Photosynthesis and apparent affinity for dissolved inorganic carbon by cells and chloroplasts of Chlamydomonas reinhardtii grown at high and low CO2 concentrations

Chloroplasts with high rates of photosynthetic O₂ evolution (up to 120 mol O₂· (mg Chl)^-1·h^-1 compared with 130 mol O₂· (mg Chl)^-1·h^-1 of whole cells) were isolated from Chlamydomonas reinhardtii cells grown in high and low CO₂ concentrations using autolysine-digitonin treatment. At 25° C and pH=7.8, no O₂ uptake could be observed in the dark by high- and low-CO₂ adapted chloroplasts. Light saturation of photosynthetic net oxygen evolution was reached at 800 mol photons·m^-2·s^-1 for high- and low-CO₂ adapted chloroplasts, a value which was almost identical to that observed for whole cells. Dissolved inorganic carbon (DIC) saturation of photosynthesis was reached between 200–300 M for low-CO₂ adapted chloroplasts, whereas high-CO₂ adapted chloroplasts were not saturated even at 700 M DIC. The concentrations of DIC required to reach half-saturated rates of net O₂ evolution (K_m(DIC)) was 31.1 and 156 M DIC for low- and high-CO₂ adapted chloroplasts, respectively. These results demonstrate that the CO₂ concentration provided during growth influenced the photosynthetic characteristics at the whole cell as well as at the chloroplast level.Abbreviations Chl chlorophyll - DIC dissolved inorganic carbon - K_m(DIC) coneentration of dissolved inorganic carbon required for the rate of half maximal net O₂ evolution - PFR photon fluence rate - SPGM silicasol-PVP-gradient medium     

Interaction of gravi- and phototropic stimulation in the response of maize (Zea mays L.) coleoptiles

The influence of gravitropic stimulation upon blue-light-induced first positive phototropism for stimulations in the same (light source and center of gravity opposite to each other) and in opposing directions was investigated in maize cole-optiles by measuring fluence-response patterns. As a result of gravitropic counterstimulation, phototropic bending was transient with maximum curvature occurring 100 min after stimulation. On a horizontal clinostat, however, the seedlings curved for 20 h. Gravistimulation in the opposite direction acted additively upon blue-light curvature. Gravistimulation in the same direction as phototropic stimulation produced a complex behaviour deviating from simple additivity. This pattern can be explained by a gravitropically mediated sensitization of the phototropic reaction, an optimal dependence of differential growth on the sum of photo-and gravistimulation, and blue-light-induced inhibition of gravitropic curvature at high fluences. These findings indicate that several steps of photo-and gravitransduction are separate. Preirradiation with red light desensitized the system independently of applied gravity-treatment, indicating that the site of red-light interaction is common to both transduction chains.Abbreviations BL blue light - G⁺ stimulation by light and gravity in the same direction (i.e. light source and center of gravity opposite to each other) - G^- stimulation by light and gravity in opposing directions     

Initiation of morphogenic cell-suspension and protoplast cultures of barley (Hordeum vulgare L.)

Cell-suspension cultures were initiated from embryogenic calli of various barley cultivars. Seven fast-growing suspension lines were obtained from four different cultivars (cvs. Dissa, Emir, Golden Promise and Igri). Two of these cell suspensions showed morphogenic capacity. From a cell suspension of cv. Dissa, albino plantlets were regenerated when aggregates were cultured on solid medium. Aggregates of cv. Igri usually stopped differentiation at the globular stage, but occasionally formed scutellum-like structures. Five suspension lines were used for protoplast isolation and culture. Dividing protoplasts were obtained from all lines, but with cv. Igri a few divisions only and no further development were observed. Protoplasts from the various lines differed in the time of first division (2–14 d), division frequency (0.09–70.9%) and efficiency of colony formation (0.09–7.3%). Protoplasts isolated from the morphogenic cell suspension of cv. Dissa developed compact calli which sporadically regenerated albino plantlets.Abbreviations CC, MS, N6, SH, Kao8p culture media; see Material and methods - cv chltivar - dicamba 3,6-dichloro-o-anisic acid - 2,4-D 2,4-dichlorophenoxyacetic acid - picloram 4-amino-3,5,6-trichloropicolinic acid     

Cardiovascular and Pulmonary Effects of a New Sedative/Analgesic (Medetomidine) as a Preanaesthetic Drug in the Dog

Cardiovascular and pulmonary effects of a new sedative/analgesic (medetomidine) as a preanaesthetic drug in the dog. A study was carried out to investigate the possible usefulness of medetomidine (Farmos Group, Turku, Finland) for premedication prior to general anaesthesia with thiopental sodium and halothane. The main emphasis was laid on the circulatory and respiratory effects of medetomidine. Dogs treated with xylazine (2 mg/kg) or placebo (physiological saline solution) served as controls. Medetomidine caused a decrease in blood pressure, heart rate and respiratory rate at all dose levels tested. These decreases were essentially dose -dependent, but there were great individual variations. It is concluded that the drug can be useful for premedication at the lowest dose level tested (10 μ/kg). The sedative effect, however, is so strong that an even lower dose might be sufficient for the present purpose.     

v-myc alters the response of a cloned mouse mammary epithelial cell line to lactogenic hormones

Several oncogenes have now been implicated in mammary carcinogenesis. We investigated the phenotypic effects of expressing three representative oncogenes in mammary epithelial cells. v-myc (coding for a nuclear protein), v-Ha-ras (a G-protein homologue) and v-fgr (a tyrosine kinase) genes were introduced into the nontumorigenic clone 14 of the mouse mammary epithelial cell line COMMA-1D. Their effects upon growth and differentiation were determined. Anchorage-independent growth was induced by all three oncogenes with low efficiency. v-Ha-ras and v-fgr induced tumorigenicity in nude mice. The effect of oncogenes upon parameters unique to mammary epithelial cells in vitro was assayed. Both v-myc and v-fgr abolished the ability of clone 14 to grow as three-dimensional branching structures in hydrated collagen gel. v-fgr completely and v-myc partially inhibited the expression of the epithelium specific cytokeratins. Clone 14 can be induced to produce the beta-casein milk protein by the combination of the lactogenic hormones, dexamethasone, insulin, and PRL. Introduction of v-myc into clone 14 cells resulted in an estimated 50-fold increased induction of beta-casein protein and at least a 60-fold increase in beta-casein mRNA. The number of cells stained with anti-beta casein antibodies also showed a 10-fold increase after v-myc introduction. This still required the synergistic action of all three lactogenic hormones. Thus v-myc can alter the normal response of mammary epithelial cells to lactogenic hormones.     

Microbeam analysis of Ca exchange and uptake in the fine roots of spruce: influence of pH and aluminum

Summary A novel stable isotope labelling procedure for microbeam analysis was developed to monitor exchange and uptake of nutrients, primarily Mg, K and Ca, by root tips at the cellular level. Initially root samples were analysed from 2-year-old spruce trees, originating both from a nursery and from a polluted forest site, (1) for the cortex cell wall accessibility and nutrient binding properties, (2) for the influence of low pH and elevated aluminum concentrations on Ca binding to cortex cell walls, and (3) for long-range transport into the secondary xylem, proximal to the labelled root tip. In nursery control plants, Ca is localized mainly in the apoplast of the cortex. Exchange of Mg, K, Ca in the cell wall of the cortex and the primary xylem with label in incubation solutions is almost completed to equilibration within 30 min. In the secondary xylem we could detect Mg, K, and Ca from labelling solutions in minute amounts after 30 min, and as a major fraction after 48 h. This indicates that stable isotope labelling can be used to study both ion-exchange properties of the apoplast and long-range transport. Slight acidification of the labelling incubation media to pH 4.5 reduced Ca binding to the cortex cell walls slightly, but acidification to the extreme value of pH 2.3 reduced binding 41%. A combination of pH 4.5 and increased free aluminum reduced the binding by 83%. In a preliminary attempt to analyse the nutrient binding capability of the root-tip apoplast from pollution affected trees, we exposed fine roots of 2-year-old spruce from an acidified and polluted site showing typical low levels of Ca and Mg in the cortical cell walls to Ca-enriched media. Under these conditions the Ca content of cortex cell walls doubled upon incubation at pH 4.7, reaching 40% of the total binding capacity of our nursey control plants.     

Light-microscopic histochemistry of non-specific alkaline phosphatase using lanthanide-citrate complexes

Summary New lanthanide methods for the histochemical detection of non-specific alkaline phosphatase in the light microscope are described and compared with already existing techniques for the light microscopical demonstration of this enzyme. To avoid formation of insoluble lanthanide hydroxide at alkaline pH citrate complexes with the capture ions cerium, lanthanum and didymium were used. A molar ratio of 11 mM citrate/14 mM capture reagent is proposed. For preincubated sections, pretreatment in chloroform-acetone and fixation in glutaraldehyde, for non-preincubated sections fixation in glutaraldehyde yielded the best results. 4-Methylumbelliferyl and 5-Br-4-Cl-3-indoxyl phosphate were found to be the most suitable substrates. For routine purposes 4-nitrophenyl, 1-naphthyl, 2-naphthyl and 2-glycerophosphate were also sufficient; naphthol AS phosphates were inferior but still suitable. After incubation for 5–60 min at 37° C lanthanide phosphate was converted into lead phosphate which was visualized as lead sulfide. At pH 9.2–9.5 enzyme activity was demonstrated at many sites such as intestinal, uterine, placental, renal and epididymal microvillous zones, plasma membranes of arterial, sinus and capillary endothelial cells, vaginal and urethral epithelium, smooth muscle cells, myoepithelial cells as well as excretory duct cells of salivary and lacrimal glands and in secretory granules of laryngeal glands. In comparison with Gomori's calcium, Mayahara's lead, Burstone's and Pearse's azo-coupling, McGadey's tetrazolium salt and Gossrau's azoindoxyl coupling technique the lanthanide methods detected alkaline phosphatase activities at identical or additional sites depending on the respective procedure. However, in contrast to the other methods especially the cerium citrate procedure yielded a more precisely localized and more stable reaction product, can be used with all available alkaline phosphatase substrates including those up till now less suitable or unsuitable for light microscopic alkaline phosphatase histochemistry.     

Primary structure of the hemoglobin α-chain of rose-ringed parakeet (Psittacula krameri)

The structure of the hernoglobin α-chain of Rose-ringed Parakeet was determined by sequence degradations of the intact subunit, the CNBr fragments, and peptides obtained by digestion with staphylococcal Glu-specific protease and trypsin. Using this analysis, the complete α-chain structure of 21 avian species is known, permitting comparisons of the protein structure and of avian relationships. The structure exhibits differences from previously established avian α-chains at a total of 61 positions, five of which have residues unique to those of the parakeet (Ser-12, Gly-65, Ser-67, Ala-121, and Leu-134). The analysis defines hemoglobin variation within an additional avian order (Psittaciformes), demonstrates distant patterns for evaluation of relationships within other avian orders, and lends support to taxonomic conclusions from molecular data.