Chromosomes of the North American prairie dogCynomys ludovicianus

Zusammenfassung Die Analyse der mitotischen Chromosomen beiCynomys ludovicianus ergibt die diploide Zahl 50 und einen Karyotypen mit nur metazentrischen und submetazentrischen Autosomen. Der FallCynomys ist einzigartig unter den Sciuridae: hohe 2n Zahl und Fehlen acrozentrischer Chromosomen.     

Chromosomes of three Asian mammals:Meriones meridianus (Rodentia: Gerbillinae),Spermophilopsis leptodactylus (Rodentia: Sciuridae),Ochotona rufescens (Lagomorpha: Ochotonidae)

Zusammenfassung Chromosomenanalyse von 3 asiatischen Säugetieren:Meriones meridianus (2n=50),Ochotona rufescens (2n=60) undSpermiophilopsis lepto-dactylus (2n=38), Deren 2n's und Karyotypen wurden mit verwandten Formen ninsichtlich der Geschlechter und Gattungen verglichen und zur Klassifizierung diskutiert.     

Monoclonal antibody identifies a new Ia-like (p29,34) polymorphic system linked to the HLA-D/DR region

The Ia antigens of the mouse are the basis for the genetic control of the immune response. The HLA-D/DR locus is considered to be the human counterpart of the Ia subregion of the murine major histocompatibility complex. The HLA-D/DR antigens are polymorphic, and eight well defined alleles have been identified using alloantisera. More recently, 'supertypic' antigens (MB and MT) have been defined which identify clusters of HLA-D/DR specificities. Little is known about the molecular basis for the cellular and serological polymorphism of the HLA-D/DR antigens, as alloantisera are usually of very low titre and heteroantisera frequently lack monospecificity. We present here the preparation and characterization of a monoclonal antibody which defines a new polymorphic system of the HLA-D/DR region. This and similar antisera should now begin to provide the reagents with which to correlate molecular structure with the functional repertoire of the human Ia-like antigens.     

Inositol 1,4,5-trisphosphate mimics muscarinic response in Xenopus oocytes

The enhanced metabolism of phosphoinositides, which is associated with a wide variety of stimuli and physiological responses, has been studied intensively. Berridge and his collaborators demonstrated that the first measurable reaction following cell membrane receptor activation is a rapid hydrolysis of phosphatidylinositol 4,5-bisphosphate (PtdIns(4,5)P2), and that the product of this reaction, inositol 1,4,5-trisphosphate (Ins(1,4,5)P3), could cause a release of non-mitochondrial calcium. These findings have been verified in other systems. Although the relationship between the hydrolysis of PtdIns(4,5)P2 and the mobilization of intracellular calcium was clearly demonstrated, the direct link between Ins(1,4,5)P3 production and the physiological response was only implied. We have investigated the possibility that the intracellular release of Ins(1,4,5)P3 mediates the muscarinic-cholinergic response is Xenopus oocytes, and we show here that intracellularly injected Ins(1,4,5)P3 mimics the muscarinic depolarizing chloride current in Xenopus oocytes. This is the first demonstration of a direct link between phosphoinositides metabolism and a neuro-transmitter-induced physiological response.     

Chromosomes and systematics of some north American species of the genusMarmota (Rodentia: Sciuridae)

Zusammenfassung Die Zahl der diploiden Chromosomen vonMarmota caligata undM. flaviventris ist 42 in Bevölkerungen der nördlichen und südlichen Verbreitungsgebiete beider Spezies. Ein Vergleich zwischen den bisher veröffentlichten Informationen überMarmota-Chromosomen mit Angaben über ihre Morphologie, Ekologie, Zoogeographie legt nahe, dass die ursprüngliche Chromosomenzahl 2n 38–40 war.

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Supported by National Science Foundation Grant Nos. GB-3251 and GB-5428, and by a National Academy of Sciences US-USSR Exchange Fellowship. We thank Dr.D. L. Pattie for generously providing the specimen ofM. flaviventris and Mrs.Gabriele Forrester for preparation of theM. c. nivaria chromosomes.     

Chromosomes of some Asian and South American squirrels (rodentia: Sciuridae)

Zusammenfassung Chromosomensätze verschiedener Sciurinae sind:Sciurus anomalus (2n=40),S. granatensis (2n=42),Callosciurus flavimanus (2n=40),Dremomys rufigenis (2n=38) undMenetes berdmorei (2n= 62). Ein Vergleich mit früher beschriebenen Sciurinae-Karyotypen ergibt als ursprünglich diploide Sätze 38–40, Spaltung, sowie Fusion zu grösseren und kleineren2n's führend.     

LTRPC7 is a Mg.ATP-regulated divalent cation channel required for cell viability

The molecular mechanisms that regulate basal or background entry of divalent cations into mammalian cells are poorly understood. Here we describe the cloning and functional characterization of a Ca2+- and Mg2+-permeable divalent cation channel, LTRPC7 (nomenclature compatible with that proposed in ref. 1), a new member of the LTRPC family of putative ion channels. Targeted deletion of LTRPC7 in DT-40 B cells was lethal, indicating that LTRPC7 has a fundamental and nonredundant role in cellular physiology. Electrophysiological analysis of HEK-293 cells overexpressing recombinant LTRPC7 showed large currents regulated by millimolar levels of intracellular Mg.ATP and Mg.GTP with the permeation properties of a voltage-independent divalent cation influx pathway. Analysis of several cultured cell types demonstrated small magnesium-nucleotide-regulated metal ion currents (MagNuM) with regulation and permeation properties essentially identical to the large currents observed in cells expressing recombinant LTRPC7. Our data indicate that LTRPC7, by virtue of its sensitivity to physiological Mg.ATP levels, may be involved in a fundamental process that adjusts plasma membrane divalent cation fluxes according to the metabolic state of the cell.