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The greater wax moth Galleria mellonella is a worldwide insect pest damaging wax combs and feeding on bee-hive products. The objective of the current study was to investigate the cytopathological impacts of four plant growth regulators (PGRs), viz., indole-3-acetic acid, indole-3-butyric acid, 2,4-Dichlorophenoxy acetic acid and 6-benzyladenine, on the circulating hemocytes of last (7th) instar larvae of G. mellonella. For this purpose, the 3rd instar larvae were force-fed on diet supplemented with LC50 values of these PGRs (0.24, 0.022, 0.16 & 0.085 ppm, respectively). These larvae were continuously fed on the treated diet throughout the larval stage. The important results could be summarized as follows. Five main types of the freely circulating hemocytes in the haemolymph of larvae had been identified as Prohemocytes (PRs), Plasmatocytes (PLs), Granulocytes (GRs), Spherulocytes (SPs) and Oenocytoids (OEs). Different qualitative disorders of the profile of each circulating hemocyte type were demonstrated in thelast instar larvae, such as destruction of cell nuclei and/or membrane, some extruded cytoplasmic contents, and production of some vacuoles in the cytoplasm. However, some of the tested PGRs failed to exhibit cytopathological impacts on certain hemocytes, since IAA and 6-BA failed to affect PLs, IBA and 6-BA failed to affect GRs, IBA and 6-BA failed to affect SPs and IBA and 6-BA failed to affect OEs. Therefore, IAA and 2,4-D may be recommended to use in the IPM program against G. mellonella [ABSTRACT FROM AUTHOR]

Abstract Thaumetopoeapityocampa is an important pine pest in the Mediterranean basin and central Europe. The insecte is a butterfly, whose larvae are called pine processionary caterpillars. To understand the resistance mechanism of the insect in order to proceed of its control and to diminuate their effect in nature, it was necessary to study of the immune system and reactions of the larva in different stages. The aim of our work is to identify the hemocytes formula of the caterpillar during the larval stages L2, L3, and L4, as well as the quantification of the different cells during each stage. After extraction of the hemolymph by centrifugation, the cells were placed in culture medium and then incubated. Microscopic observation has shown that prohemocytes population appear early in hemolymph, they differentiate into plasmatocytes and granulocytes during the advanced stages. However, the quantification process (THC), carried out in a Malassez counting chamber has shown that granulocytes are the most abundant cell population in the hemolymph of the insect larvae. To investigate the role of hemocytes in immune responses, we have co-incubate T. pityocampa cells with bacteria, entomopathogenic nematodes, and synthetic beads. Both humoral and cellular encapsulation processes have been observed early in larval stages, all hemocytes seem to be involved in the formation of nodules and capsules against bacteria and microbeads. At the opposite, entomopathogenic nematodes (Steinernemafeltiae) were not recognized and encapsulated, but their presence can strongly damage host hemocytes. [ABSTRACT FROM AUTHOR]

Stem cells are regulated by signals from their microenvironment, or niche. During Drosophila hematopoiesis, a niche regulates prohemocytes to control hemocyte production. Immune challenges activate cell-signalling to initiate the cellular and innate immune response. Specifically, certain immune challenges stimulate the niche to produce signals that induce prohemocyte differentiation. However, the mechanisms that promote prohemocyte differentiation subsequent to immune challenges are poorly understood. Here we show that bacterial infection induces the cellular immune response by modulating occluding-junctions at the hematopoietic niche. Occluding-junctions form a permeability barrier that regulates the accessibility of prohemocytes to niche derived signals. The immune response triggered by infection causes barrier breakdown, altering the prohemocyte microenvironment to induce immune cell production. Moreover, genetically induced barrier ablation provides protection against infection by activating the immune response. Our results reveal a novel role for occluding-junctions in regulating niche-hematopoietic progenitor signalling and link this mechanism to immune cell production following infection.

The hemocytes of the American bollworm Helicoverpa armigera (Hübner) were studied in the last instar larvae by phase contrast microscopy to investigate the differences among 14 populations, collected from ten locations, spread over a distance of approximately 3000 km in six different states of India. The cluster analysis of differential hemocytes showed as many as 11 clusters of populations at 5% and six clusters at 10% homogeneity level. The cluster analysis of hemocytes of seven populations from cotton crops showed five and three clusters at 5% and 10% homogeneity levels, respectively. Diversity of hemocytes of four populations from chickpea was wider than that from cotton. The differences in hemocytes of various populations may be due to space, time, host plant, insecticide use, other agroecological conditions, and insect genetic variability per se. The field populations of H. armigera heavily treated with insecticides appeared to contain more spherulocytes at the expense of plasmatocytes and granulocytes. The treatment of 6-day-old larvae of H. armigera with cypermethrin decreased plasmatocytes and granulocytes, and increased prohemocytes and spherulocytes in the hemolymph of last instar larvae. Thus, differential hemocyte counts may serve as an indicator of insecticide exposure and the diversity of insect populations. [ABSTRACT FROM AUTHOR]

Stem cell homeostasis requires coordinated fate decisions among stem cells that are often widely distributed within a tissue at varying distances from their stem cell niche. This requires a mechanism to ensure robust fate decisions within a population of stem cells. Here, we show that, in the Drosophila hematopoietic organ, the lymph gland (LG), gap junctions form a network that coordinates fate decisions between blood progenitors. Using live imaging of calcium signaling in intact LGs, we find that blood progenitors are connected through a signaling network. Blocking gap junction function disrupts this network, alters the pattern of encoded calcium signals, and leads to loss of progenitors and precocious blood cell differentiation. Ectopic and uniform activation of the calcium-signaling mediator CaMKII restores progenitor homeostasis when gap junctions are disrupted. Overall, these data show that gap junctions equilibrate cell signals between blood progenitors to coordinate fate decisions and maintain hematopoietic homeostasis. [Display omitted] • Drosophila blood progenitors use gap junctions to form a multicellular network • The gap-junction-mediated network helps blood progenitors coordinate fate decisions • Ca+2 signaling in blood progenitors is regulated by the gap junction-mediated network • Ca+2 signaling downstream of gap junctions regulates blood progenitor fate decisions Ho et al. show that, during Drosophila hematopoiesis, gap junctions link blood progenitors in a multicellular calcium-signaling network that ensures coordination of fate decisions. Gap junctions equilibrate calcium signaling between blood progenitors, which ensures collective cell behavior among hundreds of progenitors in the hematopoietic organ. [ABSTRACT FROM AUTHOR]

Stem cells are regulated by signals from their microenvironment, or niche. During Drosophila hematopoiesis, a niche regulates prohemocytes to control hemocyte production. Immune challenges activate cell-signalling to initiate the cellular and innate immune response. Specifically, certain immune challenges stimulate the niche to produce signals that induce prohemocyte differentiation. However, the mechanisms that promote prohemocyte differentiation subsequent to immune challenges are poorly understood. Here we show that bacterial infection induces the cellular immune response by modulating occluding-junctions at the hematopoietic niche. Occluding-junctions form a permeability barrier that regulates the accessibility of prohemocytes to niche derived signals. The immune response triggered by infection causes barrier breakdown, altering the prohemocyte microenvironment to induce immune cell production. Moreover, genetically induced barrier ablation provides protection against infection by activating the immune response. Our results reveal a novel role for occluding-junctions in regulating niche-hematopoietic progenitor signalling and link this mechanism to immune cell production following infection.

The efficient treatment of hematological malignancies as Acute Myeloid Leukemia, myelofibrosis and Chronic Myeloid Leukemia, requires the elimination of cancer-initiating cells and the prevention of disease relapse through targeting pathways that stimulate generation and maintenance of these cells. In mammals, inhibition of Smoothened, the key mediator of the Hedgehog signaling pathway, reduces Chronic Myeloid Leukemia progression and propagation. These findings make Smo a candidate target to inhibit maintenance of leukemia-initiating cells. In Drosophila melanogaster the same pathway maintains the hematopoietic precursor cells of the lymph gland, the hematopoietic organ that develops in the larva. Using Drosophila as an in vivo model, we investigated the mode of action of PF-04449913, a small-molecule inhibitor of the human Smo protein. Drosophila larvae fed with PF-04449913 showed traits of altered hematopoietic homeostasis. These include the development of melanotic nodules, increase of circulating hemocytes, the size increase of the lymph gland and accelerated differentiation of blood cells likely due to the exit of multi-potent precursors from quiescence. Importantly, the Smo inhibition can lead to the complete loss of hematopoietic precursors. We conclude that PF-04449913 inhibits Drosophila Smo blocking the Hh signaling pathway and causing the loss of hematopoietic precursor cells. Interestingly, this is the effect expected in patients treated with PF-04449913: number decrease of cancer initiating cells in the bone marrow to reduce the risk of leukemia relapse. Altogether our results indicate that Drosophila comprises a model system for the in vivo study of molecules that target evolutionary conserved pathways implicated in human hematological malignancies.