Search

Background: The precise mechanism of action of theophylline in asthma is not fully understood but recent data have drawn attention to its potential anti-inflammatory effect., Objective: The purpose of this study was to assess the effect of theophylline on sputum eosinophilia and sputum eosinophil chemotactic activity in steroid-naive asthmatics., Method: We performed a 4-week randomized double-blind, placebo-controlled, parallel group study in 21 mild to moderate steroid-naive asthmatics whose sputum eosinophilia was found twice > 5% during the run in period. Eleven subjects received 600 mg/24 h theophylline for the first 2 weeks and 900 mg/24 h for the last 2 weeks while 10 subjects took a placebo for 4 weeks. Sputum was induced after 2 and 4 weeks of treatment and 1 week after stopping the treatment. The sputum samples were compared for their cell counts, eosinophil cationic protein (ECP) levels and eosinophil chemotactic activity using micro-Boyden chambers., Results: Serum theophylline concentrations reached 7 and 11 microg/mL at V3 and V4, respectively. Intragroup comparisons showed that theophylline, but not placebo, caused a significant reduction in sputum eosinophil counts at V3 (62 +/- 10% from baseline, P < 0.01) and a strong trend at V4 (67 +/- 16% from baseline, P = 0.07) when compared to baseline. The intergroup difference obtained after comparing the area under the curve over the 4 week treatment period only approached the statistical significance (P = 0.08). At baseline the fluid phase of the sputum contained a significant eosinophil chemotactic activity which was inhibited after a 4-week treatment by theophylline (P < 0. 01) but not by placebo. The mean sputum theophylline levels after 4 weeks of treament (1.7 microg/mL) was lower than that required to cause significant inhibition of eosinophil chemotaxis in vitro., Conclusion: Theophylline decreases the natural sputum eosinophil chemotactic activity present in asthmatics. However, when using a small sample size, the 35% reduction in sputum eosinophilia achieved by theophylline failed to reach statistical significance when compared to that seen after placebo.

Asthma is an inflammatory disease of the airways clinically characterised by recurrent bronchial obstructions at least partially reversible. Recent epidemiologic data suggest that asthmatics have an increased rate of decrease of their expiratory volumes during life. This irreversible lung function impairment is associated with fundamental structural changes of the bronchial wall in terms of conjunctive tissue and smooth muscle composition. We describe these changes and explore the different mechanisms proposed to explain these structural modifications. We also review their consequences in terms of bronchial physiology and their potential influence on bronchial hyperresponsiveness.

Unlabelled: H. pylori infection is putatively associated with extra-digestive disorders and may also play a role in the development of autoimmune thyroid diseases (ATD). It was recently found that monoclonal antibodies to an H. pylori strain with cagA-positivity reacted with follicular cells of the thyroid gland, and that an H. pylori organism possessing the cag pathogenicity island carried a gene encoding for an endogenous peroxidase. The aims of this study was (1); To ascertain whether the infection by strains endowed with an increased inflammatory potential (those expressing CagA) could further enhance the risk of developing ATD (2); To verify the possible existence of an immune cross-reactivity between autoantibodies to peroxidase and thyroglobulin and H. pylori antigens (3). To establish whether thyroid colloid antigens could cross-react with an anti-H. pylori serum. The study was partly designed retrospectively. We examined 41 consecutive women with ATD, and, as a control, 33 consecutive age- and socio-economic class-matched women without autoimmune thyroid disorders, living in the same area as patients, occurred at the same institution in the same period (six months). Both patients and controls were examined serologically for H. pylori infection and CagA status by Western blotting. Some serum samples were absorbed with H. pylori to determine whether the antibody levels decreased. Colloid proteins were resolved electrophoretically and matched with a hyperimmune serum raised in rabbits against a CagA-positive H. pylori. Thirty-two patients (78.0%) tested seropositive for H. pylori infection, vs. 16 controls (48.4%) (P = 0.008, OR = 3.78, RR = 1.61). The prevalence of anti-CagA antibodies was 71.8% in infected patients, and 50% in infected controls (P = 0.161, n.s.). The overall prevalence of infection by CagA-positive H. pylori was significantly higher in patients with ATD (23/41, or 56.0%) than that in controls (8/33, or 24.2%) (P = 0.006, OR = 3.99, RR = 2.31). The other tests gave negative or inexplicable results., In Conclusion: CagA-positive H. pylori infection increases the risk of ATD development.

Background: Tryptase is a serine endoprotease selectively released from mast cells. Although mast cells are known to be activated after experimental allergic provocation, their role in naturally occurring asthma is still debated., Methods: We have investigated the levels of tryptase in the whole induced sputum collected from 51 asthmatics (31 atopic and 20 intrinsic) seen in our outpatient clinic and 22 normal nonatopic healthy volunteers. Tryptase was measured by a new immunoassay based on B12 monoclonal antibody recognition of total tryptase (UniCAP System, Pharmacia) with a sensitivity of 1 ng/ml., Results: While being below the threshold of detection in all normal volunteers, tryptase was detectable in the sputum from 9/51 asthmatics (18%) including five atopic and four intrinsic asthma cases. In these patients, among whom three were asymptomatic asthmatics, the values ranged between 1 and 6.1 ng/ml. The asthmatics with detectable sputum tryptase had greater sputum eosinophil counts (P<0.05) but lower neutrophil counts (P<0.05) than those in whom tryptase was undetectable. When compared to control subjects, asthmatics without tryptase had still greater eosinophil counts (P<0.0001) but also raised neutrophil counts (P<0.05). No significant difference could be found between asthmatics with tryptase and those without tryptase with respect to the age, the baseline lung function, the methacholine bronchial responsiveness, and the frequency of treatment with inhaled steroids., Conclusions: With the UniCAP System, tryptase was detectable in the sputum from 18% of asthmatics irrespective of atopy and current symptoms. Asthmatics with tryptase appeared to have a selective increase in sputum eosinophil counts while those without tryptase displayed a mixed sputum granulocyte infiltration with raised eosinophil and neutrophil counts.

A routine chart review over 23 months in a 256-bed community hospital revealed 246 medical records contaminated with apparent blood. Sixty percent of the records were nursing and anesthesiology records. Analysis of systematically selected records confirmed blood as the visible contaminant in 27% of the cases (8/30). Total quality improvement methodology reduced the incidents by 75%. Actions included policy development, in-service education, and changes in work practices. Although bloodborne pathogen transmission is statistically improbable, we should improve work practices to eliminate blood contamination of charts.

A 83 years old patient was admitted with a complex clinical picture including cutaneous rash, muscular pain, rhabdomyolysis and renal failure. The clinical picture suggests a dermatopolymyositis. Despite of high dose corticotherapy, the patient died on day 22. The anatomical examination shows a cholangiocarcinoma disseminated locally as well as in the lungs and bones.

Tumor cell extravasation is a determinant step in the process of hematogenous metastasis. The signal transduction pathways involved in the interactions between tumor cells and the vascular endothelium during transendothelial migration are still undefined. In the present study, we have investigated the influence of human breast adenocarcinoma cells (MCF7) on human umbilical vein endothelial cell (HUVEC) intracellular Ca2+ concentration ([Ca2+]i). We show that the contact between MCF7 cells and a confluent HUVEC monolayer induces an immediate and transient increase in HUVEC [Ca2+]i. This [Ca2+]i rise could not be elicited by tumor cell-conditioned medium, isolated tumor cell membranes, inert beads or normal breast epithelial cells, demonstrating the involvement of specific recognition mechanisms between MCF7 cells and HUVEC. Depletion of HUVEC intracellular Ca2+ stores by the endoplasmic reticulum Ca2+-ATPase inhibitor thapsigargin as well as the selective depletion of inositol 1,4,5-triphosphate (IP3)-sensitive Ca2+ stores by prior activation of HUVEC using histamine resulted in a complete inhibition of tumor cell-induced [Ca2+]i elevation. Similar results were obtained when HUVEC monolayers were treated with the tyrosine kinase inhibitor herbimycin A, suggesting a role for tyrosine kinase-associated cell surface receptors in tumor cell-endothelial cell interactions. The depletion of HUVEC intracellular Ca2+ stores by thapsigargin was also shown to delay MCF7-induced endothelial cell disjunction, to prevent their spreading on the subendothelial extracellular matrix and transendothelial migration in vitro. These results suggest that transient changes in endothelial [Ca2+]i may govern multiple steps of tumor cell extravasation.

The immunogenicity and protective efficacy of influenza vaccine with and without the adjuvant MF59 was determined in mice. The addition of MF59 significantly increased the antibody response to the vaccine antigens over a wide dose range. Equivalent antibody titres were seen using 50- to 200-fold lower antigen concentrations when combined with MF59 compared with vaccine alone. The humoral response was sustained for at least 6 months after immunization. The addition of MF59 increased the protective efficacy of the vaccine: the amount of live virus detectable in the lungs of mice challenged with virus 1-6 months after immunization was reduced and the rate of survival was significantly increased. Influenza vaccine combined with MF59 gave full protection from viral challenge at antigen doses 65- to 80-fold lower than with vaccine alone.

Thrombospondin is an adhesive glycoprotein that promotes breast cancer cell adhesion to human vascular endothelial cells (Incardona et al., 1995). In this study, we have identified the molecular domains of thrombospondin that mediate its binding to specific receptors on the human breast adenocarcinoma cell line, MDA-MB-231. Two recombinant fragments from the amino-terminus (TSPN18 and TSPN28), and the fusion proteins of the type 1 and type 2 repeats of human thrombospondin, inhibited binding of radiolabeled thrombospondin to MDA-MB-231 cells in suspension by 40-60% at 50 micrograms/ml whereas the type 3 repeat, carboxy-terminus and unfused glutathione-S-transferase as well as the synthetic peptide Gly-Arg-Gly-Asp-Ser (500 micrograms/ml) had little or no effect. Heparin and various glycosaminoglycans as heparan sulfate, chondroitin sulfates A, B or C, and fucoidan inhibited thrombospondin binding to MDA-MB-231 cells by more than 60% whereas dextran sulfate had only little effect. Treatment of cells with heparitinase, chondroitinase ABC, and hyaluronidase, but not with neuraminidase, induced 30-50% inhibition of thrombospondin binding suggesting the participation of both heparan sulfate and chondroitin sulfate cell surface-associated molecules. Inhibition of proteoglycan sulfation by chlorate or inhibition of glycosaminoglycan chain formation by two beta-D-xylosides also led to a substantial inhibition of thrombospondin binding. Our results indicate that several domains within the thrombospondin molecule, namely the amino-terminus, type 1 and type 2 repeats, participate in its binding to specific receptors bearing sulfated glycosaminoglycans on MDA-MB-231 cells. Biological assays have indicated that, in addition to these domains, the peptide Gly-Arg-Gly-Asp-Ser inhibited MDA-MB-231 cell attachment to thrombospondin suggesting that the last type 3 repeat of the molecule may also contribute to its cell adhesive activity.

The initiation of the angiogenic process requires a locally confined and time-limited proteolysis of the basement membrane (BM) components at the site of new vessel sprout. Gelatinase A, a member of the matrix metalloproteinase family, degrades BM type IV collagen and is involved in the BM breakdown by migrating tumor cells and endothelial cells (EC). Gelatinase A is synthesized as latent proenzyme and must be activated in order to express its proteolytic activity. A plasma membrane-dependent mechanism of activation has been described for several tumor and transformed cells lines. In the present study, we show that latent (72 kD) and mature (62-59 kD) forms of gelatinase A are present in EC membrane fraction from Triton X-114 extract while only latent form is found in the cytosolic fraction. The incubation of EC membrane fraction with exogenous latent gelatinase A resulted in a significant activation giving rise to 62-59 kD mature forms. 12-O-tetradecanoylphorbol-13-acetate (TPA), a strong potentiator of angiogenesis in vitro and in vivo, increases the amount of both latent and activated forms of gelatinase A in EC membrane fraction as well as the ability of this latter fraction to activate exogenous latent gelatinase A. We show that the mRNA transcript coding for the membrane-integrated MMP, the MT-MMP, previously described as a potential gelatinase A activator in invasive tumor cells is also expressed in vascular EC and is regulated through a TPA sensitive process. This enzyme may be responsible for membrane-dependent gelatinase A activation in normal vascular EC and may therefore be a determinant in the control of BM proteolysis during angiogenesis.

Recombinant glycoprotein B (gB) of herpes simplex virus (HSV) was processed and presented by class I major histocompatibility complex (MHC) molecules after delivery into cells by using N-[1-(2,3-dioleoyloxy)propyl]-N,N,N-trimethylammonium methyl sulfate (DOTAP), a commercially available cationic lipid used for DNA transfection. Cells treated with DOTAP-associated gB were susceptible to lysis by class I MHC-restricted, HSV-specific cytotoxic T lymphocytes (CTL), and the treated cells restimulated memory gB-specific CTL activity in spleen cells from HSV-infected mice. gB-specific CTL responses were detected in mice immunized with recombinant gB and DOTAP but not in those receiving gB emulsified in complete Freund's adjuvant. Thus, cationic lipids may facilitate induction of CD8+ T-cell responses in vaccinations with recombinant antigens, and they may serve as readily available reagents for dissecting class I MHC immunity to viruses and other intracellular pathogens.

A chronic feeding study using 95mTc incorporated into alfalfa and an acute study where 95mTc was amended to alfalfa showed that about 8.4% of ingested Tc was transferred to eggs. After 10 days of chronic feeding, 80% of the Tc was in yolk, 20% in albumin and less than 1% in shell and associated membranes. At necropsy, technetium concentrations in the three largest oocytes were nearly equal. The biological half-time for Tc was about one to two days in acute studies. Results from the chronic feeding study also indicated that Tc levels in albumin reach a maximum between three and five days while maximum yolk concentration is attained in about six to seven days. Albumin concentrations declined about 20-50% after Day 6.

Indole-3-acetic acid (IAA) is transported from a nearly mature leaf throughout an intact Coleus blumei Benth. plant in the phloem. A buffered solution of both (14)C-methylene-labeled indoleacetic acid ([(14)C]IAA) and [6-(3)H]glucose was supplied in a glass capillary to the distal end of a severed main lateral vein of the leaf. Both labeled sugar and auxin move rapidly through the plant at velocities of ca. 16-20 cm h(-1) with closely similar, exponential profiles. This translocation is nonpolar; both auxin and sugar move upwards to the apex and young expanding leaves as well as downwards to the base of the shoot. Neither tracer appears in mature leaves; this eliminates the possibility that they enter the xylem. At the end of the transport period, 80-90% of the radioactivity recovered from various portions of the plants supplied with [(14)C]IAA is still identical chromatographically with IAA. In microautoradiographs prepared by techniques that minimize loss and redistribution of soluble compounds, radioactivity from [(3)H]IAA is concentrated in the phloem of the midrib and petiole of the fed leaf. A ring of triiodobenzoic acid (TIBA) strongly inhibits the polar auxin transport in sections isolated from the ringed region but does not significantly affect auxin translocation in the phloem of intact plants. TIBA does, however, reduce the entry of auxin into the collecting veins of the leaf. Thus steps in auxin transport sensitive to TIBA may occur during transfer through the leaf or into the phloem, but not during long distance translocation in the phloem.

The gross tissue distribution, intracellular fate, and chemical behavior of Ni(2+) in soybean plants (Glycine max cv. Williams) were investigated. Following root absorption, Ni was highly mobile in the plant, with leaves being the major sink in the shoots for Ni during vegetative growth. A senescence >70% of the Ni present in the shoot was remobilized to seeds. Fractionation of root and leaf tissues showed >90% of the Ni to be associated with the soluble fraction of tissues; ultrafiltration of the solubles showed >77% of the Ni to be associated with the 10,000 to 500 molecular weight components of both roots and leaves. Chemical characterization of the soluble components (10,000 to 500 and >500 molecular weight) by thin layer chromatography and electrophoresis resolved a number of Ni-containing organic complexes. Major Ni-containing components formed in the root are transported in the xylem stream, and undergo partial modification on deposition in leaves. Nickel accumulated in seeds is primarily associated with the cotyledons. Chemical fractionation of cotyledon components showed 80% of the Ni to be associated with the soluble whey fraction, while 70% of this fraction was composed of Ni-containing components with molecular weight <10,000.

The in vitro instability of nitrate reductase (EC 1.6.6.1) activity from leaves of several species of higher plants was investigated. Decay of activity was exponential with time, suggesting that an enzyme-catalyzed reaction was involved. The rate of decay of nitrate reductase activity increased as leaf age increased in all species studied. Activity was relatively stable in certain genotypes of Zea mays L., but extremely unstable in others. In all genotypes of Avena sativa L. and Nicotiana tabacum L. studied, nitrate reductase was unstable. Addition of 3% (w/v) bovine serum albumin or casein to extraction media prevented or retarded the decay of nitrate reductase activity for several hours. In addition, the presence of bovine serum albumin or casein in the enzyme homogenate markedly increased nitrate reductase activity (up to 15-fold), especially in older leaf tissue.

The use of plants to monitor heavy metal pollution in the terrestrial environment must be based on a cognizance of the complicated, integrated effects of pollutant source and soil-plant variables. To be detectable in plants, pollutant sources must significantly increase the plant available metal concentration in soil. The major factor governing metal availability to plants in soils is the solubility of the metal associated with the solid phase, since in order for root uptake to occur, a soluble species must exist adjacent to the root membrane for some finite period. The rate of release and form of this soluble species will have a strong influence on the rate and extent of uptake and, perhaps, mobility and toxicity in the plant and consuming animals. The factors influencing solubility and form of available metal species in soil vary widely geographically and include the concentration and chemical form of the element entering soil, soil properties (endogenous metal concentration, mineralogy, particle size distribution), and soil processes (e.g., mineral weathering, microbial activity), as these influence the kinetics of sorption reactions, metal concentration in solution and the form of soluble and insoluble chemical species. The plant root represents the first barrier to the selective accumulation of ions present in soil solution. Uptake and kinetic data for nutrient ions and chemically related nonnutrient analogs suggest that metabolic processes associated with root absorption of nutrients regulate both the affinity and rate of absorption of specific nonnutrient ions. Detailed kinetic studies of Ni, Cd, and Tl uptake by intact plants demonstrate multiphasic root absorption processes over a broad concentration range, and the use of transport mechanisms in place for the nutrient ions Cu, Zn, and K. Advantages and limitations of higher plants as indicators of increased levels of metal pollution are discussed in terms of these soil and plant phenomena.

The xylem exudates of soybean (Glycine max cv Williams), provided with fixed N, were characterized as to their organic constituents and in vivo and in vitro complexation of plutonium, iron, cadmium, and nickel. Ion exchange fractionation of whole exudates into their compound classes (organic acid, neutral, amino acid, and polyphosphate), followed by thinlayer electrophoresis, permitted evaluation of the types of ligands which stabilize each element. The polyvalent elements plutonium(IV) and iron(III) are found primarily as organic acid complexes, while the divalent elements nickel(II) and cadmium(II) are associated primarily with components of the amino acid/peptide fraction. For plutonium and cadmium, it was not possible to fully duplicate complexes formed in vivo by back reaction with whole exudates or individual class fractions, indicating the possible importance of plant induction processes, reaction kinetics, and/or the formation of mixed ligand complexes. The number and distribution of specific iron- and nickel-containing complexes varies with plant age and appears to be related to the relative concentration of organic acids and amino acids/peptides being produced and transported in the xylem as the plant matures.

Enzymatically separated leaf tissues of Nicotiana tabacum L., exhibiting good metabolic integrity, were used to evaluate the kinetics of sugar accumulation over the concentration range of 10 to 100 mm. Mesophyll cells exhibited Km values of 16 and 30 mm for glucose and sucrose, respectively; minor veins showed a reverse relationship, with Km values of 58 and 16 mm for glucose and sucrose, respectively. This would suggest that sucrose is preferentially absorbed by the minor vein net. Analysis of V(max) data indicates a reduction in the ability of isolated minor veins to accumulate substrate, implicating a symplastic rather than apoplastic route for intercellular transport. Competition studies demonstrate a common carrier for sucrose and glucose in both tissue types and suggest the presence of a "transport compartment," entry to which is regulated by a critical intracellular sucrose concentration.

The comparative behavior of sulfur (S) and technetium (Tc) in soybean seedlings shows gross subcellular distributions to be similar for these oxyanions. More than 75% of the tissue-deposited Tc remains soluble and extractable. Differences in Tc fixation/incorporation were noted for the nuclear and chloroplast fractions of leaf and root cells. Pulse studies showed that soluble protein and nitrate reductase levels rose in response to Tc accumulation by sink leaves but not source leaves. In vitro assay of chloroplast-based S reduction and incorporation systems showed Tc to be reduced and incorporated into amino nitrogen-containing products. A hypothesis related to the metabolic behavior of Tc in plants is presented.

The absorption characteristics of Cd(2+) by 10- to 12-day-old soybean plants (Glycine max cv Williams) were investigated with respect to influence of Cd concentration on adsorption to root surfaces, root absorption, transport kinetics and interaction with the nutrient cations Cu(2+), Fe(2+), Mn(2+), and Zn(2+). The fraction of nonexchangeable Cd bound to roots remained relatively constant at 20 to 25% of the absorbed fraction at solution concentration of 0.0025 to 0.5 micromolar, and increased to 45% at solution concentration in excess of 0.5 micromolar. The exchangeable fraction represented 1.4 to 32% of the absorbed fraction, and was concentration dependent. Using dinitrophenol as a metabolic inhibitor, the ;metabolically absorbed' fraction was shown to represent 75 to 80% of the absorbed fraction at concentration less than 0.5 micromolar, and decreased to 55% at 5 micromolar. At comparatively low Cd concentrations, 0.0025 to micromolar 0.3, root absorption exhibited two isotherms with K(2) values of 0.08 and 1.2 micromolar. Root absorption and transfer from root to shoot of Cd(2+) was inhibited by Cu(2+), Fe(2+), Mn(2+), and Zn(2+). Analyses of kinetic interaction of these nutrient cations with Cd(2+) indicated that Cu(2+), Fe(2+), Zn(2+), and possibly Mn(2+) inhibited Cd absorption competitively suggesting an involvement of a common transport site or process.

The absorption of Ni(2+) by 21-day-old soybean plants (Glycine max cv. Williams) was investigated with respect to its concentration dependence, transport kinetics, and interactions with various nutrient cations. Nickel absorption, measured as a function of concentration (0.02 to 100 mum), demonstrated the presence of multiple absorption isotherms. Each of the three isotherms conforms to Michaelis-Menten kinetics; kinetic constants are reported for uptake by the intact plant and for transfer from root to shoot tissues. The absorption of Ni(2+) by the intact plant and its transfer from root to shoot were inhibited by the presence of Cu(2+), Zn(2+), Fe(2+), and Co(2+). Competition kinetic studies showed Cu(2+) and Zn(2+) to inhibit Ni(2+) absorption competitively, suggesting that Ni(2+), Cu(2+), and Zn(2+) are absorbed using the same carrier site. Calculated K(m) and K(i) constants for Ni(2+) in the presence and absence of Cu(2+) were 6.1 and 9.2 mum, respectively, whereas K(m) and K(i) constants were calculated to be 6.7 and 24.4 mum, respectively, for Ni(2+) in the presence and absence of Zn(2+). The mechanism of inhibition of Ni(2+) in the presence of Fe(2+) and Co(2+) was not resolved by classical kinetic relationships.

Metabolic and physiological processes play important roles in regulating the transfer and behavior of trace elements in the soil/plant/animal system. The behaviors of Ni, Cd, Cr, T1, Np, Pu and Tc are used to illustrate important aspects of these processes. Microbial metabolism has both indirect and direct effects on trace element solubility in soils. Once non-nutrient trace elements are solubilized, the ability of plant roots to actively accumulate them is dependent on chemical activity of the element in soil solution, the presence of competing ions and the redox potential and absorption capacity of the root. After absorption in the plant, trace elements are translocated, metabolized and stored; fate and behavior varies with the properties of the element, but is generally analogous to nutrient elements. These processes can dramatically affect the availability of individual elements to animals consuming plants.

The absorption characteristics and mechanisms of pertechnetate (TcO(4) (-)) uptake by hydroponically grown soybean seedlings (Glycine max cv Williams) were determined. Absorption from 10 micromolar solutions was linear for at least 6 hours, with 30% of the absorbed TcO(4) (-) being transferred to the shoot. Evaluation of concentration-dependent absorption rates from solutions containing 0.02 to 10 micromolar TcO(4) (-) shows the presence of multiphasic absorption isotherms with calculated K(s) values of 0.09, 8.9, and 54 micromolar for intact seedlings. The uptake of TcO(4) (-) was inhibited by a 4-fold concentration excess of sulfate, phosphate, selenate, molybdate, and permanganate; no reduction was noted with borate, nitrate, tungstate, perrhenate, iodate, or vanadate. Analyses of the kinetics of interaction between TcO(4) (-) and inhibiting anions show permanganate to be a noncompetitive inhibitor, while sulfate, phosphate, and selenate, and molybdate exhibit characteristics of competitive inhibitors of TcO(4) (-) transport suggesting involvement of a common transport process.

The distribution and chemical behavior of Cd(2+) in tissues and its chemical form in xylem water of soybean plants (cv. Williams) were investigated. Following root absorption, Cd is strongly retained by roots, with only 2% of the accumulated Cd being transported to leaves; as much as 8% was transported to seeds during seed filling. In vivo xylem exudates contained two anionic Cd complexes in addition to inorganic forms of Cd. Once accumulated in root and leaf tissues, Cd rapidly equilibrated between the insoluble, soluble, and organelle fractions. Of the solubles, which contain 50% of the Cd, >50% was associated with components of >10,000 molecular weight, and <8% was associated with <500 molecular weight components. Cadmium accumulated in soybean seeds was primarily associated with cotyledons. Fractionation of seeds showed the soy proteinate and soy whey to contain 32 and 50% of the accumulated Cd, respectively.

A mathematical model for the reversible exchange of THO between the sieve tube lumen and its surrounding phloem tissue is used to explain the difference between the apparent velocities of THO and (14)C-sucrose transport observed when both are supplied simultaneously. Theoretically predicted results show a close correlation with those obtained experimentally. This model may be used in evaluating previous work in which THO was used as a tracer. The calculations support the existence of a mass flow of sugars in aqueous solution along the path.

Anatomical and ultrastructural details of a translocating 10-cm leaf of sugar beet (Beta vulgaris L. var. Klein Wanzleben) were correlated with translocation rate data. The minor veins were found to be 13 times as extensive as the major veins and measure 70 cm/cm(2) leaf lamina. Measurements disclosed that a 33-mu length of minor vein services 29 mesophyll cells with the result that translocate moves an average of 73 mu or 2.2 cell diameters during transport from mesophyll cells to a minor vein. High-resolution, freeze-dry autoradiography revealed that assimilates accumulate in organelle-rich cells of the minor vein phloem. Correlation of phloem volume and loading rate for minor veins yielded an uptake rate of 735 mumoles of sucrose per g fresh weight of phloem. The arrangement and structural features of minor veins appeared to be consistent with the concept that vein loading precedes translocation.

Earlier studies have shown that the retarding effect of low petiolar temperatures on sucrose transport through sugar beet (Beta vulgaris L.) petioles is markedly time-dependent. Although the initial effect of chilling the petiole to near 0 C is severely inhibitory, translocation rates soon recover (usually within about 2 hours) to values at or near the control rate. In the present studies, selected metabolic parameters were measured simultaneously with translocation. No stoichiometric relationships among petiolar sucrose transport, petiolar respiration (CO(2) production), and calculated petiolar ATP turnover rates were evident. It appears that the major sources of energy input energizing carbohydrate transport in sieve tubes function mainly at either loading or unloading sites and not at the level of individual sieve-tube elements.

Translocation profiles along the path were studied using a modified flap-feeding technique for the simultaneous application of THO and (14)C-sucrose. A re-evaluation of a mathematical model for phloem transport with reversible lateral exchange of tracer along the path indicates that lower apparent velocities for THO as compared to labeled carbohydrate are primarily due to extensive lateral exchange of THO along the conduction path. Path-chilling experiments support the concept that THO and (14)C-sucrose exhibit different lateral exchange characteristics. The data presented are consistent with a solutionflow mechanism.

Accumulation of translocate during steady-state labeling of photosynthate was measured in the source leaf petioles of sugar beet (Beta vulgaris L. monogerm hybrid). During an 8-hr period, 2.7% of the translocate or 0.38 mug carbon/min was accumulated per cm petiole. Material was stored mainly as sucrose and as compounds insoluble in 80% ethanol. The minimum peak velocity of translocation approached an average of 54 cm/hr as the specific activity of the (14)CO(2) pulse was progressively increased. The ratio of cross sectional area required for translocation to actual sieve tube area in the petiole was 1.2. A regression analysis of translocation rate versus sieve tube cross sectional area yielded a coefficient of 0.76. The specific mass transfer rate in the petiole was 1.4 g/hr cm(2) phloem or 4.8 g/hr cm(2) sieve tube. Histoautoradiographic studies indicated that translocation occurs through the area of phloem occupied by sieve tubes and companion cells while storage occurs in these cells plus cambium and phloem parenchyma cells. The ability of the petiole to act as a sink for translocate is consistent with the concept that storage along path tissue serves to buffer sucrose concentration in the translocate during periods of fluctuating assimilation.