Ca2+ and cell fusion during sexual development in liquid cultures of Dictyostelium discoideum

Cell fusion resulting in zygote giant cell formation is the first observable event of sexual development in D. discoideum. The results reported here show that this process is Ca²⁺-dependent and that by increasing the level of Ca²⁺ in the medium the number of cell fusions can be increased 57-fold over control cultures. The data also suggest that Ca²⁺ has both an early and late function in the development of zygotes and these functions are mediated at the cell surface. These results plus the availability of a liquid culture for generating large volumes of cells make sexual development in D. discoideum an excellent system for the analysis of membrane fusion in eukaryotes.     

Molecular analysis and characterization of the Cochliobolus heterostrophus beta-tubulin gene and its possible role in conferring resistance to benomyl

Cochliobolus heterostrophus Tub1 described here is the first beta-tubulin gene characterized from a naturally occurring benomyl-resistant ascomycete plant pathogen. The gene encodes a protein of 447 amino acids. The coding region of Tub1 is interrupted by three introns, of 116, 55, and 56 nt, situated after codons 4, 12, and 53, respectively. As a result of the preference for pyrimidines in the third position of the codons when a choice exists between purines and pyrimidines, codon usage in the Tub1 gene is biased. Tub1 shows high homology with beta-tubulin genes of other ascomycete species. However, Tub1 is exceptional in having Tyr(167), compared with Phe(167), possessed by beta-tubulin genes of other ascomycetes sequenced thus far. The Tyr(167) residue has been associated with benomyl resistance in other organisms. In contrast, all other benomyl-implicated residues of Tub1 correspond to sensitivity. Based on these results, we suggest that benomyl resistance in the fungus probably is attributed to Tyr(167).     

In vitro shoot culture of wild Oryzae and other grass species

A method was developed for the in vitro clonal propagation of shoots from a range of wild rice and other grass species that have important genetic traits such as drought resistance and salinity tolerance. The axenic multiple shoot cultures, which were suitable for DNA and protein extraction or direct protoplast isolation, could be maintained without subculture for between 2 and 3 months or rapidly multiplied for the subsequent production of mature plants and seeds. Basal sections of the micropropagated shoots also provided novel explants for the production of highly embryogenic callus, from some species, that could be regenerated into green plants. It is envisaged that this clonal propagation technique could aid the genetic manipulation of cultivated rice by providing a means to vegetatively conserve valuable genetic resources, a technique to rapidly multiply novel hybrid material and a source of embryogenic callus that will allow the application of biotechnological techniques, such as somatic hybridization and genetic transformation, to previously unexploited species.Abbreviations BA N⁶-benzyladenine - 2,4-d 2,4-dichlorophenoxyacetic acid - NAA -naphthaleneacetic acid - PAR photosynthetically-active radiation     

Enzymes of Carbohydrate Metabolism in Thiobacillus species

A study was made of enzymes of carbohydrate metabolism in representative thiobacilli grown with and without glucose. The data show that Thiobacillus perometabolis possesses an inducible Entner-Doudoroff pathway and is thus similar to T. intermedius and T. ferrooxidans. T. novellus lacks this pathway. Instead, a non-cyclic pentose phosphate pathway along with the Krebs cycle is apparently the major route of glucose dissimilation in this organism. Glucose does not support or stimulate the growth of strains of T. neapolitanus, T. thioparus, and T. thiooxidans examined, nor does its presence in the growth medium greatly influence their enzymatic constitution. These obligately chemolithotrophic thiobacilli do not possess the Entner-Doudoroff pathway. Their nicotinamide adenine dinucleotide (NAD)-linked isocitrate dehydrogenase activity predominates over their nicotinamide adenine dinucleotide phosphate (NADP)-linked activity; the converse is true for the other thiobacilli. The data suggest that NAD-linked isocitrate dehydrogenase activity in thiobacilli is involved in biosynthetic reactions.     

Reproductive biology of Tilapia zillii (Gervais) in Lake Naivasha,Kenya

Synopsis Tilapia zillii breeds all year round in the equatorial Lake Naivasha with slightly high breeding intensity during wet months (March, May and July–August). A sex ratio of 1 : 1.28 was found between males and females. The smallest mature male and female were 9.0 and 11.0 cm respectively. The fecundity ranged from 2990 to 12344 eggs, with a mean of 6606 eggs. Fecundity showed a curvilinear relationship with total length (log F = 1.7034 + 1.6370 log L) and a linear relationship with body weight (F = 2197 + 28.76 W)     

A preliminary study on the effects of E-Z Mixin® and EquiPlus® extenders supplemented with Edible Bird’s Nest on the quality of chilled Arabian stallion semen

The aim of this study was to evaluate the effects of adding different concentrations of edible bird’s nest (EBN) which is secreted by swiftlet birds (Aerodramus fuciphagus), into EquiPlus® and E-Z Mixin® extenders on the quality of chilled Arabian stallion semen at various storage times (0, 24 and 48 h). Ten ejaculates were collected from five stallions, and diluted using the two extenders containing 0% (control), 0.12%, 0.24% and 0.24% of EBN + seminal plasma (SP). All the diluted semen samples were then cooled and stored at 5 °C, and examined at 0, 24 and 48 h. Sperm kinetic parameters were assessed using computer assisted sperm analysis (CASA) and viability were assessed using Hoechst33342/PI stain. In both extenders, total motility (TM) and progressive motility (PM) were significantly higher at 0.12% and 0.24% compared to 0.24% + SP at 24 and 48 h. At 0.12%, E-Z mixin® treated semen had significantly higher TM and PM than EquiPlus^® at 24 and 48 h. At 0.12% and 0.24%, average path velocity (VAP), straight-line velocity (VSL) and curvilinear velocity (VCL) were significantly higher in E-Z mixin® treated semen compared to EquiPlus^® at 24 and 48 h. Comparisons between the two extender types at different concentrations of EBN showed no significant difference in lateral head amplitude (ALH), linearity (LIN), straightness (STR), beat cross frequency (BCF) and viability, irrespective of the storage time. The percentage of viable was significantly higher in E-Z mixin® than EquiPlus® at 0 and 48 h in control and 0.12%. Supplementation of the E-Z mixin^® extender with 0.12% and 0.24% EBN concentrations in the absence of SP provided better CASA parameters such as TM, PM, VAP, VSL, and VCL at 24 and 48 h storage time. In conclusion, the results of this study indicated that chilled semen from Arabian stallion that was extended using E-Z mixin® and supplemented with 0.12% and 0.24% EBN concentrations performed better and yielded superior results in sperm kinetic parameters and % viable compared to EquiPlus® at 24 and 48 h storage time.     

New species and new records of species of Cloacina von Linstow, 1898 (Nematoda: Strongylida) parasitic in the western scrub wallaby,Notamacropus irma (Jourdan) (Marsupialia: Macropodidae) from Western Australia

Systematic Parasitology - The helminth parasites of the western scrub wallaby or black-glove wallaby, Notamacropus irma (Jourdan) which occurs in Western Australia are relatively poorly documented....     

Osteogenic potential of hexane and dichloromethane fraction of Cissus quadrangularis on murine preosteoblast cell line MC3T3-E1 (subclone 4)

In continuation of the investigation of osteogenic potential of solvent fractions of ethanolic extract of Cissus quadrangularis (CQ), an ancient medicinal plant, most notably known for its bone-healing properties, to isolate and identify antiosteoporotic compounds. In the current study, we report the effect of hexane fraction (CQ-H) and dichloromethane fraction (CQ-D) of CQ on the differentiation and mineralization of mouse preosteoblast cell line MC3T3-E1 (subclone 4). Growth, viability, and proliferation assays revealed that low concentrations (0.1, 1, and 100 ng/ml) of both solvent fractions were nontoxic, whereas higher concentrations were toxic to the cells. Differentiation and mineralization of MC3T3-E1 with nontoxic concentrations of CQ-D and CQ-H revealed that CQ-D delayed the mineralization of MC3T3-E1 cells. However, early and enhanced mineralization was observed in cultures treated with nontoxic concentrations of CQ-H, as indicated by Von Kossa staining and expression profile of osteoblast marker genes such as osterix, Runx2, alkaline phosphatase (ALP), collagen (Col1a1), integrin-related bone sialoprotein (IBSP), osteopontin (OPN), and osteocalcin (OCN). These findings suggest CQ-H as the most efficacious solvent fraction for further investigation to isolate and identify the active compounds in CQ-H.     

Low glucose availability alters the expression of genes involved in initial adhesion of human glioblastoma cancer cell line SF767

Studying the metabolic pathways of cancer cells is considered as a key to control cancer malignancies and open windows for effective drug discovery against cancer. Of all the properties of a tumor, metastasis potential is a defining characteristic. Metastasis is controlled by a variety of factors that directly control the expression of cell adhesion proteins. In this study we have investigated the expression of cell to cell and cell to matrix adhesion protein genes during the initial phases of attachment of human glioblastoma cancer cell line SF767 (66Y old human female: UCSF Neurosurgery Tissue Bank) to the attachment surface under (Cell culture treated polystyrene plate bottom) glucose-rich and glucose-starved conditions. The aim was to imitate the natural microenvironment of glucose availability to cancer cells inside a tumor that triggers epithelial to mesenchymal transition (EMT). In this study, we have observed the gene expression of epithelial and mesenchymal isoforms of cadherin (E-CAD and N-CAD) and Ig like cell adhesion molecules (E-CAM and N-CAM) along with Integrin family subunits for the initial attachment of cancer cells. We observed that high glucose environments promoted cell survival and cell adhesion, whereas low glucose accelerated EMT by downregulating the expression level of integrin, E-CAD, and N-CAD, and upregulation of N-CAM during early period of cell adhesion. Low glucose availability also downregulated variety of structural and regulatory genes, such as zinc finger E-box binding home box 1A), cytokeratin, Snail, and β catenin, and upregulation of hypoxia-inducible factor 1, matrix metalloprotease 13/Collagenase 3, vimentim, p120, and fructose 1,6 bisphosphatase. Glucose conditions are more efficient for cancer studies in this case glioblastoma cells.