Mitotic Centromere–associated Kinesin Is Important for Anaphase Chromosome Segregation

Mitotic centromere–associated kinesin (MCAK) is recruited to the centromere at prophase and remains centromere associated until after telophase. MCAK is a homodimer that is encoded by a single gene and has no associated subunits. A motorless version of MCAK that binds centromeres but not microtubules disrupts chromosome segregation during anaphase. Antisense-induced depletion of MCAK results in the same defect. MCAK overexpression induces centromere-independent bundling and eventual loss of spindle microtubule polymer suggesting that centromere-associated bundling and/or depolymerization activity is required for anaphase. Live cell imaging indicates that MCAK may be required to coordinate the onset of sister centromere separation.     

Timing and duration of moult in three populations of Purple Sandpipers Calidris maritima with different moult/migration patterns

Timing and duration of primary moult in three populations of Purple Sandpipers Calidris maritima were described and discussed in relation to the birds’ need to complete moult before the onset of winter, when resources are required for survival. We predicted that moult would be completed earlier by birds wintering at higher latitudes. The south Norwegian breeding population, which moults and winters along the coast of east Britain (54–57°N) had a mean starting date of 21 July for primary moult (16 July for females and 24 July for males), a mean duration of 61 days, and completed on 20 September. Resident Icelandic (64–65°N) birds had a mean starting date of 22 July for primary moult (17 July for females and 25 July for males), a mean duration of 51 days, and completed on 11 September. Birds moulting in north Norway (70°N) arrived in north Norway in suspended primary moult or without having started moult, and completed it there. They had a mean completion date of 2 November for primary moult (31 October for females and 3 November for males). Starting date and duration could not be estimated because some suspended moult for an undetermined period, but it was thought that they started in late August. It is likely that most originated from Russia. The onset of moult appears to be set by the end of breeding and there is little overlap in these two events. The earlier start of moult by females in all three populations may be because they abandon the males when the chicks hatch, leaving the males to attend the chicks. Although the duration of primary moult followed the expected trend, being fastest in north Norway and slowest in Britain, the onset of moult was so late in north Norway that they had an unexpectedly late completion date, despite their rapid moult. The late completion of primary moult in north Norway suggests that wintering in the far north may not pose the energetic constraints on Purple Sandpipers that had previously been supposed.     

Thermal stability: a means to assure tertiary structure in therapeutic proteins.

To be both safe and effective, a therapeutic product must have the correct chemical structure and be free of harmful contaminants. Structure in protein therapeutic products, however, implies not only the correct sequence of amino acids (primary structure) but also the proper folding of that amino acid chain in three-dimensional space (tertiary structure). This work is part of a general strategy to develop a battery of physico-chemical methods that could give assurances of structure (and hence function) in formulated therapeutic proteins in the absence of in vivo data. It focuses on recombinant human growth hormone (rhGH), a well-characterized therapeutic protein, and examines the utility of thermodynamic parameters in assessing its tertiary structure. Resistance of solutions of formulated rhGH to thermal denaturation was followed using Fourier Transform Infrared Spectroscopy (FTIR) by observing decreases in total helicity and increases in intermolecular beta-sheet formation. Under conditions known to induce changes in the intra-molecular ionic and H-bonding patterns stabilizing the tertiary structure but not affecting the protein's secondary structure or global fold, we have observed upwards of a 12 degrees C shift in the melting temperature of the protein. Furthermore, our results indicated that the T(m) of unfolding of rhGH was sensitive to much more subtle changes in the protein structure. Thus, resistance to thermal denaturation may well be a useful means to measure structure in formulations of well-characterized therapeutic proteins.     

Free fatty acids, neutral and polar lipids in Hordeum vulgare exposed to long-term fumigation with SO2

Three 9-day-old cultivars of Hordeum vulgare L. (Barberousse, Gerbel and Panda) were exposed to low levels of SO₂ fumigation (40 ± 5 and 117 ± 20 ppb). After 48 days of treatment the seedlings were harvested for lipid analysis. In comparison to the control (plants exposed to charcoal-filtered air), the total lipid content of fumigated seedlings declined at 40 ppb SO₂ and even more so at 117 ppb in all three cultivars. A large reduction in diacylglycerols. polar lipids and free sterols was also observed after fumigations at both SO₂ concentrations, whereas the treatments resulted in an increase in triacylglycerols and free fatty acids. The percentage composition of total fatty acids and that of each lipid class were changed by the fumigations. resulting in an increase in the degree of unsaturation. No changes in the percentage composition of sterols occurred in the fumigated leaves. These results suggest that even if SO₂ may not directly oxidize unsaturated fatty acids at the low concentrations used here (which do not cause visible injury). it may alter lipid metabolism. This alteration. which was particularly evident in the polar lipids and sterols, could affect the functions associated with membrane stabilization, in which lipids plus sterols play a key part.     

Degradation of membrane lipid components and antiovidanl levels in Hordeum vulgare exposed to long-term fumigation with SO2

Hordeum vulgare L. (cv. Barberousse) seedlings were continuosly exposed to SO₂ (40±5 and 117±20 ppb) for 48 days and compared to control plants exposed to charcoal-filtered air. Glyco-and phospolipid amounts were strongly affected by exposure to SO_2:, and decreased with increasing SO₂, fumigation. The chloroplast membranes of fumigated leaves were characterized by lower quantities of rnonogalacto-syldiacylglycerol (MGDG) as well as of sulphoquinovosyldiacylglycerol (SQDG). Among the phospholipids a decrease in the phosphatidylglycerol (PG) content was observed, indicating that the chloroplast membranes are affected even by such low concentrations of SO₂ as used here. As for the other phospholipids, phosphatidylcholine (PC) and phosphatidylinositol (PI) suffered a reduction and phosphatidylethano-lairrine (PE) almost disappeared at the highest SO₂, concentration, whereas phosphatidic acid (PA) followed the opposite trend. The fatty acids of both glyco- and phospholipids fell sharply upon fumigation without any decline in the degree of unsataration. In particuSar, neither linoleic nor linolenic acid showed any evident change in level, suggesting that no lipid peroxidation of polytmsaturated fatty acid tails occurred. Furthermore, the electron spin resonance (ESR) showed no differences in the free radical levels between control and fumigated leaves. The level of malondialdehyde (MDA) decreased, while lipid-soluble antioxidants, as well as superoxide dismutase (SOD; EC 1.15.1.1) and catalase (EC 1.11.1.6) activities increased with the increase in SO₂ concentration, providing evidence that defence mechanisms against oxy-radical action are activated by the plants at low levels of SO₂,. Even if SO₂, at low concentrations may not directly oxidize polyunsaturated fatty acids, it may act as a deesterifying factor on each component of both glyco- and phospholipids.