Detection and control of occult mycoplasma contamination in human tumor cell lines

Summary Mycoplasma contamination of established cell lines is a well-known but often poorly controlled artefactual problem in immunological studies of human tumor cell lines. We have evaluated four methods for detecting mycoplasmas in cell lines, namely direct culture, DNA staining, uridine phosphorylase assay, and a fourth technique based on our finding that the supernatant medium of mycoplasma-infected cell cultures inhibits thymidine uptake of mitogen-stimulated peripheral blood lymphocytes. In our hands the simplest, most reliable, and least expensive means of monitoring cell cultures for mycoplasma proved to be DNA staining. The uridine phosphorylase assay was unsuitable for use with melanoma cell lines, as six of eight lines that were negative with the other three techniques were positive with this assay.Of 14 contaminated cell lines injected to nude mice, eitht produced tumors, five of which were shown to be mycoplasma-free after one to five passages, confirming the usefulness of this approach for salvaging contaminated cell lines.     

Behaviour of dictyostelium discoideum amoebae and Escherichia coli grown together in chemostat culture

When Dictyostelium discoideum amoebae and Escherichia coli were grown together in chemostat culture damped oscillations in the popullation densities of the organisms occurred followed by a sudden increase in bacterial numbers and a concommitant decrease in the number of amoebae. After the system had come to equilibrium altering the dilution rate resulted in a monotonic change in the experimental variables to new steady state levels. A square wave increase in the concentration of limiting nutrient in the feed medium during the oscillatory phase of culture produced a sinusoidal response indistinguishable from that prior to the perturbation. The results are more complicated than those predicted by simple models of microbial predator-prey dynamics although they correspond most nearly to models which incorporate saturation kinetics.     

Neratinib degrades MST4 via autophagy that reduces membrane stiffness and is essential for the inactivation of PI3K,ERK1/2, and YAP/TAZ signaling

The irreversible ERBB1/2/4 inhibitor neratinib causes plasma membrane-associated K-RAS to mislocalize into intracellular vesicles liminal to the plasma membrane; this effect is enhanced by HDAC inhibitors and is now a Phase I trial (NCT03919292). The combination of neratinib and HDAC inhibitors killed pancreatic cancer and lymphoma T cells. Neratinib plus HDAC inhibitor exposure was as efficacious as (paclitaxel+gemcitabine) at killing pancreatic cancer cells. Neratinib reduced the phosphorylation of PAK1, Merlin, LATS1/2, AKT, mTOR, p70 S6K, and ERK1/2 which required expression of Rubicon, Beclin1, and Merlin. Neratinib altered pancreatic tumor cell morphology which was associated with MST4 degradation reduced Ezrin phosphorylation and enhanced phosphorylation of MAP4K4 and LATS1/2. Knockdown of the MAP4K4 activator and sensor of membrane rigidity RAP2A reduced basal LATS1/2 and YAP phosphorylation but did not prevent neratinib from stimulating LATS1/2 or YAP phosphorylation. Beclin1 knockdown prevented MST4 degradation, Ezrin dephosphorylation and neratinib-induced alterations in tumor cell morphology. Our findings demonstrate that neratinib enhances LATS1/2 phosphorylation independently of RAP2A/MAP4K4 and that MST4 degradation and Ezrin dephosphorylation may represent a universal trigger for the biological actions of neratinib.     

Contact structures in the poultry industry in Great Britain: Exploring transmission routes for a potential avian influenza virus epidemic

Background  

The commercial poultry industry in United Kingdom (UK) is worth an estimated ￡3.4 billion at retail value, producing over 174 million birds for consumption per year. An epidemic of any poultry disease with high mortality or which is zoonotic, such as avian influenza virus (AIV), would result in the culling of significant numbers of birds, as seen in the Netherlands in 2003 and Italy in 2000. Such an epidemic would cost the UK government millions of pounds in compensation costs, with further economic losses through reduction of international and UK consumption of British poultry. In order to better inform policy advisers and makers on the potential for a large epidemic in GB, we investigate the role that interactions amongst premises within the British commercial poultry industry could play in promoting an AIV epidemic, given an introduction of the virus in a specific part of poultry industry in Great Britain (GB).     

Tertiary Hyperparathyroidism

In our first 200 cases of primary hyperparathyroidism confirmed by operation 12 were also shown to have a long history either of a malabsorption syndrome or of chronic renal-glomerular failure. We consider that they first went through a phase of secondary hyperparathyroidism, during which one or more of the glands became autonomous adenamata. This then produced the biochemical changes of “primary” hyperparathyroidism, necessitating excision of the adenoma. This condition is best described as “tertiary” hyperparathyroidism. The transition from secondary to tertiary hyperparathyroidism occurred in four of the 12 patients while under our observation. We think the same process can be traced retrospectively in the other eight cases. The concept of tertiary hyperparathyroidism may help to explain the high incidence of other diseases in association with primary hyperparathyroidism.The behaviour of the parathyroid glands provides a valuable model for the investigation of tumour formation in man. All states occurred in our patients with primary hyperparathyroidism, from normal through hyperplasia to adenoma formation and finally to parathyroid carcinoma.     

Cortical neurite outgrowth and growth cone behaviors reveal developmentally regulated cues in spinal cord membranes

Corticospinal axon outgrowth in vivo and the ability to sprout or regenerate after injury decline with age. This developmental decline in growth potential has been correlated with an increase in inhibitory myelin‐associated proteins in older spinal cord. However, previous results have shown that sprouting of corticospinal fibers after contralateral lesions begins to diminish prior to myelination, suggesting that a decrease in growth promoting and/or an increase in inhibitory molecules in spinal gray matter may also regulate corticospinal axon outgrowth. To address this possibility, we carried out in vitro experiments to measure neurite outgrowth from explants of 1‐day‐old hamster forelimb sensorimotor cortex that were plated onto membrane carpets or membrane stripe assays prepared from white or gray matter of 1‐to 22‐day‐old cervical spinal cord. On uniform carpets and in the stripe assays cortical neurites grew robustly on young but not older membranes from both white and gray matter. Mixtures of membranes from 1‐ and 15‐day spinal cord inhibited neurite outgrowth, suggesting that the presence of inhibitory molecules in the 15‐day cord overwhelmed permissive or growth promoting molecules in membranes from 1‐day cord. Video microscopic observations of growth cone behaviors on membrane stripe assays transferred to glass coverslips supported this view. Cortical growth cones repeatedly collapsed at borders between permissive substrates (laminin or young membrane stripes) and nonpermissive substrates (older membrane stripes). Growth cones either turned away from the older membranes or reduced their growth rates. These results suggest that molecules in both the gray and white matter of the developing spinal cord can inhibit cortical neurite outgrowth. © 1999 John Wiley & Sons, Inc. J Neurobiol 39: 393–406, 1999     

Effect of inhaled platelet-activating factor on circulating neutrophils and platelets in vivo and ex vivo in man

We studied the effect of five successive inhalations of platelet-activating factor (PAF) on airway calibre, circulating neutrophil and platelet counts and the activation of these cells ex vivo in normal subjects. PAF (24 ug) caused a mean maximal fall of the expiratory flow rate at 70% vital capacity from a partial manoeuvre (Vp30) of 46.4 +/- 6.2% (p less than 0.001); there was a tachyphylactic response to further doses of PAF. Circulating neutrophil counts fell by 54.3 +/- 10.6% (p less than 0.005) with immediate recovery and with a rebound neutrophilia by the fifth inhalation. Platelet counts showed no significant changes. Aggregation of platelets in platelet-rich plasma to PAF and ADP in vitro at 15 min after the first, second and fifth PAF inhalations was not significantly altered. Chemiluminescence responses of neutrophils to PAF (0.01, 0.1, 1 and 10 microM) in vitro were reduced at 15 min after the fifth PAF inhalation, but this was only significant at 1 microM PAF. Methacholine inhalation did not cause any changes in responsiveness of neutrophils to PAF ex vivo. We conclude that ex vivo platelet desensitisation cannot be used as an index of endogenous PAF release, but reduced responsiveness of neutrophils ex vivo is not a sensitive indicator.