Characterization of Lysophospholipase D Activity in Mammalian Cell Membranes.

Lysophosphatidic acid (LPA) is a lipid mediator that binds to G-protein-coupled receptors, eliciting a wide variety of responses in mammalian cells. Lyso-phospholipids generated via phospholipase A2 (PLA2) can be converted to LPA by a lysophospholipase D (lyso-PLD). Secreted lyso-PLDs have been studied in more detail than membrane-localized lyso-PLDs. This study utilized in vitro enzyme assays with fluorescent substrates to examine LPA generation in membranes from multiple mammalian cell lines (PC12, rat pheochromocytoma; A7r5, rat vascular smooth muscle; Rat-1, rat fibroblast; PC-3, human prostate carcinoma; and SKOV-3 and OVCAR-3, human ovarian carcinoma). The results show that membranes contain a lyso-PLD activity that generates LPA from a fluorescent alkyl-lyso-phosphatidylcholine, as well as from naturally occurring acyl-linked lysophospholipids. Membrane lyso-PLD and PLD activities were distinguished by multiple criteria, including lack of effect of PLD2 over-expression on lyso-PLD activity and differential sensitivities to vanadate (PLD inhibitor) and iodate (lyso-PLD inhibitor). Based on several lines of evidence, including siRNA knockdown, membrane lyso-PLD is distinct from autotaxin, a secreted lyso-PLD. PC-3 cells express GDE4 and GDE7, recently described lyso-PLDs that localize to membranes. These findings demonstrate that membrane-associated lyso-D activity, expressed by multiple mammalian cell lines, can contribute to LPA production.

The hydrodynamics and kinematics of the appendicularian tail underpin peristaltic pumping.

Planktonic organisms feed while suspended in water using various hydrodynamic pumping strategies. Appendicularians are a unique group of plankton that use their tail to pump water over mucous mesh filters to concentrate food particles. As ubiquitous and often abundant members of planktonic ecosystems, they play a major role in oceanic food webs. Yet, we lack a complete understanding of the fluid flow that underpins their filtration. Using high-speed, high-resolution video and micro particle image velocimetry, we describe the kinematics and hydrodynamics of the tail in Oikopleura dioica in filtering and free-swimming postures. We show that sinusoidal waves of the tail generate peristaltic pumping within the tail chamber with fluid moving parallel to the tail when filtering. We find that the tail contacts attachment points along the tail chamber during each beat cycle, serving to seal the tail chamber and drive pumping. When we tested how the pump performs across environmentally relevant temperatures, we found that the amplitude of the tail was invariant but tail beat frequency increased threefold across three temperature treatments (5°C, 15°C and 25°C). Investigation into this unique pumping mechanism gives insight into the ecological success of appendicularians and provides inspiration for novel pump designs.

Sampling multiple life stages significantly increases estimates of marine biodiversity.

Biodiversity assessments are critical for setting conservation priorities, understanding ecosystem function and establishing a baseline to monitor change. Surveys of marine biodiversity that rely almost entirely on sampling adult organisms underestimate diversity because they tend to be limited to habitat types and individuals that can be easily surveyed. Many marine animals have planktonic larvae that can be sampled from the water column at shallow depths. This life stage often is overlooked in surveys but can be used to relatively rapidly document diversity, especially for the many species that are rare or live cryptically as adults. Using DNA barcode data from samples of nemertean worms collected in three biogeographical regions-Northeastern Pacific, the Caribbean Sea and Eastern Tropical Pacific-we found that most species were collected as either benthic adults or planktonic larvae but seldom in both stages. Randomization tests show that this deficit of operational taxonomic units collected as both adults and larvae is extremely unlikely if larvae and adults were drawn from the same pool of species. This effect persists even in well-studied faunas. These results suggest that sampling planktonic larvae offers access to a different subset of species and thus significantly increases estimates of biodiversity compared to sampling adults alone. Spanish abstract is available in the electronic supplementary material.

A phylum-wide survey reveals multiple independent gains of head regeneration in Nemertea.

Animals vary widely in their ability to regenerate, suggesting that regenerative ability has a rich evolutionary history. However, our understanding of this history remains limited because regenerative ability has only been evaluated in a tiny fraction of species. Available comparative regeneration studies have identified losses of regenerative ability, yet clear documentation of gains is lacking. We assessed ability to regenerate heads and tails either through our own experiments or from literature reports for 35 species of Nemertea spanning the diversity of the phylum, including representatives of 10 families and all three orders. We generated a phylogenetic framework using sequence data to reconstruct the evolutionary history of head and tail regenerative ability across the phylum and found that all evaluated species can remake a posterior end but surprisingly few could regenerate a complete head. Our analysis reconstructs a nemertean ancestor unable to regenerate a head and indicates independent gains of head regenerative ability in at least four separate lineages, with one of these gains taking place as recently as the last 10-15 Myr. Our study highlights nemerteans as a valuable group for studying evolution of regeneration and identifying mechanisms associated with repeated gains of regenerative ability.

Exploring beliefs around physical activity among older adults in rural Canada.

OBJECTIVE: As physical activity can improve health and reduce the risk of chronic disease, it is important to understand the contributing factors to physical activity engagement among older adults, particularly those living in rural communities to assist in remaining active and healthy as long as possible. The purpose of this study was to gain a deeper understanding of the socio-ecological factors that influence or contribute to physical activity among rural-dwelling older adults in rural Saskatchewan, Canada. METHODS: This qualitative description explored the perceptions of physical activity among older adults living in two rural communities in the Canadian province of Saskatchewan. Semi-structured interviews were conducted with 10 adults aged 69-94. Using content analysis techniques, transcribed interview data were coded and categorized. RESULTS: Participants identified socio-ecological elements facilitating physical activity such as improved health, independence, and mobility as well as social cohesion and having opportunities for physical activity. The most common perceived environmental barrier to engaging in physical activity was the fear of falling, particularly on the ice during the winter months. Participants also cited adverse weather conditions, aging (e.g., arthritis), and family members (e.g., encouraged to "take it easy") as barriers to physical activity. CONCLUSION: Hearing directly from older adults who reside in rural Saskatchewan was determined to have the potential to improve awareness of physical activity in rural communities to support the implementation of programs and practices that will facilitate active lifestyles for older adults.

Larval Development of Two N. E. Pacific Pilidiophoran Nemerteans (Heteronemertea; Lineidae).

Unique to the phylum Nemertea, the pilidium is an unmistakable planktonic larva found in one group of nemerteans, the Pilidiophora. Inside the pilidium, the juvenile develops from a series of epidermal invaginations in the larval body, called imaginal discs. The discs grow and fuse around the larval gut over the course of weeks to months in the plankton. Once complete, the juvenile breaks free from the larval body in a catastrophic metamorphosis, and often devours the larva as its first meal. One third of nemertean species are expected to produce a pilidium, but the larvae are known for very few species; development from fertilization to metamorphosis has been described in only one species, Micrura alaskensis. Known pilidia include both planktotrophic and lecithotrophic forms, and otherwise exhibit great morphological diversity. Here, we describe the complete development in two lineiform species that are common to the northeast Pacific coast, Micrura wilsoni and Lineus sp. "red." Both species possess typical, cap-shaped planktotrophic pilidia, and the order of emergence of imaginal discs is similar to that which is described in M. alaskensis. The pilidium of Lineus sp. "red" resembles pilidia of several other species, such as Lineus flavescens, and potentially characterizes a pilidiophoran clade. M. wilsoni has relatively transparent oocytes and a pilidium with what appears to be a unique pattern of pigmentation. The adults of both species are more commonly observed in intertidal zones than their larvae are in the plankton.

Distinguishing perceived competence and self-efficacy: an example from exercise.

UNLABELLED: This article examined the conceptual and statistical distinction between perceived competence and self-efficacy. Although they are frequently used interchangeably, it is possible that distinguishing them might assist researchers in better understanding their roles in developing enduring adaptive behavior patterns. Perceived competence is conceived in the theoretical framework of self-determination theory and self-efficacy is conceived in the theoretical framework of social-cognitive theory. PURPOSE: The purpose of this study was to empirically distinguish perceived competence from self-efficacy for exercise. METHOD: Two studies evaluated the independence of perceived competence and self-efficacy in the context of exercise. Using 2 extant instruments with validity and reliability evidence in exercise contexts, the distinctiveness of the 2 constructs was assessed in 2 separate samples (n = 357 middle-aged sedentary adults; n = 247 undergraduate students). RESULTS: Confirmatory factor analysis supported the conceptual and empirical distinction of the 2 constructs. CONCLUSIONS: This study supports the conceptual and statistical distinction of perceived competence from perceived self-efficacy. Applications of these results provide a rationale for more precise future theorizing regarding their respective roles in supporting initiation and maintenance of health behaviors.

An inexpensive and worldwide available digital image analysis technique for histological fibrosis quantification in chronic hepatitis C.

Hepatic fibrosis staging is based on semiquantitative scores. Digital imaging analysis (DIA) appears more accurate because fibrosis is quantified in a continuous scale. However, high cost, lack of standardization and worldwide unavailability restrict its use in clinical practice. We developed an inexpensive and widely available DIA technique for fibrosis quantification in hepatitis C, and here, we evaluate its reproducibility and correlation with semiquantitative scores, and determine the fibrosis percentage associated with septal fibrosis and cirrhosis. 282 needle biopsies staged by Ishak and METAVIR scores were included. Images of trichrome-stained sections were captured and processed using Adobe(®) Photoshop(®) CS3 and Adobe(®) Bridge(®) softwares. The percentage of fibrosis (fibrosis index) was determined by the ratio between the fibrosis area and the total sample area, expressed in pixels calculated in an automated way. An excellent correlation between DIA fibrosis index and Ishak and METAVIR scores was observed (Spearman's r = 0.95 and 0.92; P < 0.001, respectively). Excellent intra-observer reproducibility was observed in a randomly chosen subset of 39 biopsies with an intraclass correlation index of 0.99 (95% CI, 0.95-0.99). The best cut-offs associated with septal fibrosis and cirrhosis were 6% (AUROC 0.97, 95% CI, 0.95-0.99) and 27% (AUROC 1.0, 95% CI, 0.99-1), respectively. This new DIA technique had high correlation with semiquantitative scores in hepatitis C. This method is reproducible, inexpensive and available worldwide allowing its use in clinical practice. The incorporation of DIA technique provides a more complete evaluation of fibrosis adding the quantification to architectural patterns.

From trochophore to pilidium and back again - a larva's journey.

Nemerteans, a phylum of marine lophotrochozoan worms, have a biphasic life history with benthic adults and planktonic larvae. Nemertean larval development is traditionally categorized into direct and indirect. Indirect development via a long-lived planktotrophic pilidium larva is thought to have evolved in one clade of nemerteans, the Pilidiophora, from an ancestor with a uniformly ciliated planuliform larva. Planuliform larvae in a member of a basal nemertean group, the Palaeonemertea, have been previously shown to possess a vestigial prototroch, homologous to the primary larval ciliated band in the trochophores of other spiralian phyla, such as annelids and mollusks. We review literature on nemertean larval development, and include our own unpublished observations. We highlight recent discoveries of numerous pilidiophoran species with lecithotrophic larvae. Some of these larvae superficially resemble uniformly ciliated planuliform larvae of other nemerteans. Others possess one or two transverse ciliary bands, which superficially resemble the prototroch and telotroch of some spiralian trochophores. We also summarize accumulating evidence for planktotrophic feeding by larvae of the order Hoplonemertea, which until now were considered to be lecithotrophic. We suggest that 1) non-feeding pilidiophoran larval forms are derived from a feeding pilidium; 2) such forms have likely evolved many times independently within the Pilidiophora; 3) any resemblance of such larvae to the trochophores of other spiralians is a result of convergence and that 4) the possibility of planktotrophy in hoplonemertean larvae may influence estimates of pelagic larval duration, dispersal, and population connectivity in this group.

Development and impact of exercise self-efficacy types during and after cardiac rehabilitation.

OBJECTIVE: Cardiovascular disease (CVD) is the leading cause of death in the developed world. Cardiac rehabilitation (CR) is a comprehensive treatment program centered on structured exercise that has been demonstrated to achieve significant decreases in mortality and morbidity in cardiac patients, yet few patients adhere to exercise post-CR and so fail to maintain any health benefits accrued during rehabilitation. One reason for the lack of adherence might be that CR fails to address the challenges to adherence faced by patients when they no longer have the resources and structure of CR to support them. Self-efficacy (SE) is a robust predictor of behavioral persistence. This study therefore focuses on changes in different types of SE during CR and the relationship of SE to subsequent levels of physical activity. METHOD: A sample of 63 CR patients completed assessments of task, scheduling and coping SE at baseline and the end of CR, as well as self-reported exercise behavior at the end of CR and 1-month post-CR. RESULTS: Task SE (for performing elemental aspects of the behavior) was found to be most changed type of SE during CR and was strongly related to self-reported exercise at the end of CR. However, scheduling SE (for performing the behavior regularly) was most strongly related to self-reported exercise post-CR. CONCLUSIONS: These results are theoretically consistent and suggest that scheduling SE should be targeted during CR to improve post-CR exercise adherence.

Effects of lysophosphatidic acid on calpain-mediated proteolysis of focal adhesion kinase in human prostate cancer cells.

BACKGROUND: Calcium-mediated proteolysis plays an important role in cell migration. Lysophosphatidic acid (LPA), a lipid mediator present in serum, enhances migration of carcinoma cells. The effects of LPA on calpain-mediated proteolysis were, therefore, examined in PC-3, a human prostate cancer cell line. METHODS: Cultured PC-3 cells were used in studies utilizing pharmacologic interventions, immunoblotting, and confocal immunolocalization. RESULTS: Focal adhesion kinase (FAK), a tyrosine kinase involved in cell adhesion, is rapidly proteolyzed in serum-starved PC-3 cells exposed to the calcium ionophore, ionomycin; Nck, p130CAS, PKCα, and Ras-GAP are also degraded. Thapsigargin, which causes more moderate increases in intracellular calcium, induces partial proteolysis of these proteins. Calpain inhibitors block the proteolytic responses to ionomycin and thapsigargin. Ionomycin does not induce proteolysis in cells maintained in serum, suggesting a protective role for growth factors contained in serum. LPA causes minor FAK proteolysis when added alone, but protects against ionomycin-induced proteolysis in a time-dependent manner. LPA also protects against the cell detachment that eventually follows ionomycin treatment. The response to LPA is blocked by an LPA receptor antagonist. A similar effect of LPA is observed in ionomycin-treated Rat-1 fibroblasts. In PC-3 cells, the protective effects of LPA and serum are correlated with phosphorylation and redistribution of paxillin, suggesting roles for phosphorylation-mediated protein-protein interactions. CONCLUSIONS: The complex effects of LPA on calpain-mediated proteolysis of FAK and other adhesion proteins are likely to play a role in the ability of LPA to promote attachment, migration, and survival of prostate cancer cells.

Exploring the relationship between socioeconomic status, control beliefs and exercise behavior: a multiple mediator model.

The purpose of this study was to examine the relationship between control beliefs, socioeconomic status and exercise intentions and behavior. Specifically, we examined whether distal and proximal control beliefs mediated the association between socioeconomic status and exercise intentions and behavior. A one time, cross sectional mail out survey (N = 350) was conducted in a large urban Canadian city. Distal (i.e., personal constraints) and proximal (i.e., scheduling self-efficacy) control beliefs mediated the association between socioeconomic status and exercise, explaining approximately 30% of the variance. Proximal control beliefs (i.e., scheduling self-efficacy) partially mediated the association between socioeconomic status and intentions, with the models explaining approximately 50% of the variance. Compared to individuals with lower socioeconomic status, individuals with higher socioeconomic status reported more exercise and stronger intentions to exercise. This was at least partly because higher socioeconomic status respondents reported fewer barriers in their lives, and were more confident to cope with the scheduling demands of exercise.

Understanding physical activity intentions and behavior in postmenopausal women: an application of the theory of planned behavior.

BACKGROUND: In the present paper, we report the social cognitive correlates of physical activity (PA) intentions in postmenopausal women using the two-component theory of planned behavior (TPB) framework. PURPOSE: The primary objective of the present study was to investigate the utility of the TPB in understanding PA behavior in postmenopausal women. METHOD: Postmenopausal women (N = 297) residing in Southern Alberta, Canada completed a mailed questionnaire that assessed self-reported PA and TPB constructs. RESULTS: Data indicated that 67% of postmenopausal women intended to engage in PA behavior consistent with the public health PA guidelines. Multiple regression analysis suggested that the TPB model explained 44% of the variance in PA intentions with instrumental attitude (ß = 0.33), affective attitude (ß = 0.29), descriptive norm (ß = 0.19), and self-efficacy (ß = 0.24) making significant contributions to PA intentions. Postmenopausal women meeting PA guidelines reported higher scores across all TPB variables when compared to women not meeting PA guidelines. Unique behavioral, normative, and control beliefs were also elicited. CONCLUSION: The two-component TPB framework appears to be a useful model for understanding PA intentions and behavior in postmenopausal women. These data can be used in the development and establishment of PA behavior intervention and health promotion materials designed to facilitate PA intentions and behavior in postmenopausal women.

Quality of life and psychosocial health in postmenopausal women achieving public health guidelines for physical activity.

OBJECTIVE: The aim of this study was to determine if there are differences in health-related quality of life (HRQoL) and psychosocial health between postmenopausal women who meet public health physical activity (PA) guidelines versus those who do not (ie, self-report) and those women who achieve at least 7,500 steps . day versus those who do not (ie, via objective monitor). METHODS: Postmenopausal women (n = 297) residing in Southern Alberta, Canada, completed a mailed questionnaire that assessed self-reported PA, HRQoL, and psychosocial health outcomes. Total daily steps were assessed with a pedometer via a 3-day step monitoring period. RESULTS: Of the postmenopausal women, 43.1% were meeting public health PA guidelines. A significant multivariate model (Wilks lambda = 0.968, F2,294 = 4.918, P = 0.008) indicated that women achieving public health PA guidelines reported higher HRQoL on both the physical (mean difference [Mdiff] = 2.4, P = 0.008, d [effect size] = 0.31) and mental (Mdiff = 2.3, P = 0.011, d = 0.30) component scales of the RAND-12 compared with women not achieving PA guidelines. Furthermore, women achieving at least 7,500 steps . day-1 indicated significantly higher scores on the physical component scale (Mdiff = 4.33, P < 0.001, d = 0.56) than did women achieving fewer than 7,500 pedometer steps . day-1. CONCLUSIONS: These findings lend support for the health benefits of achieving public health PA guidelines in postmenopause and further the rationale for developing, evaluating, and implementing strategically designed PA behavior change programs for postmenopausal women.

Signal transduction responses to lysophosphatidic acid and sphingosine 1-phosphate in human prostate cancer cells.

BACKGROUND: Lysophosphatidic acid (LPA) and sphingosine-1-phosphate (S1P) are lipid mediators that bind to G-protein-coupled receptors. In this study, signaling responses to 18:1 LPA and S1P were examined in parallel in three human prostate cancer cell lines: PC-3, Du145, and LNCaP. METHODS: Receptor expression was assessed by RT-PCR, Northern blotting, and immunoblotting. Cellular responses to mediators were studied by proliferation assays, phosphoprotein immunoblotting, and phospholipid metabolism assays. RESULTS: All cell lines express mRNA for both LPA and S1P receptors. PC-3 and Du145, but not LNCaP, proliferate in response to LPA and S1P. Epidermal growth factor (EGF), phorbol 12-myristate 13-acetate (PMA), LPA, and S1P induce activation of Erks in PC-3 and Du145; only EGF and PMA activate Erks in LNCaP. In Du145 and PC-3, Akt is activated by EGF, LPA, and S1P. Akt is constitutively active in LNCaP; EGF but not LPA or S1P stimulates further phosphorylation. FAK is phosphorylated in response to both LPA and S1P in PC-3 and Du145, but not in LNCaP. LPA and S1P stimulate phospholipase D (PLD) activity to varying extents in the different cell lines. Notably, both lipid mediators activate PLD in LNCaP. In Du145, LPA, but not S1P, activates PLD and enhances cellular production of LPA. CONCLUSIONS: Although both LPA and S1P induce signal transduction in all prostate cancer cell lines studied, a proliferation response is observed only when the Erk, Akt, and FAK pathways are activated. Other responses to the lipid mediators, such as PLD activation, likely contribute to other cellular outcomes.

The enduring impact of social factors on exercise tolerance in men attending cardiac rehabilitation.

PURPOSE: This study explored the influence of social support on a prognostic indicator among cardiac patients, exercise tolerance. The relationship of sociodemographic factors to social support was examined, as well as the role of social support as a potential mediator between sociodemographic factors and exercise tolerance. METHODS: Archival data were collected from a sample of 254 men referred to cardiac rehabilitation. An exercise tolerance test was completed upon entry into cardiac rehabilitation, after 14 weeks, and after 9 months. RESULTS: Sociodemographic factors and social support reported upon entry into the cardiac rehabilitation program were related to initial and post-cardiac rehabilitation exercise tolerance, after controlling for admitting diagnoses, medical history, smoking, and perceived severity of illness. Overall, 28% of the variance in exercise tolerance was explained at baseline, 19% at 14 weeks, and 20% at 9 months. Specifically, older individuals had poorer exercise tolerance, whereas those with more income had better exercise tolerance. Social support was positively related to exercise tolerance at all 3 times. Older men reported less social support than younger men did, and those with more income reported more social support. However, social support did not mediate the relationship between sociodemographic factors and exercise tolerance. CONCLUSIONS: Results support the potential use of broad social factors in examining the determinants of prognostic factors for heart patients.

Soporte circulatorio con albúmina en la cirrosis hepática / Circulatory support with albumin in liver cirrhosis

No disponible