnosis of both types of meningitis is confirmed by taking a sample of cerebrospinal fluid and examining it under a microscope for the presence of certain cells. The sample is taken by putting a needle into the lower part of the back in a procedure called a spinal tap. The spinal cord is an extension of the brain that runs down from the head through the vertebrae. The spinal cord is also surrounded by meninges, and cerebrospinal fluid. As well as examining the cerebrospinal fluid for cells, it can be cultured to find the exact bacteria that is causing the infection. Blood tests also show abnormalities. Health Record

Course :
The patient with viral meningitis experiences fever, headache, nausea and vomiting, tiredness and rarely muscle weakness or paralysis. Doctors may note that the patient has a stiff neck. In bacterial meningitis, patients experience severe headaches that are aggravated by bright lights, loss of appetite, vomiting, drowsiness, confusion, high fevers, become delirious, unconscious and may convulse. A child may be difficult to wake and have a high pitched moaning cry. Some types of bacterial meningitis are accompanied by a red-purple rash or bruises on the skin and inside the mouth. Neck stiffness is quite obvious, and patients may lie with their neck constantly extended as though they are looking up. Medical Guide


Treatment :
There is no specific treatment available for viral meningitis. Bed rest, good nursing, paracetamol, and sometimes medication for vomiting is all that is normally required. The treatment of bacterial meningitis involves giving the appropriate antibiotic in high doses, usually by injection or a continuous drip into a vein. Other serious effects of the infection must also be treated, and these patients always require hospitalisation.


Complications :
Despite the best treatment, a number of complications are possible from bacterial meningitis. These can include permanent deafness in one or both ears, damage to different parts of the brain, heart or kidney damage, arthritis and the excess production of cerebrospinal fluid which can put pressure on the brain. A secondary bacterial infection of the blood stream (septicaemia) is another very serious complication. The worse complication is called intravascular coagulation, which results in the blood clotting within the arteries and blocking them. This may cause the loss of limbs due to gangrene and is frequently fatal.


Outcome :
Patients with viral meningitis will recover in one or two weeks, and it is rare for there to be any after effects. Bacterial meningitis is always very serious, with significant complications occurring in many patients. Patients may deteriorate very rapidly, and most deaths occur within the first 24 hours. The overall mortality rate is about 20%, but is higher in children.


Related conditions :
HiB.

How Chromosomes are Labeled

There are 46 chromosomes, or 23 pairs of chromosomes, present in every cell except the eggs and sperm which have 23 chromosomes. Chromosomes 1 through 22 are referred to as autosomes. They are present in both males and females. The 23rd pair of chromosomes, referred to as the sex chromosomes, differ between the sexes. Females have two copies of the X chromosome, one from each parent. Males receive an X chromosome from the mother, and a Y chromosome from the father.

Chromosome analysis requires growing cells in culture and harvesting dividing cells. Chromosomes are arranged into a karyotype based on size, shape and banding pattern. Conventionally, twenty cells are analyzed for chromosome count and morphology.

Different staining techniques can be used to analyze the chromosomes. Routine chromosome studies are done using trypsin-Giemsa stain which results in the G-banding pattern. FISH studies are done to identify microdeletions or the origin of extra chromosome material.

detailed info

http://www.usd.edu/med/som/genetics/curriculum/1CHROM1.htm

death of Jesse Gelsinger

The chill set in on 17 September 1999. That's when Jesse Gelsinger, a young volunteer, died in a gene therapy trial at the University of Pennsylvania in Philadelphia, triggering a blitz of media and government attention. The Food and Drug Administration (FDA) has issued Penn a warning letter and shut down all clinical trials at Penn's Institute for Human Gene Therapy while it investigates what happened. The chill intensified last week when FDA made public a warning letter to cardiac specialist Jeffrey Isner of St. Elizabeth's Medical Center in Boston, alleging infractions of FDA rules in a gene therapy trial for heart disease in which one patient's cancer could have been exacerbated by the treatment and, FDA contends, a death was not properly reported. Isner's studies are now on hold. FDA also halted several other gene therapy trials around the country last winter while investigating vector toxicity.

for detailed information about gene therapies
http://www.sciencemag.org

polytene chromosome (2)

The giant chromosomes of Drosophila appear to be composed of many chromonemata or strands and are known as polytene chromosomes. Such chromosomes are characteristics of the cells of salivary glands, intestine, gastrocaecum, and Malpighian tubule of certain insects. They are the result of a specialized process known as endomitosis. During this process, there is no cell division, but the cells grow larger. The chromonemata (strands of DNA with the corresponding RNA and histones) replicate several times during the life cycle of the organism without separating from each other. The newly formed elements remain together with the old ones and behave as a unit. This leads to polyteny or multistrandedness; in addition, the two homologs of each chromosome pair remain permanently synapsed and are considered to be in perpetual interphase. Because of this synapsed nature, chromosome alterations, such as inversions, deletions, and translocations, are readily recognized.
The most commonly observed modification or change in polytene chromosomes is a localized increase in diameter, called a puff. Puffs appear at different physiological stages of development and tend to involve only a single band of the 300 to 400 or so cross bands of a given chromosome. Different individuals of Drosophila usually have identical banding patterns for particular chromosomes. Single band differences between homologous chromosomes, which are paired in salivary glands, can be detected with certainty. The construction of cytological chromosome maps was based on this consistency of the banding patterns. A polytene chromosome has both deep-staining banded regions and nonstaining interband regions. Using Feulgen staining or autoradiography, it has been shown that the DNA resides in the deep-staining banded regions. This led to the first cytological demonstration of the fact that giant chromosomes consist of linearly arranged and independently reactive genetic units. In other words, bands, or less probably interbands, are possibly genetic loci. This is in keeping with the idea that different tissues are capable of performing diverse physiological functions, although they all contain the same complement of DNA, and that not all genes are active at the same time in any one tissue or any one cell. In the polytene chromosomes, this is clearly illustrated by the fact that different loci puff independently of one another in the same as well as in different tissues.
A puff is believed to be caused by the loosening or uncoiling of the strands in a particular band and interpreted as an indication of genetic activity. Puffs are differentially active in RNA synthesis, as there is a direct correlation between the size of a puff and the amount of
RNA produced by it. Nonpuffed areas of the chromosome are also physiologically active, a detected by the rate of incorporation of RNA and DNA precursors (tritriated uridine and thymidine, respectively). A puff manifests itself by a higher level of RNA precursor uptake, thus a higher level of transcription. The present theory is that uncoiling in the puffed region exposes more DNA strands and frees them to be transcribed by RNA polymerase into mRNA.
A disproportionate synthesis of DNA has been demonstrated in certain bands during and after the termination of puffing than any time prior to a puff in that area of the chromosome. This increased DNA synthesis is called ‘metabolic DNA’ and is defined as any DNA which is produced by the multiplication of chromosome loci, either in excess of or independent of the process of normal chromosome multiplication.

Polygenic Inheritance (2)

Human examples of polygenic traits include skin color, stature, and intelligence as measured by IQ tests. In this investigation, you will explore how the trait of total fingerprint ridge count illustrates the polygenic model of inheritance.
Fingerprint patterns of dermal ridges can be classified into three major groups: arches, loops, and whorls. The arch is the simplest and the least frequent pattern. It may be subclassified as ‘plain’ when the ridges rise slightly over the middle of the finger or ‘tented’ when the ridges rise to a point. The loop pattern has a triradius and a core. A triradius is a point at which three groups of ridges, coming from three directions, meet at angles of about 120 degrees. The core is essentially a ridge that is surrounded by fields of ridges, which turn back on themselves at 180 degrees. Loops can be either radial or ulnar. A finger possesses a radial loop if its triradius is on the side of the little finger for the hand in question, and the loop opens toward the thumb. A finger has an ulnar loop if its triradius is on the side of the thumb for that hand and the loop opens toward the little finger. The whorl pattern has two triradii, with the ridges forming various patterns inside. The frequencies for these fingerprint pattern types in general population are as follows: arch, 5.0%; radial loop, 5.4%; ulnar loop 63.5%; and whorl, 26.1%.
The focus of this investigation is the polygenic or quantitative trait called the total ridge count (TRC), the sum of the ridge counts for all 10 fingers. The average TRC for males is 145 and that for females is 126. For an arch, the ridge count is 0. The ridge count on a finger with a loop is determined by counting the number of ridges between the triradius and the center or core of the pattern. For a whorl, a ridge count is made from each triradius to the center of the fingerprint, but only the higher of the two possible counts is used.

Random Amplified Polymorphic DNA

RAPD analysis is carried out in the organisms in which their sequence information is unavailable. In this technique, sequence of PCR primers are random. These PCR primers can be used individually or in pairs during PCR reactions. They consist of 8-10 nucleotides. They often hybridize with DNA at multiple sites. If primers hybridize in the proper orientation and a suitable distance from each other, the fragment between these primers can be amplified. In RAPD analysis, a genomic DNA yields many bands on electrophoresis gel. Only some of the bands are polymorphic, presence or absence of amplified fragment in the population. If the amplified bands are detected in every organism, these bands are called monomorphic.In RAPD analysis, it is very diffucult to determine amplified DNA fragments of same size because they often result darker bands. RAPD primers are so small so they may not match DNA perfectly. Becaue of this light bands occur.

Restriction Fragment Length Polymorphisms

A change at a nucleotide site that eliminates a restriction site is called restriction fragment length polymorphism. RFLPs can be analyzed with Southern Blotting because RFLPs makes a change in the number and size of fragments cleaved by restriction enzymes. Alleles differ in the presence or absence of cleavage site. If both alleles present in DNA, 2 different bands can be detected. Codominance occurs in RFLPs because heterozygous genotype has both bands that can be detected in both homozygous alleles.RFLP analysis is useful for genetically well studied animals because RFLPs can be analyzed with using southen blotting and PCR techniques. Southern blotting requires probes in the form of cloned DNA and PCR requires sequence information.