Nonphotosynthetic CO(2) Fixation by Alfalfa (Medicago sativa L.) Roots and Nodules

The dependence of alfalfa (Medicago sativa L.) root and nodule nonphotosynthetic CO₂ fixation on the supply of currently produced photosynthate and nodule nitrogenase activity was examined at various times after phloem-girdling and exposure of nodules to Ar:O₂. Phloemgirdling was effected 20 hours and exposure to Ar:O₂ was effected 2 to 3 hours before initiation of experiments. Nodule and root CO₂ fixation rates of phloem-girdled plants were reduced to 38 and 50%, respectively, of those of control plants. Exposure to Ar:O₂ decreased nodule CO₂ fixation rates to 45%, respiration rates to 55%, and nitrogenase activities to 51% of those of the controls. The products of nodule CO₂ fixation were exported through the xylem to the shoot mainly as amino acids within 30 to 60 minutes after exposure to ¹⁴CO₂. In contrast to nodules, roots exported very little radioactivity, and most of the ¹⁴C was exported as organic acids. The nonphotosynthetic CO₂ fixation rate of roots and nodules averaged 26% of the gross respiration rate, i.e. the sum of net respiration and nonphotosynthetic CO₂ assimilation. Nodules fixed CO₂ at a rate 5.6 times that of roots, but since nodules comprised a small portion of root system mass, roots accounted for 76% of the nodulated root system CO₂ fixation. The results of this study showed that exposure of nodules to Ar:O₂ reduced nodule-specific respiration and nitrogenase activity by similar amounts, and that phloem-girdling significantly reduced nodule CO₂ fixation, nitrogenase activity, nodule-specific respiration, and transport of ¹⁴C photoassimilate to nodules. These results indicate that nodule CO₂ fixation in alfalfa is associated with N assimilation.     

Changing Activity of Glucose-6-Phosphate Dehydrogenase from Pea Chloroplasts during Photosynthetic Induction

Light inactivation of glucose 6-phosphate dehydrogenase is rapid and occurs before photosynthetic O₂ evolution is measureable in intact chloroplasts. Likewise, dark activation is rapid. The major light induced change in the kinetic parameters of glucose 6-phosphate dehydrogenase is in maximal velocity.     

Expression of the β-subunit of β-conglycinin in seeds of transgenic plants

Soybean (Glycine max (L.) Merr.) seeds contain the storage protein -conglycinin, encoded by a multigene family. -Conglycinin consists of three subunits; , , and . A genomic clone for a -subunit of -conglycinin has been characterized by restriction-enzyme mapping and hybrid selected in-vitro translation followed by immunoprecipitation. In order to determine the developmental regulation of this -subunit gene, its expression was studied in seeds of transgenic petunia (Petunia hybrida) and tobacco (Nicotiana tabacum L.) plants. The -subunit expressed in seeds of petunia and tobacco was recognized by anti--conglycinin serum at a relative molecular mass of 53 000, equivalent to that of the native protein. Separation of the petunia-seed proteins by isoelectric focusing followed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and immunoblot analysis showed that multiple isoelectric forms of the -subunit were produced. There was approximately a twofold variation in the accumulation of the -subunit protein in the mature seeds of transgenic petunia plants, each containing a single -subunit gene. However, the level of protein accumulation in mature seeds and the amount of -subunit mRNA in developing seeds was not correlated. Accumulation of the -subunit protein in transgenic seeds was less than the -subunit protein that accumulated in transgenic petunia seeds containing a single -subunit gene and less than the amount of the -subunit in mature soybean seeds which contain 8–13 -subunit genes. In transgenic tobacco plants, the accumulation of the -subunit protein in seeds was generally well correlated with the number of genes that were incorporated in the different transformants.Abbreviations kb kilobase - kDa kilodalton - M_r relative molecular mass - SDS-PAGE sodium dodecyl sulfate polyacrylamide gel electrophoresis     

Growth potential in onlay bone grafts: a comparison of vascularized and free calvarial bone and suture bone grafts

Vascularized bone grafts are characterized by a viable cell population with osteogenic potential. These features suggest that continued growth can be anticipated following vascularized membranous bone transfer in a growing craniofacial skeleton. The present paper compares the potential for appositional bone growth in vascularized and free calvarial onlay bone grafts. In seven 8-week-old beagles, growth was assessed by direct caliper measurements of graft dimensions intraoperatively and 16 weeks postoperatively. Vascularized grafts demonstrated a 50 to 60 percent increase in size in all dimensions compared to 10 to 20 percent growth in free grafts (p less than 0.01). Microradiography revealed preservation of calvarial bony architecture and minimal resorption in vascularized grafts, while triple-fluorochrome labeling confirmed subperiosteal appositional bone formation. Free grafts were characterized by significant resorption and a delay in subperiosteal bone formation.     

Reversible effects of moderately elevated temperature on the distribution of excitation energy between the two photosystems of photosynthesis in intact avocado leaves

Initial (F_o), maximum (F_m) and steady-state (F_s) levels of modulated chlorophyll fluorescence were measured in intact avocado leaves (Persea americana Mill.) during state 1-state 2 transitions using a combination of modulated and non-modulated lights with synchronized detection. Under normal temperature conditions (20°C), transition from state 2 to state 1 was associated with a substantial increase (about 20%) in F_m and F_o whereas the F_m/F_o ratio remained constant, reflecting increased absorption cross-section of PS II. On the contrary, at moderately elevated temperature (35°C), these fluorescence changes were very limited, indicating marked inhibition of the state regulation. The fraction of light distributed to PS II () was calculated from the F_o, F_m and F_s levels for both types of leaves. In control leaves, varied from 48% (in state 2) to values as high as 58% (in state 1). In contrast, mild heat treatment resulted in values close to 50% in both states, indicating the inability of heated leaves to reach extreme state 1. The results suggested that avocado leaves under moderately elevated temperature conditions are blocked in a state close to state 2. This effect was shown to occur in a non-injurious temperature range (as shown by the preservation of the (photoacoustically monitored) oxygen evolution activity) and to be rapidly reversed upon lowering of the temperature. Thermally induced development of state 2 (independent on the light spectral quality) could possibly be a protective mechanism to avoid photodamage of the heat-labile PS II by high light intensities which usually accompany heat stress in the field.     

Plasma cell granuloma of the tongue. Report of a case

A case of plasma cell granuloma of the tongue in an otherwise symptomless 48-year-old caucasian female is reported. The polyclonal nature of the plasmocytes was revealed by immunostaining of kappa and lambda light chains. Electron microscopic observations showed typical mature plasmocytes. A parasitic etiology of this type of lesion is suggested.     

The relative toxicity of a spore preparation of Bacillus thuringiensis var. israelensis against fourth instar larvae of Aedes aegypti and Toxorhynchites amboinensis: suspension feeding compared with enemas and forced feeding

The toxic effect of a spore preparation of Bacillus thuringiensis var. israelensis Berliner Serotype H-14 (Bti) on 4th instar larvae of Aedes aegypti L. and Toxorhynchites amboinensis (Doleschall) was observed when given either in a suspension feeding test or when injected orally as a forced feeding or via the anus as an enema. The A. aegypti larvae showed the greater sensitivity to Bti both because they greatly concentrate the toxin by filter feeding and they are more sensitive to Bti than are the larvae of T. amboinensis. The latter appeared approximately two-fold less sensitive to Bti than the former after taking into account their greater body weight.

---

Résumé La toxicité sur des larves de 4ème stade de A. aegypti et T. amboinensis, d'une préparation de spores de B. thuringiensis var. israelensis Berliner sérotype H-14, a été examinée après: injection orale par alimentation forcée, injection anale comme lavement, — le témoin étant une alimentation à partir d'une suspension de spores.Les larves de A. aegypti ont présenté la plus grande sensibilité au Bti d'une part parce qu'elles concentrent beaucoup la toxine avec leur alimentation par filtration, et parce qu'elles sont plus sensibles sensu stricto au Bti. Même en tenant compte de leur poids plus élevé, T. amboinensis est apparu comme deux fois moins sensible au Bti.

     

Susceptibility of protein kinase C to oxidative inactivation: loss of both phosphotransferase activity and phorbol diester binding

Exposure of protein kinase C to low concentrations of either N-chlorosuccinimide or H2O2 resulted in rapid and parallel loss of phosphotransferase activity and phorbol ester binding. This oxidative inactivation of protein kinase C also occurred in intact cells exposed to a low concentration of H2O2. With H2O2 treatment the rate of inactivation of protein kinase C in the cytosol of MCF-7 cells was rather slower than that which occurred in the cytosol of PYS cells. However, in both cell types, the oxidative inactivation of membrane-associated protein kinase C occurred rapidly in comparison to the enzyme in the cytosol. Prior treatment of cells with phorbol ester to induce membrane association (stabilization) of protein kinase C, followed by exposure to H2O2, resulted in increased inactivation of protein kinase C, suggesting that membrane association of protein kinase C increases its susceptibility to oxidative inactivation.     

Sequence analysis of the 17-kilodalton-antigen gene from Rickettsia rickettsii.

DNA obtained from the Sheila Smith strain of Rickettsia rickettsii was digested to completion with the restriction endonucleases BamHI and SalI and ligated with the plasmid vector pUC19. The ligation mixture was used to transform Escherichia coli. A total of 465 bacterial clones were screened for antigen production with hyperimmune rabbit serum. One of the reactive clones, containing a recombinant plasmid designated pSS124, was solubilized and subjected to immunoblot analysis and revealed expression of a 17-kilodalton protein reactive with anti-R. rickettsii serum that comigrated with an antigen from R. rickettsii. A 1.6-kilobase PstI-BamHI fragment from pSS124 was subcloned and continued to direct synthesis of the 17-kilodalton antigen. The nucleotide sequence was determined for this 1.6-kilobase subclone, which encompassed the gene encoding the polypeptide as well as flanking regions containing potential regulatory sequences. The open reading frame consisted of 477 nucleotides that specified a 159-amino-acid protein with a calculated molecular weight of 16,840. The deduced amino acid sequence contained a hydrophobic sequence near the amino terminus that resembled signal peptides described for E. coli. The carboxy terminus was hydrophilic in nature and probably contained the exposed epitopes.     

Chemical modification and labeling of glutamate residues at the stilbenedisulfonate site of human red blood cell band 3 protein

A new method has been developed for the chemical modification and labeling of carboxyl groups in proteins. Carboxyl groups are activated with Woodward's reagent K (N-ethyl-5-phenylisoxazolium 3'-sulfonate), and the adducts are reduced with [3H]BH4. The method has been applied to the anion transport protein of the human red blood cell (band 3). Woodward's reagent K is a reasonably potent inhibitor of band 3-mediated anion transport; a 5-min exposure of intact cells to 2 mM reagent at pH 6.5 produces 80% inhibition of transport. The inhibition is a consequence of modification of residues that can be protected by 4,4'-dinitrostilbene-2,2'-disulfonate. Treatment of intact cells with Woodward's reagent K followed by B3H4 causes extensive labeling of band 3, with minimal labeling of intracellular proteins such as spectrin. Proteolytic digestion of the labeled protein reveals that both the 60- and the 35-kDa chymotryptic fragments are labeled and that the labeling of each is inhibitable by stilbenedisulfonate. If the reduction is performed at neutral pH the major labeled product is the primary alcohol corresponding to the original carboxylic acid. Liquid chromatography of acid hydrolysates of labeled affinity-purified band 3 shows that glutamate but not aspartate residues have been converted into the hydroxyl derivative. This is the first demonstration of the conversion of a glutamate carboxyl group to an alcohol in a protein. The labeling experiments reveal that there are two glutamate residues that are sufficiently close to the stilbenedisulfonate site for their labeling to be blocked by 4,4'-diisothiocyanodihydrostilbene-2,2'-disulfonate and 4,4'-dinitrostilbene-2,2'-disulfonate.