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Several studies dealing with the reactions of dental nerve fibers to injury and inflammation are reviewed in this article. The subgroup of dental nerve fibers that contains calcitonin gene-related peptide (CGRP) was examined by immunocytochemistry at various times (1 to 35 days) after one of three degrees of injury: (a) Mild: Four days after making shallow cavities into cervical dentin of first molars of anesthetized adult rats, we found that CGRP fibers had sprouted into the subjacent odontoblast layer and dentin, and then returned to normal by 3 wk. (b) Intermediate: If the cervical cavities were acid etched, we found damage to the odontoblast layer, microabscess formation, and sprouting of CGRP fibers near the abscess, with subsequent formation of reparative dentin and healing. (c) Severe: If the pulp was exposed, a variety of reactions could occur, the most prevalent of which was a severe necrosis leading to development of periapical lesions. Analysis of the progressive stages of pulpal abscess and necrosis showed sprouting CGRP nerve fibers (a) at the retreating interface between abscess and vital pulp; (b) in periapical areas during onset of lesions; and (c) around chronic abscesses in granulomatous periodontal tissues. These studies are discussed in relation to various dental clinical problems such as hypersensitive teeth, episodic toothache, early onset of periapical lesions, dental anesthesia, and possible roles for sensory fibers and neuropeptides in tissue defense and healing.

1. This paper reports the isolation and the partial purification of cAMP phosphodiesterase (EC 3.1.4.17) from the promastigote form of Leishmania tropica and a preliminary result from Leishmania donovani. 2. The activity of the fraction obtained from column chromatography was measured. 3. The effects of pH, temperature, time of incubation and various compounds on its activity in vitro were obtained. 4. Two peaks (I and II) exhibiting cyclic nucleotide phosphodiesterase activity were obtained. 5. Both activities were found to require the addition of Mg2+ ions for full effect. 6. The apparent Km values for the first and second peaks were 1.43 x 10(-3) M and 4.1 x 10(-3) M respectively. L. donovani shows only one peak of activity.