The effects of stress on benthic algal communities

The effects of stress on both microalgal and macroalgal communities are considered. On one hand the contrasting approaches of studies of these two communities reflect intrinsic differences in plant size, longevity and ease of handling. On the other hand they reveal that biological monitoring of the potentially deleterious effects of man's activities has focused largely on freshwater environments in which macroalgae only occasionally dominate. Large conspicuous plants can be readily investigated as individuals, whereas it is virtually impossible to trace effects of stress on an individual cell of a vegetatively-reproducing microalga; a population approach is almost inevitably necessary. However, rapid turnover rates, a spectrum of ecological characteristics distributed between many taxa, and the potential for statistical analysis, have facilitated the use of microalgae in environmental impact studies. Failure to extend such investigations into marine systems rests as much on man's ability to ignore environmental deterioration until it affects his quality of life as on the visual dominance of seaweeds around our coasts. However, large gaps remain in our knowledge of both large and small algae; some reported community changes over time are suspect, and the causes of even blatant changes are not always apparent.

Use of macroinvertebrate communities to detect environmental stress in running waters

This paper presents an account of some current uses of RIVPACS (River Invertebrate Prediction and Classification System), a software package developed by the Institute of Freshwater Ecology (UK). Background information is also given on the unique data-set on which the system is based. Before discussing RIVPACS, we consider the range of environmental stresses encountered in flowing-water systems and some of the ways in which stresses may affect macroinvertebrate communities. The wide application and relevance of the RIVPACS approach was recognised when it was chosen as the biological method for use throughout the UK in the 1990 River Quality Survey (RQS). In the concluding section we list some lessons learnt both from the 1990 survey and from our own testing exercise, and we outline current developments which will lead to a new version of RIVPACS for use in the 1995 RQS.

From the individual to the community and beyond: water quality, stress indicators and key species in coastal waters

This review examines water quality and stress indicators at levels of organisation from the individual to the community and beyond by means of three case studies concentrating on rocky shores within the north-east Atlantic. Responses of dogwhelks (Nucella) to tributyltin pollution from antifouling paints is examined as the main case study. There are effects at the individual level (development of male sexual characteristics in the female leading to effective sterility) and population level (reduction in juveniles, few females and eventual population disappearance of dogwhelks in badly contaminated areas) but information on community level effects of dogwhelk demise is sparse. Such effects were simulated by dogwhelk removal experiments on well studied, moderately exposed ledges on shores on the Isle of Man. The removal of dogwhelks reduced the size and longevity of newly established Fucus clumps that had escaped grazing. Removal of dogwhelks also increased the likelihood of algal escapes. In a factorial experiment dogwhelks were shown to be less important than limpets \{Patella) in structuring communities but still had a significant modifying effect by increasing the probability of algal escapes. Community level responses to stress on rocky shores are then explored by reference to catastrophic impacts such as oil spills, using the Torrey Canyon as a case study. Recovery of the system in response to this major perturbation took between 10-15 years through a series of damped oscillations. The final case study is that of indicators of ecosystem level change in response to climate fluctuations, using ratios of northern \{Semibalanus balanoides) and southern (Chthamalus spp.) barnacles. Indices derived from counts on the shore show good correlations with inshore sea-water temperatures after a 2-year lag phase. The use of barnacles to measure offshore changes is reviewed. The discussion considers the use of bioindicators at various levels of organisation.

Stress, shredders and streams: using gammarus energetics to assess water quality

This paper reviews the effectiveness of Gammarus scope for growth (SfG) as an indicator of water quality. In addition, the link between physiological changes and effects at higher levels of biological organisation is addressed. Exposure to a range of toxicants resulted in decreases in Gammarus SfG which were qualitatively and quantitatively correlated with subsequent reductions in growth and reproduction. Reductions in SfG were due principally to a decrease in energy intake (i.e. feeding rate) rather than an increase in energy expenditure. Gammarus pulex is an important shredder in many stream communities and stressed-induced reductions in its feeding activity were correlated with reductions in the processing of leaf litter by a semi-natural stream community. Hence, changes in the physiological energetics of Gammarus provide a general and sensitive indicator of stress which can be linked to effects at higher levels of biological organisation. Under long-term stress and hence prolonged reductions in SfG, animals may adapt by modifying their life-history strategies and producing fewer, larger offspring.

Effects of stress on the immune system of fish

The effects of stress on the immune system of various fish species including dab Limanda limanda, flounder Platichthys flesus, sea bass Dicentrarchus labrax and gobies Zosterisessor ophiocephalus, were investigated from laboratory and field experiments, using various assays to measure immunocompetence, correlated with histological and ultrastructural observations. Modulation of the immune system was demonstrated at tissue, cellular and biochemical levels following exposure to various stressors. The spleen somatic index was depressed in dab stressed in the laboratory and gobies collected from polluted sites in the Venice Lagoon. Differential blood cell counts consistently showed an increase in phagocytes and decrease in thrombocytes in fish exposed to various stressors. Phagocytic activity from spleen and kidney adherent cells was stimulated in dab stressed by transportation but depressed in fish exposed to chemical pollutants. Respiratory burst activity in phagocytic cells was also stimulated in stressed dab but depressed in sea bass exposed to cadmium. The results are discussed in relation to current concepts on stress in fish and the regulation of the immune system.

Efeitos de diferentes dietas hiperlipídicas na via L-arginina-óxido nítrico e no stress oxidativo em eritrócitos de camundongos C57BL/6

Introdução: o óxido nítrico (NO) é um gás inorgânico com uma meia-vida curta e tem um papel crítico na manutenção da homeostase vascular e fluidez sanguínea. O NO é sintetizado a partir do aminoácido L-arginina por uma família de enzimas NO sintases (NOS). Estudos têm mostrado que eritrócitos expressam NOS endotelial (eNOS) funcional, que serve como uma fonte de NO intraluminal. Além disso, eritrócitos participam da defesa antioxidante removendo os radicais livres e prevenindo o dano oxidativo às membranas biológicas e a destruição do NO. Dietas hiperlípidicas estão associadas a um risco aumentado de doença cardiovacular e síndrome metabólica, mas os exatos mecanismos não estão completamente esclarecidos. O objetivo deste estudo foi investigar os efeitos de diferentes dietas hiperlípidicas na via L-arginina-NO e o estresse oxidativo em eritrócitos de camundongos. Metodologia: camundongos machos C57BL/6 de três meses de idade receberam diferentes dietas por 10 semanas: dieta normolipídica ou dieta hiperlipídica contendo banha de porco (HB), óleo de oliva (HO), óleo de girassol (HG) ou óleo de canola (HC). Foram analisados o transporte de L-arginina mediado pelos transportadores catiônicos y+ e y+L, a atividade da NOS, a expressão da eNOS e da NOS induzível (iNOS), a formação de substâncias reativas ao ácido tiobarbitúrico (TBARS) e a atividade das enzimas antioxidantes catalase (CAT) e superóxido dismutase (SOD). Resultados: o transporte total de L-arginina estava aumentado no grupo HO em comparação aos controles e aos outros grupos com dieta hiperlipídica. Quando o transporte foi fracionado, o sistema y+ estava mais ativado no grupo HO em relação aos controles e outros grupos que receberam dieta hiperlipídica. O transporte de L-arginina via sistema y+L estava maior nos grupos HO, HG e HC comparados aos grupos controle e HB. Adicionalmente, a atividade basal da NOS e a expressão de eNOS estavam aumentadas em eritrócitos independente do tipo de dieta hiperlípidica insaturada. Observou-se uma maior expressão da iNOS no grupo HO comparado ao controle. Em contraste, o grupo HB apresentou uma inibição da via L-arginina-NO. A análise da peroxidação lipídica, através da formação de TBARS, e da atividade da enzima antioxidante CAT não revelou diferenças entre os grupos, ao contrário do grupo HO, que induziu uma ativação de outra enzima antioxidante, a SOD. Conclusões: o presente estudo proporciona a primeira evidência de que os sistemas y+ e y+L regulam o transporte aumentado de L-arginina em eritrócitos de camundongos do grupo HO. Além disso, todas as dietas hiperlipídicas insaturadas induzem um aumento da atividade basal da NOS associada a uma expressão elevada da eNOS. É possível que diferentes mudanças na composição lipídica da membrana plasmática induzidas pelas dietas possam afetar transportadores e enzimas nos eritrócitos. Além disso, a inibição da via L-arginina-NO no grupo HB pode contribuir para o desenvolvimento da aterosclerose, enquanto dietas hiperlipídicas insaturadas podem ter um efeito protetor via aumento da geração de NO.

The promoter of cell growth- and RNA protection-associated SND1 gene is activated by endoplasmic reticulum stress in human hepatoma cells

Background: Staphyloccocal nuclease domain-containing protein 1 (SND1) is involved in the regulation of gene expression and RNA protection. While numerous studies have established that SND1 protein expression is modulated by cellular stresses associated with tumor growth, hypoxia, inflammation, heat- shock and oxidative conditions, little is known about the factors responsible for SND1 expression. Here, we have approached this question by analyzing the transcriptional response of human SND1 gene to pharmacological endoplasmic reticulum (ER) stress in liver cancer cells. Results: We provide first evidence that SND1 promoter activity is increased in human liver cancer cells upon exposure to thapsigargin or tunicamycin or by ectopic expression of ATF6, a crucial transcription factor in the unfolded protein response triggered by ER stress. Deletion analysis of the 5'-flanking region of SND1 promoter identified maximal activation in fragment (-934, +221), which contains most of the predicted ER stress response elements in proximal promoter. Quantitative real- time PCR revealed a near 3 fold increase in SND1 mRNA expression by either of the stress- inducers; whereas SND1 protein was maximally upregulated (3.4-fold) in cells exposed to tunicamycin, a protein glycosylation inhibitor. Conclusion: Promoter activity of the cell growth- and RNA-protection associated SND1 gene is up-regulated by ER stress in human hepatoma cells.

An Embedded Stress Sensor for Concrete SHM Based on Amorphous Ferromagnetic Microwires

A new smart concrete aggregate design as a candidate for applications in structural health monitoring (SHM) of critical elements in civil infrastructure is proposed. The cement-based stress/strain sensor was developed by utilizing the stress/strain sensing properties of a magnetic microwire embedded in cement-based composite (MMCC). This is a contact-less type sensor that measures variations of magnetic properties resulting from stress variations. Sensors made of these materials can be designed to satisfy the specific demand for an economic way to monitor concrete infrastructure health. For this purpose, we embedded a thin magnetic microwire in the core of a cement-based cylinder, which was inserted into the concrete specimen under study as an extra aggregate. The experimental results show that the embedded MMCC sensor is capable of measuring internal compressive stress around the range of 1-30 MPa. Two stress sensing properties of the embedded sensor under uniaxial compression were studied: the peak amplitude and peak position of magnetic switching field. The sensitivity values for the amplitude and position within the measured range were 5 mV/MPa and 2.5 mu s/MPa, respectively.