Photosynthetic electron transfer system is inoperative in anaerobic cells of Erythrobacter species strain OCh 114

Some of the photosynthetic reactions were measured under aerobic and anaerobic conditions in intact cells of an aerobic photosynthetic bacterium Erythrobacter species strain OCh 114 (ATCC No. 33942). In intact cells, the flash-light induced oxidation of cytochrome c-551, the continuous light-induced oxidation of reaction center bacteriochlorophyll and the continuous light-induced pH change ( ) of the suspension decreased on aerobic-anaerobic transition and almost disappeared under anaerobic conditions. These photosynthetic reactions reappeared when the suspension was aerated again. These phenomena were reconciled with the fact that Erythrobacter sp. cannot grow anaerobically even in the light. The incompetence of photoanaerobic growth of this bacterium was explained by the reduction of the primary electron acceptor (Q_I) before illumination, resulting partly from the relatively high midpoint potential of Q_I of this bacterium.Abbreviations Q_I Primary electron acceptor - E_h ambient redox potential - E_m midpoint redox potential     

Purification and some properties of a soluble cytochrome (cytochrome c-551) from Erythrobacter species strain OCh 114

A soluble cytochrome, cytochrome c-551 was purified from an aerobic photosynthetic bacterium Erythrobacter species strain OCh 114 (ATCC No. 33942) by ammonium sulfate fractionation, ion-exchange chromatography and gel-filtration. The cytochrome had absorption maxima at 277, 410, and 524–525 nm in the oxidized form, and at 415, 522, and 550.5 nm in the reduced form. At 77 K, the -band of the absorption spectrum of the reduced form split in two at 547 and 549 nm. The millimolar absorption coefficient at 550.5 nm was 26.8 mM^-1 cm^-1 in the reduced form. This cytochrome was an acidic protein with an isoelectric point of 4.9. Its molecular weight was determined to be 15,000 by gel-filtration on Sephadex G-100 and 14,500 by sodium dodecyl sulfate polyacrylamide gel electrophoresis. The midpoint potential of this cytochrome was +250 mV at pH 7.0. This cytochrome did not bind CO.     

Discovery of novel 1,2,3,4-tetrahydroisoquinolines and 3,4-dihydroisoquinoline-1(2H)-ones as potent and selective inhibitors of KDR: synthesis, SAR, and pharmacokinetic properties

1,2,3,4-Tetrahydroisoquinolines and 3,4-dihydroisoquinoline-1(2H)-ones were identified as potent and selective inhibitors of KDR. The discovery, synthesis, and structure–activity relationships of these novel inhibitors are reported. In vitro metabolism and pharmacokinetic profiles of the most interesting compounds are discussed.     

Lipid extracts from different algal species:1H and13C-NMR spectroscopic studies as a new tool to screen differences in the composition of fatty acids,sterols and carotenoids

One- and two-dimensional¹H- and¹³C-NMR spectra of lipid extracts fromUlva rigida, Gracilaria longa, Fucus virsoides andCodium tomentosum collected in the northern Adriatic Sea allowed screening of the content of fatty acid chains, carotenoids, free and acylated cholesterol and chlorophylls. The carotenoid-to-polyunsaturated fatty acid molar ratio was taken as a comparison parameter in samples ofUlva rigida collected in differentloci and seasons; the value was markedly higher in samples from the Lagoon of Venice than from marine coastal waters. The total cholesterol concentration was evaluated by¹H-NMR spectroscopy and similar values were found for all species. Two-dimensional heterocorrelated NMR spectroscopy was shown to give characteristic fingerprints of the lipid extracts from algal samples as regards the content in chlorophylls, unsaturated fatty acids and carotenoids.author for correspondence     

Ontogeny of the antennal glands in the crayfish Astacus leptodactylus (Crustacea, Decapoda): immunolocalization of Na+,K+-ATPase

The involvement of the antennal urinary glands in the ontogeny of osmoregulatory functions was investigated during the development of Astacus leptodactylus by measurements of hemolymph and urine osmolality in juvenile and adult crayfish and by the immunodetection of the enzyme Na⁺,K⁺-ATPase. In stage II juveniles, 1-year-old juveniles, and adults, all of which were maintained in freshwater, urine was significantly hypotonic to hemolymph. In adults, chloride and sodium concentrations were much lower in urine than in hemolymph. During embryonic development, Na⁺,K⁺-ATPase was detected by immunocytochemistry in ionocytes lining the tubule and the bladder, at an eye index (EI) of 220–250 m, and in the labyrinth, at EI 350 m. In all regions, immunofluorescence was mainly located at the basolateral side of the cells. No immunofluorescence was detected at any stage in the coelomosac. In late embryonic stages (EI 410–440 m), in stage I juveniles, and in adults, strong positive immunofluorescence was found from the labyrinth up to and including the bladder. These results show that, as early as hatching, juvenile crayfish are able to produce dilute urine hypotonic to hemolymph. This ability originates from the presence of Na⁺,K⁺-ATPase in ion-transporting cells located in the labyrinth, the tubule, and the bladder of the antennal glands and constitutes one of the main adaptations of crayfish to freshwater.We thank the University of Tarbiat Modarres and Ministry of Science, Research and Technology, Islamic Republic of Iran for financial aid and support. Special thanks are also due to the Société Française dExportation des Ressources Educatives (SFERE) for the scholarship to S.K.     

Cell-killing efficiency and number of platinum atoms binding to DNA,RNA, and protein molecules of hela cells treated with combinations of hyperthermia and cisdiamine (glycolato)platinum(II)

HeLa S-3 cells were treated with^195mPt-radiolabeledcisdiamine(glylato)platinum(II) (254-S) for 60 min at various temperatures, and the relationship between the lethal effect and the number of Pt atoms binding to DNA, RNA, and proteins was examined. The mean lethal concentration (Do) of 254-S for a 60-min treatment at 0‡C, 25‡C, 37‡C, 40‡C, 42‡C, and 44‡C was 233,132, 61.1, 42.7, 25.6, and 9.9 ΜM, respectively. By using identically treated cells, the numbers of Pt atoms combined with DNA, RNA, and protein molecules were determined in the subcellular fractions. Thus, the D₀ values given as drug concentrations were replaced with the number of Pt atoms combined in each fraction. Then, the cell-killing efficiency of the Pt atom was expressed as the reciprocal of the number of Pt atoms combined and was calculated for each molecule. The efficiency for the DNA molecule was 0.61X10⁴, 1.09xl0⁴, 1.88xl0⁴, 1.90xl0⁴, 2.66xl0⁴, and 5.88xl0⁴ nucleotides, respectively, for the conditions described. From 0‡C to 44‡C, the cell-killing efficiency of Pt atoms increased by a factor of 9.6.     

Tissue kinetics,ion transport,and recruitment of mitochondria-rich cells in the skin of the toad (Bufo bufo) in response to exposure to distilled water

Mitochondria-rich cells (MRC) of the amphibian epidermis are responsible for active chloride uptake at low external salinity, and new MRCs are recruited in response to exposure to distilled (deionized) water. The time-course of this recruitment, the tissue kinetics and ion transport have been studied in toads (Bufo bufo) immediately before, and after 2,7, and 14 days exposure to distilled water. General epidermal structure was not affected. However, the numbers of MRCs per mm² (D_MRC) increased throughout the experiment as revealed by staining of epidermal sheets with AgNO₃ (Ag) or methylene blue (MB). Part of the increased D_MRC was accounted for by an increase in MRC subpopulation(s) that stained neither with Ag nor MB. The cell birth rate (K_b) decreased and cell loss by moulting (K_d) increased without any significant change in epidermal cell pool size, indicating a reduced apoptotic rate. The increase in D_MRC was accompanied by a 3-fold increase in Cl^- current (I_Cl). At day-2 there was a transient reduction in the I_Cl per MRC. H⁺ secretion was progressively reduced during prolonged exposure to distilled water. Thus, at day-2 MRCs appeared incompletely differentiated as indicated by decreased I_Cl and H⁺ flux per MRC, and by the increased proportion of MRCs unstained by Ag or MB. Full Cl^- (but not H⁺) transport capacity, was restored at day-7. We conclude that increased D_MRC following exposure to low external Cl^-, rather than being due to an increased K_b, is the combined effect of a decreased apoptotic rate and an increased rate of differentiation, where morphological differentiation precedes functional differentiation.Parts of this study have been presented at the 32th International Congress of Physiological Sciences, 1–6 August, 1993, Glasgow, Scotland, and the 19th meeting of the European Study Group for Cell Proliferation, 5–9 October, 1993, Bruges, Belgium     

Correlating structure, dynamics, and function in transmembrane segment VII of the Na/H exchanger isoform 1

We place ¹⁵N nuclear magnetic resonance relaxation analysis and functional mutagenesis studies in the context of our previous structural and mutagenesis work to correlate structure, dynamics and function for the seventh transmembrane segment of the human Na⁺/H⁺ exchanger isoform 1. Although G261-S263 was previously identified as an interruption point in the helical structure of this isolated transmembrane peptide in dodecylphosphocholine micelles, and rapid conformational exchange was implicated in the NOE measurements, the six ¹⁵N labelled residues examined in this study all have similar dynamics on the ps-ns time scale. A mathematical model incorporating chemical exchange is the best fit for residues G261, L264, and A268. This implies that a segment of residues from G261 to A268 samples different conformations on the μs-ms time scale. Chemical exchange on an intermediate time scale is consistent with an alternating-access cycle where E262 is bent away from the cytosol during proton translocation by the exchanger. The functional importance of chemical exchange at G261-A268 is corroborated by the abrogated activity of the full-length exchanger with the bulky and restricting Ile substitutions F260I, G261I, E262I, S263I, and A268I.     

Amino acids as a nitrogen source for tomato seedlings: The use of dual-labeled (C, N) glycine to test for direct uptake by tomato seedlings

Direct uptake of organic nitrogen (ON) compounds, rather than inorganic N, by plant roots has been hypothesized to constitute a significant pathway for plant nutrition. The aim of this study was to test whether tomatoes (Solanum lycopersicum cv. Huying932) can take up ON directly from the soil by using ¹⁵NH₄Cl, K¹⁵NO₃, 1, 2-¹³C₂¹⁵N-glycine labeling techniques. The ¹³C and ¹⁵N in the plants increased significantly indicating that a portion of the glycine-N was taken up in the form of intact amino acids by the tomatoes within 48 h after injection into the soil. Regression analysis of excess ¹³C against excess ¹⁵N showed that approximately 21% of the supplied glycine-N was taken up intact by the tomatoes. Atom% excesses of ¹⁵N and ¹³C in the roots were higher than in any shoots. Results also indicated rapid turnover of amino acids (e.g., glycine) by soil microorganisms, and the poor competitive ability of tomatoes in absorbing amino acids from the soil solution. This implies that tomatoes can take up ON in an intact form from the soil despite the rapid turnover of organic N usually found under such conditions. Given the influence of climatic change and N pollution, further studies investigating the functional ecological implications of ON in horticultural ecosystems are warranted.     

Long-term exposure of the freshwater shrimp Macrobrachium olfersii to elevated salinity: Effects on gill (Na,K)-ATPase α-subunit expression and K-phosphatase activity

The kinetic properties of a microsomal gill (Na⁺,K⁺)-ATPase from the freshwater shrimp, Macrobrachium olfersii, acclimated to 21‰ salinity for 10 days were investigated using the substrate p-nitrophenylphosphate. The enzyme hydrolyzed this substrate obeying cooperative kinetics at a rate of 123.6 ± 4.9 U mg^− 1 and K_0.5 = 1.31 ± 0.05 mmol L^− 1. Stimulation of K⁺-phosphatase activity by magnesium (V_max = 125.3 ± 7.5 U mg^− 1; K_0.5 = 2.09 ± 0.06 mmol L^− 1), potassium (V_max = 134.2 ± 6.7 U mg^− 1; K_0.5 = 1.33 ± 0.06 mmol L^− 1) and ammonium ions (V_max = 130.1 ± 5.9 U mg^− 1; K_0.5 = 11.4 ± 0.5 mmol L^− 1) was also cooperative. While orthovanadate abolished p-nitrophenylphosphatase activity, ouabain inhibition reached 80% (K_I = 304.9 ± 18.3 μmol L^− 1). The kinetic parameters estimated differ significantly from those for freshwater-acclimated shrimps, suggesting expression of different isoenzymes during salinity adaptation. Despite the ≈2-fold reduction in K⁺-phosphatase specific activity, Western blotting analysis revealed similar α-subunit expression in gill tissue from shrimps acclimated to 21‰ salinity or fresh water, although expression of phosphate-hydrolyzing enzymes other than (Na⁺,K⁺)-ATPase was stimulated by high salinity acclimation.     

Morphofunctional changes in Leydig cells throughout the continuous spermatogenesis of the freshwater teleost fish, Serrasalmus spilopleura (Characiformes, Characidae): an ultrastructural and enzyme study

The freshwater fish Serrasalmus spilopleura (piranha) has a continuous type of reproduction; gametes are constantly produced and released during the reproductive cycle. The testes do not undergo seasonal morphological changes but exhibit two constant regions throughout the year: the medullar region (involved with spermatogenesis) and the cortical region (involved with spermiation and sperm storage). We have evaluated the ultrastructure of the Leydig cells and the activity of 3beta-HSD (an essential enzyme related to steroid hormone biosynthesis) and acid phosphatase (AcPase; lysosomal marker enzyme) in these two regions. The activity of 3beta-HSD is stronger in the medullar region, and the Leydig cells in this region have a variety of cytological features that reflect differences in hormone synthesis and/or that could be linked to steroidogenic cells under various degrees of hormonal activity. In the cortical region, 3beta-HSD activity is weak and the Leydig cells exhibit signs of degeneration, as confirmed by their ultrastructure and intense AcPase activity. These degenerative signs are indicative of cytoplasmic remodelling to degrade steroidogenic enzymes, such as 3beta-HSD, that could lead to senescence or even to autophagic cell degeneration. S. spilopleura thus constitutes an interesting model for increasing our understanding of steroidogenesis control in freshwater teleost fish.     

Comparisons of phylogenetic hypotheses among different data sets in dwarf dandelions (Krigia,Asteraceae): Additional information from internal transcribed spacer sequences of nuclear ribosomal DNA

The internal transcribed spacer (ITS) region of the 18 S–25 S nuclear ribosomal DNA repeat was sequenced from 19 populations of the tribeLactuceae, including all species of dwarf dandelion (Krigia) and five outgroup genera. The incidence of length changes and base substitutions was at least two times higher for ITS 1 than ITS 2. Interspecific sequence divergence withinKrigia averaged 9.62% (1.61%–15.19%) and 4.26% (0%–6.64%) in ITS 1 and ITS 2, respectively. Intergeneric sequence divergence ranged from 15.6% to 44.5% in ITS 1 and from 8.0% to 28.6% in ITS 2. High sequence divergence and homoplasy among genera of tribeLactuceae suggest that the phylogenetic utility of ITS sequence data is limited to interspecific studies or comparisons among closely related genera. Trees generated from ITS sequences are essentially identical to those from restriction site comparisons of the entire nuclear ribosomal (nr) DNA region. The degree of tree resolution differed depending on how gaps were treated in phylogenetic analyses. The ITS trees were congruent with the chloroplast DNA and morphological phylogenies in three major ways: 1) the sister group relationship betweenKrigia andPyrrhopappus; 2) the recognition of two monophyletic sections,Krigia andCymbia, in genusKrigia; and 3) the monophyly of theK. occidentalis-K. cespitosa clade in sect.Cymbia. However, the two nrDNA-based trees are not congruent with morphology/chloroplast DNA-based trees for the interspecific relationships in sect.Krigia. An average of 22.5% incongruence was observed among fourKrigia data sets. The relatively high degree of incongruence among data sets is due primarily to conflict between trees based on nrDNA and morphological/cpDNA data. The incongruence is probably due to the concerted evolution of nrDNA repeating units. The results fromKrigia and theLactuceae suggest that nrDNA data may have limited utility in phylogenetic studies of plants, especially in groups which exhibit high levels of sequence divergence. Our combined phylogenetic analysis as a total evidence shows the least conflict to each of the individual data sets.     

Neuropeptides in the intestine of two teleost species (Oreochromis mossambicus,Carassius auratus): Localization and electrophysiological effects on the epithelium

Summary The presence of bioactive peptides in the gut and their possible electrophysiological effects on the intestinal epithelium were studied in two teleost species, the tilapia (Oreochromis mossambicus) and the goldfish (Carassius auratus). Vasoactive intestinal polypeptide-like immunoreactive nerve fibres were found beneath the intestinal epithelium of both species. Galanin-, metenkephalin-and calcitonin gene-related peptide-like immunoreactive nerve fibres were found exclusively in the mucosa of the tilapia. Both species had vasoactive intestinal polypeptide-, enkephalin- or neuropeptide Y-like immunoreactive endocrine cells; calcitonin gene-related peptide-like immunoreactive endocrine cells were additionally found in the tilapia. Somatostatin- and dopamine--hydroxylase-like immunoreactivities were not observed. Nerve cell bodies in the myenteric plexus of both species showed immunoreactivity for calcitonin gene-related peptide-, vasoactive intestinal polypeptide-, and galanin-like peptide. Enkephalin-like immunoreactive nerve cell bodies were present in the tilapia only. None of the peptides had a pronounced electrogenic effect. However, calcitonin gene-related peptide added to stripped intestinal epithelium of the tilapia, reduced the ion selectivity, and addition of galanin increased the ion selectivity. In goldfish intestine, both galanin and calcitonin gene-related peptide were without effect. Enkephalin counteracted the serotonin-induced reduction of the ion selectivity of the goldfish intestinal epithelium, but had no effect on the tilapia epithelium. In both species, vasoactive intestinal polypeptide reduced the ion selectivity of the intestinal epithelium, and neuropeptide Y induced an increase of the ion selectivity. Somatostatin showed no effect on the epithelial ion selectivity of either species. Tetrodotoxin did not inhibit the effects of the peptides studied. The changes in ion selectivity suggest that the enterocytes may be under the regulatory control of these peptides.     

Immunocytochemical localization of serotonin and photoreceptor-specific proteins (rod-opsin,S-antigen) in the pineal complex of the river lamprey,Lampetra japonica,with special reference to photoneuroendocrine cells

Summary The pineal complex of the river lamprey, Lampetra japonica, was examined by means of immunocytochemistry with antisera against serotonin, the precursor of melatonin, and two photoreceptor proteins, rod-opsin (the apoprotein of the photopigment rhodopsin) and S-antigen. Serotonin-immunoreactive cells were observed in both the pineal and the parapineal organ. The proximal portion of the pineal organ (atrium) comprised numerous serotonin-immunoreactive cells displaying spherical somata. In the distal end-vesicle of the pineal organ, the serotonin-immunoreactive elements resembled photoreceptors in their size and shape. These cells projecting into the pineal lumen and toward the basal lamina were especially conspicuous in the ventral portion of the end-vesicle. In addition, single serotonin-immunoreactive nerve cells were found in this location. Retinal photoreceptors were never seen to contain immunoreactive serotonin; amacrine cells were the only retinal elements exhibiting serotonin immunoreaction. Strong S-antigen immunoreactivity was found in numerous photoreceptors located in the pineal end-vesicle. In contrast, the S-antigen immunoreactivity was weak in the spherical cells of the atrium. Thus, the pattern of S-antigen immunoreactivity was roughly opposite to that of serotonin. Similar findings were obtained in the parapineal organ. The rod-opsin immunoreaction was restricted to the outer segments of photoreceptors in the pineal end-vesicle and parapineal organ. No rodopsin immunoreactive outer segments occurred in the proximal portion of the atrium. Double immunostaining was employed to investigate whether immunoreactive opsin and serotonin are colocalized in one and the same cell. This approach revealed that (i) most of the rodopsin-immunoreactive outer segments in the end-vesicle belonged to serotonin-immunonegative photoreceptors; (ii) nearly all serotonin-immunoreactive cells in the end-vesicle bore short rod-opsin-immunoreactive outer segments protruding into the pineal lumen; and (iii) the spherical serotonin-immunoreactive cells in the pineal stalk lacked rod-opsin immunoreaction and an outer segment. These results support the concept that multiple cell lines of the photoreceptor type exist in the pineal complex at an early evolutionary stage.     

A facile synthesis of C-24 and C-25 oxysterols by in situ generated ethyl(trifluoromethyl)dioxirane

Experiments were performed to compare the regioselective hydroxylation of the isopropyl C-H bond at C-25 in 5α-cholestan-3β-yl acetate by in situ generated dimethyldioxirane, methyl(trifluoromethyl)dioxirane, hexafluoro(dimethyl)dioxirane or ethyl(trifluoromethyl)dioxirane (ETDO). The dioxiranes were generated from the corresponding ketones and potassium peroxymonosulfate in aq. NaHCO₃, pH 7.5-8.0. Of the four dioxiranes examined, partially fluorinated, sterically bulky ETDO displayed the highest reactivity and regioselectivity. Using in situ generated ETDO, a facile, synthesis was developed for two naturally occurring oxysterols, i.e., 25-hydroxycholesterol, as well as its 3-sulfate (overall yield of the sulfate, 24%) and 24-oxocholesterol (16%), starting from cholesterol.     

TRPC3-mediated Ca influx contributes to Rac1-mediated production of reactive oxygen species in MLP-deficient mouse hearts

Dilated cardiomyopathy (DCM) is a myocardial disorder that is characterized by dilation and dysfunction of the left ventricle (LV). Accumulating evidence has implicated aberrant Ca²⁺ signaling and oxidative stress in the progression of DCM, but the molecular details are unknown. In the present study, we report that inhibition of the transient receptor potential canonical 3 (TRPC3) channels partially prevents LV dilation and dysfunction in muscle LIM protein-deficient (MLP (−/−)) mice, a murine model of DCM. The expression level of TRPC3 and the activity of Ca²⁺/calmodulin-dependent kinase II (CaMKII) were increased in MLP (−/−) mouse hearts. Acitivity of Rac1, a small GTP-binding protein that participates in NADPH oxidase (Nox) activation, and the production of reactive oxygen species (ROS) were also increased in MLP (−/−) mouse hearts. Treatment with pyrazole-3, a TRPC3 selective inhibitor, strongly suppressed the increased activities of CaMKII and Rac1, as well as ROS production. In contrast, activation of TRPC3 by 1-oleoyl-2-acetyl-sn-glycerol (OAG), or by mechanical stretch, induced ROS production in rat neonatal cardiomyocytes. These results suggest that up-regulation of TRPC3 is responsible for the increase in CaMKII activity and the Nox-mediated ROS production in MLP (−/−) mouse cardiomyocytes, and that inhibition of TRPC3 is an effective therapeutic strategy to prevent the progression of DCM.     

NMR structural studies of the myristoylated N-terminus of ADP ribosylation factor 6 (Arf6)

Arf proteins are guanine nucleotide binding proteins that are implicated in endocytotic pathways and vesicle trafficking. The two widely studied isoforms of Arf proteins (Arf1 and Arf6) have different cellular functions and localizations but similar structures. Arf proteins have an N-terminal helix with a covalently bound myristoyl group. Except structural models, there are no three dimensional structures of the myristoylated N-terminal peptide or the intact myristoylated Arf proteins. However, understanding the role of both the myristoyl group and the N-terminal helix based on the details of their molecular structures is of great interest. In the solution structure of myristoylated N-terminal peptide of Arf6 described here, the myristoyl group folds toward the N-terminus to interact with the hydrophobic residues in particular, the phenyl ring. Also, the structure of the dodecylphosphocholine (DPC) micelle-bound of the peptide together with paramagnetic studies showed that the myristoyl group is inserted into the micelle while residues V4-G10 interact with the surface of the micelle. The structural differences between the unbound and micelle-bound myristoylated N-terminal peptide of Arf6 involves the myristoyl group and the side chains of the hydrophobic residues.     

EPR study of electron transport in the cyanobacterium Synechocystis sp. PCC 6803: Oxygen-dependent interrelations between photosynthetic and respiratory electron transport chains

In this work, we investigated electron transport processes in the cyanobacterium Synechocystis sp. PCC 6803, with a special emphasis focused on oxygen-dependent interrelations between photosynthetic and respiratory electron transport chains. Redox transients of the photosystem I primary donor P700 and oxygen exchange processes were measured by the EPR method under the same experimental conditions. To discriminate between the factors controlling electron flow through photosynthetic and respiratory electron transport chains, we compared the P700 redox transients and oxygen exchange processes in wild type cells and mutants with impaired photosystem II and terminal oxidases (CtaI, CydAB, CtaDEII). It was shown that the rates of electron flow through both photosynthetic and respiratory electron transport chains strongly depended on the transmembrane proton gradient and oxygen concentration in cell suspension. Electron transport through photosystem I was controlled by two main mechanisms: (i) oxygen-dependent acceleration of electron transfer from photosystem I to NADP⁺, and (ii) slowing down of electron flow between photosystem II and photosystem I governed by the intrathylakoid pH. Inhibitor analysis of P700 redox transients led us to the conclusion that electron fluxes from dehydrogenases and from cyclic electron transport pathway comprise 20-30% of the total electron flux from the intersystem electron transport chain to P700⁺.     

Rhipicephalus (Boophilus) microplus: distinct acute phase proteins vary during infestations according to the genetic composition of the bovine hosts, Bos taurus and Bos indicus

Tick bites may trigger acute phase responses. Positive and negative acute phase proteins were measured in infested cattle genetically resistant and susceptible to ticks. During heavier infestations levels of haptoglobin increased significantly in susceptible bovines; levels of serum amyloid A increased in resistant bovines; levels of alpha-1-acid glycoprotein decreased significantly in resistant bovines; levels of transferrin decreased significantly in susceptible bovines. In conclusion, tick infestations trigger acute phase responses and enhancement of specific acute phase proteins differs according to the genetic composition of hosts. Acute phase proteins may constitute useful biological signatures for monitoring the stress induced by tick infestations.     

Participation of chlorobiumquinone in the transplasma membrane electron transport system of Leishmania donovani promastigote: Effect of near-ultraviolet light on the redox reaction of plasma membrane

The respiratory quinone composition of the parasitic protozoa Leishmania donovani promastigote was investigated. 1′-oxomenaquinone-7, a chlorobiumquinone was found to be the major isoprenoid quinone. Substantial level of ubiquinone-9 was also present. Isolation and identification of the quinone from the purified plasma membrane yielded mainly 1′-oxomenaquinone-7 and ubiquinone-9; menaquinone was not detected. Membrane bound 1′-oxomenaquinone-7 could be destroyed by near-ultraviolet irradiation, with a concomitant loss or stimulation of plasma membrane electron transport activities. The abilities of different quinones to restore α-lipoic acid and ferricyanide reductase activity in near UV-irradiated cell preparations were compared. The order was; conjugate of chlorobiumquinone and sphingosine base ? conjugate of 2-methyl-3-(1′-oxooctadecyl)-1,4-napthoquinone and octadecylamine >> chlorobiumquinone ? 2-methyl-3-(1′-oxooctadecyl)-1,4-napthoquinone > menaquinone-4 ? ubiquinone-10. After irradiation with near-UV light, transmembrane α-lipoic acid reduction was inhibited, while transmembrane ferricyanide reduction was stimulated. The result obtained indicates that chlorobiumquinone mediates the plasma membrane electron transport between cytosolic reductant and oxygen as well as α-lipoic acid. UV-inactivation of chlorobiumquinone shuts down the plasma membrane oxygen uptake and diverts the electron flux towards ferricyanide reduction via ubiquinone-9. Chlorobiumquinone is the only example of a polyisoprenoid quinone containing a side chain carbonyl group from photosynthetic green-sulphur bacteria. Recent work has revealed numerous genes of trypanosomatid sharing common ancestry with plants and/or bacteria. These observations pose some fascinating questions about the evolutionary biology of this important group of parasitic protozoa.