How does the extracellular matrix direct gene expression?

Based on the existing literature, a model is presented that postulates a “dynamic reciprocity” between the extracellular matrix (ECM) on the one hand and the cytoskeleton and the nuclear matrix on the other hand. The ECM is postulated to exert physical and chemical influences on the geometry and the biochemistry of the cell via transmembrane receptors so as to alter the pattern of gene expression by changing the association of the cytoskeleton with the mRNA and the interaction of the chromatin with the nuclear matrix. This, in turn, would affect the ECM, which would affect the cell, which…     

The effect of needle age on the acceptability of Sitka spruce needles to the aphid,Elatobium abietinum (Walker)

Summary A comparison of the feeding behaviour of E. abietinum on current year needles and previous year needles of P. sitchensis revealed that during the summer months the aphids preferentially settled on previous year needles, this response not being evident in winter. Aphids on current year needles in summer took a much longer period of time to commence sap uptake than in winter, intake ceasing following a very short feeding period. On previous year needles sap uptake in December commenced after a shorter feeding period than in June. Analysis of total and soluble nitrogen levels in Sitka spruce needles showed that current year needles had initially higher levels during shoot elongation in May and early June, but that previous year needles had higher levels for most of the remainder of the year. Quantitative analyses of amino acids revealed that in current year needles the levels were generally lower than in previous year needles. Less marked proportional differences were observed between previous year needles in May and in July/August when the needles were unsuitable. Addition of amino acids in solution into cut current year shoots resulted in increased longevity on shoots containing introduced iso-leucine, histidine and methionine and revealed a general imbalance of the amino acids.     

Movement of tropomyosin during regulation of vertebrate skeletal muscle: a simple physical model.

Using data obtained from (a) X-ray diffraction patterns of vertebrate skeletal muscle (b) three dimensional reconstructions from electron micrographs of in vitro aggregates of the thin filament proteins in the switched “on” and “off” positions (c) the analysis of the sequence of tropomyosin, a simple model can be proposed which may explain the geometrical arrangement of actin, tropomyosin and troponin during regulation. The “cooperative” behaviour exhibited by the thin filament can also be explained in terms of this arrangement.