University of Dundee

About: University of Dundee is a education organization based out in Dundee, United Kingdom. It is known for research contribution in the topics: Population & Protein kinase A. The organization has 19258 authors who have published 39640 publications receiving 1919433 citations. The organization is also known as: Universitas Dundensis & Dundee University.

Use of infrared thermography for monitoring stomatal closure in the field: application to grapevine

Abstract: This paper reviews and discusses strategies for the use of thermal imaging for studies of stomatal con ductance in the field and compares techniques for image collection and analysis. Measurements were taken under a range of environmental conditions and on sunlit and shaded canopies to illustrate the vari ability of temperatures and derived stress indices. A simple procedure is presented for correcting for cali bration drift within the images from the low-cost thermal imager used (Snapshot 225, Infrared Solutions, Inc.). The use of wet and dry reference surfaces as thresholds to eliminate the inclusion of non-leaf material in the analysis of canopy tempera ture is discussed. An index that is proportional to stomatal conductance was compared with stomatal measurements with a porometer. The advantages and disadvantages of a possible new approach to the use of thermal imagery for the detection of stomatal closure in grapevine canopies, based on an analysis of the temperature of shaded leaves, rather than sunlit leaves, are discussed. Evidence is presented that the temperature of reference surfaces exposed within the canopy can be affected by the canopy water status.

MAPKAP kinase-2; a novel protein kinase activated by mitogen-activated protein kinase.

Abstract: A novel protein kinase, which was only active when phosphorylated by the mitogen-activated protein kinase (MAP kinase), has been purified 85,000-fold to homogeneity from rabbit skeletal muscle. This MAP kinase activated protein kinase, termed MAPKAP kinase-2, was distinguished from S6 kinase-II (MAPKAP kinase-1) by its response to inhibitors, lack of phosphorylation of S6 peptides and amino acid sequence. MAPKAP kinase-2 phosphorylated glycogen synthase at Ser7 and the equivalent serine (*) in the peptide KKPLNRTLS*VASLPGLamide whose sequence is similar to the N terminus of glycogen synthase. MAPKAP kinase-2 was resolved into two monomeric species of apparent molecular mass 60 and 53 kDa that had similar specific activities and substrate specificities. Peptide sequences of the 60 and 53 kDa species were identical, indicating that they are either closely related isoforms or derived from the same gene. MAP kinase activated the 60 and 53 kDa forms of MAPKAP kinase-2 by phosphorylating the first threonine residue in the sequence VPQTPLHTSR. Furthermore, Mono Q chromatography of extracts from rat phaeochromocytoma and skeletal muscle demonstrated that two MAP kinase isoforms (p42mapk and p44mapk) were the only enzymes in these cells that were capable of reactivating MAPKAP kinase-2. These results indicate that MAP kinase activates at least two distinct protein kinases, suggesting that it represents a point at which the growth factor-stimulated protein kinase cascade bifurcates.

Mitochondria, calcium regulation, and acute glutamate excitotoxicity in cultured cerebellar granule cells.

Abstract: Exposure of cultured cerebellar granule cells to 100 μM glutamate plus glycine in the absence of Mg 2+ causes calcium loading of the in situ mitochondria and is excitotoxic, as demonstrated by a collapse of the cellular ATP/ADP ratio, cytoplasmic Ca 2+ deregulation (the failure of the cell to maintain a stable cytoplasmic free Ca 2+ concentration), and extensive cell death. Glutamate-evoked Ca 2+ deregulation is exacerbated by the mitochondrial respiratory chain inhibitor rotenone. Cells maintained by glycolytic ATP, i.e., in the presence of the mitochondrial ATP synthase inhibitor oligomycin, remain viable for several hours but are still susceptible to glutamate; thus, disruption of mitochondrial ATP synthesis is not a necessary step in glutamate excitotoxicity. In contrast, the combination of rotenone (or antimycin A) plus oligomycin, which collapses the mitochondrial membrane potential, therefore preventing mitochondrial Ca 2+ transport, allows glutamate-exposed cells to maintain a high ATP/ADP ratio while accumulating little 45 Ca 2+ and maintaining a low bulk cytoplasmic free Ca 2+ concentration determined by fura-2. It is concluded that mitochondrial Ca 2+ accumulation is a necessary intermediate in glutamate excitotoxicity, whereas the decreased Ca 2+ flux into cells with depolarized mitochondria may reflect a feedback inhibition of the NMDA receptor mediated by localized Ca 2+ accumulation in a microdomain accessible to the mitochondria.