Demonstration of "hydroxylase" and "epoxide hydrase" activities in preparations of nucleoli isolated from rat liver]

Aryl hydrocarbon hydroxylase (AHH) activity and epoxyde hydrase (EH) activity have been found in Rat liver nucleoli obtained from untreated (C) and methylcholanthrene (MC) pretreated Rats. Electron microscopic observations of nucleolar preparations did not reveal significant contamination either by intact nuclei or by nuclear membranes. Very low but detectable activity of NADPH cytochrome C reductase was found in the nucleoli. Nucleolar preparations revealed little AHH activity (12-18 pmoles/min/mg). AHH was inducible by MC in nuclei but not in nucleoli. The presence of EH in nucleoli was demonstrated with phenanthrene 9,10-oxide (550-620 pmoles/min/mg) and benzopyrene 4,5-oxide (92-116 pmoles/min/mg). These values were lower than those obtained using intact nuclei. The addition of TCPO (10(-4) M) inhibited EH activity.     

Nucleolar control of p53: a cellular Achilles’ heel and a target for cancer therapy

Nucleoli perform a crucial cell function, ribosome biogenesis, and of critical relevance to the subject of this review, they are also extremely sensitive to cellular stresses, which can cause loss of function and/or associated structural disruption. In recent years, we have learned that cells take advantage of this stress sensitivity of nucleoli, using them as stress sensors. One major protein regulated by this role of nucleoli is the tumor suppressor p53, which is activated in response to diverse cellular injuries in order to exert its onco-protective effects. Here we discuss a model of nucleolar regulation of p53, which proposes that key steps in the promotion of p53 degradation by the ubiquitin ligase MDM2 occur in nucleoli, thus providing an explanation for the observed link between nucleolar disruption and p53 stability. We review current evidence for this compartmentalization in p53 homeostasis and highlight current limitations of the model. Interestingly, a number of current chemotherapeutic agents capable of inducing a p53 response are likely to do so by targeting nucleolar functions and these compounds may serve to inform further improved therapeutic targeting of nucleoli.     

Chemical studies on the silver staining of nucleoli

Summary The uptake of Ag-ions by isolated nucleoli of rat liver cells was studied. Nucleolar proteins separated by electrophoresis were examined for selective silver-staining. A mechanism for a preferential Ag-staining of the nucleoli is discussed.We thank Mrs L. Schwinn for her valuable technical assistance, and Mrs K. Jain for presenting us DNA. We would like to thank the Department of Biology V for making possible the measurements with the atomic absorption spectrophotometer. This work was supported by the Deutsche Forschungsgemeinschaft.     

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.     

Methods for determining ploidy in amphibians: Nucleolar number and erythrocyte size

Summary Diploid and triploidXenopus can be easily and reliably distinguished by the size of their erythrocytes. This method has several advantages over other methods, such as counting metaphase chromosomes and counting nucleoli. One problem with the latter method is the reduction in cells with a full complement of nucleoli when regenerating tissue is used.Research supported by NIH grant EY 01662.     

A comparative study of the correlations existing in the ratio between nucleolar dimensions and number of nucleolini in the oocytes of amphibia

Riassunto Le indagini statistiche effettuate sui nucleoli degli ovociti diRana esculenta, Discoglossus pictus eTriturus cristatus hanno consentito di confermare che i nucleolini, assenti nei nucleoli più piccoli, diventano sempre più numerosi coll'aumentare delle dimensioni dei nucleoli. Nelle tre specie in esame sono stati altresì ottenuti coefficienti di correlazione approssimativamente simili.     

Bau und Funktion der Nukleolen

Summary In previous years the composition and function of chromosomes have been analyzed to a considerable extent, in contrast to the small number of investigations that have been made on nucleoli. There exist at present many conflicting opinions about the structure and function of the nucleolus, and therefore a critical survey of the facts and theories about the nucleolar substance appears necessary.The structure, chemical composition and metabolism of the nucleoli of various cells are described in this publication. The regulation of the size and function of the nucleolus is also discussed.It is concluded that the size and structure of the nucleolus is organ- and species-specific. A rapid synthesis of RNA and proteins occurs in the nucleolus. After a short interval, this disappears; and it is therefore concluded that the nucleolus must have a high turnover of these substances. The size and function of the nucleoli depends on the energy state of the cytoplasm.It appears that the nucleolus can synthesize proteins which can be utilized by the chromosomes during their genetic function.     

Gene amplification in oocytes of the rove beetle Creophilus maxillosus (Staphylinidae, Coleoptera-Polyphaga).

The extra-DNA body was found, for the first time, in oocytes of an insect with telotrophic ovary. Dispersion of this body is accompanied by an enormous increase of nuclear volume and production of multiple nucleoli. It is suggested that the extra-DNA contains a huge mass of nucleolus organizers.     

Murine primitive neuroectodermal tumor: nucleolar isolation and RNA polymerase inhibition.

A nucleolar isolation procedure was developed for the murine primitive neuroectodermal tumor originally induced with methylcholanthrene. This procedure utilizes sonication for breakage of the nuclei at a magnesium concentration which disperses the extranucleolar chromatin. The nucleoli retain RNA synthetic activity which is inhibited to about 90% by actinomycin D and the chemotherapeutic drug adriamycin.     

Feulgen positive nucleoli in Epon semithin sections: fact or artifact?

Epon semithin sections from glutaraldehyde fixed tissues show stained nucleoli after treatment with the Schiff's reagent. The possibility that aldehyde groups already present could account for this positive staining reaction is briefly discussed.     

Gene amplification in oocytes of the rove beetleCreophilus maxillosus (staphylinidae,coleoptera-polyphaga

Summary The extra-DNA body was found, for the first time, in oocytes of an insect with telotrophic ovary. Dispersion of this body is accompanied by an enormous increase of nuclear volume and production of multiple nucleoli. It is suggested that the extra-DNA contains a huge mass of nucleolus organizers.This research was supported in part by funds from the Cytobiology Committee of the Polish Academy of Science.     

Nucleolar hypertrophy and nuclear DNA replication in liver

Summary Hypertrophy of nucleoli is associated with DNA synthesis in the hepatocytes of untreated rats just as it is in stimulated animals. Nucleolar enlargement is not a sufficient change to ensure that the parenchymal liver cell can make DNA.This work was supported by a grant from the National Cancer Institute.     

Murine primitive neuroectodermal tumor: nucleolar isolation and RNA polymerase inhibition

Summary A nucleolar isolation procedure was developed for the murine primitive neuroectodermal tumor originally induced with methylcholanthrene. This procedure utilizes sonication for breakage of the nuclei at a magnesium concentration which disperses the extranucleolar chromatin. The nucleoli retain RNA synthetic activity which is inhibited to about 90% by actinomycin D and the chemotherapeutic drug adriamycin.Acknowledgments. This work was supported in part by USPHS Grant CM-67058. We wish to thank Dr William Brooks for his generous support of this project.     

Differences of the nucleolus in 2 species ofAmyclina (Moll. Gast.)

Summary TwoAmyclina species were examined concerning the more significant anatomo-morphological differences and the different cytological aspects in the nucleoli of growing oocytes.     

Feulgen positive nucleoli in Epon semithin sections: Fact or artifact?

Summary Epon semithin sections from glutaraldehyde fixed tissues show stained nucleoli after treatment with the Schiff's reagent. The possibility that aldehyde groups already present could account for this positive staining reaction is briefly discussed.This work was partially supported by a grant from the Comisión Asesora de Investigación Científica y Técnica, Spain. The author is greatly indebted to O.D. Colman and O. Partearroyo for valuable collaboration.     

Characteristics of the nucleolini observed under the photon microscope

Riassunto I risultati delle ricerche condotte al microscopio fotonico sul nucleolo di cellule vegetali e animali, somatiche e germinali, normali e tumorali hanno permesso di affermare ancora una volta che le sole strutture presenti in esso sono i nucleolini. L'esistenza dei nucleolini è stata comprovata in vivo, come pure con varie tecniche in seguito ad osservazioni compiute con diversi tipi di microscopio. L'analisi statistica effettuata su ovociti diEchinus melo ha permesso di confermare che i nucleolini, che sono assenti nei nucleoli più piccoli, sono poi tanto più numerosi per quanto più elevato è il volume dei nucleoli più grandi.     

Morphological effects of estrogen on the female rat liver nucleolus

Summary Prolonged administration of nonphysiological amounts of estrogen induced markedly enlarged nucleoli volumes in rat hepatocytes, indicative of increased nucleolar RNA synthesis. Physiological amounts of drug had no apparent morphological effects on the hepatocytes.I thank Dr L. Biempica, Department of Pathology, Albert Einstein College of Medicine, for the electron microscopy studies.     

Mitotic karyotype and nucleoli of the marbled newtTriturus marmoratus (Latreille)

Riassunto I cromosomi mitotici diTriturus marmoratus sono stati ordinati in cariotipo. Gli organizzatori nucleolari sono due per cellula, ma negli spermatogoni primitivi sono presenti numerosi nucleoli liberi.

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With financial support by Consiglio Nazionale delle Ricerche, Rome.     

Gold nanoparticles induce nuclear damage in breast cancer cells,which is further amplified by hyperthermia

Gold nanoparticles have emerged as promising tools for cancer research and therapy, where they can promote thermal killing. The molecular mechanisms underlying these events are not fully understood. The geometry and size of gold nanoparticles can determine the severity of cellular damage. Therefore, small and big gold nanospheres as well as gold nanoflowers were evaluated side-by-side. To obtain quantitative data at the subcellular and molecular level, we assessed how gold nanoparticles, either alone or in combination with mild hyperthermia, altered the physiology of cultured human breast cancer cells. Our analyses focused on the nucleus, because this organelle is essential for cell survival. We showed that all the examined gold nanoparticles associated with nuclei. However, their biological effects were quantitatively different. Thus, depending on the shape and size, gold nanoparticles changed multiple nuclear parameters. They redistributed stress-sensitive regulators of nuclear biology, altered the nuclear morphology, reorganized nuclear laminae and envelopes, and inhibited nucleolar functions. In particular, gold nanoparticles reduced the de novo biosynthesis of RNA in nucleoli, the subnuclear compartments that produce ribosomes. While small gold nanospheres and nanoflowers, but not big gold nanospheres, damaged the nucleus at normal growth temperature, several of these defects were further exacerbated by mild hyperthermia. Taken together, the toxicity of gold nanoparticles correlated with changes in nuclear organization and function. These results emphasize that the cell nucleus is a prominent target for gold nanoparticles of different morphologies. Moreover, we demonstrated that RNA synthesis in nucleoli provides quantitative information on nuclear damage and cancer cell survival.