Higher-order analysis of four-beam cross grating interferometers

Both on- and off-axis four-beam interference patterns are analyzed using ray tracing. The cross gratinglike interference pattern is accompanied by an extra term which consists of two orthogonal two-beam interference patterns. When partially coherent light is used, the extra term generally degrades the contrast of the cross gratinglike pattern unless some special kinds of source are utilized. With gratings of high spatial frequencies, the amplitude of the extra term can become large compared with the desired term. Consequently, the localized cross gratinglike pattern is changed to be periodic in different directions.

In vivo deposition of ultrafine aerosols in the nasal airway of the rat

We studied the deposition of ultrafine aerosols, ranging in geometric diameter from 0.005 to 0.1 microns, in the nasal airway of Fischer-344/N rats, at inspiratory flow rates of 200, 300, 400, and 600 ml/min. Simultaneously, we measured the pressure drop across the rat nasal airway. The purpose was to determine whether the in vivo deposition of ultrafine aerosols in the rat nasal airway is the same as the deposition observed in rat nasal casts. At a flow rate of 400 ml/min, corresponding to the normal mean inspiratory flow rate of the rat, deposition efficiency increased from 6 to 58%, when the particle diameter decreased from 0.1 to 0.005 microns. For 0.005-microns-diameter particles, the deposition efficiency decreased from 68 to 52% when the flow rate was increased from 200 to 600 ml/min. These results agree well with those from previous experiments with nasal casts, which indicated that diffusion is the dominant mechanism for deposition of ultrafine aerosols. The pressure drop in the nasal airway of the rat increased almost linearly with flow rate, from 73 Pa at 200 ml/min to 247 Pa at 600 ml/min. These values are within the range of those obtained in previous experiments with nasal casts, although the pressure drop in casts increased as a power greater than 1 with flow rate. The results of our study support the use of nasal airway casts to estimate the in vivo deposition of ultrafine aerosols.

Stability and activity of human immunodeficiency virus protease: comparison of the natural dimer with a homologous, single-chain tethered dimer

A single-chain tethered dimer of human immunodeficiency virus protease (HIV-PR) was produced by expression of a synthetic gene in Escherichia coli. The tethered dimer, which consists of two 99-amino acid HIV-PR subunits linked together by a pentapeptide, was isolated from inclusion bodies and refolded as an active protease with enzymatic properties very similar to those of the natural dimer at pH 5.5. In addition to demonstrating that the tethered dimer is active, we have shown that the tethered dimer is more stable than the natural HIV-PR dimer at pH 7.0. This is attributed to dissociation of the natural HIV-PR dimer, for which a surprisingly high dissociation constant, 5 X 10(-8) M was measured. Furthermore, the tethered dimer offers an opportunity to produce asymmetric dimer mutants and thereby determine the effect of changes in one of the two subunits on protease activity. In one such mutant, a single active-site aspartic residue was changed to a glycine residue. This protein was inactive, consistent with a requirement for an aspartic residue from each subunit to constitute an active site of HIV-PR.

Deposition of ultrafine aerosols in rat nasal molds

To evaluate the health effects of air pollutants on the respiratory tract, it is critical to determine the regional deposition of inhaled aerosols. Information on deposition of larger particles (greater than 0.2 microns) in the nasal passages of laboratory animals is available; the deposition fraction increases with increasing particle size. However, little deposition information is available for ultrafine particles of less than 0.2 microns. Three clear, plastic molds (models) of the nasal passages of F344/N rats, prepared from metal replica casts were used in these studies. Total deposition of ultrafine aerosols in the casts was determined by using a unidirectional flow system. The pressure drops measured in the casts were a function of flow rate to the power of 1.4-1.6, indicating that flow through the nasal passages has nonlaminar components. Deposition data were obtained by using monodisperse sodium chloride aerosols with particle sizes ranging from 0.2 to 0.005 microns, at inspiratory and expiratory flow rates of 200 to 600 ml/min. Similar deposition data were obtained for two of the casts studied. Deposition efficiency was greatest for the smallest particles, and decreased with increasing particle size and flow rate. At an inspiratory flow rate of 400 ml/min, which is comparable to the mean respiratory flow of an adult male F344 rat with a respiratory minute volume of 200 ml, deposition efficiencies reached 40 and 70% for 0.01- and 0.005-microns particles, respectively. These studies demonstrated that turbulent diffusional deposition was the dominant mechanism for uptake of ultrafine particles by the nasal passages.

The immunotoxicity of three nickel compounds following 13-week inhalation exposure in the mouse

Groups of B6C3F1 mice were exposed to aerosols of nickel subsulfide (Ni3S2), nickel oxide (NiO), or nickel sulfate hexahydrate (NiSO4.6H2O) 6 hr/day, 5 days per week for 65 days to determine the immunotoxicity of these compounds. Exposure concentrations were 0.11, 0.45, and 1.8 mg Ni/m3 for Ni3S2, 0.47, 2.0, and 7.9 mg Ni/m3 for NiO; and 0.027, 0.11, and 0.45 mg Ni/m3 for NiSO4. Thymic weights were decreased only in mice exposed to 1.8 mg Ni/m3 Ni3S2. Increased numbers of lung-associated lymph nodes (LALN), but not spleen nucleated cells, were seen with all compounds. Nucleated cells in lavage samples were increased in mice exposed to the highest concentrations of NiSO4 and NiO and to 0.45 and 1.8 mg Ni/m3 Ni3S2. Increased antibody-forming cells (AFC) were seen in LALN of mice exposed to 2.0 and 7.9 mg Ni/m3 NiO and 1.8 mg Ni/m3 Ni3S2. Decreased AFC/10(6) spleen cells were observed in mice exposed to NiO, and decreased AFC/spleen were seen for mice exposed to 1.8 mg Ni/m3 Ni3S2. Only mice exposed to 1.8 mg Ni/m3 Ni3S2 had a decrease in mixed lymphocyte response. All concentrations of NiO resulted in decreases in alveolar macrophage phagocytic activity, as did 0.45 and 1.8 mg Ni/m3 Ni3S2. None of the nickel compounds affected the phagocytic activity of peritoneal macrophages. Only 1.8 mg Ni/m3 Ni3S2 caused a decrease in spleen natural killer cell activity. Results indicate that inhalation exposure of mice to nickel can result in varying effects on the immune system, depending on dose and physicochemical form of the nickel compound. These nickel-induced changes may contribute to significant immunodysfunction.

Effect of inhaled azodicarbonamide on F344/N rats and B6C3F1 mice with 2-week and 13-week inhalation exposures

Azodicarbonamide (ADA), a compound used in the baking and plastics industries, has been reported to cause pulmonary sensitization and dermatitis in people. Two-week repeated and 13-week subchronic inhalation exposures of F344/N rats and B6C3F1 mice to ADA were conducted to determine the toxicity of inhaled ADA. The mean air concentrations of ADA in the 2-week studies were 207, 102, 52, 9.4, or 2.0 mg/m3. No exposure-related mortality nor abnormal clinical signs were observed in rats or mice during or after exposure. The terminal body weights were slightly depressed in the highest exposure group. Liver weights were lower in male rats exposed to 200 mg ADA/m3. No significant lesions were noted on either gross or histologic evaluation of rats or mice. In the 13-week subchronic study, the mean air concentrations of ADA were 204, 100, or 50 mg/m3. No mortality or clinical signs related to exposure were observed. The terminal body weights of exposed rats were not significantly different from those of control rats but were significantly depressed in mice exposed to 100 or 200 mg ADA/m3. No histopathological lesions were noted in mice. Lung weights were increased and enlarged mediastinal and/or tracheobronchial lymph nodes were noted in rats exposed to 50 mg ADA/m3. No exposure-related lesions were observed microscopically in rats exposed to 100 or 200 mg ADA/m3. All rats in the 50 mg ADA/m3 exposure group only had lung lesions that consisted of perivascular cuffing with lymphocytes and a multifocal type II cell hyperplasia, suggesting a possible immune reaction to an antigen in the lung. Viral titers for rats exposed to 50 mg ADA/m3 were negative for Sendai virus and pneumonia virus of mice, which produce similar lesions. The possibility of an unknown viral antigen causing this lesion cannot be eliminated. Lung tissue from male rats was analyzed for ADA and biurea, the major metabolite of ADA. No ADA was detected. The amount of biurea in the lungs increased nonlinearly with increasing exposure concentration, suggesting that clearance was somewhat impaired with repeated exposures. However, even at the highest exposure concentration, this amount of biurea was less than 1% of the estimated total ADA deposited over the exposure period. In summary, ADA is rapidly cleared from the lungs, even when inhaled at concentrations up to 200 mg/m3. Exposure to ADA for up to 13 weeks did not appear to be toxic to rodents.

Influence of preexisting pulmonary emphysema on susceptibility of rats to inhaled diesel exhaust

The susceptibilities of normal rats and rats with preexisting pulmonary emphysema to chronically inhaled diesel exhaust were compared. Rats were exposed 7 h/day, 5 days/wk for 24 months to diesel exhaust at 3.5 mg soot/m3, or to clean air as controls. Emphysema was induced in one-half of the rats by intratracheal instillation of elastase 6 wk before exhaust exposure. Measurements included lung burdens of diesel soot, respiratory function, bronchoalveolar lavage, clearance of radiolabeled particles, pulmonary immune responses, lung collagen, excised lung weight and volume, histopathology, and mean linear intercept of terminal air spaces. Parameters indicated by analysis of variance to exhibit significant interactions between the influences of emphysema and exhaust were examined to determine if the effects were more than additive (indicating increased susceptibility). Although 14 of 63 parameters demonstrated emphysema-exhaust interactions, none indicated increased susceptibility. Less soot accumulated in lungs of emphysematous rats than in those of nonemphysematous rats, and the reduced accumulation had a sparing effect in the emphysematous rats. The results did not support the hypothesis that emphysematous lungs are more susceptible than are normal lungs to chronic exposure to high levels of diesel exhaust. The superimposition of effects of emphysema and exhaust, however, might still warrant special concern for heavy exposures of emphysematous subjects.

High-level synthesis of recombinant HIV-1 protease and the recovery of active enzyme from inclusion bodies

A complete chemical synthesis and assembly of genes for the production of human immunodeficiency virus type-I protease (HIV-PR) and its precursors are described. The T7 expression system was used to produce high levels of active HIV-PR and its precursors in Escherichia coli inclusion bodies. The gene encoding the open reading frames of HIV-PR was expressed in E. coli as a 10-kDa protein, while the genes encoding HIV-PR precursors were expressed as larger proteins, which were partially processed in E. coli to the 10-kDa form. These processing events are autoproteolytic, since a single-base mutation, changing the active-site aspartic acid to glycine, completely abolished the conversion. HIV-PR can be released with 8 M urea from washed cellular inclusion bodies, resulting in a preparation with few bacterial host proteins. After refolding, this preparation contains no nonspecific protease or peptidase activities. The recombinant HIV-PR isolated from inclusion bodies cleaves HIV-PR substrates specifically with a specific activity comparable to column-purified HIV-PR.

Heparin modulation of laminin polymerization

Previously, it has been shown that laminin will self-assemble by a two-step calcium-dependent process using end-domain interactions (Yurchenco, P. D., Tsi-library, E. C., Charonis, A. S., and Furthmayr, H. (1985) J. Biol. Chem. 260, 7636-7644). We now find that heparin, at low concentrations, modifies this polymerization by driving the equilibrium further toward aggregation, by producing a denser polymer, and by inducing aggregation in the absence of calcium. This effect on self-assembly is specific in that it is observed with heparin but not with several heparan sulfates or other glycosaminoglycans: it correlates with affinity and depends on the degree of polysaccharide sulfation. Heparin binds to laminin in a calcium-dependent manner with a single class of interaction (KD = 118 +/- 18 nM) and with a binding capacity of one heparin for two laminins. We find the long arm globule (E3) is the only laminin domain which exhibits substantial heparin binding: heparin binds E3 with an affinity (KD = 94 +/- 12 nM) and calcium dependence similar to that for intact laminin. These data strongly suggest that heparin modifies laminin assembly by binding to pairs of long arm globular domains. As a result the polymer may be stabilized at domain E3 and laminin interdomain interactions induced or modified. We further postulate that heparins may act in vivo as specific regulators of the structure and functions of basement membranes by both altering the laminin matrix and by displacing weakly binding heparan sulfates.

White-light joint-transform correlator

The spatial and temporal coherence requirements in the formation of the joint-transform hologram and in the readout process are described, and experimental results are given.

Comparison of detection efficiencies for VanderLugt and joint transform correlators

The correlation of peak intensities of VanderLugt and joint transform correlators with a single object, multiple objects, and noisy environments are analyzed. The study shows that the VanderLugt correlator can generally perform better for the multiple object case and also under a noisy environment.

Glycinamide ribonucleotide synthetase from Escherichia coli: cloning, overproduction, sequencing, isolation, and characterization

The purD gene of Escherichia coli encoding the enzyme glycinamide ribonucleotide (GAR) synthetase, which catalyzes the conversion of phosphoribosylamine (PRA), glycine, and MgATP to glycinamide ribonucleotide, MgADP, and Pi, has been cloned and sequenced. The protein, as deduced by the structural gene sequence, contains 430 amino acids and has a calculated Mr of 45,945. Construction of an overproducing strain behind a lambda pL promoter allowed a 4-fold purification of the protein to homogeneity. N-Terminal sequence analysis and comparison of the sequence with those of other GAR synthetases confirm the amino acid sequence deduced from the gene sequence. Initial velocity studies and product and dead-end inhibition studies are most consistent with a sequential ordered mechanism of substrate binding and product release in which PRA binds first followed by MgATP and then glycine; Pi leaves first, followed by loss of MgADP and finally GAR. Incubation of [18O]glycine, ATP, and PRA results in quantitative transfer of the 18O to Pi. GAR synthetase is very specific for its substrate glycine.

Influence of experimental pulmonary emphysema on the toxicological effects from inhaled nitrogen dioxide and diesel exhaust

This project examined the influence of preexisting, experimentally induced pulmonary emphysema on the adverse health effects in rats of chronic inhalation exposure to either nitrogen dioxide or automotive diesel-engine exhaust. Previous reports indicated that humans with chronic lung disease were among those most severely affected by episodic exposures to high concentrations of airborne toxicants. There were no previous reports comparing the effects of chronic inhalation exposure to components of automotive emissions in emphysematous and normal animals. The hypothesis tested in this project was that rats with preexisting pulmonary emphysema were more susceptible than rats with normal lungs to the adverse effects of the toxicant exposures. Young adult rats were housed continuously in inhalation exposure chambers and exposed seven hours per day, five days per week, for 24 months to nitrogen dioxide at 9.5 parts per million (ppm)2, or to diesel exhaust at 3.5 mg soot/m3, or to clean air as control animals. These concentrations were selected to produce mild, but distinct, effects in rats with normal lungs. Pulmonary emphysema was induced in one-half of the rats by intratracheal instillation of the proteolytic enzyme elastase six weeks before the toxicant exposures began. Health effects were evaluated after 12, 18, and 24 months of exposure. The measurements included respiratory function, clearance of inhaled radiolabeled particles, pulmonary immune responses to instilled antigen, biochemistry and cytology of airway fluid, total lung collagen, histopathology, lung morphometry, and lung burdens of diesel soot. The significance of influences of emphysema and toxicant exposure, and interactions between influences of the two treatments, were evaluated by analysis of variance. The elastase treatment resulted in pulmonary emphysema that was manifested by enlarged alveoli and alveolar ducts, and by ruptured alveolar septa. There was no accompanying inflammation and no alterations of bronchioles. The emphysema persisted throughout the study period, with little evidence of progression. Lung weight was increased, physiological lung volumes were enlarged, lung compliance was increased, and airflow was obstructed. Nitrogen dioxide exposure of normal rats caused mild epithelial hyperplasia and a thickening of the walls of terminal bronchioles, an extension of bronchiolar epithelium into proximal alveoli, and inflammation in proximal alveoli. Lung volume and weight and the lung collagen content were increased. Airway fluid indicators of cell damage and oxidant protective mechanisms were increased. Similar effects of nitrogen dioxide exposure were superimposed over the effects of emphysema in emphysematous nitrogen dioxide-exposed rats. Several parameters were affected similarly by nitrogen dioxide exposure and emphysema (for example, increased lung volume), and the combined effects tended to be additive.(ABSTRACT TRUNCATED AT 400 WORDS)

Azodicarbonamide: methods for the analysis in tissues of rats and inhalation disposition

1. A method has been developed for measuring azodicarbonamide (ADA) and its metabolite biurea in tissues of rat. The method is based on the reaction of ADA with triphenylphosphine; the derivative so formed was isolated and quantified using reversed-phase h.p.l.c. Quantification was by u.v. detection with 14C-ADA as internal standard. Biurea was measured by oxidation to ADA, followed by treatment as described above. 2. When biurea was added to tissues at 100-400 micrograms, recoveries of 92-125% were observed. In contrast, recoveries of ADA added to tissues were generally much less than 100% and could not be reliably determined. The inability to quantify ADA added to tissues was ascribed to its rapid and facile reduction by tissue sulphydryl groups. 3. When rats were exposed to ADA aerosol concentrations of 200, 100, 50 and 0 mg/m3 for 13 weeks by inhalation, a non-linear dose-dependent accumulation of biurea was observed in lungs. No ADA was detected in lungs. Neither biurea nor ADA could be detected in kidneys.

Biochemical responses of rat and mouse lung to inhaled nickel compounds

Nickel subsulfide (Ni3S2), nickel sulfate (NiSO4), and nickel oxide (NiO) are encountered occupationally in the nickel refining and electroplating industries, with inhalation being a common route of exposure. The purposes of this study were to evaluate the biochemical responses of lungs of rats and mice exposed for 13 weeks to occupationally relevant aerosol concentrations of Ni3S2, NiSO4, and NiO, to correlate biochemical responses with histopathologic changes, and to rank the compounds by toxicity. Biochemical responses were measured in bronchoalveolar lavage fluid (BALF) recovered from lungs of exposed animals. Parameters evaluated in BALF were lactate dehydrogenase (LDH), beta-glucuronidase (BG), and total protein (TP). Total and differential cell counts were performed on cells recovered in BALF. All compounds produced an increase in LDH, BG, TP, and total nucleated cells, and an influx of neutrophils, indicating the presence of a cytotoxic and inflammatory response in the lungs of exposed rats and mice. Increases in BG were greater than increases in LDH and TP for both rats and mice. Chronic active inflammation, macrophage hyperplasia, and interstitial phagocytic cell infiltrates were observed histologically in rats and mice exposed to all compounds. Statistically significant increases in BG, TP, neutrophils, and macrophages correlated well with the degree of chronic active inflammation. Results indicated a toxicity ranking of NiSO4 greater than Ni3S2 greater than NiO, based on toxicities of the compounds at equivalent mg Ni/m3 exposure concentrations.

Interactions of alpha- and gamma-interferon in the transcriptional regulation of the gene encoding a guanylate-binding protein

Transcriptional regulation of the gene encoding a guanylate-binding protein (GBP) by the two interferon (IFN) types was studied. GBP gene transcription was regulated by alpha IFN in a manner identical to that of previously described IFN-stimulated genes (ISGs): rapid induction, without a need for protein synthesis, followed by a protein synthesis-dependent suppression of transcription to basal levels within 6 h. Transcriptional induction by gamma IFN was equally rapid and independent of ongoing protein synthesis but remained at elevated levels for greater than 24 h. Experiments employing combined treatments with IFNs of both types revealed that induction of the GBP gene by gamma IFN overrides the alpha IFN-induced active repression and reverses the alpha IFN-induced repressed state. Moreover, the alpha IFN-mediated repression of ISG54, a gene normally responsive to only alpha IFN, is also reversed by gamma IFN. Induction of GBP by gamma IFN is presumably mediated by a factor different from the recently described activator Interferon Stimulated Gene Factor 3 (ISGF3) because induction of this factor was not observed upon treatment of cells with gamma IFN. Finally, a complex set of reinforcing or synergistic effects were observed when induction of the GBP gene was evoked by a combined treatment with the two IFN types.

Effect of four-week repeated inhalation exposure to unconjugated azodicarbonamide on specific and non-specific airway sensitivity of the guinea pig

Reports of respiratory problems among industrial workers exposed repeatedly by inhalation to azodicarbonamide (ADA) raised concern that ADA might be a pulmonary sensitizer. We used a non-invasive method for measuring specific airway conductance to evaluate the potential for repeated inhalation of unconjugated ADA to cause specific or non-specific pulmonary sensitization in the guinea pig. Two groups of male Hartley guinea pigs were exposed 6 h/day, 5 days/week for 4 weeks to aerosolized ADA at 51 or 200 mg/m3, or to filtered air as controls. One group was tested for specific sensitization to ADA by measuring specific airway conductance during inhalation challenge with ADA before and on the third day after the 4-week ADA exposure. The ADA concentrations for the challenges were identical to the repeated exposure concentrations (51 or 200 mg/m3, 200 mg/m3 for controls). The other group was tested for non-specific airway sensitization by inhalation challenge with aerosolized histamine before and after the 4-week ADA exposure. Histamine was administered in stepwise increasing concentrations to elicit an airway response in each guinea pig. Skin tests for immunological responses to ADA, body weight and histopathology of the respiratory tract and skin test sites were also evaluated. The 4-week exposure to ADA did not result in either specific or non-specific airway sensitization. The ADA exposure did not induce positive skin reactions, influence body weight or cause histopathological responses. These results indicate that ADA, acting alone (i.e. not conjugated to a protein), is not a pulmonary sensitizer in the guinea pig exposed repeatedly for 4 weeks and challenged to simulate a 'Monday morning' exposure.

Lung toxicity after 13-week inhalation exposure to nickel oxide, nickel subsulfide, or nickel sulfate hexahydrate in F344/N rats and B6C3F1 mice

The relative toxicity of nickel oxide (NiO), nickel sulfate hexahydrate (NiSO4.6H2O), and nickel subsulfide (Ni3S2) was studied in F344/N rats and B6C3F1 mice after inhalation exposure for 6 hr/day, 5 days/week, for 13 weeks. Exposure concentrations used (as mg Ni/m3) were 0.4-7.9 for NiO, 0.02-0.4 for NiSO4.6H2O, and 0.11-1.8 for Ni3S2. No exposure-related effects on mortality and only minor effects on body weight gain were seen in rats or mice. The most sensitive parameter for nickel toxicity was histopathologic change in the lungs of exposed animals were chronic active inflammation, fibrosis, and alveolar macrophage hyperplasia were associated with nickel exposure. There was an exposure-related increase in lung weight in rats and mice. Equilibrium levels of nickel in the lung were reached by 13 weeks of nickel sulfate and nickel subsulfide exposure, whereas lung levels of nickel continued to increase throughout exposure to nickel oxide. Additional exposure-related histopathologic lesions in treated animals included atrophy of the olfactory epithelium after nickel sulfate and nickel subsulfide exposure. No nasal lesions were seen after nickel oxide exposure. Lymphoid hyperplasia of the bronchial lymph nodes developed in animals exposed to all three nickel compounds. The order of toxicity corresponded to the water solubility of the nickel compounds, with nickel sulfate being most toxic, followed by nickel subsulfide and nickel oxide.

Experimental use of a low cost liquid crystal TV in multiplex holography

We demonstrate experimentally the use of liquid crystal television to make a multiplex hologram.

Interference patterns in cross-grating interferometers: further analysis

The fringe characteristics in four-beam cross-grating interferometers, illuminated by a source at finite distance, are analyzed. From the measurements of the fringe visibilities and the fringe shifts on discrete planes, the spatial irradiance distribution of the illuminating source which is separable in two orthogonal directions can be synthesized. When the line structures of the two cross gratings are not parallel, the fringe pattern has lower contrast which suggests that four line gratings should be used to replace the second cross grating in order to have high contrast fringes. The possibility of forming cross-gratinglike patterns using either a combination of one cross grating and two line gratings or a combination of two line-grating interferometers is discussed. Finally, moire interferometry using a cross-grating interferometer is suggested.

Analysis of the interference pattern in a cross-grating interferometer

A structured source is used to illuminate the four-beam cross-grating interferometer to cause the interference fringes to localize at different planes. When a monochromatic spatially incoherent source is used, the amplitude transmittance of the first cross grating can be imaged to different locations in various planes. With white light extended source illumination, a cross-gratinglike pattern can be formed not only near but also far away from the optical axis simply by choosing four beams of equal path length to interfere. A multicross-grating interferometer is also analyzed with special emphasis on the three-cross-grating interferometer.

Comparative toxicity of nickel oxide, nickel sulfate hexahydrate, and nickel subsulfide after 12 days of inhalation exposure to F344/N rats and B6C3F1 mice

The relative toxicity of nickel oxide (NiO), nickel sulfate hexahydrate. (NiSO4.6H2O), and nickel subsulfide (Ni3S2) was studied in F344/N rats and B6C3F1 mice after inhalation exposure for 6 h/day, 5 days/week for 12 exposure days. Exposure concentrations used (as mg Ni/m3) were 0.9-23.6 for NiO; 0.8-13.3 for NiSO4.6H2O, and 0.4-7.3 for Ni3S2. For each compound there were 5 exposure groups plus a control group. NiSO4.6H2O was the most toxic compound with exposure related mortality seen at exposure concentrations of 13.3 mg/m3 in rats and 1.6 mg/m3 and above in mice. For Ni3S2, mortality was seen in mice (but not in rats) at the highest exposure concentration (7.3 mg/m3). No mortality was seen after NiO exposure. Lesions of the lung and nasal cavity were seen in both rats and mice after exposure to NiSO4.6H2O and Ni3S2 at the 4 highest exposure concentrations. Lesions of the lung were seen primarily at the highest exposure concentrations after NiO exposure. The amount of nickel in the lungs at the end of exposure varied in relation to the water solubility of the compounds. Based on these 2-week studies, the toxicity ranking was NiSO4.6H2O greater than Ni3S2 much greater than NiO. Additional studies are in progress to assess the relative toxicities of these three nickel compounds after 90-day exposures.

Accumulation of guanylate binding proteins in patients treated with interferons

We have previously described an interferon (IFN)-induced protein with a molecular weight of 67,000. This protein has an affinity to guanylates and is thus called guanylate binding protein (GBP). The synthesis of GBP is inducible by IFNs in all human diploid fibroblast cell lines that we studied. To determine whether or not the GBP synthesis is IFN-inducible in humans as well as in cultured cells, we have studied the levels of GBP in the peripheral blood leukocytes (PBL) of patients treated with either type I or type II IFN. An increased GBP level was found the day immediately after treatment with either type of IFN, and the elevated GBP levels were maintained for at least 8 days. Among the patients studied, we found a higher level GBP accumulation (2.3x) in patients treated with IFN-beta than in those treated with IFN-gamma (1.6x). The increase of GBP in patients receiving IFN-gamma correlated with increases in class II histocompatibility antigens, HLA-DR and HLA-DQ in monocytes. Thus, the levels of GBP in peripheral blood leukocytes may be used as a parameter for the study of IFN responses in patients.

Characterization and chemical properties of phosphoribosylamine, an unstable intermediate in the de novo purine biosynthetic pathway

Incubation of [1-13C]-5-phosphoribosyl pyrophosphate ([1-13C]PRPP) and glutamine with PRPP amidotransferase results in rapid production and disappearance of two new resonances at 89.3 and 85.9 ppm. These resonances coincide with two of the products produced upon incubation of [1-13C]ribose 5-phosphate with NH3. Extensive NMR studies (15N and 1H-13C chemical shift correlation spectra) have allowed assignment of these resonances to beta- and alpha-phosphoribosylamine. These studies represent the first spectral observations of this chemically reactive intermediate. The rate of interconversion of alpha- to beta-phosphoribosylamine as a function of pH has been determined by saturation and inversion-transfer NMR methods. The rate of formation of 5-phosphoribosylamine (PRA) from ribose 5-phosphate and NH3 and its rate of decomposition as a function of pH have been determined with a glycinamide ribonucleotide synthetase trapping system fashioned after earlier studies of Nierlich and Magasanik [Nierlich, D. P., & Magasanik, B. (1965) J. Biol. Chem. 240, 366]. Phosphoribosylamine has a t1/2 = 38 s at 37 degrees C and pH 7.5. The pH-independent equilibrium constant for ribose 5-phosphate and NH3 with phosphoribosylamine has been established, 2.5 M-1, by use of these rate constants as well as by NMR methods. This equilibrium constant and the rates of nonenzymatic interconversion of alpha- and beta-PRA provide essential background for studying the mechanism of glycinamide ribonucleotide synthetase and investigating the possibility of channeling phosphoribosylamine between this enzyme and the first enzyme in the purine pathway.