Objective: The present study simultaneously investigated the effects of different zinc (Zn) levels on the growth performance and relative biochemical parameters in growing rats and analyzed the molecular mechanism of zinc influencing food intake.Methods: Three diets with different Zn levels-Zn adequate (ZA; 35.94 mg/kg, control), Zn deficient (ZD; 3.15 mg/kg), and Zn overdose (ZO; 347.50 mg/kg)-were fed to rats for 6 wk. Dietary Zn was supplemented with ZnSO4. The relation between zinc and food intake was studied by pituitary cDNA microarrays.Results: Compared with ZA group, rats fed the ZD diet showed decreases in body weight (P < 0.01), food intake (P < 0.05), tissue zinc concentrations (P < 0.01), and specific activities of alkaline phosphatase (P < 0.01) and copper/Zn superoxide dismutase (P < 0.05), whereas the ZO diet had positive effects on body weight (P < 0.05), zinc concentrations (P < 0.01), and alkaline phosphatase activity (P < 0.05). The villi of the jejunum became shorter (P < 0.01), shriveled, and flattened. This change in morphology decreased absorption surface area, and there was a substantial decrease (P < 0.01) in villi number per unit area in ZD rats. Metallothionein concentration was increased in livers of rats fed ZD (P < 0.01) and ZO (P < 0.05) diets. Moreover, ZD and ZO influenced normal growth and development of organs. The results from pituitary cDNA arrays indicated that different Zn levels affect gene expression of appetite-related peptides, including neuropeptide-Y, melanin-concentrating hormone, ghrelin, calcitonin gene-related product, and serotonin.Conclusion: The present results showed that zinc deficiency has a negative effect on the growth performance and biochemical parameters of rats. The ZO diet increased body weight (P < 0.05) but had no effect (P > 0.05) oil food intake, copper/Zn superoxide dismutase activity, and intestinal morphology. The ZD diet decreased rat food intake by regulating appetite-related gene expression in the pituitary gland. (c) 2006 Elsevier Inc. All rights reserved.

The effect of magnetite concentration and applied magnetic field on pool boiling heat transfer of a water-based magnetic fluid was investigated on a horizontal heater. The experiments show that the heat transfer of the dense magnetic fluid was reduced while there was an optimum magnetite concentration in which the enhancement of heat transfer was best for the dilute magnetite particles; this conclusion was the same with the applied magnetic field. The applied magnetic field made the boiling heat transfer of magnetic fluid enhance.

The normal condition of air flow through axial flow fans outlet was studied based on the phenomenon of air flow away from solid boundary.It was pointed that the determination of outlet area of axial flow fans accodring to the standard GB1236—2000 isn't reasonable.Some suggestions were made for this problem.

本文从原理上探讨了风力通风机在自然风作用下的工作原理,风速和转速之间的关系,并通过简单的试验进行了验证.

通过对通风过程的研究,得到了一个用于评价通风系统性能的通风效率和空气龄的方法.与以往方法相比,该法简单,易于操作,既可以用于同一空间不同空调系统的比较,也可用于不同空间不同空调系统的比较,还可以比较不同通风量时通风系统的优劣.

The relationship between thrust and flow quantity and the relationship between thrust and pressure is derived theoretically. It, which is tested, can be used in fan design.

本文对于空调客车通风系统中存在的问题进行了分析,指出了由于换气扇结构和使用上的不合理,既造成通风效果不显著,又浪费了能源.在此基础上,提出了减少能耗提高功效的改进措施.

本文从液体与固体界面之间的关系,以及它们之间存在的表面张力入手,从另一个角度探讨了磁流体密封的机理.通过分析和试验,得出了磁流体密封能力与表面张力间的定性关系.在把磁性力作为附加的范德瓦引力的新思路基础上,提出了磁表面张力新概念,为研究磁流体密封能力作了一些基础性的工作.

对磁流体在转轴密封中的应用作了探讨.阐明了磁流体密封的原理,根据磁学理论进行了磁回路的计算.在此基础上设计了磁流体密封的试验装置.实验中采用不同的密封间隙,以确定磁流体密封能力与密封间隙之间的关系.同时,进行了轴旋转和静止时磁流体密封能力变化的试验.试验结果表明,磁流体的密封能力随密封级数的增加而提高,随密封间隙的增大而减小,密封间隙在0.05～0.20mm时,效果较好,同时密封级数有一个最佳值.

从圆盘风机的特点出发,分析了单个圆盘转动时,其表面带动气体的流动情况;在轴对称流动的假定下,用量纲分析法,探讨了圆盘所能带动气流层的厚度.利用分析结果考察了一个圆盘风机,在其他条件相同的情况下,分别对三个不同的圆盘间距作了测试.结果表明,圆盘风机在最大风量时的盘间距与分析的结论较一致.

Aquaporin-4 is a mammalian water channel protein that is predominately expressed in brain, where it is believed to mediate water homeostasis. Here we report the isolation and characterization of the cDNA for mouse Aqp4 and map the gene to the proximal region of mouse chromosome 18. This region contains the neurological mutation ataxia, but further analysis reveals that Aqp4 is not responsible for the ataxia phenotype.

The aquaporin family of membrane water transport proteins are expressed in diverse tissues, and in brain the predominant water channel protein is AQP4. Here we report the isolation and characterization of the human AQP4 cDNAs and genomic DNA. Two cDNAs were isolated corresponding to the two initiating methionines (M1 in a 323-aa polypeptide and M23 in a 301-aa polypeptide) previously identified in rat [Jung, J.S., Bhat, R.V., Preston, G.M., Guggino, W.B. & Agre, P. (1994) Proc. Natl. Acad. Sci. USA 91, 13052-13056]. Similar to other aquaporins, the AQP4 gene is composed of four exons encoding 127, 55, 27, and 92 amino acids separated by introns of 0.8, 0.3, and 5.2 kb. Unlike other aquaporins, an alternative coding initiation sequence (designated exon 0) was located 2.7 kb upstream of exon 1. When spliced together, M1 and the subsequent 10 amino acids are encoded by exon 0; the next 11 amino acids and M23 are encoded by exon 1. Transcription initiation sites have been mapped in the proximal promoters of exons 0 and 1. RNase protection revealed distinct transcripts corresponding to M1 and M23 mRNAs, and AQP4 immunoblots of cerebellum demonstrated reactive polypeptides of 31 and 34 kDa. Using a P1 and a lambda EMBL subclone, the chromosomal site of the human AQP4 gene was mapped to chromosome 18 at the junction of q11.2 and q12.1 by fluorescence in situ hybridization. These studies may now permit molecular characterization of AQP4 during human development and in clinical disorders.