Magnesium ions in catecholamine fluorescence histochemistry

Summary The effects of high concentrations of magnesium ions in the cryostat and Vibratome procedures for visualization of catecholamine fluorescence in the central nervous system have been investigated. In cryostat sections, obtained from specimens perfused with a formaldehyde and glyoxylic acid containing buffer, the addition of high concentrations of MgSO₄ to the perfusion solution enhances the fluorescence intensity and reduces the unspecific background fluorescence and the diffusion of the catecholamine fluorophore. This improves the visualization of all portions of the central catecholamine-containing neurons. Similar effects are obtained in the formaldehyde-Vibratome technique by the introduction of an immersion bath containing MgSO₄ after the sectioning procedure. The use of the magnesium perfusion or immersion steps furthermore increases the reproducibility of the Vibratome and cryostat techniques. The paper describes the improved Vibratome and cryostat techniques used in our laboratory.     

Areal distribution of a Neodiprion sertifer (Hym., Diprionidae) outbreak on Scots pine as related to stand condition

Analyses of a recent N. sertifer outbreak in southern Sweden were made during on-going attack, comprising a regional and local mapping of defoliation severity, as well as a study of intensity of larval consumption, abundance of cocoons and parasitation of larvae in relation to fertilizer application. It was found that (1) the outbreak was preceded by summer and autumn droughts, (2) it was limited to infertile soils, (3) pine stands aged 20–40 yr suffered most, (4) it was less severe in trees benefiting from a reduced inter-tree competition, as measured from tree-ring growth, and (5) less severe in a fertilized stand. The findings support the hypothesis on a fundamental effect of stand nutritive state on changes in number of the sawfly.     

Oxidation of pyrite by Acidianus brierleyi: Importance of close contact between the pyrite and the microorganisms

Experiments were done in order to study the thermophilic archaebacterium Acidianus brierleyi during oxidation of pyrite (FeS₂). The microorganisms were grown both separated from the pyrite by a membrane and in close contact with the pyrite. From the results it can be concluded that direct contact is needed for good growth of the strain studied. The obtained results indicate that the direct contact mechanism may be applied to oxidation of sulfidic minerals by A. brierleyi.     

Molecular properties and odour. Effects of substituents on pyridine and pyridine odour

It is investigated how the odour of pyridine changes when substituents of different kinds are inserted on the pyridine ring. The relation between the space filling and electronic properties of molecules and odour is studied. Far infrared spectra have been recorded for pyridines in order to test a hypothetical correlation between odour and vibrational energies.     

Mevalonate-regulated mechanisms in cell growth control: role of dolichyl phosphate in expression of the insulin-like growth factor-1 receptor (IGF-1R) in comparison to Ras prenylation and expression of c-myc

One or more mevalonate derivatives of non-sterol type have beenproposed to be of indispensable importance for cell growth.Conceivable mevalonate-dependent mechanisms involved in growthcontrol are farnesylation of Ras proteins, regulation of c-mycexpression, and N-linked glycosylation of the IGF-1 receptor.The latter mechanism might be rate-limited by dolichyl phosphate,which acts as a donor of oligosaccharides in glycoprotein synthesisin the endoplasmic reticulum. In order to study the significancefor cell proliferation of the three aforementioned mevalonate-dependentprocessings, their inhibitory response due to mevalonate deprivationwas explored and compared with the effect on DNA synthesis inthe malignant melanoma cell line SK-MEL-2. We found that mevalonatedepletion due to treatment with 3 µM lovastatin for 24h, which efficiently growth-arrested the cells, hardly at allaffected the expression of c-myc, and although Ras prenylationwas inhibited by 50%, the most pronounced effect of lovastatinwas seen on N-linked glycosylation of IGF-1 receptors, whichwas inhibited by more than 95%. The order and magnitude of thedecreased IGF-1 receptor glycosylation, which was followed bya decreased expression of IGF-1 receptors at the cell membrane,correlated well with the inhibition of DNA synthesis. We investigatedwhether dolichol, and in particular dolichyl phosphate, throughits participation in N-linked glycosylation, act as regulatorsof IGF-1 receptor expression. First, we could confirm that exogenousdolichol became phosphorylated and in this form took part inthe glycosylation processing. Secondly, we showed that dolichylphosphate, in a dose-dependent manner, could increase the numberof IGF-1 receptors at the cell membrane, simultaneously as DNAsynthesis was stimulated. Taken together, our results providedirect evidence for an important role of dolichyl phosphateas a regulator of cell growth through limiting N-linked glycosylationof the IGF-1 receptor. dolichyl phosphate IGF-1 receptor c-myc N-linked glycosylation Ras     

On the electronic structure and odours of esters of the isothiocyanic acid

The electronic structure of the esters of the isothiocyanic acid is calculated in an iterative extended Hückel method. Contour diagrams of the valence electron density are given. The odour character of these molecules is discussed in terms of the electronic structure obtained and the theories of smell put forward by Amoore and Wright respectively.