Mass-spectrometric determination of O2 and CO2 gas exchange in illuminated higher-plant cells

In order to estimate photosynthetic and respiratory rates in illuminated photoautotrophic cells of carnation (Dianthus caryophyllus L.), simultaneous measurements of CO₂ and O₂ gas exchange were performed using ¹⁸O₂, ¹³CO₂ and a mass-spectrometry technique. This method allowed the determination, and thus the comparison, of unidirectional fluxes of O₂ and CO₂. In optimum photosynthetic conditions (i.e. in the presence of high light and a saturating level of CO₂), the rate of CO₂ influx represented 75±5% of the rate of gross O₂ evolution. After a dark-to-light transition, the rate of CO₂ efflux was inhibited by 50% whereas the O₂-uptake rate was little affected. The effect of a recycling of respiratory CO₂ through photosynthesis on the exchange of CO₂ gas was investigated using a mathematical model. The confliction of the experimental data with the simulated gas-exchange rates strongly supported the view that CO₂ recycling was a minor event in these cells and could not be responsible for the observed inhibition of CO₂ efflux. On the basis of this assumption it was concluded that illumination of carnation cells resulted in a decrease of substrate decarboxylations, and that CO₂ efflux and O₂ uptake were not as tightly coupled in the light as in the dark. Furthermore, it could be calculated from the rate of gross photosynthesis that the chloroplastic electron-transport chain produced enough ATP in the light to account for the measured CO₂-uptake rate without involving cyclic transfer of electrons around PS I or mitochondrial supplementation.Abbreviations Chl chlorophyll - K_d permeability coefficient The authors thank Drs A. Vermeglio and P. Thibault, Dépt. de Biologie, CEN-Cadarache, St. Paul Lez Durance, France, for helpful discussions.     

Cestodes of birds from the Ivory Coast. Species of the genus Anonchotaenia Cohn, 1990

Five taxa included in the cestode genus Anonchotaenia (Cyclophyllidea, Paruterinidae) have been found in various birds from the Ivory Coast (West Africa). The hosts belong to the families Hirundinidae and Corvidae. A. (Paranonchotaenia) prionopos n. sp., parasitic in Prionops plumata, and A. (P.) malaconoti n. sp, parasitic in Malaconotus blanchoti, are placed in a new subgenus named Paranonchotaenia, which is erected for the Anonchotaenia species showing genital ducts passing between the longitudinal excretory stems. A. (P.) prionopos is characterised by a rather short cirrus-pouch, six to seven testes, and an integumental cavity at the distal extremity of the cirrus-pouch in gravid proglottides. A. (P.) malaconoti differs from the former species mainly by the larger cirrus-pouch and a slightly greater number of testes. The other three species are A. longiovata, parasitic in Hirundo semirufa; A. globata, parasitic in Psadiloprocne obscura (the latter two species are recorded from new hosts and new geographical areas); and Anonchotaenia sp., parasitic in Hirundo rustica. It is assumed that the subgenus A. (Anonchotaenia) is rather a parasite of the Passerida and that the subgenus A. (Paranonchotaenia) tends to be parasitic in the Corvida.This paper is a part of the author's thesis.This paper is a part of the author's thesis.     

Universal primers for amplification of three non-coding regions of chloroplast DNA

Six primers for the amplification of three non-coding regions of chloroplast DNA via the polymerase chain reaction (PCR) have been designed. In order to find out whether these primers were universal, we used them in an attempt to amplify DNA from various plant species. The primers worked for most species tested including algae, bryophytes, pteridophytes, gymnosperms and angiosperms. The fact that they amplify chloroplast DNA non-coding regions over a wide taxonomic range means that these primers may be used to study the population biology (in supplying markers) and evolution (inter- and probably intraspecific phylogenies) of plants.     

Immunochemical characterisation of parathyroid hormone-related protein from tumor and non-tumor cells

The molecular forms of parathyroid hormone-related protein (PTHRP) in conditioned media from the BEN human lung cancer cell line, rat parathyroid cells (PT-r) and human keratinocytes were studied by gel-filtraton chromatography with assay of PTHRP by immunoassays and bioassay. Immunoreactivity (1–86 and 1–34) and bioactivity (1–34) in conditioned media eluted as a coincident major peak (approx. molecular mass 19–22 kDa) and there was evidence of amino-terminal species in the molecular mass range 10–16 kDa in BEN and keratinocyte media. Western blotting of PTHRP affinity purified by monoclonal antibodies directed at regions 1–34 or 37–67, identified a major species in all cell cytosols and media with an apparent molecular mass of 24–25 kDa, consistently slighty larger than recombinant PTHRP(1–141) (mobility of 21 kDa) which may represent an intact or native form of PTHRP. Additional amino-terminal species were identified in medium from keratinocytes (16 and 7 kDa), BEN cells (18 and 14 kDa) and PT-R cells (17 kDa), suggesting that processing occurs at the C-terminus and within the mid-region to form a range of amino-terminal fragments.     

Computation of relaxation matrix elements from incomplete NOESY data sets

Summary The structural determination of biological molecules in solution by NMR relies on the determination of a set of interatomic distances obtained by measurement of intramolecular nuclear Overhauser effects (NOE). It is shown in this paper that it is possible to obtain the accurate relaxation rate (and hence the interatomic distance) from the direct measurement of a single NOE signal. The precise analysis of a NOESY peak evolution with respect to the mixing time allows the evaluation of the relaxation parameters for the pair of spins under consideration. This is done without any assumption on the relaxation of unmeasured spins, or on the movement of the molecule. The theoretical basis of this method is presented. In order to evaluate the proposed method, a simulated case on the protein BPTI is studied, which shows that the method performs very well even in the case of noisy data sets.     

Liquefaction of dulse (Palmaria palmata (L.) Kuntze) by a commercial enzyme preparation and a purified endo ,β-1,4-D-xylanase

Liquefaction of dry and freshPalmaria palmata by food grade enzyme preparations and a purified endo--1,4-D-xylanase was studied.The endo--1,4-D-xylanase (EC 3.2.1.8) was purified to homogeneity from a commercial food grade enzyme prepared fromAspergillus niger. It has a molecular weight of 22 500, a pI of 3.5, is inactive toward corn arabinoxylan,p-nitrophenyl--D-xylose, carboxymethyl cellulose but shows a weak activity toward microcrystalline cellulose. It hydrolyzes oat and dulse xylan equally well in seawater and deionized water essentially into xylose and xylobiose. It is stable between pH 5.5 to 9.0 and 0 to 30 °C and its activity is optimal at pH 4.5–5.5 and 40–60 °C. It has a K_m of 2.2 and 2.8 mg ml^-1 and V_max of 3600 and 3900 nkat mg^-1 of protein on oat and dulse xylan, respectively.Acetate buffer, deionized water and seawater alone extracted 62.6 to 64.5 % of the dry weight of dry dulse, but the use of commercial food grade enzyme preparations or the purified xylanase improved liquefaction to 81.2–87.1 %. Xylose and galactose were the only sugars present in the soluble extracts. Deionized and seawater extracted 58.8–52.7 and 39.1–42.2% of the dry weight of the fresh algae collected in fall and summer, respectively. Only galactose was found in the seawater extract, while some xylose with galactose were measured in the deionized water extract of the fresh autumn algal sample. Purified and crude xylanase improved liquefaction of fresh algae to 79.8–81.4 and 71.9–77.9% of the fresh dry weight (fall and summer, respectively) in deionized and seawater, respectively, and increased the xylose content of the soluble fractions. Polysaccharides in the soluble residues were composed of 1,3/1,4-linked xylose, 1-linked galactose (floridoside) and 1,4-linked glucose (cellulose) and contained essentially 1,4-linked xylose and 1,4-linked glucose in insoluble fractions obtained after enzymatic treatment.The use of xylanase-containing food grade enzyme preparations improves liquefaction ofPalmaria palmata, particularly from fresh alga. This study indicates that processing such as drying may modify markedly the solubility ofP. palmata cell wall polysaccharides, which would imply the existence of some organization and/or other components in the fresh cell wall that lower xylan solubility in seawater.     

A multi-recombination model for the mtDNA rearrangements seen in maize cmsT regenerated plants

Regeneration of plants from maize cytoplasmic male sterile type T (cmsT) callus tissue culture promotes, in some instances, genetic variability in their mitochondrial genomes. These mutations have been analyzed in various cmsT regenerated plants that have or have not regained the male fertile phenotype. A unique multi-recombination model explains the various mitochondrial genome rearrangements. First, recombination involving two different sets of direct repeats gives rise to subgenomic recombinant circles. Second, intermolecular recombination between some selected subgenomes gives rise to a new rearranged master chromosome. The consequence of these events is the formation of a new master chromosome containing sequence deletions and duplications when compared to the progenitor. This new mitochondrial genome seems stable, although it does not contain the entire genetic complexity of the progenitor.     

Novel heme-binding component in the serum of the channel catfish (Ictalurus punctatus)

The serum of the channel catfish (Ictalurus punctatus) was examined for heme- and hemoglobin-binding proteins. Electrophoretic mobility retardation assays failed to detect a hemoglobin-binding material similar to mammalian haptoglobin; however, a heme-binding component (not previously described) was identified in catfish seru. The heme-binding component was purified by gel filtration chromatography; electrophoretic analyses suggested it to be composed of two polypeptide subunits of molecular masses about 115 and 98 kDa. This composition is inconsistent with hemopexin, the known heme-binding serum protein of mammals. Although it was not fully saturated with heme, the catfish component contained detectable heme in normal sera. When complexed by the binding material, heme was used as an iron source by isolates of the bacterial Gram-negative genusAeromonas; the capacity of other bacteria to use the complex was not tested. The physiological function of the catfish heme-binding serum protein is presently not clear.