Chemotherapy mechanisms associated

Table 1 Mechanisms Associated with Chemotherapy Related Resistance ...

Mechanism of Action A S-HT, receptor antagonist that acts centrally in the chemore-ceptor trigger zone and peripherally at the vagal nerve terminals. Therapeutic Effect Prevents nausea and vomiting associated with chemotherapy. 

Welwistatin also inhibits cell proliferation with reversible depletion of cellular microtubules in ovarian carcinoma cells and A-10 vascular smooth muscle cells by inhibiting the polymerization of tubulin, but it does not alter the ability of tubulin to bind [3H]colchicine or to hydrolyze GTP [8]. Due to the cytotoxicity associated with the inhibition of tubulin polymerization, which is the main mechanism of action of antitumor drugs such as vincristine and vinblastine, and because P-gp-overexpressing cells show virtually no resistance to welwistatin due to its MDR reversal properties, this natural product could be a good candidate in the chemotherapy of drug-resistant tumors. 

A variety of tumours, e.g. oat-cell limg cancer, can make vasopressin, and of course they are not subject to normal homeostatic mechanisms. SIADH also occurs in some CNS and respiratory disorders (infection). Dilutional hyponatraemia follows, i.e. low plasma sodium with an inappropriately low plasma osmolality and high urine osmolality. When the plasma sodium approaches 120 mmol/I treatment should be with fluid restriction (< 500 ml/day). Treatment is primarily of the imderlying disorder accompanied by fluid restriction. Chemotherapy to the causative tumour or infection is likely to be the most effective treatment. Demeclocycline, which inhibits the renal action of vasopressin, is useful Infusion of isotonic or hypertonic saline must be reserved for extreme emergencies, associated with stupor, and undertaken with great caution. Rapid correction of hyponatraemia must be avoided because of the risk of central pontine myelinolysis the rate of correction must not exceed 12 mmol/1 per 24 h. 

Hepatitis B virus (HBV) is widespread throughout human populations, specially in Asia and Africa, and it has been estimated that over 200 million carriers exist, some of whom are eventually expected to develop liver carcinoma or cirrhosis. HBV shows a strict tropism for liver hepatocytes in which it displays a protected replication with resultant foci of liver necrosis. The virus is a member of the Hepadnaviridae, along with several other species, and it replicates by a mechanism which appears to be unique to this family. In contrast, hepatitis A virus is a picornavirus and the hepatitis D agent appears to be a viroid-like RNA enclosed within a hepatitis B capsid, and consequently depends upon its association with the HBV for its spread and survival. Control may be effected by passive immunization (with hyperimmune globulin) or by various types of vaccines which are currently being developed and improved. Specific chemotherapy has not been consistently successful, but in some countries (e g., India and China), plant extracts have provided some success. 

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