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。     

Salvage after severe lower-extremity trauma: are the outcomes worth the means?

Advances in reconstructive surgery have allowed for impressive salvage after severe lower-extremity trauma but not without complications when compared with immediate below-knee amputation. Several amputation index scores have been developed to help predict successful salvage as defined by a viable rather than a functional extremity. The purpose of this study was to evaluate retrospectively the predictive value of the amputation index scores and to assess prospectively overall health status and specific dysfunction in successful limb salvage and primary and secondary amputation by administering standardized generic and specific outcomes questionnaires (Medical Outcomes Study 36-Item Short-Form Health Survey, Western Ontario and MacMaster Universities Osteoarthritis Index). A retrospective chart review identified 55 severe lower-extremity injuries (Gustilo Type IIIB and IIIC) over a 12-year period (1984 to 1996). Forty-six severe open tibial fractures in 45 patients underwent attempted salvage. All required soft-tissue coverage by either local or free flap or vascular repair for leg salvage. The attempted-salvage group was subdivided into successful salvage and secondary amputation. The other nine patients underwent a primary amputation. There were no statistically significant differences in terms of patient demographics or other injuries (Injury Severity Score) in the three groups. Forty-eight of 54 patients with an average 5-year follow-up completed a validated generic and specific outcomes health questionnaire. In the attempted-salvage group, 89 percent of patients had a successful salvage and 11 percent came to a secondary amputation. The amputation index scores correctly predicted an amputation in 32 percent of patients. The magnitude of the amputation index scores did not correlate with the physical outcomes scores and were not found to add any significant value of information to the surgeon's decision making. Patients undergoing primary and secondary amputation had a worse physical outcomes score (28 versus 38) than successful salvage (p < 0.007). Even so, the SF-36 (physical component score) outcomes score for this group of injured extremities, regardless as to whether salvaged or amputated, was as low as or lower than that of many serious medical illnesses, suggesting that severe lower-extremity trauma impairs health as much as or more than being seriously ill. The mental component score in this group was comparable to that of a healthy population (49 versus 50), which implies the disability is primarily physical rather than psychological. Ninety-two percent of patients preferred their salvaged leg to an amputation at any stage of their injury, and none would have preferred a primary amputation.     

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.     

A preliminary biomechanical study of cyclic preconditioning effects on canine cadaveric whole femurs

Biomechanical preconditioning of biological specimens by cyclic loading is routinely done presumably to stabilize properties prior to the main phase of a study. However, no prior studies have actually measured these effects for whole bone of any kind. The aim of this study, therefore, was to quantify these effects for whole bones. Fourteen matched pairs of fresh-frozen intact cadaveric canine femurs were sinusoidally loaded in 4-point bending from 50?N to 300?N at 1?Hz for 25 cycles. All femurs were tested in both anteroposterior (AP) and mediolateral (ML) bending planes. Bending stiffness (i.e., slope of the force-vs-displacement curve) and linearity R(2) (i.e., coefficient of determination) of each loading cycle were measured and compared statistically to determine the effect of limb side, cycle number, and bending plane. Stiffnesses rose from 809.7 to 867.7?N/mm (AP, left), 847.3 to 915.6?N/mm (AP, right), 829.2 to 892.5?N/mm (AP, combined), 538.7 to 580.4?N/mm (ML, left), 568.9 to 613.8?N/mm (ML, right), and 553.8 to 597.1?N/mm (ML, combined). Linearity R(2) rose from 0.96 to 0.99 (AP, left), 0.97 to 0.99 (AP, right), 0.96 to 0.99 (AP, combined), 0.95 to 0.98 (ML, left), 0.94 to 0.98 (ML, right), and 0.95 to 0.98 (ML, combined). Stiffness and linearity R(2) versus cycle number were well-described by exponential curves whose values leveled off, respectively, starting at 12 and 5 cycles. For stiffness, there were no statistical differences for left versus right femurs (p?=?0.166), but there were effects due to cycle number (p?相似文献   

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.