In vitro assessment of the toxicity of metal compounds

A review has been compiled illustrating the directions taken in examining the genotoxic effects of metals and their compounds centering only on those studies pertaining to effects of metals and their compounds on DNA structure and function, such as the induction of DNA strand breaks, production of DNA-protein crosslinks, induction of chromosomal aberrations, and sister chromatid exchanges. Although it is premature to declare a cause and effect relationship between the carcinogenic activity of metals and their ability to induce one or more lesions in DNA, strong evidence is emerging to suggest such a relationship. Low concentrations of metals induce the appearance of DNA lesions, such as strand breaks and crosslinks, or induce sister chromatid exchanges or DNA repair synthesis. Assays based upon these events constitute extremely sensitive probes for genotoxic effects of metals and their compounds. These effects of metals on DNA are consistent with the currently accepted mechanism of chemical carcinogenesis, allowing the acquisition and propagation of altered DNA function. The lack of complete information on the activity of metals in producing DNA lesions allow only preliminary conclusions to be drawn. Certain compounds containing potentially or actually carcinogenic elements, such as Ni, Be, As, Cr, Cd, and to a minor extent Pb, have yielded positive responses in one or more DNA lesion assays. At relatively nontoxic levels of Ni and Cr, considerable evidence suggests that multiple types of DNA lesions are induced.     

The effect of antennectomy on the humidity reactions of Carpophilus dimidiatus and C. hemipterus (Coleoptera, Nitidulidae)

The humidity reactions of intact and antennaless specimens of Carpophilus dimidiatus and C. hemipterus were studied. The results suggested that the hygroreceptors mediating a response to high humidities are situated on the antennae in both species and those mediating a response to low humidities, in the case of C. dimidiatus, elsewhere on the body.

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Résumé On a étudié la réaction à l'humidité de Carpophilus hemipterus et C. dimidiatus intacts et sans antennes. Les résultats suggèrent que les hygrorécepteurs qui répondent aux humidités élevées se trouvent sur l'antenne dans les deux espèces et ceux qui répondent aux basses humidités sur l'antenne de C. hemipterus et dans une autre partie du corps de C. dimidiatus.

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On transfer from tropical Stored Products Centre, O.D.M., Slough, Bucks     

Protein Synthesis in Sonically Damaged Escherichia coli

By gentle sonic treatment, Escherichia coli cells were modified to permit penetration of actinomycin D, adenosine triphosphate, trypsin, ribonuclease, and polyuridylic acid. The behavior of these "soniplasts" as protein-synthesizing particles was investigated.     

Histochemistry of implantation in the rabbit

Summary The distribution of glycogen, acid and neutral mucopolysaccharides, hydrolases alkaline phosphatases, and carbohydrate dehydrogenases is described in the rabbit blastocyst and its surroundings over the implantation period from 5 to 9 days.Glycogen is found mainly in the embryonic tissues, where peaks of concentration coincide with differentiation, some is also seen in the uterine epithelium and secretion, and large quantities accumulate in the developing decidua.Neutral mucopolysaccharide is found in the yolk-sac and embryonic endoderm, and as secretion droplets in the uterine epithelium and secretion.Acid mucopolysaccharide occurs in the embryonic coverings and uterine secretion.RNA is associated in the embryo with developing tissues, and accumulates in the developing decidual cells.Hydrolases (acid phosphatase, and B esterase) increase their activity in the trophoblast knobs, in developing syncytiotrophoblast, and in the embryonic endoderm. Degeneration of the uterine epithelium is associated with maximal hydrolase activity.Trophoblastic alkaline phosphatase activity (non-specific and specific) decreases from 5 to 7 days of gestation, then increases markedly in the developing syncytiotrophoblast. AMPase appears in the embryonic mesoderm. In the uterine epithelium intense brush border staining is seen, and TPPase and UDPase become visible for a short period in the Golgi region. Phosphatases increase their activity in the decidua to 8 days and then decrease.Carbohydrate dehydrogenases (except -glycero-phosphate and -hydroxy-butyrate dehydrogenases) increase their activity in embryonic tissues, particularly in the developing syncytiotrophoblast and endoderm. Symplasma formation in the uterine epithelium is also associated with increase in enzyme activity, and a similar increase, up to 8 days of gestation, is seen in the decidua with isocitrate, malate, glucose-6-phosphate, lactate, succinate, and furfuryl alcohol dehydrogenases.Some correlation is found between the histochemical findings and the phenomena of epithelial removal, uterine secretion, decidual formation and function, giant cell function, morphogenesis, and histiotrophic nutrition, and the results are compared with previous findings for the rat in which implantation is morphologically, and probably physiologically a very different process.     

Comparative histochemical distribution of “leucine amino-peptidase” in the placenta and foetal membranes

Summary The distribution of an enzyme, or enzymes hydrolysing l-leucyl--naphthylamide is studied in the placentae, foetal membranes, and uterine structures of the horse, sheep, cat, dog, ferret, rat, rabbit, guinea-pig, and human. Activity is seen mainly in the trophoblast (except that of the cat, dog, and guinea-pig), in the rodent yolk-sac endoderm (except that of the rat), or in the uterine epithelium — surface (sheep and guinea-pig) or glandular (dog). The presence of the enzyme or enzymes is correlated with possible functions in absorption and transport of materials, or in elaboration and release of complex molecules.