An autoradiographic study of the renewal of mouse bronchiolar epithelium following bromobenzene exposure

We report an experimental model of germanium dioxide (GeO2)-induced neuropathy in rats. More than 6 months administration of GeO2 to young rats produced neuropathy characterized by segmental demyelination/remyelination and nerve edema. Electron microscopic studies demonstrated that changes in Schwann cells, such as an increased cytoplasmic volume or disintegration of the cytoplasm, were the earliest pathological findings. Schwann cell mitochondria contained high electron-dense materials. Subsequent removal of necrotic Schwann cell debris and myelin by invading macrophages was evident. These findings suggested that the Schwann cells themselves are the primary target of the toxin. The deposition of electron-dense granules in the intra-axonal vesicles, which was suggestive of glycogen granules in mitochondria, was observed in the advanced stage of the neuropathy. The findings of endoneurial edema with splitting of myelin lamellae were noted at the early stage of demyelination. Nerve edema may be the result of GeO2-induced endothelial cell injury.     

Comparative presynaptic neurochemical changes in rat striatum following exposure to chlorpyrifos or parathion

We recently demonstrated that posttraumatic administration of the N-type calcium channel blocker SNX-111 (S) and a novel blood-brain barrier penetrating antioxidant U-101033E (U), significantly alleviated mitochondrial dysfunction induced by traumatic brain injury (TBI) in rats. The present study was designed to determine whether a combination of S and U, which act on different biochemical mechanisms of secondary brain injury, would be more efficacious than either drug alone. Brain mitochondria from injured and uninjured hemispheres were isolated and examined at 12 h post TBI induced by a severe controlled cortical impact injury. S at 1.0 mg/kg significantly increased both State 3 and 4 rates and produced a slight increase in P/O ratio, and there was virtually no change in RCI. U at 1.0 mg/kg did not show any protection. However, the combined treatment of S at 1.0 mg/kg and U at 1.0 mg/kg eliminated the uncoupling effect of S, and restored not only State 3 rates and P/O ratios but also RCI to near sham values. These results provide further evidence that both reactive oxygen species and perturbation of cellular calcium homeostasis participate in the pathogenesis of TBI-induced mitochondrial dysfunction, and support the idea of using combined therapy with lower drug doses.     

Observation of ultrastructural changes in cultured retinal pigment epithelium following exposure to blue light

BACKGROUND: The retina can be damaged by light even when levels of energy are well below the threshold for thermal damage, and the experimental damage of the retinal pigment epithelium (RPE) may be induced more easily by blue light than by longer wavelengths of visible light. The present study demonstrates the ultrastructural damage produced by exposure to blue light in cultured RPE. METHODS: Long-Evans rats were enucleated 8-10 days after birth for primary culture. One week after seeding, the monolayer culture of RPE cells was exposed to a cool blue light (wavelength = 440 +/- 10 nm) for 36 h (12 h/day, 3 days) at 2.0 mW/cm2. Transmission electron microscopy was used to compare the exposed RPE with the control. The entire experiment was repeated 3 times independently. RESULTS: The cytoplasm of the exposed RPE exhibited degenerative changes, such as large whorls of membrane, lamellar whorls and whorled inclusions. CONCLUSION: The RPE cells can be damaged directly by blue light after excluding the possible influence of phagosomes. This primary culture of RPE can also serve as an in vitro model for the study of light damage to the RPE.     

Luminol chemiluminescence in rat macrophages and granulocytes: the role of NO, O2-/H2O2, and HOCl

Luminol chemiluminescence was increased up to five-fold by L-arginine and markedly inhibited by NG-nitro-L-arginine (L-NNA) in phorbol ester (PMA) or opsonized zymosan-activated rat Kupffer cells, and in PMA-activated rat peritoneal and alveolar macrophages. While in Kupffer cells these effects did occur without pretreatment with lipopolysaccharides (LPS), LPS pretreatment was a requirement in peritoneal and alveolar macrophages. Azide (0.05 mM) had no effect on luminol chemiluminescence in the macrophages. The changes in luminol chemiluminescence were accompanied by parallel changes in nitric oxide (NO) formation. Macrophage superoxide anion radical (O2-) production was not significantly changed by addition of L-arginine and L-NNA nor by pretreatment with LPS. No hypochlorous acid (HOCl) formation was detectable in the macrophages. In contrast, in rat granulocytes activated by a variety of stimuli including PMA, zymosan, the chemotactic peptide formyl-methionyl-leucyl-phenylalanine and the calcium ionophore A23187 with or without pretreatment with LPS, L-arginine and L-NNA had no effect on luminol chemiluminescence. Luminol chemiluminescence, however, was largely inhibited by 0.05 mM azide. The activated granulocytes released significant amounts of HOCl but did not generate NO. These results demonstrate that NO may largely contribute to luminol chemiluminescence in rat macrophages, in which HOCl formation does not occur. On the other hand, HOCl is the reactive oxygen species responsible for luminol chemiluminescence in rat granulocytes, where NO is formed only in minor quantities, if at all.     

Sensory gating deficit following cocaine exposure in the rat

In order to determine the prevalence of malaria and its epidemiological characteristics, a survey was carried out in 11 villages situated in all the Basin of River Senegal (B.R.S.). 3306 (0-14 years) children are examined. The results show that malaria is hypo-endemic in the B.R.S. with a plasmodic index of 8.6% and a splenic index of 9.9%. But these malariametric indexes change according to the areas visited. Thus, malaria prevails at a hypo-endemic level in Dagana and Podor districts while at a medium if not hyperendemic level in Matam and Bakel districts. The plasmodial index also change according to age reaching a maximum within children from 10 to 14 years. As for the spleen index, it is low among children from 10-14 years. As for the spleen index, it is low among children from 0 to 4 years old, then increases among those aging from 5 to 9 years, before decreasing within children ranging from 10 to 14 years. P.falciparum is the most prevalent species, representing 96% of the cases; it is followed by P.malarioe (3%) and P.ovale (1%). If our results are compared with those obtained before by other authors, we can conclude that the recent hydro-agricultural plannings carried out in the area, have not yet provoked an increase of the cases of malaria. But, in order to avoid this risk, it is necessary to take from now some preventive measures.     

Physiologic regeneration of corneal epithelium following exposure to constant magnetic fields of super-high intensity]

The mitotic index of mouse corneal epithelium was studied during and after 0.5-- 24 hours exposures to 9.9-39.4 kilooersteds constant magnetic fields. It was shown that 0.5, 1 and 3 hours exposures to a 39.4 kilooersteds constant magnetic field inhibited the mitotic activity whereas 8 and 24 hours exposures caused its stimulation. The value and rate of mitotic index alterations decrease with a decrease of field strength. No changes were found in the frequency of aberrant mitoses or in the number of cells per one field of microscopic vison.     

Study on analysis of crystal structure in CeO2 doped with Er2O3 or Gd2O3

To simulate the effects of burnable poison doping in nuclear fuel UO₂, Er₂O₃ (or Gd₂O₃)-doped CeO₂ pellets were prepared. Changes in lattice constant and atomic disordering for CeO₂ due to the Er₂O₃ and Gd₂O₃ doping were measured by means of XRD and XAFS. By the Er₂O₃ doping, the lattice constant decreased, and a disordering of lattice structure was induced in the samples. The doping with Er₂O₃ also induced the disordering of atomic arrangement around Er atoms, which was observed through the change in XAFS spectra. In contrast, the effect of Gd₂O₃ doping was smaller than that of Er₂O₃ doping. The result was discussed in terms of ionic size of dopants in CeO₂ crystal.     

Long-lasting increased pain sensitivity in rat following exposure to heroin for the first time

Acute dependence, defined as a precipitation of somatic signs by an antagonist, may occur after a single administration of an opiate drug. Because hyperalgesia is a consistent sign of the withdrawal syndrome, we tested the effectiveness of heroin, an opiate used by addicts, to induce pain facilitation even after a first exposure to the drug. In opiate-naive rats, subcutaneous injection of heroin induced analgesia followed by allodynia, a decrease in pain threshold. This latter phenomenon was observed in the absence of noxious stimuli and lasted several days. An N-methyl-D-aspartate (NMDA) receptor antagonist, MK-801 prevented such long-lasting allodynia. These results suggest that allodynia is an early sign reflecting neural plasticity associated with the development of dependence.     

Dissolution of carbon dioxide in CaO-CaF2-Al2O3 based melts containing Na2O or K2O oxide

The influence of Na₂O or K₂O on the solubility of CO₂ in CaO-CaF₂-Al₂O₃ based melts is measured by a thermogravimetric technique over a temperature range of 1250–1350°C. The values of the carbonate capacities (C'_c = wt. % ) are calculated by data on the dissolution and partial pressure of carbon dioxide. The replacement of CaO by Na₂O leads to an increase of the carbonate capacity to a maximum at 3–3.5 wt. % Na₂O and then to a decrease. The addition of Na₂O or K₂O up to 2 wt. %, to CaO-CaF₂-Al₂O₃ increases the carbonate capacity at 1300°C by 30%.     

Repair of O6-methylguanine in rat pancreatic beta-cells after exposure to N-methyl-N-nitrosourea

Because of the possible involvement of O6-methyldeoxyguanosine as a cytotoxic and carcinogenic lesion in pancreatic beta-cells, studies were undertaken to assess the ability of rat beta-cells to repair this DNA lesion. Primary cultures of neonatal rat beta-cells were shown to contain very low levels of O6-methylguanine-DNA-methyltransferase activity, the predominant mechanism for repairing O6-methyldeoxyguanosine in mammalian cells. However, using a 32P-endlabeling assay to measure O6-methyldeoxyguanosine in cells after exposure to N-methyl-N-nitrosourea, it was determined that rat beta-cells repaired O6-methyldeoxyguanosine to a substantial extent over a 24-h period. To elucidate the mechanism of O6-methyldeoxyguanosine repair in the virtual absence of constitutive O6-methylguanine-DNA-methyltransferase expression, studies were performed to determine if O6-methylguanine-DNA-methyltransferase expression was enhanced in N-methyl-N-nitrosourea-treated beta-cells. No increase in O6-methylguanine-DNA-methyltransferase activity was detected 24 or 48 h after exposure. However, Northern blot analysis showed a two- to threefold elevation in O6-methylguanine-DNA-methyltransferase messenger RNA levels in beta-cells 12 and 24 h after N-methyl-N-nitrosourea treatment. This finding is the first demonstration of a change in O6-methylguanine-DNA-methyltransferase messenger RNA levels in a cell type with low constitutive activity.     

Pathways mediating Ca2+ entry in rat cerebellar granule cells following in vitro exposure to methyl mercury

Metastatic disease is the most common cause of malignant liver lesion in the United States. This article focuses on the MR techniques utilized for evaluation of the liver for metastatic disease, the MR appearance of hepatic metastases, and several contrast agents being developed to further improve detection of focal hepatic lesions by MR imaging.     

Interactions in the Al2O3-ZrO2-Y2O3 system

The phase diagram of the Al₂O₃-ZrO₂ system was replotted over a broad range of concentrations (0–100 mole %) and temperatures (1150–2800°C). The polymorphic transformation of zirconium F ? T occurs via the metatectic reaction F ? T + L at 2260°C. Phase triangulation was employed to plot the diagrams of the partially quasibinary sections in the Al₂O₃-ZrO₂-Y₂O₃ system. Since there is a wide solubility range based on ZrO₂ in the binary ZrO₂-Y₂O₃ system, the triangulation conodes are displaced in the F-solid solution corners. The two-phase regions Y₃A₅-F are quite broad. The reactions in all three are of the eutectic type. The ternary solid solution fields in the Al₂O₃-ZrO₂-Y₂O₃ system had no observable width.     

Interdiffusion in the MgO-Al2O3 spinel with or without some dopants

With a view to seek an improved understanding of the DIMOX process, interdiffusion of polycrystalline MgO and Al₂O₃ in the temperature range 1473 to 1873 K was studied by diffusion couple experiments. The interdiffusivities in the spinel layer were calculated as functions of composition and temperature. The spinel portion of the phase diagram in the system MgO-Al₂O₃ was determined from carefully measured compositions at the phase boundaries, and the low temperature spinel region of the phase diagram was confirmed from the present results. For Zn²⁺ as dopant in alumina, the growth rate of spinel thickness seems to increase when compared with that of the diffusion couples without dopant. The samples containing Si⁴⁺ as dopant reveal the formation of a glass phase, and the effect of Si⁴⁺ on the diffusion process appears to be negligible. This article is based on a presentation made in the “n Situ Reactions for Synthesis of Composites, Ceramics, and Intermetallics” symposium, held February 12–16, 1995, at the TMS Annual Meeting in Las Vegas, Nevada, under the auspices of SMD and ASM-MSD (the ASM/TMS Composites and TMS Powder Materials Committees).     

Influence of V2O5 Addition on Reduction of NO by C3H6 over Pt/V2O5/Al2O3 Monolithic Catalyst

Pt/V2O5/Al2O3 and Pt/Al2O3 monolithic catalysts were prepared by wet impregnation method, and the influence of V2 O5 addition on the catalytic activity for NO reduction by C3 H6 under lean burn condition was investigated in detail.The results show that Pt/V2O5/Al2O3 has better activity of NO reduction than Pt/Al2O3 , adding V2O5 to Pt catalyst makes the temperature window of NO reduction shift further to a lower temperature region.The activity of NO reduction decreases and there is a similar degree of deactivation over the two catalysts in the presence of SO2 in feed gas.Moreover, adding V2 O5 to Pt catalyst resulted in improvement of resistance to SO2 oxidation, which decreases the emission of sulfate particulate.Thermal aging treatment counteractes the promoting effect of V2O5 on NO reduction.     

Phosphate capacity of CaO-AI2O3 slags containing CaF2, BaO,Li2O,or Na2O

Phosphorus partition ratios between CaO-Al₂O₃ and CaO-Al₂O₃-CaF₂ fluxes and Fe-C_sat-P alloys have been measured as a function of slag composition at 1500 °C. The effects of additions of BaO, Li₂O, and Na₂O to the CaO-Al₂O₃-CaF₂ system on the phosphorus partition ratios at 1400 °C and 1300 °C have been measured. From the partition ratio, and assuming that the oxygen potential is controlled by C-CO equilibrium, the phosphate capacities of the fluxes were calculated. Also, the activities of Li₂O and Na₂O were measured as a function of slag composition at 1300 °C by equilibrating the flux and the metal with Pb-Li or Pb-Na alloy and CO in a graphite crucible. The results indicate that phosphorus partition ratios with carbon-saturated iron and the phosphate capacities for additions of more basic oxides decrease in the following order: Na₂Oτ;Li₂Oτ;BaO. The activities of Li₂O and Na₂O in calcium aluminate fluxes have large negative deviations from ideal behavior; the activity coefficients at infinite dilution are on the order of 0.05 and 10^-5, respectively. Formerly Graduate Student, Department of Metallurgical Engineering and Materials Science, Carnegie Mellon University     

Reduction of vesicular acetylcholine transporter mRNA in the rat septum following lead exposure

We have previously observed that maternal exposure to lead (Pb) results in a reduction of levels of mRNA coding for cholineacetyltransferase (ChAT) in the septum of developing rat without affecting the dams. Here we report that Pb similarly affects the expression of vesicular acetylcholine transporter (VAChT) mRNA in the rat septum. In close agreement with the time course of ChAT mRNA expression, septal VAChT mRNA levels increased from 30% at postnatal day 7 to 78% and 100% of adult levels at days 14 and 21, respectively. Maternal exposure to 0.2% lead acetate in drinking water from gestational day 16 resulted in an approximately 30% reduction of VAChT in 7 and 21-day-old rat pups without affecting VAChT mRNA levels in the dams. These results indicate a developmental stage-dependent interference by Pb with ChAT/VAChT gene expression in the rat septum.     

镁砂中Fe2O3、Al2O3、P2O5、TiO2的联合测定

镁砂产品检验中,采用碱熔融法共同预处理样品,在同一母液中,联合测定铁、铝、磷、钛的含量,缩短了检测时间。通过分别控制各元素的显色酸度,各元素线性良好,测得的Fe2O3、Al2O3、P2O5、TiO2的相对标准偏差分别小于1.11%、2.78%、4.84%、5.88%。实验结果表明,方法的准确度和精密度都较高。     

新型SO2和NO吸附-催化剂La-Cu-Na-γ-Al2O3的制备

研究了新型SO2和NO吸附-催化剂La-Cu-Na-γ-Al2O3的制备条件,并用均匀设计法确定了La-Cu-Na-γ-Al2O3的组成.研究表明,当用分步等体积浸渍法制备La-Cu-Na-γ-Al2O3时,以Na2CO3、Cu(NO3)2和La(NO3)3为原料,在873K下空气中焙烧制备的含Na2CO3、CuO、La2O3的质量分数分别为8%、5%、5%的La-Cu-Na-γ-Al2O3,具有较好的低温(423K)同时吸附储存SO2和NO的能力.