Determination of Feeder Cell‐Based Cellular Niches Supporting the Colonization and Maintenance of Spermatogonial Stem Cells from Prepubertal Domestic Cat Testes

Recently, isolation and in vitro culture of putative spermatogonial stem cells (SSCs) in the domestic cat have been conducted. However, the cellular niche conditions that facilitate the establishment and long‐term maintenance of feline SSCs (FSSCs) have not been described. Therefore, we investigated the type of feeder cells used to stimulate colony formation and growth of FSSCs among the various factors in the FSSC niche. Spermatogonial stem cells isolated from feline testes were cultured on mitotically inactivated testicular stromal cells (TSCs) derived from cats, dogs and mice, and mouse embryonic fibroblasts (MEFs). The formation and growth of colonies derived from SSCs cultured on each type of feeder cell were identified at passage 0, and the morphology, alkaline phosphatase (AP) activity and expression of SSC‐specific genes in surviving colonies were investigated at passage 4. Among these diverse feeder cells, TSCs from cat showed the greatest colony formation, growth and maintenance of FSSCs, and SSC colonies cultured by passage 4 showed a typical dome‐shaped morphology, AP activity and expression of SSC‐specific genes (NANOG, OCT4, SOX2 and CD9). Accordingly, these results demonstrate that feline TSCs could be used as feeder cells to support the establishment and maintenance of SSCs from domestic cats.     

The hawaii to tahiti shuttle experiment

The Shuttle Experiment conducted between Hawaii and Tahiti from January 1979 to June 1980 was designed to observe the changing equatorial ocean structure and circulation, to study the variations and interactions of the four major equatorial ocean currents, and to develop a scientific basis for their monitoring by simple observations of thermal structure and sea level. Preliminary analyses of the results show that the equatorial thermal structure remains intact during a normal year and that only the positions and intensities of the currents are subject to change. The water transport of the equatorial undercurrent varied from 25 x 10(6) cubic meters per second in January to 51 x 10(6) cubic meters per second in July, but also exhibited strong short-term pulsations. The equatorial surface flow responded strongly to the winds at periods of 1 month and longer. An array of drifter buoys in the equatoral countercurrent was subject to very little dispersion while traveling over 4500 kilometers in 4 months. Low-frequency fluctuations in the North Equatorial Countercurrent can be monitored by means of the difference in sea level between Fanning and Majuro.     

Power analysis based on spatial effects mixed models: A tool for comparing design and analysis strategies in the presence of spatial variability

Spatial variability among experimental units is known to exist in many designed experiments. Agronomic field trials are a particularly well-known example, but there are others. Historically, spatial variability has been dealt with in one of two ways: either though design, by blocking to account for spatial effects, or though analysis, by nearest neighbor adjustment. More recently, mixed models with spatial covariance structures such as those used in geostatistics have been proposed. These mixed model procedures have tempted some to conclude—to the dismay of many consulting statisticians—that design principles may be bypassed, since spatial covariance models can recover any lost information. Although design principles clearly should not be ignored, spatial procedures do raise questions. Are traditional notions of appropriate design affected? If so, how? How do spatial effects mixed models compare to conventional analysis of variance used in conjunction with blocked designs? This article presents mixed model methods to assess power and precision of proposed designs in the presence of spatial variability and to compare competing design and analysis strategies. The main conclusion is that, if anything, spatial models reinforce the need for sound design principles, particularly the use of incomplete block designs.     

Cyclic variation in cattle feed intake data: characterization and implications for experimental design

Feed intake data were collected every 6 h in a 140-d feeding trial involving two pens of 15 bull calves, each using one Pinpointer single-animal feeding stall per pen. Spectral analysis of these data revealed strong cyclic patterns of feed intake. These patterns were unique to each animal and consisted of two or more cycle lengths, some up to 28 d, for each animal. Feed intake behavior is an important factor in many forms of animal experimentation. Animal researchers frequently use row-column designs, where columns represent animals and rows represent periods. Latin squares and crossover designs are common examples. Standard analysis of variance procedures are appropriate for these experiments only if certain assumptions are met; one is that if cyclic variation is present, it is identical for all animals, i.e., there is no row X column interaction. If this assumption is not satisfied, standard analysis of variance procedures will result in upward bias of the mean square error and may result in serious distortion of treatment effect estimates. This occurred using the data from the feeding trial reported in this paper. Time-series analysis of covariance greatly improved the accuracy and efficiency of estimates of treatment effects. Consideration of variations in cyclic behavior should be part of the design process in experiments using feed intake data. Guidelines for the design of experiments to take advantage of time-series methodology are given.