Bronchusassociated lymphoid tissue balt

Subset of mucosal-associated lymphoid tissue found as lym-phoid nodules in the lamina propria of the bronchus. Some mammalian species have it constitutively present (e.g. rabbits) but in others (e.g. humans) it can develop in response to infection.

brown adipose tissue Highly vascularized adipose tissue found in restricted locations in the body (in the inter-scapular region in the rat, for example). In hibernating animals and neonates, brown adipose tissue is important for regulating body temperature via non-shivering thermogen-esis.

brown fat cells Brown fat is specialized for heat production and the adipocytes have many mitochondria in which an inner-membrane protein can act as an uncoupler of oxidative phosphorylation allowing rapid thermogene-sis. See brown adipose tissue.

Brownian motion Random motion of small objects as a result of intermolecular collisions. First described by the nineteenth-century microscopist, Brown.

Brownian ratchet Mechanism proposed to explain protein translocation across membranes and force generation by polymerising actin filaments. Relies upon asymmetry of cis and trans sides of the membrane or biased thermal motion as a result of polymerization. Still a hypothesis.

Brucella Genus of Gram-negative aerobic bacteria which occur as intracellular parasites or pathogens in man and other animals. Brucella abortus is responsible for spontaneous abortion in cattle and causes undulent fever (brucellosis), a persistent recurrent acute fever, in man.

Brunner's gland Duodenal gland Small, branched, coiled tubular glands in the submucosa of the first part of the duodenum. Their secretion of alkaline mucus helps neutralize gastric acid from the stomach.

brush border The densely packed microvilli on the apical surface of, for example, intestinal epithelial cells.

Bruton's disease Sex-linked recessive agammaglobulinemia caused by a deficiency in B-lymphocyte function. See btk.

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