We conclude that the switching of pigment granules between the two major cytoskeletal systems is independent of the densities of MT or AF but is tightly controlled by signaling events.

The mitotic spindle is a microtubule (MT)-based molecular machine that serves for equal segregation of chromosomes during cell division. The formation of the mitotic spindle requires the activity of MT motors, including members of the kinesin-14 family. Although evidence suggests that kinesins-14 act by driving the sliding of MT bundles in different areas of the spindle, such sliding activity had never been demonstrated directly. To test the hypothesis that kinesins-14 can induce MT sliding in living cells, we developed an in vivo assay, which involves overexpression of the kinesin-14 family member Drosophila Ncd in interphase mammalian fibroblasts. We found that green fluorescent protein (GFP)-Ncd colocalized with cytoplasmic MTs, whose distribution was determined by microinjection of Cy3 tubulin into GFPtransfected cells. Ncd overexpression resulted in the formation of MT bundles that exhibited dynamic "looping" behavior never observed in control cells. Photobleaching studies and fluorescence speckle microscopy analysis demonstrated that neighboring MTs in bundles could slide against each other with velocities of 0.1 m/s, corresponding to the velocities of movement of the recombinant Ncd in in vitro motility assays. Our data, for the first time, demonstrate generation of sliding forces between adjacent MTs by Ncd, and they confirm the proposed roles of kinesins-14 in the mitotic spindle morphogenesis. INTRODUCTIONThe mitotic spindle is a molecular machine that serves for equal segregation of chromosomes during mitosis. The principal structural components of the mitotic spindle are cytoplasmic microtubules (MTs) organized into two polarized (minus ends at the center) radial arrays, located at a distance from each other. MT organization in the mitotic spindle is achieved by MT motors, kinesins and dyneins, which generate force for movement toward the plus or minus ends of MTs and that participate in the transport of chromosomes to the spindle poles, spindle elongation during anaphase, regulation of the MT turnover rates, and spindle morphogenesis (for review, see Sharp et al., 2000b;Karsenti and Vernos, 2001;McIntosh et al., 2002;Scholey et al., 2003;Gadde and Heald, 2004;Wadsworth and Khodjakov, 2004).A special role in the formation and maintenance of the mitotic spindle belongs to the minus-end-directed members of the kinesin-14 subfamily. Unlike conventional kinesin, kinesin-14 family members have motor domains at the carboxy terminus (for review, see Ovechkina and Wordeman, 2003). The best studied kinesin-14 members are Drosophila Ncd (Komma et al., 1991;Matthies et al., 1996) and Saccharomyces cerevisiae Kar3 (Meluh and Rose, 1990). These MT motors, and their mammalian (Matuliene et al., 1999;Mountain et al., 1999;Zhu et al., 2005) and plant (Vanstraelen et al., 2006) homologues, play essential roles in mitosis and meiosis. Their activities are important for the formation of the mitotic spindle poles (Goshima and Vale, 2003; MoralesMulia and Scholey, 2005;Zhu et al., 2005) and for regulation of the distance...

Renewable energy resource utilisation is becoming more prevalent in society and can be a sustainable method to meet rising energy demand and consumption. The International Renewable Energy Agency reports that presently, approximately 33% of total electricity output around the world is from renewable energy sources. However, in Nigeria, the World Bank reported this figure as 18.2% in 2015. It is important to understand how Nigeria can raise this average as the world moves towards less use of fossil fuels. Therefore, the aim of this work was to provide a review of the established literature, which can then be used to support the development of renewable energy systems in Nigeria. The methodology employed for the study of the literature involved a systematic review method, including identification, screening, eligibility and inclusion criterium steps. Understanding the national energy landscape is essential to support potential projects, and consequently, energy supply, demand and consumption in Nigeria are observed. The review examined renewable energy sources in Nigeria with a focus on solar and biomass/bioenergy. The levelised cost of electricity from renewable technologies was analysed, and the paper identified and evaluated past projects centered on solar and biomass, presenting three main case studies. The results indicate that solar and biomass have the most potential for energy generation in Nigeria, with 4–6.5 kWh/m2 of solar irradiation available per day and approximately 2.3 × 109 GJ bioenergy potential per year. However, solar PV is currently of most interest in Nigeria due to the lower cost of on-grid solar PV electricity, which can comfortably compete with fossil fuels. Nevertheless, costs still need to be lowered to compete fully. Finally, the findings also indicate that there is an omission in the literature surrounding the existing renewable projects and technologies in Nigeria.