bluuebunny/crossref_metadata_2025 huggingface dataset:
Genomic arrangement of repeated PS700 elements in the nematode Panagrellus silusiae
Authors: Retterath M. A. , Pasternak J. J.
Published: October 2017

When genomic DNA from the free-living nematode Panagrellus silusiae is digested with the restriction endonuclease BamHI and separated by electrophoresis, a band in the 700 base pair size range is evident after ethidium bromide staining. One of the 0.7-kilobase fragments (PS700-1) was characterized and found to be a member of a moderately repetitive DNA family (T. Warren and J.J. Pasternak. 1988. Nucleic Acids Res. 16: 10 833 – 10 847). In the current study, DNA sequence analyses of three independently isolated copies of the PS700 DNA family showed the same nucleotide sequence and >98% similarity to PS700-1. Four EMBL-4 bacteriophage clones were isolated from a Panagrellus genomic DNA library with PS700-1 as the probe and were analyzed by restriction endonuclease site mapping and Southern blot DNA hybridization. These clones contain 31 copies of the PS700 DNA family. In each case, the units are arranged in head-to-tail arrays. One of the EMBL-4 clones contains copies of a novel variant of the PS700 elements. The maintenance of both nucleotide sequence and restriction endonuclease restriction site homogeneity among members of the dispersed PS700 DNA family may denote a functional role for these sequences.Key words: nematode, Panagrellus, repetitive DNA organization, nucleotide sequence variation.
Meiotic crossing-over between sites on opposite sides of the centromeres of homoeologues is frequent in hybrid Aloeaceae
Authors: Brandham P. E.
Published: October 2017

During meiosis, long and short arms of acrocentric homoeologues pair and cross over in the centromere region in 95 (66.9%) of 142 hybrids of differing parentage in the monocotyledon family Aloeaceae. A characteristic configuration, the L–S bridge, is produced at anaphase I with frequencies ranging from <1 to 48% of pollen mother cells and in up to three bivalents per pollen mother cell. Too frequent to be due to inversion hybridity, L–S crossing-over most probably results from straight, noninverted pairing between nonhomologous proximal segments of the long and short chromosome arms following centromere mismatching in the heteromorphic bivalents. It is suggested that there are several lengths of DNA in different regions of homoeologous chromosomes, but perhaps concentrated around the centromere, that are sufficiently similar to recognize each other, pair, and cross over when brought together in a heteromorphic bivalent with mismatching of centromeres.Key words: Aloeaceae, hybrid, meiosis, nonhomologous pairing, crossing-over.
Somaclonal variation from cultured immature embryos of sister lines of rye differing in heterochromatic content
Authors: Bebeli P. J. , Karp A. , Kalts1kes P. J.
Published: October 2017

Somaclonal variation occurred among rye plants regenerated from cultured immature embryos of five sister lines that differed in their content of telomeric heterochromatin. Variation was observed in morphology, chromosome number, and secalin seed storage proteins. Morphological variation was present in 9.7% of the regenerants and included albinism and variegation, which appeared in different frequencies among the lines. Chromosome variation occurred in 15.8% of the regenerants and included translocations, tetraploidy, and trisomy in addition to meiotic disturbances such as centromere misbehaviour and asyndesis. Some of the regenerated plants were mosaic for the structural and numerical chromosome aberrations. The nature of the chromosome variation also differed among the lines. A single variant in the 40K γ-secalins was detected. The occurrence of variation is discussed in relation to differences in morphogenetic response of the rye lines and to the genotypic component of instability in culture.Key words: somaclonal variation, immature embryo culture, rye heterochromatin, chromosome variation, secalins.
Polytene chromosome maps in the Medfly Ceratitis capitata
Authors: Zacharopoulou A.
Published: October 2017

Polytene chromosome maps of the five autosomes from salivary gland cells in Ceratitis capitata are presented, and the more characteristic features of each element are described. The correlation of the polytene elements to miotic chromosomes and linkage groups is established by using various Y-autosome and autosome-autosome translocation lines. Two loci, dp (black pupal case) and w (white pupal case), are mapped to the third and fifth chromosome, respectively. In addition to the polytene maps presented, some extra figures of specific chromosomal regions are given for easier identification of each polytene element.Key words: polytene chromosome maps, Ceratitis capitata.
Inheritance of resistance to Puccinia coronata avenae and P. graminis avenae in an accession of Avena sterilis from Spain
Authors: Harder D. E. , Chong J. , Brown P. D. , Martens J. W.
Published: October 2017

Accessions of wild Avena spp. obtained from the Iberian Peninsula were screened for resistance to oat crown and oat stem rust. Of a number of accessions which showed resistance, A. sterilis accession IB3056 was selected for further genetic analysis because it had combined resistance to both crown and stem rusts and as a hexaploid was readily hybridizable with A. sativa. IB3056 was crossed and backcrossed with the susceptible cultivar 'Makuru' and progeny were analyzed for segregation to a range of rust races. A single dominant gene conferred resistance to crown rust. The resistance was highly effective against all isolates of Puccinia coronata avenae tested. The crown rust resistance of IB3056 was due either to gene Pc68 or was very closely linked or allelic to Pc68. Seedling plants of the IB3056 parent were susceptible to all isolates of P. graminis avenae tested, but in the adult plant stage they were resistant. All IB3056/2* Makuru progeny also were susceptible to stem rust as seedlings, but BC1F2 adult plants segregated for resistance in ratios indicating a single dominant gene, designated Pg17.Key words: oat crown rust, oat stem rust, adult plant resistance, seedling resistance
Genetic location and biochemical characterization of eye-colour mutants from natural populations of Drosophila melanogaster
Authors: Aparisi M. Luisa , Nájera Carmen
Published: October 2017

From six captures of Drosophila melanogaster carried out in three different habitats (cellar, vineyard, and pinewood) in two different seasons of the year (spring and autumn), 60 eye-colour mutations were isolated, which were reduced to 29 loci by means of allelism tests within and between populations. Forty-five of these mutations were analyzed genetically and biochemically; of these 33 turned out to be previously described mutants and mapped to a total of 17 loci. Twelve new mutants were discovered and they mapped to 12 new loci, distributed on chromosomes X, II, and III. The eye-colour mutants show large effects on the red and brown pigments. The high variability of the eye-colour loci is discussed in relation to the mutation and selection hypotheses.Key words: eye-colour mutants, variability, mapping, Drosophila melanogaster, pigment patterns.
Extensive multivalent pairing occurs in male lake trout meiosis
Authors: Disney Jane E. , Wright Jr. James E.
Published: October 2017

Extensive multivalent pairing was observed in the tetraploid derivative lake trout (Salvelinus namaycush). In conjunction with previously reported hybrid splake (brook × lake) trout data, this result supports a meiotic model to explain the phenomenon of pseudolinkage. In addition, C-banding of mitotic and meiotic lake trout chromosomes revealed an intraindividual polymorphism for a Robertsonian fusion. Silver staining of lake trout chromosomes showed that the chromosomes with active nucleolar organizer regions located proximal to a centromere were not involved in the fusion event.Key words: lake trout, mitosis, C-banding, nucleolar organizer regions, intraindividual Robertsonian polymorphism, meiosis.
The genetics of resistance of hexaploid wheat to the wheatgrass powdery mildew fungus
Authors: Tosa Y. , Sakai K.
Published: October 2017

The avirulence of Erysiphe graminis f.sp. agropyri, Ak-1, on Triticum aestivum 'Norin 4' and 'Norin 10' and T. compactum 'No.44' is conditioned by four genes; three operate singly against each cultivar and one operates against all three cultivars. If the forma specialis – genus specificity follows the gene-for-gene relationship, four major genes should be involved in the resistance of the three cultivars to Ak-1, one carried only by 'Norin 4', one carried only by 'No.44', one carried only by 'Norin 10', and one carried by all three cultivars. The first and second genes were considered to be the previously reported genes Pm10 and Pm11, respectively. The third and fourth genes were successfully detected using F1 hybrid cultures between Ak-1 and E. graminis f.sp. tritici, Tk-1. They were located on chromosomes 6B and 7D and designated Pm14 and Pm15, respectively. These results strongly support the assumption that the forma specialis – genus specificity follows the gene-for-gene relationship. It is, therefore, concluded that this type of specificity belongs to cultivar specificity rather than plant-species specificity and that the resistance to inappropriate formae speciales is essentially cultivar resistance and not nonhost resistance.Key words: powdery mildew, Erysiphe graminis, wheat, wheatgrass, resistance.
Operation of resistance genes in wheat to Erysiphe graminis f.sp. tritici against E. graminis f.sp. agropyri
Authors: Tosa Y. , Tada S.
Published: October 2017

The common wheat cultivar 'Chancellor' and its near-isogenic lines carrying resistance genes to Erysiphe graminis f.sp. tritici were inoculated with 240 F1 cultures derived from a cross between E. graminis f.sp. agropyri, Ak-1, and E. graminis f.sp. tritici, Tk-1. Segregation patterns of avirulent and virulent cultures suggested that the F1 population carries avirulence genes corresponding to Pm1, Pm2, Pm3a, and Pm3b. These avirulence genes were considered to be derived from Ak-1. It was therefore concluded that Pm1, Pm2, Pm3a, and Pm3b, resistance genes to E. graminis f.sp. tritici, operate against E. graminis f.sp. agropyri.Key words: powdery mildew, Erysiphe graminis, resistance, wheat, wheatgrass.
Growth hormone restriction fragment length polymorphisms that segregate with 42-day live weight of mice
Authors: Winkelmann Dianne C. , Querengesser Laura D. , Hodgetts Ross B.
Published: October 2017

The known correlation between growth hormone levels and growth rate in a number of species prompted us to examine if polymorphic restriction fragment alleles at the growth hormone locus in mice might be associated with differentiable rates of growth. An F2 population of mice was generated from crosses between a line selected for high 42-day weight and an unselected control line. The original selected and control lines exhibited mean 42-day weights of 30.6 ± 3.8 and 20.5 ± 2.6 g, respectively. Since the two lines also differed with respect to the restriction fragments detected by hybridization to a rat growth hormone cDNA probe, an analysis of the F2 generation was carried out to determine whether this polymorphism could be considered a quantitative trait locus for 42-day weight. The results of the analysis indicated that a polymorphic HindIII restriction fragment was correlated (P < 0.05) with 42-day weight. However, the allele that was positively correlated with weight was the one that was fixed in the original control line, rather than the one from the selected line. While these findings support the potential use of restriction fragment length polymorphisms in quantitative trait evaluation of livestock, they also emphasize the requirement for testing such potential quantitative trait loci in the appropriate genetic background.Key words: mice, growth rate, quantitative trait loci, restriction fragment length polymorphism.
Relative abundance of various rDNA repeat types in polytene nuclei of Drosophila melanogaster
Authors: Kalumuck Karen E. , Wetzel F. Liebchen , Procunier James D.
Published: October 2017

The relative abundance of the five predominant X chromosome nucleolus organizer repeat types was determined in polytene nuclei. Previous studies showed that the major type I insert containing class of repeats was disproportionately underreplicated when compared with the insert-free class of repeats in these nuclei. Our results demonstrate that this disproportionate underreplication also occurs for both the minor type I and type II insert containing repeats. There was not an exclusive polytenization of the insert-free repeats for this wild-type X nucleolus organizer region. A repeat type lacking either insert type and having an unusually long nonstrancribed spacer was identified and found to be preferentially replicated in polytene nuclei. Preliminary mapping studies indicate that this class of repeats has a unique location, in the distal portion of either the X nucleolus organizer region or the centric heterochromatin. Their similarity to the common insert-free repeats includes preferential polytenization and generalized DNase I sensitivity, which suggests that they are transcriptionally active.Key words: Drosophila melanogaster, rDNA polytenization.
Identification of loci on chromosome 5A of wheat involved in control of cold hardiness, vernalization, leaf length, rosette growth habit, and height of hardened plants
Authors: Roberts D. W. A.
Published: October 2017

The offspring from crosses of 'Cadet' by 'Cadet – Rescue 5A' and 'Winalta' by 'Winalta – Rescue 5A' were studied to obtain information on the inheritance of cold hardiness, winter–spring growth habit, rosette growth habit, height of cold-hardened plants, and length of leaves of hardened plants. The results indicate that a minimum of two loci on chromosome 5A are involved with cold hardening. One locus controls hardiness in part and is tightly linked to the one that controls in part the length of leaves of hardened plants. The other locus is, or it tightly linked to, Vrn1, a winter-spring growth habit locus. This locus may also control part of rosette growth habit. It is postulated that Vrn1 is involved in sensing temperature and in part triggering vernalization, cold hardening, and the development of the rosette growth habit. If so, Vrn1 could code for production of a temperature-sensitive protein, which undergoes conformational changes with changes in temperature.Key words: Triticum aestivum L., cold hardiness, vernalization, rosette growth habit, plant height, leaf length, temperature sensing.
Meiotic abnormalities in primary regenerants from callus culture of immature embryos of 'Norstar' winter wheat
Authors: Whelan Ernest D. P.
Published: October 2017

Tissue culture can induce changes in chromosome structure and number in common wheat (Triticum aestivum L.). The type and frequency of such changes were evaluated in primary regenerants extracted from calli of four immature embryos of 'Norstar' winter wheat cultured for various durations. Meiotic analyses of samples from 18 or 19 primary regenerants from a single embryo cultured for 6, 10, or 14 weeks detected chromosomal changes in 17–20% of the samples. Analyses of 20 duplicate samples from these plants indicated that 7 (35%) plants were chimeras. Similar analyses for nine duplicate samples from plants extracted from an embryo cultured for 18 weeks failed to detect any chimeras, but meiotic abnormalities were much more frequent, with about one-half of the 46 plants sampled showing chromosomal structural changes; translocations were the most common abnormality. Plants regenerated from this embryo also were characterized by an abnormal chromosome, believed to contain a deletion, that was not considered to have been induced by tissue culture.Key words: tissue culture, meiotic abnormalities, Triticum aestivum, aneuploidy, translocations, chimeras.
Karyotype, C-banding, chromosomal location of active nucleolar organizing regions, and B-chromosomes in Lasius niger (Hymenoptera, Formicidae)
Authors: Palomeque T. , Chica E. , Guardia R. Díaz de la
Published: October 2017

The karyotype of Lasius niger (n = 15) was analysed using C-banding and observation of nucleolar organizing region (NOR) sites. C-banding showed the existence of heterochromatin in the paracentromeric regions of all chromosomes. Two sites with primary NORs were found in chromosomes 6 and 8. Chromosome 13 showed a secondary NOR. In both cases, the NORs were located in the paracentromeric region. B-chromosomes were found in male and female germ cells. They exhibited intra- and inter-individual numerical variation. No B-chromosomes were observed in somatic cells (cerebral ganglion cells) of all castes. The Bs are telocentric, small, and clearly distinguishable from the regular members of the complement. They show positive heteropycnosis in meiotic prophase and they are highly C-band positive. The activity of NORs does not change when Bs are present. Several aspects of the behaviour of these Bs are examined.Key words: C-bands, nucleolar organizing region (primary), nucleolar oganizing region (secondary), B-chromosomes, Formicidae.
Introgression of Solarium acaule germ plasm from the endosperm balance number 2 gene pool into the cultivated endosperm balance number 4 potato gene pool via triplandroids
Authors: Brown C. R. , Adiwilaga K.
Published: October 2017

Triploid plants from interspecific crosses between selected clones of Solanum acaule and a 2n pollen producing, cultivated diploid expressed an average of 7.7% to 2n pollen, called triplandroids. Percent stainable pollen of these triploids ranged from 1.8 to 22.1%. The cytological mechanism of 2n pollen formation was parallel orientation of spindles in the second division of meiosis. Three triplandroid-producing triploids were crossed to several tetraploid potato cultivars and breeding clones. Of these 4x−3x pollinations, 49% produced berries, containing an average of 15.2 seeds. Progeny from 4x−3x crosses were 67% pentaploid, 2n = 60, and 33% aneuploids 2n = 56–59, mostly 2n = 59. Thus, functional microspores from triploids were predominantly triplandroids, 2n = 3x = 36, with low frequencies of aneuploidy. This use of a triplandroid bridge is a rapid means of introducing S. acaule germ plasm to the cultivated tetraploid gene pool.Key words: interspecific hybrids, parallel spindles, pollen restitution, triploidy, 2n pollen.
Cytogenetic and isozyme studies of wild and cultivated Capsicum annuum
Authors: Conicella C. , Errico A. , Saccardo F.
Published: October 2017

The esterase isozymes of 15 wild and cultivated accessions of Capsicum annuum from different geographic areas throughout the United States, Mexico, Central America, and South America showed three patterns. All accessions from central Mexico, including the cultivated type, and some from the United States, had pattern A. Other accessions from the United States, those from Central America, and those from Peru had pattern B; those from Colombia had pattern C. Pattern C had more bands, apparently identical with those in the hybrids between A and B. F1 plants between the Colombian accession used in a hybridization test and accessions with patterns A and B showed associations of four or six chromosomes at metaphase I of meiosis. The hypothesis is discussed that pattern C resulted from a process of gene duplication. The alternative explanation of permanent translocation heterozygosity is excluded because in the Colombian accessions no multivalents were observed at meiosis.Key words: Capsicum, geographic distributions, duplication, translocation, isozymes.
Isolation of repeated DNA sequences from Lophopyrum elongatum for detection of Lophopyrum chromatin in wheat genomes
Authors: Zhang Hong-Bin , Dvořák Jan
Published: October 2017

Species of the genus Lophopyrum are closely related to the genus Triticum and have been extensively used in wheat breeding. To facilitate the detection of the Lophopyrum chromatin in wheat, two repeated nucleotide sequences were isolated from L. elongatum (Host) Löve (= Agropyron elongatum Host, Elytrigia elongata (Host) Nevski), which hybridized strongly with the DNAs of Lophopyrum species but weakly (pLeUCD1) or essentially not at all (pLeUCD2) with those of Triticum species. Both sequences were shown to be on all chromosomes of L. elongatum. Each chromosome arm of L. elongatum showed a unique pattern of restriction fragments hybridizing with pLeUCD2. The analysis of chromosomes recombinant between chromosome arm 3AgL of L. ponticum (Podp.) Löve and chromosome arm 3DL of wheat (T. aestivum L.) showed that regional heterogeneity of the pLeUCD2 family occurs also within the arm. It was demonstrated that this heterogeneity can be exploited for identification of Lophopyrum chromatin in wheat and mapping of crossover points in Lophopyrum–wheat recombinant chromosomes by Southern blot analysis.Key words: concerted evolution, Triticum, gene transfer.
Replicate differences in lines of mice selected for body composition
Authors: Eisen E. J. , Pomp D.
Published: October 2017

Replicate differences were studied in lines of mice selected at 12 weeks of age for high (HF1, HF2) or low (LF1, LF2) right epididymal fat pad weight as a percentage of body weight (%EFP); for high (HL1, HL2) or low (LL1, LL2) hind carcass weight as a percentage of body weight (%HC); and randomly (RC1, RC2). Correlated traits were subcutaneous fat pad weight as a percentage of body weight (%SFP), water weight in hind carcass as a percentage of hind carcass weight (%WAT), body weights at 3, 6, and 12 weeks of age, and 3- to 6-week weight gain. Individual and maternal effects contributed to significant genetic drift for selected and correlated traits. No evidence indicated that drift was greater in selection treatments than in controls. Significant heterosis in replicate crosses within selection treatments was found for %HC in HL, LL, and LF and for %EFP in HF. Heterosis was insignificant in crosses of control replicates. Divergence in parental lines and replicate crosses was similar, indicating that differences in heterosis between high and low lines were small relative to divergence. Asymmetry tended to be greater between replicate crosses and parental lines, because selected replicates have greater average heterosis than control replicates. Multivariate discriminant function and Mahalanobis distance analysis of selected traits showed that divergence between replicates within selection treatments was much less than among selection treatments.Key words: selection, genetic drift, body composition, mice.
Meiotic behaviour of induced autotetraploids in Triticum L.
Authors: Yen Yang , Kimber Gordon
Published: October 2017

Colchicine-induced autotetraploids of Triticum speltoides, T. longissimum, T. sharonense, T. bicorne, T. uniaristatum, T. monococcum, and T. tauschii were all morphologically similar to but larger than their diploid forms. Seed set was lower than in the diploids except for the autotetraploid T. speltoides. Meiotic analysis showed fewer quadrivalents and more bivalents than would be expected in all of these autotetraploids. Arm-pair switch, indicated by complex trivalents and quadrivalents, was found and involved 0.1% of total chromosomes in T. umbellulatum, 0.5% in T. longissimum, 0.7% in both T. sharonense and T. tauschii, 6.3% in T. bicorne, and 15.3% in T. uniaristatum.Key words: meiosis, chromosome association, arm-pair switch, chromosome pairing, bivalentization.
Variation in flowering time and flower and cotyledon color in Ipomoea hederifolia L.
Authors: Brown B. P. , Eckenwalder J. E.
Published: October 2017

Floridian populations of Ipomoea hederifolia L. require significantly less time to come to flower than West Indian and Yucatanian populations. Rapid flowering seems to be dominant in expression over the requirement for a much longer period. Variation in flower and cotyledon color appears to be determined by an intensity locus which is codominant in expression rather than by differences in anthocyanins among populations.Key words: anthocyanins, Ipomoea, photoperiod, inheritance.
Practical air quality management
Authors: Young James WS , Vazquez-Galvez Felipe A
Published: October 2017

Monitoring, analysis, and modelling are essential elements of an air quality management plan. It is beneficial to deal with them as an integrated whole. The paper describes Ciudad Chihuahua, Mexico, the development of a new, user friendly, integrated air quality management system (SIMON), and an example of the use of SIMON to examine "good" and "poor" mitigation strategies that could be applied to reduce high pollutant concentrations. The system design and architecture are documented. The five major parts of SIMON are described: an emission inventory module, the meteorological data module, an air quality monitoring module, a modelling-planning module, and a reporting module. The practical use of SIMON is demonstrated through its application to mitigate high concentrations of particulates in one area of the city.Key words: air quality, management, urban, applied, sustainable, integrated, strategies, inventory, modelling, analysis.
Wetdry composting of organic municipal solid waste: current status in Canada
Authors: Otten Lambert
Published: October 2017

Source separation of municipal solid waste into wet and dry streams is proving to be an attractive alternative in dealing with solid waste, and in achieving provincial and national waste diversion objectives. The system provides important flexibility in the number of waste streams, collection methods, collection frequency, and waste processing. In the past few years, experience has been obtained with two-, three-, and four-stream source separation and collection, composting of the organic waste fraction, and recycling of the valuable dry waste. The systems used in Guelph, Ontario, Lunenburg, Nova Scotia, and Caledon, Ontario, are presented. Public interest and participation has been high, especially when a two-stream, mandatory system is used. Thus, the City of Guelph has reported a 98% participation rate in its two-stream system which means that the public accepted the two-stream approach. Experience has shown that, as the number of streams increase, there is a greater chance of putting waste in the wrong stream. There is a strong demand for compost at a bulk price of about $30/ t FOB at the plant. The processing cost of the three plants varied from $50/t to $80/t of waste received without allowing for credits derived from extended landfill life or reduction in environmental impact.Key words: municipal solid waste, organic, source-separation, composting.
Environmental engineering education in Canada
Authors: Smith Daniel W , Biswas Nihar
Published: October 2017

Environmental engineering education has been an active option for engineers from all disciplines for nearly 50 years at the graduate level. Some graduate programs expanded to integrate students with undergraduate science degrees with the engineering programs, since the cross discipline interaction is required outside the academic programs. In the mid-1980s interest increased to such a level that undergraduate programs began to form. Several of these programs have been accredited in their various forms recognizing the diversity of the field and those presenting the programs. The progression from graduate-degree-based specializations to broad-based undergraduate programs reflects both the increased knowledge in the field and the increased demand for professional engineers capable of responding to public health and environmental protection issues. Graduate programs greatly expand fundamental knowledge of physical, chemical, and biological processes and their application to protection problems. Of course, the doctorate is dedicated to the development of significant new knowledge. This paper defines several of the basic components of the environmental engineering profession and the educational process needed to produce qualified environmental engineers.Key words: environmental engineering, education, courses, undergraduate environmental engineering, graduate environmental engineering.
Risk assessment for environmental contamination: an overview of the fundamentals and application of risk assessment at contaminated sites
Authors: Cushman David J , Driver Keith S , Ball Stephen D
Published: October 2017

Many jurisdictions throughout Canada and the United States allow the decision to proceed with an active site cleanup, an evaluation or monitoring program, or site closure to be determined from the results of a risk assessment. Risk assessment can protect both human health and the environment while providing significant savings to industry and government by reducing unnecessary environmental expenditures and allowing for the more efficient allocation of resources. Risk assessment is a dynamic process which is evolving as new methods for contaminant fate and transport modelling, more complete toxicological data, and more standardized statistical methods become available. Principal methodologies for conducting risk assessments are provided by the United States Environmental Protection Agency (USEPA), the American Society for Testing and Materials (ASTM), and the Canadian Council of Ministers of the Environment (CCME). Risk assessment methodologies include both "forward" risk calculations and "reverse" risk calculations. Uncertainties inherent in risk assessment methodologies can be difficult to quantify and are dealt with by incorporating conservative assumptions throughout the risk assessment process. Institutional controls may be required to ensure the continued validity of assumptions. There is a trend toward the increased application and acceptance of risk assessment, although Canada remains well behind the United States. To ensure the expanded use of risk assessment in Canada, more training for both regulators and environmental professionals, increased public awareness, and the adaptation of the risk assessment methodologies being applied in the United States to reflect the environmental policies and technical concerns of interest across Canada will be required.Key words: risk assessment, petroleum, risk-based corrective action, site remediation, remediation objectives, Canada, institutional controls, ethics.
Advanced technologies in water and wastewater treatment
Authors: Zhou H , Smith Daniel W
Published: October 2017

The use of conventional water and wastewater treatment processes becomes increasingly challenged with the identification of more and more contaminants, rapid growth of population and industrial activities, and diminishing availability of water resources. Three emerging treatment technologies, including membrane filtration, advanced oxidation processes (AOPs), and UV irradiation, hold great promise to provide alternatives for better protection of public health and the environment and thus are reviewed in this paper. The emphasis was placed on their basic principles, main applications, and new developments. Advantages and disadvantages of these technologies are compared to highlight their current limitations and future research needs. It can be concluded that, along with the growing knowledge and the advances in manufacturing industry, the applications of these technologies will be increased at an unprecedented scale.Key words: water treatment, wastewater treatment, membrane filtration, ozonation, advanced oxidation processes, UV irradiation.
New technologies for on-site domestic and agricultural wastewater treatment
Authors: Joy Douglas , Weil Claude , Crolla Anna , Bonte-Gelok Shelly
Published: October 2017

Recently publicized problems of water quality in rural parts of Canada are again bringing increasing attention to methods of dealing with wastewater in rural environments. This includes wastewater from both domestic (principally single-family homes) and agricultural sources. Previous practices which relied on dispersal with little treatment are increasingly unacceptable not only because of the recognition of the weakness of this approach but also because of the increasing intensification of land use in rural areas. Thus the need for additional and improved technologies for treating wastewater, on site, has increased. Because of this, new technologies have been developed which provide better treatment than previous approaches that also rely on natural processes. Examples of the former include peat, sand, and foam filters for domestic on-site wastewater systems. Engineered wetlands to treat barnyard runoff or rural municipal lagoon effluent is an example of a technology using natural processes. This paper describes some of these new technologies and their potential advantages.Key words: rural, wastewater, septic, manure, farm, on site, technologies.
Actin and tubulin in Tetrahymena
Authors: Mitchell E. Jane , Zimmerman Selma , Zimmerman Arthur M.
Published: October 2017

Tubulin and actin are cytoskeletal proteins known to play a major role in dividing cells. Tetrahymena pyriformis, a ciliated protozoan, was used as a model system for investigating tubulin synthesis during cilia regeneration and during the cell cycle. Until recently the identification of actin in Tetrahymena has been controversial. In this report evidence for the presence of actin in Tetrahymena is reviewed and control of actin gene expression during the cell cycle is discussed.
The filamins: properties and functions
Authors: Weihing Robert R.
Published: October 2017

The filamins are a group of homologous proteins defined by their high native molecular weight (500 000), their amino acid compositions, their cross-reactivity to antibodies to heterologous filamins, their localization to actin networks and bundles in situ, and their ability to cross-link actin filaments in vitro into three-dimensional networks and bundles. Native filamins contain two subunits (relative mass = 250 000). Each subunit carries at least one actin-binding site and formation of bivalent dimers is therefore believed to explain filamin's ability to cross-link actin filaments. Formation of networks in vitro (corresponding to formation of macroscopic gels) has been analyzed using the theory of Flory. As predicted, a sharp transition to gel (at the critical gelation concentration of filamin) is observed when actin is mixed with increasing concentrations of filamin and the critical gelation concentration is found to vary inversely with the length of actin filaments. However, the measured values of the critical gelation concentration are all higher (2- to 14-fold) than predicted by the theory and the prediction that the critical concentration varies directly with the actin concentration was verified with only one of two techniques used. Filamin's length (160–190 nm) and flexibility (1000-fold greater than actin filaments) may make it especially well fitted to cross-link actin filaments into three-dimensional networks when present in low molar ratios (1:200 to 1:50) relative to actin. At higher molar ratios (> 1:20) it also cross-links actin filaments into bundles. Assuming that filamin actually helps organize supramolecular structures inside cells (not yet tested directly), then its concentration relative to actin may help determine whether networks or bundles are formed. Other factors that may influence its localization and function inside cells include competition with other actin-binding proteins (such as myosin and tropomyosin) for binding sites on actin and phosphorylation, which may alter its ability to bind to actin.
The actin treadmill
Authors: Wanger Michael , Keiser Thomas , Neuhaus Jean-Marc , Wegner Albrecht
Published: October 2017

Actin filaments can assemble at the barbed end and disassemble simultaneously at the pointed end. Prerequisites for this treadmilling reaction are the structural polarity of actin filaments and tight coupling of the actin assembly reaction and the adenosine triphosphate hydrolysis occurring during actin polymerization. In this article, investigations on the actin treadmill are reviewed.
Concerning the location of the GTP hydrolysis site on microtubules
Authors: Caplow Michael , Shanks John , Brylawski Bruna Pegoraro
Published: October 2017

The kinetics for GTP hydrolysis associated with microtubule assembly with microtubular protein has been analyzed under reaction conditions where tubulin–GDP does not readily assemble into microtubules. The GTPase rate is only slightly faster during the time when net microtubule assembly occurs, as compared with steady state. The slightly slower steady-state GTPase rate apparently results from GDP product inhibition, since the progressive decrease in the rate can be quantitatively accounted for using the previously determined GTP dissociation constant and the Ki value for GDP. Since the GTPase rate is not a function of the rate for net microtubule assembly, it is concluded that GTP hydrolysis is not required for tubulin subunit incorporation into microtubules. The constancy of the rate indicates that the GTPase reaction occurs at a site, the concentration of which does not change during the assembly process. This result is consistent with a reaction scheme in which GTP hydrolysis occurs primarily at microtubule ends. We propose that hydrolysis occurs at microtubule ends, at the interface between a long core of tubulin–GDP subunits and a short cap of tubulin–GTP subunits.
The intermediate filament protein desmin in cardiac and skeletal muscle from normal and dystrophic (BIO 14.6) hamsters
Authors: Pollock Michael , Atkinson Burr G.
Published: October 2017

Electrophoretic separation on polyacrylamide gels of polypeptides extracted from skeletal and cardiac muscle of BIO 14.6 dystrophic, carrier, and random-bred normal hamsters demonstrates similar quantities and electrophoretic mobility of a protein having a relative mass of 52 000 daltons (apparent isoelectric point 6.2) from all sources examined; we have tentatively identified this protein as the intermediate filament protein desmin. Reaction of such separated polypeptides transferred to nitrocellulose blots with antibodies raised against this protein fails to show immunological differences in this 52 000 dalton protein in cardiac and skeletal muscle from normal and dystrophic animals. Indirect immunofluorescence analysis of skeletal myofibrils from 30- to 60-day normal and dystrophic animals shows no differences in Z-line staining when immunoglobulins from anti-α-actinin serum are used as primary antibodies. Immunoglobulins from the putative anti-desmin serum also produce Z-line staining of skeletal myofibrils from normal animals, but fail to bind to the Z-lines of some skeletal myofibrils from dystrophic hamsters.
N,N′-Ethylene-bis(iodoacetamide) as a probe for structural and functional characteristics of brine shrimp, squid, and bovine tubulins
Authors: Luduena Richard F. , Roach Mary Carmen , MacRae Thomas H. , Langford George M.
Published: October 2017

We have developed a simple probe for certain functionally significant features of the tubulin molecule. When bovine brain tubulin is treated with N,N′-ethylene-bis(iodoacetamide) (EBI), two intrachain cross-links, designated βs and β*, are formed in β-tubulin, each one with a unique effect on the electrophoretic mobility of β on gels containing sodium dodecyl sulfate. Formation of the β* cross-link, which involves at least one assembly-critical sulfhydryl, is completely inhibited by colchicine and its congeners, while that of βs is inhibited completely by maytansine and GTP and partly by vinblastine. To see how conserved this complex pattern is in evolution we examined tubulins from the brine shrimp Artemia and the squid Loligo. In both tubulins EBI forms the β* cross-link in a reaction inhibitable by colchicine, podophyllotoxin, and nocodazole. In each tubulin, EBI appears to form a second intrachain cross-link in a reaction that can be inhibited completely by maytansine and GTP and partly by vinblastine. In Artemia, this cross-link alters the electrophoretic mobility to a slightly smaller extent than is the case for βs in bovine brain, but in Loligo the alteration is much greater. It seems that the ligand-binding sites, the critical sulfhydryls, and their spatial interrelationships are strongly conserved and that the βs sulfhydryls or the sequence between them are less strongly conserved in evolution.
Dexamethasone can modulate the synthesis and organization of cytokeratins in cultured differentiating rat hepatocytes
Authors: Marceau Normand , Baribault Helene , Leroux-Nicollet Isabelle
Published: October 2017

Dexamethasone, added to suckling rat hepatocytes cultured in serum-free medium supplemented with insulin and epidermal growth factor (EGF), caused a selective dose-dependent increase in cytokeratin synthesis. The response was dependent on the initial hepatocyte density. At 5 × 104 hepatocytes/cm2 a concentration of 1 or 10 μM dexamethasone, in the presence of insulin, enhanced the synthesis of a 55 000 relative mass (Mr) cytokeratin and to a lesser degree a 49 000 Mr cytokeratin, whereas at 1 × 105 hepatocytes/cm2 10 μM dexamethasone preferentially stimulated a 51 000 Mr component. Preferential synthesis of the 51 000 Mr component also occurred when either 1 or 10 μM dexamethasone was added to cultures seeded at 2 × 105 hepatocytes/cm2. The inclusion of EGF along with dexamethasone and insulin in cultures at 2 × 105 cells/cm2 yielded a differential effect of dexamethasone concentration equivalent to that observed at the lower cell density in absence of EGF. Under conditions where increased cytokeratin synthesis was observed, the hepatocytes maintained a high production of albumin and lost their capacity to produce α-fetoprotein, a change in gene expression associated with the normal differentiation of suckling rat hepatocytes. In contrast, no enhancement of cytokeratin synthesis was observed in hepatocytes following addition of EGF and insulin only, a condition that promoted hepatocyte growth and the maintenance of α-fetoprotein production. The dexamethasone-induced enhancement of cytokeratin synthesis was still present at 3 days postseeding. At this time, morphological observations by phase-contrast and immunofluorescence microscopy using monoclonal antibodies against the 55 000 and 49 000 Mr components revealed that under growth-promoting conditions the hepatocytes were spread and the cytokeratin filaments were stretched, whereas under differentiation-promoting conditions the cultures constitute a compact monolayer of cells exhibiting highly ordered filaments. These data suggest a close relationship between synthesis and organization of cytokeratins and promotion of differentiation of suckling rat hepatocytes by glucocorticoids.
A monoclonal antibody to β-tubulin distinguishes a subset of neurons and axons in the chick ciliary ganglion
Authors: Tremblay Jacques P. , Gravel Claude , Hawkes Richard B.
Published: October 2017

A monoclonal antibody, called mabPS2, has been produced by injecting mice with purified postsynaptic densities from adult rat brain. The antibody reacts with an epitope of β-tubulin which is not found on the α-tubulin subunit. In the chick ciliary ganglion mabPS2 reacts both with some large and some small neurons. mabPS2 also labels a subset of myelinated, as well as some unmyelinated axons. Higher magnification of longitudinal sections of axons shows that the reaction product is associated with microtubules. The nerve terminals on the ciliary neurons are also labelled and at higher magnification the label is seen to be distributed generally throughout the cytosol and especially concentrated on the membranes of synaptic vesicles. mabPS2 can therefore be used a a differentiation marker for neurons in chick ciliary ganglion.
Microtubule mutants
Authors: Oakley Berl R.
Published: October 2017

Genetics has become an important tool for studying microtubule structure and function. Mutations in genes that encode microtubule proteins have been isolated in several, evolutionarily diverse organisms. These mutations have been, and will increasingly be, of great value in determining which cellular events are microtubule mediated, in determining which genes encode the microtubule proteins involved in a particular cellular event, and in determining the mechanisms of resistance to anti-microtubule drugs. These mutants also have great potential, which is just beginning to be realized, for identifying proteins other than α- and β-tubulin that are essential to microtubule function and for determining the mechanisms of microtubule-based force production in mitosis and organellar movement.
Genetic and biochemical studies with mutants of mammalian cells affected in microtubule-related proteins other than tubulin: mitochondrial localization of a microtubule-related protein
Authors: Gupta Radhey S. , Venner Thomas J. , Chopra Arvind
Published: October 2017

In Chinese hamster ovary cells, stable mutants exhibiting specific resistance or collateral sensitivity towards the various microtubule inhibitors podophyllotoxin, colchicine, griseofulvin, taxol, nocodazole, vinblastine, and maytansine have been isolated. A number of independent mutants selected for resistance to podophyllotoxin and colchicine contain electrophoretically altered forms of two proteins, P1 and P2, of relative molecular masses of approximately 63 000 and 69 000, respectively. The proteins P1 and P2 have been shown to be microtubule related by a number of different genetic and biochemical criteria and are among the major proteins of Chinese hamster ovary cells, being present in approximately equimolar amounts with tubulin. In addition, a griseofulvin-resistant mutant contains a novel mutation (presumably nonsense) which reduces the relative molecular mass of a protein, P5 [Formula: see text], by about 20 000. Specific antibodies to protein P1 have been raised and cross-reactivity studies show that a similar protein is also present in cells from all vertebrate species examined, viz. man, monkey, mouse, Chinese hamster, Syrian hamster, and chicken. Immunofluorescence studies with anti-P1 and anti-tubulin antibodies show that, in interphase cells from various species, the P1 antibody reacts specifically with mitochondria whose overall cellular distribution is strikingly similar to the distribution of microtubules. The mitochondrial localization of the microtubule-related protein P1 provides strong suggestive evidence regarding the existence of a chemical and functional linkage between these two structures, with protein P1 playing an important role in this linkage. Some implication of these results are discussed and it is suggested that mitochondria play an important role in the dynamics of microtubules.
Maytansine-resistant mutants of Chinese hamster ovary cells with an alteration in α-tubulin
Authors: Schibler Matthew J. , Cabral Fernando R.
Published: October 2017

Mutant clones of Chinese hamster ovary cells resistant to killing by the Vinca alkaloid maytansine have been isolated using a single-step procedure. These mutants are threefold more resistant to killing by the drug than the wild-type parent. The majority of the clones (30 of 34) probably contain alterations in membrane permeability based on their cross-resistance to an unrelated drug, puromycin. Two of the four puromycin-sensitive clones were found to contain "extra" spots which migrated close to α-tubulin on two-dimensional gels. The "extra" spots were shown to be electrophoretic variants of α-tubulin with an identical two-dimensional tryptic peptide map to that of the wild-type α-tubulin. The α-tubulin mutants were cross-resistant to other microtubule disrupting drugs such as griseofulvin, vinblastine, and colcemid, but were more sensitive to the microtubule-stabilizing agent taxol than the wild-type parental cells. Mutant – wild-type hybrids were found to be resistant to levels of maytansine intermediate between the lethal doses for mutant and wild-type cells. A possible explanation for the drug resistance of these mutants is discussed.