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Toxic amblyopia following neonatal lead exposure: Alterations in central visual pathways
76 TOXIC AMBLYOPIAFULLDWINGNEONATAL LEAD EXPDSURE:ALTE~TIONS IN CEWTRAL VISUAL PATHWAYS.
FOX, D.A., IMPELMQN,D., LEAR, C.L. AND WILSON, R. COLLEGEOF OPTOWETRY,UNIV. HOUSTON,~USTON, TX, DIV. OF TOXICOLOGY,UNIV. OF TEXAS MEDIAL SCHOOL,HORTON, TX AND USOA-ARS-V~TERI~RYTOXICOLOGYAND ~TD~L~Y RESERRCH LABORATORY,COLLEGE STATION, TX. Reportsof childrenpoisoned by Pb describe irreversibledeficits in the spatial resolution propertiesof the visual system.To determine if visual acuity was altered in adult rats followingneonatal Pb exposure,pattern-reversalevoked corticalpotential (VECP)and psychophysicalstudieswere conductedin female Long-Evanshooded rats that were exposed to Pb (or no Pb) from ~rturit~on to weaning (days O-211 via the milk of dams consuming0.2% Pb acetate solutions(or water). VECPs were recorded in chronicallyimplanted,awake rats and used to estimate visual acuity. Psychometricfunctionswere obtained using sine-wave gratings in a conditionedsuppressionparadigm. In Pb-exposedrats visual acuity was decreased ZD-30% under mesopic conditionsand 40-55% under scotopicconditions.In addition to the decreasedamplitudeof the VECPs, which accounts for the spatial resolutiondecrement, increasesin the letenciesof the retinogeniculateand collicularresponseswere observed. These latter changesmay reflect decreasesin conductionvelocity (CV) and/or excitability (ch~naxy) of the optic nerve (ON} fibers.To examine this possibl'lty CVs and chronaxies were obtainedfor the three ON conductiongroups and recoveryfunctions (pre- and postsynaptic) were measured in electricallyevoked recordingsfrom the lateralgeniculatenuc,(dL.GN), superiorcolliculus (SC) and striate cortex (VC). In the Pb group, CVs of the fast conduction group were decreased (12%) while chronaxiesfor the fast and medium groups were increased (approx.50%). The recoveryof the postsynapticSC (optic chiasm stimulation)and VC (dLGN stimulation)responseswere depressed,while the dlGN responseswere not changed. The resultsshow that low-levelneonatal Pb exposure producesdecreasesin visual acuity (toxic~lyopia~ and reduces excitabilityand recoverabilityin the central visual pathways that mediate vision at high spatial frequencies,The decreasedexcitabiltyand CV contribute to the increasedVECP latencieswhile the depressedrecovery responsescontribute to the visual acuir:yloss. Supportedby ES 03183, ES 07090 and OH 07085.
A %&DAYI~A~~IO~~ STUDY OF HEAVY DISTILLATEFROM TUE SOLVENTREFINED COAL- (SRCf II PROCESS
SPRINGER,D.L., WAIILUM, D-D., MILLER, R.A., AND RAGAN, H.A. BIOLOGY AND CMHISTRY DEPAR~NT, PACIFICNOR~WEST HISTORY, RICH~D, WA 99352.
Even though high boiling coal liquids (>500'F) are biologicallyactive in in vitro assays and producetenors when applied continuouslyto mouse skin, the effects of these materialsfollowin inhalationexposurehave not been evaluated. To further the data base on potentialhealth effects of coal liquefaction,we have extended our efforts to include inhalationstudies. Fischer-344rats and CD-l mice were exposed 6 hrlday,5 daylwk for 13-weeksto an aerosol of heavy distillate,the 550~650*Ffractions. The average aerosol concentrationin the exposurechambers were 0.7, 0.14, 0.03, or 0.0 mg/L. Wean Particlesize in the exposure chambers ranged from 1.7-1.8@IImass median aero~n~ic diemeterwith a geumetricstandarddeviationof app~xi~tely 2.0. There was a dose dependent decreasein the rate of body weight gain, and the 0.7 mg/L dose group failed to gain weight during the 13-week exposure period. Even though body weight gain was severely retarded,94% of the male and 91% of the female rats survivedthe exposure period. Decreases in both red and whiitecells were present in blood samples taken after C-weeks of exposure; these resultswere confirmed in samples from animals after go-days of exposure,Evaluation of serum samples indicateddecreases in total protein, albumin,globulin,LDW, SGPT, and increasesin bilirubin,BUN, cholesterol.and triglyceridelevels. Significantincreases in liver weight for all three dose groups and decreases in thymus and ovary weightswere observedfor tissueweights taken at 6 and 13 weeks. Hfstopathologic evaluationwill also be reported. These data indicatethat inhalationexposure to heavy distillateproduces changes in growth, tissue weights, and blood parametersand demonstratesthe need for further eva~~tion of these materials. [Work supers by the U.S. &~~nt of Energy under ContractNo. DE-A~-76ffLD-l830}_
FOX, D.A., IMPELMQN,D., LEAR, C.L. AND WILSON, R. COLLEGEOF OPTOWETRY,UNIV. HOUSTON,~USTON, TX, DIV. OF TOXICOLOGY,UNIV. OF TEXAS MEDIAL SCHOOL,HORTON, TX AND USOA-ARS-V~TERI~RYTOXICOLOGYAND ~TD~L~Y RESERRCH LABORATORY,COLLEGE STATION, TX. Reportsof childrenpoisoned by Pb describe irreversibledeficits in the spatial resolution propertiesof the visual system.To determine if visual acuity was altered in adult rats followingneonatal Pb exposure,pattern-reversalevoked corticalpotential (VECP)and psychophysicalstudieswere conductedin female Long-Evanshooded rats that were exposed to Pb (or no Pb) from ~rturit~on to weaning (days O-211 via the milk of dams consuming0.2% Pb acetate solutions(or water). VECPs were recorded in chronicallyimplanted,awake rats and used to estimate visual acuity. Psychometricfunctionswere obtained using sine-wave gratings in a conditionedsuppressionparadigm. In Pb-exposedrats visual acuity was decreased ZD-30% under mesopic conditionsand 40-55% under scotopicconditions.In addition to the decreasedamplitudeof the VECPs, which accounts for the spatial resolutiondecrement, increasesin the letenciesof the retinogeniculateand collicularresponseswere observed. These latter changesmay reflect decreasesin conductionvelocity (CV) and/or excitability (ch~naxy) of the optic nerve (ON} fibers.To examine this possibl'lty CVs and chronaxies were obtainedfor the three ON conductiongroups and recoveryfunctions (pre- and postsynaptic) were measured in electricallyevoked recordingsfrom the lateralgeniculatenuc,(dL.GN), superiorcolliculus (SC) and striate cortex (VC). In the Pb group, CVs of the fast conduction group were decreased (12%) while chronaxiesfor the fast and medium groups were increased (approx.50%). The recoveryof the postsynapticSC (optic chiasm stimulation)and VC (dLGN stimulation)responseswere depressed,while the dlGN responseswere not changed. The resultsshow that low-levelneonatal Pb exposure producesdecreasesin visual acuity (toxic~lyopia~ and reduces excitabilityand recoverabilityin the central visual pathways that mediate vision at high spatial frequencies,The decreasedexcitabiltyand CV contribute to the increasedVECP latencieswhile the depressedrecovery responsescontribute to the visual acuir:yloss. Supportedby ES 03183, ES 07090 and OH 07085.
A %&DAYI~A~~IO~~ STUDY OF HEAVY DISTILLATEFROM TUE SOLVENTREFINED COAL- (SRCf II PROCESS
SPRINGER,D.L., WAIILUM, D-D., MILLER, R.A., AND RAGAN, H.A. BIOLOGY AND CMHISTRY DEPAR~NT, PACIFICNOR~WEST HISTORY, RICH~D, WA 99352.
Even though high boiling coal liquids (>500'F) are biologicallyactive in in vitro assays and producetenors when applied continuouslyto mouse skin, the effects of these materialsfollowin inhalationexposurehave not been evaluated. To further the data base on potentialhealth effects of coal liquefaction,we have extended our efforts to include inhalationstudies. Fischer-344rats and CD-l mice were exposed 6 hrlday,5 daylwk for 13-weeksto an aerosol of heavy distillate,the 550~650*Ffractions. The average aerosol concentrationin the exposurechambers were 0.7, 0.14, 0.03, or 0.0 mg/L. Wean Particlesize in the exposure chambers ranged from 1.7-1.8@IImass median aero~n~ic diemeterwith a geumetricstandarddeviationof app~xi~tely 2.0. There was a dose dependent decreasein the rate of body weight gain, and the 0.7 mg/L dose group failed to gain weight during the 13-week exposure period. Even though body weight gain was severely retarded,94% of the male and 91% of the female rats survivedthe exposure period. Decreases in both red and whiitecells were present in blood samples taken after C-weeks of exposure; these resultswere confirmed in samples from animals after go-days of exposure,Evaluation of serum samples indicateddecreases in total protein, albumin,globulin,LDW, SGPT, and increasesin bilirubin,BUN, cholesterol.and triglyceridelevels. Significantincreases in liver weight for all three dose groups and decreases in thymus and ovary weightswere observedfor tissueweights taken at 6 and 13 weeks. Hfstopathologic evaluationwill also be reported. These data indicatethat inhalationexposure to heavy distillateproduces changes in growth, tissue weights, and blood parametersand demonstratesthe need for further eva~~tion of these materials. [Work supers by the U.S. &~~nt of Energy under ContractNo. DE-A~-76ffLD-l830}_