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941.
942.
Chlorobutanol (1,1,1-trichlor-2-methyl-2-propanol) decreases the duration of the latent period of Limulus ventral eye receptor potentials. This effect is both concentration and intensity dependent. Between 0.05 and 1 mM chlorobutanol in sea water the extent of latency shortening effect of chlorobutanol linear function of the logarithm of the chlorobutanol concentration. The latency shortening effect of chlorobutanol diminishes with decreasing intensity of stimulation and virtually disappears at intensities just exceeding threshold. These results are explained by postulating that the latent period is composed of two processes only one of which is sensitive to chlorobutanol and, further, that the duration of the chlorobutanol-sensitive process is not appreciably affected by the stimulating intensity. This model of a two component latent period may be tested experimentally. In several experiments prolonged exposure of ventral photoreceptor cells to chlorobutanol coupled with a short exposure to calcium deficient sea water produced a collapse of the receptor potential followed by a slow recovery after returning to perfusion with normal sea water. During the recovery a slow, low amplitude positive wave exists which has been tentatively called a prepotential. 相似文献
943.
944.
Sharif HS; Aideyan OA; Clark DC; Madkour MM; Aabed MY; Mattsson TA; al-Deeb SM; Moutaery KR 《Radiology》1989,171(2):419-425
Radiographs, scintigrams, computed tomographic scans, and magnetic resonance (MR) images of 17 patients with brucellar spondylitis and 15 with tuberculous spondylitis were analyzed to identify distinguishing features. Characteristic findings of brucellar spondylitis included predilection for the lower lumbar spine (68% of lesions), bone destruction limited to the end plates, disk collapse (16 of 19 disks), and granulation tissue or localized soft-tissue edema (17 of 19 sites). MR imaging showed diffuse increased signal in vertebrae and disks on long repetition time (TR)/echo time (TE) images in four patients and focal increased signal with normal disks in one. Epidural extension was best seen on short TR/TE images in four. Tuberculous spondylitis was characterized by predilection for the midthoracic spine (73%), vertebral destruction with gibbus deformity (60%), disk collapse, and paraspinal abscesses (14 of 15). On MR images signal intensity of affected vertebrae was similar to but more severe than findings in patients with brucellar spondylitis. Scintigraphy was the least helpful in differentiating the two infections. Lesions of tuberculous spondylitis affecting the lower lumbar spine were difficult to differentiate from those of brucellar spondylitis. 相似文献
945.
Chronic exposure to tumor necrosis factor in vivo preferentially inhibits erythropoiesis in nude mice 总被引:11,自引:3,他引:8
The anemia of chronic disease (ACD) is associated with conditions in which macrophage activation occurs. Activated marrow macrophages suppress erythropoiesis in vitro and produce tumor necrosis factor (TNF). Therefore, we tested the effects of chronic in vivo exposure to TNF to determine if it was a candidate for a mediator of ACD. Nude mice were inoculated with Chinese hamster ovary (CHO) cells expressing the human TNF gene or with control cells containing the transfection vector alone. The TNF mice promptly became reticulocytopenic, and after 3 weeks their corrected reticulocytes were 2.6% +/- 0.7% as compared with 7.3% +/- 4% in control mice. The hematocrit at 3 weeks was 28.4% +/- 1.7% in TNF mice as compared with 46% +/- 0.8% in control mice. This anemia was also associated with low serum iron and normal iron stores and increased erythropoietin (Epo) levels. The TNF mice showed an absolute monocytosis with twice the number of circulating monocytes as control mice and had M-colony-stimulating factor (CSF) activity in their serum. The TNF mice also became mildly thrombocytopenic. Marrow CFU-E and BFU-E were profoundly decreased (1.2 +/- 0.2 x 10(3) v 8.6 +/- 0.2 x 10(4) CFU-E per femur, and 6.5 +/- 1 x 10(2) v 8.5 +/- 0.2 x 10(4) BFU-E per femur). Splenic CFU-E and BFU-E were similarly depressed. In contrast, marrow CFU-GM and CFU-GEMM were not affected. The residual BFU-E in TNF mice were relatively resistant to TNF as compared with control mice. These data demonstrate that TNF preferentially inhibits erythropoiesis in vivo and may be important in the pathogenesis of ACD. 相似文献
946.
947.
948.
Transesophageal echocardiographic detection of gas embolism and cardiac valvular dysfunction during laparoscopic nephrectomy 总被引:4,自引:0,他引:4
Fahy BG Hasnain JU Flowers JL Plotkin JS Odonkor P Ferguson MK 《Anesthesia and analgesia》1999,88(3):500-504
We used transesophageal echocardiography (TEE) to monitor venous gas embolism, cardiac performance, and the hemodynamic effects of positioning and pneumoperitoneum in 16 healthy kidney donors undergoing laparoscopic nephrectomy. A four-chamber view was used continuously, except at predetermined intervals, when a complete TEE examination for cardiac function was performed. Other clinical variables recorded include systolic, diastolic, and mean arterial blood pressure; heart rate (HR), pulse oximetric saturations; and end-tidal CO2. Baseline valvular incompetence was seen in 13 of the 16 patients when supine and asleep. After positioning for surgery and induction of pneumoperitoneum, TEE revealed valvular incompetence with regurgitation more pronounced from baseline in 15 of the 16 patients. In one patient, during renal vein dissection, gas entered the right atrium from the inferior vena cava, worsening tricuspid regurgitation. Hemodynamic variables and ejection fraction were tested by using repeated-measures analysis of variance for significance (P < 0.05). Pneumoperitoneum increased (P < 0.05) systolic blood pressure (from 102.8 +/- 3.89 to 120.8 +/- 3.88 mm Hg) and HR (from 68.9 +/- 3.19 to 75.6 +/- 2.62). Ejection fraction was unchanged. The high incidence of valvular incompetence indicates that further studies are needed to assess these effects during laparoscopic nephrectomy with cardiac disease. IMPLICATIONS: Laparoscopic surgery has gained popularity as a procedure for the removal of donated kidneys. Although the insufflation of gas necessary for this relatively simple approach poses a low risk of venous air embolism, it may increase the risk of changes in valvular competency. 相似文献
949.
Effects of particle exposure and particle-elicited inflammatory cells on mutation in rat alveolar epithelial cells 总被引:20,自引:3,他引:20
Driscoll KE; Deyo LC; Carter JM; Howard BW; Hassenbein DG; Bertram TA 《Carcinogenesis》1997,18(2):423-430
To investigate mechanisms underlying development of lung adenomas and
carcinomas in rats exposed to poorly soluble particles the relationships
between particle exposure, inflammation and mutagenesis in rat alveolar
type II cells were characterized. Rats were exposed to saline or saline
suspensions of 10 and 100 mg/kg of alpha-quartz, carbon black or titanium
dioxide by intratracheal instillation. Fifteen months after exposure,
bronchoalveolar lavage (BAL) cells were characterized as to number and type
and lung histopathology performed. The alveolar type II cells were isolated
and cultured in 6 thioguanine (6TG) containing media to select for mutation
in the hprt gene. The potential contribution of lung inflammatory cells to
in vivo mutagenic responses, were evaluated by co-culturing BAL cells with
the rat alveolar epithelial cell line, RLE-6TN for 24 h and the RLE-6TN
cells selected for 6TG resistance. Neutrophilic inflammation was detected
in all rats exposed to 10 and 100 mg/kg of alpha-quartz and carbon black
and 100 mg/kg titanium dioxide; epithelial hyperplasia was observed in rats
exposed to 10 and 100 mg/kg of alpha-quartz and 100 mg/kg carbon black.
Hprt mutation frequency was increased in alveolar type II cells from rats
exposed to 10 and 100 mg/kg of alpha-quartz, 100 mg/kg carbon black and 100
mg/kg titanium dioxide. In vitro exposure of RLE-6TN cells to BAL cells
from rats treated with 10 and 100 mg/kg of alpha- quartz or 100 mg/kg
carbon black increased hprt mutant frequency. Both macrophage and
neutrophil enriched BAL cell populations were mutagenic to RLE-6TN cells,
however, the mutagenic activity appeared greatest for neutrophils. Addition
of catalase to BAL cell:RLE-6TN co-cultures inhibited the increase in hprt
mutation frequency. These studies demonstrate exposure of rats to doses of
particles producing significant neutrophilic inflammation is associated
with increased mutation in rat alveolar type II cells. The ability of
particle- elicited macrophages and neutrophils to exert a mutagenic effect
on epithelial cells in vitro supports a role for these inflammatory cells
in the in vivo mutagenic effects of particle exposure. The inhibition of
BAL cell-induced mutations by catalase implies a role for cell- derived
oxidants in this response.
相似文献
950.
目的:对比断冠再接与玻璃纤维桩联合树脂桩核修复应用于恒上前牙外伤冠折的修复疗效。方法:65例82颗青少年上前牙外伤冠折断冠后保留完整患牙病例,随机分为实验组41颗,应用玻璃纤维桩进行断冠再接,对照组41颗,用玻璃纤维桩联合树脂桩核冠修复,随访12个月,观察修复效果。结果:实验组1年成功率为97.6%,对照组1年成功率为92.7%。结论:断冠再接技术不但色泽外形上能与剩余牙体组织及邻牙匹配,且与复合树脂比较抗压强度更高,稳定性更好,操作方便,是修复上前牙外伤冠折患牙的有效方法。 相似文献