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Megumi Fujiwara,1,2 Tomohiro Yonezawa,3 Toshiro Arai,1 Ichiro Yamamoto,1 Hiromichi Ohtsuka21Laboratory of Veterinary Biochemistry, Nippon Veterinary and Life Science University, Tokyo, Japan; 2Laboratory of Large Animal Internal Medicine, 3Laboratory of Veterinary Physiology, Kitasato University, Towada, JapanPurpose: The immune system is considered to be affected by aging, which is linked to various immune pathogeneses. The purpose of this study was to determine age-associated changes in immune function of healthy dogs (beagles), specifically those of naive and memory T lymphocytes, based on cytokine synthesis.Patients and methods: Blood samples were obtained from 44 healthy beagles that were divided into three age-groups: young (8 years). Subpopulations of T lymphocytes were determined by flow cytometry. Transcriptional (mRNA) levels of cytokines were determined for primary-cultured leukocytes using quantitative real-time polymerase chain reaction.Results: There were negative correlations between dogs’ages and the number of peripheral blood mononuclear cells, T cells, and B cells. In particular, the number of naive CD4+ CD45RA+ T cells and CD8+ CD45RA+ T cells significantly decreased with age. The mRNA levels for interleukin (IL)-2, IL-2Rα, and interferon-gamma were significantly higher in young or middle-aged dogs (P < 0.05), whereas IL-4 mRNA expression was not significantly different over the different age-groups. IL-2Rγ mRNA expression tended to decrease with age.Conclusion: Decreases of naive CD4+ and naive CD8+ T cells may be related to age-related immunosenescence in dogs. With regard to cytokine production, leukocyte IL-4 and IL-10 mRNA levels did not change with age, whereas IL-2, IL-2Rα, and IL-2Rγ mRNA levels decreased with age. These altered cytokine mRNA expression patterns may contribute to decreased naive T-cell function(s) with aging.Keywords: aging, leukocyte subpopulation, cytokine, dog, naive T cell, IL-2R

Urea is an important reutilizable nitrogen source for the ruminant and is mainly synthesized through the urea cycle in the liver. The cycle is undertaken by 5 enzymes: carbamoyl phosphate synthetase (CPS), ornithine transcarbamoylase (OTC), arginino-succinate synthetase (AS), argininosuccinate lyase (AL), and arginase. The purpose of this study was to investigate changes in the activity of the enzymes and mRNA expression, given that previous observations have indicated an increase in plasma urea concentrations with age in Holstein calves. First, plasma concentrations of metabolites and hormones were determined in calves at 1, 3, 8, 13, and 19 wk of age (n = 4, weaned at 6 wk of age). The plasma concentration of urea drastically increased after weaning (P < 0.001). The plasma concentration of glucose was lowest at 8 wk. The plasma concentration of IGF-I gradually increased with age, although those of NEFA, glucagon, and cortisol decreased (P < 0.001). Concentrations of triglyceride, [alpha]-amino nitrogen, growth hormone, and insulin did not change significantly with age of the calf. Next, using the liver tissues taken from calves at 2, 13, and 19 wk of age (n = 4 to 6 at each time point, weaned at 6 wk of age), we measured the activity and mRNA expression of the enzymes by biochemical methods and quantitative reverse transcription-PCR, respectively. The activities of CPS (P < 0.001), OTC (P = 0.001), and AS -(P = 0.015) increased with age, whereas AL (P = 0.003) decreased. Although mRNA expression was decreased with age for AL (P = 0.002) and arginase (P = 0.007), no significant change was observed for CPS, OTC, or AS mRNA expression. We conclude that the increased urea production in the liver may be explained not only by an increase in the activities of the urea cycle enzymes, but also by increased ammonia production by rumen fermentation and gluconeogenesis from amino acids around weaning time. Key words: calf, development, liver, mRNA, urea cycle enzyme, weaning

This paper presents a new, practical method of simulating the behavior of arcs driven by magnetic force in a gas. This simulation method is very useful in designing electric devices using magnetically driven arc technique. First, we describe the arc model. In this model, the arc is assumed to be a chain of small rigid cylindrical current elements. Each element receives Lorentz's force from the magnetic field and a fluid drag force from the surrounding gas. Owing to the similarity between an arc and a rigid column, the drag force of the arc is expressed by that of the column. The element moves with the velocity determined by these forces. Consequently, we can obtain the behavior and the shape of the whole arc. Finally, simulation example is shown.