Subcellular localization of lethal lysis proteins of bacteriophages lambda and phiX174.

The gene products of the lethal lysis genes S and E of the bacteriophages lambda and phiX174, respectively, were shown to be associated primarily with inner membrane material by isopycnic sucrose gradient centrifugation of lysates of infected cells. A small amount of each polypeptide appeared to be in the outer membrane fraction.     

Alkaline-phosphatase and adenosine-triphosphatase histochemical reactions in the salivary glands of cat,dog and man,with particular reference to the myoepithelial cells

Summary Salivary myoepithelial cells were demonstrated by alkaline-phosphatase techniques in cat, but not in man or dog, and by an adenosine-triphosphatase technique in man, but not in cat or dog.Electron-microscopical cytochemistry showed that the reaction product from the respective techniques in cat and man was associated with the myoepithelial plasma membrane and that it was most constant and usually strongest at the plasma membrane adjacent to the acinar cells.In the dog, the reaction product from the adenosine-triphosphatase technique was found lining the canaliculi and lumina of the acini of the parotid gland, and of the non-mucous acini of the submandibular and sublingual glands. Alkaline-phosphatase reaction product was found lining the canaliculi and lumina in the sublingual gland.These remarkable species differences indicate that neither technique can be regarded as a universal marker of salivary myoepithelial cells. Inconsistencies in activity were found within the myoepithelium of individual glands and suggest that even the appropriate technique may not be relied upon to demonstrate all the myoepithelial cells present in a tissue section.

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Zusammenfassung Myoepithelzellen der Speicheldrüsen lassen sich bei der Katze — nicht jedoch bei Mensch und Hund — mittels der alkalischen Phosphatase-Reaktion darstellen. Der Nachweis für Adenosintriphosphatase fällt in diesen Zellen beim Menschen, nicht bei Katze und Hund, positiv aus.Elektronenmikroskopisch-cytochemisch zeigt sich, daß das Reaktionsprodukt der jeweiligen Methode bei der Katze und beim Menschen an den Plasmamembranen der Myoepithelzellen auftritt und zwar am regelmäßigsten und meistens am stärksten in der Nachbarschaft der Azinuszellen.Beim Hund fällt in der Ohrspeicheldrüse sowie den nicht-mukösen Acini der Glandulae submandibularis und sublingualis das Reaktionsprodukt der Adenosintriphosphatase-Reaktion an der Begrenzung der Azinuskanälchen und der Lumenoberfläche aus. Alkalische Phosphatase ist in der Glandula sublingualis in den Wänden der Kanälchen und an den Lumina lokalisiert.Diese bemerkenswerten Unterschiede zwischen den verschiedenen Tierarten zeigen, daß keine der verwendeten Methoden zur Universalmarkierung von Myoepithelzellen der Speicheldrüsen geeignet ist. Außerdem ist die Aktivität des Myoepithels bei den einzelnen Drüsen uneinheitlich. Dies legt die Vermutung nahe, daß man sich selbst bei Anwendung der richtigen Methode nicht darauf verlassen kann, alle in einem Gewebsschnitt vorhandenen Myoepithelzellen zu erfassen.

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This work has been supported by a Medical Research Council Grant.     

Suppression of a yeast cyclic AMP-dependent protein kinase defect by overexpression of SOK1, a yeast gene exhibiting sequence similarity to a developmentally regulated mouse gene.

Saccharomyces cerevisiae cyclic AMP-dependent protein kinase (A kinase) activity is essential for growth and cell cycle progression. Dependence on A kinase function can be partially relieved by the inactivation of a second kinase encoded by the gene YAK1. We have isolated two new genes, SOK1 and SOK2 (suppressor of kinase), as gene dosage suppressors of the conditional growth defect of several temperature-sensitive A kinase mutants. Overexpression of SOK1, like lesions in YAK1, also restores growth to a strain (tpk1 tpk2 tpk3) lacking all A kinase activity. The SOK1 gene is not essential, but a sok1::HIS3 disruption abrogates suppression of an A kinase defect by yak1. These results suggest that Yak1 and Sok1 define a linear pathway that is partially redundant with that of the A kinase. Activation of Sok1, by SOK1 overexpression or by inactivation of the negative regulator Yak1, renders a cell independent of A kinase function. The implications of such a model are particularly intriguing in light of the nuclear localization pattern of the overexpressed Sok1 protein and the primary sequence homology between SOK1 and a recently described, developmentally regulated mouse gene.     

Adventitious shoot production from immature embryos of white clover

Cotyledonary-stage embryos of Haifa white clover, collected 13 days after cross-pollination, were induced to form adventitious shoots primarily from the hypocotyl region. The culture medium used for the production of adventitious shoots contained 5 M thidiazuron and 0.5 M -naphthaleneacetic acid. Numerous shoot meristems were produced within the first week, discrete shoots developed by week three, small plantlets by week eight, and whole plants in soil by week ten. 95–100% of all embryos, regardless of genotype, produced adventitious shoots within four weeks with an average production of 17.5 shoots per embryo. The majority of shoots (on average 77%) were easily converted to whole plants in soil. The white clover regeneration system described is prolific, rapid and effective on a large number of genotypes.Abbreviations BA N⁶-benzylaminopurine - MS medium Murashige & Skoog medium (1962) - NAA -naphthaleneacetic acid - thidiazuron N-phenyl-N-1,2,3-thiadiazol-5-ylurea     

The nucleotide sequence of the 16S ribosomal RNA gene of the archaebacterium Halococcus morrhua.

The sequence of the 16S rRNA gene from the archaebacterium Halococcus morrhua was determined by the dideoxynucleotide sequencing method. It is 1475 nucleotides long. This is the second archaebacterial sequence to be determined and it provides sequence comparison evidence for the secondary structural elements confined to the RNAs of this kingdom and, also, support for controversial or additional base pairing in the eubacterial RNAs. Six structural features are localized that have varied during the evolution of the archaebacteria, eubacteria and eukaryotes. Moreover, although the secondary structures of both sequenced archaebacterial RNAs strongly resemble those of eubacteria, they contain sufficient eukaryotic-like structural characteristics to reinforce the view that they belong to a separate line of evolutionary descent.     

The role fo glutamine synthetase and glutamine metabolism in nitrogen metabolite repression, a regulatory phenomenon in the lower eukaryote Neurospora crassa

Summary Growth of Neurospora crassa on media containing NH ₄ ⁺ leads to the repression of a variety of permeases and alternative pathways which would generate NH ₄ ⁺ , so called ammonium repression. The mutant am ₂ which lacks NADP-GDH is not subject to ammonium repression of nitrate reductase or urea permease, but like the wild type has repressed levels of these systems when grown in the presence of proline, glutamate or glutamine. The glutamine synthetase (GS) mutant gln-la has derepressed levels of the aforementioned systems unless grown with glutamine.The oligomeric state of GS depends upon the nitrogen sufficiency of the cell, a tetrameric form predominates under conditions of nitrogen limitation and an octameric form under conditions of nitrogen sufficiency. We have found that the tetrameric form GS predominates in the mutants am ₂ and gln-la when they are ammonium derepressed.The mechanism of NH ₄ ⁺ repression in N. crassa is thought to entail a cessation of positive gene action by the product of the nit-2 regulatory gene. We propose that under conditions of NH ₄ ⁺ sufficiency, and hence glutamine sufficiency, the octameric form of GS represses nit-2 gene expression and thereby achieves ammonium repression.