Freeze-dehydration for permanent mounts after aceto-orcein stain.
Fresh smears of mammalian material were stained 5 min (only) by La Cour's (1941) aceto-orcein method at 60°C, briefly rinsed and drained, and then dehydrated in a prechilled equal-parts mixture of absolute alcohol and anhydrous acetone held 2 hr or more at — 20°C or lower by means of dry ice. The preparations were differentiated 30 sec at room temperature in 95% alcohol containing 1% HCl, counterstained (optional) in a 0.01% solution of fast green FCF in absolute alcohol for 10 sec, passed through 2 changes of xylene and mounted in HSR or other synthetic resin.
Studies on the structure of the chromosomes
SummaryThe structure of the mitotic chromosomes ofAllium cepa has been elucidated by controlling the temperature and time of exposure of fresh roots to stain fixatives. The details seen in material stained in N HCl-orcein for 8 min. at 60° C. and squashed after varying intervals of storage at room temperature were essentially similar to pictures obtained with 1% aceto-orcein and 1% aceto-orcein-N HCl (10:1) under identical conditions of handling. The chromosomes appear quadri-partite at metaphase and bi-partite at anaphase. A rare instance of the precocious assumption of a quadri-partite condition by two anaphase chromosomes is illustrated. Caduceus coiling of chromonemata was seen in chromosome bridges also. Chromosomes have material easily dissociable from the chromonemata and their removal does not affect the structural integrity of the chromosome.
A Series of New Sulfonamides Which Are Unaffected by p-Aminobenzoic Acid
Probably the greatest contribution to the field of chemotherapy was Domagk's introduction of prontosil (chrysoidin) in 1935. Trefouel et al. (1935) soon theorized that in the tissues prontosil was broken down at the azo linkage to triaminobenzene and p-aminobenzenesulfonamide, and that this latter group was the active part of the prontosil molecule. The introduction of prontosil and its active principle, sulfanilamide, opened the way for successful treatment of streptococcal, gonococcal, and meningococcal infections. Inasmuch as pneumococcus infections did not respond to sulfanilamide therapy, it remained for Whitby (1938) to introduce sulfapyridine, a sulfonamide effective in the treatment of pneumococcus infections as well as those previously mentioned. With this impetus given to sulfonamide research, several new and important compounds were soon introduced: sulfathiazole by Fosbinder and Walter (1939), sulfadiazine by Roblin et at. (1940), and sulfaguanidine by Marshall e al. (1940). Up to this period none of the sulfonamide compounds were found to have any appreciable effect against certain other groups of organisms, notably the anaerobic clostridia commonly associated with war-wound infections. Miller et al. (1940) synthesized p-aminomethylbenzenesulfonamide (sulfamylon1) which was subsequently found by Klarer (1941) to be highly effective against certain anaerobic bacteria. Moreover, Schreus (1942) found that paminomethylbenzenesulfonamide was unaffected by p-aminobenzoic acid, an attribute not associated with the common sulfonamides described heretofore. These observations led one of us (Lawrence, 1944, 1945) to conduct an extensive study on the in vitro activities of p-aminoalkylbenzenesulfonamides against a variety of microorganisms. It also stimulated an interest in the search for other possible sulfonamides which are unaffected by p-aminobenzoic acid. Compounds of this type were found when a group of sulfanilylanilides was investigated. The main representative of this group is sulfanilyl-3,5-dibromoanilide. A discussion of p-aminobenzoic acid relationships to the latter will be presented in another section of this report. To our knowledge, there is no reference in the literature to the antibacterial effects of di-halogen-substituted sulfanilylanilides. Suter and Weston (1940), however, described the preparation of a mono-halogenated sulfanilylanilide, sulfanilyl-4-fluoroanilide, and noted that it showed a slight effect against streptococcal infections in mice. Marchant et al. (1942) described a series of 38 N'-substituted sulfanilamides, among which was sulfanilyl-4-bromoanilide.