Vascular smooth muscle cell detachment from elastin and migration through elastic laminae is promoted by chondroitin sulfate-induced “shedding” of the 67-kDa cell surface elastin binding protein

Impaired elastin fiber assembly is observed in the fetal ductus arteriosus (DA), associated with a reduced concentration of elastin binding protein (EBP), a 67-kDa galactolectin. It is also seen in cultured aortic (Ao) smooth muscle cells (SMC) following the release of the EBP by glycosaminoglycans rich in AN-acetylgalactosamine, such as chondroitin sulfate (CS). In the DA, impaired elastin fiber assembly is observed in conjunction with intimal thickening associated with increased migration of SMC into the subendothelium, a feature we previously related to increased production of fibronectin. In this report, we determined whether SMC use the EBP to attach to an elastin substrate, whether shedding of the EBP promotes SMC migration through a threedimensional network of pure elastic laminae prepared from sheep aorta, and whether the latter is associated with increased production of fibronectin. We observed reduced attachment to elastin-coated surfaces of DA SMC deficient in EBP compared to Ao SMC. Addition of CS but not heparan sulfate (a glycosaminoglycan which does not induce EBP shedding) decreased Ao SMC attachment to elastin, as did preincubation with VGVAPG elastin-derived peptides which saturate the EBP. The immunolocalization of cell surface EBP suggested that cells can quickly replace EBP released from their surfaces by CS treatment. The magnitude of CS-induced impaired attachment of SMC to elastin was dose dependent and could be further increased by the administration of cyclohexamide and sodium azide. Also, the reversibility of CS-induced detachment was prevented by monensin. This suggests that a process of new synthesis and intracellular transport of the EBP was necessary to replace the EBP molecules released from the cell surface by CS treatment. In the migration assay, both DA and Ao SMC attached to the top of an elastin membrane, but only DA SMC deficient in EBP migrated through the laminae. Addition of CS, which induced shedding of EBP, resulted in Ao SMC migration associated with increased synthesis of fibronectin. We postulate that CS-induced release of EBP from SMC surfaces causes cell detachment from elastin and an increase in fibronectin synthesis, processes which may be critical in promoting SMC migration associated with intimal thickening developmentally in the DA and perhaps also in vascular disease.     

A review of the bioavailability of petroleum constituents

Exposure to petroleum constituents at contaminated sites may occur through a variety of pathways, including inhalation of vapors and particulates, ingestion of water and soils, and dermal contact with water and soils. Accurately assessing the human health risks from such exposures requires information on the medium‐ and route‐specific bioavailability of petroleum constituents (e.g., how well these chemicals enter the body via the gastrointestinal tract and skin). For example, when the medium or exposure route in an animal toxicity assay (e.g., ingestion of water) differs from the actual route of human exposure at the petroleum contaminated site (e.g., dermal contact with soil), adjustments should be made that reflect the relative bioavailability of the chemical in the different media. The focus of this article is on (1) the availability of oral and dermal absorption data for one PAH (benzo[a]pyrene, (B[a]P) and three VOCs in soil (benzene, toluene, and xylene); (2) factors affecting the uptake of these PAHs and VOCs from soil; and (3) ways to incorporate bioavailability data into human health risk assessments. Based on our review, we recommend the following default values for the oral and dermal absorption of B[a]P, benzene, toluene, and xylene from soil:

A review of the bioavailability of petroleum constituents

All authors

Jennifer Bramard & Barbara D. Beck

https://doi.org/10.1080/15320389209383417

Published online:

02 December 2008

Display Table

Site‐specific information such as chemical concentrations in soil, soil characteristics, soil loadings on the skin, contact site, and contact time could result in modifications of these numbers. As shown, our default absorption values are generally less than those recommended by the U.S. EPA (1991a,b,c). The implications of these estimates of bioavailability for risk assessment and for the selection of soil cleanup levels at petroleum‐contaminated sites are discussed.     

Two approaches to obtaining low,extracellular deoxyribonuclease activity in cultures of heterocyst-forming cyanobacteria

Six out of 158 axenic strains of heterocyst-forming cyanobacteria consistently failed to produce circles of clearing in agar medium containing DNA-methyl green. When tested with [³H]DNA and coliphage DNA, supernatant fluids from cultures of two of these strains [University of Texas Culture Collection (UTEX) strain 2014 and 19-6C-C] showed no detectable deoxyribonuclease activity, and such fluids from another two of the six, and four others, showed low but detectable deoxyribonuclease activity. Covalently closed circular (plasmid) DNA was not detectably degraded by supernatant fluids from UTEX 2014 and 19-6C-C and from four of the other strains. When DNA was incubated with whole cells of certain strains, a sereis of fragments of discrete size was produced, perhaps by cell-bound, periplasmic, restriction endonucleases. Inclusion of one-tenth strength saline sodium citrate (SSC) in an eight-fold dilution of the medium of Allen and Arnon had little effect on growth of Anabaena variabilis American Type Culture Collection (ATCC) strain 29413 yet prevented all but slight degradation of plasmid pBR322 or of DNA.     

Analysis of development and growth in a mutant of Physarum polycephalum with defective cytokinesis

Cultures of amoebae of the mutant strain ATS23 isolated from strain CLd of Physarum polycephalum contain multinucleate cells and cells with increased nuclear DNA content. Plasmodia derived from ATS23 clones show abnormal morphology and defective sporulation. All abnormalities are enhanced by high incubation temperature (31 °C). Genetic analysis suggested that all the abnormalities were caused by a single mutation, denoted hts-23. The kinetics of plasmodium formation were followed in cultures of apogamic amoebae carrying hts-23 and hts⁺ (wild type) respectively. Results indicated that, relative to wild type, hts-23 did not increase the rate of plasmodium formation. There was evidence that, in both mutant and wild-type strains, commitment to plasmodium development occurred in uninucleate cells. Analysis of cell pedigrees by time-lapse cinematography indicated that the primary abnormal event in cultures of hts-23 amoebae was failure of cytokinesis; an apparently complete cleavage furrow was formed but cell separation failed, resulting in a binucleate cell. This event occurred randomly in pedigrees in which the majority of divisions were completed normally; its frequency increased during incubation at 31 °C. All other abnormalities in hts-23 amoebal cultures could be attributed to this primary event, assuming that DNA synthesis continued in the absence of cytokinesis and that the binucleate cells underwent the amoebal type of “open” mitosis, allowing the possibility of spindle fusion. This implies that the acquisition of “closed” mitosis is an essential early step in plasmodium development.     

A yellow polysaccharide-producing bacterium with unusual characteristics

Summary A polysaccharide-producing Gram-negative bacterium was isolated from a sample of hay. It grew best on nitrate-containing media with sucrose as carbon source; the colony form was highly unusual. No polysaccharide was formed on glucose. A spontaneous mutant producing the same polysaccharide on both sucrose- and glucose-containing media was isolated. The polysaccharide has been characterized as an acid heteropolymer containing D-galacturonic acid, D-glucose, D-galactose and D-mannose in the approximate molar ratio 1:1:3:1, together with about 2 mol of acetate. The polysaccharide in aqueous solution was highly viscous with pseudoplastic characteristics.     

Silver staining of the lampbrush chromosomes ofTriturus cristatus carnifex

Lampbrush chromosomes fromTriturus cristatus carnifex were stained using the ammoniacal silver staining (AgAS) technique. Many of the recognized marker structures proved to be silver positive, plus between six and fifteen lateral loop pairs. None of the stained loop pairs corresponded to known sites of the nucleolus organizers, although the extrachromosomal nucleoli were silver positive. The ammoniacal silver staining technique does not demonstrate the specificity for active ribosomal cistrons in lampbrush chromosomes that it does in a wide variety of mammalian mitotic chromosomes.     

The response of development rate to temperature in the univoltine cranefly,Tipula subnodicornis Zetterstedt

Summary The cranefly, Tipula subnodicornis, emerges as an adult in the spring and has an annual life-cycle in the British Isles. This is maintained partly through the presence of a winter diapause but the response of development rate to temperature also acts to preserve the timing of the cycle. During development under constant temperature conditions in the laboratory the optimum temperature (taken as the temperature which promoted the most rapid development) dropped from 25°C, or above, in the egg stage to below 20°C in the late larval stages. It is suggested that at the warmer, southern limits of the geographical range rapid early development may be compensated by a retardation in late larval growth. In addition, the response of growth rate to change in temperature was small in the fourth, final, instar and resulted in low Q ₁₀ values; 2.4 between 7° and 10°C, 1.5 between 10° and 15°C and 0.9 between 15° and 20°C. As the fourth instar comprises the greater part of the growth period, this has the effect of minimising the effect of temperature differences which are the result of differences of latitude or altitude. Even at optimum temperatures the growth period was prolonged and larvae in the field do not reach maximum weight, and the photosensitive stage, until late autum when short daylength promotes diapause. Subsequent development in the spring, before pupation and during the pupal period, showed a reversion to the higher Q ₁₀ figures of the early stages in development.The development of final instar Tipula subnodicornis larvae is contrasted with that of Tipula melanoceros. Tipula melanoceros emerges as an adult in September and it is likely that it has an egg diapause. Consequently larval development is confined to a short period between April and late July and growth must be rapid during this period. Under constant temperature conditions in the laboratory the growth of final instar larvae showed a marked contrast to that of Tipula subnodicornis in that the response to temperature was large and remained positive over a wider temperature range.     

Effects of pair migratory behavior on breeding phenology and success in a partially migratory shorebird population

In migratory systems, variation in individual phenology can arise through differences in individual migratory behaviors, and this may be particularly apparent in partial migrant systems, where migrant and resident individuals are present within the same population. Links between breeding phenology and migratory behavior or success are generally investigated at the individual level. However, for breeding phenology in particular, the migratory behaviors of each member of the pair may need to be considered simultaneously, as breeding phenology will likely be constrained by timing of the pair member that arrives last, and carryover effects on breeding success may vary depending on whether pair members share the same migratory behavior or not. We used tracking of marked individuals and monitoring of breeding success from a partially migrant population of Eurasian oystercatchers (Haematopus ostralegus) breeding in Iceland to test whether (a) breeding phenology varied with pair migratory behavior; (b) within‐pair consistency in timing of laying differed among pair migratory behaviors; and (c) reproductive performance varied with pair migratory behavior, timing of laying, and year. We found that annual variation in timing of laying differed among pair migratory behaviors, with resident pairs being more consistent than migrant and mixed pairs, and migrant/mixed pairs breeding earlier than residents in most years but later in one (unusually cold) year. Pairs that laid early were more likely to replace their clutch after nest loss, had higher productivity and higher fledging success, independent of pair migratory behavior. Our study suggests that the links between individual migratory behavior and reproductive success can vary over time and, to a much lesser extent, with mate migratory behavior and can be mediated by differences in laying dates. Understanding these cascading effects of pair phenology on breeding success is likely to be key to predicting the impact of changing environmental conditions on migratory species.