ALBERT

Notes: Abstract Quantitative tectonic modelling demonstrates an interaction of flexure of the lithosphere underlying the western Betics with crustal thinning in the Alboran Basin and flank uplift in the Internal Zone. In the eastern Betics the flexural response is overprinted by post-thrusting extensional events. Lateral variations in thermal structure and rheology of the lithosphere along strike of the Betics shed light on changes in tectonic configuration and are consistent with evidence for lateral variations in the mode of extension in the Alboran Basin. Flexural modelling and subsidence analysis of Neogene basins in the Internal Zone of the Betics, with spatial development controlled by contrasts in lithosphere rheology, demonstrate that at least two extensional events have affected the orogenic evolution of the Betics. The first event appears to reflect Oligocene-Early Miocene rifting observed throughout the Western Mediterranean. The second phase, which caused the present configuration of the Betics, corresponds to Tortonian-Recent extension centered in the Alboran Basin.

Notes: Summary Single fibres of different sarcomere length at rest have been isolated from the claw muscle of the yabby (Cherax destructor), a decapod crustacean. Fibres of either long (SL 〉 6 μm) or short (SL 〈 4 μm) sarcomere length have been mechanically skinned and were maximally activated by Ca2+ and Sr2+ under various experimental conditions (ionic strength, in the presence of 2,3 butanedione monoxime (BDM)) to determine differences in their contractile properties. Isometric force was measured simultaneously with either myofibrillar MgATPase or fibre stiffness in both fibre types. The ultrastructure of individual long- and short-sarcomere fibres was also determined by electron microscopy. The long-sarcomere fibres developed greater tension (30.48±1.72 N cm−2) when maximally activated by Ca2+ compared with the short-sarcomere fibres (18.60±0.80 N cm−2). The difference in the maximum Ca2+-activated force can be explained by the difference in the amount of filament overlap between the two fibre types. The maximum Ca2+-activated myofibrillar MgATPase rate in the short-sarcomere fibres (1.60±0.27 mmol ATP l−1 s−1) was higher, but not significantly different from the ATPase rate in fibres with long-sarcomeres (1.09±0.14 mmol ATP l−1 s−1). As the concentration of myosin is estimated to be higher only by a factor of 1.22 in the short-sarcomere preparations there is no evidence to suggest that the myofibrillar MgATPase activity is different in the long- and short-sarcomere preparations. The maximum Ca2+-activated force (P 0) of both short- and long-sarcomere fibres was quite insensitive to BDM compared with vertebrate muscle. Force decreased to 60.2±5.3% and 76.1±2.7% in the short- and long-sarcomere fibres respectively in the presence of 100 mmol l−1 BDM. The difference in the force depression between the. long- and short-sarcomere fibres is statistically significant (p〈0.05). Fibre stiffness during maximum Ca2+-activation expressed as percentage maximum force per nm per half sarcomere was higher by a factor of 3.5 in short-sarcomere fibres than in long-sarcomere fibres suggesting that the compliance of the filaments in the long-sarcomere fibres is considerably higher than in the short-sarcomere fibres. Sr2+ could not activate the contractile apparatus to the same level as that seen by Ca2+ in either fibre type: the maximum Sr2+-activated force was (20±3%) and (63±3%) of the maximum Ca2+-activated force response in short- and long-sarcomere fibres, respectively. The ratio between fibre stiffness in the maximum Sr2+-activating solution and the Ca2+-activating solution was very similar to the ratio between the maximum Sr2+-activated force and Ca2+-activated force in either type of fibres, suggesting that the number of attached crossbridges is lower in the fibres when maximally activated by Sr2+ than when maximally activated by Ca2+. The short-sarcomere fibres were also more sensitive to changes in ionic strength than long-sarcomere fibres. In conclusion these results indicate that while several important specific characteristics of the short- and long-sarcomere length fibres (ATPase, maximum Ca2+-activated force and fibre stiffness) can be explained solely on differences in the ultrastructure (length and density per cross-sectional area of myosin filaments) there are also differences in the properties of the proteins involved in the force production and regulation evidenced by the differential effect of Sr2+, BDM and ionic strength on contractile activation in the two fibre types.

Notes: Abstract A bioassay was used to evaluate the effects of cuticular leaf components, isolated fromN. tabacum, N. glutinosa (accessions 24 and 24a), and 23other Nicotiana species, on germinationof P. tabacina (blue mold). The leaf surface compounds includedα- andβ-4,8,13,-duvatriene-l,3-diols (DVT-diols), (13-E)-labda-13-ene-8α-,15-diol (labdenediol), (12-Z)-labda-12,14-diene-8α-ol (cis-abienol), (13-R)-labda-8,14-diene-13-ol (manool), 2-hydroxymanool, a mixture of (13-R)-labda-14-ene-8α,13-diol (sclareol), and (13-S)-labda-14-ene-8α,13-diol (episclareol), and various glucose and/or sucrose ester isolates. The above in acetone were applied onto leaf disks of the blue moldsusceptibleN. tabacum cv. TI 1406, which was then inoculated with blue mold sporangia. Estimated IC50 values (inhibitory concentration) were 3.0μg/cm2 forα-DVT-diol, 2.9μ/cm2 forβ-DVT-diol, 0.4μg/cm2 for labdenediol and 4.7μg/cm2 for the sclareol mixture. Manool, 2-hydroxymanool, andcis-abienol at application rates up to 30μg/cm2 had little or no effect on sporangium germination. Glucose and/or sucrose ester isolates from the cuticular leaf extracts of 23Nicotiana species and three different fractions fromN. bigelovii were also evaluated for antimicrobial activity at a concentration of 30μg/cm2. Germination was inhibited by 〉20% when exposed to sugar esters isolated fromN. acuminata, N. benthamiana, N. attenuata, N. clevelandii, andN. miersii, and accessions 10 and 12 ofN. bigelovii. These results imply that a number of compounds may influence resistance to blue mold in tobacco.

Notes: Abstract The first intron of the human Proα1(I) collagen gene contains an orientation-dependent enhancer composed of both positive and negative cis-acting elements involved in the transcriptional regulation of this gene. Deletion of a 360 bp Sau 3A intronic fragment spanning nucleotide + 494 to + 854 (S360) resulted in dramatic down-regulation of pCOL-KT (Thompson et al., J Biol Chem 266: 2549–2556, 1991). Using a DNaseI protection assay, we demonstrate a single footprint located at + 590 to + 615 in the S360 fragment; nuclear extracts prepared from mesenchymal and nonmesenchymal cells exhibited similar binding characteristics. A double stranded oligonucleotide representing a consensus Ap-1 binding sequence competed with S360 for binding. In contrast to what occurred in response to S360 deletion which was always accompanied by reduced expression, the deletion of the Ap-1 binding site (+ 598 to + 604) caused either increased or decreased expression of the reporter gene depending on the target cell. Site-directed mutations in the Ap-1-like cis-element of Proα1(I) were also tested in transient expression assays. Consistent with the paradoxical results of Ap-1 deletion, we observed that the functional consequences of mutations in the Ap-1 site also varied in different cells. In A204 cells, one point mutation, which resulted in the loss of protein binding to S360, led to increased CAT activity while another point mutant, which retained binding of the Ap-1 like trans-acting factor(s), showed decreased CAT expression. The effects of these two mutations in the HFL-1 cells were exactly opposite of what was seen for A204 cells. Based on these observations, we postulate that the Ap-1 site plays a critical role in the transcriptional activity of the human Proα1(I) gene. The implications of an apparently dual mode of regulation through a single cis-regulatory element are discussed. (Mol Cell Biochem 118: 119–129, 1992)