Up-regulation of granulocyte-macrophage colony-stimulating factor (GM-CSF) receptors in murine peritoneal exudate macrophages by both GM-CSF and IL-3.

Murine peritoneal exudate macrophages (PEM) display multiple CSF receptors. In this study, the expression of granulocyte-macrophage (GM)-CSF receptors in PEM was studied. PEM displayed over 5000 single type, high affinity GM-CSF receptors/cell with a Kd = 38 to 42 pM and an apparent molecular mass of 86,000 Da. Treatment of PEM with low, but not high, concentrations of recombinant murine (rMu) GM-CSF continuously for 24 h resulted in a marked up-regulation of GM-CSF receptors in PEM. A similar up-regulation of GM-CSF receptors also was detected in PEM cultures treated with rMuIL-3 (1-100 ng/ml) for 24 h or longer, regardless the doses of rMuIL-3 added in this case. Scatchard analysis of equilibrium binding showed that the enhanced binding activities in both cases were due to an increase in total number of GM-CSF receptors rather than changes in receptor affinity. Contrariwise, treatment with recombinant human macrophage-CSF (greater than 100-1000 ng/ml) partially inhibited the expression of GM-CSF receptors in PEM. Removal of rMuGM-CSF from culture medium 24 h after treatment led to a further up-regulation of GM-CSF receptors over a 4 to 24-h period, depending on the doses of initial treatment. On the other hand, removal of rMuIL-3 from culture medium after prolonged treatment did not result in further increase in GM-CSF receptors. The protein synthesis inhibitor cycloheximide abrogated GM-CSF receptor up-regulation induced by both rMuIL-3 and rMuGM-CSF, whereas actinomycin D inhibited only the second (8-24 h) phase of GM-CSF receptor up-regulation induced by exposure to high concentrations rMuGM-CSF (10 ng/ml). These findings suggest that rMuGM-CSF and rMuIL-3 up-regulate GM-CSF receptors in PEM in part through similar or identical metabolic pathways and provide further evidence of a close linkage between IL-3 and GM-CSF receptors.     

Regions of the CD4 molecule not involved in virus binding or syncytia formation are required for HIV-1 infection of lymphocytes.

Cell surface-expressed CD4 binds to the envelope glycoprotein of HIV-1 and mediates syncytia formation through interacting with membrane expressed HIV-1 gp120. Further possible roles of the CD4 molecule in the process of cell infection by HIV-1 remain poorly understood. In our study we describe two mAb that recognize the V3/V4 domain of the CD4 molecule. Although these mAb do not inhibit gp120-CD4 binding or HIV-1-induced syncytia formation, they inhibit HIV-1 infection of human PBL. These findings suggest that discrete, definable domains of the CD4 molecule may be involved in interactions after HIV-1 envelope binding that lead to virus entry into the cell.     

Serum protease inhibitors promote anchorage-independent growth of transformed cells in serum-free medium.

The effect of three serum serine protease inhibitors on the serum-free agar growth of an SV40-transformed 3T3 cell line was investigated. Antithrombin III, alpha-2-macroglobulin and alpha-1-antitrypsin were found to potently stimulate colony growth in a semisolid medium because of their anti-proteolytic properties. These results indicate that protease inhibitors can facilitate tumor cell growth in serum-free agar cultures and suggest that the stimulatory effect of serum on the growth of certain transformed cells in agar may at least partially be due to the high levels of protease inhibitors found in serum.     

Genotoxicity of heated cooking oil vapors.

Epidemiological studies of lung cancer in Chinese women indicated that factors other than cigarette smoking are related to lung cancer risk. A case-control study suggested that indoor air pollution, particularly from cooking oil emissions, may be involved. Condensates of volatile emissions from rapeseed and soybean cooking oils were prepared and found to be genotoxic in short-term tests including the Salmonella mutation assay, SV50 forward-mutation assay, and sister-chromatid exchange assay, as well as the micronucleus assay in mouse bone marrow. In contrast, condensates from rapeseed oil with butylated hydroxyanisole or hydrogenated rapeseed oil were not mutagenic, implicating oxidation products as the cause for mutagenicity. Peanut oil and lard condensates were not mutagenic in any assay. The association of exposure to Chinese rapeseed cooking-oil emissions and lung-cancer risk may be related to the mutagenic component of these condensates.     

Abscisic Acid increases terrestrial plant cell resistance to hydrostatic pressure

Cells of the terrestrial plant species bromegrass (Bromus inermis L.) are not naturally adapted to withstand the hydrostatic pressures encountered in aquatic environments. However, after treatment with the natural plant growth hormone abscisic acid (75 micromolar), bromegrass cells survived a hydrostatic pressure of 101.3 megapascals, approximating the limits of ocean depth (10,860 m). The increased resistance to hydrostatic pressure from 1 to 7 days of abscisic acid treatment paralleled the induced elevation of cell tolerance to freezing stress.     

Coupling of Carbon Dioxide Fixation to the Oxyhydrogen Reaction in the Isolated Chloroplast of Chlamydomonas reinhardtii

The oxyhydrogen reaction (the reduction of O₂ to water by H₂) in the presence of CO₂ was studied in the isolated Chlamydomonas reinhardtii chloroplast by monitoring the rate of ¹⁴CO₂ incorporation into acid-stable products in the dark. The endogenous rate of CO₂ uptake (50-125 nmol/mg chlorophyll per h) was increased about 3- to 4-fold by ATP and additionally when combined with glucose, ribose-5-phosphate, and glycerate-3-phosphate. The rate was diminished 50 to 75%, respectively, when H₂ was replaced by N₂ or by air. Decrease in CO₂ uptake by dl-glyceraldehyde was taken to indicate that the regenerative phase and complete Calvin cycle turnover were involved. Diminution of CO₂ incorporation by rotenone, antimycin A, and 2,5-dibromo-3-methyl-6-isopropanol-p-benzoquinone was attributed to an inhibition of the oxyhydrogen reaction, resulting in an elevated NADPH/NADP ratio. If so, then the diminished CO₂ uptake could have been by “product inhibition” of the carbon metabolic network. Our data are consistent with the proposal (H. Gaffron [1942] J Gen Physiol 26: 241-267) that CO₂ fixation coupled to the oxyhydrogen reaction is dependent to some extent on exchloroplastic metabolism. This support is primarily ATP provided by mitochondrial respiration.     

Short-term effects of rhizosphere microorganisms on fe uptake from microbial siderophores by maize and oat

Effects of rhizosphere microorganisms on Fe uptake by oat (Avena sativa) and maize (Zea mays) were studied in short-term (10 h) nutrient solution experiments. Fe was supplied either as microbial siderophores (pseudobactin [PSB] or ferrioxamine B [FOB]) or as phytosiderophores obtained as root exudates from barley (epi-3-hydroxy-mugineic acid [HMA]) under varied population densities of rhizosphere microorganisms (axenic, uninoculated, or inoculated with different microorganism cultures). When maize was grown under axenic conditions and supplied with FeHMA, Fe uptake rates were 100 to 300 times higher compared to those in plants supplied with Fe siderophores. Fe from both sources was taken up without the involvement of an extracellular reduction process. The supply of FeHMA enhanced both uptake rate and translocation rate to the shoot (more than 60% of the total uptake). However, increased density of microorganisms resulted in a decrease in Fe uptake rate (up to 65%), presumably due to microbial degradation of the FeHMA. In contrast, when FeFOB or FePSB was used as the Fe source, increased population density of microorganisms enhanced Fe uptake. The enhancement of Fe uptake resulted from the uptake of FeFOB and FePSB by microorganisms adhering to the rhizoplane or living in the free space of cortical cells. The microbial apoplastic Fe pool was not available for root to shoot transport or, thus, for utilization by the plants. These results, in addition to the low uptake rate under axenic conditions, are in contrast to earlier hypotheses suggesting the existence of a specific uptake system for Fe siderophores in higher plants. The bacterial siderophores PSB and FOB were inefficient as Fe sources for plants even when supplied by stem injection. It was concluded that microorganisms are involved in degradation processes of microbial siderophores, as well as in competition for Fe with higher plants.     

The effect of light fluence rate in photodynamic therapy of normal rat brain.

This paper reports the effect of incident light fluence rate on the depth to which necrotic lesions are produced by photodynamic therapy (PDT) in the brains of normal Fisher rats. The rats were injected intraperitoneally with Photofrin (12.5 mg kg-1) 48 h prior to PDT with a fixed incident fluence of 35 J cm-2. The treatment was performed at 10, 50, 100, and 200 mW cm-2 and also in a periodic manner (30 s "on" at 100 mW cm-2, 30 s "off"). The depth to which necrosis occurred was determined 24 h after treatment by microscopic examination of tissue sections. No differences were found in the depth to which necrosis was produced by any of the five irradiation schedules. This finding is discussed in the context of other published dose-rate experiments.     

Production and cytogenetic analysis of BC1, BC2, and BC3 progenies of an intergeneric hybrid between Triticum aestivum (L.) Thell. and tetraploid Agropyron cristatum (L.) Gaertn.

Summary Intergeneric hybrids between Triticum aestivum cv Chinese Spring and Agropyron cristatum 4x (2n= 5x=35, ABDPP genomes) with a high level of homoeologous meiotic pairing between the wheat chromosomes were backcrossed 3 times to wheat. Pollination of the F₁ hybrid with Chinese Spring resulted in 22 BC₁ seeds with an average seed set of 1.52%. Five BC₁ plants with 39–41 chromosomes were raised using embryo rescue techniques. Chromosome pairing in the BC₁ was characterized by a high frequency of multivalent associations, but in spite of this there was no evidence of homoeologous pairing between chromosomes of wheat and those of Agropyron. All of the plants were self sterile. The embryo rescue technique was again essential to produce 39 BC₂ plants with chromosome numbers ranging from 37 to 67. The phenomenon of meiotic non-reduction was also observed in the BC₃ progenies. In this generation male and female fertility greatly increased, and meiotic pairing was fairly regular. Some monosomic (2n=43) and double monosomic (2n=44) lines were produced. Analysis of these progenies should permit the extraction of the seven possible wheat-Agropyron disomic addition lines including those with the added chromosomes carrying the genes involved in meiotic non-reduction and in suppression of Ph activity.