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排序方式: 共有263条查询结果,搜索用时 15 毫秒
1.
J. J. KEUR J. P. S. CAMPBELL J. F. McCARTHY W. J. RALPH 《Journal of oral rehabilitation》1987,14(2):183-191
A sample consisting of 1135 edentulous patients with clinically healthy denture bearing areas, was examined radiologically. It appears that the diagnostic yield is high whereas the expected radiation induced risk is low. Patients should therefore be examined radiologically prior to full denture construction. 相似文献
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3.
A Critical Period of Ventricular Fibrillation More Susceptible to Defibrillation: Real-Time Waveform Analysis Using a Single ECG Lead 总被引:1,自引:0,他引:1
PENG-WIE E. HSIA SYLVIA FRERK CYNTHIA A. ALLEN ROBERT M. WISE NERI M. COHEN RALPH J. DAMIANO Jr . 《Pacing and clinical electrophysiology : PACE》1996,19(4):418-430
Previous studies have suggested that variations in the underlying ventricular fibrillation (VF) waveform may be one of the factors responsible for the probabilistic nature of defibrillation. The heart appeared to be more susceptible to defibrillation at higher absolute VF voltages (AVFV). This study investigated in an open-chest canine model (n = 8), a newly developed system that analyzed the VF waveform in real-time, instantaneously determined the time to shock, and immediately delivered a fixed low energy DC shock. A two parameter tracking technique using a running long-term and short-term AVFV average was devised to automatically identify a high voltage peak area of the VF waveform, which has been hypothesized to represent a critical period susceptible to defibrillation. Using a DC shock estimated at the 50% success level, the performance using this technique in 58 defibrillation trials was compared to the performance of the conventional method of shocking at a fixed time (random shock method) in 62 trials. Patch size, electrode location, and discharge voltage were kept constant while VF duration, transmyocardial resistance (TMR), energy delivered, and AVFV at the point of shock were measured. Shock energy and current, TMR, and VF duration were similar with both shock methods. A significantly higher AVFV was observed for trials performed with the peak shock method (0.66 ± 0.02 mV) as compared to trials performed with the random shock method (0.25 ± 0.09 mV) (P < 0.003). Using lead II as the only sensing lead, the success rate was increased in 6 of 8 dogs (75%) with the new method. One animal showed identical performance, and one animal a worse performance. The overall increase in success rate was 24% using a single ECG lead (range 0%-100%; P < 0.04). Our data document that using this algorithm a period of high VF voltage can be detected in realtime. The improved success in the majority of animals supports the hypothesis that a critical period susceptible to defibrillation exists during VF. However, the high AVFV detected using a single ECG lead did not translate to an improved success rate in all animals. This suggests that other factors in addition to the VF voltage measured on a single lead of the ECG are important in characterizing this critical period. 相似文献
4.
H-Reflex Waveform and Latency Variability in Rats. MATTSSON,J. L., ALBEE, R. R., AND BRANDT, L. M. (1984). Fundam. Appl.Toxicol. 4, 944948. The right tibial nerve of each of11 anesthetized male Fischer 344 rats was electrically stimulatedat the ankle, and H-reflexes were recorded simultaneously fromfour locations in the hind foot. Needle electrodes were usedfor stimulating and recording. The mean (±SD) latencyto the dominant peak of the H reflex was 10.21 ± 0.75msec. Individual rats had a 10% difference in latency from the"fastest" to the "slowest" locations in the foot, although anyof the four locations could produce the fastest (shortest latency)response. The H reflexes varied from simple, single peak waveformsto complex multiple peak waveforms. The dominant peak polaritywas unpredictably either positive or negative. These variationsin complexity and latency occurred among rats and among thefour locations within an individual rat. The dominant peak wasidentified in complex waveforms by adjusting the stimulatingintensity and by recording from more than one location in thefoot. The smallest coefficient of variation (5.57%) resultedfrom selecting data from the fastest electrode locations. 相似文献
5.
SCHOENIG GERALD P.; HARTNAGEL RALPH E. JR.; SCHARDEIN JAMES L.; VORHEES CHARLES V. 《Toxicological sciences》1993,21(3):355-365
The neurotoxic potential of N,N-diethyl-m-toluamide (DEET) wasevaluated following acute oral administration or following multigenerationplus chronic dietary administration to the rat. For the acutestudy, rats were administered undiluted DEET at dose levelsof 50, 200, or 500 mg/kg by gavage. A dose level of 500 mg/kgwas considered to be the highest practical dose that could beevaluated in this study based upon observations of overt toxicityat 500 mg/kg and mortality at 1000 mg/ kg in a dose range-findingstudy. The two measures of neurotoxicity evaluated in the acutestudy were functional observational battery (FOB) and motoractivity measurements. An apparent treatment-related effectin thermal response time (increased) was noted for both sexes1 hr after dosing at the 500 mg/kg dose level. A questionableeffect on rearing activity (decreased) also was noted at thesame dose level. For the multigeneration plus chronic dietaryadministration study, rats were administered DEET at dietaryconcentrations of 0, 500, 2000, or 5000 ppm continuously overtwo generations and then chronically for 9 months. A dietaryconcentration of 5000 ppm meets the criteria for a maximum tolerateddose (MTD) based on traditional chronic toxicology assessments.Evaluations included FOB, motor activity, discriminative acquisitionand reversal in an Mmaze, acoustic startle habituation, passiveavoidance acquisition and retention, and microscopic examinationof central and peripheral nervous tissue. The only effect thatwas considered to be possibly treatment-related was a slightincrease in exploratory locomotor activity at the 5000 ppm doselevel. Based on the results of these studies, the nervous systemdoes not appear to be a selective target when DEET is administeredto rats either as a single oral dose at high dose levels orchronically at the MTD. 相似文献
6.
Acute Spermatogenic Effects of Bromoacetic Acids 总被引:6,自引:3,他引:3
LINDER RALPH E.; KLINEFELTER GARY K.; STRADER LILLIAN F.; SUAREZ JUAN D.; DYER CHERYL J. 《Toxicological sciences》1994,22(3):422-430
Chlorine and bromine can react with natural organic substancesin source waters to form haloacetic acids, major disinfectionby-products of water chlorination. Several toxic effects includingtesticular damage have been attributed to the chloroacetic acidsbut little information is available on the bromine analogues.In this report we present the results of acute toxicity andacute spermatotoxicity studies of monobromoacetic acid (MBAA)and dibromoacetic acid (DBAA). In adult male rats the acuteoral toxicity of MBAA was 10-fold that of DBAA (LD50 177 vs1737 mg/kg). No reproductive-related endpoints were affectedin rats given a single dose of 100 mg MBAA/kg or 14 daily dosesof 25 mg MBAA/kg/day. In rats dosed with DBAA, serum testosteronefell to 17% of control 2 days after a single dose of 1250 mg/kgbut returned to control levels by Day 14. Marked effects onsperm motion were seen on post-treatment Days 14 and 28. Degenerativeflagellar changes in cauda sperm were present on Day 14 whileabnormal sperm head shapes and flagellar degeneration were observedin both caput and cauda sperm on Day 28. Histopathology indicatedaltered spermiation at all timepoints as evidenced by retentionof Step 19 spermatids beyond Stage VIII of the cycle of theseminiferous epithelium. Disorganization, distortion, and degenerationof late spermatids were also observed. On Day 14 structuresresembling residual bodies were rarely seen in the testis butwere numerous in the epididymis. Caput sperm counts were decreased on Day 2 and cauda sperm counts were decreased on Days14 and 28. The data indicate that DBAA is a testicular toxicantin the rat with late and elongating spermatids being particularlysusceptible germinal cells. 相似文献
7.
Absorption, Metabolism, and Excretion of N,N-Diethyl-m-toluamide Following Dermal Application to Human Volunteers 总被引:1,自引:0,他引:1
SELIM SAMI; HARTNAGEL RALPH E. JR.; OSIMITZ THOMAS G.; GABRIEL KARL L.; SCHOENIG GERALD P. 《Toxicological sciences》1995,25(1):95-100
The absorption, metabolism, and excretion of N,N-diethyl-m-toluamide(DEET) in male human volunteers following dermal applicationof |14C|DEET was studied. DEET was applied to two groups ofsix volunteers either as the undiluted technical grade materialor as a 15% solution in ethanol. The material was applied overa 4 x 6-cm area on the volar surface of the forearm and wasleft in contact with the skin for 8 hr, then rinsed off theskin. Application sites also were tape stripped at 1, 23, and45 hr after rinsing. Serial blood samples and all urine andfeces were collected for 5 days after application. Aliquotsof these materials were analyzed for total radioactivity inorder to define absorption and excretion patterns. Urine samplesalso were analyzed by HPLC to characterize the metabolic profileand/or to identify metabolites. Absorption of DEET as evidencedby plasma radioactivity occurred within 2 hr after dose application.Elimination of radioactivity from plasma was rapid and quantifiablelevels of radioactivity were observed in plasma for only 4 hrafter the end of the 8-hr exposure period. Urine was the principalroute of excretion of radioactivity and accounted for an averageof 5.61 and 8.33/ of the applied dose in the undiluted DEETand 15/ DEET in ethanol groups, respectively. Excretion of radioactivityin the feces was less than 0.08/ of the applied dose in bothgroups. DEET did not accumulate in the superficial layers ofthe skin as evidenced by low amounts of radioactivity in thetape strippings. The major fraction of the applied radioactivitywas recovered in the skin rinses. Absorbed DEET was completelymetabolized and six major metabolites were observed in urine.Two major urinary metabolites tenta tively were identified.Based upon the percentage of applied dose recovered in the excreta,dermal absorption of DEET ranged from 3 to 8% with a mean of5.6/ in the volunteers applied undiluted technical grade DEET.The corresponding values for the volunteers applied 15/ DEETin ethanol were 4 to 14/ and 8.4/, respectively. 相似文献
8.
HESS REX A.; MOORE B. J.; FORRER JANET; LINDER RALPH E.; ABUEL-ATTA AHMED AWAD 《Toxicological sciences》1991,17(4):733-745
The Fungicide Benomyl (Methyl 1-(Butylcarbamoyl)-2-benzimidazolecarbamate)Causes Testicular Dysfunction by Inducing the Sloughing of GermCells and Occlusion of Efferent Ductules. HESS, R. A., MOORE,B. J., FORRER, J., LINDER, R. E., ABUEL-ATTA, A. A. (1991).Fundam. Appl. Toxicol 17, 733745. Adult male Sprague-Dawleyrats (100 days of age) were given single oral doses of the fungicidebenomyl (methyl 1-(butylcarbamoyl)-2-benzimidazolecarbamate)in dosages ranging from 25 to 800 mg/kg body weight. The testisand excurrent ducts were examined at 2 and 70 days posttreatmentto determine the chemical effects on spermatogenesis and theepididymis. Primary effects seen at 2 days postexposure weretesticular swelling and occlusions of the efferent ductules.Mean testis weight peaked with 400 mg/kg. Premature releaseof germ cells (sloughing), detected even with the lowest dosage(25 mg/kg), was the most sensitive short-term response to benomyl.Sloughing was found primarily in Stage VII of the spermatogeniccycle at the lower dosages, but at higher dosages sloughingextended into all stages except for Stages VIII-XI. Occlusionsof the efferent ductules of the testis were dose-dependent andcorrelated with testis weight. Sperm and sloughed germ cellswere compacted in the ductal lumen of occluded ductules, whichwere surrounded by two to four layers of polymorphonuclear leukocytesand other inflammatory cells. Although the caput epididymidiscontained sloughed germ cells and appeared swollen, evidenceof permanent occlusion was not found. The long-term (70 days)effects of benomyl were decreased testis weight (at 400 mg/kg),dose-dependent increases in seminiferous tubular atrophy, andincreases in the number of reproductive tracts containing occludedefferent ductules. Fibrosis, granulomas, and abnormal growthwere long-term consequences of occluded ductules, which werepresent 100% of the time in testes containing 26100%seminiferous tubular atrophy. Only a few testes were found tobe completely regressed. Occlusion of efferent ductules anddisruption of the seminiferous epithelium by sloughing of germcells are overlapping dose-dependent mechanisms responsiblefor short- and long-term effects of benomyl on the rat testis. 相似文献
9.
GRODIN WARREN K.; EPSTEIN Mary Anne F.; EPSTEIN RALPH A. 《British journal of anaesthesia》1982,54(5):561-565
Using fresh soda-lime (15% water by weight) the soda lime/airpartition coefficient of halothane was found to decrease asa function of vapour phase halothane concentration from 2 40at 0.3% halothane by volume to 1.15 at 2.6percnt;, but adsorptiongenerally followed Henry's law. However, soda-lime dried toa constant weight and subsequently exposed to various concentranonsof halothane adsorbed approximately 320 µlitre of vaporizedliquid halothane per 100 g before a measurable concentrationof halothane was detected in the vapour phase. Adding additionalhalothane then caused a linear increase in vapour concentration.We conclude that dry soda-lime can adsorb large quantities ofhalothane by a mechanism which is nimilar to that of a molecularsieve. After these "high affinity" sites are satisfied, additionalhalothane is adsorbed by a mechanism following Henry's law. 相似文献
10.