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.     

Modular hybrid total hip arthroplasty. Experimental study in dogs

Background

This prospective experimental study evaluated the surgical procedure and results of modular hybrid total hip arthroplasty in dogs.

Methods

Ten skeletally mature healthy mongrel dogs with weights varying between 19 and 27 kg were used. Cemented modular femoral stems and uncemented porous-coated acetabular cups were employed. Clinical and radiographic evaluations were performed before surgery and at 30, 60, 90, 120, 180 and 360 days post-operation.

Results

Excellent weight bearing was noticed in the operated limb in seven dogs. Dislocation followed by loosening of the prosthesis was noticed in two dogs, which were therefore properly treated with a femoral head osteotomy. Femoral fracture occurred in one dog, which was promptly treated with full implant removal and femoral osteosynthesis.

Conclusions

The canine modular hybrid total hip arthroplasty provided excellent functionality of the operated limb.     

A finite element model of the bovine claw under static load for evaluation of different flooring conditions

AIM: To create a computer-based finite element (FE) model of the bovine claw and to use finite element analysis (FEA) to estimate stress and deformation of a physiologically-shaped model claw under static load, to visualise potential material weakness and to evaluate the effect of different flooring conditions.

METHODS: Model geometry was derived using digitalised images from a recently trimmed, sound, hind claw from a 4-year-old Austrian Fleckvieh cow. Material properties of bovine claw horn were defined from preliminary investigations and recently established material data, using a modulus of elasticity from 200 to 600 N/mm² . Meshing of the model was performed with 42,127 elements based on 116,141 nodes. Loading of the model was defined at 756 N per claw on a hard and soft surface.

RESULTS: The FE model of the bovine claw under a load of 756 N showed only minimal deformation, most of which took place at the axial wall. Highest stresses were evident in the proximal axial wall, the outer edge of the weight-bearing surface and under the heels. The claw-floor contact image showed a pressure distribution resembling the distal rim of the claw wall. On the hard surface, the maximum stresses were three times higher than those on the soft surface.

CONCLUSIONS AND CLINICAL RELEVANCE: FEA allowed visualisation of the effects that loading on different floor surfaces have on the biomechanics of the claw. Uneven preparation of the claw sole resulted in high stresses at and close to irregularities of the sole. Consequences were more severe on harder flooring. The model supports the hypothesis that mechanical factors play a substantial role in the pathogenesis of claw lesions.