Restricted diet breadth of the larvae of Antheraea assamensis and the role of the labrum‐epipharynx and galeal sensilla

The silkworm, Antheraea assamensis Helfer (Lepidoptera: Saturniidae), grows primarily on Persea bombycina and Litsea polyantha. To understand if the restricted diet breadth is due to the specific role of gustatory sensilla of the larvae of A. assamensis, the same fifth instar larvae retaining only labrum‐epipharynx or galeal sensilla were subjected to food choice tests. The foods used were leaves of two host‐plant and two non‐host‐plant species. Mean per cent consumption and per cent of choosing larvae were used as parameters for drawing conclusions. The finding indicated involvement of the labrum‐epipharynx for acceptance and galeal sensilla for rejection of a non‐host‐plant species. Scanning electron microscope studies revealed the presence of two sensilla on the galea, one lateral and one medial sensilla styloconicum and two gustatory sensilla in the epipharynx of A. assamensis. The study revealed the key role of galeal sensilla in the restrictive diet‐breadth of A. assamensis.     

Thermal inactivation and stabilization of lysozyme substrate-- Micrococcus lysodeicticus cells

Heat inactivation of the acetonic powder of Micrococcus lysodeicticus cells suspended in phosphate buffer pH 6.2 was quantitatively characterized in the temperature range from 34 to 52 degrees. The total value of the rate constant for heat inactivation of the cells equals 2.88 X 10(8) exp(-18360/RT) sec-1. The activation parameters of the process at 34 degrees are the following: delta H* = 17.7 kcal/mole; delta S* = 21.8 E. U.; delta F* = 24.4 kcal/mole. The effect of ethylene glycol, mannitol, dextran, polyvinyl alcohol (PVA) and polyethylene glycols with different molecular weights on the lysis rate and cell stability was studied. Polyvinyl alcohol was found to be the most effective stabilizer. At concentrations of about 10(-5) it enhances the thermostability of the cells threefold.     

Lipogenesis in the brain of suckling rats. Studies on the mechanism of mitochondrial–cytosolic carbon transfer

1. Studies on the incorporation of [3-¹⁴C]pyruvate and d-3-hydroxy[3-¹⁴C]butyrate into the brain lipid fraction by brain homogenates of the suckling (7-day-old) rat have been carried out. 2. Whereas approximately twice as much CO₂ was evolved from pyruvate compared with 3-hydroxybutyrate metabolism, similar amounts of the radioactivity of these two precursors were incorporated into the lipid fraction. Furthermore, in both cases the incorporation into lipid was almost tripled when glucose (10mm) or NADPH (2.5mm) was added to the incubation media. 3. If 5mm-(—)-hydroxycitrate, an ATP–citrate lyase inhibitor, was added to the incubation the incorporation of carbon from pyruvate was inhibited to 39% of the control and from 3-hydroxybutyrate to 73% of the control, whereas CO₂ production from both precursors was not affected. 4. The incorporation from pyruvate or 3-hydroxybutyrate into lipids was not affected by the presence of 10mm-glutamate in the medium (to encourage N-acetylaspartate production). However, incorporation from pyruvate was inhibited by 21% in the presence of 5mm-amino-oxyacetate (a transaminase inhibitor) and by 83% in the presence of both hydroxycitrate (5mm) and amino-oxyacetate. 5. Incorporation from 3-hydroxybutyrate into brain lipids was inhibited by 20% by amino-oxyacetate alone, but by 55% in the presence of both hydroxycitrate and amino-oxyacetate. 6. It is concluded that the mechanism of carbon transfer from pyruvate into lipids across the mitochondrial membrane in the suckling rat brain is mainly via citrate and N-acetylaspartate. 3-Hydroxybutyrate, in addition to using these routes, may also be incorporated via acetoacetate formation and transport to the cytosol.     

The effect of acetate on the regulation of the branched chain α-keto acid and the pyruvate dehydrogenase complexes in the perfused rat liver

The regulatory consequences of acetate infusion on the pyruvate and the branched chain α-keto acid dehydrogenase reactions in the isolated, perfused rat liver were investigated. Metabolic flux through these two decarboxylation reactions was monitored by measuring the rate of ¹⁴CO₂ production from infused 1-¹⁴C-labeled substrates. When acetate was presented to the liver as the sole substrate the rate of ketogenesis which resulted was maximal at concentrations of acetate in excess of 10 mm. The increase in hepatic ketogenesis during acetate infusion was not accompanied by an alteration of the mitochondrial oxidation-reduction state as measured by the ratio of β-hydroxybutyrate/ acetoacetate in the effluent perfusate. While acetate infusion did not affect the rate of α-keto[1-¹⁴C]isocaproate decarboxylation, the rate of α-keto[1-¹⁴C]isovalerate decarboxylation was stimulated appreciably upon acetate addition. No change was observed in the amount of extractable branched chain α-keto acid dehydrogenase during acetate infusion. The rate of [1-¹⁴C]pyruvate decarboxylation was stimulated in the presence of acetate at low (<1 mm) but not at high (>1 mm) perfusate pyruvate concentrations. The stimulation of the metabolic flux through the pyruvate dehydrogenase reaction upon acetate infusion was accompanied by an increase in the activation state of the pyruvate dehydrogenase complex from 25.7 to 35.6% in the active form. In a liver perfused in the presence of the pyruvate dehydrogenase kinase inhibitor, dichloroacetate, at a low concentration of pyruvate (0.05 mm) the infusion of acetate did not affect the rate of pyruvate decarboxylation. As the rate of mitochondrial acetoacetate efflux is increased during acetate infusion the stimulation of pyruvate and α-ketoisovalerate decarboxylation is attributed to an accelerated rate of exchange of mitochondrial acetoacetate for cytosolic pyruvate or α-ketoisovalerate on the monocarboxylate transporter.     

Cytotoxicity of zinc chloride in mice in vivo

Intraperitoneal administration of zinc chloride (ZnCl2) to Swiss albino mice in vivo induced a significant (p less than or equal to 0.05) increase in the frequencies of chromosomal aberrations of the bone-marrow cells at all concentrations used following acute (7.5, 10, 15 mg/kg body weight) and chronic (2.0, 3.0 mg/kg body wt) treatment. The degree of clastogenicity was directly proportional to the concentrations (p less than or equal to 0.05, trend test) and indirectly to the period of treatment (p less than or equal to 0.05, ANOVA test). It induced a dose-dependent, statistically significant increase (Mann-Whitney U statistics, Student's t-test) in sperm-head abnormalities. The data designate ZnCl2 as a potent clastogen and as a toxic chemical at the concentrations used.     

Signaling different pathways of cell death: Abrin induced programmed necrosis in U266B1 cells

Abrin is a type II ribosome-inactivating protein comprising of two subunits, A and B. Of the two, the A-subunit harbours the RNA-N-glycosidase activity and the B subunit is a galactose specific lectin that enables the entry of the protein inside the cell. Abrin inhibits protein synthesis and has been reported to induce apoptosis in several cell types. Based on these observations abrin is considered to have potential for the construction of immunotoxin in cell targeted therapy. Preliminary data from our laboratory however showed that although abrin inhibited the protein synthesis in all cell types, the mode of cell death varied. The aim of the present study was therefore to understand different death pathways induced by abrin in different cells. We used the human B cell line, U266B1 and compared it with the earlier studied T cell line Jurkat, for abrin-mediated inhibition of protein translation as well as cell death. While abrin triggered programmed apoptosis in Jurkat cells in a caspase-dependent manner, it induced programmed necrosis in U266B1 cells in a caspase-independent manner, even when there was reactive oxygen species production and loss of mitochondrial membrane potential. The data revealed that abrin-mediated necrosis involves lysosomal membrane permeabilization and release of cathepsins from the lysosomes. Importantly, the choice of abrin-mediated death pathway in the cells appears to depend on which of the two events occurs first: lysosomal membrane permeabilization or loss of mitochondrial membrane potential that decides cell death by necrosis or apoptosis.     

Patterns of CO<Subscript>2</Subscript> exchange and productivity of the herbaceous vegetation and trees in a humid savanna in western Kenya

Factors governing the dynamics between woody and herbaceous vegetation in the savanna are of ecological interest since they determine ecosystem productivity and stability. Field measurements were conducted in a humid savanna in the Lambwe valley, western Kenya, to compare CO2 exchange of the herbaceous vegetation and trees and its regulation. Soil characteristics and root distribution patterns under tree canopies and in the open locations dominated by the herbaceous vegetation were profiled in 1-m-deep soil layers. Soil water content (SWC) was measured at 30 cm depth both in the herbaceous vegetation and also under the tree canopies. The mean maximum monthly gross primary production (GPPmax) in the herbaceous vegetation was determined from chamber measurements, while daily GPP (GPPday) in both the grass and tree canopies was simulated using the PIXGRO model. The highest mean GPPmax in the herbaceous vegetation was 26.2 ± 3.7 μmol m-2 s-1 during April. Seasonal fluctuations of GPP in the herbaceous vegetation were explained by soil water availability (R ² = 0.78) within the upper 30-cm soil profile. Seasonal GPPday fluctuations were larger (between 1 gC m-2 d-1 and 10 gC m-2 d-1) in the herbaceous vegetation compared to the trees, which fluctuated around 4.3 ± 0.3 gC m-2 d-1 throughout most of the measurement period. Daily tree canopy transpiration (Ec), canopy conductance (Gc), and GPPday were decoupled from SWC in the top 30-cm soil profile. On average, ecosystem GPPday (mean of tree and herbaceous vegetation) was 14.3 ± 1.2 gC m-2 d-1 during the wet period and 6.1 ± 0.9 gC m-2 d-1 during drought. Differences between the herbaceous and tree canopy responses were attributed to soil moisture availability.     

Bioprospecting Micromonospora from Kaziranga National Park of India and their anti-infective potential

Large number of strains was isolated from soils of Kaziranga National Park of North-East India using selective isolation procedure. They were assigned to the genus Micromonospora on the basis of their typical colonial and pigmentation features. The taxonomic identities of the isolates were confirmed on the basis of their molecular characters (16SrDNA). A total of one hundred Micromonospora strains were isolated during the present investigation. The diagnostic cell wall sugar and amino acids were determined from these Micromonospora strains. After preliminary screening most of the isolates exhibited excellent anti-infective activity against human bacterial pathogens Staphylococcus aureas, Bacillus subtilis, Proteus vulgaris, Echerichia coli, Pseudomonas aeroginosa and fungal pathogens Aspergillus niger, Fusarium oxysporum and Candida albicans. Among these isolates one strain designated as HK-10 showed promising activity against human pathogens S. aureas, B. subtilis, P. vulgaris and P. aeroginosa.     

Toll-like receptor (TLR) 2-9 agonists-induced cytokines and chemokines: I. Comparison with T cell receptor-induced responses

The cells of innate and adaptive immunity, although activated by different ligands, engage in cross talk to ensure a successful immune outcome. To better understand this interaction, we examined the demographic picture of individual TLR (TLRs 2-9) -driven profiles of eleven cytokines (IFN-alpha/beta, IFN-gamma, IL-12p40/IL-12p70, IL-4, 1L-13, TNF-alpha, IL-1beta, IL-2, IL-10) and four chemokines (MCP-1, MIP1beta, IL-8, and RANTES), and compared them with direct T-cell receptor triggered responses in an assay platform using human PBMCs. We find that T-cell activation by a combination of anti-CD3/anti-CD28/PHA induced a dominant IL-2, IL-13, and Type-II interferon (IFN-gamma) response without major IL-12 and little Type-I interferon (IFN-alphabeta) release. In contrast, TLR7 and TLR9 agonists induced high levels of Type-I interferons. The highest IFN-gamma levels were displayed by TLR8 and TLR7/8 agonists, which also induced the highest levels of pro-inflammatory cytokines IL-12, TNF-alpha, and IL-1beta. Amongst endosomal TLRs, TLR7 displayed a unique profile producing weak IL-12, IFN-gamma, TNF-alpha, IL-1beta, and IL-8. TLR7 and TLR9 resembled each other in their cytokine profile but differed in MIP-1beta and MCP1 chemokine profiles. Gram positive (TLR2, TLR2/6) and gram negative (TLR4) pathogen-derived TLR agonists displayed significant similarities in profile, but not in potency. TLR5 and TLR2/6 agonists paralleled TLR2 and TLR4 in generating pro-inflammatory chemokines MCP-1, MIP-1beta, RANTES, and IL-8 but yielded weak TNF-alpha and IL-1 responses. Taken together, the data show that diverse TLR agonists, despite their operation through common pathways induce distinct cytokine/chemokine profiles that in turn have little or no overlap with TCR-mediated response.     

Complement activation via alternative pathway is critical in the development of laser-induced choroidal neovascularization: role of factor B and factor H

The objective of this study was to explore the role of classical, lectin, and alternative pathways of complement activation in laser-induced choroidal neovascularization (CNV). The classical and alternative pathways were blocked in C57BL/6 mice by small interfering RNAs (siRNA) directed against C1q and factor B, respectively. C4(-/-) mice developed CNV similar to their wild-type controls and inhibition of C1q by siRNA had no effect on the development of CNV. In contrast, CNV was significantly inhibited (p < 0.001) in C5(-/-) mice and C57BL/6 mice treated with factor B siRNA. Inhibition of the alternative pathway by factor B siRNA resulted in decreased levels of membrane attack complex and angiogenic factors-vascular endothelial growth factor and TGF-beta2. Furthermore, factor B was up-regulated in complement sufficient C57BL/6 mice at day 1 postlaser and remained elevated at day 7. Significantly reduced levels of factor H were observed at day 3 in these animals. In conclusion, our results demonstrate that activation of the factor B-dependent alternative pathway, but not the classical or lectin pathways, was essential for the development of CNV in mouse model of laser-induced CNV. Thus, specific blockade of the alternative pathway may represent a therapeutically relevant strategy for the inhibition of CNV.