A scanning electron microscopic study of the two-step effect of cytochalasin B on Ehrlich ascites tumor cells

The effect of cytochalasin B (CB) on the surface structure of Ehrlich ascites tumor cells was investigated using the scanning electron microscope. The effect occurs in two steps: formation of zeiotic knobs on the cell surface and subsequent grouping of the knobs at one pole of the cell. The early step of zeiotic knob formation occurs at low concentrations of CB (0.5-1 microgram/ml) at 37 degrees C and at high concentrations of the drug (5-10 microgram/ml) at low temperature but within 1 min at 37 degrees C. This step is only partially inhibited by 5 x 10(-3) M sodium azide. The subsequent grouping of zeiotic knobs lasts for more than 2 min at 37 degrees C and occurs only in the case of high concentrations of CB. It is inhibited by sodium azide and is often associated with grouping of the microvilli, which are then lost from all of the cell surface except the area of knob-grouping.

Bacterial flora of ex-germfree mice after oral inoculation of feces from various species of conventional animals

Emulsions of fresh feces from a conventional mouse, rabbit, dog or cynomolgus monkey were administered orally to germfree and conventional ICR mice. Various fecal floras bearing a striking resemblance in pattern to those in the inoculant became established in the inoculated ex-germfree mice. Reinoculation of these ex-germfree mice with fecal emulsions from a conventional mouse made 21 days after the original inoculation (conventionalization) led to alteration of their floras to the indigenous pattern of conventional mice. The administration of feces from the conventional animals of different species did not appreciably modify the fecal flora of conventional mice. The results indicate that intestinal flora of animals is determined in the first stage by that of the contaminants, but this would be altered later under the predominant influence of the various host factors.

The dynamics of clindamycin-2-phosphate in vivo and its transfer to tissues

Studies were conducted on clindamycin-2-phosphate, a preparation of clindamycin CLDM developed for injection, and the following results were obtained. 1) The concentration of CLDM phosphate and lincomycin (LCM) in sera were measured in rabbits following continuous intravenous infusion of 20 mg/kg over a 60 minute period, and the results were compared in a crossover test. 2) The concentration of CLDM phosphate in the oral tissues of rabbits following continuous intravenous drip infusion of 20 mg/kg over a 60 minute period was found to be a maximum in the submaxillary gland (21.1 microgram/g), followed by the liver, submaxillary lymph nodes, sera and tongue. The concentration of LCM was found to be the highest in the submaxillary gland (20.2 microgram/g), followed by the submaxillary lymph nodes, tongue, sera and liver. 3) The metabolism of CLDM phosphate in vivo was investigated using TCL. CLDM phosphate was found to metabolize to CLDM N-demethyl CLDM in vivo. 4) The peak concentration of CLDM phosphate in human sera following intravenous drip infusion of 600 mg over a 60 minute period averaged 11.9 microgram/ml, while the average concentration of LCM in sera under identical circumstances was approximately twice that of CLDM phosphate.

Influence of medium and diluent pH and diffusion time on antibiotic bioassay

The effects of pH assay medium and diluents and of diffusion time on antibiotic bioassays were investigated to determine optimal assay conditions. Assays of penicillins, cephalosporins and macrolide derivatives were found to be little affected by the pH of the diluent, whereas the pH of the diluent exerted a noticeable influence on aminoglycoside assays, in which, therefore, it is essential to use a diluent at approximately p H 8.0. The data obtained have also demonstrated that the assays of penicillins, cephalosporins, macrolide derivatives and aminoglycosides were influenced by the pH of the assay medium. It is important to carry out penicillin or cephalosporin assays on plates of medium adjusted to approximately pH 6.0 and macrolide derived or aminoglycoside assays on a medium which is adjusted to approximately pH 8.0. The optimal duration of preculturing of assay plates for diffusion at 4 degree C after addition of the sample was determined to be 2 hours for the penicillins and cephalosporins. Diffusion of more than 2 hours was inadequate for assays of these antimicrobial agents. Diffusion times of less than 2 hours. For the macrolide derivatives and aminoglycosides, preculturing of 2 hours for diffusion at 4 degrees C was noted to be optimal, while preculturing for less than 2 hours proved inadequate. Diffusion times exceeding 2 hours had little effect on the assay of these antibiotics.

Epithelial cell kinetics in the crypts of familial polyposis of colon

Epithelial cell kinetics were examined in the uninvolved part of the rectal mucosa in nine cases of familial polyposis of colon, six cases of their first degree relatives, and six control cases. The biopsied specimen were incubated for two hours in the culture medium containing H3-thymidine. In the control cases, the proliferating zone was confined to the lower two thirds of the crypt in all except one case. Six of the nine cases of familial polyposis of colon had crypts with altered proliferating zone, i.e., incorporation of H3-thymidine was observed in the upper one third of the crypt as in the case of adenomatous polyps. Three of the six cases of the first degree relatives showed such change. There were significant differences in the incidence of such change between controls and familial polyposis of colon or their first degree relatives, whereas no significant differences between familial polyposis of colon and their first degree relatives.

Increased oxygen affinity for hemoglobin Sawara: alphaA4(6) aspartic acid replaced by alanine

The oxygen binding property of Hb Sawara (alphaA4 Asp replaced by Ala) was studied at different pH values with and without addition of 2,3-diphosphoglycerate. The oxygen affinity of Hb Sawara was shown to be increased, the difference of the log P50 value between normal and abnormal hemoglobins being 0.37 at pH 7.0. Both the magnitude of the alkaline Bohr effect and the effect of 2,3-diphosphoglycerate upon oxygen affinity of Hb Sawara were comparable to those of Hb A. The amino acid substitution of alanine for alphaA4 aspartic acid might result in the loss of a stabilizing force for ionic interaction between the alpha-amino group of NA (1)alpha1 valine and the alpha-carboxyl of HC3(141)alpha2 arginine in the deoxy-form.

Mechanism of histamine release by alpha-chymotrypsin from isolated rat mast cells

Alpha-chymotrypsin (CT) was modified chemically and physically by the treatments with diisopropyl fluorophosphate, L-(1-tosylamide-2-phenyl) ethylchloromethylketone, hydrogen peroxide and heat. After these treatments, CT lost or decreased both the enzymic activity and ability of releasing histamine from rat mast cells. Ca++ was essential for histamine release by CT, while it enhanced only slightly the enzymic activity. Process of histamine release by CT could be separated into two stages: CT-dependent but not Ca++-dependent, and Ca++-dependent but not CT-dependent. The activated state of mast cells produced by CT decayed rapidly at 37 degrees C in the absence of Ca++, but these cells responded to Ca++ by adding CT once again, suggesting reconstitution of cell membrane structure affected by CT. Isoproterenol, epinephrine, prostaglandin E1, and dibutyryl-cyclic AMP (0.01-0.1 mM) did not inhibit release of histamine induced by CT. Neither theophylline (0.01-0.1 mM) alone nor the combinations of these cyclic AMP-active agents with theophylline inhibited the release of histamine. But, in the presence of papaverine (0.01-0.1 mM) a marked, dose-dependent inhibition was observed. These data suggest that 1) release of histamine by CT from rat mast cells is causally related to its hydrolytic activity, 2) this activity causes a reversible change on mast cell membrane which probably facilitates Ca++-influx through the cell membrane, and 3) there are subtle differences among CT, compound 48/80 and antigens concerning the effect of cyclic AMP-active agents in histamine-releasing mechanisms in mast cells.