Decreased incidence of mycorrhizal root tips associated with soil heavy-metal enrichment

Mycorrhizal incidence was studied at two forested locations in south-central Virgina. At each location, one site with soil naturally enriched in copper, lead and zinc was designated as mineralized, and an adjacent site, with significantly lower levels of these metals, was used as a control. A total of 223 soil samples were collected during the summer of 1984 and assayed for active mycorrhizal tips. A reduced active mycorrhizal root tip count was found in those samples collected from the mineralized sites at both locations (P≤0.001).     

Larval mortality and the composition of coral reef fish communities

Research over the past decade shows that fish populations on coral reefs can vary enormously, both spatially and temporally. Nonetheless, predictable patterns in structure are present at both small and regional scales. These have usually been interpreted as resulting from processes acting after settlement of fishes from the plankton. However, current research now suggests that planktonic processes could also result in deterministic patterns of community structure.     

Use of p-aminobenzamidine to monitor activation of trypsin-like serine proteases

The fluorescent compound p-aminobenzamidine was used to monitor activation of the trypsin-like serine proteases trypsin, thrombin, and blood coagulation factors IXa and Xa. p-Aminobenzamidine, when bound to the activated forms of these proteases but not the corresponding zymogens, displayed an increase in fluorescence. This fluorescence increase was coincident with activation as measured by synthetic substrate hydrolysis, physiological coagulation activity, and the appearance of activation products on gel electrophoresis. The activation of proteolytically modified factor X was also monitored. These results suggest that following p-aminobenzamidine fluorescence is a convenient procedure for monitoring activation of trypsin-like serine proteases.     

Sulfated glycolipids and cell adhesion

The adhesive glycoproteins laminin, thrombospondin, and von Willebrand factor bind specifically and with high affinity to sulfatides, and it is this binding that probably accounts for their ability to agglutinate glutaraldehyde-fixed erythrocytes. The three proteins differ, however, in the inhibition of their binding to sulfatides by sulfated polysaccharides. Fucoidan strongly inhibits binding of both laminin and thrombospondin, but not of von Willebrand factor, suggesting the involvement of laminin or thrombospondin, or other unknown sulfatide-binding proteins in specific cell interactions that are also inhibited by fucoidan. Thrombospondin adsorbed on plastic promotes the attachment and spreading of some melanoma cells. Interestingly, fucoidan and an antibody against the sulfatide-binding domain of thrombospondin selectively inhibit spreading but not attachment to thrombospondin-coated surfaces. Sulfatides, but not neutral glycolipids or gangliosides, when adsorbed on plastic also promote attachment and spreading of some cultured cell lines. Direct adhesion of melanoma cells requires high densities of adsorbed sulfatide. In the presence of laminin, however, specific adhesion of some cell types to sulfatide is strongly stimulated and requires only low densities of adsorbed lipid, suggesting that laminin is mediating adhesion by crosslinking receptors on the cell surface to sulfatide adsorbed on the plastic. Although thrombospondin also binds to sulfatides and to melanoma cells, it does not enhance but rather inhibits direct and laminin-dependent melanoma cell adhesion to sulfatide, presumably because it is unable to bind simultaneously to ligands on opposing surfaces. Thus, sulfated glycolipids can participate in both laminin- and thrombospondin-mediated cell adhesion, but their mechanisms of interaction are different.     

Characterization of Haemophilus parainfluenzae strains with low-Mr or ladder-like lipopolysaccharides

Twenty-five Haemophilus parainfluenzae strains were characterized for lipopolysaccharide (LPS) profiles, outer membrane protein profiles, serum sensitivity, plasmid profiles and DNA homology. Seventeen strains produced low-Mr LPS that did not contain O-sidechains, while the remaining eight strains contained ladder-like LPS suggestive of O-repeated units. This is the first time in the genus Haemophilus that LPS with O-repeated groups has been described. The strains producing the different types of LPS could not be distinguished from each other in outer membrane protein profiles or the other characteristics examined.     

Transforming growth factor beta is an important immunomodulatory protein for human B lymphocytes

The growth and differentiation of B cells to immunoglobulin (Ig)-secreting cells is regulated by a variety of soluble factors. This study presents data that support a role for transforming growth factor (TGF)-beta in this regulatory process. B lymphocytes were shown to have high-affinity receptors for TGF-beta that were increased fivefold to sixfold after in vitro activation. The addition of picogram quantities of TGF-beta to B cell cultures suppressed factor-dependent, interleukin 2 (IL 2) B cell proliferation and markedly suppressed factor-dependent (IL 2 or B cell differentiation factor) B cell Ig secretion. In contrast, the constitutive IgG production by an Epstein Barr virus-transformed B cell line was not modified by the presence of TGF-beta in culture. This cell line was found to lack high-affinity TGF-beta receptors. The degree of inhibition of B cell proliferation observed in in vitro cultures was found to be dependent not only on the concentration of TGF-beta added but also on the concentration of the growth stimulatory substance (IL 2) present. By increasing the IL 2 concentrations in culture, the inhibition of proliferation induced by TGF-beta could be partially overcome. In contrast, the inhibition of Ig secretion induced by TGF-beta could not be overcome by a higher concentration of stimulatory factor, demonstrating that the suppression of B cell differentiation by TGF-beta is not due solely to its effects on proliferation. Furthermore, it was demonstrated that B lymphocytes secrete TGF-beta. Unactivated tonsillar B cells had detectable amounts of TGF-beta mRNA on Northern blot analysis, and B cell activation with Staphylococcus aureus Cowan (SAC) resulted in a twofold to threefold increase in TGF-beta mRNA. Supernatants conditioned by unactivated B cells had small amounts of TGF-beta, SAC activation of the B cells resulted in a sixfold to sevenfold increase in the amount of TGF-beta present in the supernatants. Thus, B lymphocytes synthesize and secrete TGF-beta and express receptors for TGF-beta. The addition of exogenous TGF-beta to cultures of stimulated B cells inhibits subsequent proliferation and Ig secretion. TGF-beta may function as an autocrine growth inhibitor that limits B lymphocyte proliferation and ultimate differentiation.     

Growth hormone regulates the abundance of insulin-like growth factor I RNA in adult rat liver

Insulin-like growth factor I (IGF-I) is a mitogenic polypeptide present in the plasma of man and rat that is thought to mediate the actions of pituitary growth hormone on cartilage to promote skeletal elongation. In the rat, plasma levels of IGF-I show both developmental and hormonal regulation: levels are low at birth, increase with age, and are decreased in growth hormone-deficient adult animals. The present study demonstrates that these changes in plasma IGF-I reflect the abundance of IGF-I RNA in rat liver. A human IGF-I cDNA probe hybridized to multiple RNA species in adult rat liver with sizes 8.6, 4.6, 3.2, 2.1, and 1.0-1.4 kilobases. These RNA species were decreased by greater than 80% in neonatal (2- and 12-day-old) rat liver and by greater than 90% in liver from adult rats made growth hormone-deficient by hypophysectomy. Treatment of hypophysectomized rats with growth hormone increased the abundance of all species of IGF-I RNA. These results suggest that growth hormone regulates the expression of its physiological mediator by altering the synthesis, stability, or both of IGF-I RNA in rat liver.     

Effect of chlorine dioxide on selected membrane functions of Escherichia coli

The mode of action of chlorine dioxide on Escherichia coli was assessed by studying outer membrane permeability to macromolecules and potassium, and observing effects on respiration. The results indicate that gross cellular damage involving significant leakage of intracellular macromolecules does not occur. There was a substantial efflux of potassium, however, and respiration was inhibited even at sublethal doses. It was concluded that the inhibition of respiration, which could be due to the damage to the cell envelope, was not the primary lethal event. Observations of the efflux of K⁺ strongly implicate the loss of permeability control as the primary lethal event at the physiological level, with nonspecific oxidative damage to the outer membrane leading to the destruction of the trans-membrane ionic gradient.     

Inheritance of a vestigial wing mutation in the alfalfa weevil, Hypera postica

Alfalfa weevils (Hypera postica (Gyllenhal)) with vestigial hind wings were discovered in a population from Wageningen, the Netherlands, and two populations from the United States—an eastern weevil strain from Beltsville, Maryland and an Egyptian weevil strain from Atascadero, California. Such a mutant was absent from 23 other populations surveyed in the United States—three from eastern, seven from western, and 13 from Egyptian weevil strains. This mutation is due to a dominant autosomal gene with normal-wing individuals as recessive. The mutant gene can be transferred from eastern weevil to the western weevil strain. The short-wing trait may be useful for genetic manipulation to control the alfalfa weevil.

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Résumé Des H. postica aux ailes postérieures vestigiales ont été découverts dans une population de Wageningen (Pays Bas) et deux des USA—une lignée orientale de Beltsville (Maryland) et une lignée de H. brunneipennis d'Atascadero (Californie). Ce mutant était absent de 23 autres populations examinées aux USA: 3 de l'est, 7 de l'ouest et 13 de H. brunneipennis. Cette mutation est due à un gène dominant antosomal avec aile normale comme récessif. Le gêne mutant peut être transféré des lignées orientales aux lignées occidentales. Le caractère aile courte peut être pratique pour les manipulations génétiques destinées à maîtriser les populations d'H. postica.

     

Corticotropin-releasing factor (CRF) stimulates locomotor activity in intact and hypophysectomized newts (Amphibia)

Locomotor activity of rough-skinned newts (Taricha granulosa) was significantly higher in intact and hypophysectomized males injected intracranially with 100 ng CRF (ovine corticotropin-releasing factor) than in those injected with 10 ng CRF or saline. In addition, an injection of corticosterone or dexamethasone failed to stimulate newt locomotor activity. These results provide evidence that CRF can act independently of pituitary hormones to stimulate locomotor activity in a nonmammalian vertebrate.