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Studies carried out on a number of secretory cell systems suggest that the specific cytoplasmic granules in which the secretion products are stored before their release are complex organelles which can possess a distinct molecular organization. For instance, it has been reported that in some granules the segregated secretion products are organized into crystalline structures (1-3) or large intermolecular aggregates (4-8). It is likely that all phenomena of this type are favorable to the economy of the cell, in the sense that they reduce the energy required for storage of the secretion products. The prolactin (LTH) granules of the rat pituitary possess a number of morphological features which strongly suggest that the molecules(s) of their content might be arranged in a relatively stable structure. Thus, these granules are remarkably polymorphic in shape, and their membrane is usually separated from their content by a clear space. Furthermore, identifiable LTH granules devoid of their membrane are often seen in the pericapillary space, suggesting that upon discharge by exocytosis they are dissolved only slowly (9). However, no studies specifically concerned with the mechanisms of LTH storage have been reported so far. In order to obtain some information on this question, we have studied the behavior of isolated granule fractions incubated in vitro under a variety of carefully controlled experimental conditions.

THEtoxication in order to stimulate interest in this disease so that cases may be found and treatment instituted early, before irreversible sequelae occur.Lead poisoning in children is relatively common. The rarity of the diagnosis at any particular institution may mean merely that one is inclined to forget that such an entity exists. In recent years fairly large series of cases have been reported from various hospitals throughout the country. Ennis1 reported 47 cases from Baltimore in 1950. Eighty-nine cases of lead poisoning were observed in infants' and children's hospitals in Boston during the years 1924 through 1933 (McKhann and Vogt).2 Rapoport3 reported 30 cases from the Children's Hospital, Philadelphia, in 1941.Twelve of the 14 patients were admitted between June, 1951, and September, 1951, with 1 admitted in February, 1951, and 1 in December, 1951. Of 12 cases of lead encephalopathy, 10 occurred between the months

Isolation of Cytokinins from « Rhizobium leguminosarum » Frank. — Three substances with cytokinin activity have been isolated from liquid cultures of Rh. leguminosarum by fractionation on Dowex 50W X4 H+ column, butanol extraction, silver precipitation, chloroform extraction and finally by paper chromatography. The Rf-values and the U.V. absorption maxima of one of these substances were similar to those of isopentenyl adenine, a potent cytokinin synthetized by several bacteria responsible, as Rhizobium, for profound morphological alterations of the tissues of higher plants. The other two substances are not comparable to any of the as yet known natural cytokinins. It is suggested that these substances, produced by Rhizobium, are responsible for tissue proliferation during nodule formation.

Polyacrylamide disc gel electrophoresis has been recently introduced for the assay of rat anterior pituitary gland hormones, particularly of prolactin and of growth hormone (GH). The most important step in this method, on which its reliability and quantitative yield depend, is the extraction of hormones from the pituitary gland. This paper reports a comparison between different methods of extraction already described in the literature, and our own procedure, which seems to give a quantitative extraction of the GH and the prolactin present in the pituitaries.For the extraction of the hormones, female rat anterior pituitaries were homogenized (3%, w/v) in 0·02 m-phosphate buffer, pH 7·0, according to Kurcz, Nagy & Baranyai (1969); in water, according to Yanai & Nagasawa (1969); in acrylamide sample gel, pH 8·6, according to Nicoll, Parsons, Fiorindo & Nichols (1969); or in 0·32 m-sucrose. This last homogenate was diluted 1:1 with 0·02 m-phosphate