The rat MIS1/Pvt-1 locus is syntenic with MYC on chromosome 7

Mouse Pvt-1 and rat MIS1 are frequent proviral integration sites in retrovirally induced lymphomas. The Pvt-1 locus is also involved in mouse plasmacytoma (6;15) and in the variant Burkitt lymphoma (2;8) translocations. We show that the Pvt-1/MIS1 locus is syntenic with MYC on rat chromosome 7. This is consistent with a postulate of close linkage and, possibly, a functional relationship between the MYC protooncogene and the MIS1/Pvt-1 locus.     

Continuous microbial desulfurization of coal--application of a multistage slurry reactor and analysis of the interactions of microbial and chemical kinetics

Microbial desulfurization of coal by pyrite oxidizing bacterial enrichment cultures has been studied in air-agitated slurry reactors of 4- and 20-L volumes. Batch experiments showed that inoculation with an active bacterial culture is essential to minimize the lag phase, although a considerable number of pyrite oxidizing bacteria was found on the coal prior to desulfurization. For detailed investigations of kinetics, energy requirements, and technical applicability, a bioreactor equipment consisting of a cascade of eight stages was developed and operated continuously. Microbial desulfurization of coal-monitored by measuring the axial profile of dissolved iron concentration, real and maximum oxygen consumption rates, and cell concentration-at pulp densities to 30% was performed over a period of 200 days without any disturbances concerning the aeration system, fluidization, transport of solids and microbial growth. At a pulp density of 20%, a pyrite conversion of 68% was achieved after the third reactor stage at a total residence time of five days in the first three stages. The kinetics of pyrite degradation were found to be well described by a rate equation of first order in pyrite surface area concentration if the pyrite is directly accessible for microbial attack. Rate constants were determined to 0.48 mg pyrite/(cm(2) day) in the first and to 0.24 mg pyrite/(cm(2) day) in the following reactor stages. Kinetic models taking into account adsorption/desorption as well as growth kinetics failed to describe the observed reaction rates. However, a model treating pyrite degradation and microbial growth kinetics formalistically seems to be applicable when backmixing between the reactor stages can be avoided. The advantage of a multistage reactor in comparison to single-stage equipment was shown by calculation. To obtain a pyrite conversion of 68%, a three-stage reactor would require only 58% of the volume of single-stage equipment.Measurement of oxygen consumption rates proved to provide quickly and easily measurable parameters to observe microbial coal desulfurization in technical scale: the real oxygen consumption rate is correlated to the pyrite oxidation rate and the maximum oxygen consumption rate is correlated to the concentration of viable cells. The Y(o/s) coefficient for the amount of oxygen consumed per mass unit of pyrite oxygen was determined to approximately 0.33 in comparison to 1.0 which can be calculated from stoichiornetry. This could yet not be explained. Chemical leaching experiments as well as sulfur analyses of desulfurized coal samples showed that the microorganisms play the main role in degradation of pyrite from coal and that pyrite oxidation by ferric iron can be neglected.     

The kinetics of generation of influenza-specific cytotoxic T-lymphocyte precursor cells

A dramatic increase in the number of restimulatable (memory) cytolytic T-cell precursors (CTLps) has been demonstrated to occur 2 to 4 days postimmunization. By 4 or at the latest 6 days following in vivo priming, the frequency of restimulatable influenza-specific CTLps has reached that characteristic of a memory response. This indicates that the proliferative events which give rise to memory CTLps occur earlier than might have been expected and in fact are completed prior to the cessation of othe primary CTL response. Such information may have important significance to future immunomodulatory efforts aimed at perturbing the establishment of T-cell memory in vivo.     

Photocontrol of Dark Circadian Rhythms in Stomata of Phaseolus vulgaris L

Stomatal diffusion resistance in primary leaves of Phaseolus vulgaris L. which had been grown in light:dark cycles followed a marked circadian rhythm when the plants were transferred to continuous darkness. Reentrainment of the rhythm required more than one inductive change in photoperiod. The phasing of the rhythm of dark stomatal opening was contolled primarily by the light-on (dawn) signal, whereas the rhythm of dark closure was related to the light-off (dusk) signal. The evidence points to a dual control of the circadian clock in which a product of photosynthesis plays a major role. No evidence for phytochrome involvement in the phasing of the rhythm was found. An influence of phytochrome on the amplitude of the stomatal rhythm was observed in which removal of phytochrome-far-red absorbing form caused rapid damping.     

Insulin activation of insulin receptor tyrosine kinase in intact rat adipocytes. An in vitro system to measure histone kinase activity of insulin receptors activated in vivo

We have studied the effect of incubation of intact cells with insulin on insulin receptor kinase activity. Following exposure of rat adipocytes to insulin, cells were solubilized and insulin receptors purified by specific immunoprecipitation or by insulin affinity chromatography. Kinase activity of the receptors, as measured by phosphorylation of histone 2B, was then determined. Insulin treatment of the cells resulted in a 10-20-fold increase in histone kinase activity of the subsequently isolated insulin receptors. The insulin effect was half-maximal at 3 s and maximal within 15 s of exposure, was dose-dependent (EC50 = 21 ng/ml), and was rapidly reversible following dissociation of insulin from the cells. The insulin effect in intact cells on insulin receptor kinase activity could be partially reversed in vitro by dephosphorylation of the isolated receptors by alkaline phosphatase. It is proposed that: in intact cells, insulin causes alterations in insulin receptors, such that their kinase activity toward non-receptor substrates increases; increased insulin receptor kinase activity following insulin stimulation in intact cells is, at least in part, the result of an increased phosphate content of the receptors; and effects of insulin on insulin receptors in intact cells can be preserved during receptor isolation and thus can be measured in a cell-free system.     

Development of heart cells in culture: studies using an affinity purified antibody to a myosin light chain

Cultured neonatal rat heart cells can be used to study the factors that regulate cardiac contractility and myocyte development in vitro. An antibody to the 26,000 dalton light chain of myosin (MLC1), has been produced and purified on a Sepharose 4B affinity column prepared with rat heart myosin. When primary cultures of myocytes are studied by indirect immunofluorescence using this antibody a predictable pattern of myofibrillar structure is observed to develop over 72 h. This myosin cytoskeleton is highly organized and the myosin fibrils exhibit cross striations. The antibody does not stain non-muscle heart cells and there is no evidence for myocyte division in culture. The qualitative immunofluorescent pattern of myosin organization is the same in both spontaneously beating and in non-contracting cells.     

Extracellular lumazine from aggregating Dictyostelium discoideum cells. Influence of pH on its fluorescence

Lumazine has been demonstrated to be one of the two main compounds responsible for the extracellular fluorescence linked with the aggregation ability of Dictyostelium discoideum, strain Ax-2. The other compound, also having lumazine properties, is, however, different from the 7-hydroxylumazine proposed previously. The influence of pH on the fluorescence of lumazine was studied. The possible use of extracellular pteridines as pH markers was stressed and a method for the determination of the amount of "lumazine equivalents" in the extracellular medium of aggregating D. discoideum cells is elaborated.     

Human autologous rosettes. IV. Their relation with interleukin 2 activity production and natural killer cells in cancer patients

Peripheral blood lymphocytes (PBL) of solid-tumor-bearing cancer patients produced a lower interleukin 2 (IL-2) activity after lectin stimulation than did those from normal subjects. Moreover natural killer (NK) cell activity and autologous rosette forming (ARF) cell rate are found significantly correlated with IL-2 production in these patients. No direct relation is observed between ARF cell ratio and NK cell activity in a given patient. A central role for IL-2 in cancer patient immune dysfunctions is suggested. Two lines of pathogenetic mechanisms are documented. First, PBL exhibited cellular function defects, namely, autologous receptor expression, IL-2 production, and NK activity. Second, these dysfunctions involved, at least partly, plasma factors. The possibility of specific deficiency, (e.g., thymic factors) is not documented. Conversely it is demonstrated that patient plasma contain immunosuppressive factor(s) that block(s) IL-2 production and ARF cell expression. Involvement of ARF cell receptor in T-cell activation is discussed.