Thrombin-induced proliferation and expression of platelet-derived growth factor-A chain gene in human vascular smooth muscle cells.

Treatment of human vascular smooth muscle cells (SMC) with human alpha-thrombin greatly increased DNA synthesis and cell proliferation. Both the integrity of the catalytic site and that of the anion binding exosite were required for expression of this activity. Experiments employing Northerns indicated induction of c-fos expression as well as a time-dependent induction of platelet-derived growth factor-A (PDGF-A) gene by thrombin. The thrombin mitogenic activity was potentiated by PDGF-BB, insulin and the vasoconstrictor peptide endothelin-1 suggesting synergism by convergence of intracellular growth-promoting signals. SMC treatment with pertussis toxin and forskolin indicated that the mitogenic activity of thrombin may be induced via signal transduction mechanism(s) involving changes in cAMP levels and activation of a Gi-like protein. These results suggest that thrombin may play a functional role in the regulation of human vascular SMC proliferation.     

Factors affecting low temperature survival ofCinara pilicornis eggs on Sitka spruce

OviparousC. pilicornis deposited eggs in October and early November, the dry weight, but not the fresh weight, decreasing during winter. Diapause terminated in early March, eggs hatched in early May. Mean egg supercooling points varied during the winter, the variation being related to the temperature in the period preceding sample collection. Both glycerol and mannitol were isolated from the eggs. Mannitol levels decreased to zero by mid-winter, levels increasing after diapause termination. Glycerol levels increased up to diapause termination and thereafter decreased, none being present just prior to egg hatch. Neither glycerol nor mannitol were related to supercoolingability, the variation being related to low temperatures which possibly induced changes in the levels of an unknown factor.     

Microvascular free-tissue transfer in children

We have reviewed our experience with 22 microvascular free-tissue transfers in children. Ages range from 2 to 14 years; the success rate was 96 percent. Two patients underwent reexploration for postoperative hemorrhage, possibly due to treatment with low-molecular-weight dextran. No vessel spasm was observed, compared with a 28 percent incidence in our adult series of 154 patients. The vessels were in pristine condition. Operative time was shorter (6.1 hours) than in our adult series (9.7 hours). Average hospital stay was 10 days (compared to 23 days for adults). All children have resumed almost normal activity within 2 months (4 months for adults). Results of this study indicate that microvascular free-tissue transfer can be accomplished safely and expeditiously in children. Care should be taken in preoperative and postoperative planning, however, especially concerning immobilization.     

The observation of mitotic division aberrations in mammalian cells exposed to chemical and radiation treatments

The fidelity of chromosome segregation and the maintenance of the integrity of the chromosome karyotype of eukaryotiic cells is dependent upon the synthesis and functioning of division-related structures such as the nuclear spindle and events such as the attachment of chromosomes to the spindle and their subsequent movement to the poles of the dividing cell. Chemical and physical treatment which modify the synthesis and functioning of division-related events may potentially lead to the production of cells with abnormal chromosome numbers (of both whole chromosome sets and of individual chromosomes).

The ability of environmental agents to modify division-related structures in mammalian cells has been assessed by morphological examination of exposed mitotically dividing cells using staining techniques which identify spindle and chromosome structure and by the analysis of the characteristics of microtubule polymerisation in vitro. Such techniques have been used to identify the spindle-modifying effects of chemicals such as the synthetic hormone diethylstilboestrol and modifications of chromosome to spindle attachment in cells exposed to both UV- and X-irradiation. Such modifications of cell-division-related activities may lead to alterations in the fidelity of division events leading to the production of chromosomally abnormal daughter cells with aneuploid or polyploid karyotypes.