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Gram staining - Procedure, mechanism, explanation

 INTRODUCTION  The Gram stain was developed in 1884 by the Danish bacteriologist Hans Christian Gram. It is one of the most useful staining procedures because it classifies bacteria into two large groups:  1) gram-positive and  2) gram-negative.  PROCEDURE  1) A heat-fixed smear is flooded with a basic purple dye, usually crystal violet. Because the purple stain imparts its color to all cells, it is referred to as a primary stain . 2) After 1 minute, the crystal violet is drained off and washed with distilled water. The smear is then covered with Gram's iodine, a mordant or helper . When the iodine is washed off, both gram-positive and gram-negative bacteria appear dark violet or purple. 3) Next, the slide is washed with alcohol (95% ethanol) or an alcohol-acetone solution. This solution is a decolorizing agent which removes the purple from the cells of some species but not from others. When the procedure is carried out, the slide is held at an angle and 95% ethanol is

Differences between hyperemia and congestion

Hyperemia and congestion both indicate a local increased volume of blood in a particular tissue. Hyperemia is an active process that result from augmented blood flow due to arteriolar dilation (e.g. at sites of inflammation or in skeletal muscle during exercise). The affected tissue is redder than normal because of engorgement with oxygenated blood. Congestion, on the other hand, is a passive process resulting from impaired venous return out of a tissue. It may occur due to systemic causes like cardiac failure or a local cause like isolated venous obstruction. The tissue is cyanosed because the worsening congestion leads to accumulation of deoxygenated hemoglobin in the affected tissues. 

Third degree atrioventricular block / Complete heart block - ECG

Third degree atrioventricular block is also known as complete heart block because there is complete failure of conduction between the atria and the ventricles. As a result of this there is complete independence between atrial and ventricular contractions. It is thus one type of AV dissociation. The classic characteristics of a complete heart block ECG are as follows : 1) P waves are present and the atrial rate is faster than the ventricular rate, 2) QRS complexes are present and are usually much slower than normal,  3) the P waves bear no relation to the QRS complexes and thus the PR intervals are completely variable. Since there is a block in the conduction, a subsidiary pacemaker will take over the function to make the ventricles contract. Depending at the level of block we can have different QRS complex morphologies.  Below is an ECG showing a complete heart block with the block occurring proximal to the His bundle, usually in congenital cases. The QRS complexes

Romberg's test - how to do and interpretation

 INTRODUCTION  Romberg's test is done to assess the integrity of the dorsal columns of the spinal cord. It is not a test to assess the cerebellar function. The test was first described by Moritz Heinrich von Romberg who found that patients with tabes dorsalis (neurosyphilis) often complained of increased unsteadiness in the dark. The test should be performed in all patients who complain of dizziness, imbalance or falls to rule out sensory ataxia.  HOW TO DO THE TEST?  The test is done by requesting the patient to keep his feet firmly together, arms by the side and the eyes open at first. The balance of the patient is noted. Now the patient is asked to close both eyes and the balance is now noted for around 1 minute. The physician should stand in front of the patient with his arms extended on either side of the patient but not touching him. This is done as the latter may fall.  INTERPRETATION  1) If with the eyes open, the balance is not good then there may be a probl

Retropharyngeal abscess - X-ray

Retropharyngeal abscess is a rare condition presenting in infants (<1 year of age). Clinical symptoms include fever and drooling.  As a result of the swelling within the posterior pharyngeal wall causing upper airway obstruction, the child will typically hold their neck in extension to assist breathing.  A lateral soft tissue neck radiograph taken with the neck held in extension is indicated if a retropharyngeal abscess is suspected. If it is positive, it will demonstrate air within the swollen retropharyngeal tissues, as shown by the x-ray above. A contrast enhanced computerized  tomography (CT) examination will confirm the diagnosis.

Difference between factitious disorder and malingering

Persons with factitious disorder fake illness. They simulate, induce, or aggravate illness. They also often inflict painful and even life-threatening injury on themselves or those under their care. Unlike malingerers who have material goals, such as monetary gain or avoidance of duties, patients with factitious disorder bear the sufferings primarily to gain the emotional care and attention that comes with playing the role of the patient. The disorders have a compulsive quality, but the behaviors are considered voluntary in that they are deliberate and purposeful, even if they cannot be controlled.