Modeling of drug delivery into tissues with a microneedle array using mixture theory

In this paper, we apply mixture theory to quantitatively predict the transient behavior of drug delivery by using a microneedle array inserted into tissue. In the framework of mixture theory, biological tissue is treated as a multi-phase fluid saturated porous medium, where the mathematical behavior of the tissue is characterized by the conservation equations of multi-phase models. Drug delivery by microneedle array imposes additional requirements on the simulation procedures, including drug absorption by the blood capillaries and tissue cells, as well as a moving interface along its flowing pathway. The contribution of this paper is to combine mixture theory with the moving mesh methods in modeling the transient behavior of drug delivery into tissue. Numerical simulations are provided to obtain drug concentration distributions into tissues and capillaries.     

DNA methylation changes in photoperiod-thermo-sensitive male sterile rice PA64S under two different conditions

Epigenetic modification can occur at a high frequency in crop plants and might generate phenotypic variation without changes in DNA sequences. DNA methylation is an important epigenetic modification that may contribute to environmentally-induced phenotypic variations by regulating gene expression. Rice Photoperiod-Thermo-Sensitive Genic Male Sterile (PTGMS) lines can transform from sterility to fertility under lower temperatures and short-day (SD) conditions during anther development. So far, little is known about the DNA methylation variation of PTGMS throughout the genome in rice. In this study, we investigated DNA cytosine methylation alterations in the young panicles of PTGMS line PA64S under two different conditions using methylation sensitive amplified polymorphism (MSAP) method. Compared with the DNA methylation level of PA64S under lower temperatures and SD conditions (fertility), higher methylation was observed in PA64S (sterility). The sequences of 25 differentially amplified fragments were successfully obtained and annotated. Three methylated fragments, which are homologous to D2, NAD7 and psaA, were confirmed by bisulfite sequencing and their expression levels were also evaluated by qPCR. Real time quantitative PCR analysis revealed that five of the six selected methylated genes were downregulated in PA64S (sterility). These results suggested that DNA methylation may be involved in the sterility–fertility transition of PA64S under two different environmental conditions.     

六六六在水环境中转移、积累和归趋研究——3.六六六在鱼体的积累释放

鳃是六六六进入鱼体的主要通道,鱼体的残留水平决定于水与体脂间的分配平衡。要使背肌六六六残留低于0.5毫克/公斤,则水中六六六含量要低于0.024毫克/升。鱼体六六六残留向水体释放的速度与温度有关,温度低,释放慢;当温度低于10℃时,释放的速度极慢以至难以检出。建议采用清水寄养的方法,让鱼体释放六六六,降低残毒,提高商品质量。这种方法估计也适用于其它脂溶性的与水分配系数不是太大的污染物。       

A novel ferritin subunit involved in shell formation from the pearl oyster (Pinctada fucata)

Iron is one of the most important minor elements in the shell of bivalves. This study was designed to investigate the involvement of ferritin, the principal protein for iron storage, in shell formation. A novel ferritin cDNA from the pearl oyster (Pinctada fucata) was isolated and characterized. The ferritin cDNA encodes a 206 amino acid polypeptide, which shares high similarity with snail soma ferritin and the H-chains of mammalian ferritins. Oyster ferritin mRNA shows the highest level of expression in the mantle, the organ for shell formation. In situ hybridization analysis revealed that oyster ferritin mRNA is expressed at the highest level at the mantle fold, a region essential for metal accumulation and contributes to metal incorporation into the shell. Taken together, these results suggest that ferritin is involved in shell formation by iron storage. The identification and characterization of oyster ferritin also helps to further understand the structural and functional properties of molluscan ferritins.     

一氧化氮增加常氧和缺氧豚鼠心室肌细胞持续性钠电流

运用全细胞膜片钳记录缺氧条件下豚鼠心室肌持续性钠电流(INa.P)的变化及施加药物对其的影响,以探讨 INa.P 的本质及缺氧增大 INa.P 的机制。结果显示:(1)在常氧条件下,一氧化氮(NO)前体 L- 精氨酸(L-Arg)和供体硝普钠(SNP)浓度依赖性地增大INa.P; (2)INa.P 随缺氧时间延长而增大, 缺氧15 min 后施加 NO 合酶(NOS)抑制剂L- 硝基精氨酸甲酯(L-NAME), 不能使增大的INa.P 明显回复[(1.344 ±0.320) vs (1.301 ±0.317) pA/pF, P>0.05, n=5]; (3)缺氧时含L-NAME 的灌流液可使INa.P 明显减小,与单纯缺氧相比有显著差异[(0.914 ± 0.263), n=5 vs (1.344 ± 0.320) pA/pF, n=6, P<0.05], 但仍比常氧条件下增大[(0.914 ±0.263) vs (0.497 ±0.149) pA/pF, P<0.05, n=5]; (4)还原剂1,4-二硫代苏糖醇(DTT)不但可使L-Arg 及缺氧后施加SNP 增大的 INa.P 回复[(1.449 ± 0.522) vs (0.414 ± 0.067) pA/pF, P<0.01, n = 6 和(0.436 ± 0.141) vs (1.786 ± 0.636) pA/pF,P<0.01, n=5],而且使正常的 INa.P 减小[(0.396 ± 0.057) pA/pF vs (0.442 ± 0.056) pA/pF, P<0.01, n=6]。本实验结果表明缺氧可增大心室肌细胞的INa.P, 其作用机制可能是缺氧时心肌产生的NO 通过氧化细胞膜上钠通道蛋白所致,正常INa.P 的产生