CELL POPULATION KINETIC PROFILE OF THE MOUSE THYMUS, AND THE CHANGES INDUCED BY PREDNISOLONE

The cell population kinetic parameters of the thymus in BALB/c mice have been estimated using stathmokinetic and [³H]TdR techniques in both control animals and animals treated with prednisolone. FLM data were analysed by computer using the Gilbert program. The study showed that prednisolone had an inhibitory effect mainly in the DNA synthesis phase and in G₁. Stathmokinetic data also showed a decrease in the cell birth rate and an increase in the apparent cell cycle time (or potential doubling time) after treatment. The labelling index, the mitotic index and the growth fraction were also decreased. The study also shows a good agreement between the data obtained by stathmokinetic and [³H]TdR techniques.     

The influence of cell elastic modulus on inertial positions in Poiseuille microflows

Microchannels are used as a transportation highway for suspended cells both in vivo and ex vivo. Lymphatic and cardiovascular systems transfer suspended cells through microchannels within the body, and microfluidic techniques such as lab-on-a-chip devices, flow cytometry, and CAR T-cell therapy utilize microchannels of similar sizes to analyze or separate suspended cells ex vivo. Understanding the forces that cells are subject to while traveling through these channels are important because certain applications exploit these cell properties for cell separation. This study investigated the influence that cytoskeletal impairment has on the inertial positions of circulating cells in laminar pipe flow. Two representative cancer cell lines were treated using cytochalasin D, and their inertial positions were investigated using particle streak imaging and compared between benign and metastatic cell lines. This resulted in a shift in inertial positions between benign and metastatic as well as treated and untreated cells. To determine and quantify the physical changes in the cells that resulted in this migration, staining and nanoindentation techniques were then used to determine the cells’ size, circularity, and elastic modulus. It was found that the cells’ exposure to cytochalasin D resulted in decreased elastic moduli of cells, with benign and metastatic cells showing decreases of 135 ± 91 and 130 ± 60 Pa, respectively, with no change in either size or shape. This caused benign, stiffer cancer cells to be more evenly distributed across the channel width than metastatic, deformable cancer cells; additionally, a decrease in the elastic moduli of both cell lines resulted in increased migration toward the channel center. These results indicate that the elastic modulus may play more of a part in the inertial migration of such cells than previously thought.     

Reducing the Decline in Physical Activity during Pregnancy: A Systematic Review of Behaviour Change Interventions

Purpose

Physical activity (PA) typically declines throughout pregnancy. Low levels of PA are associated with excessive weight gain and subsequently increase risk of pre-eclampsia, gestational diabetes mellitus, hypertension disorders, delivery by caesarean section and stillbirth. Systematic reviews on PA during pregnancy have not explored the efficacy of behaviour change techniques or related theory in altering PA behaviour. This systematic review evaluated the content of PA interventions to reduce the decline of PA in pregnant women with a specific emphasis on the behaviour change techniques employed to elicit this change.

Search and Review Methodology

Literature searches were conducted in eight databases. Strict inclusion and exclusion criteria were employed. Two reviewers independently evaluated each intervention using the behaviour change techniques (BCT) taxonomy to identify the specific behaviour change techniques employed. Two reviewers independently assessed the risk of bias using the guidelines from the Cochrane Collaboration. Overall quality was determined using the GRADE approach.

Findings

A total of 1140 potentially eligible papers were identified from which 14 studies were selected for inclusion. Interventions included counselling (n = 6), structured exercise (n = 6) and education (n = 2). Common behaviour change techniques employed in these studies were goal setting and planning, feedback, repetition and substitution, shaping knowledge and comparison of behaviours. Regular face-to-face meetings were also commonly employed. PA change over time in intervention groups ranged from increases of 28% to decreases of 25%. In 8 out of 10 studies, which provided adequate data, participants in the intervention group were more physically active post intervention than controls.

Conclusions and Implications

Physical activity interventions incorporating behaviour change techniques help reduce the decline in PA throughout pregnancy. Range of behaviour change techniques can be implemented to reduce this decline including goals and planning, shaping knowledge and comparison of outcomes. A lack of high quality interventions hampers conclusions of intervention effectiveness.     

Mercury concentrations in Irish headwater lake catchments

An estimated 215,000 tonnes of mercury (Hg) have been emitted to the atmosphere from anthropogenic sources since the nineteenth century, igniting widespread environmental monitoring owing to its toxicity. The environmental fate of Hg is strongly determined by catchment characteristics, especially soil organic matter. In this study, concentrations and pools of Hg were determined for lakes and soils in upland peat-dominated catchments in Ireland to assess controls of aquatic Hg and soil response to changes in emissions. Headwater lakes in upland coastal regions were surveyed for water chemistry and total Hg (THg) during spring 2008. In addition, a sub-set of lakes (n = 5) were repeatedly sampled during 2009–2011, and their surface soils collected for Hg analysis, including a short (30 cm) peat core to assess temporal Hg fluxes using radiometric ²¹⁰Pb dating. Peat cores indicated a significant decrease in Hg deposition since the 1980s, in broad agreement with other ‘background’ regions. Total Hg was correlated with total organic carbon (TOC) in the survey and intensive study lakes (r = 0.70 and 0.45), indicative of the strong affinity of Hg to organic matter. At the intensive lakes, monomethylmercury (MMHg) made up 3.3 % of mean THg and exhibited a positive correlation with total SO₄ ^2? (r = 0.55). Further, both THg and MMHg were significantly correlated with conductivity (r = 0.48 and 0.54, respectively) potentially owing to marine inputs, and negatively correlated with pH (r = ?0.59 and ?0.56 respectively). Significant differences in THg (and MMHg) were observed between the five lakes, the highest concentrations (4.45 and 0.16 ng L^?1, respectively) tended to be associated with TOC in lakes and occurred at sites in the northwest, characterized by higher levels of soil organic matter (peat) and soil moisture relative to the other sites. In contrast, surface soil pools of THg ranged between 13.6 and 20.8 μg m^?2 across study sites and did not vary significantly, but were typical of global background regions. Nonetheless, the organic rich soils that dominate Ireland are a natural sink for THg, and peat harvesting for energy production may release long-term stores of Hg from deeper soil layers.     

Physiological dynamics,reproduction‐maintenance allocations,and life history evolution

Allocation of resources to competing processes of growth, maintenance, or reproduction is arguably a key process driving the physiology of life history trade‐offs and has been shown to affect immune defenses, the evolution of aging, and the evolutionary ecology of offspring quality. Here, we develop a framework to investigate the evolutionary consequences of physiological dynamics by developing theory linking reproductive cell dynamics and components of fitness associated with costly resource allocation decisions to broader life history consequences. We scale these reproductive cell allocation decisions to population‐level survival and fecundity using a life history approach and explore the effects of investment in reproduction or tissue‐specific repair (somatic or reproductive) on the force of selection, reproductive effort, and resource allocation decisions. At the cellular level, we show that investment in protecting reproductive cells increases fitness when reproductive cell maturation rate is high or reproductive cell death is high. At the population level, life history fitness measures show that cellular protection increases reproductive value by differential investment in somatic or reproductive cells and the optimal allocation of resources to reproduction is moulded by this level of investment. Our model provides a framework to understand the evolutionary consequences of physiological processes underlying trade‐offs and highlights the insights to be gained from considering fitness at multiple levels, from cell dynamics through to population growth.     

α-tocopherol inhibits oxidative stress induced by cholestanetriol and 25-hydroxycholesterol in porcine ovarian granulosa cells

The cytotoxicity of oxysterols including 7-ketocholesterol, -epoxide, cholestanetriol and 25-hydroxycholesterol and the possible protecting effect of -tocopherol on cholestanetriol and 25-hydroxycholesterol-induced cytotoxicity were investigated in primary cultures of porcine ovarian granulosa cells. Cell viability as determined by % trypan blue staining and mitochondrial function as determined using 3-[4,5-dimethylthiazol-2-yl]-2,5- diphenyltetrazolium bromide (MTT) reduction were decreased significantly after 24 h exposure to 2.5 M -epoxide, cholestanetriol and 25-hydroxycholesterol. 7-ketocholesterol (2.5 M) did not affect cell viability or mitochondrial function under the same culture conditions. The specific activities of catalase and superoxide dismutase, two antioxidant defense enzymes were increased significantly (p < 0.01) following 24 h exposure to 2.5 M concentrations of cholestanetriol while only superoxide dismutase was increased in 25-hydroxycholesterol-treated cells (p < 0.001). Specific activity of glutathione peroxidase was unchanged relative to control cells. Levels of thiobarbituric acid reactive substances remained unchanged after exposure to 7-ketocholesterol, -epoxide, cholestanetriol, 25-hydroxycholesterol and cholesterol. Administration of 1 M -tocopherol to the culture medium significantly improved cell viability and restored both superoxide dismutase and catalase activities to control levels in cholestanetriol -treated cells and only superoxide dismutase in 25-hydroxycholesterol-treated cells. These studies suggest that the cytotoxic nature of physiologically relevant concentrations of cholestanetriol and 25-hydroxycholesterol in granulosa cells is in part due to oxidative stress, but it may be reduced in the presence of a-tocopherol.     

Author Index Volume 71 2004

Authors Index

Author Index Volume 71 2004     

Synthesis and X-ray crystal structure of [Ag(phendio)<Subscript>2</Subscript>]ClO<Subscript>4</Subscript> (phendio = 1,10-phenanthroline-5,6-dione) and its effects on fungal and mammalian cells

The Cu(II) and Ag(I) complexes, [Cu(phendio)₃](ClO₄)₂4H₂O and [Ag(phendio)₂]ClO₄ (phendio = 1,10-phenanthroline-5,6-dione), are prepared in good yield by reacting phendio with the appropriate metal perchlorate salt. The X-ray crystal structure of the Ag(I) complex shows it to have a pseudo tetrahedral structure. `Metal-free' phendio and the Cu(II) and Ag(I) phendio complexes strongly inhibit the growth of the fungal pathogen Candida albicans, and are more active than their 1,10-phenanthroline analogues. The simple Ag(I) salts, AgCH<sub>3</sub>CO<sub>2</sub>, AgNO<sub>3</sub> and AgClO<sub>4</sub>.H<sub>2</sub>O display superior anti-fungal properties compared to analogous simple Cu(II) and Mn(II) salts, suggesting that the nature of the metal ion strongly influences activity. Exposing C. albicans to `metal-free' phendio, simple Ag(I) salts and [Ag(phendio)₂]ClO₄ causes extensive, non-specific DNA cleavage. `Metal-free' phendio and [Ag(phendio)₂]ClO₄ induce gross distortions in fungal cell morphology and there is evidence for disruption of cell division. Both drugs also exhibit high anti-cancer activity when tested against cultured mammalian cells.     

Cytotoxicity, genotoxicity and oxidative reactions in cell-culture models: modulatory effects of phytochemicals

Much research effort has focused on the identification of phytochemicals in fruit and vegetables which exert beneficial effects. Our research examines modulatory effects of phytochemicals on cytotoxicity, genotoxicity and oxidative reactions in cell systems. Two examples of our studies are discussed. First, the potential beneficial effects of flavonoids are demonstrated. Flavonoids are reported to exhibit a wide variety of biological effects, including antioxidant and free-radical-scavenging activities. The aim of the study was to determine if flavonoids could protect against H2O2-induced DNA damage, as measured by the comet assay, in Caco-2 and HepG2 cells. Both cell lines were supplemented with increasing concentrations of myricetin, quercetin and rutin for 24 h followed by exposure to H2O2 (50 microM) for 30 min. Exposure to H2O2 for 30 min at 37 degrees C resulted in significant DNA damage and pre-incubation with the flavonoids before H2O2 exposure significantly (P <0.05) protected Caco-2 and HepG2 cells against H2O2-induced DNA damage. Secondly, we illustrate the use of cellular models to study oxysterol-induced toxicity. Oxysterols are generated during the cooking and processing of foods and may be produced endogenously by the oxidation of membrane lipids. Recent findings suggest that oxysterols may modulate cytotoxicity by exerting effects on the induction of apoptosis. 7beta-Hydroxycholesterol (7beta-OHC) and 25-hydroxycholesterol, both of which are commonly found in foods, were investigated for their abilities to induce apoptosis in a human monocytic blood cell line, U937, and in the human hepatoma cell line, HepG2 cells. U937 and HepG2 cells were incubated for up to 48 h with 30 microM oxysterol. 7beta-OHC induced apoptosis in U937 cells as measured by non-random DNA fragmentation, condensed and fragmented nuclei, and the generation of hypodiploid cells. In contrast, oxysterols may induce cell death by a different mechanism in the hepatoma cells, possibly by necrosis.