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Context: There are at least 24 missense, nonconservative mutations found in the ACTH receptor [melanocortin 2 receptor (MC2R)] that have been associated with the autosomal recessive disease familial glucocorticoid deficiency (FGD) type 1. The characterization of these mutations has been hindered by difficulties in establishing a functional heterologous cell transfection system for MC2R. Recently, the melanocortin 2 receptor accessory protein (MRAP) was identified as essential for the trafficking of MC2R to the cell surface; therefore, a functional characterization of MC2R mutations is now possible., Objective: Our objective was to elucidate the molecular mechanisms responsible for defective MC2R function in FGD., Methods: Stable cell lines expressing human MRAPalpha were established and transiently transfected with wild-type or mutant MC2R. Functional characterization of mutant MC2R was performed using a cell surface expression assay, a cAMP reporter assay, confocal microscopy, and coimmunoprecipitation of MRAPalpha., Results: Two thirds of all MC2R mutations had a significant reduction in cell surface trafficking, even though MRAPalpha interacted with all mutants. Analysis of those mutant receptors that reached the cell surface indicated that four of six failed to signal, after stimulation with ACTH., Conclusion: The majority of MC2R mutations found in FGD fail to function because they fail to traffic to the cell surface.

Using both in vivo (inhalation) and in vitro (cell culture) studies, we previously reported that p-aramid respirable fibers (RFP--defined as respirable-sized fiber-shaped particulates) are biodegraded in lungs and lung cells of rats following exposures. The current studies were undertaken to determine whether shortening mechanisms of p-aramid RFP biodegradability are also operative in human lung cells. Cultures of human A549 lung epithelial cells (A549), primary alveolar macrophages (HBAL) (collected via bronchoalveolar lavage [BAL]) from volunteers), and co-cultures (Co) of the A549 and HBAL were incubated with p-aramid RFP for either 1 h, 1 day, or 1 week to assess RFP shortening. Lengths of RFP were measured using scanning electron microscopy (SEM) following fixation, digestion of culture tissue components, and processing. Similar to findings using rat lung cells, only slight RFP shortening was measured in A549 cultures at 1-day and 1-week post-incubation. More importantly, in HBAL and Co groups, greater transverse cleavage of p-aramid RFP was measured at 1-day and 1-week postexposure compared to 1-h HBAL or Co groups, or in any A549 groups. In contrast, cellulose RFP, a biopersistent reference control fiber, were not measurably shortened under similar circumstances. Second, p-aramid RFP were incubated either with phosphate-buffered saline (PBS), or acellular BAL fluids from human volunteers or rats and processed for SEM analysis of RFP lengths. Mean lengths of p-aramid RFP incubated with human or rat BAL fluids were substantially decreased compared to PBS. Similar to our findings with rat lung cells, components of human lung fluids coat the p-aramid RFP as a prerequisite for subsequent enzymatic cleavage by human phagocytic lung cells and this finding reinforces the concept that inhaled p-aramid RFP are likely to be biodegradable in the lungs of humans.

Most pigment-grade titanium dioxide (TiO(2)) samples that have been tested in pulmonary toxicity tests have been of a generic variety-i.e., generally either uncoated particles or TiO(2) particles containing slightly hydrophilic surface treatments/coatings (i.e., base TiO(2)). The objectives of these studies were to assess in rats, the pulmonary toxicity of inhaled or intratracheally instilled TiO(2) particle formulations with various surface treatments, ranging from 0-6% alumina (Al(2)O(3)) or alumina and 0-11% amorphous silica (SiO(2)). The pulmonary effects induced by TiO(2) particles with different surface treatments were compared to reference base TiO(2) particles and controls. In the first study, groups of rats were exposed to high exposure (dose) concentrations of TiO(2) particle formulations for 4 weeks at aerosol concentrations ranging from 1130-1300 mg/m(3) and lung tissues were evaluated by histopathology immediately after exposure, as well as at 2 weeks and 3, 6, and 12 months postexposure. In the second study, groups of rats were intratracheally instilled with nearly identical TiO(2) particle formulations (when compared to the inhalation study) at doses of 2 and 10 mg/kg. Subsequently, the lungs of saline-instilled and TiO(2)-exposed rats were assessed using both bronchoalveolar (BAL) biomarkers and by histopathology/cell proliferation assessment of lung tissues at 24 h, 1 week, 1 and 3 months postexposure. The results from these studies demonstrated that for both inhalation and instillation, only the TiO(2) particle formulations with the largest components of both alumina and amorphous silica surface treatments produced mildly adverse pulmonary effects when compared to the base reference control particles. In summary, two major conclusions can be drawn from these studies: (1) surface treatments can influence the toxicity of TiO(2) particles in the lung; and (2) the intratracheal instillation-derived, pulmonary bioassay studies represent an effective preliminary screening tool for inhalation studies with the identical particle-types used in this study.

The aim of this study was to evaluate the acute lung toxicity of intratracheally instilled single-wall carbon nanotubes (SWCNT) in rats. The lungs of rats were instilled either with 1 or 5 mg/kg of the following control or particle types: (1) SWCNT, (2) quartz particles (positive control), (3) carbonyl iron particles (negative control), (4) phosphate-buffered saline (PBS) + 1% Tween 80, or (5) graphite particles (lung tissue studies only). Following exposures, the lungs of PBS and particle-exposed rats were assessed using bronchoalveolar lavage (BAL) fluid biomarkers and cell proliferation methods, and by histopathological evaluation of lung tissue at 24 h, 1 week, 1 month, and 3 months postinstillation. Exposures to high-dose (5 mg/kg) SWCNT produced mortality in ~15% of the SWCNT-instilled rats within 24 h postinstillation. This mortality resulted from mechanical blockage of the upper airways by the instillate and was not due to inherent pulmonary toxicity of the instilled SWCNT particulate. Exposures to quartz particles produced significant increases versus controls in pulmonary inflammation, cytotoxicity, and lung cell parenchymal cell proliferation indices. Exposures to SWCNT produced transient inflammatory and cell injury effects. Results from the lung histopathology component of the study indicated that pulmonary exposures to quartz particles (5 mg/kg) produced dose-dependent inflammatory responses, concomitant with foamy alveolar macrophage accumulation and lung tissue thickening at the sites of normal particle deposition. Pulmonary exposures to carbonyl iron or graphite particles produced no significant adverse effects. Pulmonary exposures to SWCNT in rats produced a non-dose-dependent series of multifocal granulomas, which were evidence of a foreign tissue body reaction and were nonuniform in distribution and not progressive beyond 1 month postexposure (pe). The observation of SWCNT-induced multifocal granulomas is inconsistent with the following: (1) lack of lung toxicity by assessing lavage parameters, (2) lack of lung toxicity by measuring cell proliferation parameters, (3) an apparent lack of a dose response relationship, (4) nonuniform distribution of lesions, (5) the paradigm of dust-related lung toxicity effects, (6) possible regression of effects over time. In addition, the results of two recent exposure assessment studies indicate very low aerosol SWCNT exposures at the workplace. Thus, the physiological relevance of these findings should ultimately be determined by conducting an inhalation toxicity study.

The 31mer 5'-TCA ACG CTA GAA TTC GGA TCC ATC GCT TGG T, the complementary 33mer 5'-CCA AGC GAT GGA TCC GAA TTC TAG CGT TGA GAT, the 40mer 5'-GGC CAG GAT GGT GAA GAA TTC GAT CCG GTA CGT AGC TAA G, and the complementary 42mer 5'-TAC TTA GCT ACG TAC CGG ATC GAA TTC TTC ACC ATC CTG GCC were synthesized and their reactivity towards EcoRI was studied. It was found that the 31mer and the 40mer were cleaved at a comparable rate to the 31mer-33mer hybrid and the 40mer-42mer hybrid, respectively. The rate of cleavage of the 33mer and the 42mer was an order of magnitude lower. To rule out possible intermolecular duplex formation, the 33mer was immobilized on cellulose by ligation and labeled with alpha 32P-dCTP using Klenow fragment of E. coli DNA polymerase. EcoRI cleaved this immobilized oligomer into specific fragments.

This paper reports details of the synthesis of oligodeoxynucleotides containing the modified base 5-methyl-N4,N4-ethanocytosine (Ce). The 9-fluorenylmethoxycarbonyl group is used as a protecting group for the exocyclic amines of dA and dC. This group can be removed rapidly under very mild conditions. Oligomers containing the Ce base form a cross-link when hybridized to their complementary deoxyoligonucleotides. Some of the scope and limitations of these cross-link forming oligonucleotides are reported.

In order to gain more understanding about the mode of action of DNA polymerase, eight related partially self-complementary "hairpin" shaped oligodeoxynucleotides were prepared. Four of the oligomers contained either 1-beta-D-arabinofuranosyluracil (ara-U) or 1-beta-D-2'deoxyxylofuranosylthymine (dxT) nucleoside analogs at their 3' termini. We investigated the ability of the oligomers to prime DNA synthesis in relationship to the stability of the hybridized region, the nature of the sugar terminus and the DNA polymerase used (reverse transcriptase, or polymerase alpha). The results are discussed in relation to the mode of action of some nucleoside analog inhibitors of DNA polymerase. An understanding of the mechanism of DNA polymerase action was used to design template-primer analogs as polymerase inhibitors. Two of the oligodeoxynucleotide analogs prepared were found to be potent inhibitors of polymerase alpha.

The template-directed oligomerization of activated derivatives of 2-aminoadenylic acid (paA) on polyuridylic acid (poly(U)) in aqueous buffers was studied. The reaction differs from that of adenylic acid (pA) under identical conditions, in that only di- and tri-nucleotides are observed as substantial products rather than a longer sequence of oligomers. The reaction of paA also differs from that of pA in that it does not require Mg++, and is less susceptible to increased temperature. The relevance of these observations to the chemical evolution of polynucleotide replication is discussed. Improved syntheses of paA and its diphosphate are reported.