Anthropogenic Harvesting Pressure and Changes in Life History: Insights from a Rocky Intertidal Limpet

The importance of large breeding individuals for maintaining the health of marine fish and invertebrate populations has long been recognized. Unfortunately, decades of human harvesting that preferentially remove larger individuals have led to drastic reductions in body sizes of many of these species. Such size-selective harvesting is particularly worrisome for sequentially hermaphroditic species where the larger size classes are composed primarily of one sex. Whether these species can maintain stable sex ratios under sustained harvesting pressure depends on the level of plasticity of their life-history traits. Here, we show that populations of a marine limpet (Lottia gigantea) can adjust a fundamental aspect of their life history (the timing of sex change) when subjected to size-selective harvesting. As predicted by theoretical models, individuals from harvested populations change sex at smaller sizes and grow at slower rates compared to individuals from protected populations. In addition, the relative size at which the change from male to female occurs remains constant (?0.75; size at sex change/maximum size) across populations, regardless of harvesting pressure. Our results show that population-level demographic and life-history data, in conjunction with existing theory, can be sufficient to predict the responses of sequential hermaphrodites to harvesting pressure. Furthermore, they suggest such species can potentially adapt to size-selective harvesting

Cytotoxicity of in vitro exposure of polystyrene latex bead nanoparticles to human keratinocyte (HaCaT) cells and human cervical cancer (HeLa)cells

yesNanoparticles are increasingly used in industry and medicine due to their unique physiochemical properties such as their small size, charge, shape, chemical architecture, large surface area, surface reactivity and media interactions, etc [1-5]. However, very little is still known on the interactions between nanoparticles and the biological system. This study aims to evaluate the cytotoxicity of polystyrene latex bead nanoparticles on HaCat and HeLa cell lines. Carboxyl-modified 20 nm polystyrene NPs core labelled with fluorophore were from Invitogen. We chose to use polystyrene NPs because this specific type of NP is being increasingly characterized for use in nanosensors and drug nanocarrier investigations. 1x 104 cells/100 μl of cell culture medium were plated into 96-well plates in triplicate, measuring activity post 24 hours at concentrations of 10, 50, 100 μg/ml of polystyrene NPs exposure. The extracellular lactate dehydrogenase release was measured by using a colorimetric CytoTox 96 nonradioactive assay kit from Promega and the absorbance were recorded at 450nm (FLUO-star) with Elisa micro plate reader. The MTT assay was used to evaluate mitochondrial activity. This was performed by inserting a premixed optimized dye solution in the culture wells. The Absorbance was recorded at 570 nm, from the recorded absorbance is directly proportional to the number of live cells. The cell lines were kept in a plastic T-75cm2 tissue culture flasks grown in DMEM. We found that cytotoxicity of polystyrene NPs on both cells was concentration dependent. For Hela cells, with exporesure of polystyrene NPs at concentrations of 10, 50, 100 μg/ml for 24 hrs, the percentage cytotoxicity of positive control for LDH assay was 35.9%, 49.5% and 73.4% respectively. With the MTT cell viability assay the percentage MTT reduction of negative control was 88.9%, 42.9% and 26.4% respectively. Cell toxicity increased with increasing polystyrene NPs concentration. For HaCaT cells, the cytotoxic effect is less significant than those on Hela cells. With MTT assay, when compared to HaCaT cells exposed to a negative control containing only PBS, the cell viability decreased as the concentrations of NPs increased. Cells exposed to 100μg/ml of polystyrene NPs for a period of 24 hours compared to those exposed to a positive control (100% cell viability) had an average cell viability of 49%, with those numbers decreasing from 59% for cells exposed to 10μg/ml of polystyrene NPs to 57% for cells exposed to 50μg/ml of polystyrene NPs. Our results indicated that polystyrene NPs acted differently in two different cell types and that cautions should be taken about its cytotoxicity. Further understanding of the mechanism involving the ROS generation could provide more information on how polystyrene NPs increase cytotoxicity

South African ICT Skills Deficiency

Information Communication Technology (ICT) is part of everyday life and the skills needed are quickly becoming a prerequisite for daily life. There is a dire shortage of ICT skills in South Africa and any attempt to circumvent this problem creates an even greater urgency. Several reports and much research have been conducted to establish the extent of the problem and many proposals and initiatives have been established to address it, but the problem seems to prevail. The aim of this study is to investigate the problems contributing to ICT skills shortages in South Africa, the initiatives in place to address it and to determine a possible need for skills by looking at other research and reports

Investigation into the Material Response of Concretes when Subject to Blast and Fragment Loading

Vehicle Bourne Improvised Explosive Devices (VBIEDs) are utilised globally by terrorist organisations and radical individuals to inflict mass casualties. Many of these casualties are caused by the collapse of structures due to damage sustained by the blast and fragmentation loadings produced by the VBIED. As such it is important to understand how these loadings affect structures so as to improve design and increase structure survivability. Historically significant research effort has been invested in understanding the blast and fragmentation loadings produced by conventional weapons. The loadings produced by VBIEDs are often considerably different with much larger, slower fragments. Little work has been undertaken in documenting these loadings and how they damage structural materials such as concrete. As such, when designing for threats of this type the fragmentation loading produced by a VBIED is often ignored. This thesis aims to investigate; the loadings produced by bare explosive charges and VBIED surrogate charges, and how the blast and fragmentation loadings contribute to the deflection and damage of concrete panels. Panels with approximate dimensions of 1200 mm by 1200 mm and with thicknesses varying between 100 and 200 mm were tested. Panels were constructed from low-strength concrete, moderate-strength concrete, and Ultra-High Performance Concrete (UHPC). Testing found that the fragment loading produced by the VBIED surrogate was sufficient to produce a global response in the panels as well as localised damage. As such, fragmentation loadings should not be ignored when predicting the response of structures to VBIED threats. Synergistic effects, between the blast and fragmentation loadings were, were observed for panels with sufficiently low flexural stiffness.Thesis (MPhil) -- University of Adelaide, School of Civil, Environmental & Mining Engineering, 201

Organizational adaption to changes in public objectives for management of Cache La Poudre River system

Research Period: 1965-1969.June 30, 1969.Submitted to Office of Water Resources Research, U.S. Department of Interior.Project A-005-COLO, Grant agreement no. 14-01-0001-1625

Impact of transportation equipment shortages and substandard transportation service in 1969 on Iowa country elevators

Shortages of transportation equipment suffered by Iowa grain shippers over many years reached serious proportions in 1969. The situation resulted from increases in the quantities of grain sold by farmers during the decade of the 60\u27s and a decline in the availability of railroad and truck equipment for grain movements. Changes in the availability of transportation equipment have serious implications for the grain industry. The inability to ship grain results in dollar penalties for the failure to meet contract delivery dates. Costs are incurred to finance inventories, to employ other methods of storage, and in the use of substandard equipment and services.https://lib.dr.iastate.edu/specialreports/1065/thumbnail.jp

Assessing long-distance RNA sequence connectivity via RNA-templated DNA-DNA ligation

Many RNAs, including pre-mRNAs and long non-coding RNAs, can be thousands of nucleotides long and undergo complex post-transcriptional processing. Multiple sites of alternative splicing within a single gene exponentially increase the number of possible spliced isoforms, with most human genes currently estimated to express at least ten. To understand the mechanisms underlying these complex isoform expression patterns, methods are needed that faithfully maintain long-range exon connectivity information in individual RNA molecules. In this study, we describe SeqZip, a methodology that uses RNA-templated DNA-DNA ligation to retain and compress connectivity between distant sequences within single RNA molecules. Using this assay, we test proposed coordination between distant sites of alternative exon utilization in mouse Fn1, and we characterize the extraordinary exon diversity of Drosophila melanogaster Dscam1

Anthropogenic Harvesting Pressure and Changes in Life History: Insights from a Rocky Intertidal Limpet

The importance of large breeding individuals for maintaining the health of marine fish and invertebrate populations has long been recognized. Unfortunately, decades of human harvesting that preferentially remove larger individuals have led to drastic reductions in body sizes of many of these species. Such size-selective harvesting is particularly worrisome for sequentially hermaphroditic species where the larger size classes are composed primarily of one sex. Whether these species can maintain stable sex ratios under sustained harvesting pressure depends on the level of plasticity of their life-history traits. Here, we show that populations of a marine limpet (Lottia gigantea) can adjust a fundamental aspect of their life history (the timing of sex change) when subjected to size-selective harvesting. As predicted by theoretical models, individuals from harvested populations change sex at smaller sizes and grow at slower rates compared to individuals from protected populations. In addition, the relative size at which the change from male to female occurs remains constant (similar to 0.75; size at sex change/maximum size) across populations, regardless of harvesting pressure. Our results show that population-level demographic and life-history data, in conjunction with existing theory, can be sufficient to predict the responses of sequential hermaphrodites to harvesting pressure. Furthermore, they suggest such species can potentially adapt to size-selective harvesting.This is the publisher’s final pdf. The published article is copyrighted by University of Chicago and can be found at: http://www.press.uchicago.edu/journals.html.Keywords: Age, Sex change, Animals, Population structure, Growth, Body size, Fish, Southern California, Owl limpet, Lottia gigantea