Photophosphorylation in Scenedesmus in vivo: O2 evolution, ATP pools and transients, and phosphate binding during photoreduction of NO3−, NO2− and CO2

The relation between light-induced electron transport with NO₃^?, NO₂^? or CO₂ as acceptors, ATP pools and transients in dark-light-dark transitions, and phosphate uptake was examined in phosphorus-starved cells of Scenedesmus obtusiusculus Chod. Net O₂ evolution at saturating light was around 6 μmol × (mg chlorophyll × h)^?1 in the absence of any acceptor, but reached average rates of 21, 65 and 145 μmol × (mg chlorophyll × h)^?1 upon additions of 5 mM KNO₃, KNO₂ and KHCO₃, respectively. The apparent rate of photophosphorylation in transition experiments was only a few percent of the rate calculated from CO₂-dependent O₂ evolution. Blocking non-cyclic electron transport with DCMU inhibited phosphate assimilation, but acceleration of non-cyclic electron flow by addition of NO₃^? or NO₂^? did not stimulate phosphate assimilation as compared to the situation without an acceptor. A functional non-cyclic system might primarily be needed for an efficient shuttle transfer of ATP from the chloroplast to the cytoplasm. An inhibition of the non-cyclic system due to lack of reducible substrates accelerates the cyclic system and thus indicates a regulation mechanism between the two systems.     

MITOSIS AND CYTOKINESIS IN ASTEROMONAS GRACILIS, A WALL-LESS GREEN MONAD1

Asteromonas gracilis Artari remains motile throughout cell division. Basal bodies separate and replicate at prophase. They are located lateral to the poles of the closed metaphase spindle. Kinetochores appear at late metaphase. Chromosomes move to the poles and extensions of the nuclear envelope develop into the pyrenoid at anaphase. The interzonal spindle disintegrates at telophase and a diffuse phycoplast is present. Cytokinesis proceeds rapidly from the anterior region of the cell. Newly formed daughter cells have four narrow-banded rootlets and both distal and proximal fibers connect the basal bodies. Features of cell division in Asteromonas are compared to those in other algae, particularly Dunaliella and Chlamydomonas.     

Tyrosine Hydroxylase Phosphorylation in Bovine Adrenal Chromaffin Cells: The Role of Intracellular Ca2+ in the Histamine H1 Receptor-Stimulated Phosphorylation of Ser8, Ser19, Ser31, and Ser40

Abstract: Tyrosine hydroxylase (TOH), the rate-limiting enzyme in catecholamine biosynthesis, is regulated by phosphorylation. Activation of histaminergic H₁ receptors on cultured bovine adrenal chromaffin cells stimulated a rapid increase in TOH phosphorylation (within 5 s) that was sustained for at least 5 min. The initial increase in TOH phosphorylation (up to 1 min) was essentially unchanged by the removal of extracellular Ca²⁺. In contrast, the H₁-mediated response was abolished by preloading the cells with BAPTA acetoxymethyl ester (50 µ M ) and significantly reduced by prior exposure to caffeine (10 m M for 10 min) to deplete intracellular Ca²⁺. Trypticphosphopeptide analysis by HPLC revealed that the H₁ response in the presence or absence of extracellular Ca²⁺ resulted in a major increase in the phosphorylation of Ser¹⁹ with smaller increases in that of Ser⁴⁰ and Ser³¹. In contrast, although a brief stimulation with nicotine (30 µ M for 60 s) also resulted in a major increase in Ser¹⁹ phosphorylation, this response was abolished in the absence of extracellular Ca²⁺. These data indicate that the mobilization of intracellular Ca²⁺ plays a crucial role in supporting H₁-mediated TOH phosphorylation and may thus have a potentially important role in regulating catecholamine synthesis.     

Präadaptation, Wirtskreiserweiterung and Parallel-Cladogenese in der Evolution von phytophagen Insekten1, 2

Preadaptation, host shifts and parallel cladogenesis in the evolution of phytophagous insects In this contribution we investigate the possibilities to apply concepts developed for the evolution of animal parasites to insect-plant systems. We compare host parasite systems in animals with plant-herbivore systems and list similarities and differences. The terms preadaptation, predisposition, expansion and contraction of host ranges, and parallel cladogenesis are discussed. We enumerate general preadaptations for the evolution of herbivory in insects and preadaptations for shifts between herbivory and entomophagy. Examples are given for expansions of host ranges based on phytochemical or structural characters of host plants. Cases of parallel cladogenesis in herbivoreparasitoid systems and plant-herbivore systems are compiled from the literature. An analysis of the insect fauna of the “thistles” (Cynaroideae) in the Palearctic and Nearctic demonstrates the importance of the evolutionary history of the plant taxa and of the existence of preadapted pools of herbivores for the evolution of guilds of specialized herbivores. The members of the Curculionid taxon Cleoninae provide examples for multiple colonizations and radiations of herbivores on the Cynaroideae. The taxonomic and biological relationships of the weevil genera Rhinocyllus, Bangasternus and Larinus which exploit the flower heads of Cynaroideae, can be interpreted as result of a basic parallel cladogenesis between herbivore and host. A gelelectrophoretic analysis of Larinus spp. supports this hypothesis.     

Impairment of Na+,K+-ATPase activity following enterotoxigenic Campylobacter jejuni infection: changes in Na+, Cl− and 3-O-methyl-D-glucose transport in vitro, in rat ileum

Abstract Unidirectional fluxes of Na⁺, Cl⁻ and 3-O-methyl-D-glucose (3-MG) were measured in vitro across Campylobacter jejuni live culture-infected and control rat ileal short-circuited tissues by the Using Chamber technique. Net secretion of Na⁺ and enhanced secretion of Cl⁻ ions was observed in the infected animals ( P < 0.001, n =6) as compared to the net absorption of Na⁺ and marginal secretion of Cl⁻ ions in the control animals. There was a significant decrease in the mucosal-to-serosal fluxes of 3-MG in C. jejuni -infected rat ileum. The specific Na⁺,K⁺-ATPase activity when measured biochemically in the membrane-rich fraction of enterocytes was found to be significantly lower (58%) in the infected group as compared to the control group ( P < 0.001). Our results therefore suggest that infection with an enterotoxigenic C. jejuni inhibits the Na⁺,K⁺-ATPase activity in rat enterocytes. The impairment of Na⁺,K⁺-ATPase activity thus appears to induce a secondary change in Na⁺,Cl⁻ and 3-MG transport in vitro in rat ileum.     

Bovine haemoglobin βA Zebu, βA43(CD3)Ser Thr: an intermediate globin type between the βA and βD Zambia is present in Indian zebu cattle

Two bovine haemoglobin beta chains, electrophoretically identical with the beta A chain of Herefords, were obtained from Ongole and Banteng, Bos javanicus, cattle. The amino acid residue differences of the two beta chains were compared by electrophoresis, cation-exchange and reverse-phase chromatography, amino acid analyses, and Edman degradation in comparison with beta A chain. The results showed that two beta chains differed from the beta A chain of the Hereford breed by the substitution of serine with threonine at the beta 43 position. No other difference was found between the two chains and beta A. This new beta chain type was termed beta A Zebu, which forms a possible evolutionarily transitional type between the beta A and the rare variant beta D Zambia found previously in African zebu cattle. The beta A Zebu differentiates from the previous beta B by at least four amino acid substitutions involving five codon-base changes.     

2H+:1 malate2− stoichiometry during Crassulacean Acid Metabolism is unaffected by lipophilic cations

Abstract. Lipophilic cations inhibit nocturnal malic acid accumulation in leaf cells of the Crassulacean Acid Metabolism plant Kalanchoë tubiflora . perhaps by interacting directly or indirectly with active malic acid transport into the vacuoles. Lipophilic cations do not affect passive efflux of malic acid from the vacuoles. Membrane potentials are depolarized, oxygen uptake is stimulated by lipophilic cations and there may also be stomatal responses. Thus it is striking that lipophilic cations do not alter the stoichiometry of 2 titratable H : 1 enzymatically-determined malate²⁻ during diurnal malic acid oscillations of Crassulacean Acid Metabolism in Kalanchoë . This suggests that coupling between protons and malate during transport into the vacuole must be tight. Transport as undissociated acid is unlikely because the dissociation equilibrium in the cytoplasm is largely on the side of malate²⁻. These results appear to suggest an intimate molecular interaction between a proton pump and a presumed malate²⁻ translocator at the tonoplast of leaf cells with Crassulacean Acid Metabolism.     

Studies on lipopeptide biosynthesis by Bacillus subtilis: Isolation and characterization of iturin−, surfactin+ mutants

Abstract Two mutant strains, M35 and M89, were obtained by UV irradiation from a wild-type Bacillus subtilis producing iturin and surfactin. Sporulation and surfactin production were similar in both mutants and in the parent strain, while the iturin production of M35 was 300-fold less than that of the wild-type strain; M89 did not produce any iturin. The analysis of the incorporation of sodium [1-¹⁴C]acetate into cellular lipids and lipopeptides showed that M89 still synthesized β-amino fatty acids, the lipid moiety of iturin.     

Distribution of Na+, K+-ATPase α-Subunit Isoforms in Rat Pituitary

The distributions of alpha-subunit isoforms of the Na+,K(+)-ATPase in rat pituitary were determined by immunoblotting and immunohistochemistry. Immunoreactivity for all three forms is present in the neural lobe, whereas the anterior lobe contains only alpha 1 and alpha 2. Most areas of the intermediate lobe exhibit faint immunoreactivity for only alpha 1, but thin strands of cells which stain strongly for all three isoforms are also present in this lobe. The previously reported ouabain inhibitable Na+,K(+)-ATPase activity in the neural lobe is consistent with the presence of both alpha 2 and alpha 3 subunits.     

Lan-1: A Human Neuroblastoma Cell Line With M1 and M3 Muscarinic Receptor Subtypes Coupled to Intracellular Ca2+ Elevation and Lacking Ca2+ Channels Activated by Membrane Depolarization

The LAN-1 clone, a cell line derived from a human neuroblastoma, possesses muscarinic receptors. The stimulation of these receptors with increasing concentrations of carbachol (CCh; 1-1,000 microM) caused a dose-dependent increase of the intracellular free Ca2+ concentration ([Ca2+]i). This increase was characterized by an early peak phase (10 s) and a late plateau phase. The removal of extracellular Ca2+ reduced the magnitude of the peak phase to approximately 70% but completely abolished the plateau phase. The muscarinic-activated Ca2+ channel was gadolinium (Gd3+) blockade and nimodipine and omega-conotoxin insensitive. In addition, membrane depolarization did not cause any increase in [Ca2+]i. The CCh-induced [Ca2+]i elevation was concentration-dependently inhibited by pirenzepine and 4-diphenylacetoxy-N-methylpiperidine methiodide, two rather selective antagonists of M1 and M3 muscarinic receptor subtypes, respectively, whereas methoctramine, an M2 antagonist, was ineffective. The coupling of M1 and M3 receptor activation with [Ca2+]i elevation does not seem to be mediated by a pertussis toxin-sensitive guanine nucleotide-binding protein or by the diacylglycerol-protein kinase C system. The mobilization of [Ca2+]i elicited by M1 and M3 muscarinic receptor stimulation seems to be dependent on an inositol trisphosphate-sensitive intracellular store. In addition, ryanodine did not prevent CCh-induced [Ca2+]i mobilization, and, finally, LAN-1 cells appear to lack caffeine-sensitive Ca2+ stores, because the methylxanthine was unable to elicit intracellular Ca2+ mobilization, under basal conditions, after a subthreshold concentration of CCh (0.3 microM), or after thapsigargin.     

Die Ölblumensymbiosen – Parallelismus and andere Aspekte ihrer Entwicklung in Raum and Zeit1, 2

The oil-bee/oil-flower relationships: parallelism and other aspects of their evolution in space and time A survey is given of our present knowledge and existing hypotheses concerning the biogeography, history, and phylogeny of plant taxa yielding fatty oil as a floral reward, and of the bee genera involved in their pollination. Four syngenetic complexes of the symbiosis arose convergently: The neotropical, the paleotropical, the holarctic, and the capensic complex. On the basis of the mutual structural adaptations of bees and flowers it is concluded that, in addition, parallelism within related groups as a result of a common tendency to develop the respective organs, has played an important role in the evolution of the oil-based floral interrelationships.     

Specificity of rabbit antisera against the rough lipopolysaccharide of Salmonella minnesota strain R7 (chemotype Rd1P−)

Abstract Rabbit polyclonal antibodies against the lipopolysaccharide (LPS) of the Rd₁P⁻ mutant strain R7 of Salmonella minnesota were serologically characterized using R7 LPS, dephosphorylated LPS, deacylated LPS, deacylated, dephosphorylated and reduced LPS, and synthetic partial structures. The latter comprised partial structures of the core region of Rd₁P⁻ LPS bound to the β 1 → 6-linked glucosamine disaccharide with two amide-linked 3-hydroxytetradecanoic acid residues or artificial glycoconjugates comprised of the synthetic oligosaccharides coupled to bovine serum albumin. Using a passive hemolysis and an enzyme immunoassay, absorption and inhibition experiments, the antibody specificities present could be determined. One group of antibodies required components of the core region and the phosphorylated glucosamine disaccharide of the lipid A moiety for binding. The majority of phosphate-independent antibodies was directed against the trisaccharide l -glycero-α- d -manno-heptopyranose(1 → 3)- l -glycero-α- d -manno-heptopyranose(1 → 5)3-deoxy- d -manno-octulosonic acid. Antibodies against the 1 → 3- and 1 → 7-linked heptose disaccharides and against a single heptose were also detected, however, with low titers. No antibodies were found which required the presence of fatty acids.     

CA2+ BINDING PROTEIN CALRETICULIN IN CHLAMYDOMONAS REINHARDTII (CHLOROPHYTA): BIOCHEMICAL CHARACTERIZATION, DIFFERENTIAL EXPRESSION DURING SEXUAL REPRODUCTION, AND PHYLOGENETIC ANALYSIS

The occurrence of calreticulin, the main Ca²⁺ binding protein in the endoplasmic reticulum of eukaryotic cells, was investigated in the unicellular green alga Chlamydomonas reinhardtii Dangeard. The biochemical characterization of a diethylaminoethyl purified extract highlighted the presence, on SDS-PAGE, of a 55-kDa protein that stained blue with the Stains All dye, a diagnostic feature of acidic Ca²⁺ binding proteins. Immunoblot analyses revealed a strong cross-reaction of the Chlamydomonas reinhardtii protein with antibodies to plant calreticulins and the endoplasmic reticulum retention signal HDEL. Furthermore, the 55-kDa protein bound [⁴⁵Ca²⁺] and had an acidic isoelectric point (pI = 4.9) but was neither glycosylated nor phosphorylated. N-terminal sequencing revealed strong amino acid sequence similarity to calreticulin from other sources. The presence of calreticulin in Chlamydomonas reinhardtii suggested that an endoplasmic reticulum Ca²⁺ buffering mechanism was present in this unicellular chlorophyte. The data suggest an early origin and high conservation of endoplasmic-reticulum-mediated Ca²⁺ functions in eukaryotes, whereby specific posttranslational modifications of the proteinhave been specifically acquired in different lineages of photosynthetic eukaryotes. Moreover, northern and western blot analysis experiments showed a regulation of calreticulin expression during Chlamydomonas sexual reproduction with a high abundance of calreticulin mRNA and protein in reproductive cells.     

The brain-specific protein, p42IP4 (ADAP 1) is localized in mitochondria and involved in regulation of mitochondrial Ca2+

In brain, p42^IP4 (centaurin‐α1; recently named ADAP 1, which signifies ADP ribosylation factor GTPase activating protein with dual PH domains 1, within the large family of Arf‐GTPase activating proteins) is mainly expressed in neurons. p42^IP4 operates as a dual receptor recognising two second messengers, the soluble inositol(1,3,4,5)tetrakisphosphate and the lipid phosphatidylinositol(3,4,5)trisphosphate. We show here for the first time that p42^IP4 is localized in mitochondria, isolated from rat brain and from cells transfected with p42^IP4. In rat brain mitochondria we additionally found interaction of p42^IP4 with 2′, 3′‐cyclic nucleotide 3′‐phosphodiesterase and α‐tubulin by pull‐down binding assay and by immunoprecipitation. In mitochondria from Chinese hamster ovary cells, p42^IP4 is predominantly associated with the intermembrane space and the inner membrane. This localization of p42^IP4 indicates that p42^IP4 might have a still unknown mitochondrial function. We studied whether p42^IP4 is involved in Ca²⁺‐induced permeability transition pore opening, which is important in mitochondrial events leading to programmed cell death. We used mouse neuroblastoma cells as a model for the functional studies of p42^IP4 in mitochondria. In mitochondria isolated from p42^IP4‐transfected mouse neuroblastoma cells, over‐expression of p42^IP4 significantly decreased Ca²⁺ capacity and lag time for Ca²⁺ retention. Thus, we suggest that p42^IP4 is involved in the regulation of Ca²⁺ transport in mitochondria. We propose that p42^IP4 promotes Ca²⁺‐induced permeability transition pore opening and thus destabilizes mitochondria.