Extracellular matrix components influence the survival of adult cardiac myocytes in vitro

Calcium-tolerant myocytes were isolated from adult rat hearts by collagenase perfusion and plated on various substrates in serum-free medium and their adhesion to various extracellular matrix (ECM) components was determined. The myocytes attached readily to dishes coated with collagen type IV (C-IV), laminin (LN), and to fetal bovine serum (FBS) in a manner dependent on the concentration of the components. Substantially fewer myocytes adhered to dishes coated with fibronectin (FN) or to uncoated plastic dishes. Cells adhered equally well to dishes coated with C-IV, LN and FBS within 1-4 h. However, when examined after 2 weeks in culture it was found that only C-IV and LN could support survival of the attached myocytes, and when cultured on C-IV or LN the myocytes were spread and had formed a dense monolayer. The actin filaments had at this time reorganized linearly along the long axis of the cell and the myocytes contracted spontaneously. Rabbit antibodies were raised against myocyte membranes and their ability to inhibit attachment to ECM components was studied. Purified IgG inhibited attachment to C-IV, while having only a minor effect on attachment to LN. These data are compatible with the presence of a specific cell surface component(s) that interacts with ECM substrates and influences cell shape and possibly thereby influences cellular functions.     

Relationships of the Col plasmids E2, E3, E4, E5, E6, and E7: Restriction mapping and colicin gene fusions

Thirteen ColE plasmids representing the E2-E7 types have been compared by restriction mapping. Over 80% of their restriction sites were found to be similarly positioned, indicating that these plasmids share a common structure. Three variants are ColE2-CA42 and ColE7-K317, both of which contain 1.8-kb DNA segments in place of a 2.5-kb segment common to the other plasmids, and ColE6-CT14, which has an additional 5.0-kb DNA segment compared to the other plasmids. The colicin (col), immunity (imm), and colicin release (hic) genes of these plasmids have been localized to regions corresponding to those known for ColE3-CA38 and ColE2-P9, with the imm and hic genes adjacent to the 3' end of the col gene. Active colicin is produced from hybrid col genes containing 5' and 3' ends from different E-type plasmids. The 3'-termini of the fused col genes specify the colicin type.     

Inhibition of soybean lipoxygenase by SKF 525-A and metyrapone

To determine whether agents which inhibit cytochrome P-450 enzymes also inhibit lipoxygenase, the effects of metyrapone and SKF 525-A were assessed on soybean lipoxygenase using a spectrophotometric technique which allows for measurement of both the rate and magnitude of product formation. Both SKF 525-A and metyrapone inhibited the rate of product formation and the final amount of product formed in 5 min incubations SKF 525-A was 5 to 6 times more potent than metyrapone, with the IC₅₀ for SKF 525-A 40 uM and for metyrapone between 150 and 200 uM as determined by the total product formation in 5 minutes. Analysis of the reduced product by HPLC confirmed that the substances monitored were those generated by the 15-lipoxygenase enzyme.     

Absence of genotoxic effects of nonasbestos mineral fibers

The biological activity of natural and synthetic mineral fibers has been examined. Natural attapulgite [(Mg, Al)₂Si₄O₁₀(OH).4H₂0], synthetic xonotlite [Ca₃Si₃O₈(OH)₂] and natural sepiolite [Mg₂Si₃O₈.2H₂O] were selected. Genotoxic effects were investigated by means of a well established cellular model based upon the measurement of unscheduled DNA synthesis (UDS) in rat hepatocytes in primary culture. The intrinsic capacity of the fibers (1 and 10 µ/ml) to induce UDS was first tested. None of the fiber types showed detectable UDS-eliciting activity. Also, the possible modulation of the cellular response to genotoxic agents by the materials was examined by exposing the cells to mixtures of 2-acetylaminofluorene (AAF) (0.05 and 0.25 µg/ml) and fibers (1 and 10 µg/ml). In these experiments, the UDS response was significantly diminished in the presence of xonotlite. This phenomenon may reflect changes in the uptake and/or metabolism of AAF or may result from an inhibition of DNA repair processes, the latter suggesting a possible cocarcinogenic potential for this synthetic silicate. These results point to the immediate necessity of studying more extensively the biological effects of fibrous materials that can be used as substitutes for asbestos.Abbreviations AAF 2-acetylaminofluorene - DMSO dimethyl-sulfoxide - FBS fetal bovine serum - IRDA Institut de Recherche et de Développement sur l'Amiante - LDH lactate dehydrogenase - UDS unscheduled - DNA synthesis - WME Williams' Medium E This work was supported by the Institut de Recherche et de Développement sur l'Amiante (IRDA), Sherbrooke, Canada.     

Double blind comparative study of omeprazole 10 mg and 30 mg daily for healing duodenal ulcers.

Healing of duodenal ulcers was assessed in 66 patients who received omeprazole either 10 mg or 30 mg daily for four weeks in a double blind study. Healing was rapid in both groups. At two weeks the ulcers in 15 of the 30 patients taking 10 mg daily had healed compared with 28 of the 36 (78%) taking 30 mg daily (p less than 0.03). At four weeks the respective proportions had risen to 83% (25/30) and 94% (33/35) (p greater than 0.05). In non-smokers the proportion of ulcers healed did not differ significantly with the two doses, although there was a trend for less healing at two weeks with 10 mg daily; in smokers significantly fewer ulcers (p less than 0.05) were healed with 10 mg than 30 mg daily at two weeks (7/16 (44%) v 17/21 (81%] and at four weeks (12/16 (75%) v all 21 (100%]. Adverse reactions were few and transient and were considered unlikely to be due to omeprazole.     

Binding of 5-methoxypsoralen to human serum low density lipoproteins

5-methoxypsoralen (5-MOP) binds to human serum low density lipoproteins (LDL) according to a two-step process. Scatchard analysis of the first step yields K = 1.4 × 10⁵ M^?1 and 4 binding sites. It involves the LDL apoprotein. The second step corresponds to a solubilization, in the lipidic core, of ? 45 molecules of 5MOP per LDL molecule. It is accompanied by a large blue shift of the 5MOP fluorescence. The ability of LDL to bind 5MOP and to carry it into various cells may explain some biological effects sometimes encountered during PUVA therapy.     

Light-induced variation in the growth and dynamics of transplanted ramets of the understory herb,Aster acuminatus

Summary Ramets of the understory herb, Aster acuminatus, were transplanted from two source populations into eight understory garden sites that varied in light and soil moisture levels. Ramet growth, clonal growth, flowering and survivorship were monitored for three growing seasons. Large differences among gardens in ramet growth, clonal growth and flowering developed in the first growing season and increased in the next two years. This variation was positively correlated with garden light level but not at all with soil moisture. Mortality rates were low in all gardens and showed that genets from any particular source could survive over a broad range of environmental conditions. There was no conclusive evidence for any source population differences in the capacity to survive or grow in different environments. The rapid, light-induced responses of transplanted ramets resulted in garden populations very similar in appearance to natural populations experiencing similar light regimes. These results combined with those from other studies of A. acuminatus provide strong evidence for the importance of light in explaining population patterns and dynamics in this species.