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41.
NP Shirodkar PS Chopra M Marker KD Murphy A Dhamoon OJ Kwon 《Canadian Metallurgical Quarterly》1997,21(5):340-345
In this study, we evaluated the permeation of piperacillin (PIPC), imipenem (IPM), amikacin (AKM), gentamicin (GM), ofloxacin (OFLX), levofloxacin (LVFX), ciprofloxacin (CPFX) and sparfloxacin (SPFX) through Pseudomonas aeruginosa biofilm with a simple new method. Bacteria used were a leucine-requiring mucoid mutant. Bacteria were grown on the membrane of a cell culture insert in chemically defined medium and incubated at 37 degrees C for 5 days. At days 0, 1, 3 and 5, the penetration rates through the biofilms were measured. PIPC and IPM demonstrated relatively high permeation both with penetration rates at day 5 of 50%, whereas AMK and GM, which are aminoglycosides, showed low permeation both with penetration rates after day 1 of less than 25%. Among the 4 fluoroquinolones, LVFX and SPFX demonstrated excellent permeation with penetration rates that reached 100% from day 0 to 5, while OFLX and CPFX showed almost the same permeation as IPM. This method of measuring penetration rates of antimicrobial agents through biofilm is very simple and useful for the evaluation of antibiotics against biofilm-forming bacteria. 相似文献
42.
BM de Rooij PJ Boogaard JN Commandeur NJ van Sittert NP Vermeulen 《Canadian Metallurgical Quarterly》1997,54(9):653-661
OBJECTIVE: To evaluate the use of urinary mercapturic acids as a biomarker of human exposure to allyl chloride (3-chloropropene) (AC). During three regular shut down periods in a production factory for AC, both types of variables were measured in 136 workers involved in maintenance operations. METHODS: Potential airborne exposure to AC was measured by personal air monitoring in the breathing zone. In total 205 workshifts were evaluated. During 99 workshifts no respiratory protection equipment was used. Mercapturic acid metabolites were measured in urinary extracts by gas chromatography-mass spectrometry (GC-MS). RESULTS: During 86 work shifts when no respiratory protection was used the air concentrations of AC were below the Dutch eight hour time weighted average (8 h-TWA) occupational exposure limit (OEL) of AC (3 mg/m3), whereas in 13 workshifts the potential exposure, as measured by personal air monitoring, exceeded the OEL (3.3 to 17 mg/m3). With the aid of GC-MS, 3-hydroxypropylmercapturic acid (HPMA) was identified as a minor and allylmercapturic acid (ALMA) as a major metabolite of AC in urine samples from the maintenance workers exposed to AC. The concentrations of ALMA excreted were in a range from < 25 micrograms/l (detection limit) to 3550 micrograms/l. The increases in urinary ALMA concentrations during the workshifts correlated well with the 8h-TWA air concentrations of AC (r = 0.816, P = 0.0001, n = 39). Based on this correlation, for AC a biological exposure index (BEI) of 352 micrograms ALMA/g creatinine during an eight hour workshift is proposed. In some urine samples unexpectedly high concentrations of ALMA were found. Some of these could definitely be attributed to dermal exposure to AC. In other cases garlic consumption was identified as a confounding factor. CONCLUSION: The mercapturic acid ALMA was identified in urine of workers occupationally exposed to airborne AC and the increase in ALMA concentrations in urine during a workshift correlated well with the 8 h-TWA exposure to AC. Garlic consumption, but not smoking, is a potential confounding factor for this biomarker of human exposure to AC. 相似文献
43.
MJ Lemmon P van Zijl ME Fox ML Mauchline AJ Giaccia NP Minton JM Brown 《Canadian Metallurgical Quarterly》1997,4(8):791-796
A fundamental obstacle in gene therapy for cancer treatment is the specific delivery of an anticancer gene product to a solid tumor. Although several strategies exist to control gene expression once a vector is directly introduced into a tumor, as yet no systemic delivery system exists that specifically targets solid tumors. Nonpathogenic, obligate anaerobic bacteria of the genus Clostridium have been used experimentally as anticancer agents because of their selective growth in the hypoxic regions of solid tumors after systemic application. In this report we further describe a novel approach to cancer gene therapy in which genetically engineered clostridia are used as tumor-specific vectors for the delivery of antitumor genes. We have introduced into a strain of C. beijerinckii the gene for an E. coli nitroreductase known to activate the nontoxic prodrug CB 1954 to a toxic anticancer drug. Nitroreductase produced by these clostridia enhanced the killing of tumor cells in vitro by CB 1954, by a factor of 22. To demonstrate the specificity of this approach for tumor targeting, we intravenously injected the inactive spore form of C. beijerinckii, which upon transition to a reproductive state will express the E. coli nitroreductase gene. Nitroreductase activity was detectable in 10 of 10 tumors during the first 5 days after intravenous injection of inactive clostridial spores, indicating a rapid transition from spore to reproductive state. Tumors harboring clostridial spores which did not possess the E. coli nitroreductase gene were devoid of nitroreductase activity. Most importantly, E. coli nitroreductase protein was not found in a large survey of normal mouse tissues following intravenous injection of nitroreductase containing clostridia, strongly suggesting that obligate anaerobic bacteria such as clostridia can be utilized as highly specific gene delivery vectors for cancer therapy. 相似文献
44.
It is not known whether a short loop feedback mechanism for the regulation of LH exists in sheep. This study on ovariectomized ewes investigated whether a bolus injection (10, 1, and 0.1 microg LH or 1 microg BSA; n 4) or a 3-h continuous infusion of exogenous LH (100 or 1 ng/min; n = 7) into the third ventricle through a permanent indwelling cannula could influence the activity of the GnRH pulse generator, as determined by measurement of endogenous LH secretion. To assess the potential for involvement in a LH short loop feedback system and to estimate the level of LH in the hypothalamic milieu, the concentrations of LH in the peripheral circulation, portal circulation, and third ventricle were measured during an estradiol-induced preovulatory LH surge (n = 4). Neither the bolus nor continuous administration of LH into the third ventricle had any effect on the mean interpulse interval, nadir, pulse amplitude, or circulating level of systemic LH. Furthermore, despite portal LH concentrations being more than 20-fold higher than jugular LH concentrations, LH levels in third ventricular cerebrospinal fluid remained barely detectable and did not reflect dynamic secretory events in the peripheral or hypothalamo-hypophyseal portal blood. These data demonstrate that in ewes, little pituitary LH reaches the third ventricle, and the small amount that does is unable to affect peripheral gonadotropin release. Our study suggests, therefore, that a short loop feedback system for LH does not exist in the ewe. 相似文献
45.
46.
TM Lovell RT Gladwell FJ Cunningham NP Groome PG Knight 《Canadian Metallurgical Quarterly》1998,139(3):1164-1171
Accumulating evidence implicates inhibins and activins as endocrine and local regulators of follicular development in mammals, and it was recently confirmed that inhibin/activin alpha and betaA genes are also expressed in the avian ovary. To investigate the potential involvement of these proteins in the chicken ovary, thecal and granulosa layers of the four largest follicles (F1-F4) and the most recent postovulatory follicle were collected from hens (10/group) killed 4, 12, and 20 h before the expected time of F1 ovulation. Inhibin A and activin A concentrations of tissue extracts (expressed per mg DNA) were measured using validated two-site enzyme-linked immunosorbent assays; total immunoreactive inhibin alpha-subunit (ir-alpha) was also measured by heterologous RIA (Monash assay). Inhibin A and ir-alpha were largely confined to the granulosa layer, whereas activin A was much more abundant in the thecal layer. Granulosa inhibin A contents were similar in F4 and F3, but increased approximately 40-fold from F3-F1 (P < 0.0001). As such, the F1 granulosa layer was by far the richest source of inhibin A in the chicken ovary, but contained very little activin A. Total ir-alpha in granulosa was much more abundant than inhibin A and increased only 3-fold from F4-F1 (P < 0.001). Activin A in both granulosa and theca showed little variation between F1 and F4 follicles (by ANOVA, P > 0.05). The inhibin A content of F1 granulosa was maximal 12 h before ovulation and had fallen approximately 6-fold (P < 0.0001) within 8 h, suggesting an inhibitory effect of the preovulatory LH surge on the F1 capacity to synthesize inhibin A. Inhibin A, activin A, and ir-alpha were all less in the postovulatory follicle compared with F1 before ovulation (P < 0.0001). In conclusion, application of the present two-site enzyme-linked immunosorbent assays to the chicken ovary revealed 1) divergent tissue distribution of inhibin A and activin A within preovulatory follicles, and 2) differential regulation of granulosa cell production of inhibin A and activin A dimers during preovulatory follicular development. These findings of dynamic changes in inhibin A, activin A, and total ir-alpha support the hypothesis that these proteins subserve regulatory roles during preovulatory follicular development in the hen. 相似文献
47.
Acute dystonia is a common adverse effect following anti-psychotic medication, which mainly appears shortly after beginning treatment or increasing the dosage. Laryngeal dysfunction may carely occur as part of the picture of acute dystonia and, if so, usually with dyspnoea. We describe a case of acute dystonia with atypical onset without relation to changes in dosage and with laryngeal involvement with aphonia, but without dyspnoea. 相似文献
48.
NP Chizhov 《Canadian Metallurgical Quarterly》1993,38(4-5):70-74
49.
50.
NP Ching J Lumeng R Pang G Pang FW Or NW Ching C Ching 《Canadian Metallurgical Quarterly》1998,57(12):735-739
The antiviral and immunomodulatory effects of interferon were assessed in the treatment of chronic Hepatitis C in multi-ethnic patients to prevent viral replication and chronic liver damage. Three million units of recombinant interferon alpha-2b were administered three times a week for 48 weeks to a group of 9 active Hepatitis C patients. A clinical response was defined as normalization of serum ALT values. Serum was frozen and stored for Hepatitis C viral assays. Four patients normalized their liver functions. When viral levels were measured only two patients had unmeasurable levels of HCV RNA after treatment. Therapeutic results were observed and much work needs to be done to improve therapy because a serious epidemic is predicted for the future. 相似文献