The effect of triacontanol on growth, photosynthesis and photorespiration in Chlamydomonas reinhardtii and Anacystis nidulans

Chlamydomonas reinhardtii Dangerad 11–32(90) (−), which exhibits C3 properties, and Anacystis nidulans (Strain no. UTEX 625), which exhibits C4 properties, were used to study the effects of triacontanol on growth, photosynthesis and photorespiration. Photosynthetic rate was measured as CO2 uptake and the O2 inhibition of photosynthesis was used as a measure of photorespiration. Triacontanol dissolved in chloroform and dispersed in Tween-20 and triacontanol colloidally dispersed in an aqueous solution of sodium tallow alkyl sulfate were tested. Chlamydomonas cultures increased significantly in cell number after 4 days, and in chlorophyll content after 3 days of treatment with 2.3 × 10⁻⁸ M TRIA in chloroform/Tween-20. In cultures of Anacystis the chlorophyll content became significantly higher 3 days after treatment with 2.3 × 10⁻⁹ M TRIA and the cell number was noticeably higher than the controls.
CO₂ uptake by triacontanol-treated Chlamydomonas cultures was about the same in both 2 and 21% O2, and the O2 inhibition was significantly reduced as compared with the controls. Photosynthesis in Anacystis was O2-insensitive under the experimental condition used. When Anacystis was treated with triacontanol there was no change in the rate of CO2 uptake and no change in the O2 sensitivity of its CO2 uptake. It appears that triacontanol affects some process which regulated the balance between photosynthesis and photorespiration, but other processes which result in increased growth are probably also affected.     

Subcellular location of an abundant substrate (p36) for tyrosine-specific protein kinases.

A 36,000-dalton cellular protein (p36) has been identified previously as an abundant substrate for phosphorylation by tyrosine-specific protein kinases. Since several of the responsible kinases are associated with the plasma membrane, we explored the subcellular distribution of p36. Biochemical fractionations located p36 on the plasma membrane of both normal and retrovirus-transformed cells. Approximately half of the p36 was bound to the membrane with the affinity of a peripheral membrane protein; the remainder was even more tightly bound. The distribution of p36 among subcellular fractions and its affinity for the plasma membrane were not affected by tyrosine phosphorylation. We determined that p36 is synthesized in the soluble compartment of the cell and then moves rapidly to the membranous compartment. Immunofluorescence microscopy with antibodies directed against p36 revealed two distinct distributions of the antigen: (i) a sharply demarcated crenelated pattern within or immediately beneath the plasma membrane, which we presume to be a correlary of the distribution of p36 in biochemical fractionations; and (ii) diffuse staining in a cytoplasmic location that could not be attributed to a specific feature of cytoarchitecture and could not be easily reconciled with the results of biochemical fractionations. Efforts to detect the secretion of p36 were unsuccessful. No evidence was obtained for exposure of p36 on the cell surface, and no changes in localization were observed as a consequence of neoplastic transformation. During the course of this study, we had the opportunity to pursue a previous report that p36 is a component of the enzyme malate dehydrogenase (Rubsamen et al., Proc. Natl. Acad. Sci. U.S.A. 79:228-232, 1982). We were unable to substantiate this claim. We conclude that at least a substantial fraction of p36 is located on the cytoplasmic aspect of the plasma membrane, where it could be well situated to serve as a substrate for several identified tyrosine-specific kinases. But the function of p36 and its role, if any, in neoplastic transformation of cells by retroviruses possessing tyrosine-specific kinases remain enigmatic.     

Cytological evidence for somatic diploidization in dikaryotic cells ofArmillariella mellea

Dikaryotic hyphae isolated from basidiocarps ofArmillariella mellea are unstable in aseptic culture and change into monokaryotic hypae. During monokaryotization the nuclei of a dikaryon fuse and fusion nucleus immediately divides resulting in two uninucleate cells, from which the monokaryotic mycelium originates. Similar fusion of two nuclei takes place in matings of compatible singlespore isolates. It is concluded that the resulting monokaryotic mycelium is diploid.     

New data on the toxic and radioprotective effect of cysteine onEscherichia coli 15 T- cells

Summary Exponential phase cultures ofE. coli 15 T^- cells growing on glucosemineral medium were supplemented with 2 mM l-cysteine-HCl. The optical density, acid soluble SH (AS-SH) as well as the DNA, RNA, and protein synthesis of the cultures were examined during this treatment and after return to normal growth conditions. Similarly, the survival of cells irradiated by a standard X-ray dose in cysteine-free buffer was measured.The development of radioresistance during the cysteine treatment as well as the loss of this acquired radioresistance after return to normal growth conditions could be divided into two phases: a) an instantaneous and b) a slow change of radioresistance. Phase a seems to be related to the changes occurring in the AS-SH content of the bacteria, while phase b is apparently dependent on the alterations in the synthesis of macromolecules.This work was partly presented at the 6th Annual Meeting of the European Society for Radiation Biology, Interlaken 1968.     

Transforming growth factor-beta does not alter interleukin-1 expression in cultured human macrophages

Transforming growth factor-beta (TGF beta) is a growth modulator that stimulates the growth of fibroblastic cells but inhibits the growth of cells of epithelial origin. TGF beta also influences the production of extracellular matrix proteins, and of proteases and the type 1 plasminogen activator inhibitor (PAI-1) by cultured cells. TGF beta appears also to have various immunoregulatory effects, suppressing both T- and B-cell activities. It has been proposed that it might increase the expression of interleukin-1 (IL-1) mRNA in cultured human monocytes, thus potentiating immune functions. To analyze the role of TGF beta in IL-1 production we have now quantitated the effect of this factor on the production of biologically active IL-1 as well as IL-1 beta mRNA expression. The effect of TGF beta on IL-1 production optimally activated with bacterial lipopolysaccharide (LPS) was also studied. It was found that IL-1 activity and mRNA levels were rapidly elevated by LPS but not by TGF beta. Culture fluids from monocytes treated with TGF beta alone or with TGF beta plus LPS inhibited the proliferation of the test thymocytes. After gel filtration, the media from TGF beta-treated cultures showed no activity in the molecular weight area of IL-1 (approx. 15 kD), while the supernatants from TGF beta plus LPS-induced cells contained IL-1 activity in these fractions, the magnitude of which was, however, at the same level as in the culture fluids derived from cells stimulated with LPS alone.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects on microbial activity by extraction of indigenous cells from soil slurries

Abstract: Possible effects on the physiological activity and culturability of soil microorganisms by different soil dispersion procedures, and effects on activity caused by extracting bacteria from soil, were investigated. There was no apparent difference in cfu's with dispersion of a silty loam soil and a loamy sand soil with pyrophosphate as compared to dispersion in NaCl. Substrate-induced respiration was reduced in the silty loam soil, and methanol oxidation was reduced in the loamy sand soil with dispersion in pyrophosphate, and the soil pH was irreversibly increased by the treatment. Extracted bacterial fractions had lower numbers of culturable cells as percentage of the total number of bacteria in each fraction, lower respiration rates and no methanol oxidation activity as compared to the soil slurry both before and after extraction. The physiological activity was apparently not affected by the number of cells extracted. This indicates that the increased extraction rate of indigenous soil bacteria obtained by effective disruption of aggregates and detachment of cells from surfaces, only results in increased extraction of cells that have been physiologically changed as a result of the extraction process.     

c-Myc induces cellular susceptibility to the cytotoxic action of TNF-alpha.

Tumor necrosis factor-alpha (TNF) is a multifunctional cytokine which is cytotoxic for some tumor cells and transformed cells. The molecular mechanisms which render transformed and tumor cells sensitive to the cytotoxic action of TNF are unclear. We show here that an increased expression of the c-Myc oncoprotein strongly increases cellular sensitivity to TNF cytotoxicity. In Rat1A fibroblasts, which are resistant to TNF, the addition of TNF with a concomitant activation of a hormone-inducible c-Myc-estrogen receptor chimera (MycER) resulted in apoptotic cell death. Similarly, c-Myc overexpression enhanced the sensitivity of NIH3T3 fibroblasts to TNF-induced death. The c-Myc and TNF-induced apoptosis was inhibited by ectopic expression of the Bcl2 oncoprotein and by the free oxygen radical scavenging enzyme Mn superoxide dismutase. Furthermore, in highly TNF-sensitive fibrosarcoma cells, antisense c-myc oligodeoxynucleotides caused a specific inhibition of TNF cytotoxicity. Our results suggest that the deregulation of c-Myc, which is common in human tumors and tumor cell lines is one reason why these cells are TNF sensitive.     

Tyrosine phosphorylation of CD45 phosphotyrosine phosphatase by p50csk kinase creates a binding site for p56lck tyrosine kinase and activates the phosphatase.

Src family protein tyrosine kinases (PTKs) play an essential role in antigen receptor-initiated lymphocyte activation. Their activity is largely regulated by a negative regulatory tyrosine which is a substrate for the activating action of the CD45 phosphotyrosine phosphatase (PTPase) or, conversely, the suppressing action of the cytosolic p50csk PTK. Here we report that CD45 was phosphorylated by p50csk on two tyrosine residues, one of them identified as Tyr-1193. This residue was not phosphorylated by T-cell PTKs p56lck and p59fyn. Tyr-1193 was phosphorylated in intact T cells, and phosphorylation increased upon treatment with PTPase inhibitors, indicating that this tyrosine is a target for a constitutively active PTK. Cotransfection of CD45 and csk into COS-1 cells caused tyrosine phosphorylation of CD45 in the intact cells. Tyrosine-phosphorylated CD45 bound p56lck through the SH2 domain of the kinase. Finally, p50csk-mediated phosphorylation of CD45 caused a severalfold increase in its PTPase activity. Our results show that direct tyrosine phosphorylation of CD45 can affect its activity and association with Src family PTKs and that this phosphorylation could be mediated by p50csk. If this is also true in the intact cells, it adds a new dimension to the physiological function of p50csk in T lymphocytes.