Etude par immunofluorescence de l'apparition d'antigènes neuro-spécifiques d'adulte chez l'embryon de Poulet

Immunofluorescent study of the distribution of adult neuro-specific antigens in the chick embryo The adult neuro-specific antigens have been localized by immunofluorescence techniques in diencephalon and mesencephalon of chick embryo. This study has been made using fresh or fixed tissues from embryos 72, 48 or 36 h old. At 72 h of incubation the wall of diencephalon shows marked fluorescence; at 48 h of incubation the fluorescent cells are localized in an outer layer and an inner one. In the 48 h-old embryo the reaction is more distinct and intensive in fresh tissues than in fixed tissues. At 36 h of incubation no fluorescence has been detected either in fresh tissues or in fixed tissues.

Fluorometric Determination of Zinc in Biologic Fluids

The 8-quinolinol complexes of zinc at pH 8.0 (in universal buffer) are stabilized by gum arabic and demonstrate a marked fluorescence at 517 mµ when excited at 375 mµ. Under these conditions only zinc—not magnesium or calcium at physiologic concentrations—can be determined in plasma and urine. Adult plasma has 94 ± 7 µg. zinc per 100 ml. while the plasma of children contains 108 ± 15g./100 ml.

FLUORESCENCE OF AZOTOBACTER: I. A COMPARISON OF THE FLUORESCENT PIGMENTS WITH RIBOFLAVIN

The fluorescent pigments elaborated in cultures of certain species of Azotobacter were compared with riboflavin produced by the same cultures. No correlation between the amounts of fluorescence and riboflavin was observed. Iron appears to inhibit the synthesis of the fluorescent pigments but stimulates riboflavin production. The fluorescent pigments obtained from Azotobacter were water-soluble, thermostable, insoluble in water-free organic solvents, and each exhibited a single absorption peak in the region of 370–380 mμ in slightly acid solution shifting to 400–420 in alkaline solution. Partial purification has been achieved by continuous paper electrophoresis with an acid electrolyte. These studies appear to indicate that the marked fluorescence observed in certain Azotobacter cultures cannot be attributed to riboflavin.

THE EPIDEMIOLOGY OF FOWL CHOLERA

1. A bacteriological study has been made of 210 fresh strains of Pasteurella obtained from typical cases of fowl cholera on seven widely separated poultry farms. 2. The strains have proved identical in consisting of small, pleomorphic, bipolar staining, Gram-negative, non-motile bacilli. They grew rapidly in infusion broth plus a trace of hemolgobin. They formed acid but no gas in media containing dextrose, saccharose, and mannite; indol was produced. 3. The strains fall into three distinct groups, according to their colony formation on hemoglobin agar. The "fluorescent" colony was large, whitish, opaque, exhibiting, under suitable conditions marked fluorescence. The "blue" colony was smaller, clear slate-blue, and non-fluorescent. The "intermediate" colony was moderately fluorescent at 15–18 hours growth, and "blue" thereafter. It was "blue" at all times when crowded and occasionally of "ring" form. "Fluorescent" colony cultures developed "blue" colony forms under certain conditions; otherwise all forms were stable. 4. Strains from "fluorescent" colonies were resistant to precipitation by acids, to sedimentation by centrifuging, and although they combined with specific antiserum, did not agglutinate. They were relatively highly virulent and occurred in flocks where fowl cholera was epidemic. 5. Strains from "blue" colonies were precipitated by acids over a wide range of concentration and agglutinated strongly in antisera. They were relatively of low virulence and occurred in flocks where fowl cholera was endemic. 6. Strains from "intermediate" colonies varied in behavior betweee the "fluorescent" and "blue" strains. They came from a flock where fowl cholera was epidemic.

STUDIES ON BIOLUMINESCENCE

1. Small dumps of the luminous cells of Mnemiopsis cannot readily be stimulated mechanically but will luminesce on treatment with saponin solution. Larger groups of luminous cells (such as are connected with two paddle plates) luminesce on mechanical stimulation. This suggests that mechanical stimulation to luminesce occurs chiefly through a nerve mechanism which has been broken up in the small dumps of luminous tissue. 2. The smallest bits of luminous tissue, even cells freed from the animal by agitation, that will pass through filter paper, lose their power to luminesce in daylight and regain it (at least partially) in the dark. 3. Luminescence of the whole animal and of individual cells is suppressed by near ultra-violet light (without visible light). 4. Inhibition in ultra-violet light is not due to stimulation (by the ultra-violet light) of the animal to luminesce, thereby using up the store of photogenic material. 5. Animals stimulated mechanically several times and placed in ultra-violet light show a luminescence along the meridians in the same positions as the luminescence that appears on stimulation. This luminescence in the ultra-violet or "tonic luminescence," is not obtained with light adapted ctenophores and is interpreted to be a fluorescence of the product of oxidation of the photogenic material. 6. Marked fluorescence of the luminous organ of the glowworm (Photuris) and of the luminous slime of Chatopterus may be observed in ultra-violet but no marked fluorescence of the luminous substances of Cypridina is apparent. 7. Evidence is accumulating to show a close relation between fluorescent and chemiluminescent substances in animals, similar to that described for unsaturated silicon compounds and the Grignard reagents.