Paclitaxel enhances macrophage IL-12 production in tumor-bearing hosts through nitric oxide.

Tumor-induced macrophages (Mphis) mediate immunosuppression, in part, through increased production of factors that suppress T cell responsiveness and underproduction of positive regulatory cytokines. Pretreatment of tumor-bearing host (TBH) Mphis with the anticancer agent paclitaxel (Taxol) partially reverses tumor-induced Mphi suppressor activity, suggesting that paclitaxel may restore TBH Mphi production of proimmune factors. Because paclitaxel demonstrates LPS-mimetic capabilities and increased production of the LPS-induced immunostimulatory cytokine IL-12 could account for enhanced T cell responsiveness, we investigated whether paclitaxel induces Mphi IL-12 production. Tumor growth significantly down-regulated Mphi IL-12 p70 production through selective dysregulation of IL-12 p40 expression. LPS stimulation failed to overcome tumor-induced dysregulation of p40 expression. In contrast, paclitaxel significantly enhanced both normal host and TBH Mphi IL-12 p70 production in vitro, although TBH Mphi IL-12 production was lower than that of similarly treated normal host Mphis. Paclitaxel enhanced p40 expression in a dose-dependent manner. Through reconstituted Mphi IL-12 expression, paclitaxel pretreatment relieved tumor-induced Mphi suppression of T cell alloreactivity. Blocking Mphi NO suppressed paclitaxel's ability to induce IL-12 production. This suggests that paclitaxel-induced activities may involve a NO-mediated autocrine induction pathway. Collectively, these data demonstrate that paclitaxel restores IL-12 production in the TBH and ascribe a novel immunotherapeutic component to the pleiotropic activities of NO. Through its capacity to induce IL-12 production, paclitaxel may contribute to the correction of tumor-induced immune dysfunction.     

Effect of light and oxygen on neocarzinostatin stability and DNA-cleaving activity.

The in vitro DNA-cleaving activity of neocarzinostatin, a protein antibiotic, is strongly but reversibly inhibited by anaerobiosis. Half-maximal activity is seen in the presence of 0.25 mM O2. The stability of neocarzinostatin, as demonstrated by its ability to cleave DNA, is significantly reduced in light. Inactivation by light is complete and irreversible.     

Linkage and the Maintenance of Heritable Variation by Mutation-Selection Balance

The role of linkage in influencing heritable variation maintained through a balance between mutation and stabilizing selection is investigated for two different models. In both cases one trait is considered and the interactions within and between loci are assumed to be additive. Contrary to most earlier investigations of this problem no a priori assumptions on the distribution of genotypic values are imposed. For a deterministic two-locus two-allele model with recombination and mutation, related to the symmetric viability model, a complete nonlinear analysis is performed. It is shown that, depending on the recombination rate, multiple stable equilibria may coexist. The equilibrium genetic and genic variances are calculated. For a polygenic trait in a finite population with a possible continuum of allelic effects a simulation study is performed. In both models the equilibrium genetic and genic variances are roughly equal to the house-of-cards prediction or its finite population counterpart as long as the recombination rate is not extremely low. However, negative linkage disequilibrium builds up. If the loci are very closely linked the equilibrium additive genetic variance is slightly lower than the house-of-cards prediction, but the genic variance is much higher. Depending on whether the parameters are in favor of the house-of-cards or the Gaussian approximation, different behavior of the genetic system occurs with respect to linkage.     

Computer-assisted imaging cytometry of nuclear chromatin reveals bone tumor virus infection and neoplastic transformation of adherent osteoblast-like cells

Established osteoblast-like (OB) cells infected with the bone tumor-inducing C-type retrovirus OA MuLV remained nontumorigenic over 104 cell culture passages. DNA histograms revealed a new cell population with a stem line peak at 5c. A second OA MuLV-infected OB cell line underwent neoplastic transformation with increasing passage level. These cells showed diffuse aneuploidy. Stepwise linear discriminant analysis of the chromatin structure of control, OA MuLV-infected, and FBR osteosarcoma virus-transformed cell lines resulted in various levels of discrimination ranging between 79.6% for control cells versus nontumorigenic OA MuLV-infected cells, and 96.6% for nontumorigenic OA MuLV-infected cells versus FBR osteosarcoma virus-transformed cells. OA MuLV-infected tumorigenic cells and FBR osteosarcoma virus-transformed cells were discriminated at a 93.6% level.     

Influenza virus-model membrane interaction. A morphological approach using modern cryotechniques

The membrane fusion activity of influenza virus was characterized morphologically using a model system composed of a highly purified influenza B virus suspension and ganglioside-containing zwitterionic liposomes. Electron microscopical analysis was performed after a combination of fast-freezing with either freeze-fracture or freeze-substitution-thin sectioning, ensuring maximal time resolution and avoiding preparation artifacts. In a parallel fluorescence 'lipid mixing' fusion assay, influenza virus-membrane fusion was characterized biochemically. Biochemical and morphological data are in full agreement, indicating negligible membrane fusion activity at neutral pH and high fusion activity at low pH. The freeze-fracture morphology strongly suggests a local point contact between viral and liposomal membrane at neutral pH, and a local point fusion mechanism for influenza virus-membrane fusion upon lowering of the pH. Fusion is followed by lipid mixing, lateral diffusion of viral spike proteins and exposure of viral contents at the inner liposomal surface.     

Phosphorus deficiency induced by nitrogen input in Douglas fir in the Netherlands

Summary A re-examination of earlier NPK fertilization experiments in Douglas fir stands on sandy soils shows the effects of high nitrogen input by air pollution during the last 10–15 years on plant nutrition at these sites. In 1960, experimental plots showed a positive growth reaction to nitrogen, phosphorus, and potassium fertilization. All suffered from severe phosphorus deficiency in 1984, low phosphorus in the needles was invariably accompanied by a high nitrogen content, with all N/P ratios between 20 and 30. The same conclusion emerges from an independent investigation of nutrient status of a selection of Douglas fir stands. Hence, if stand productivity and a balanced nutrient status of the trees is to be maintained, the increase in atmospheric input of nitrogen calls for supplementary fertilization. Given the current N/P ratios in the needles, a positive growth response to phosphorus fertilization is to be expected.     

Fibronectin and laminin in the extracellular matrix and basement membrane of sea urchin embryos

Fibronectin and laminin have been found in the extracellular matrix and in the basement membrane of sea urchin embryos during early development. These glycoproteins are also found on the cell surfaces of the outer epithelial layer and on the secondary mesenchyme cells within the blastocoel. The similarity of functions of the extracellular matrix and basement membrane is discussed, as is the similarity of their molecular components. These observations suggest the possibility that fibronectin and laminin form a continuous matrix surrounding the cells which links the outer ECM (hyaline layer) to the inner ECM (basement membrane). Such a network could coordinate the various activities of the embryo during early morphogenesis.