猫脑干上涎核节前神经元电活动的观察

在麻醉的32只猫记录了电刺激颌下腺神经支引起的上涎核平均场电位和单位放电。逆行电刺激颌下腺神经支引起的上涎核平均场电位分布在同侧脑干背面闩部头端5.5—8mm处,与过去的组织学结果大致符合。用微电极在上涎核记录了68个对刺激颌下腺神经支有反应的单位,其中33个单位作了碰撞试验。有9个单位符合逆向反应标准,它们是真正的颌下腺节前神经元,逆行反应的潜伏期为14.4±2.5ms,其轴突传导速度为2.9±0.1m/s。其他不符合逆向反应标准的单位,对刺激颌下腺神经支仍能发生反应,估计多为中间神经元。在一部分单位观察了电刺激舌神经或味觉刺激舌引起的反应。根据这些观察对上涎核内存在复杂神经元回路的可能性作了讨论。     

β-Actin Messenger RNA Localization and Protein Synthesis Augment Cell Motility

In chicken embryo fibroblasts (CEFs), β-actin mRNA localizes near an actin-rich region of cytoplasm specialized for motility, the lamellipodia. This localization is mediated by isoform-specific 3′-untranslated sequences (zipcodes) and can be inhibited by antizipcode oligodeoxynucleotides (ODNs) (Kislauskis, E.H., X.-C. Zhu, and R.H. Singer. 1994. J. Cell Biol. 127: 441–451). This inhibition of β-actin mRNA localization resulted in the disruption of fibroblast polarity and, presumably, cell motility. To investigate the role of β-actin mRNA in motility, we correlated time-lapse images of moving CEFs with the distribution of β-actin mRNA in these cells. CEFs with localized β-actin mRNA moved significantly further over the same time period than did CEFs with nonlocalized mRNA. Antizipcode ODN treatment reduced this cell translocation while control ODN treatments showed no effect. The temporal relationship of β-actin mRNA localization to cell translocation was investigated using serum addition to serum-deprived cultures. β-actin mRNA was not localized in serum-deprived cells but became localized within minutes after serum addition (Latham, V.M., E.H. Kislauskis, R.H. Singer, and A.F. Ross. 1994. J. Cell Biol. 126:1211–1219). Cell translocation increased over the next 90 min, and actin synthesis likewise increased. Puromycin reduced this cell translocation and blocked this induction in cytosolic actin content. The serum induction of cell movement was also inhibited by antizipcode ODNs. These observations support the hypothesis that β-actin mRNA localization and consequent protein synthesis augment cell motility.     

A mathematical model for the burden of diabetes and its complications

Background  

The incidence and prevalence of diabetes are increasing all over the world. Complications of diabetes constitute a burden for the individuals and the whole society.     

A two-dimensional mathematical model of percutaneous drug absorption

Background  

When a drug is applied on the skin surface, the concentration of the drug accumulated in the skin and the amount of the drug eliminated into the blood vessel depend on the value of a parameter, r. The values of r depend on the amount of diffusion and the normalized skin-capillary clearence. It is defined as the ratio of the steady-state drug concentration at the skin-capillary boundary to that at the skin-surface in one-dimensional models. The present paper studies the effect of the parameter values, when the region of contact of the skin with the drug, is a line segment on the skin surface.     

Gene doctoring: a method for recombineering in laboratory and pathogenic Escherichia coli strains

Background  

Homologous recombination mediated by the λ-Red genes is a common method for making chromosomal modifications in Escherichia coli. Several protocols have been developed that differ in the mechanisms by which DNA, carrying regions homologous to the chromosome, are delivered into the cell. A common technique is to electroporate linear DNA fragments into cells. Alternatively, DNA fragments are generated in vivo by digestion of a donor plasmid with a nuclease that does not cleave the host genome. In both cases the λ-Red gene products recombine homologous regions carried on the linear DNA fragments with the chromosome. We have successfully used both techniques to generate chromosomal mutations in E. coli K-12 strains. However, we have had limited success with these λ-Red based recombination techniques in pathogenic E. coli strains, which has led us to develop an enhanced protocol for recombineering in such strains.     

Characterization of a beta-actin mRNA zipcode-binding protein.

Localization of beta-actin mRNA to the leading edge of fibroblasts requires the presence of conserved elements in the 3' untranslated region of the mRNA, including a 54-nucleotide element which has been termed the "zipcode" (E. Kislauskis, X. Zhu, and R. H. Singer, J. Cell Biol. 127:441-451, 1994). In order to identify proteins which bind to the zipcode and possibly play a role in localization, we performed band-shift mobility assays, UV cross-linking, and affinity purification experiments. A protein of 68 kDa was identified which binds to the proximal (to the coding region) half of the zipcode with high specificity (ZBP-1). Microsequencing provided unique peptide sequences of approximately 15 residues each. Degenerate primers corresponding to the codons derived from the peptides were synthesized and used for PCR amplification. Screening of a chicken cDNA library resulted in isolation of several clones providing a DNA sequence encoding a 67.7-kDa protein with regions homologous to several RNA-binding proteins, such as hnRNP E1 and E2, and with consensus mRNA recognition motif with RNP1 and 2 motifs and a putative REV-like nuclear export signal. Antipeptide antibodies were raised in rabbits which bound to ZBP-1 and coimmunoprecipitated proteins of 120 and 25 kDa. The 120-kDa protein was also obtained by affinity purification with the RNA zipcode sequence, along with a 53-kDa protein, but the 25-kDa protein appeared only in immunoprecipitations. Mutation of one of the conserved sequences within the zipcode, an ACACCC element in its proximal half, greatly reduced its protein binding and localization properties. These data suggest that the 68-kDa ZBP-1 we have isolated and cloned is an RNA-binding protein that functions within a complex to localize beta-actin mRNA.