Tissue, slices connective

The use of tissue slices for experiments on histidine decarboxylation introduces the additional problem of the access of substrate, co-enzyme and inhibitors into the cells. In this connection, it should be noted that in practice the specificity of an enzyme within a cell may be increased by the specificity of the substrate-transporting system. Similar considerations apply to the in vivo inhibition of histidine decarboxylases there is, however, the additional possibility of modifying production of the apo-enzyme either by restricting the supply of amino acids or by altering the hormonal state of the animal. 

Immediately after the rats had been killed, tissue slices taken firom three lobes of the liver were histochemically stained for GGT by the mediod described previously (4). GGT positive foci were analyzed with hnagelyzer model HTB-C995 (Hammatsu Television Co., Ltd., Shizuoka, Japan) connected to Desktop Computer System-45 (Hewlett-Packard, Co., USA). 

A variety of different types of tissue preparation are used to study neurosecretion and synaptic transmission. A classical preparation is the frog NMJ (discussed below). The brain slice has been used for many years for biochemical studies of CNS metabolism and is a useful preparation for electrophysiological studies of synaptic transmission in the CNS. Slices can be oriented to maintain the local neuronal circuitry and can be thin, 0.3 mm, to minimize anoxia. The transverse hippocampal slice is widely used as an electrophysiological preparation to study synaptic plasticity (see Ch. 53). Primary cultures of neurons from selected CNS areas and sympathetic ganglia are also frequently used. They permit excellent visual identification of individual neurons and control of the extracellular milieu, but the normal neuronal connections are disrupted. 

In rheumatic disease, the main pathological manifestations appear in connective tissue, the chief constituents of which are collagen, elastin and mucopolysaccharides. The last, apart from hyaluronic acid and chondroitin of cornea, are all sulphate esters , the sulphate groups of which are in a dynamic state with a short biological half-life. The sulphate exchange is under enzymic control and can be decreased in vitro and in vivo by corticosteroids " . Bostrom and Mansson examined the effects of a number of salicylates on the incorporation of S into calf costal cartilage slices in vitro. 

Tissue compression and tearing during slicing may occur if removal of connective tissue and blood vessels is incomplete (such tissue will not be cleanly cut by the blade). Compression and tearing will compromise slice viability. 

The seeding of the apatite crystals triggers the entire mineralization process. All tissues are irrigated with a plasma supersaturated by calcium and phosphate. Yet crystallization occurs only in five different structures. Does the cartilage or the connective tissue of the bone contain specific molecules that precipitate calcium phosphate, or does the osteoblast secrete an enzyme that triggers crystallization In 1923, Robinson incubated slices of rachitic rat tibial epiphysis. 

Currents from cells in an integral tissue can be recorded by making patches on cells from thin slices obtained by cutting the tissue with a vibrating microtome. Cells that maintain their connections with other cells can be visually identified using a non-inverted microscope. This technique is particularly appropriate for recording post-synaptic currents, evoked by stimulation of neighboring cells [40]. 

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