Brain source

Genazzani, A.R., F. Pelraglia, and R.H. Purdy The Brain Source and Target for Sex Steroid Hormones. CRC Press, LLC, Boca Raton. FL, 1996. 

FIGURE 1 Cross section of the retina and other layers of the eye (choroid and sclera). The rods and cones are the photoreceptors that sense light. The other cells process this information and transmit electrical impulses via the optic nerve fibers to the brain. Source Image from http //www.catalase.com/retina.gif. 

Synthesis. In contrast to pituitary hormones, which usually can be obtained in pure form only after extraction from animal tissues, brain oligopeptides are readily available because of their small size. The synthetic repHca represents the most economical and readily accessible source for the oligopeptides. Two techniques are available for laboratory synthesis of oligopeptides, ie, solution chemistry and soHd-phase peptide synthesis (SPPS). 

Industrial lecithins from a variety of sources ate utilized (Tables 2 and 3). The main sources include vegetable oils (eg, soy bean, cottonseed, corn, sunflower, tapeseed) and animal tissues (egg and bovine brain). However, egg lecithin and in particular soy lecithin (Table 4) ate by fat the most important in terms of quantities produced. So much so that the term soy lecithin and commercial lecithin ate often used synonymously. 

Provitamin D. Provitamin is made from cholesterol, and its commercial production begias with the isolation of cholesterol from one of its natural sources. Cholesterol occurs ia many animals, and is generally extracted from wool grease obtained by washing wool after it is sheared from sheep. This grease is a mixture of fatty-acid esters, which contain ca 15 wt % cholesterol. The alcohol fraction is obtained after saponification, and the cholesterol is separated, usually by complexation with 2iac chloride, followed by decomplexation and crystallisation. Cholesterol can also be extracted from the spiaal cords and brains of animals, especially catde, and from fish oils. 

Urodilantin, a 32-amino acid natriuretic peptide synthesized by the kidney and found in urine but not in plasma, is beheved to compHcate the interpretation of the natriuretic effects of ANP (58). There have been reports of natriuretic peptides related to ANP that have been isolated from several sources, including the brain, eg, brain natriuretic peptide (BNP) [114471-18-0] (59—61). 

Fig. 10-2. Threshold contrast in distinguishing an object from its surroundings. The eye responds to an increment in light intensity by increasing the number of signals (pulses) sent to the brain. The detection of threshold contrast involves the ability to discriminate between the target (1) and the brighter background (/ + A/). Source Gregory, R. L., Eye and Brain "The Psychology of Seeing." Weidenfeld and Nicolson, London, 1977.

Ascorbic acid is photosensitive and unstable in aqueous solution at room temperature. During storage of foods, vitamin C is inactivated by oxygen. This process is accelerated by heat and the presence of catalysts. Ascorbic acid concentration in human organs is highest in adrenal and pituitary glands, eye lens, liver, spleen, and brain. Potatoes, citrus fruits, blade currants, sea buckthorns, acerola, rose hips, and red paprika peppers are among the most valuable vitamin C sources [1,2]. 

These four PET scans show how blood flow to different parts of the brain is affected by various activities. In this case, an oxygen isotope that is taken up by the hemoglobin in blood is used as a source of positrons. 

Microtubules (MT) are the largest of the cytoskeletal filaments with an outer diameter of about 25 nm, a wall thickness of about 5 nm, and a central lumen measuring about 15 nm. They consist of tubulin and associated proteins. Vertebrate brain tissue is a rich source of extractable tubulin because of the large numbers of microtubules that are present in axons and dendrites. Tubulin obtained from such a natural source is a heterodimer of 100 kD composed of a-tubulin and P-tubulin. Brain a-tubulin is a globular polypeptide that contains 451 amino acid residues, whereas P-tubulin, which is somewhat shorter, is made up of 445 amino acid residues. These two molecular species of tubulin share in common 40% of their amino acid residues. 

Vertebrate liver is a very rich source of enzymes that metabolize lipophilic xenobiotics, and subcellular fractions are prepared to study metabolism. Sometimes, other tissues such as brain, kidney, testis, and ovary are also treated in this way. A typical subcellular fractionation of liver might be as follows ... 

This system is present in many tissues, including hver, kidney, brain, lung, mammary gland, and adipose tissue. Its cofactor requirements include NADPfl, ATP, Mn, biotin, and HC03 (as a source of CO2). Acetyl-CoA is the immediate substrate, and free palmitate is the end product. 

The radioactive source need not aiways be introduced into the body. Inoperable brain tumors can be treated with y rays from an extemai source, usuaiiy a sampie of cobait-60. The patient is placed in a position where the y-ray beam passes through the tumor. The patient is moved so that the y rays irradiate the tumor from several angles. In this manner the tumor receives a much higher dose of radiation than the dose received by any surrounding tissues. 

Chemokines serve as the messengers in a reciprocal relationship that exists between brain tumors and their environment (Fig. 11.1). Brain tumors are dependent upon stromal sources of chemokines for their growth and spread. They also use chemokines... 

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