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991.
Whole-of-life tests of the C-nitroso compounds p-nitrosodimethylaniline (NDMA) and p-nitroso-diethylaniline (NDEA) have been completed in male rats and mice fed maximum tolerated doses continuously over the first halves of their respective natural lifespans. The chemicals were offered at a concentration of 300 mg/litre drinking fluid, but the doses of NDEA consumed were only 75% of the NDMA doses, in both species. Possibly because of this the results with NDEA were statistically not clear-cut, but there was a significant increase in tumour incidence after NDMA treatment in both species. The main sites of tumorigenesis after NDMA were lung, kidney and malignant lymphoma in the rats, and lung, duodenum and malignant lymphoma in the mice. The results confirm our own earlier experiment and provide the first evidence of oncogenic activity in this class of compounds.  相似文献   
992.
We report a case of a posterior fossa arteriovenous fistula (AVF) with bithalamic hyperintensity of MR images. The thalamic abnormality improved after surgery, suggesting reversible venous hypertension as the pathogenesis of the finding, as opposed to infarction. This manifestation of a posterior fossa AVF should be considered in the differential diagnosis of bilateral thalamic disease.  相似文献   
993.
994.
Photorefractive liquid crystals represent the newest class of photorefractive materials. The low electric fields required for reorienting liquid crystals, combined with their high birefringence, results in the observation of photorefractivity with very low optical intensities and low applied fields. Photoinducing efficient charge transport over macroscopic distances is the primary hurdle for producing the space-charge field required for photorefractivity.  相似文献   
995.
Although much information about firearm fatalities has been published, few articles have characterized all types of gunshot victims, the weapons used, and the injuries sustained in a well-defined geopolitical unit. This study of 597 persons sustaining gunshot injuries serious enough to cause death or hospitalization in Mobile County Alabama during 1985-1987, addresses that deficit. The overall rate of these 597 seriously gunshot-injured victims was 53/100,000 population per annum. Of the 597 victims, 215 died, resulting in a rate of 18.9 per 100,000 population per annum. Demographic characteristics of the homicide victims, predominantly young black men, and the suicide victims, predominantly middle-aged and elderly white men, are similar to those reported from other parts of the country. Assault victims accounted for the largest (316) number of victims: again, young black men also constituted the largest demographic group among assault victims. Handguns accounted for 71% of the weapons used. No assault type weapons were employed. Head, neck, and chest wounds led with the greatest fatality rates. Information about nonfatally wounded victims, particularly data about the weapons, proved difficult to obtain. This was one of the many problems encountered in this type of project and, consequently, is discussed at some length. Additional population-based studies using prospective methods and a variety of investigators, including persons knowledgeable of firearms, are needed.  相似文献   
996.
Biopsy specimens were obtained from 102 leprosy patients before chemotherapy and examined by polymerase chain reaction (PCR) using the primers amplifying the 372-bp DNA of a repetitive sequence of Mycobacterium leprae. The PCR results were then compared with bacterial indices (BI) of slit-skin smears and biopsy specimens. The intensities of DNA bands were in general correlated with the numbers of acid-fast bacilli, and even a sample with only one organism gave a PCR positive result. Ten 5-micron sections from each frozen tissue sample were pooled and processed for DNA preparation. PCR was positive for 11 (73.3%) of 15 biopsy specimens with BI of 0 determined for the paraffin sections from the same biopsy samples. PCR also gave positive results for 84 (96.6%) of 87 BI positive biopsy samples. Although the difference in overall results between the two methods was not statistically significant, PCR seemed to have an advantage over microscopic examination in detecting M. leprae in biopsy specimens negative for acid-fast bacilli. Further evaluation of PCR using more specimens from leprosy patients who are bacteriologically negative is warranted to ensure PCR's advantage over the conventional microscopic examination for the diagnosis of leprosy.  相似文献   
997.
Hydatid lung disease due to Echinococcus granulosus in the Canadian northwest and Alaska is often asymptomatic and usually benign. We reviewed the course and outcome of three children with giant hydatid lung cyst seen over a 2-year period. All were North American Indian children aged 9 to 12 years who presented with cough, fever, and chest pain. One had a rash. There was a history of exposure to domestic dogs who had been fed moose entrails in each case. Chest x-rays showed solitary lung cysts with air-fluid levels, from 6 cm to 12 cm in diameter. Aspiration of each cyst demonstrated Echinococcus hooklets and protoscolices. Serology was unhelpful, being negative in two cases. Transient pneumonitis and pneumothorax were seen as complications of needle aspiration. Two cysts gradually resolved over the following 6 months. One child returned after 9 months with a lung abscess due to superimposed infection of the cyst remnant with Haemophilus influenzae, and eventually required lobectomy. The existence of an endemic benign variant of E granulosus in Canada is not widely known, and it is important to distinguish it from the more aggressive pastoral form of the disease seen in immigrants from sheep-rearing countries. The native Canadian disease usually resolves spontaneously, does not cause anaphylaxis, and does not implant daughter cysts if spilled. Surgical treatment should be avoided except for complications such as secondary bacterial infection.  相似文献   
998.
In idiopathic dilated cardiomyopathy (IDC), the relation between the signal-averaged electrocardiogram and ventricular tachycardia (VT) remains unclear. In this study, conventional time domain and frequency domain analyses (2-dimensional, spectral temporal mapping and spectral turbulence analysis) of the signal-averaged electrocardiogram were performed in 64 patients with IDC. Eight patients had a history of symptomatic sustained VT and an additional 24 had nonsustained VT recorded during ambulatory electrocardiography. Conventional time domain analysis, using the 25 and 40 Hz filter, and spectral temporal mapping, detected late potentials within the terminal QRS in 8 (13%), 14 (22%) and 18 (28%) patients, respectively. Late potentials were seen more often in patients with than without VT, and in patients with sustained versus nonsustained VT, but these differences were not significant. The predictive accuracy of these techniques in detecting either form of VT were: sensitivity, 22, 25 and 31%; specificity, 97, 81 and 75%; and overall predictive value, 59, 53 and 50%, respectively. Two-dimensional frequency domain analysis of the signal-averaged electrocardiogram revealed a higher energy and area ratio in patients with than without VT (entire QRS), and in patients with sustained versus nonsustained VT (entire QRS and terminal QRS). Spectral turbulence analysis was abnormal in 24 patients (39%), but no differences were observed between patients with and without VT. During follow-up (mean duration 18 +/- 14 months), 5 patients had arrhythmic events (3 died suddenly, 1 had aborted sudden death and 1 developed sustained VT).(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
999.
Hypoxanthine, thymidine, and folinic acid protection from methotrexate cytotoxicity were compared in human lymphoid cell lines variably sensitive to thymidine-induced growth suppression. Hypoxanthine protection differed among the cell lines, and the dose-response relationship for protection occurred within the physiologic bone marrow hypoxanthine concentration range. The slopes of the thymidine protection curves were virtually superimposable in a B cell line versus a T cell line, but threefold to fourfold higher thymidine concentrations were required to maximally protect the B versus the T cell line. Thymidine (plus hypoxanthine) protection was superior to that of folinic acid in both the B and the T cell lines when protection was delayed. As the interval between methotrexate and folinic acid exposure was progressively delayed, there was a linear decline in the degree of maximum protection in both cell lines. However, as thymidine exposure was progressively delayed, maximal protection was maintained, except at 12 hours in the B cell line. The influence of methotrexate on thymidine-induced growth suppression was studied. Methotrexate enhanced thymidine-induced growth suppression in sensitive cells as manifested by a significant shift of the dose-response curve. Deoxycytidine protection from thymidine toxicity was superior in the presence of methotrexate. The results of these studies indicate that thymidine protection and folinic acid protection against methotrexate toxicity produce different effects, which in part are dependent on the cell type. The complexity of these interactions points out the need for further studies.  相似文献   
1000.
We have examined the role that individual TGF-beta isoforms, and in particular TGF-beta3, play in control of epidermal homeostasis. Mice with a knockout mutation of the TGF-beta3 gene die a few hours after birth. A full-thickness skin grafting approach was used to investigate the postnatal development and homeostatic control of the skin of these mice. Grafted skin of mice with a disruption of the TGF-beta3 gene developed similarly to grafts of wild type and TGF-beta1 knockout animals. However, a strikingly different response was observed after acute treatment with the tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA). When exposed to TPA, the grafted skin of wild type and TGF-beta1 knockout mice underwent a hyperplastic response similar to that of normal mouse skin. In marked contrast, TPA treatment of TGF-beta3 knockout grafts induced widespread areas of keratinocyte cell death. Analysis of cultured keratinocytes treated with purified TGF-beta isoforms revealed that TGF-beta3 plays a direct and specific function in protecting keratinocytes against TPA-induced cell death. The protective function of TGF-beta3 on TPA-induced cell death was not because of general suppression of the signaling pathways triggered by this agent, as ERK1/2 activation occurred to a similar if not greater extent in TGF-beta3-treated versus control keratinocytes. Instead, TGF-beta3 treatment led to a significant reduction in TPA-induced c-Jun N-terminal kinase activity, which was associated and possibly explained by specific counteracting effects of TGF-beta3 on TPA-induced disruption of keratinocyte focal adhesions.  相似文献   
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