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Platelets / Thrombocytes

Introduction: Platelets are also called as thrombocytes. Size: they are very small discs with diameter varying from 1 to 4 micrometers. The normal concentration of platelets in the blood is between 150,000 and 450,000 per microliter. Formation: They are formed in the bone marrow from megakaryocytes. The latter are extremely large cells in the marrow and they fragment into the minute platelets either in the bone marrow or soon after entering the blood. Destruction: The platelet has a half-life in the blood of 8 to 12 days. Then it is eliminated from the circulation mainly by the tissue macrophage system. More than one half of the platelets are removed by macrophages in the spleen, where the blood passes through a latticework of tight trabeculae. Platelets do not have nuclei and cannot reproduce. Yet, they have many functional characteristics of whole cells. 1) Actin and myosin molecules are present in their cytoplasm. They are contractile proteins similar to those found in

Statins and muscle weakness

Muscle weakness is a well known side effect of statin use. This symptom is very commonly ignored both by the patients and the doctors. Recent studies suggest that the higher potency statins i.e the ones causing a bigger drop in cholesterol/mg of active product are also the ones more likely to cause muscle weakness as a side effect. In order of potency the statins are as followed : 1) Rosuvastatin 2) Atorvastatin 3) Simvastatin 4) Pravastatin 5) Lovastatin So, it is always better not just to look at the altered hepatic functions during follow up visits. Do ask about the adverse side effects also and use a less potent statin if required.

Colchicine - complete information

Introduction: Colchicine is an alkaloid isolated from the autumn crocus, Colchicum autumnale. It is actually present in the corm of the plant, the underground swollen part of the stem. Pharmacokinetics: Colchicine is absorbed readily when taken in orally. It reaches peak plasma levels within 2 hours.  It has a serum half-life of 9 hours.  Colchicine is partially deacetylated in the liver and the unchanged drug and its metabolites are excreted in the bile and undergo intestinal reabsorption. Colchicine is found in high concentrations in leucocytes, kidneys, the liver and spleen. Most of the drug is excreted in the feces but 10 to 20% is excreted in the urine and this proportion rises in patients with liver disorders. For patients with creatinine clearance of < 50 mL/min, colchicine must be avoided or used at a lower dose. Colchicine is also distributed into breast milk. Pharmacodynamics: Colchicine relieves the pain and inflammation of gouty arthritis in 12-24 hou

Pulmonary embolism due to metallic mercury

Above is a chest radiograph of a schizophrenic patient. He was delusional about being a doctor. He used to read a lot of medical books and mastered the art of taking blood pressure. During an episode of psychosis, he broke the blood pressure apparatus and injected the mercury into his vein. We can see in the X-ray that there is micro-embolism of the liquid mercury to the pulmonary arterioles, mostly to the dependent areas and the arrow indicates a small pool of the mercury in the right ventricle.

Popliteal artery cyst

This is a popliteal arteriogram of a 27 year old male who presented with pain in left calf when exercising. Signs of deep vein thrombosis were negative but there was minimal swelling at the left ankle. A palpable pulsatile mass could be felt on the popliteal fossa. On arteriography a filling defect was obtained as shown in the picture above. CT scan confirmed that the cyst was within the popliteal artery wall.

Insulin - Structure

Insulin is a protein hormone. It was the first protein to be shown to have a precisely defined amino acid sequence. This work was done by Federick Sanger in 1953.  As shown above in two colours, the insulin molecule consists of 2 peptide chains.  a) The blue coloured chain is the A chain. It has 21 amino acids and a sisulphide bond within itself.  b) The yellow colour represents the B chain. It is larger with 30 amino acids.  Both chains are connected by 2 disulphide bridges.  Porcine and bovine insulins differ from human insulin at 1 and 3 positions of the amino acids respectively.