Effects of 2,4,6-trinitrotoluene in a holistic environmental exposure regime on a terrestrial salamander, Ambystoma tigrinum.

2,4,6-Trinitrotoluene (TNT) is a defense-related environmental contaminant present at high concentrations in soil at some military installations. Tiger salamanders (Ambystoma tigrinum, family Ambystomatidae) were exposed to TNT in a soil matrix and fed earthworms that had also been exposed to TNT via contaminated soil. Such exposure was previously shown to result in significant accumulation of both TNT and TNT metabolites by salamanders. Following 14 days of combined oral and dermal exposures, salamanders were evaluated for signs of toxicity. Control and TNT-exposed salamanders gained weight (p < 0.025). In addition, organ to body weight ratios (kidney, liver, and spleen) were not affected by treatment. The function of splenic phagocytic cells was evaluated because these cells are sensitive to certain environmental chemical exposures. Neither the chemiluminescence response (H2O2 production) nor the phagocytic capacity of such cells were different between controls and treatment groups. In like manner, no changes were seen in the peripheral hematologic parameters investigated. Histopathologic evaluations were inconclusive, yet the liver revealed the presence of heavily pigmented iron-rich phagocytes (melanomacrophages). This investigation presents a realistic approach and preliminary data for investigating the effects of xenobiotic exposure in a soil matrix on a terrestrial vertebrate.

Intratracheal instillation of zinc-cadmium sulfide (ZnCdS) in Fischer 344 rats.

The purpose of this study was to assess the bioavailability and pulmonary toxicity of ZnCdS in rats. Groups of 30 male Fischer 344 rats each were anesthetized and dosed via intratracheal instillation with 5 mg of either ZnCdS, quartz (positive control), or titanium dioxide (TiO(2), negative control) suspended in 0.5 ml saline. A vehicle control group received 0.5 ml saline. Ten animals from each test group were sacrificed at 1 day, 1 wk, and 14 wk after dosing for bronchoalveolar lavage fluid (BALF) analysis and histopathology. The BALF was analyzed for alkaline phosphatase, acid phosphatase, lactate dehydrogenase (LDH), beta-glucuronidase (beta-glu), total protein, and cell counts. Two separate groups of 24 rats each were dosed as already described with either ZnCdS or saline. Eight rats from each group were sacrificed at 1 day, 1 wk, and 14 wk after dosing for determination of cadmium (Cd) and zinc (Zn) concentrations in the lung, liver, kidney, and blood. Results indicate that at 1 day after dosing, all enzyme activities (except acid phosphatase) and cell counts in BALF from the quartz and ZnCdS groups were significantly higher than in the TiO(2) and saline groups. At 7 days after dosing, high enzyme activity persisted in the quartz group, while the ZnCdS group showed only LDH and total protein levels significantly higher than the saline group. At 14 wk after dosing, LDH, total protein, beta-glu, and cell counts in the quartz group were significantly higher than all other groups. Histologic examination revealed interstitial inflammation and accumulation of foreign material in the lungs and mediastinal lymph nodes of quartz-, TiO(2)-, and ZnCdS-treated rats. Metal analyses in tissues showed profuse Cd and Zn concentrations in the lung 1 day after dosing, followed by a successive decline at 7 days and 14 wk after dosing. A very small, but statistically significant, amount of Cd and Zn was found in the kidneys at 14 wk after dosing. In conclusion, ZnCdS appears to cause temporary lung inflammation, is cleared slowly, and is poorly bioavailable.

Acute oral toxicity study of pyridostigmine bromide, permethrin, and DEET in the laboratory rat.

This study investigated the lethal interaction of pyridostigmine bromide (PB), permethrin, and DEET when given to adult male rats by gavage and was separated into two phases. Phase I determined the acute oral lethal dose-response relationship of each compound with the vehicle, propylene glycol. Phase II was divided into two portions: a dose-response study using probit units obtained from phase I [lethal dose (LD) 16, 30, 50, 70, and 84], and an interaction study that contained low levels (calculated LD16, additive LD32) of the two compounds while the concentration of the third compound was varied. Rats were fasted overnight, dosed, and observed for 14 d. A significant increase in lethality occurred when PB, permethrin, and DEET were given concurrently when compared to expected additive values. Furthermore, solutions containing PB and permethrin or PB and DEET also caused a significant increase in lethality when compared to expected additive values. This information suggests that lethality in this study was more than an additive effect.

Catecholamine concentrations and contractile responses of isolated vessels from hens treated with cyclic phenyl saligenin phosphate or paraoxon in the presence or absence of verapamil.

Blood samples and vascular segments from the ischiadic artery of hens treated with either cyclic phenyl saligenin phosphate (PSP; 2.5 micrograms/kg, im) or paraoxon (PXN; 0.1 micrograms/kg, im) in the presence or absence of verapamil, a calcium channel antagonist (7 micrograms/kg, im, given 4 consecutive days beginning the day before PSP or PXN administration), were examined 1, 3, 7, and 21 d after PSP or PXN administration in order to determine the contribution of catecholamines and peripheral blood vessel physiology and morphology to organophosphorus-induced delayed neuropathy (OPIDN). The levels of plasma catecholamines were measured by high-performance liquid chromatograpy (HPLC) and indicated a different effect with PSP, which causes OPIDN, and PXN, which does not. PSP treatment elevated the levels of norepinephrine and epinephrine throughout the study, while PXN treatment depressed the levels of these catecholamines. Verapamil treatment attenuated the OP response by approximately 50% for both compounds. Ischiadic vessel segments were isolated from OP-treated hens and perfused at a constant flow rate of 12 ml/min, then examined for their response to potassium chloride (KCl, 3 x 10(-3) M), acetylcholine (ACh), phenylephrine (PE), an alpha 1 adrenergic agonist, and salbutamol (SAL), a beta 2 adrenergic agonist. Agents were delivered in concentrations of 10(-8) to 10(-3) M. Vascular segments did not respond to ACh or SAL at any concentration used. Vessels displayed a significant reduction in contractile response to both KCl (3 x 10(-3) M) and PE (10(-8) to 10(-3) M) 3 and 21 d after exposure to either PSP or PXN. This reduced response was not altered by the presence of verapamil. Innervation of the peripheral vasculature was unchanged after OP treatment. This study indicates that plasma catecholamine levels could be differentially altered by treatment with OPs that do and do not cause OPIDN and suggests that the alterations involve intracellular calcium. In contrast, vascular response of the ischiadic artery was altered following OP treatment, but the effect was not specific for the neuropathy-inducing OP, PSP, and response was not mediated by Ca 2+, nor was it the result of autonomic nerve deterioration.

Effect of cyclic phenyl saligenin phosphate and paraoxon treatment on vascular response to adrenergic and cholinergic agents in hens.

The response of peripheral blood vessels to adrenergic and cholinergic agonists was examined 1, 3, 7, and 21 d after hens were treated with a single intramuscular injection of 2.5 mg/kg cyclic phenyl saligenin phosphate (PSP) or 0.10 mg/kg paraoxon (PXN). These two organophosphates (OPs) cause different clinical effects in exposed animals, as PSP causes organophosphate-induced delayed neuropathy (OPIDN) and PXN causes acute poisoning through inhibition of acetylcholinesterase. For these studies, the ischiadic artery was cannulated both prograde and retrograde and the blood was shunted through a pump to maintain a constant flow. Alterations in pressure measured at the pump outflow were used to indicate changes in limb vascular resistance. Dose-response curves were generated for the response to intravenous administration of acetylcholine (ACh), phenylephrine (PE), or salbutamol (SAL) (10(-8) to 10(-4) mol/kg). Acetylcholine at 10(-8) to 10(-7) mol/kg caused an increase in vascular resistance, whereas concentrations of 10(-5) to 10(-4) mol/kg caused a decrease in vascular resistance in hens given PSP 1 and 3 d previously. The response of PXN-treated hens to ACh was not significantly altered from that of vehicle-treated hens. The resistance generated in response to PE, an alpha 1-adrenergic agonist, in PSP-treated hens was greater than levels in vehicle-treated hens on d 1 and 3 and greater than the response seen in hens treated with PXN. Salbutamol, a beta 2-adrenergic agonist, at concentrations of 10(-7) to 10(-4) mol/kg caused an increase in resistance 1 and 3 d after PSP and a decrease on d 7. The responses to SAL were different in PXN-treated hens, as these hens demonstrated a lesser increase in resistance at concentrations of 10(-8) to 10(-7) mol/kg and a decrease in resistance at 10(-5) to 10(-4) mol/kg 1 d after administration of PXN. These observations indicate that response to vasoactive agents is altered in OP-treated hens and that responses differ between a compound capable of causing OPIDN (PSP) and a compound that only causes acute effects (PXN).

Furcation anatomy of the first mandibular molar in dogs.

Tooth surface and interradicular area (furcation) measurements were taken of 20 first mandibular molar teeth obtained randomly from canine cadavers. The lingual furcation entrance had a mean width of 1.2 +/- 0.3 mm. The buccal furcation entrance had a mean width of 1.3 +/- 0.4 mm. There was no significant difference between mean furcation entrance measurements. The horizontal attachment area between the cementoenamel junction and the coronal roof of the lingual furcation was 1.1 +/- 0.4 mm. The horizontal attachment area between the cementoenamel junction and the coronal roof of the buccal furcation (0.5 +/- 0.3 mm) was significantly different from the lingual horizontal attachment area. Distal root length and mesial root length were 16.0 +/- 1.5 mm and 16.1 +/- 1.6 mm, respectively. The mean coefficient of variation for variables measured was 14.0%. Tooth size did not have a significant effect on furcation entrance measurement. All teeth had a concavity coronal to the furcation area, which extended apically for a mean distance of 65.6% of the distal root length and 83.8% of the mesial root length. Furcation anatomy of the first mandibular molar is complex and may be a contributing factor in periodontal disease involving the interradicular area.

Adaptation of human oscillometric blood pressure monitors for use in dogs.

Two digital oscillometric human blood pressure measuring devices were modified and evaluated as blood pressure monitors in 12 healthy anesthetized dogs. Direct arterial pressures were measured via cannulation of the dorsal pedal artery and were correlated with indirect measurements through an inflatable cuff placed over the dorsal pedal artery below the hock joint of the contralateral limb. Direct and indirect measurements were compared for systolic, diastolic, and calculated mean arterial pressures. Blood pressure ranges between 215/145 mm of Hg and 65/30 mm of Hg were obtained, using combinations of halothane, phenylephrine, calcium, and IV administered fluids. Machine A was found to be insufficient for clinical application, on the basis of correlation coefficients between direct and indirect pressures of 0.78, 0.65, and 0.74 for systolic, diastolic, and mean arterial pressures, respectively. Higher correlation coefficients between direct and indirect pressures (0.77, 0.87, and 0.87, respectively) were obtained with machine B. The results of the study reported here suggest machine B may be an effective blood pressure monitoring device in anesthetized dogs.