Cloned DNA probes distinguish endemic and exotic Entomophaga grylli fungal pathotype infections in grasshopper life stages

Entomophaga grylli is a fungal pathogen of grasshoppers and at least three pathotypes are recognized world-wide. Pathotypes 1 and 2 are endemic to North America while the Australian pathotype 3 had been released into two field sites in North Dakota between 1989 and 1991. Grasshoppers were collected over the summer at the field sites in 1992 and assessed for pathotype infection by cloned DNA probe analysis. The three most predominant grasshopper species that were infected ( Melanoplus sanguinipes, M. bivittatus and Camnula pellucida ) were assessed for pathotype infection with respect to their life stages (nymphal instars and adult males and females). Pathotype 1 predominantly infected grasshoppers in the subfamilies Oedipodinae and Gomphocerinae and pathotype 2 predominantly infected grasshoppers in the subfamily Melanoplinae. Early-instar M. sanguinipes and M. bivittatus had higher pathotype 2 infection frequencies, while late-instar and adult C. pellucida had higher pathotype 1 infection frequencies. Cross-infection by the pathotypes did occur in up to 3% of the individuals, on a per species basis, and primarily in later instar and adult grasshoppers. Pathotype 3 infections occurred in later instar and adults of the three grasshopper species. Infection of grasshoppers by E. grylli pathotypes is discussed with reference to the fungal life cycles.     

The neutrophil migration induced by tumour necrosis factor alpha in mice is unaffected by glucocorticoids

Macrophages harvested from the peritoneal cavities of rats release a neutrophil chemotactic factor (MNCF) in response to stimulation with Gram-negative bacterial lipopolysaccharide (LPS). MNCF has been shown to be active in rats treated with dexamethasone, a glucocorticoid that usually inhibits the neutrophil migration induced in this species by interleukin (IL)-1, tumour necrosis factor alpha (TNFalpha), IL-8, C5a and leukotriene B(4) (LTB(4)). Here we report that macrophages harvested from peritoneal cavities of mice, and stimulated in vitro with LPS, also release a factor that induces neutrophil migration in dexamethasone-treated animals. This chemotactic activity was neutralized by the incubation of the LPS-stimulated macrophage supernatants with a purified polyclonal IgG anti-mouse TNFalpha. In addition, significant amounts of TNF were detected in the supernatants. The neutrophil migration induced by intraperitoneal administration of recombinant murine TNFalpha was also unaffected by pretreatment of the mice with dexamethasone. Moreover, neutrophil migration induced by intraperitoneal injection of LPS was completely blocked by pretreatment of the mice with a monoclonal antibody against murine TNFalpha. In conclusion, our results support the hypothesis that, in contrast to the role of TNF in rats (where it indirectly induces neutrophil migration), in mice, it may be an important mediator in the recruitment of neutrophils to inflammatory sites.     

Cpn60 is exclusively localized into mitochondria of rat liver and embryonic Drosophila cells

Several reports have claimed that the mitochondrial chaperonin cpn60, or a close homolog, is also present in some other subcellular compartments of the eukaryotic cell. Immunoelectron microscopy studies, using a polyclonal serum against cpn60, revealed that the protein is exclusively localized within the mitochondria of rat liver and embryonic Drosophila cells (SL2). Furthermore, no cpn60 immunoreactive material could be found within the nucleus of SL2 cells subjected to a 1 h 37°C heat-shock treatment. In contrast to these findings, immunoelectron microscopy studies, using a cpn60 monoclonal antibody, revealed mitochondrial and extramitochondrial (plasma membrane, nucleus) immunoreactive material in rat liver cells. Surprisingly, the monoclonal antibody also reacted with fixed proteins of the mature red blood cell. The monoclonal antibody, as well as cpn60 polyclonal sera, only recognize mitochondrial cpn60 in Western blots of liver proteins. Furthermore, none of the cpn60 antibodies used in this study recognized blotted proteins from rat red blood cells. Therefore, we suggest that the reported extramitochondrial localization of cpn60 in metazoan cells may be due to cross-reactivity of some of cpn60 antibodies with conformational epitopes also present in distantly related cpn60 protein homologs that are preserved during fixation procedures of the cells. © 1995 Wiley-Liss, Inc.     

Whitening,thallus decay and fragmentation in Gracilaria chilensis associated with an endophytic amoeba

Whitening of Gracilaria chilensis, accompanied by tissue softening and thallus fragmentation, was found to be associated with the presence of an endophytic amoeba. Although the symptoms developed originally in green mutant thalli, subsequent infections in the laboratory also affected normal, wild-type G. chilensis. Ultrastructural evidence indicates that the amoebae perforate the host cell walls of both cortical and medullary cells and digest their protoplasm. Feeding by the amoeba appears to involve both phagocytosis and enzymatic digestion of the host tissue. Destruction of the host tissue resulted in large cavities first, followed by thallus fragmentation. No other organism was found during the early stages of thallus invasion by the amoeba, although bacteria may appear once the amoeba reaches the inner tissues of the host.     

Osmotic Stress-Induced Polyamine Accumulation in Cereal Leaves : II. Relation to Amino Acid Pools

Arginine decarboxylase activity increases 2- to 3-fold in osmotically stressed oat leaves in both light and dark, but putrescine accumulation in the dark is only one-third to one-half of that in light-stressed leaves. If arginine or ornithine are supplied to dark-stressed leaves, putrescine rises to levels comparable to those obtained by incubation under light. Thus, precursor amino acid availability is limiting to the stress response. Amino acid levels change rapidly upon osmotic treatment; notably, glutamic acid decreases with a corresponding rise in glutamine. Difluoromethylarginine (0.01-0.1 millimolar), the enzyme-activated irreversible inhibitor of arginine decarboxylase, prevents the stress-induced putrescine rise, as well as the incorporation of label from [¹⁴C]arginine, with the expected accumulation of free arginine, but has no effect on the rest of the amino acid pool. The use of specific inhibitors such as α-difluoromethylarginine is suggested as probes for the physiological significance of stress responses by plant cells.     

Cortisol binding in human breast cancer: Correlation with antitumor immunity

Summary The intensity of cortisol binding was measured in the cytosol fraction of the primary tumor obtained from 50 patients with stage I and II breast cancer. The state of cellular antitumor immunity of the same patients was investigated by the tube leucocyte adherence inhibition (LAI) test, performed with peripheral blood leucocytes 1–2 days preoperatively. It was found that the intensity of tumor cortisol binding correlates negatively with LAI values. Patients with high cortisol binding in their tumors have low LAI values, while low tumor cortisol binding is associated with higher antitumor immunity. The results suggest that high cortisol binding in the tumor might inhibit the tumor recognition process and/or the cellular immune defense mechanism and thus facilitate cancer development.     

The electrochemical proton gradient in Escherichia coli membrane vesicles.

Membrane vesicles isolated from Escherichia coli grown under various conditions generate a transmembrane pH gradient (delta pH) of about 2 pH units (interior alkaline) under appropriate conditions when assayed by flow dialysis. Using the distribution of weak acids to measure delta pH and the distribution of the lipophilic cation triphenylmethylphosphonium to measure the electrical potential (delta psi) across the membrane, the vesicles are demonstrated to develop an electrochemical proton gradient (delta-muH+) of almost - 200 mV (interior negative and alkaline) at pH 5.5 in the presence of reduced phenazine methosulfate or D-lactate, the major component of which is a deltapH of about - 120 mV. As external pH is increased, deltapH decreases, reaching 0 at about pH 7.5 and above, while delta psi remains at about - 75 mV and internal pH remains at pH 7.5-7.8. The variations in deltapH correlate with changes in the oxidation of reduced phenazine methosulfate or D-lactate, both of which vary with external pH in a manner similar to that described for deltapH. Finally, deltapH and delta psi can be varied reciprocally in the presence of valinomycin and nigericin with little change in delta-muH+ and no change in respiratory activity. These data and those presented in the following paper (Ramos and Kaback 1976) provide strong support for the role of chemiosmotic phenomena in active transport and extend certain aspects of the chemiosmotic hypothesis.     

Suppressor cells present in the spleens of Trypanosoma cruzi-infected mice.

Infection with Trypanosoma cruzi decreases the ability of spleen cells from mice to respond to either T cell, concanavalin A (Con A), or B cell, lipopolysaccharide (LPS), mitogens. The effect of infection on the mitogenic response depends on the elapsed time between the day of infection and the time of mitogen presentation. Responses early in infection are normal, whereas later responses to either mitogen are depressed. Spleen cells from late trypanosome-infected mice inhibit the ability of normal spleen cells to respond to Con A or LPS. The cell in the T. cruzi-infected spleen cells responsible for this effect is nonadherent, sensitive to treatment with anti-mouse thymus serum plus complement, but insensitive to treatment with anti-immunoglobulin plus complement. These data indicate that infection with T. cruzi elicits over time the generation of T cells suppressive to T and B cell mitogenic responses.     

Ketone bodies in fish skin mucus as an indicator of starvation: a preliminary report

The detection of starvation is a major problem in fish husbandry. Too often the discovery of starving animals is not made until pathogenic organisms are about to overcome the weakened animals. A simple test, using a commercial plastic strip with a reagent area that changes colour in the presence of starvation-induced ketones, was applied to this problem in the mullet, Mugil cephalus. The strip identified ketones in the fish skin mucus, and demonstrated its value in detecting starvation in fishes.