bluuebunny/crossref_metadata_2025 huggingface dataset:
In Vitro Protein Digestibility of Dietary Ingredients Throughout Ontogeny of California Halibut, Paralichthys californicus, Larvae
Authors: Martínez‐Montaño E. , Lazo J. P.
Published: February 2012

Digestive capacity varies substantially in marine fish larvae during development, and the formulation of larval diets does not take this into account. The objectives of this study were to assess in vitro protein digestibility of dietary ingredients throughout the ontogeny of digestive system in California halibut, Paralichthys californicus, larvae so as to identify adequate protein sources for each stage of development. Protein digestibility of potential sources was evaluated using the pH‐STAT technique. Digestive enzymes utilized for the in vitro assays were obtained from homogenates of whole bodies (9, 15, and 26 days post hatch [dph]) and dissected guts of larvae (39 and 51 dph) sampled at different stages of development. Significant differences in degree of protein hydrolysis (DH) were found among developmental stages for some ingredients. Meals elaborated with rotifers and Artemia showed the highest DH with a tendency to decrease as larval development progressed. Digestibility of casein was poor early in development and increased as it progressed. In contrast, soybean and krill meals were poorly digested throughout development, which may be attributed to differences in the nature or quality of the ingredient. Results from this study highlight the importance of evaluating the digestibility of protein sources through larval development to formulate successful, stage‐specific weaning diets.
Photocatalytic Disinfection of Bacterial Pollutants Using Suspended and Immobilized TiO2 Powders
Authors: Ede Sarah , Hafner Louise , Dunlop Patrick , Byrne John , Will Geoffrey
Published: February 2012

The photocatalytic disinfection of Enterobacter cloacae and Enterobacter coli using microwave (MW), convection hydrothermal (HT) and Degussa P25 titania was investigated in suspension and immobilized reactors. In suspension reactors, MW‐treated TiO2 was the most efficient catalyst (per unit weight of catalyst) for the disinfection of E. cloacae. However, HT‐treated TiO2 was approximately 10 times more efficient than MW or P25 titania for the disinfection of E. coli suspensions in surface water using the immobilized reactor. In immobilized experiments, using surface water a significant amount of photolysis was observed using the MW‐ and HT‐treated films; however, disinfection on P25 films was primarily attributed to photocatalysis. Competitive action of inorganic ions and humic substances for hydroxyl radicals during photocatalytic experiments, as well as humic substances physically screening the cells from UV and hydroxyl radical attack resulted in low rates of disinfection. A decrease in colony size (from 1.5 to 0.3 mm) was noted during photocatalytic experiments. The smaller than average colonies were thought to occur during sublethal •OH and O2•− attack. Catalyst fouling was observed following experiments in surface water and the ability to regenerate the surface was demonstrated using photocatalytic degradation of oxalic acid as a model test system.
UV Released Factors Induce Antioxidant Defense in A375 Cells
Authors: Ghosh Rita , Guha Dipanjan , Bhowmik Sudipta
Published: February 2012

UV light leads to release of different secretory factors from irradiated cells of which some of them have been characterized. We have reported earlier that cells exposed to the supernatant medium from irradiated cells were resistant to killing by some genotoxic agents. In this study, we present our finding that demonstrates DNA damage induced by UV or H2O2 is lowered on prior exposure to the UV released factors (UVRF). Production of ROS in cells and lipid peroxidation was also lowered. It was found that treatment of unexposed cells with UVRF present in the supernatant medium altered the antioxidant defense activity in cells. Significant was the increase in catalase (CAT) and Cu–Zn superoxide dismutase (SOD) activity, whereas glutathione peroxidase (GPx) and reduced glutathione (GSH) levels remained unaffected. Cells exposed to UVRF prior to UV or H2O2 treatment also experienced such upregulation; however, the remarkable increase in the GPx activity exhibited by these cells was not observed in cells exposed to H2O2 or UV alone. It appears that exposure to UVRF tinkered with antioxidant defense in cells to facilitate its proliferation upon assault by an agent that can produce oxidative damage.
Calibration of the New Certified Reference Materials ERM‐AE633 and ERM‐AE647 for Copper and IRMM‐3702 for Zinc Isotope Amount Ratio Determinations
Authors: Moeller Kirsten , Schoenberg Ronny , Pedersen Rolf‐Birger , Weiss Dominik , Dong Shuofei
Published: February 2012

The commonly used, but no longer available, reference materials NIST SRM 976 (Cu) and ‘JMC Lyon’ (Zn) were calibrated against the new reference materials ERM®‐AE633, ERM®‐AE647 (Cu) and IRMM‐3702 (Zn), certified for isotope amount ratios. This cross‐calibration of new with old reference materials provides a continuous and reliable comparability of already published with future Cu and Zn isotope data. The Cu isotope amount ratio of NIST SRM 976 yielded δ65/63Cu values of −0.01 ± 0.05‰ and −0.21 ± 0.05‰ relative to ERM®‐AE633 and ERM®‐AE647, respectively, and a δ66/64ZnIRMM‐3702 value of −0.29 ± 0.05‰ was determined for ‘JMC Lyon’. Furthermore, we separated Cu and Zn from five geological reference materials (BCR‐2, BHVO‐2, BIR‐1, AGV‐1 and G‐2) using a two‐step ion‐exchange chromatographic procedure. Possible isotope fractionation of Cu during chromatographic purification and introduction of resin‐ and/or matrix‐induced interferences were assessed by enriched 65Cu isotope addition. Instrumental mass bias correction for the isotope ratio determinations by MC‐ICP‐MS was performed using calibrator‐sample bracketing with internal Ni doping for Cu and a double spike approach for Zn. Our results for the five geological reference materials were in very good agreement with literature data, confirming the accuracy and applicability of our analytical protocol.
Women’s Strategic Responses to Intimate Partner Violence: A Study in a Rural Community of Bangladesh
Authors: Sayem Amir Mohammad , Khan Mohammad Aftab Uddin
Published: February 2012

The objective of this study was to explore women’s strategic responses to physical violence perpetrated by an intimate partner. Twenty women from a rural area of the Narshingdi district in the Dhaka division of Bangladesh who experienced physical violence at home participated in the study. Development of the interview protocol and data analysis were carried out by applying the consensual qualitative research (CQR) method. The results showed that several themes, such as women’s responses to intimate partner violence, arose from the data. First, coping strategies to pre‐violent events included three themes: (i) leaving the scene; (ii) trying to divert attention; and (iii) preparing to protest. Women’s strategic responses to violent events consisted of four themes: (i) leaving the scene; (ii) remaining silent or no giving response; (iii) seeking help from others; and (iv) protesting against the violence. Lastly, women’s strategic responses to post‐violent events consisted of three themes: (i) temporary abstinence; (ii) verbally abusive behavior to family members; and (iii) going to the parental home. Given the findings of this study, we conclude by suggesting that more work is needed to better understand effective strategies and to draw women to institutional services to prevent violence to a greater extent.
Trends of Income Inequality Among the Elderly in Korea
Authors: Hong Baeg Eui , Kim Hye youn
Published: February 2012

This study investigates the overall trend of inequality among the elderly in Korea and to examine what the most influential factor is for these changes. Although inequality among the elderly is far greater than it is for any other group, little attention has been given to how inequality changes over time. Used are data from the Urban Household Survey with five‐year intervals from 1986 to 2006. The results show that inequality within a cohort increases over time and that earnings and benefits from occupational retirement plans are the most influential factors on overall inequality changes. In addition, the impact of public transfers has gradually increased during the past twenty years. The results imply that our society needs to enact a social policy for lessening earnings inequality in the labor market and to increase public transfers for the elderly.
Peace parks and transboundary initiatives: implications for marine conservation and spatial planning
Authors: Mackelworth Peter
Published: February 2012

Increasing use of the marine environment makes the development of spatial planning desirable. However, ambiguity and connectivity in the marine system has the potential to create conflict between neighboring States, particularly in contested border regions with overlapping ecosystems and migratory species. Interest in the concept of transboundary conservation is expanding in the marine system. Increasingly, there is a strategic move toward attempting to combine conservation issues with resolving conflicts between States by promoting these initiatives as peace parks. Although this strategy has the potential to provide solutions there are risks involved. A review of nine marine transboundary initiatives provides insights into hazards and best practices that may inform future conservation and spatial planning in this system. Results suggest that, like most conservation, long‐term sustainability of projects is based on transparency, the availability of appropriate funding, and governmental will. While the branding of marine transboundary conservation initiatives as peace parks may help to provide initial political impetus to projects, maintaining governmental interest is a significant long‐term issue. This review aims to stimulate the debate on strategies for developing marine transboundary conservation for the future, bearing in mind the potential for conflict in these regions.
Ultrastructural changes in the Golgi apparatus and secretory granules of HL‐60 cells treated with the imino sugar N‐butyldeoxynojirimycin
Authors: Neises Gabrielle R , Woodman Philip G , Butters Terry D , Ornberg Richard L , Platt Frances M
Published: February 2012

The imino sugar N‐butyldeoxynojirimycin inhibits the N‐linked oligosaccharide processing enzymes α‐glucosidases I and II, and the ceramide specific glucosyltransferase which catalyses the first step in glucosphingolipid biosynthesis. We have studied the effects of this compound on the ultrastructure of HL‐60 cells to identify novel activities of this compound. Treatment of HL‐60 cells with this imino sugar results in several morphological changes within the cell, none of which result in cytotoxicity. The plasma membrane stains heavily with potassium ferrocyanide within 30 min following addition of the compound to the medium, and there is then a time dependent involvement of all other intracellular membranes. Secretory granules become enlarged and lose their dense core morphology and appear either empty and vacuolated or have low density contents. However, the most striking effect of NB‐DNJ treatment is on the Golgi apparatus. The Golgi exhibits a time‐dependent change from typical Golgi morphology to a structure almost completely devoid of cisternae and consisting predominantly of vesicles. All the observed changes are fully reversible on withdrawal of the compound.
Delaying the onset of M phase in NIH 3T3 cells blocked in early S phase occurs via accumulating cyclin B1 and tyrosine‐phosphorylated p34cdc2 in the nucleus
Authors: David‐Pfeuty The´re`se , Nouvian‐Dooghe Yolande , Rouillard Dany
Published: February 2012

An affinity‐purified antibody (anti‐Cdc2C) raised against the carboxy terminal sequence LDNQIKKM of p34cdc2 uncovered in NIH 3T3 cells a protein subpopulation, the location and the level of accumulation of which evolve during progression through the cell cycle: it first emerges inside the nucleus in late G1/early S phase and continues to build up principally in this location throughout S phase; a cytoplasmic expression then becomes apparent near the end of S phase, develops during G2 and sometimes prevails over the nuclear expression; it finally relocates to the nucleus in early prophase. We propose that a major part of this subpopulation would represent p34cdc2 molecules existing inside a complex with cyclin B1. NIH 3T3 cells arrested in early S phase with aphidicolin do not commit prematurely to mitosis which indicates that the regulatory pathway involved in preserving the temporal order of S and M phases is functioning in these conditions. Conjugated Western blot analysis and immunofluorescence microscopy showed that cyclin A, cyclin B1 and tyrosine‐phosphorylated p34cdc2 continue to build up predominantly in the nucleus of the arrested cells. After release from the block, the cells rapidly reenter S and G2 phases and, concomitantly, cyclin B1 and tyrosine‐phosphorylated p34cdc2 relocate to the cytoplasm before redistributing again in the nucleus in early prophase. These data would suggest that delaying the onset of M phase in NIH 3T3 cells in which the rate of DNA replication is reduced, is first ensured by a mechanism that prevents the cytoplasmic relocation of inactive p34cdc2/cyclin B1 complexes continually forming in the nucleus once the G1 period of mitotic cyclin instability is over.
Oligonucleotide biological activity: Relationship to the cell cycle and nuclear transport
Authors: Wu‐Pong Susanna , Bard Julie , Huffman John , Jimerson Jason
Published: February 2012

Previous studies suggest that oligodeoxynucleotide (ODN) cellular uptake is cell cycle‐dependent which may have important implications in cancer cell targeting. To further our understanding of ODN transport and activity, this study examines the relationships between the cell cycle, ODN cellular uptake, intracellular transport, and activity. An antisense c‐myc ODN 21‐mer was used to study ODN cellular uptake in Rauscher erythroleukemia cells synchronized by either chemical methods or flow cytometry. ODN uptake was examined using subcellular fractionation and confocal fluorescence microscopy. Western blot analysis was used to measure ODN‐mediated decreases in c‐myc protein levels. Intracellular ODN distribution and extent of uptake was influenced by the phase of the cell cycle, but the mechanism of uptake was not. The relative activity of the antisense ODN was positively correlated to ODN distribution to the cytosol, but negatively correlated to total cellular uptake. Although ODN total cellular uptake is positively influenced by the cell cycle, retention of the ODN in the cytosol (presumably extra‐vesicularly) appeared to be relevant in determining the activity of an antisense ODN. Novel methods to target cytosol‐acting drugs to the cytoplasm may therefore be warrented.
Intracellular pH regulation in rat round spermatids
Authors: Osses Nelson , Pancetti Floria , Benos Dale J , Reyes Juan G
Published: February 2012

Intracellular pH has been shown to be an important physiological parameter in cell cycle control and differentiation, aspects that are central to the spermatogenic process. However, the pH regulatory mechanisms in spermatogenic cells have not been systematically explored. In this work, measuring intracellular pH (Hi) with a fluorescent probe (BCECF), membrane potential with a fluorescent lipophilic anion (bisoxonol), and net movement of acid using a pH‐stat system, we have found that rat round spermatids regulate pHi by means of a V‐type H+‐ATPase, a HCO 3 − entry pathway, a Na+ HCO3−dependent transport system, and a putative proton conductive pathway. Rat spermatids do not have functional base extruder transport systems. These pH regulatory characteristics seem specially designed to withstand acid challenges, and can generate sustained alkalinization upon acid exit stimulation.
Water transport across plant tissue: Role of water channels
Authors: Steudle Ernst
Published: February 2012

Summary— The contribution of water‐filled, selective membrane pores (water channels) is integrated into a general concept of water transport in plant tissue. The concept is based on the composite anatomical structure of tissues which results in a composite transport pattern. Three main pathways of water flow have been distinguished, ie the apoplastic, symplastic and transcellular (vacuolar) paths. Since the symplastic and transcellular components can not be distinguished experimentally, these components are summarized as a cell‐to‐cell component. Water channel activity may control the overall water flow across tissues provided that the contribution of the apoplastic component is relatively low. The composite transport model has been applied to roots where most of the data are available. Comparison of the hydraulic conductivity at the root cell and organ levels shows that, depending on the species, there may be a dominating cell‐to‐cell or apoplastic water flow. Most remarkably, there are differences in the hydraulic conductivity of roots which depend on the nature of the force used to drive water flows (osmotic or hydrostatic pressure gradients). This is predicted by the model. The composite transport model explains low reflection coefficients of roots, the variability in root hydraulic resistance and differences between herbaceous and woody species. It is demonstrated that there is also a composite transport of water at the membrane level (water channel arrays vs bilayer arrays). This results in low reflection coefficients of plasma membranes for certain test solutes as derived for isolated internodes of Chara. The titration of water channel activity in this alga with mercurials and its dependence on changes in temperature or external concentration show that water channels do not exclusively transport water. Rather, they are permeable to relatively big uncharged organic solutes. The result indicates that, at least for Chara, the concept of an exclusive transport of water across water channels has to be questioned.
Water transport by the Na+/glucose cotransporter under isotonic conditions Proceedings of a meeting held in Paris, 27–30 April, 1997, as a tribute to Jacques Bourguet.*
Authors: Zeuthen Thomas , Meinild Anne‐Kristine , Klaerke Dan A , Loo Donald DF , Wright Ernest M , Belhage Bo , Litman Thomas
Published: February 2012

Solute cotransport in the Na+glucose cotransporter is directly coupled to significant water fluxes. The water fluxes are energized by the downhill fluxes of the other substrates by a mechanism within the protein itself. In the present paper we investigate the Na+glucose cotransporter expressed in Xenopus oocytes. We present a method which allows short‐term exposures to sugar under voltage clamp conditions. We demonstrate that water is cotransported with the solutes despite no osmotic differences between the external and intracellular solutions. There is a fixed ratio of 195:1 between the number of water molecules and the number of Na+ ions transported, equivalent to 390 water molecules per glucose molecule. Unstirred layer effects are ruled out on the basis of experiments on native oocytes incubated with the ionophores gramicidin D or nystatin.
Expression of aquaporin‐1 (AQP1) in the adult and developing sheep kidney
Authors: Butkus Aldona , Alcorn Daine , Earnest Linda , Moritz Karen , Giles Michelle , Wintour E Marelyn
Published: February 2012

The distributions of aquaporin‐1 mRNA and protein were studied by hybridization histochemistry with a homologous riboprobe and immunohistochemistry, in the adult sheep kidney. Heaviest labelling occurred in the thin descending limb (DTL) of the loop of Henle in the inner stripe of the outer medulla, with apparent decreasing expression in the inner medulla, outer stripe of the outer medulla and cortex, but no quantitation was performed. Only proximal tubules (PT) (convoluted and straight) and DTL labelled. The glomerulus showed no labelling, consistent with the pattern in the rat but different to that in the human. During ontogeny, no labelling occurred in the mesonephros at 27 or 41 days of gestation (term = 145–150 days) but other structures did label at 27 days (heart, lung bud, blood vessels surrounding developing spinal cord). Labelling first occurred faintly in the metanephros at 41 days of gestation and increased throughout gestation consistent with morphological development of nephrons.
Photic regulation of pineal function. Analogies between retinal and pineal photoreception
Authors: Meissi Hilmar
Published: February 2012

Light absorbed by a photopigment in a photoreceptor cell causes a photochemical reaction converting the 11‐cis retinal chromophore into the all‐trans configuration. These changes lead to a series of events that causes cGMP hydrolysis, a following decrease of cGMP in the cytoplasm of the photoreceptor outer segment and a closure of cGMP‐gated cationic channels. As a consequence of these processes the membrane hyperpolarizes. In pineal photoreceptor cells of lower vertebrates these processes are only partly investigated. Molecules involved in the phototransduction process and the desensitization, like opsin, vitamin A, α‐transducin and arrestin, have been immunocytochemically localized in pineal photoreceptors and also electrophysiological studies have shown that phototransduction mechanisms in pineal photoreceptors might be very similar to those found in retinal photoreceptors. This review will summarize some of the current knowledge on pineal photoreception and compare it with retinal processes.
Peptidergic cells in the mammalian pineal gland. Morphological indications for a paracrine regulation of the pinealocyte
Authors: Møller Morten
Published: February 2012

Several neuropeptides are present in the mammalian pineal gland. Most of these peptides, eg neuropeptide Y, vasoactive intestinal peptide, and peptide histidine isoleucine, are located in nerve fibres innervating the gland. In some mammalian species, neuropeptides are also found in cells scattered in the pineal parenchyma. In the rat, bipolar cells immunoreactive for somatostatin are present, just as cells containing mRNA encoding somatostatin can be detected in the gland by in situ hybridisation. In the pineal gland of the European hamster, many cells are immunoreactive for enkephalin. Ultrastructural cytochemical analysis of these cells reveals a pinealocyte morphology. Processes from the opioidergic pinealocytes terminate in the parenchyma between the non‐immunoreactive pinealocytes. Some of the processes contain small clear and large dense core vesicles and end in club shaped swellings which make synapse‐like contacts with other pinealocytes. The ultrastructural morphology suggests that the opioidergic cells exert a paracrine regulation on other pinealocytes.
How do the suprachiasmatic nuclei of the hypothalamus integrate photoperiodic information?
Authors: Pévet Paul , Jacob Nathalie , Lakhdar‐Ghazal Nouria , Vuillez Patrick
Published: February 2012

The suprachiasmatic nucleus of the hypothalamus (SCN) plays an essential role in the generation and maintenance of circadian rhythms in mammals. The SCN activity is also dependent upon the photoperiod. The duration of the SCN sensitive phase to light, in term of Fos induction, is variable and tied to the length of the night. The question is how and by which pathways can photoperiod influence SCN? It is possible following the theoretical model of evening and morning component of the clock that the SCN build itself the photoperiodic signal. That the SCN integrate the photoperiodic information through indirect neural or neuroendocrine pathways is also to consider. Data in favor of these different interpretations are presented.
Intracellular Ca2+ homeostasis in rat round spermatids
Authors: Berrios Julio , Osses Nelson , Opazo Carlos , Arenas Gloria , Mercado Luis , Benos Dale J , Reyes Juan G
Published: February 2012

Intracellular calcium, [Ca2+]i, can regulate meiotic progression of mammalian oocytes. However, the role of [Ca2+]i in the regulation of the spermatogenic process and its cellular homeostatic mechanisms in spermatogenic cells has not been elucidated. Using intracellular fluorescent probes for Ca2+ and immunodetection of plasma membrane (PM) Ca2+‐ATPases, we report that: a) rat round spermatids maintain [Ca2+]i levels of 60 ± 5 nM (SEM), as estimated with fluo‐3 in single cells or fura‐2 in cells in suspension; b) these cells regulate [Ca2+]i by actively extruding it using a PM Ca2+‐ATPase; c) rat spermatids also actively transport Ca2+ by sarco‐endoplasmic reticulum type ATPases (SERCA); d) rat spermatids possess non‐mitochondrial intracellular Ca2+i stores insensitive to thapsigargin but releasable by ionomycin; and e) rat spermatids do not activate Ca2+ entry mechanisms by the release of Ca2+ from SERCA‐regulated stores. These results demonstrate that rat round spermatids can generate modulated intracellular Ca2+ signals upon activation of Ca2+ channels or Ca2+ release from intracellular stores.
Expression of melatonin synthesis genes is controlled by a circadian clock in the pike pineal organ but not in the trout
Authors: Coon Steven L , Bégay Valérie , Falcón Jack , Klein David C
Published: February 2012

The photosensitive teleost pineal organ exhibits a daily rhythm in melatonin production. In most teleosts, including the pike, this is driven by an endogenous pineal clock. An exception is the trout, in which the pineal melatonin rhythm is a direct response to darkness. This fundamental difference in the regulation of melatonin production in two closely related species provides investigators a novel opportunity to study the molecular mechanisms of vertebrate clock function. We have studied the circadian regulation of mRNA encoding two melatonin synthesis enzymes by Northern blot analysis. These two enzymes are serotonin N‐acetyltransferase (AA‐NAT), the penultimate enzyme in melatonin synthesis, and tryptophan hydroxylase (TPH), the first enzyme in melatonin synthesis. A clock controls expression of both AA‐NAT and TPH mRNAs in the pineal organ of pike, but not that of trout, in which the levels of these mRNAs are tonically elevated. A parsimoneous explanation of this is that a single circadian system regulates the expression of both AA‐NAT and TPH genes in most teleosts, and that in trout this system has been disrupted, perhaps by a single mutation.
Yoshio Masui and cell cycle control, past, present and future
Authors: Nurse Paul
Published: February 2012

Yoshio Masui is a gentle, modest traditional biologist whose contributions have had a major influence on the recent advances that have taken place in understanding how the cell cycle is controlled. His work forms part of a long tradition of experimental zoologists beginning at the end of the last century, who have studied the process of cell division and its control. In this essay I want to place Yoshio Masui's contributions in perspective, as the successor to these early experimentalists, and as the forerunner of the molecular biologists now working on cell cycle control. For a fuller treatment of much of the same historical material, I recommend Yoshio Masui's own scholarly review (Masui (1992) Biochem Cell Biol 70, 920–945). After this I will briefly summarise the central role of cyclin dependent kinases (CDK's) in controlling the cell cycle, following Yoshio Masui's own example by emphasising their biological significance. Finally I will sketch out some of the unsolved problems of the future in this area of research as I see them.
Behavior of cyclin B and cyclin B‐dependent kinase during starfish oocyte meiosis reinitiation: Evidence for non‐identity with MPF
Authors: Picard André , Peaucellier Gérard
Published: February 2012

We reconsider the notion of MPF initiation, which is generally viewed as the prerequisite production of a small cdc2‐cyclin B kinase activity sufficient to trigger its own self‐amplification. Using starfish oocytes as a tool, we show that H1 kinase activation is not explosive, but rather is a gradual process in both time and space. We show further that the production of even a large H1 kinase activity, either in MPF‐microinjected or in hormone‐stimulated oocytes, is not sufficient to trigger MPF amplification.
Autonomous activation of histone H1 kinase, cortical activity and microtubule organization in one‐ and two‐cell mouse embryos
Authors: Ciemerych Maria A , Tarkowski Andrzej K , Kubiak Jacek Z
Published: February 2012

The activation of M‐phase promoting factor (MPF) in one‐cell mouse embryo is independent from the nucleus. Other autonomous phenomena include the cortical activity observed at the end of the first cell cycle and the reorganization of the microtubule network. Here, we observed that the autonomous control of MPF activation is present also in two‐cell mouse embryos (H1 kinase activity being higher in the first than in the second cell cycle). Moreover, the disappearance of the cortical activity in anucleated halves is observed when MPF activation takes place. The rounding up of the cytoplast and the mitotic reorganization of the microtubule network correlates with the maximum activity of H1 kinase in anucleated halves from one‐cell embryos. In anucleated halves of two‐cell stage blastomeres neither the cortical activity nor the microtubule reorganization were observed. The degree of activation of histone H1 kinase, and, as a consequence, the cortical activity and the microtubule reorganization, does not depend on the distribution of cyclin B. Finally, the level of cyclin B synthesis is similar in anucleated and nucleated halves derived from both one‐and two‐cell embryos.
Mos‐induced p42 mitogen‐activated protein kinase activation stabilizes M‐phase in Xenopus egg extracts after cyclin destruction
Authors: Chau Andrew SS , Shibuya Ellen K
Published: February 2012

Previously, we have shown that the addition of a constitutively‐active mitogen‐activated protein kinase kinase protein (MAPKK = MEK) to cycling Xenopus egg extracts activates the p42MAPK pathway, leading to a G2 or M‐phase cell cycle arrest. The stage of the arrest depends on the timing of p42MAPK activation. If p42MAPK is activated prior to M‐phase, or after exit from M‐phase, the extract is arrested in G2. If p42MAPK is activated during entry into M‐phase, the extract is arrested in M‐phase. In this study, we show that the addition of recombinant Mos protein (which directly phosphorylates and activates MEK) to cycling egg extracts has the same effect as those described for MEK. The addition of Mos to the extract at the start of incubation leads to a G2 arrest with large interphase nuclei with intact nuclear envelopes. If Mos is added at later times, however, the activation of p42MAPK leads to an M‐phase arrest with condensed chromosomes and mitotic arrays of microtubules. Moreover, the extent of M‐phase specific phosphorylations is shown by the sustained presence of phosphoproteins that are detected by the monoclonal antibody MPM‐2. Unexpectedly, in certain M‐phase arrested extracts, histone H1 kinase activity levels reach a peak on entry into M‐phase but then fall abruptly to interphase levels. When these extracts are analyzed by immunoblotting, Cyclin B2 is destroyed in those samples containing low maturation promoting factor activity (MPF, cyclin B/Cdc2), yet chromosomes remain condensed with associated mitotic arrays of microtubules and M‐phase‐specific phosphorylations are sustained. These results suggest that although MPF is required for entry into M‐phase, once established, M‐phase can be maintained by the p42MAPK pathway after the proteolysis of mitotic cyclins.
The legacy of lithium effects on development
Authors: Kao Kenneth R , Elinson Richard P
Published: February 2012

The simple element lithium causes specific effects on early embryonic development. In amphibians, treatment during early cleavage enhances anterior and dorsal development at the expense of posterior and ventral development. Conversely, treatment at late cleavage reduces head development. While an effect of lithium on the phosphoinositide cycle was suspected, the enhancement of dorsoanterior development is now thought to result primarily from stimulation of the Wnt/β‐catenin pathway. The multiple uses of this pathway in development may account for lithium's various specific effects.
P‐glycoprotein subcellular localization and cell morphotype in MDR1 gene‐transfected human osteosarcoma cells
Authors: Maraldi Nadir M , Zini Nicoletta , Santi Spartaco , Scotlandi Katia , Serra Massimo , Baldini Nicola
Published: February 2012

Efflux of chemotherapy agents by P‐glycoprotein at the plasma membrane is thought to be a major cause of cancer multidrug‐resistance (MDR). However, the mechanism underlying the cellular accumulation and distribution of cytotoxic drugs is still poorly defined. We have recently found that P‐glycoprotein is expressed also in the nucleus of MDR cell lines selected in doxorubicin (DXR), suggesting the possible involvement of this protein in the direct extrusion of the drug from the nucleus of resistant cells. In this study, we analyzed the subcellular localization of P‐glycoprotein in a series of U‐2 OS osteosarcoma cell clones transfected with MDR1 gene in order to verify whether the nucleus is a constant site for the localization and functional activity of P‐glycoprotein, and in which way some aspects of cell morphology related to MDR depend on the subcellular P‐glycoprotein localization rather than on the exposure to the selective drug. Our results indicate that to achieve a subcellular drug distribution prevailing in the cytoplasm but not in the nucleus, a significant increase in the expression of P‐glycoprotein at the different cellular compartments, including the plasma membrane, the cytoplasm, and the nucleus, is needed, although the in vitro drug resistance appears to be mainly dependent on the expression of P‐glycoprotein at the cell surface. With regard to the morphological characteristics of MDR cells involving the cell surface and the chromatin arrangement, the influence of DXR appears to be prevalent, although P‐glycoprotein overexpression cannot be excluded.
The motility of human spermatozoa as influenced by prostasomes at various pH levels
Authors: Arienti Giuseppe , Carlini Enrico , Nicolucci Annalisa , Cosmi Ermelando Vinicio , Santi Fernando , Palmerini Carlo Alberto
Published: February 2012

Human semen contains several components among which spermatozoa, membranous vesicles called ‘prostasomes’, secreted by the prostate gland and unorganized material. Prostasomes possess an unusual lipid composition, contain a number of proteins and small molecules and have been claimed to take a part in the immune response, in seminal fluid liquefaction and in sperm motility. Since sperm may come in contact with an acidic environment in the vagina, it may be of some interest to know whether prostasomes may affect spermatozoon motility or may protect spermatozoa upon the exposure to an acidic milieu. Human semen was supplied by donors. From whole semen we collected spermatozoa by centrifugation and used the supernatant to prepare prostasomes (centrifugation at 105000 g for 120 min, followed by purification step on Sephadex G 200); spermatozoa were then collected by a swim‐up procedure and exposed to an acidic pH medium (from 5 to 7) in the presence or absence of prostasomes. Spermatozoa motility was subsequently assessed with a superimposed image analysis system (SIAS). Results indicate that the motility of spermatozoa was affected by the pH value of the medium. Acidic media reduced the percentage of motile cells and decreased the straight line velocity of spermatozoa (VLS). Prostasomes had a protective effect and increased the percentage of motile cells. However, they did not change the characteristics of motility (curvilinear and straight). Prostasomes may be considered as a system for counteracting the negative effects of acidic pH values that may be present in the vagina after coitus.
Centrosomal and non‐centrosomal microtubules
Authors: Keating Thomas J , Borisy Gary G
Published: February 2012

While microtubule (MT) arrays in cells are often focused at the centrosome, a variety of cell types contain a substantial number of non‐centrosomal MTs. Epithelial cells, neurons, and muscle cells all contain arrays of non‐centrosomal MTs that are critical for these cells' specialized functions. There are several routes by which non‐centrosomal MTs can arise, including release from the centrosome, cytoplasmic assembly, breakage or severing, and stabilization from non‐centrosomal sites. Once formed, MTs that are not tethered to the centrosome must be organized, which can be accomplished by means of self‐organization or by capture and nucleation of MTs where they are needed. The presence of free MTs requires stabilization of minus ends, either by MT‐associated proteins or by an end‐capping complex. Although some of the basic elements of free MT formation and organization are beginning to be understood, a great deal of work is still necessary before we have a complete picture of how non‐centrosomal MT arrays are assembled in specific cell types.
Microtubule release and capture in epithelial cells
Authors: Mogensen Mette M
Published: February 2012

Many differentiated cells including polarised epithelial cells display a non‐radial, apico‐basal microtubule array. In some cells the centrosome disassembles and new nucleating sites are created at more appropriate locations. In others the centrosome remains, but relatively few microtubules radiate from it's immediate environs. Instead, the majority of the microtubule minus‐ends are associated with apical cell surface sites. Centrosomal microtubule release and capture is evidently a mechanism exploited by some polarised epithelial cells as a means of producing non‐centrosomal, apico‐basal microtubule arrays. This involves microtubule nucleation at the centrosome, release and subsequent translocation and capture at the apical sites. Two functionally distinct centrosomal complexes dedicated to the control of microtubule nucleation and anchorage have been suggested to be essential and universal features of all centrosomes. The centrosomal proteins ninein and R2 are potential microtubule anchoring proteins and their discovery has exciting implications for centrosomal organisation and microtubule positioning in cells.
Control of centrosome reproduction: The right number at the right time
Authors: Sluder Greenfield , Hinchcliffe Edward H
Published: February 2012

It is of great importance for the cell to precisely coordinate the doubling of the interphase centrosome with nuclear events during the cell cycle and limit the number of centrosomes it contains at the onset of mitosis to two and only two. The penalties for mistakes are abnormal spindle assembly, inappropriate chromosome distribution, and consequently, genomic instability. We review the functional properties of the mechanisms that control when the centrosome duplicates in the cell cycle and the controls for centrosome copy number. We look to limits that are intrinsic to the centrosome itself and controls imposed by cell cycle linked changes in cytoplasmic conditions. Control of centrosome reproduction is exercised at both levels.
Identification and function of the centrosome centromatrix
Authors: Schnackenberg Bradley J , Palazzo Robert E
Published: February 2012

Centrosomes direct the organization of microtubules in animal cells. However, in the absence of centrosomes, cytoplasm has the potential to organize microtubules and assemble complex structures such as anastral spindles. During cell replication or following fertilization, centrioles that are incapable of organizing microtubules into astral arrays are introduced into this complex cytoplasmic environment. These centrioles become associated with pericentriolar material responsible for centrosome‐dependent microtubule nucleation, and thus the centrosome matures to ultimately become a dominant microtubule organizing center that serves as a central organizer of cell cytoplasm. We describe the identification of a novel structure within the pericentriolar material of centrosomes called the centromatrix. The centromatrix is a salt‐insoluble filamentous scaffold to which subunit structures that are necessary for microtubule nucleation and abundant in the cytoplasm bind. We propose that the centromatrix serves to concentrate and focus these subunits to form the microtubule organizing center. Since binding of these subunits to the centromatrix does not require nucleotides, we propose a model for centrosome assembly which predicts that the assembly of the centromatrix is a rate‐limiting step in centrosome assembly and maturation.
Mechanisms of genetic instability revealed by analysis of yeast spindle pole body duplication
Authors: Chial Heidi J , Winey Mark
Published: February 2012

Aneuploidy and polyploidy are commonly observed in transformed cells. These states arise from failures during mitotic chromosome segregation, some of which can be traced to defects in the function or duplication of the centrosome. The centrosome is the organizing center for the mitotic spindle, and the equivalent organelle in the budding yeast, Saccharomyces cerevisiae, is the spindle pole body. We review how defects in spindle pole body duplication or function lead to genetic instability in yeast. There are several well documented instances of genetic instability in yeast that can be traced to the spindle pole body, all of which serve as models for genetic instability in transformed cells.
Connection of vulval and uterine epithelia in Caenorhabditis elegans
Authors: Delattre Marie , Félix Marie‐Anne
Published: February 2012

In the Caenorhabditis elegans hermaphrodite, the establishment of the egg‐laying system requires the connection of two epithelial tubes: the uterus of the gonad and the vulva in the underlying ectoderm. A specialized uterine cell, the anchor cell (AC), plays a central role in specifying the fates of the uterine and vulval precursor cells via the EGF‐Ras‐MAP kinase and the Notch/Delta signaling pathways. This central and common inducing source ensures that the two sets of cells are in register and it specifies the cell types that build the T‐shaped connection between uterus and vulva. On either side, progeny of the induced cells form lumen structures and undergo stereotyped cell‐to‐cell fusion, thereby building epithelial tubes. Finally, the anchor cell fuses with a uterine syncytium and thus leaves only a thin cellular process between the lumen of the uterus and the vulva. In the adult, the fertilized eggs exit the lumen of the uterus through the vulva. This relatively simple developmental process serves as a model to study the biology of cells during organogenesis, such as intercellular signaling, cell polarity, invasion of basal laminae and epithelia, cell recognition and cell fusion. The anchor cell is a particularly interesting cell as it coordinates the development of its neighboring cells by using different signaling pathways at different times.
In vivo localisation of the mitotic POLO kinase shows a highly dynamic association with the mitotic apparatus during early embryogenesis in Drosophila
Authors: Moutinho‐Santos Tatiana , Sampaio Paula , Amorim Isabel , Costa Madalena , Sunkel Claudio E
Published: February 2012

The gene polo encodes a highly conserved serine/threonine protein kinase that has been implicated in several functions during cell division. Polo‐like kinases are important positive regulators of cell cycle progression and have also been implicated in the exit from mitosis through the activation of the anaphase‐promoting complex. Several data indicate that Plks are required for centrosome function, bipolar spindle organisation and cytokinesis. The intracellular localisation of Plks reflects their multiple roles in cell division, however, in vivo studies that describe the distribution of this protein during different stages of mitosis have never been performed. In the present work, we report the in vivo distribution of a GFP‐POLO fusion protein expressed in stable transformants and analysed during the early embryonic development of Drosophila melanogaster. The GFP‐POLO protein can be detected in unfertilised oocytes associated with the centromeric region of chromosomes of the polar body and followed until the formation of mitotic domains in later development. Detailed analysis of the dynamic localisation of GFP‐POLO during syncytial mitotic cycles shows the timing of localisation to the centrosomes, centromeres and midbody. The results also indicate that GFP‐POLO is present in astral microtubules early in mitosis, accumulates around the nuclear envelope until nuclear envelop breakdown and at metaphase associates to spindle microtubules. These in vivo studies show a highly dynamic association of POLO with multiple compartments of the mitotic apparatus. Furthermore, the wide distribution of the GFP‐POLO protein to all compartments of the mitotic apparatus provides a valuable tool for future studies on cell cycle during development.
Double‐Masked, Placebo‐Controlled Study of Intravenous Levetiracetam for the Treatment of Status Epilepticus and Acute Repetitive Seizures in Dogs
Authors: Hardy B.T. , Patterson E. E. , Cloyd J.M. , Hardy R.M. , Leppik I.E.
Published: February 2012

Background

Status epilepticus (SE) and acute repetitive seizures (ARS) are common canine neurologic emergencies. No evidence‐based studies are available to guide treatment in veterinary patients. Parenteral levetiracetam (LEV) has many favorable properties for the emergency treatment of seizures, but its safety and efficacy in dogs forSEandARSare unknown.

Hypothesis

IntravenousLEVis superior to placebo in controlling seizures in dogs withSEorARSafter treatment withIVdiazepam.

Animals

Nineteen client‐owned dogs admitted forSEorARS.

Methods

Randomized, placebo‐controlled, double‐masked study. Dogs withSEorARSwere randomized to receiveIV LEV(30 or 60 mg/kg using an adaptive dose‐escalation approach) or placebo, in addition to standard of care treatment. They were monitored for at least 24 hours after admission for additional seizures.

Results

The responder rate (defined as dogs with no additional seizures after administration of the study medication) afterLEVwas 56% compared with 10% for placebo (P = .06). Dogs in the placebo group required significantly more boluses of diazepam compared with theLEVgroup (P < .03). Seizure etiologies identified were idiopathic epilepsy (n = 10), inflammatory central nervous system disease (n = 4), intracranial neoplasia (n = 2), hepatic encephalopathy (n = 1), and 2 dogs had no cause determined. No serious adverse effects were attributable toLEVadministration.

Conclusions and Clinical Importance

LEVwas safe and potentially effective for the treatment ofSEandARSin these client‐owned dogs. Larger, controlled clinical trials are needed to confirm this preliminary observation.
Hannah's Prior Knowledge About Chemicals: A Case Study of One Fourth‐Grade Child
Authors: Bretz Stacey Lowery , Emenike Mary Elizabeth
Published: February 2012

Chemical principles are taught in elementary education across much of the United States because the National Science Education Standards include concepts about the nature of matter, states of matter, and changes in matter among other science concepts within the first to fifth grade levels. “Chemicals” is a word related to the nature of matter that is used not only in formal instruction, but also in everyday conversations. Children's prior knowledge about chemicals gained from everyday experiences will influence how they learn about chemical principles. The research described herein reveals insights into one child's conceptual structure related to the word “chemical,” which includes how she uses the word both inside and outside of school. Hannah was purposefully chosen for this case study because she exemplified “children's science.” Her understanding of chemicals as cleaners, in foods, and used for a purpose were primarily gained from everyday experiences. The implications of these findings are discussed with respect to both future research and elementary science education.