排序方式: 共有43条查询结果,搜索用时 15 毫秒
1.
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。 相似文献
2.
3.
4.
5.
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. 相似文献6.
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. 相似文献7.
Rowan S Hardy Andrew Filer Mark S Cooper Greg Parsonage Karim Raza Debbie L Hardie Elizabeth H Rabbitt Paul M Stewart Christopher D Buckley Martin Hewison 《Arthritis research & therapy》2006,8(4):R108-10
Stromal cells such as fibroblasts play an important role in defining tissue-specific responses during the resolution of inflammation.
We hypothesized that this involves tissue-specific regulation of glucocorticoids, mediated via differential regulation of
the enzyme 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1). Expression, activity and function of 11β-HSD1 was assessed
in matched fibroblasts derived from various tissues (synovium, bone marrow and skin) obtained from patients with rheumatoid
arthritis or osteoarthritis. 11β-HSD1 was expressed in fibroblasts from all tissues but mRNA levels and enzyme activity were
higher in synovial fibroblasts (2-fold and 13-fold higher mRNA levels in dermal and synovial fibroblasts, respectively, relative
to bone marrow). Expression and activity of the enzyme increased in all fibroblasts following treatment with tumour necrosis
factor-α or IL-1β (bone marrow: 8-fold and 37-fold, respectively, compared to vehicle; dermal fibroblasts: 4-fold and 14-fold;
synovial fibroblasts: 7-fold and 31-fold; all P < 0.01 compared with vehicle). Treatment with IL-4 or interferon-γ was without effect, and there was no difference in 11β-HSD1
expression between fibroblasts (from any site) obtained from patients with rheumatoid arthritis or osteoarthritis. In the
presence of 100 nmol/l cortisone, IL-6 production – a characteristic feature of synovial derived fibroblasts – was significantly
reduced in synovial but not dermal or bone marrow fibroblasts. This was prevented by co-treatment with an 11β-HSD inhibitor,
emphasizing the potential for autocrine activation of glucocorticoids in synovial fibroblasts. These data indicate that differences
in fibroblast-derived glucocorticoid production (via the enzyme 11β-HSD1) between cells from distinct anatomical locations
may play a key role in the predeliction of certain tissues to develop persistent inflammation. 相似文献
8.
9.
David J Lee Lewis EH Bingle Karin Heurlier Mark J Pallen Charles W Penn Stephen JW Busby Jon L Hobman 《BMC microbiology》2009,9(1):252
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. 相似文献10.
Richard D. Rabbitt Sarah Clifford Kathryn D. Breneman Brenda Farrell William E. Brownell 《PLoS computational biology》2009,5(7)
Cochlear outer hair cells (OHCs) are fast biological motors that serve to enhance the vibration of the organ of Corti and increase the sensitivity of the inner ear to sound. Exactly how OHCs produce useful mechanical power at auditory frequencies, given their intrinsic biophysical properties, has been a subject of considerable debate. To address this we formulated a mathematical model of the OHC based on first principles and analyzed the power conversion efficiency in the frequency domain. The model includes a mixture-composite constitutive model of the active lateral wall and spatially distributed electro-mechanical fields. The analysis predicts that: 1) the peak power efficiency is likely to be tuned to a specific frequency, dependent upon OHC length, and this tuning may contribute to the place principle and frequency selectivity in the cochlea; 2) the OHC power output can be detuned and attenuated by increasing the basal conductance of the cell, a parameter likely controlled by the brain via the efferent system; and 3) power output efficiency is limited by mechanical properties of the load, thus suggesting that impedance of the organ of Corti may be matched regionally to the OHC. The high power efficiency, tuning, and efferent control of outer hair cells are the direct result of biophysical properties of the cells, thus providing the physical basis for the remarkable sensitivity and selectivity of hearing. 相似文献