Developmental Exposure to Aroclor 1254 Produces Low-Frequency Alterations in Adult Rat Brainstem Auditory Evoked Responses

Developmental exposure of Long—Evans rats to 0, 1, 4,or 8 mg/kg/day Aroclor 1254 (A1254) from Gestational Day 6 throughPostnatal Day 21 produces an elevated behavioral threshold fora 1-kHz tone. Brahistem auditory evoked responses (BAERs) wereassessed in a subset of these animals (about 1 year old) usingfiltered clicks at 1 (65 and 80 dB SPL), 4 (60 and 80 dB SPL),16 (40 and 80 dB SPL), and 32 (40 and 80 dB SPL) kHz. Aroclor1254 decreased BAER amplitudes at 1 and 4 kHz, but not at 16or 32 kHz. A dose-related decrease in the baseline-to-peak P_1Aamplitude was observed for the 1-kHz (80-dB) stimulus. Dosesof 1, 4, or 8 mg/kg/day A1254 decreased the peak-to-peak amplitudeof both P_1AN₁ and P_1BN₁ for a 1-kHz (80-dB) stimulus. Dosesof 4 and 8 mg/kg/day A1254 decreased the peak-to-peak amplitudeof N₁P₂ and P₂N₂ for a 4-kHz (60-dB) or 1-kHz (80-dB) stimulus.At 8 mg/kg/day, A1254 also increased the latency of peak P₄at 1 kHz (65 dB). The decreases in peak P_1A amplitudes are consistentwith a dysfunction of the cochlea and/or auditory nerve. Together,the data confirm that developmental exposure of rats to A1254produces a permanent low- to mid-frequency auditory dysfunctionand suggest a cochlear and/or auditory nerve site of action.     

Neuropathological Effects of Triphenyl Phosphite on the Central Nervous System of the Hen (Gallus domesticus)

The neurotoxic effects of single subcutaneous injections of1000 mg triphenyl phosphite (TPP)/kg body weight were investigatedin White Leghorn hens. At 7 days postexposure, birds began toshow signs of mild to moderate ataxia that progressed to severeataxia and paralysis at 21 days. Inhibition of whole brain neuropathytarget esterase was 85% at 48 hr and 73% by 21 days postexposure.After postexposure periods of 7, 14, and 21 days, hens werekilled and their brains and spinal cords were examined for degeneratingaxons and terminals using the Fink-Heimer silver impregnationmethod. A small amount of degeneration was noted at 7 days.By 21 days, dense degeneration was noted in the spinal graymatter and funiculi. Degeneration was also present in the granularcell layer of cerebellar folia I-VI and in nuclei and fibertracts of the medulla. Moderate to dense degeneration was alsoseen in several forebrain and midbrain areas including the paleostriatum,ansa lenticularis, the dorsointermediate thalamic nucleus, lateralspiriform, pedunculopontine tegmental, and lateral mesencephalicnuclei and in the deeper layers of the optic tectum. These resultsindicate that, in addition to affecting the spinal cord andbrainstem, exposure to TPP also damages higher order centersresponsible for processing and integrating sensorimotor, visual,and auditory information.     

Acoustic Stimuhtion-induced Fetal Response Compared to Traditional Nonstress Testing

Eighty-eight nonstress tests (NSTs) were obtained on gravid women between 27 and 44 weeks' gestation to compare the results of a three-second acoustic stimulus with a traditional NST. Length of testing time was significantly decreased with the use of acoustic stimulation. Consequently, nursing time and equipment use were also considerably lessened per test. Previous studies indicated that the predictive value of the acoustic stimulation test is comparable or better than the traditional NST.     

Waldenstrom's Macroglobulinemia: Correlation Between Expanded Plasma Volume and Increased Serum Viscosity

In 17 patients with Waldenström’s Macroglobulinemia, total chromiumspace, red cell mass, plasma volume and relative serum viscosities were determined; aldosterone excretion was determined in 12. Ten of the 15 patients whomanifested elevated serum viscosity at some time during the course of studypresented signs and symptoms of hyperviscosity syndrome. All patients had increased total blood volume. Fifteen had moderate decreases in red cell massbut all had elevations of plasma volume far in excess of that required to compensate for the lowered cell mass. The degree of the increase in plasma volumecorrelated (r = 0.74) with the degree of abnormality in relative serum viscosity. Aldosterone excretion in such patients was normal to low. It is concluded that the plasma volume increase is correlated with serum viscosity andis mediated by sodium retention mechanisms not involving modification ofaldosterone secretion.