A new class and order of myxozoans to accommodate parasites of bryozoans with ultrastructural observations on Tetracapsula bryosalmonae (PKX organism)

Tetracapsula bryosalmonae, formerly PKX organism, is a myxozoan parasite that causes proliferative kidney disease in salmonid fish. Its primary hosts, in which it undergoes a sexual phase, are phylactolaemate bryozoans. It develops in the bryozoan coelomic cavity as freely floating sacs which contain two types of cells, stellate cells and sporoplasmogenic cells, which become organised as spores. Eight stellate cells differentiate as four capsulogenic cells and four valve cells which surround a single sporoplasmogenic cell. The sporoplasmogenic cell undergoes meiosis and cytoplasmic fission to produce two sporoplasms with haploid nuclei. Sporoplasms contain secondary cells. The unusual development supports previously obtained data from 18S rDNA sequences, indicating that species of Tetracapsula form a clade. It diverged early in the evolution of the Myxozoa, before the radiation that gave rise to the better known genera belonging to the two orders in the single class Myxosporea. The genus Tetracapsula as seen in bryozoans shares some of the characters unique to the myxosporean phase and others typical of the actinosporean phase of genera belonging to the class Myxosporea. However, it exhibits other features which are not found in either phase. A new class Malacosporea and order Malacovalvulida are proposed to accommodate the family Saccosporidae and genus Tetracapsula. Special features of the new class are the sac-like proliferative body, valve cells not covering the exit point of the polar filament, lack of a stopper-like structure sealing the exit, maintenance of valve cell integrity even at spore maturity, absence of hardened spore walls and unique structure of sporoplasmosomes in the sporoplasms.     

Corticotropin releasing hormone and related peptides can act as bioregulatory factors in human keratinocytes

Summary Following previous findings in human skin of the functional expression of genes for the corticotropin releasing hormone (CHR) receptor type 1 (CRH-R1) and CRH itself, we searched for local phenotypic effects for peptides related to CRH. We now report that CRH, sauvagine, and urocortin inhibit proliferation of human HaCaT keratinocytes in a dose-dependent manner. The peptides produced variable cyclic adenosine 3′∶5′-monophosphate stimulation with CRH having the highest potency. Binding of iodine 125 CRH to intact keratinocytes was inhibited by increasing doses of CRH, sauvagine, or urocortin, all showing equal inhibitory potency. Immunocytochemistry identified CRH-R1 immunoreactivity in HaCaT keratinocytes. In conclusion, CRH (exogenous or produced locally) and the related urocortin and sauvagine peptides can modify human keratinocyte phenotype through a receptor-mediated pathway.     

Favorable effect of VEGF gene transfer on ischemic peripheral neuropathy

Ischemic peripheral neuropathy is a frequent, irreversible complication of lower extremity vascular insufficiency. We investigated whether ischemic peripheral neuropathy could be prevented and/or reversed by gene transfer of an endothelial cell mitogen designed to promote therapeutic angiogenesis. Intramuscular gene transfer of naked DNA encoding vascular endothelial growth factor (VEGF) simultaneously with induction of hindlimb ischemia in rabbits abrogated the substantial decrease in motor and sensory nerve parameters, and nerve function recovered promptly. When gene transfer was administered 10 days after induction of ischemia, nerve function was restored earlier and/or recovered faster than in untreated rabbits. These findings are due in part to enhanced hindlimb perfusion. In addition, however, the demonstration of functional VEGF receptor expression by Schwann cells indicates a direct effect of VEGF on neural integrity as well. These findings thus constitute a new paradigm for the treatment of ischemic peripheral neuropathy.     

Oncogenes and inflammation rewire host energy metabolism in the tumor microenvironment

Here, we developed a model system to evaluate the metabolic effects of oncogene(s) on the host microenvironment. A matched set of “normal” and oncogenically transformed epithelial cell lines were co-cultured with human fibroblasts, to determine the “bystander” effects of oncogenes on stromal cells. ROS production and glucose uptake were measured by FACS analysis. In addition, expression of a panel of metabolic protein biomarkers (Caveolin-1, MCT1, and MCT4) was analyzed in parallel. Interestingly, oncogene activation in cancer cells was sufficient to induce the metabolic reprogramming of cancer-associated fibroblasts toward glycolysis, via oxidative stress. Evidence for “metabolic symbiosis” between oxidative cancer cells and glycolytic fibroblasts was provided by MCT1/4 immunostaining. As such, oncogenes drive the establishment of a stromal-epithelial “lactate-shuttle”, to fuel the anabolic growth of cancer cells. Similar results were obtained with two divergent oncogenes (RAS and NFκB), indicating that ROS production and inflammation metabolically converge on the tumor stroma, driving glycolysis and upregulation of MCT4. These findings make stromal MCT4 an attractive target for new drug discovery, as MCT4 is a shared endpoint for the metabolic effects of many oncogenic stimuli. Thus, diverse oncogenes stimulate a common metabolic response in the tumor stroma. Conversely, we also show that fibroblasts protect cancer cells against oncogenic stress and senescence by reducing ROS production in tumor cells. Ras-transformed cells were also able to metabolically reprogram normal adjacent epithelia, indicating that cancer cells can use either fibroblasts or epithelial cells as “partners” for metabolic symbiosis. The antioxidant N-acetyl-cysteine (NAC) selectively halted mitochondrial biogenesis in Ras-transformed cells, but not in normal epithelia. NAC also blocked stromal induction of MCT4, indicating that NAC effectively functions as an “MCT4 inhibitor”. Taken together, our data provide new strategies for achieving more effective anticancer therapy. We conclude that oncogenes enable cancer cells to behave as selfish “metabolic parasites”, like foreign organisms (bacteria, fungi, viruses). Thus, we should consider treating cancer like an infectious disease, with new classes of metabolically targeted “antibiotics” to selectively starve cancer cells. Our results provide new support for the “seed and soil” hypothesis, which was first proposed in 1889 by the English surgeon, Stephen Paget.     

Determination of microvessel permeability and tissue diffusion coefficient of solutes by laser scanning confocal microscopy

Interstitium contains a matrix of fibrous molecules that creates considerable resistance to water and solutes in series with the microvessel wall. On the basis of our preliminary studies, by using laser-scanning confocal microscopy and a theoretical model for interstitial transport, we determined both microvessel solute permeability (P) and solute tissue diffusion coefficient (D) of alpha-lactalbumin (Stokes radius 2.01 nm) from the rate of tissue solute accumulation and the radial concentration gradient around individually perfused microvessel in frog mesentery. P(alpha-lactalbumin) is 1.7 +/- 0.7(SD) x 10(-6) cm/s (n = 6). D(t)/D(free) for alpha-lactalbumin is 27% +/- 5% (SD) (n = 6). This value of D(t)/D(free) is comparable to that for small solute sodium fluorescein (Stokes radius 0.45 nm), while p(alpha-lactalbumin) is only 3.4% of p(sodium fluorescein). Our results suggest that frog mesenteric tissue is much less selective to solutes than the microvessel wall.     

Effect of neurotensin on pancreatic function in man

The effect of neurotensin on submaximally-stimulated hepatobiliary and pancreatic secretion was studied in 6 healthy subjects. An intravenous infusion of neurotensin 1.4 ± 0.3 pmol/kg/min, designed to reproduce plasma neurotensin immunoreactivity levels within the physiological range, produced a significant increase in pancreatic bicarbonate output. Plasma concentrations of pancreatic polypeptide rose by 83 ± 16 pmol/l and were associated with a small reduction in trypsin, but no significant change in bilirubin outputs.     

The effect of unphosphorylated and phosphorylated sugar moieties on human and mouse natural killer cell activity: is there selective inhibition at the level of target recognition and lytic acceptor site?

A number of different sugars were investigated for their effect on human and mouse natural killer cell (NK)-mediated cytolysis. From the pool of nonphosphorylated sugars, D-mannose, N-acetyl-D-glucosamine (NAcGlc), D-glucose, and, to a lesser extent, beta-gentiobiose were found to inhibit human NK cytolysis. Mouse NK activity against YAC-1 target cells was reduced consistently in the presence of D-mannose and NAcGlc only. The sugars, NAcGlc, D-glucose, and beta-gentiobiose, were specifically inhibitory against NK-mediated cytolysis with no inhibitory effects being observed against ADCC, monocyte-mediated cytolysis, or CTL activity. Pretreatment and washing at either the target or effector cell level as well as direct target binding assays using Percoll-purified NK cells indicated that at least NAcGlc and beta-gentiobiose function at the recognition stage of NK cytolysis. D-Mannose, which was the most effective nonphosphorylated sugar inhibitor, was capable of inhibiting all cell-mediated cytotoxic mechanisms tested (NK, ADCC, monocyte, and CTL) and its action did not appear to be solely due to an impairment in the recognition event. All the phosphorylated sugars caused significant inhibition of human and mouse NK-mediated cytolysis, although repeated analyses of sugar titration curves consistently showed mannose-6-phosphate (Man-6-P) to be the most effective inhibitor. Inhibition with the phosphorylated sugars was apparent against all cytotoxic mechanisms investigated. It is possible that these sugars may function as general metabolic inhibitors or may activate a common signal which negatively regulates cell-mediated cytotoxic mechanisms. Nevertheless, the relative degree of inhibition with the majority of these sugars (particularly Man-6-P) was greater against NK and ADCC activity than against monocyte and CTL activity. Furthermore, studies with selected well-characterized human and mouse NK-resistant target cells strongly indicated that these sugars, particularly Man-6-P, compete at an acceptor site responsible for the uptake of the NK lytic factor, which is independent of the recognition structure(s).     

Ecology,development and pathogenicity of Buddenbrockia plumatellae Schröder, 1910 (Myxozoa,Malacosporea) (syn. Tetracapsula bryozoides) and establishment of Tetracapsuloides n. gen. for Tetracapsula bryosalmonae

Buddenbrockia plumatellae, an enigmatic worm-like myxozoan, was observed as continuously writhing free and attached 'worms' and as free mature spores in the coelom of the freshwater bryozoans Plumatella fungosa, Hyalinella punctata, and Fredericella sp. 'Worm' numbers could double every three days. 'Worms' and spores could be expelled from colonies by external pressure. Some mature 'worms' exited actively, entraining release of free spores, and gradually ceased movement outside the host. Bryozoans sealed off infected regions of the colony. Infected colonies grew slowly, produced no statoblasts, and eventually regressed and died. Transmission was not achieved and prevalence was low. Electron microscopy of 'worms' revealed a single layer of mural cells on a fibrous basal lamina overlying four longitudinal muscle blocks and an inner sheet of two types of proliferating cells, an organization indicative of the bilaterian ancestry of the Myxozoa. Primary type A cells were attached directly by striated tubules to mural cells at positions between muscle blocks. Secondary type A cells had a secretory function. Type B cells underwent meiosis and subsequently developed to typical malacosporean myxozoan spores filling the internal cavity of the 'worms'. External tubes were formed during capsulogenesis in 'worms' from Fredericella sp. Tetracapsula bryozoides is synonymised with Buddenbrockia plumatellae and a new genus is proposed for Tetracapsula bryosalmonae.