Cell Cycle Stage Analysis of Rabbit Foetal Fibroblasts and Cumulus Cells

Synchronization of the cell cycle stages in G0/G1 phase is one of the key factors determining the success of nuclear transplantation. Serum deprivation, contact inhibition and chemical inhibitors are widely used methods for this purpose. In this study, cell cycle stages of foetal fibroblasts and cumulus cells were determined using flow cytometry [fluorescence-activated cell scan (FACS)]. Foetal fibroblasts (in vitro cultured for 72-120 h) and fresh cumulus cells were analysed in Experiment 1. Fifty to 55% proliferating fibroblasts remained in G0/G1 phase compared with 78% in confluent culture (p <0.05). In contrast to foetal fibroblasts, fresh cumulus cells maintained 90% of the population in the G0/G1 stage. When serum was retrieved from the proliferating fibroblasts from day 1 to day 5 (Experiment 2), proportions of G0/G1 cells increased from the initial ratio of 53 to 87% at day 4 of starvation, which was significantly higher than the non-starved proliferating cells (p <0.05). In Experiment 3, fibroblasts were treated with aphidicolin (0.1 microg/ml, 6 h), demicolcine (0.5 microg/ml, 10 h), or a combination of these two chemicals to synchronize the cell cycle stages. Surprisingly, no differences or significantly lower in the proportions of G0/G1)phase cells were detected (25-50%) compared with the uncontrolled growing cells (53%). These results suggested that fresh cumulus cells rest their cell cycle in G0/G1 stage. Serum deprivation became effective in the first 24 h and reached the highest proportions during days 4-5 after deprivation. Chemical synchronization of the cell cycle stage of rabbit foetal fibroblasts to G0/G1 phase appeared less effective compared to serum deprivation.     

Infertility associated with the absence of endometrial progesterone receptors in a bitch

A three‐year‐old intact female Old English sheepdog was presented for evaluation of infertility. A uterine biopsy was performed during dioestrus, and the microscopic appearance was inconsistent with progesterone stimulation; the glands were sparse, simple and failed to show coiling, while the glandular epithelium was cuboidal instead of columnar. There was very little evidence of glandular activity. Due to the inappropriate appearance of the glands for the stage of the cycle, immunohistochemistry for progesterone receptors was performed. No progesterone receptor‐positive immunoreactivity was identified in the endometrial luminal epithelium, glandular epithelium or stroma. Weak intranuclear immunoreactivity was identified within the smooth muscle cells of the myometrium. The absence of progesterone receptors within the endometrial glands is the most likely explanation for the abnormal appearance of the endometrium and for this bitch's infertility. To our knowledge, this is the first report of endometrial progesterone receptor absence in a bitch.     

Organic carbon fluxes and ecological recovery from the cretaceous-tertiary mass extinction

Differences between the carbon isotopic values of carbonates secreted by planktic and benthic organisms did not recover to stable preextinction levels for more than 3 million years after the Cretaceous-Tertiary mass extinction. These decreased differences may have resulted from a smaller proportion of marine biological production sinking to deep water in the postextinction ocean. Under this hypothesis, marine production may have recovered shortly after the mass extinction, but the structure of the open-ocean ecosystem did not fully recover for more than 3 million years.     

Photonic band gap guidance in optical fibers

A fundamentally different type of optical waveguide structure is demonstrated, in which light is confined to the vicinity of a low-index region by a two-dimensional photonic band gap crystal. The waveguide consists of an extra air hole in an otherwise regular honeycomb pattern of holes running down the length of a fine silica glass fiber. Optical fibers based on this waveguide mechanism support guided modes with extraordinary properties.     

Room temperature-operating spin-valve transistors formed by vacuum bonding

Functional integration between semiconductors and ferromagnets was demonstrated with the spin-valve transistor. A ferromagnetic multilayer was sandwiched between two device-quality silicon substrates by means of vacuum bonding. The emitter Schottky barrier injected hot electrons into the spin-valve base. The collector Schottky barrier accepts only ballistic electrons, which makes the collector current very sensitive to magnetic fields. Room temperature operation was accomplished by preparing Si-Pt-Co-Cu-Co-Si devices. The vacuum bonding technique allows the realization of many ideas for vertical transport devices and forms a permanent link that is useful in demanding adhesion applications.     

Genome-wide association analysis of resistance to wheat spindle streak mosaic virus in bread wheat

Wheat spindle streak mosaic virus (WSSMV) is a major concern for cereal crops in Europe and North America. A strong increase in the occurrence of WSSMV has been observed in each French region where susceptible cultivars are cultivated. Most European bread wheat cultivars are resistant, but assessing the status of newly registered cultivars or breeding lines regarding WSSMV resistance is of importance. This paper describes a genome-wide association study carried out on a panel of 163 cultivars and tested for their resistance to WSSMV. Two regions on chromosomes 5B and 7D showed minor effects on WSSMV resistance. More importantly, a large genomic region on chromosome 2D explained most of the resistance to WSSMV. More than 99% of the cultivars carrying the AA genotype at the most associated marker (Excalibur_c15426_661) were resistant to WSSMV, while 100% of the cultivars showing the GG genotype were susceptible. This large genomic region of 45.8 Mb was found distal to the centromere and showed very high linkage disequilibrium. It is hypothesized that this region may be an alien introgression originating from a wild related species. This region contains a total of 2605 predicted genes based on the Chinese Spring IWGSC RefSeq v. 1.0 including genes potentially involved in plant disease resistance. A kompetitive allele-specific PCR (KASP) single-nucleotide polymorphism (SNP) marker was designed in order to identify breeding lines or registered cultivars resistant to WSSMV.     

Tetravalent uranium in calcite

X-ray absorption spectroscopy and x-ray fluorescence microprobe studies of 35-million-year-old calcite from a Mississippi Valley-type zinc ore deposit indicate substitution of tetravalent uranium for divalent calcium. Thus, tetravalent uranium has a stable location in calcite deposited under reducing conditions. This result validates uranium-series dating methods (including uranium/lead dating) for ancient calcite and shows that calcite provides a sink for uranium in deep groundwater aquifers and anoxic lacustrine and marine basins.     

Effect of Reproductive Seasonality on Gamete Quality in the North American Bison (Bison bison bison)

The objective was to investigate the effects of reproductive seasonality on gamete quality in plains bison (Bison bison bison). Epididymal sperm (n = 61 per season), collected during the breeding season (July–September), had significantly higher post‐thaw total motility (36.76 ± 14.18 vs 31.24 ± 12.74%), and lower linearity (0.36 ± 0.06 vs 0.39 ± 0.04) and wobbliness (0.49 ± 0.04 vs 0.51 ± 0.03; mean ± SD) compared to non‐breeding season (January–March) samples. Representative samples (n = 4) from each season were used in heterologous IVF trials using cattle oocytes. Cleavage, morulae and blastocyst percentage were higher for breeding vs non‐breeding season sperm samples (81.88 ± 6.8 vs 49.94 ± 6.77; 41.89 ± 13.40 vs 27.08 ± 23.21; and 30.49 ± 17.87 vs 13.72 ± 18.98%, respectively). Plains bison ovaries collected during the breeding (n = 97 pairs) and non‐breeding (n = 100 pairs) seasons were classified as luteal or follicular. Oocytes recovered from these ovaries were classified into five grades based on morphology. There was no significant difference in the number of luteal ovaries or grades of oocytes recovered. Oocytes were matured, fertilized (with frozen sperm from three bison bulls) and cultured in vitro. Cleavage percentage was higher for oocytes collected during breeding vs non‐breeding season (83.72 ± 6.42 vs 73.98 ± 6.43), with no significant difference in subsequent development to blastocysts. In summary, epididymal sperm from non‐breeding season had decreased total motility and resulted in reduced embryo production in vitro. Oocytes collected during non‐breeding season had reduced ability to be matured, fertilized and/or undergo cleavage in vitro. Data suggested that season influenced gamete quality in plains bison.