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21.
Tyrosine kinase signaling pathways are essential for process outgrowth and guidance during nervous system development. We have examined the roles of tyrosine kinase activity in programming growth cone guidance decisions in an intact nervous system in which neurons can be individually identified. We applied the tyrosine kinase inhibitors herbimycin A and genistein to whole 40% grasshopper embryos placed in medium, or injected the inhibitors into intact grasshopper eggs. Both inhibitors caused interneuronal axons that normally would grow along the longitudinal connectives to instead leave the central nervous system (CNS) within the segmental nerve root and grow out toward the body wall muscles. In addition, herbimycin A produced pathfinding errors in which many longitudinal axons crossed the CNS midline. To study how this drug affected guidance decisions made by individual growth cones, we dye-filled the pCC interneuron, which normally extends an axon anteriorly along the ipsilateral longitudinal connective. In the presence of herbimycin A, the pCC growth cone was redirected across the anterior commissure. These phenotypes suggest that tyrosine kinase inhibition blocks a signaling mechanism that repels the growth cones of longitudinal connective neurons and prevents them from crossing the midline. 相似文献
22.
Spatial correlations define the statistical structure of any visual image. Two-point correlations inform the visual system about the spatial frequency content of an image. Higher-order correlations can capture salient features such as object contours. We studied "isodipole" texture discrimination in V1 to determine if higher-order spatial correlations can be extracted by early stages of cortical processing. We made epicortical, local field potential, and single-cell recordings of responses elicited by isodipole texture interchange in anesthetized monkeys. Our studies demonstrate that single neurons in V1 can signal the presence of higher-order spatial correlations in visual textures. This places a computational mechanism, which may be essential for form vision at the earliest stage of cortical processing. 相似文献
23.
KP Dingemans MA van den Bergh Weerman RF Keep PK Das 《Canadian Metallurgical Quarterly》1994,57(3):433-439
We have previously reported that an invasive morphotype can be evoked in a rat colon carcinoma by transplanting it into pre-induced subcutaneous granulation tissue. We have now studied the interaction of the same tumor with liver tissue, which is extremely poor in connective tissue in comparison with the subcutaneous site. Tumor cells were injected into the portal system and the resulting experimental liver metastases were examined by electron microscopy and immunohistochemistry. Early metastases consisted of well-differentiated acini, fully surrounded by connective tissue that was derived from the periportal stroma. In a later stage, this connective tissue was overgrown by tumor cells and, almost immediately, acinar differentiation was lost. Most metastases eventually reached the liver capsule, which reacted by forming a layer of granulation tissue. Only in this layer, we observed invasion by thin tumor cell strands, which were often intimately associated with fibroblasts or with blood capillaries. The tumor cells remained smooth and rounded during this process. After fully penetrating the granulation tissue, the tumor cell strands reached the liver surface, where they formed poorly structured papillary masses that were nearly devoid of stroma. Our observations indicate that, even in a relatively homogeneous organ like the liver, the tumor-host interaction is highly complex and dynamic. They also confirm the notion that granulation tissue stimulates tumor invasiveness. Finally, they show that tumor cells can actively invade host tissues without exhibiting a "fibroblastic" morphology. 相似文献
24.
The design and operating characteristics of a dye laser pumped by a 3-W copper-vapor laser (CVL) and injection seeded by low-power (1-5 mW) He-Ne lasers at 633 nm are reported. An extremely simple optical arrangement is used wherein the output mirror of the He-Ne laser and a third mirror form the dye laser cavity. Laser efficiency in fixed-wavelength operation has been investigated for variable CVL pump power, He-Ne injection power and polarization, and cavity output coupling for a standard Rhodamine 590/Rhodamine 640 dye solution. Over 90% of free-running (unseeded) laser power is obtained in fixed-wavelength (seeded) operation at low CVL pump powers (≤1 W), dropping to approximately 60% at 3-W pump power. Maximum CVL pump to dye laser optical conversion efficiency in narrow-band, fixed-wavelength operation at 633 nm was 12%. 相似文献
25.
We reviewed 410 cases, 365 males and 45 females, mean age 64 years, of inguinal and femoral hernia, from 1/1/1991 to 31/12/1994, repaired with Lichtenstein and Trabucco techniques. Recurrent hernias repaired were 36 (8,8%). Local anesthesia was used in 82% and follow-up has ranged from 6 months to 4 years. The meshes used are made with a single layer of polipropylene and the Trabucco plugs T1 were made by hand at the operating table. In our experience these two techniques are simple, but is very important, before application of the mesh, a correct dissection of inguinal region. We made a complete excision of cremasteric fibers preservig, if possible, the genital branch of the genitofemoral nerve. The transversalis fascia is introflected and sutured in direct hernia repair or when there are a loss of tissues. The preliminary results obtained with the "tension free" hernioplasty are satisfying. The most important complications were 9 hematomas and an important and persistent inguinal neuralgia in 1 case. There were no recurrences, but we must considered the short follow-up period. 相似文献
26.
KK M?kinen CY Chen PL M?kinen CA Bennett PJ Isokangas KP Isotupa HR Pape 《Canadian Metallurgical Quarterly》1996,30(3):180-188
The concern with nursing research in the future work of nurse graduates. Expectations from the viewpoint of the nurse researcher. Keeping in mind the concerns which occupy nurse researchers now and in the future, expectations are raised of the graduates of degree programmes in nursing science which are now also being established in the Federal Republic of Germany. This takes into account the structurally determined areas of self determined action in new fields of professional practice. Nurse graduates will be seen as "change agents" in their future areas of work and will have three essential aspects of involvement with nursing research: 1. they themselves will conduct research 2. they will receive, put into practice and transmit results of nursing research 3. they will initiate and commission nursing research projects. According to the broad topics of nursing research, requirements for nurses to act as professionals in their new working fields are formulated referring to the given structural conditions in Germany. 相似文献
27.
Rectal ischemia is rare because of excellent collateral supply. Although rectosigmoid ischemia is usually accompanied by more proximal colonic involvement, it may occur alone. METHODS: A retrospective review of all patients diagnosed as having colonic ischemia at the Mayo Clinic from 1976 to 1991 was performed. Clinical, endoscopic, radiological, and pathological data were obtained from patient charts. Patients with involvement of the rectosigmoid colon extending to no more than 30 cm above the dentate line on endoscopy were included in the study. A single radiologist reviewed CT scans and aortograms, and a single pathologist reviewed tissue specimens. RESULTS: Ten of 328 patients with ischemic colitis had isolated ischemic proctosigmoiditis. Six patients had acute ischemia (i.e., symptom duration of less than 4 wk), and four had chronic ischemia (symptoms for 4 wk or longer). Ischemic proctosigmoiditis affects elderly patients with atherosclerosis. An identifiable precipitating factor, such as a major illness or hemodynamic disturbance, was identified in four of six patients with acute ischemic proctosigmoiditis and in one of four patients with chronic ischemic proctosigmoiditis. CT revealed rectal wall thickening and/or perirectal stranding. Angiography may demonstrate atheromatous disease of the aortoiliac vessels. Acute and "chronic" presentations had similar histopathological changes. CONCLUSIONS: Ischemic proctosigmoiditis is rare. In contrast to generalized colonic ischemia, patients with acute rectal ischemia often have clearly identifiable precipitating factors. Conservative management is appropriate for uncomplicated acute ischemic proctosigmoiditis. Patients with chronic ischemic proctosigmoiditis. Patients with chronic ischemic proctosigmoiditis may develop bowel perforation necessitating a proctectomy or colonic diversion. Recognition of this entity and differentiation from idiopathic inflammatory bowel disease is important to determine appropriate therapy. 相似文献
28.
Cytotoxic T lymphocyte (CTL) activation requires specific T cell receptor (TCR)-class I major histocompatibility complex (MHC) antigen complex interactions as well as the participation of coreceptor or accessory molecules on the surface of CTL. CD8 can serve as a coreceptor in that it binds to the same MHC class I molecules as the TCR to facilitate efficient TCR signaling. In addition, CD8 can be "activated" by TCR stimulation to bind to class I molecules with high avidity, including class I not recognized by the TCR as antigenic complexes (non-antigen [Ag] class I), to augment CTL responses and thus serve an accessory molecule function. A Glu/Asp227-->Lys substitution in the class I alpha 3 domain acidic loop abrogates lysis of target cells expressing these mutant molecules by alloreactive CD8-dependent CTL. Lack of response is attributed to the destruction of the CD8 binding site in the alpha 3 domain which is likely to disrupt CD8 coreceptor function. The relative importance of the class I alpha 3 domain acidic loop Glu227 in coreceptor as opposed to accessory functions of CD8 is unclear. To address this issue, we examined CTL adhesion and degranulation in response to immobilized class I-peptide complexes formed in vitro from antigenic peptides and purified class I molecules containing wild-type or Glu227-->Lys substituted alpha 3 domains. The alpha 3 domain mutant class I-peptide complexes were bound by CTL and triggered degranulation, however to much lower levels than wild-type class I-peptide complexes. In further experiments, it is directly demonstrated that the alpha 3 domain mutant class I molecules, which lack the Glu227 CD8 binding site, still serve as TCR-activated, avidity-enhanced CD8 accessory ligands. However, mutant class I peptide Ag complexes failed to effectively serve as CD8 coreceptor ligands to initiate TCR-dependent signals required to induce avidity-enhanced CD8 binding to coimmobilized non-Ag class I molecules. Thus the Glu227-->Lys mutation effectively distinguishes CD8 coreceptor and avidity-enhanced CD8 accessory functions. 相似文献
29.
Residuals of facial paralysis consist of a great variety of cosmetic and functional anomalies which differ in quality and/or quantity. An internationally standardized evaluation of such defects is mandatory for the assessment of the results of different therapeutic procedures. In the present study, a system has been developed to record the results of facial paralysis following therapy. Such a system does not require specialized training, instrumentation or require significant time for completion. A clearly-defined "Yes-No" evaluation criteria is established which creates a high interscorer reliability. The usefulness of this scoring system was tested by three examiners on 42 patients following facial nerve surgery, with an obtained interscorer reliability of 93%. 相似文献
30.
A young female with ulcerative colitis associated with positive direct and indirect Coombs reaction and severe autoimmune hemolytic anemia is reported. Cortisone was beneficial and total colectomy was promptly followed by subsidence of the hematologic defects. Review of the literature suggests that this complication of ulcerative colitis is uncommon. It basis is unclear. It seems to be expressed through the presence of a "warm" auto-antibody. Colectomy should be strongly considered when severe hemolysis is present but not when the Coombs test is positive alone without significant hemolysis. 相似文献