Chromosomal analysis of recurrent laryngeal papillomas

Recurrent laryngeal papillomas are tumors believed to be induced by human papillomaviruses. Severity of this disease varies due to the unpredictability of clinical remissions and recurrences. However, the severity of the disease does not affect the classification of these tumors as benign, and the rate of spontaneous conversion of recurrent laryngeal papillomas to carcinomas is very low. Laryngeal papillomas from six patients were evaluated cytogenetically after short-term culture. All six specimens were chromosomally normal, consistent with their classification as benign tumors with a low rate of malignant conversion. The presence of human papillomaviruses has no detectable effect on the chromosomes of these tumors.

The three-dimensional structure of trichosanthin molecule

A model completed recently of two trichosanthin molecules in an asymmetric unit belonging to the monoclinic system is reported. It can be seen that the molecular structure consists of two domains, one large and one small, and that there are some features in the secondary structure. The dissimilarity between two molecules as well as their interactions in an independent unit correlated in a non-symmetric way has been described, moreover, the binding sites of the heavyatom position in the derivatives are also discussed.

Surfactants: a survey of short-term genotoxicity testing

The available results for tests on over 200 surfactants in nine short-term genotoxicity assay systems were reviewed. These tests included the Salmonella/microsome mutation assay, bacterial DNA repair tests, mitotic recombination in Saccharomyces cerevisiae, the mouse lymphoma cell-mutation assay, unscheduled DNA synthesis and sister chromatid exchange assays in mammalian cells, mammalian chromosome damage tests in vitro and in vivo, the dominant lethal test in rodents, and mammalian cell-transformation tests. The collected data cover all four major classes of surfactants: anionic, cationic, nonionic and amphoteric. The results of these genotoxicity tests were overwhelmingly negative. Although there were occasional positive results in bacterial or cell-transformation systems, the testing performed to date indicates that surfactants have negligible potential to cause genetic damage. The available data also indicate that none of the assays were incompatible with testing surfactants for genotoxicity.

Pulmonary absorption of amino acids in the rat: evidence of carrier transport

To investigate the absorption of nonmetabolized amino acids from the rat lung, 0.1 ml of Krebs-Ringer phosphate solution containing either 14C-labeled 1-aminocyclopentanecarboxylic acid (cycloleucine) or alpha-aminoisobutyric acid (AIB) was administered to anesthetized animals by way of a catheter introduced through a tight-fitting tracheal cannula. After various times, lungs were removed and assayed for the amount of amino acid that remained. Cycloleucine appeared to be absorbed by a combination of at least two processes: saturable carrier-type transport and a nonsaturable process. The saturable process was inhibited to varying degrees by a number of L- and D-amino acids but not by D-ornithine, betaine, 3-O-methyl-D-glucose, phenol red, disodium cromoglycate, or tetraethylammonium. The nonsaturable process appeared to be too rapid to be accounted for by diffusion alone, thus suggesting interaction with a second carrier system of high capacity. Although AIB was a weak inhibitor of cycloleucine transport, it appeared to be absorbed solely by a nonsaturable process at a rate consistent with diffusion through aqueous membrane channels.

Fine structure of meiotic prophase chromosomes and modified synaptonemal complexes in diploid and triploid Rhoeo spathacea

The synaptonemal complex (SC) in the diploid Rhoeo consists of 2 amorphous lateral elements, each about 46.0 nm thick, and one amorphous central element about 30.0 nm thick. The central region is about 115.0 nm wide. SC in the triploid have essentially the same dimensions as those of the diploid; both lateral (46.0 nm) and central (30.0 nm) elements are amorphous, and the central region is about 117.5 nm wide. The coil, observed in both diploid and triploid, is a modified short segment of SC with several twists at the end of a synapsed bivalent that is attached to the nuclear membrane. Serial sections in a diploid cell reveal that a coil extends inwards about 3.5 micron from the nuclear membrane and makes a complete turn at a distance of every 0.5 micron. There is a correlation between the modified ends of SC and terminal chiasmata in Rhoeo. The coils might have a positive role in the process of crossing over, or alternatively might be involved in ring formation by holding chromosome ends together while chiasmata are not involved. SC are present in chromocentres of both diploid and triploid. Chromocentres in diploid and triploid are indistinguishable, and appear to be formed from the aggregation of pericentromeric heterochromatin as a result of translocations which occured close to the centromeres. 3-dimensional hypothetical pachytene configuration of the diploid is presented.

New method for detecting and quantitating pharmacokinetic drug-drug interactions applied to ethanol-propranolol

A novel method for detecting and quantitating pharmacokinetic drug-drug interactions is described. The method involves perturbation of an existing steady-state whole blood (or plasma) concentration of one drug by the other drug. The method would allow differentiation of "pharmacokinetic" drug interactions from "pharmacologic" interactions. It is shown that a bolus intravenous injection of propranolol reduced a steady-state arterial blood concentration of ethyl alcohol by 26% in the cat.