Comparative small intestine absorption, biliary excretion and aorticportal blood levels of 14C-cephaloglycin and 14C-cephalexin were determined in rats utilizing isolated proximal intestinal loops in vivo and in vitro and biliary cannulation. The absorption of both drugs was linear but significantly higher for cephalexin; 91.2% of cephaloglycin remained in enteric contents whereas 42.9% of cephalexin was found contained in or transferred across the mucosa. High chloroform solubility of cephalexin (277.5) compared to cephaloglycin (0.034) was consistent with the differences in intestinal absorption. Relatively high, 12 hour, biliary excretion of cephaloglycin (496 μg) and cephalexin (304 μg) was observed but only cephalexin resulted in significant aortic (13.1 μg/ml) and portal venous (6.6 μg/ml) concentrations.

The scanning-beam electron microscope (SEM) allows visualization of the surface morphology of populations of intact bacterial cells at high magnification in three-dimensional perspective. This communication reports the use of the SEM in studies which defined the normal morphology of specific microorganisms and the abnormalities induced by cell-wall active antibiotics. As demonstrated by these studies, SEM observations correlate well with previous visual experience with other forms of microscopy. Physicians, therefore, need not be experienced electron microscopists to appreciate phenomena made visible with the SEM. The techniques utilized in the preparation of specimens for examination have been described previously.1 The normal morphology of a strain of penicillin-resistantStaphylococcus aureus isillustrated in Fig 1,A. Figures 1,Bthrough 1,Fdemonstrate the effect of three hours' exposure to increasing concentrations of cephalothin added to this culture during the logarithmic phase of growth. These phenomena represent a progression of changes which