Concordant change in mitochondrial and nuclear genes in a hybrid zone between two frog species (genusBombina)

Summary In contrast to results in other studies, nuclear and mitochondrial genes were found to change concordantly in a transect across the hybrid zone betweenBombina bombina andBombina variegata. mtDNAs of both species are found in populations in the central part of the zone, whereas populations at its margins contain mtDNA corresponding to nuclear genomes.     

Antifungal properties of taxol and various analogues

The antimitotic agent taxol was tested for toxicity towards fungi from different taxonomic groups and found to be particularly active against oomycete fungi. In germinating zoospore cysts of the oomycetePhytophthora capsici the mechanism of action of taxol was shown to involve inhibition of mitosis, presumably resulting from an effect on microtubules. Various taxol analogues with deleted A-ring C-13 side chain substituents were tested for toxicity towardsP. capsici andAphanomyces cochlioides to provide insight into structural features required for activity. The importance of the side chain was shown by the much lower activity as compared to taxol of analogues lacking all or part of the side chain. The effect of stereochemistry at the C-2 position on fungitoxicity towards oomycetes was similar to that reported previously on mammalian microtubule assembly.     

Low allozyme and mtDNA variability in the island endemic speciesDrosophila sechelia (D. melanogaster complex)

Summary Genetic variability ofD. sechellia is investigated at both mitochondrial and nuclear levels. The results reveal the existence of a single main type of mtDNA with very few variants and a very low enzyme polymorphism. This situation is consistent with the small population size of this specialized species.     

Association of DNA replication with nuclear membrane in larvae ofChironomus thummi

Summary In the larvae ofChironomus thummi, the newly replicating DNA has been found to be associated with the nuclear membrane, as evidenced by the isolation of DNA nuclear membrane complexes (M-band) of³H-thymidine labelled larvae.Acknowledgment. The authors thank Dr D. S. Pradhan for discussions and encouragement.     

Circadian rhythm in the subcommissural organ of the frog,Rana arvalis Nilsson,under natural conditions

Summary A circadian activity of SCO ependymal cells, judged by changes in the nuclear volume, has been found in juvenile frogs (Rana arvalis) under natural summer conditions. The nuclear volume reaches its maximum at 12.00 h and a minimum at 24.00 h. A significant increase in activity occurs between 06.00 and 09.00 h and a gradual decrease is observed from 12.00 to 24.00 h.     

Die Wirkung von Demecolceinamiden an Zellenin vitro

Summary A series of demecolceinamids was examinedin vitro on chicken fibroblasts, leucocytes, and different bacteria. It was found that with increasing length of the side chain on ring C the antimitotic activity is decreasing while the antibacterial effect is increasing.     

Les transformations des nucléoides deEscherichia coli déclenchées par les rayons X

Summary In order to obtain further knowledge on the action of radiation on living cells we studied the nuclear transformations ofE. coli after exposure to X-rays. Three different phenomena could be observed; One is producting the polychromosomal form of nucleoids, and is reversible. The second, which is probably a rapid lethal effect, expresses himself by the vesicular form of the nucleoids. The third is only concerned with very high doses. The hypothesis, that the fragmentation of nucleoids may be directly related to induction of lysogenic cells is postulated.     

Tumor necrosis factor as an antineoplastic agent: pitfalls and promises

The discovery and cloning of the cytokine tumor necrosis factor α (TNF) gave rise to new hopes for a significant victory in the war against cancer. Preclinical in vitro studies in cell cultures and in vivo studies in animal models demonstrated the antitumor capacities of TNF. Although clinical studies were largely made possible by the availability of recombinant TNF, phase I and II clinical trials showed very quickly that the systemic administration of TNF induced severe side effects mainly due to its pleiotropic action on immunocompetent cells. The clinical manifestations of the side effects were similar to those observed during a severe infection and inflammation. Very recently, lessons from these clinical studies yielded refined approaches whereby the toxicity of TNF is limited through local administration, a combination with other therapeutic regimens and targeted gene therapy. These new approaches are slated for larger clinical trials and in the near future might demonstrate the limited but powerful usefulness of TNF as an antineoplastic agent for different types of cancer. Received 7 September 1998; received after revision 15 October 1998; accepted 15 October 1998     

Die antibakterielle Wirkung der Usninsäure auf Mykobakterien und andere Mikroorganismen

Summary Usnic acid has already been found in optically active forms in very different quantities in a large number of species of lichens. We have been able to demonstrate the presence of the racemic form of usnic acid as a naturally occuring product in Iceland moss (Cetraria islandica Ach.). The bacteriological examination of the three forms of usnic acid led to the result that, besides an effect uponStaphylococcus aureus, they exert also a very remarkable action againstMycobacteria. The action ofl-usnic acid on different strains ofMycobacteria and other microorganisms is shown in table II. According to the results so far obtained by us, other acids of lichens behave in a similar manner.     

Der Trockenheitssinn bei Larven vonDrosophila Melanogaster

Summary Larvae ofDrosophila melanogaster perceive very small differences of relative humidity if the humidity is high, whereas the perceptible differences are relatively large in dry air. The sense organs for these perceptions are the so-called tufted organs on the ventral side of the thoracic segments. From the fact that the threshold of sensation is high in dry air, we conclude that the absence of humidity irritates the sense organs. We think, therefore, that they are aridity receptors.     

Passaggio di nucleoli attraverso la membrana nucleare negli ovociti in accrescimento diPatella coerulea L. (Moll. Gast. Pros.)

Summary The author has found in increasing ovocytes ofPatella coerulea, particularly in the nuclear membrane, a real passage of small nucleoli from the nucleus to the cytoplasm. Thus not all the nucleoli which appear little by little in the nucleus are amphinucleoli.     

Effect of B-chromosomes on the duration of mitotic cycle in pearl millet

Summary Effect of B-chromosomes on the duration of the mitotic cycle was studied by a colchicine shock method in the root-tip cells of pearl millet (Pennisetum typhoides). 3 B-chromosomes were found to have very little effect, whereas 5 B-chromosomes resulted in an increase of the duration by about 39%.This investigation was financed by the University Grants Commission, New Delhi.     

‘Let the stars shine in peace!’ Niels Bohr and stellar energy, 1929–1934

Faced with various anomalies related to nuclear physics in particular, in 1929 Niels Bohr suggested that energy might not be conserved in the atomic nucleus and the processes involving it. By this radical proposal he hoped not only to get rid of the anomalies but also saw a possibility to explain a puzzle in astrophysics, namely the energy generated by stars. Bohr repeated his suggestion of stellar energy arising ex nihilo on several occasions but without ever going into detail. In fact, it is not very clear what he meant or how seriously he took the stellar energy hypothesis. This paper relates Bohr's comments to the period's attempts to find a mechanism for stellar energy and also to the role played by astrophysics at the Copenhagen institute. Moreover, it looks at how Bohr's hypothesis was received not only by physicists but also by astronomers. In this regard the disciplinary status of astrophysics and its contemporary relation to the new quantum mechanics is of relevance. It turns out that, with very few exceptions, the hypothesis was met with silence by astronomers and astrophysicists concerned with the problem of stellar energy production. And yet, for a brief period of time it did have an impact on how physicists thought about the interior of the stars.     

EGF-induced programmed cell death of human mammary carcinoma MDA-MB-468 cells is preceded by activation of AP-1

MDA-MB-468 is a human mammary adenocarcinoma cell line that overexpresses the epidermal growth factor (EGF) receptor and undergoes programmed cell death (apoptosis) in response to EGF treatment. Programmed cell death was shown to be greatly enhanced when cells were growth-arrested prior to EGF treatment. Apoptosis was characterized by an initial rounding up and detachment of the cells from their substrate starting about 12 h after EGF treatment, followed by chromatin condensation, nuclear fragmentation and oligonucleosomal fragmentation of the DNA at about 24 to 48 h. Cell death was dependent on de novo protein synthesis. We found a rapid induction of c-fos, c-jun and junB at the mRNA level after about 30 min of EGF treatment and a more delayed upregulation of fosB and fra-1. The junD gene was expressed in the absence of EGF, and it was moderately induced within 30 min of growth factor addition. The increase of the different fos and jun mRNAs were paralleled by an increase of activator protein-1 (AP-1) DNA binding activity. A characterization of the AP-1 complex revealed similar levels of several Fos and Jun proteins. Based on the kinetics of AP-1 accumulation and cell death, it seems likely that AP-1 contributes to the apoptotic cell death of EGF receptor-overexpressing MDA-MB-468 cells. Received 21 July 1997; received after revision 6 November 1997; accepted 6 November 1997     

Distribuzione di fosfatasi alcaline in gonadi di Crostacei isopodi in rapporto al ciclo degli acidi nucleici

Summary The distribution of alkaline phosphatases has been studied in male and female gonads of some isopod crustaceans by means of Gomori's reaction.Monophosphatases are found on all Feulgen-positive nuclear structures, in the nucleolus and in the cytoplasm of young oocytes. They disappear from the cytoplasm in auxocytosis, during yolk formation, although they persist in the germinal vesicle. The authors think that the cytoplasmic localization is coincident with ribonucleic acid distribution.From the experiments related in the following note, nucleolar phosphatases appear to be in some way different from the nuclear (sensu stricto) and cytoplasmic phosphatases.Diphosphatases do not follow so closely the nucleic acid localization. They are absent from cytoplasm; in the nucleolus they are not distributed uniformly but show characteristic structure; in the nucleus they are not localized in the chromosomes but homogeneously diffused.     

Nuclear envelope changes related to cell activation inHelianthus tuberosus L.

Summary The ultrastructure of nuclei from dormant and activatedHelianthus tuberosus tuber cells has been investigated with particular reference to nuclear pore frequency and nuclear envelope invaginations, and the results discussed in relation to observations made on other cell types.     

Über den Wirkungscharakter verschiedener Antibiotikain vitro

Summary The mode of action of penicillin onBact. coli is the same as that on staphylococci.The mode of action of 6 different antibiotics was found in 5 cases to be different from that of penicillin.Streptomycin, however, was shown to have at least a very similar action to penicillin on staphylococci, and the same action as penicillin onBact. coli.     

Q-banding and A-T rich DNA inOrnithogalum montanum (Liliaceae)

Summary An A-T rich component was detected by CsCl-actinomycin D centrifugation in nuclear DNAs from three natural populations ofOrnithogalum montanum (Liliaceae). No correlation was found between the Q-banding pattern and the amount of the A-T richest fractions of the genome.Supported by C.N.R. contract No. 74/0267.     

Developmental control of heat shock and chaperone gene expression Hsp70 genes and heat shock factors during preimplantation phase of mouse development

Heat shock genes are found in all organisms, and synthesis of heat shock proteins is induced by various stressors in nearly all the cells forming these organisms. However, a particular situation is noticed for hsp70 genes in mouse embryos at the beginning of their development. First, spontaneous expression of hsp70 is observed at the onset of zygotic genome activity. Second, inducible expression is delayed until morula or early blastocyst stages. A better understanding of both these points depends on a more careful analysis of hsp70 expression in relation to their major regulators, the heat shock factors. In this review, we will see how the development of the preimplanta tion embryo highlights the complexity of heat shock gene regulation involving trans-cis interactions and the cellular and nuclear environment.     

La libération des deux acides nucléiques au cours de l'autolyse des bactéries et sa signification

Summary The existence of a process of directed mutation for aBacterium coli through the action of the desoxyribonucleic acid released by anotherBacterium coli during its autolysis raises the question of the behavior of the two sorts of nucleic acids during the autolytic desintegration of the bacterial cell. Working with several germs, we have seen that autolysis releases a nucleoproteidic fraction containing from 20 to 30 per cent of nucleic acid. The desoxyribonucleic acid represents 50 to 70 per cent of the total nucleic acid; this value is very much higher than that of the initial germs, which contain but 20 to 30 per cent. The signification of the easy mobilization of the desoxyribonucleic acid by autolysis is discussed, according to the observations made in usingRobinow's method of nuclear staining.