Erythromycin (EM), discovered in 1953,1 was the first clinically useful macrolide antibiotic. It is still widely used today as an effective agent against infections with Grampositive bacteria, Gram-negative cocci, and mycoplasmas.
Chemical modifications of 8,9-anhydroerythromycin A 6,9-hemiacetal (1), which showed gastrointestinal motor stimulating (GMS) activity 10 times more potent than that of erythromycin A (EM-A), were undertaken to search for derivatives having stronger GMS activity and no antimicrobial activity; details are described in this and a subsequent paper. Displacement of a methyl group of the dimethylamino group of 1 with an ethyl group and an isopropyl group provided de(N-methyl-N-ethyl-8,9-anhydroerythromycin A 6,9-hemiacetal (55) and de(N-methyl)-N-isopropyl-8,9-anhydroerythromycin A 6,9-hemiacetal (58), respectively. They showed significant GMS activity and no antibacterial activity. In particular, the GMS activity of 58 was increased to 248 times that of EM-A. EM-A and the derivatives obtained in this study mimic exogenous motilin in the dog. The name "motilide", meaning a motilin-like macrolide, is proposed for this new family of macrolide compounds.
Light microscopy, scanning electron microscopy and transmission electron microscopy have been used to delineate the structure and function of the lamina propria mucosae in the rat jejunum. In silver-impregnated sections, the adepithelial surface of the lamina propria mucosae was framed by a sheet of reticular fibers (reticular sheet). Short-term (3-hour) immersion of jejunal tissues in 2 N NaOH solution enabled us to simultaneously view networks of reticular fibrils and fibroblasts residing in the subepithelial connective tissue under a scanning electron microscope. The reticular fibrils, which measured about 40 nm in diameter and were interwoven in dense networks, formed a sheet 2–3 µm thick. In the villi, this sheet contained numerous foramina ranging from 3 to 7 µm in diameter, through which lymphocytes, macrophages, basal extensions of epithelial cells and fat particles traversed. The reticular sheet in the domes of isolated lymphoid nodules was markedly porous, and many lymphocytes migrated into or out of the epithelium through the foramina. The foramina of the reticular sheet may participate in the communication between the intestinal epithelium and the lamina propria mucosae. It was noted that the foramina of the reticular sheet in the villi were surrounded by end feet of the cytoplasmic processes of fibroblasts. In addition, these fibroblasts were combined with lymphocytes or dendritic cells in the lamina propria mucosae.
A series of quaternary ammonium derivatives of 8,9-anhydroerythromycin A 6,9-hemiacetal (1) and 9,9-dihydroerythromycin A 6,9-epoxide (2) has been prepared and tested for antimicrobial activity and gastrointestinal motor stimulating (GMS) activity in the dog (in vivo). The GMS activity is enhanced markedly when small alkyl halides and unsaturated alkyl halides such as allyl bromide and propargyl bromide are added to the dimethylamino group of 1. Among them, N-propargyl-8,9-anhydroerythromycin A 6,9-hemiacetal bromide (3) exhibits GMS activity 2890 times stronger than that of erythromycin A and is completely devoid of antimicrobial activity. The potency of 3 is comparable to that of synthetic motilin both in vitro and in vivo.
This pilot study found that epidural tramadol administered before incision induced a Cmax within 30 minutes of administration. The drug was detected in serum at ∼21 hours after surgery.
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