Stimulation of growth and phospholipase A2 by the peptides mastoparan and melittin and by the auxin 2,4-dichlorophenoxyacetic acid

The peptide mastoparan from wasp venom and the peptide melittin from bee venom stimulated growth in etiolated zucchini (Cucurbita pepo L.) hypocotyls. Both peptides were only effective in hypocotyls with abraded cuticles. At concentrations of 2 g ml^–1 peptide growth was stimulated 72% by mastoparan and 50% by melittin after 2 h as compared to the controls. Mastoparan (5 g ml^–1), melittin (10 g l^–1) and 2,4-dichlorophenoxyacetic acid (5×10^–4 M) stimulated accumulation of ¹⁴C-choline-labeled lysophosphatidylcholine in less than 10 min in cultured soybean cells (Glycine max L.), all to about the same extent. The effects of these peptides are among the first to be reported on plant cells and may be related to important events coupled to growth stimulation.Abbreviations 2,4-D 2,4-dichlorophenoxyacetic acid     

On the generalization of the logistic law of growth

This communication presents a discussion of some extensions of the formalism of Verhulst's simple logistics, which may constitute an autonomous growth model of a more general scope.For that purpose, the basis concept of growth diagram or trajectory is called upon, as it affords the graphic representation of the change in the growth variable y, using two relevant kinetic parameters: the instantaneous rate and the instantaneous acceleration. The two possible kinds of trajectories are in relation to the use of absolute (V = dyldt; = dV/dt) or relative (or specific) values (R = (1/y)(dy/dt); _R = dR/dt).In the case of simple logistics, the trajectory (V, ) allows 4 growth phases or states to be distinguished. The diagram (R, _R ) shows that the deceleration of the specific rate is not monotonous.In the case of Richards - Nelder's generalized logistics, the qualitative variation of the growth trajectory depends on the value of the dissymmetry parameter (occurrence of a critical value which determines the number of growth states).Blumberg's model is characterized by an analogous property and, moreover, can account for a non monotonous variation of the specific growth rate.     

A new thermodynamically based correlation of chemotrophic biomass yields

A new, generally applicable, thermodynamically based method is proposed to provide an estimation of the biomass yield on arbitrary organic and inorganic substrates. Aerobic, anaerobic, denitrifying growth systems with and without reversed electrontransport are covered. The biomass yield can be estimated with only 15% error in a very wide range of microbial growth systems and biomass yields (0.01–0.80 C-mol/(C)-mol). This method is based on the use of Gibbs energy dissipared per C-mol produced biomass (designated as D _infS ^sup01 /r_Ax) as the central parameter. Moreover the insufficiency of other methods based on Y_ATP, Y_Ave, ₀, Y_C and enthalpy or Gibbs energy efficiencies is shortly discussed. Also it appeared to be possible to understand the obtained correlation of D _infS ^sup01 /r_Ax in general biochemical terms.     

Fermentation of L-tartrate by a newly isolated gram-negative glycolytic bacterium

Enrichments on L-tartrate from a freshwater lake sediment yielded a pure culture of anaerobic bacterium designated strain 16Lt1. The rod-shaped organism was motile, did not form spores, and had a gram-negative wall structure. No cytochromes were detected. The mol % G+C of the DNA was 58. The new strain was microaerotolerant, and grew optimally at 30°C and neutral pH in freshwater medium. A wide range of carbohydrates was fermented, with formate, acetate, ethanol, lactate and succinate being the end-products detected. L-tartrate and citrate were fermented to formate, acetate and CO₂. L-tartrate was fermented by the dehydratase pathway, and glucose by the Embden-Meyerhof-Parnas pathway. Fumarate was reduced, but nitrate, sulfate, sulfur and thiosulfate were not used as terminal electron acceptors. Glucose metabolism was constitutive, whereas L-tartrate-degrading activity was inducible. When glucose and L-tartrate were both present as substrates, growth was diauxic with glucose being metabolized first. The growth rate and growth yield were higher on glucose than on L-tartrate. Strain 16Lt1 has been deposited with the Deutsche Sammlung von Mikroorganismen as Bacteroides sp. DSM6268.     

Microcarrier culture of bowes melanoma cells in serum-free medium with Human plasma fraction IV-4+ V

Bowes melanoma cells were cultivated successfully in a serum-free medium which was constructed by the concept of maximum retention of proteins from fractionated human plasma having growth stimulatory activities. The cells could be cultivated in the serum-free medium without any adaptation period. The major serum-free component of the medium was the fraction IV-4 + V of the Cohn fractionation process of human plasma. Approximately six times increase of tissue-type plasminogen activator (t-PA) activity as compared with that in serum-free medium even though the cell growth was much slower. In addition, the growth stimulatory activities of thrombin and fibronectin were investigated during the cultivation of Bowes melanoma cells in this serum-free medium. These proteins contributed significantly to the enhanced growth of cells by reducing doubling time to 25 and 35 h as compared with 55 h in the serum-free medium without them. Especially, fibronectin supported cells to propagate near to the maximum cell density achieved in the medium with 10% FBS.     

A segment of rye chromosome 1 enhances growth and embryogenesis of calli derived from immature embryos of wheat

Summary The influence of the short arm of rye chromosome 1 (1RS) from Secale cereale var. Imperial on the growth and differentiation of callus cultures from wheat Triticum aestivum var. Chinese Spring immature embryos was analysed. This chromosome arm was found to stimulate both embryogenesis and the rate of growth of calli. Recombinant lines carrying segments of 1RS were used to delineate the regions of 1RS responsible for the tissue culture effects. The enhancement of embryogenesis and the stimulation of growth were shown to be associated with two distinct genetic regions of the chromosome arm; the former is located between the centromere and the Sec 1 locus, while the latter is situated in the immediate vicinity of the Sec 1 locus.     

Release of basic fibroblast growth factor,an angiogenic factor devoid of secretory signal sequence: A trivial phenomenon or a novel secretion mechanism?

Basic fibroblast growth factor (bFGF), a potent angiogenesis inducer, lacks a signal sequence. Therefore, it has been proposed that bFGF is primarily released from dead or damaged cells. Other proteins devoid of secretion signals, interleukin 1 beta (IL-1 beta) and the muscle lectin L-14, have been shown to be released via exocytosis, a novel secretion pathway independent of the "classic" endoplasmic reticulum-Golgi route. In the light of these findings and of our own recent results, we discuss evidence that bFGF can be released from single, uninjured cells and mediate functions in an autocrine manner. As is the case for IL-1 beta and L-14, externalization of bFGF may occur via exocytosis, a pathway utilized during development and differentiation.     

Buffering of intracellular calcium in response to increased extracellular levels in mortal, immortal, and transformed human breast epithelial cells.

Extracellular levels of calcium at 1.05 mM or higher induce terminal differentiation and senescence in the mortal (MCF-10M) line of human breast epithelial cells, but does not retard the growth or induce differentiation in the immortal (MCF-10A) and oncogene transformed (MCF-10AneoT) lines. Intracellular levels of calcium and inositol triphosphate were determined in MCF-10M, MCF-10A, and MCF-10AneoT, under conditions of low and high extracellular calcium. We hereby report that increases in extracellular calcium is translated into significant increases in intracellular levels of calcium and inositol triphosphate in MCF-10M, but not in MCF-10A and MCF-10AneoT. This difference in the apparent calcium buffering capacity between the mortal and the immortalized human breast epithelial cells could account for the latter's unperturbed growth potential in high extracellular calcium environment.     

Estrogen-stimulation of postconfluent cell accumulation and foci formation of human MCF-7 breast cancer cells

Foci, nodules of cellular overgrowth, that appear after confluence are an in vitro characteristic of malignant transformation. A well-studied in vitro model of estrogen-dependent tumors is the MCF-7 cell line, derived from a pleural metastasis of a human breast adenocarcinoma. We report that cultivation of MCF-7 cells, using routine methods, results in extensive estrogen-stimulated postconfluent cell accumulation characterized by discrete three-dimensional arrays. Side view Nomarski optical sections revealed these to be principally multicellular foci with occasional domes and pseudoacinar vacuoles. This effect on MCF-7 cell growth occurs in media containing fetal bovine serum but not with calf serum or charcoal-dextran-treated fetal bovine serum unless supplemented with estrogens. Foci formation starts 5-6 days after confluence, and the number of foci generated is a function of the concentration of added estrogens. Foci formation is suppressed by the antiestrogens Tamoxifen and LY 156758. Addition of progesterone, testosterone, or dexamethasone had little or no effect, while various estrogens (ethinyl estradiol, diethylstilbestrol, and moxestrol) induced foci development. Clones derived from single cells of the initial MCF-7 population revealed a wide variance in estrogen-induced foci formation, demonstrating heterogeneity of this tumor cell line. The postconfluent cell growth of the estrogen receptor-deficient cell line, MDA-MB-231, contrasted with MCF-7 by developing an extensive multilayer morphology devoid of discrete structures. The tumorigenic potential of the MCF-7 cells used in our experiments was confirmed by their estrogen-dependent growth in immunosuppressed male BDF1 mice. These data suggest an estrogen receptor-based mechanism for the development of multicellular foci during postconfluent growth of MCF-7 cells. After confluence, foci, in contrast to the quiescent surrounding monolayer, retain proliferating cells. Focus formation, therefore, reflects the heterogeneous responsiveness of these cells to estrogens and should provide a model permitting in vitro comparisons between the progenitor cells of multicellular foci and the monolayer population.     

Constitutive production of lymphocyte activating factors by normal tissues in the adult rat

Lymphocyte activating factors (LAFs), e.g., interleukin-1 (IL-1) and IL-1-like factors, have previously been demonstrated outside the immune system in the skin, thymus epithelium, and the human and rat testis. We have studied the presence of LAFs in normal tissues of the adult rat, utilizing a highly IL-1 sensitive murine thymocyte proliferation assay. We have demonstrated high amounts of LAF activity in the tongue, esophagus, proventricular part of the stomach, and the liver. Some activity was also demonstrated in the duodenum, placenta, spleen, Peyer's patches, glandular stomach, and jejunum, but no bioactivity was present in other gastrointestinal, endocrine, lymphoid, or haematopoeitic tissues. We were also unable to detect any LAF activity in the reproductive organs (except for the testis), urinary tract, skeletal and muscular tissues, brain, eyes, salivary glands, or lung. In the esophagus the activity was mainly localized to the mucosa. The LAF activity in the skin was partly inhibited by treatment with a mixture of antibodies against human IL-1 alpha and IL-1 beta. Dose response curves and gel filtration on a Sephacryl S-200 column suggested the presence of a high molecular weight (90,000-100,000 Da) LAF inhibitory factor in the liver. In all positive tissues, the demonstrated LAFs had a molecular weight of 15,000-25,000 Da, as determined by Sephacryl S-200 gel filtration. Of the positive tissues, the skin, tongue, esophagus, and the proventricular part of the stomach all contain stratified squamous epithelium. It is tempting to suggest that the detected LAFs have a similar function in these barrier tissues, e.g., to serve as host defence factors, or, alternatively or additionally, as tissue growth factors.