Section 3 Medical Literature 第三部分 医学文献
Part 1.
Whatever factors are given as the causes of cancer,the underlying cause of all cancer is DNA or RNA mutation.DNA is the substance of genes that contains the hereditary1) traits for an organism.DNA’s two basic functions are cellular replication and protein synthesis.When cell division occurs，each DNA molecule，which resembles a double spiral，unwinds，and each DNA strand serves as a pattern or mold called a template for the formation of a double set of a new DNA strand.The result is two pairs of spirals.This replication occurs in all genes and results in the formation of a double set of chromosomes2),one set for each new cell.The other function of DNA is protein synthesis.DNA itself is made from a sequence or pattern of four bases.These bases are adenine3),guanine4),cytosine5),and thymine6).The arrangement of these bases on the DNA molecule determines the proteins that each cell can produce.We call this arrangement of bases on DNA the genetic code.To carry out protein synthesis，DNA manufactures a messenger，RNA(ribonucleic acid)，which enters the cytoplasm and attaches itself to the ribosomes(where protein is synthesized)located on the endoplasmic reticulum7).The sequence of the bases on the messenger RNA established the pattern for the arrangement of amino acids(substances that make up proteins),thus determining the type of protein and enzymes(complex proteins that each cell can manufacture)therefore any mutation8) of the DNA molecule or RNA messenger alters the arrangement of the amino acids，which results in the production of different proteins by the cell.Consequently，the affected cells grow differently and lack of differentiation characteristics of normal cells.
注释：
1）hereditary 遗传的
2）chromosome 染色体
3）adenine 腺嘌呤，维生素B4
4）guanine 鸟嘌呤
5）cytosine 胞嘧啶
6）thymine 胸腺嘧啶
7）endoplasmic reticulum 内质网
8）mutation 突变
Part 2.
Response of living tissues to injury,resulting in such a series of changes as exudate,degeneration1) and regeneration.The changes may last for hours，days or weeks.The term of inflammation is derived from Latin which means to burn.
The injury is abnormal，but the body’s reaction，inflammation，is normal，if complex,physiological reaction—the only one possible in the circumstances of that particular injury.This reactive nature of inflammation was first recognized by John Hunter(1794)，who，after his studies of war wounds，concluded：“Inflammation is itself not to be considered as a disease,but as salutary operation consequent either to some violence or some disease.”
Many different types of injury may evoke inflammation.They may be classified as follows:
(1)physical agents,such as excessive heating or cooling,ultraviolet or ionizing radiation or mechanical trauma.
(2)chemical substances，including toxins from various bacteria.(https://www.daowen.com)
(3)hypersensitivity reactions.The reaction of antibody or of sensitized lymphocytes with bacterial or other antigens may，by the mechanism of hypersensitivity，release substances which cause an inflammatory response.
(4)microbial i nfections2) are a very important cause of inflammation.Micro-organisms may injure tissue in several ways by release of exo-or endotoxins,by hypersensitivity mechanisms or by intracellular multiplication followed by cell death as seen in many viral infections.
(5)necrosis3) of tissue from almost any cause leads to release of substances which induce inflammation in adjacent living tissues.
Microscopically,the usual sequence of the acute inflammation is as the following:
(1)Momentary arteriolar construction.
(2)Dilation of arteriolar，capillaries and venules.
(3)Increased permeability of vessel walls.
(4)Exudation of a protein-rich inflammatory fluid-exudate.
(5)Hemoconcentration due to fluid loss into tissues but intravascular retention of most of the red cells.
(6)Margination of the leukocytes which leave the axial stream，pass into the plasmatic zone and pavement the endothelial surface.
(7)Emigration of white cells and diapedesis of red cells through the vessel walls.
(8)Chemotaxis of polymorphonuclear leukocytes.
(9)Phagocytosis of organisms by the polymorphs.
(10)Appearance of phagocytic histocytes-macrophages.
注释：
1）degeneration 退化，变性
2）microbial infections 微生物感染
3）necrosis 坏死，细胞坏死，骨疽