Chlorophyll content and plastid ultrastructure in leaflets ofMetasequoia glyptostroboides

The ability to synthetize chlorophyll pigments and to build the ultrastructures of the photosynthetic apparatus was studied in leaflets ofMetasequoia glyptostroboides, experimentally darkened before the buds started swelling. The content in chlorophyll pigments, was found to be about 50% that of normally lighted leaflets. Chloroplasts of leaflets of darkened buds show a photosynthetic apparatus with grana, formed by many thylakoids and by stroma lamellae and, in leaflet fragments fixed with glutaraldehyde and osmium tetraoxide, osmiophilic globules. Prolamellar bodies in direct connection with thylakoids are evident in these plastids. In plastids of leaflets of normally lighted buds prolamellar bodies are not present; starch grains, lacking in plastids of darkened buds, are present instead. These results, showing for the first time greening and building of a photosynthetic apparatus in leaflets of buds ofGymnospermae grown in darkness, are interpreted phylogenetically.     

Role of mitochondrial permeability transition pore and mitochondrial ATP-sensitive potassium channels in the protective effects of ischemic preconditioning in isolated hearts from fed and fasted rats

The aim of the present study was to assess whether the protective effects of ischemic preconditioning (PC) are associated with activation of the mitochondrial ATP-sensitive potassium channels (mitoKATP) and if there is any relationship between the activity of these channels and the mitochondrial permeability transition pore (MPTP) opening in ischemic-reperfused rat hearts under different nutritional conditions. Langendorff-perfused hearts of fed and 24-h fasted rats were exposed to 25 min of no-flow global ischemia plus 30 min of reperfusion. Fasting accelerated functional recovery and attenuated MPTP opening. The mitoKATP blocker, 5-hydroxydecanoic (HD), did not influence functional recovery and MPTP opening induced by ischemia–reperfusion in the fed hearts but partially reversed the beneficial effects of fasting. PC and the mitoKATP opener, diazoxide (DZ), improved functional recovery, preserved cell viability, and inhibited MPTP opening in both fed and fasted hearts. The protection elicited by PC and DZ on contractile recovery and MPTP opening was reversed by HD, which did not affect cell viability. Altogether, these results argue for a role of mitoKATP and its impact on preservation mitochondrial inner membrane permeability as a relevant factor in the improvement of contractile function in the ischemic-reperfused rat heart. They also suggest that the functional protection elicited by PC may be related to this mechanism.     

Amoeba-bacteria relationship: Factors in the bacterial lipids supporting the growth of axenicEntamoeba histolytica

Live bacteria in modifiedDiamond’s axenic medium did not support growth ofEntamoeba histolytica. Cysteine hydrochloride, required for the multiplication of amoeba, was broken down by live bacteria and toxic substances were produced which were lethal for amoebae. Monoxenic and xenic cultures ofaxenically grownE. histolytica could be established in Boeck and Drbohlav medium with bacteria and rice starch. Bacterial lipids prepared from 15 human intestinal bacteria supported growth and multiplication ofE. histolytica in axenic medium. In a pilot experiment using lipids ofStreptococcus faecalis, free fatty acids did stimulate the multiplication of amoebae. When total lipids of this bacteria were fractionated into neutral lipids and phospholipids by chromatography and used, neither fraction was found to stimulate growth. Free fatty acids prepared by chemical hydrolysis of the total lipids, neutral lipids and phospholipids stimulated growth ofE. histolytica, The sterols present in the bacterial lipids (neutral lipids or non-saponifiable fractions) stimulated growth of amoebae. It was found thatE. histolytica is incapable of liberating fatty acids from di- or triglyceridesof phospholipids and the multiplication of the organism is stimulated by the presence of free fatty acids and sterols (cholesterol).     

Identification of a pH 6.5 acetohydroxyacid synthetase inBacillus subtilis

Acetohydroxyacid synthetase activity of crude extracts ofBacillus subtilis grown in pH 7.0 minimal medium has a pH optimum of 7.5. However, the activity of extracts of cells grown in minimal medium of pH 6.0 shows a pH optimum of 6.5. Acetate or propionate induces formation of the pH 6.5 activity. Hydroxyapatite chromatography of a crude extract of cells grown in pH 7.0 medium shows one major and one minor peak of enzymatic activity. Both peaks have a pH optimum of 7.5–8.0. However, chromatography of an extract of cells grown in the presence of acetate reveals three peaks of activity: one major peak with a pH optimum of 6.5 and two minor peaks both having a pH optimum of 7.5–8.0.     

β-adrenergic receptor antagonists inhibit vasculogenesis of embryonic stem cells by downregulation of nitric oxide generation and interference with VEGF signalling

The β-adrenoceptor antagonist Propranolol has been successfully used to treat infantile hemangioma. However, its mechanism of action is so far unknown. The hypothesis of this research was that β-adrenoceptor antagonists may interfere with endothelial cell differentiation of stem cells. Specifically, the effects of the non-specific β-adrenergic receptor (β-adrenoceptor) antagonist Propranolol, the β₁-adrenoceptor-specific antagonist Atenolol and the β₂-adrenoceptor-specific antagonist ICI118,551 on vasculogenesis of mouse embryonic stem (ES) cells were investigated. All three β-blockers dose-dependently downregulated formation of capillary structures in ES cell-derived embryoid bodies and decreased the expression of the vascular cell markers CD31 and VE-cadherin. Furthermore, β-blockers downregulated the expression of fibroblast growth factor-2 (FGF-2), hypoxia inducible factor-1α (HIF-1α), vascular endothelial growth factor 165 (VEGF₁₆₅), VEGF receptor 2 (VEGF-R2) and phospho VEGF-R2, as well as neuropilin 1 (NRP1) and plexin-B1 which are essential modulators of embryonic angiogenesis with additional roles in vessel remodelling and arteriogenesis. Under conditions of β-adrenoceptor inhibition, the endogenous generation of nitric oxide (NO) as well as the phosphorylation of endothelial nitric oxide synthase (eNOS) was decreased in embryoid bodies, whereas an increase in NO generation was observed with the NO donor S-nitroso-N-acetyl-D,L-penicillamine (SNAP). Consequently, vasculogenesis of ES cells was restored upon treatment of differentiating ES cells with β-adrenoceptor antagonists in the presence of NO donor. In summary, our data suggest that β-blockers impair vasculogenesis of ES cells by interfering with NO generation which could be the explanation for their anti-angiogenic effects in infantile hemangioma.     

Preliminary studies of the effects of an induced phosphate deficiency on carbohydrate-nitrogen ratios inAlternanthera philoxeroides [Centrospermae: Amaranthacea] and on the feeding ofAgasicles hygrophila [Col.: Chrysomelidae]

In no-choice tests but not in choice tests, alligatorweed flea beetles,Agasicles hygrophila Selman & Vogt (Col.: Chrysomelidae) exposed to alligatorweed plants grown with two levels of mineral nutrition fed significantly more on those grown in full mineral nutrient than those grown with deficient phosphate. Chemical analysis showed that the full nutrient plants had more ethanol-soluble nitrogen compounds but less total carbohydrate than the phosphate-deficient plants. The response of beetles to phosphate-deficient alligatorweed may thus result from a change in the carbohydrate-nitrogen composition of host plants, though further investigation is needed for confirmation. Flea beetle response was identical to terminal and mature leaf tissue of full nutrient plants.     

Carvedilol Attenuates 6-Hydroxydopamine-Induced Cell Death in PC12 Cells: Involvement of Akt and Nrf2/ARE Pathways

Oxidative stress is closely related to the pathogenesis of neurodegenerative disorders such as Parkinson’s disease. Carvedilol, a nonselective β-adrenergic receptor blocker with pleiotropic activity has been shown to exert neuroprotective effect due to its antioxidant property. However, the neuroprotective mechanism of carvedilol is still not fully uncovered. The phosphotidylinositol 3-kinase (PI3K)/Akt signaling pathway plays key role in cell survival and the nuclear factor erythroid 2–related factor 2 (Nrf2)/antioxidant response element (ARE) signaling pathway is the major cellular defense mechanism against oxidative stress. Here we investigated the effects of carvedilol on 6-hydroxydopamine (6-OHDA)-induced cell death as well as the Akt and Nrf2/ARE pathways in PC12 cells. We found that carvedilol significantly increased cell viability and decreased reactive oxygen species in PC12 cells exposed to 6-OHDA. Furthermore, carvedilol activated the Akt and Nrf2/ARE pathways in a concentration-dependent manner, and increased the protein levels of heme oxygenase-1(HO-1) and NAD(P)H quinone oxidoreductase-1(NQO-1), two downstream factors of the Nrf2/ARE pathway. In summary, our results indicate that carvedilol protects PC12 cells against 6-OHDA-induced neurotoxicity possibly through activating the Akt and Nrf2/ARE signaling pathways.     

Involvement of Neurotransmitters in the Action of the Nociceptin/Orphanin FQ Peptide-Receptor System on Passive Avoidance Learning in Rats

The nociceptin/orphanin FQ peptide (NOP) receptor and its endogenous ligand plays role in several physiologic functions of the central nervous system, including pain, locomotion, anxiety and depression, reward and drug addiction, learning and memory. Previous studies demonstrated that the NOP-receptor system induces impairment in memory and learning. However, we have little evidence about the underlying neuromodulation. The aim of the present study was to investigate the involvement of distinct neurotransmitters in the action of the selective NOP receptor agonist orphan G protein-coupled receptor (GPCR) SP9155 P550 on memory consolidation in a passive avoidance learning test in rats. Accordingly, rats were pretreated with a nonselective muscarinic acetylcholine receptor antagonist, atropine, a γ-aminobutyric acid subunit A (GABA-A) receptor antagonist, bicuculline, a D2, D3, D4 dopamine receptor antagonist, haloperidol, a nonselective opioid receptor antagonist, naloxone, a non-specific nitric oxide synthase inhibitor, nitro-l-arginine, a nonselective α-adrenergic receptor antagonist, phenoxybenzamine and a β-adrenergic receptor antagonist, propranolol. Atropine, bicuculline, naloxone and phenoxybenzamine reversed the orphan GPCR SP9155 P550-induced memory impairment, whereas propranolol, haloperidol and nitro-l-arginine were ineffective. Our results suggest that the NOP system-induced impairment of memory consolidation is mediated through muscarinic cholinergic, GABA-A-ergic, opioid and α-adrenergic receptors, whereas β-adrenergic, D2, D3, D4-dopaminergic and nitrergic mechanisms are not be implicated.     

Glutamine synthetase,glutamate synthase and glutamate dehydrogenase in Rhizobium japonicum strains grown in cultures and in bacteroids from root nodules of Glycine max

The growth yields of three strains of Rhizobium japonicum (CB 1809, CC 723, CC 705) in culture solutions containing L-glutamate were about twice those grown with ammonium. The activities of glutamine synthetase (GS; EC 6.3.1.2) and glutamate dehydrogenase (GDH; EC 1.4.1.4) were dependent on the nitrogen source in the medium and also varied with growth. Both NADPH-and NADH-dependent glutamate synthase (GOGAT; EC 1.4.1.13) and NADPH-dependent GDH were found in strains grown with either glutamate or ammonium but NADH-linked GDH was only detected in glutamate-grown cells. Glutamine synthetase was adenylylated in cells grown with NH ₄ ⁺ (90%) and to lesser extent in those grown with L-glutamate (50%). In root nodules produced by the three strains in Glycine max (L.) Merr., the bulk of GS was located in the nodule cytosol (60–85%). The enzyme was adenylylated in bacteroids (43–75%) and in the nodule tissues (52–68%). The enzyme in cell-free extracts of Rh. japonicum (CC 705) grown in culture solutions containing glutamate and in bacteroids (CC 705) was deadenylylated by snake-venom phosphodiesterase. L-methionine-DL-sulfoximine restricted the incoporation of ¹⁵N-labelled (NH₄)₂SO₄ into cells of strains CB 1809 and CC 705, as well as in bacteroids of strain CC 705. It is noteworthy that appreciable activities for GDH were found in the free-living rhizobia grown on glutamate. Thus the presence of an enzyme does not necessarily imply that a particular pathway is operative in assimilating ammonium into cell nitrogen. Based on ¹⁵N studies, the GS-GOGAT pathway of rhizobia (strains CB 1809 and CC 705) is important when grown in culture solutions as well as in bacteroids from root nodules of G. max.     

Oxaloacetate decarboxylase from Acetobacter aceti

An oxaloacetate (OAA) decarboxylase (EC 4.1.1.3) has been purified 72-fold from Acetobacter aceti cells grown on ethanol, and its molecular weight was estimated to be about 80,000 by gel filtration. Several properties distinguished this enzyme from the OAA decarboxylase from A. xylinum:

1. It was not a constitutive enzyme; the activity was 6- to 20-fold higher in cells grown on a C₂ substrate (acetate or ethanol) than in cells grown on a C₃ compound (pyruvate or propionate).
2. The optimum pH was 7.5; a value of 5.6 was reported for the enzyme from A. xylinum.
3. The enzyme did not need a divalent cation and was not inhibited by EDTA.
4. The K _mvalue for OAA was found to be 0.22 mM. It was not affected by the addition of nicotinamide adenine dinucleotide.
5. The enzyme activity was neither inhibited by acetate nor by L-malate.

In addition, the OAA decarboxylase from A. aceti was insensitive to monovalent cations, avidin or acetyl coenzyme A.     

Ubiquinone 10 formation in Rhodospirillum rubrum under different culture conditions

The formation of ubiquinone 10 and bacteriochlorophyll (bchl) was determined in Rhodospirillum rubrum grown under different culture conditions. Transfer of chemotrophically grown cultures to photosynthetic conditions leads to the formation of the pigments until cells reach the stationary phase of growth. Bchl-synthesis initially exceeds quinone synthesis. On a cellular protein basis quinone levels first decrease by about a factor of two and subsequently increase by a factor of four. Bchl levels per protein increase until cells reach the stationary phase of growth. Quinone levels per bchl decrease rather rapidly and become constant in the growing culture. When cells were transferred under continuous phototrophic conditions to new culture medium, both pigments are formed concomitantly. While protein synthesis starts immediately, bchl and ubiquinone formation is slightly delayed. This causes a short time decrease in the amount of both pigments per cellular protein followed by an increase to a constant level. Ratios of ubiquinone per bchl are constant. The transfer of phototrophically grown cultures to chemotrophic conditions results in a complete inhibition of bchl formation while quinone synthesis resumes. Quinone cellular levels decrease slightly and then remain constant. Quinone values increase per bchl which is eventually diluted out of the cells.     

Light-controlled sugar-starch interconversion in epidermal chloroplasts of light-grown cucumber hypocotyl sections and its relationship to cell elongation

Sugar-starch interconversion in epidermal chloroplasts of light-grown cucumber hypocotyl sections as a regulatory mechanism of the osmotic potential of the cell was studied in relation to cell elongation. The presence of chloroplasts in epidermal cells was confirmed by electron microscopy, and also the chloroplasts were shown to act as the site of sucrose-starch interconversion. Chloroplast starch formation was induced by light, which was more distinct in the presence of sucrose (50 mM). The starch formation was microscopically detectable even at 1 hr incubation in the light with sucrose. On the other hand, no starch formation was observed in the dark both in the presence and absence of sucrose. Red light was effective, but not blue light. A photosynthetic inhibitor, 3-(4-chlorophenyl)-1:1-dimethylurea, also inhibited starch formation. Thus, epidermal chloroplast starch formation was induced under conditions where cell elongation is small and the osmotic potential (Ψ ₀) of the epidermal cell is high. The sugar quantity (free sugar and reducing sugar) as the osmotica of the cell was larger in the dark than in the light, whereas the quantity of starch was greater in the light than in the dark. It is assumed from these results that one of the regulatory mechanisms of the osmotic potential of the epidermal cells in sugar-starch interconversion which occurs in epidermal chloroplasts.     

Effects of cordycepin,hydroxyurea and cycloheximide on histone mRNA synthesis in synchronized HeLa cells

The effects of cordycepin, hydroxyurea and cycloheximide on the synthesis of histone mRNA in synchronized HeLa cells were studied by quantitating the RNA, using translation in a rabbit reticulocyte cell-free system. It was found that biologically active histone mRNA is synthesized in the presence of cordycepin. This result strengthens the findings by others that histone mRNA does not contain poly(A). Hydroxyurea and cycloheximide, when used at concentrations that inhibit cellular DNA synthesis, had different effects on histone messenger activity. While polyribosomal messenger activity rapidly declined after addition of hydroxyurea it was not impaired by cycloheximide. These results might help to elucidate regulatory mechanisms involved in the coupled synthesis of DNA and histones in HeLa cells.     

The Effects of Hispidulin on Bupivacaine-Induced Neurotoxicity: Role of AMPK Signaling Pathway

Bupivacaine is a sodium channel blocker, which is widely used for local infiltration nerve block, epidural and intrathecal anesthesia. However, bupivacaine could cause nerve damage. Hispidulin was shown to be able to penetrate the blood–brain barrier and possess antiepileptic activity. In this study, we investigate whether hispidulin administration could attenuate bupivacaine-induced neurotoxicity. Bupivacaine-challenged mouse neuroblastoma N2a cells were treated with hispidulin. The neuron injury was assessed by examination of cell viability and apoptosis. The levels of activation of AMP-activated protein kinase (AMPK) signaling pathway were examined along with the effect of blocking AMPK signaling on cell viability in the presence of hispidulin and bupivacaine. Our results showed that Bupivacaine treatment significantly decreased cell viability and induced apoptosis. Treatment with hispidulin significantly attenuated bupivacaine-induced cell injury. In addition, hispidulin treatment increased the levels of phospho-AMPK and phospho-GSK3β and attenuated bupivacaine-induced loss in mitochondrial membrane potential. Furthermore, we found that blocking AMPK signaling pathway significantly abolished the cytoprotective effect of hispidulin against bupivacaine-induced cell injury. Our findings suggest that treatment of neuroblastoma cells with hispidulin-protected neural cells from Bupivacaine-induced injury via the activation of the AMPK/GSK3β signaling pathway.     

Rhythmic changes in ribonuclease activity in relation to nucleic acid synthesis in cotyledons ofChenopodium rubrum L. and to floral induction of the plants

Ribonuclease (RNAse) activity was investigated in cotyledons ofChenopodium rubrum plants subjected to various conditions of illumination (photoperiodic induction, continuous light, induction cancelled by interrupting the dark period by a light-break). At the end of the dark period of the single inductive cycles RNAse activity of induced plants was inferior to that of plants grown in continuous light. At the end of the first two cycles the activity was lowest after the interruption of the dark period by light. The investigation of the enzyme in 6h intervals showed rhythmic changes in activity to occur in induced plants. Enzyme activity followed a pattern opposed to this of nucleic acid (NA) synthesis in the cotyledons. In plants from continuous light the enzyme activity did not show any rhythm and in plants having obtained a light-break during the inductive period the rhythm was less distinct than in the induced ones. The period length of the endogenous rhythm of NA synthesis in the cotyledons is about half as long as this of flowering and the peaks of flowering coincide with the throughs of NA synthesis.     

Glyoxylate conversion by Hyphomicrobium species grown on allantoin as nitrogen source

Glyoxylate, formed as a result of allantoin degradation, is converted by Hyphomicrobium species to glycerate via tartronate semialdehyde. Glyoxylate carboligase and tartronate semialdehyde reductase, the two enzymes involved, are present only in cells grown on allantoin as nitrogen source.     

Distribution of mercury,cadmium, lead and thallium in a eutrophic lake

Five species of fishes, two species of aquatic macrophytes, zooplankton, migratory goose feces, water and sediments from a eutrophic lake were analyzed for mercury, cadmium, lead and thallium. Mercury was detected in fishes and sediments only while cadmium and lead were detected in all components. Thallium was detected only in sediments. Sediments in the lake act as a ‘sink’ for the four metals. Mercury in axial musculature of largemouth bass was highly correlated with length and weight. A high degree of correlation between other metals and weight and length of other species was not evident. The feces of migratory waterfowl had high concentrations of both cadmium and lead. In view of the large quantity of waterfowl feces deposited within the drainage basin, it is suggested that this avenue is one of the major sources of contamination for the two metals and that fallout from airborne particulate matter is secondary. Fallout of airborne particulate matter may be the primary method by which mercury and thallium enter the lake although residual concentrations of the four metals in soil of the drainage basin were not determined.     

Changes in mitochondrial density and succinic dehydrogenase activity in Euglena gracilis as a function of the dependency on light for growth

Mitochondria from Euglena gracilis strain z grown under strictly heterotrophic conditions have higher equilibrium densities and higher succinate dehydrogenase activities than those grown in the presence of light. There is a consistent trend toward lower mitochondrial density with increasing time of exposure to light. Experiments reported here indicate that the development of dependency upon light for the provision of energy results in the repression of mitochondrial development with respect to both density and enzymatic activity.