Erratum: Formation of galaxies and large-scale structure with cold dark matter

Abstract

2 3 4 5 6 2 3 4 5 6 Fig. 3 Phosphorylation of the myosin light chain is unaffected by replacement of sodium chloride with choline chloride and sodium channel blockers. Platelets were preincubated with labelled phosphate as Fig. 2 and then gel filtered either in buffer A, or in buffer A with the sodium chloride replaced with choline chloride plus I mM amiloride. To the experimental samples, 2 ILM tetrodotoxin was added also for 10 min before adding thrombin or placing the platelets at 5 oc for I h. Left panel, lanes 1-3, whole platelet lysates from resting, thrombin treated (0.1 U ml-1 ) and 60 min chilling; lanes 4-6, the same treatments but with sodium replaced by choline and with the addition of amiloride and tetrodotoxin as above. Right panel, cytoskeletons from the same experiment. Arrows, the positions of myosin light chain and a relative molecular mass M, 36,000 protein of unknown properties which appears in the cytoskeleton after chilling but not after thrombin treatment. Both thrombin and cold cause increased phosphorylation of a band with mobility of myosin light chain, and also of aM, 47,000 band which is present in the supernatants but not in the cytoskeletons. Densitometry of this and similar gels was used to derive an estimate of the extent of phosphorylation in cold compared with thrombin phosphorylation.be due to external calcium. To examine shape change, we scored more than 100 gel-filtered platelets fixed in 2% formaldehyde/2% glutaraldehyde at several time-points after chilling. The use of thick layers ·of fluid allowed us to see each scored platelet on edge. We distinguished four states: disks without filopodia, disks with filopodia, irregular or distorted disks and fully altered platelets (irr~gular spheres). Our results show that at 37 °C platelets are 99% discoid, but 70% of them have one or two filopodia. Chilled platelets become progressively more distorted from the disk shape until they are fully altered. After 20 minutes, 81% are distorted and 17% fully shape changed and after 60 minutes 81% are fuliy altered and 16% distorted. Many distorted disks but no spheres ar~ present after l 0 minutes of chilling. These disks can be considered fully altered if not compared carefully with later stages. Thus, the degree of phosphorylation (Table l) in our experiments parallels quite well the degree of shape change from disk to fully altered sphere. The protrusion of filopodia, however, does not appear to depend on myosin phosphorylation as suggested by previous work on the in vitro formation of actin bundles without myosin 7 • As shape change has been thought to depend on microtubule breakdown, we also tested the effects of adding Taxol to gel filtered platelets at 30 !J.M for 10 minutes before chilling for 1 hour. This treatment preserved the microtubule ring as shown in electron micrographs (taken by Dr Fern Tablin), but did not prevent the appearance of irregular spheres by phase or electron microscopy. This retention of cold-induced shape change is in agreement with previous results where Taxo...

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