Airway reactivity in cotton bract-induced bronchospasm

Most healthy subjects challenged with cotton bract extract demonstrate some degree of bronchospasm. This response has been associated with the endogenous production of histamine by the inhalation of cotton bract extract. We examined whether this responsiveness reflects increased sensitivity to histamine. Thirty-one healthy subjects were screened for sensitivity to cotton bract extract administered by nebulization. Pulmonary function was measured using partial expiratory flow-volume curves on which flows at 60% of the control vital capacity below total lung capacity were measured (MEF40%(P)). Responders were defined as subjects who exhibited a 20% or greater decrease in MEF40%(P) after 10 min inhaling cotton bract extract. Of those screened, 10 subjects were responders. From the remaining nonresponders, 11 consecutive subjects were selected. The maximal decrease in MEF40%(P) in responders was 40.5 +/- 5.1%, compared to 10.9 +/- 2.2% in nonresponders. The dose-response relationship for histamine was measured in all subjects, using inhalations of progressively more concentrated histamine solutions. The mean +/- SEM threshold for the responders was 38.4 +/- 7.4 mg of histamine per ml, compared to 42.2 +/- 6.8 mg of histamine per ml for responders (difference not significant). The percentage decrease in MEF40%(P) at the threshold dose was 27.6 +/- 3.7% for responders and 32.4 +/- 5.2% for nonresponders (difference not significant). We conclude that healthy subjects sensitive to cotton bract extract do not exhibit increased reactivity to histamine. This suggests that responders are not, in general, subclinical asthmatics, and that the difference between responders and nonresponders to CBE is not due to increased histamine sensitivity among responders.

Regulation of aromatic amino acid transport by tRNA: role of 2-methylthio-N6-(delta2-isopentenyl)-adenosine

E. coli growing rapidly in media where ferric iron is not freely available contain a population of specifically undermodified tRNAs. These tRNAs contain isopentenyl adenosine instead of the usual methylthioisopentenyl adenosine adjacent to the 3' end of the anticodon. Iron restricted E. coli also show an enhanced capacity to transport aromatic amino acids into the cell. Our work shows that undermodified tRNAs for phe, tyr and trp can function as positive regulatory elements of the aromatic amino acid transport system in E. coli. This iron related metabolic control, mediated through a specific post-transcriptional modification of the tRNAs, may be an important mechanism for adapting E. coli for growth in an iron restricted environment.

Activity of 10-chloro-5-(2-dimethylaminoethyl)-7H-indolo [2,3-c]-quinolin-6(5H)-one hydrochloride against experimental tumors in mice and rats

10-Chloro-5-(2-dimethylaminoethyl)-7H-indolo [2,3-c]-quinolin-6(5H)-one hydrochloride (CIQ) was shown to exert significant antitumor activity against the Ehrlich carcinoma and sarcoma 180 transplantable tumors in mice by the intraperitoneal (ip) or oral (po) routes and when incorporated into diet. A solid tumor induced in BALB/c mice by the subcutaneous (sc) implantation of nonproducer murine sarcoma virus-transformed BALB/3T3 cells was also inhibited by CIQ after ip or po treatment but there was no effect against leukemia L1210 ascites or a transplantable murine renal adenocarcinoma. When tested in rats, CIQ significantly reduced the growth of Flexner-Jobling carcinoma, Murphy-Sturm lymphosarcoma and Walker 256 carcinosarcoma when administered by the ip or po routes. Pretreatment, but not posttreatment, with CIQ slightly inhibited the humoral antibody response of mice to sheep red blood cells. CIQ therefore differs from immunosuppressive agents such as imuran, methotrexate, cytosine arabinoside, or 6-mercaptopurine which affect the antibody response of mice to sheep erythrocytes when administered after immunization.

Dihydroretinoic acids and their derivatives. Synthesis and biological activity

The syntheses of the ring and four side-chain dihydroretinoic acids and/or their esters, 3-7, are described. The syntheses of several other retinoids containing a substituted aromatic ring are also included. The biological activity of the compounds was evaluated in vivo in a chemically induced mouse skin papilloma test and in vitro in two vitamin A deficient assays. The activity observed for 1a, 1c, and 2a in the former test was partially retained in the dihydro derivatives 4b, 4c, and 6b. Similar results were found in the in vitro assays.

The Role of Antibodies in Experimental Drug Resistance of Trypanosoma Equiperdum

Different methods of inducing drug-resistance of T. equiperdum towards p-rosaniline HCl were compared. The “classical” technic of rendering trypanosomes resistant by treatment of relapses with slowly increasing doses of the dyestuff was inferior to methods which avoid the formation of antibodies (short passage; splenectomy). Drug-resistance was more difficult to achieve in rats than in mice, due to more abundant antibody-formation in rats. Splenectomy and short passage combined gave satisfactory results. The rapid development of p-rosaniline-fastness in splenectomized mice was counteracted by passive immunization with trypanocidal rabbit serum.