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Biomedical subjects

B Sundberg

Publications and source records attributed to B Sundberg.

At least 37 records · Page 2Linked to original sources
PubMed2000

Cambial-region-specific expression of the Agrobacterium iaa genes in transgenic aspen visualized by a linked uidA reporter gene.

The level of indole-3-acetic acid (IAA) was locally modified in cambial tissues of transgenic aspen (Populus tremula L. x Populus tremuloides Michx.). We also demonstrate the use of a linked reporter gene to visualize the expression of the iaa genes. The rate-limiting bacterial IAA-biosynthetic gene iaaM and the reporter gene for beta-glucuronidase (GUS), uidA, were each fused to the cambial-region-specific Agrobacterium rhizogenes rolC promoter and linked on the same T-DNA. In situ hybridization of the iaaM gene confirmed that histochemical analysis of GUS activity could be used to predict iaaM gene expression. Moreover, quantitative fluorometric analysis of GUS activity allowed estimation of the level of de novo production of IAA in transgenic lines carrying a single-copy insert of the iaaM, uidA T-DNA. Microscale analysis of the IAA concentration across the cambial region tissues showed an increase in IAA concentration of about 35% to 40% in the two transgenic lines, but no changes in the radial distribution pattern of IAA compared with wild-type plants. This increase did not result in any changes in the developmental pattern of cambial derivatives or the cambial growth rate, which emphasizes the importance of the radial distribution pattern of IAA in controlling the development of secondary xylem, and suggests that a moderate increase in IAA concentration does not necessarily stimulate growth.

Blotting, Northern↗
PubMed2000

Radial distribution pattern of pectin methylesterases across the cambial region of hybrid aspen at activity and dormancy.

Biochemical microanalysis combined with tangential cryosectioning was used to visualize the distribution of pectin methylesterases (PMEs) across the cambial region in active and dormant hybrid aspen (Populus tremula L. x Populus tremuloides Michx). These novel techniques allowed us to relate activity and isoforms of PMEs to specific tissues and developmental stages of the stem to get more information on the physiological function of PMEs in cambial growth. Isoelectrofocusing analysis revealed numerous isoforms that were differentially distributed according to the tissue-type and to the cambial stage. A neutral isoform was found to be distributed ubiquitously across the stem of both active and dormant trees, which suggests that it is a housekeeping isoform involved in the maintenance of the cell wall integrity throughout the stem. In addition, two distinct isoforms having different isoelectric points were found to be related to the differentiation of cambial derivatives. A basic isoform appears to be a physiological marker of the dormant stage involved in the cessation of meristematic radial growth, whereas an acidic isoform is functionally related to the immediate expansion of the cambial daughter cells that occurs bilaterally on each side of the cambium at the active stage.

Carboxylic Ester Hydrolases↗
PubMed1999

Accurate and high resolution in situ hybridization analysis of gene expression in secondary stem tissues.

Accurate in situ hybridization analysis in secondary stem tissues of plants has been hindered by specific characteristics of these tissues. First, secondary cell walls non-specifically bind probes used for in situ hybridization thus preventing gene expression analysis in the lignified regions of the stem, such as the xylem. Second, the mRNA in the cambial meristem and its recent derivatives are prone to inadequate fixation when conventional techniques are used. Here we describe an in situ hybridization technique which uses fast freezing and freeze substitution to cryoimmobilize the mRNA followed by embedding in a methacrylate resin for high-resolution analysis of gene expression. By using a transgenic poplar line harbouring rolC:uidA, rolC:iaaM, the gene expression pattern could be compared with histochemical GUS staining. This in situ hybridization technique results in superior preservation of cellular contents, retention of mRNA in all cell types in the poplar stem, a significant reduction of non-specific binding to secondary cell walls and a resolution not previously possible in secondary tissues. This technique will be particularly valuable for the expression analysis of genes involved in xylogenesis and wood formation.

Gene Expression↗
PubMed1999

Oral desmopressin for nocturnal polyuria in elderly subjects: a double-blind, placebo-controlled randomized exploratory study.

OBJECTIVE: To evaluate the decrease in nocturnal diuresis, nocturnal polyuria and the safety of oral desmopressin in elderly subjects with nocturia. SUBJECTS AND METHODS: After being identified using a population-based questionnaire, subjects were included in the study if they; (i) were healthy and free from medication with possible influence on the diuresis or voiding pattern; (ii) had an increased nocturnal frequency (>/=2 nocturnal voids/night, as reported before screening); (iii) had a nocturnal urinary output of >/=0.9 mL/min; (iv) completed and responded to an initial dose-titration study. Twelve men and five women (mean age 67.7 years, sd 4.6 years) met these criteria and were treated with oral desmopressin or placebo at bedtime for 2 weeks on each medication in a randomized, double-blind, crossover design. RESULTS: Subjects treated with desmopressin had a significantly reduced nocturnal diuresis of 0.59 mL/min compared with those on placebo (95% confidence interval, CI, 0.33-0.85). The 24-h diuresis was unaffected by desmopressin treatment. Patients treated with desmopressin had fewer micturitions at night than had those on placebo (1.1 and 1.7, respectively; P<0.001; mean difference=0.59; 95% CI, 0.32-0.85). The reduction in nocturnal diuresis was dependent on the baseline level of night-time diuresis (r=0.886; r2=0.785; P<0.0001) and the nocturnal part of the baseline 24 h-diuresis (r=0.708; r2=0.502; P<0.001). After desmopressin treatment was withdrawn, diuresis returned to the levels before treatment. The time from falling asleep to first awakening was improved by 1.4 h in patients treated with desmopressin. There was no change in body weight or ankle circumference during desmopressin treatment. Overall, the treatment was well tolerated and no serious adverse events were observed. CONCLUSION: Desmopressin was effective in reducing nocturnal diuresis and nocturnal voids in polyuric elderly subjects, with no significant adverse events or inconvenience to the patient. The length of uninterrupted sleep was also improved.

Administration, Oral↗
PubMed1999

Incompatibility between human blood and isolated islets of Langerhans: a finding with implications for clinical intraportal islet transplantation?

The remarkable difference in success rates between clinical pancreas transplantation and islet transplantation is poorly understood. Despite the same histocompatibility barrier and similar immunosuppressive treatments in both transplantation procedures, human intraportal islet transplantation has a much inferior success rate than does vascularized pancreas transplantation. Thus far, little attention has been directed to the possibility that islets transplanted into the blood stream may elicit an injurious incompatibility reaction. We have tested this hypothesis in vitro with human islets and in vivo with porcine islets. Human islets were exposed to nonanticoagulated human ABO-compatible blood in surface-heparinized polyvinyl chloride tubing loops. Heparin and/or the soluble complement receptor 1 (sCR1) TP10 were tested as additives. Adult porcine islets were transplanted intraportally into pigs, and the liver was recovered after 60 min for immunohistochemical staining. Human islets induced a rapid consumption and activation of platelets. Neutrophils and monocytes were also consumed, and the coagulation and complement systems were activated. Upon histological examination, islets were found to be embedded in clots and infiltrated with CD11+ leukocytes. Furthermore, the cellular morphology was disrupted. When heparin and sCR1 were added to the blood, these events were avoided. Porcine islets retrieved in liver biopsies after intraportal islet allotransplantation showed a morphology similar to that of human islets perifused in vitro. Thus, exposure of isolated islets of Langerhans to allogenic blood resulted in significant damage to the islets, a finding that could explain the unsatisfactory clinical results obtained with intraportal islet transplantation. Because administration of heparin in combination with a soluble complement receptor abrogated these events, such treatment would presumably improve the outcome of clinical islet transplantation by reducing both initial islet loss and subsequent specific immune responses.

Adult↗
PubMed1998

Gene discovery in the wood-forming tissues of poplar: analysis of 5, 692 expressed sequence tags.

A rapidly growing area of genome research is the generation of expressed sequence tags (ESTs) in which large numbers of randomly selected cDNA clones are partially sequenced. The collection of ESTs reflects the level and complexity of gene expression in the sampled tissue. To date, the majority of plant ESTs are from nonwoody plants such as Arabidopsis, Brassica, maize, and rice. Here, we present a large-scale production of ESTs from the wood-forming tissues of two poplars, Populus tremula L. x tremuloides Michx. and Populus trichocarpa 'Trichobel.' The 5,692 ESTs analyzed represented a total of 3,719 unique transcripts for the two cDNA libraries. Putative functions could be assigned to 2,245 of these transcripts that corresponded to 820 protein functions. Of specific interest to forest biotechnology are the 4% of ESTs involved in various processes of cell wall formation, such as lignin and cellulose synthesis, 5% similar to developmental regulators and members of known signal transduction pathways, and 2% involved in hormone biosynthesis. An additional 12% of the ESTs showed no significant similarity to any other DNA or protein sequences in existing databases. The absence of these sequences from public databases may indicate a specific role for these proteins in wood formation. The cDNA libraries and the accompanying database are valuable resources for forest research directed toward understanding the genetic control of wood formation and future endeavors to modify wood and fiber properties for industrial use.

Arabidopsis↗
PubMed1998

Desmopressin for the treatment of nocturnal polyuria in the elderly: a dose titration study.

OBJECTIVE: To evaluate the decrease in nocturnal polyuria and the tolerability of three different doses of oral desmopressin in elderly subjects. SUBJECTS AND METHODS: Subjects were included in the study if they; (i) were healthy and free from medication with possible influence on their diuresis or voiding pattern: (ii) had an increased nocturnal frequency (> or = 2 nocturnal voids, as reported in the pre-screening period); and (iii) had a nocturnal urinary output of > or = 0.9 mL/min. Seventeen men and six women (mean age 68.1, SD 4.7 years) met these criteria and were treated with 0.1, 0.2 and 0.4 mg oral desmopressin given at bedtime, each dose taken for one week on three consecutive weeks. RESULTS: The mean (SD) nocturnal diuresis before treatment was 1.6 (0.7) mL/min, which decreased significantly to 1.1 (0.4) mL/min when 0.1 mg desmopressin was given. A dose of 0.2 mg desmopressin resulted in a further small decrease in the nocturnal diuresis to 0.9 (0.4) mL/min, whereas the 0.4 mg dose produced no additional effect. The reduction in nocturnal diuresis occurred almost exclusively in the group with a nocturnal urinary output of > or =1.3 mL/min. After treatment, diuresis returned to pretreatment levels. There was no change in body weight or in ankle circumference during desmopressin treatment and no serious adverse effects were observed. CONCLUSION: Desmopressin reduces nocturnal diuresis in polyuric elderly subjects and this reduction, occurring with doses of 0.1 mg given at bedtime, does not increase in a dose-dependent way.

Administration, Oral↗
PubMed1998

Indole-3-acetic acid controls cambial growth in scots pine by positional signaling

The vascular cambium produces secondary xylem and phloem in plants and is responsible for wood formation in forest trees. In this study we used a microscale mass-spectrometry technique coupled with cryosectioning to visualize the radial concentration gradient of endogenous indole-3-acetic acid (IAA) across the cambial meristem and the differentiating derivatives in Scots pine (Pinus sylvestris L.) trees that had different rates of cambial growth. This approach allowed us to investigate the relationship between growth rate and the concentration of endogenous IAA in the dividing cells. We also tested the hypothesis that IAA is a positional signal in xylem development (C. Uggla, T. Moritz, G. Sandberg, B. Sundberg [1996] Proc Natl Acad Sci USA 93: 9282-9286). This idea postulates that the width of the radial concentration gradient of IAA regulates the radial number of dividing cells in the cambial meristem, which is an important component for determining cambial growth rate. The relationship between IAA concentration in the dividing cells and growth rate was poor, although the highest IAA concentration was observed in the fastest-growing cambia. The radial width of the IAA concentration gradient showed a strong correlation with cambial growth rate. The results indicate that IAA gives positional information in plants.

Journal Article↗
PubMed1997

Efficacy of immunosuppressive drugs in islet xenotransplantation: leflunomide in combination with cyclosporine and mycophenolate mofetil prevents islet xenograft rejection in the pig-to-rat model.

BACKGROUND: Morphological characteristics of islet xenograft rejection differ from those of islet allograft rejection. Therefore, prevention of islet xenograft rejection probably requires a different type of immunosuppression from that used in allogeneic transplantation. METHODS: Fetal porcine islet-like cell clusters (ICC) were transplanted into the renal subcapsular space of rats treated with different immunosuppressive protocols. The existence of a cellular infiltrate or deposits of antibodies and complement in the grafts was evaluated at different times after transplantation using immunohistochemistry. RESULTS: Treatment with leflunomide (LEF), cyclosporine (CsA), mycophenolate mofetil (MMF), 15-deoxyspergualin, and rapamycin alone or in combination had an insufficient inhibitory effect on ICC xenograft rejection. However, in animals treated with LEF+CsA, the rejection process was markedly inhibited. However, some macrophages and T cells were still present, and at 24 days, the xenografts were destroyed. In LEF+CsA-treated animals that were given sera containing an excessive amount of rat anti-porcine xenoreactive antibodies, marked deposits of IgG, and to some extent C3 as well, were detected along the border between intact ICC, and the xenografts were surrounded by macrophages. However, almost no cells infiltrated the grafts, and there were many intact ICC. In animals treated with LEF+CsA+MMF, only occasional infiltrating cells were seen at 12 and 24 days after transplantation, and the endocrine tissue was completely intact. CONCLUSIONS: LEF+CsA+MMF prevented rejection of porcine ICC xenografts in the rat for up to 24 days after transplantation.

Animals↗
PubMed1996

Auxin as a positional signal in pattern formation in plants.

By using a novel, extremely sensitive and specific gas chromatography-mass spectrometry technique we demonstrate in Pinus sylvestris (L.) trees the existence of a steep radial concentration gradient of the endogenous auxin, indole-3-acetic acid, over the lateral meristem responsible for the bulk of plant secondary growth, the vascular cambium. This is the first evidence that plant morphogens, such as indole-3-acetic acid, occur in concentration gradients over developing tissues. This finding gives evidence for a regulatory system in plants based on positional signaling, similar to animal systems.

Journal Article↗
PubMed1996

Substrates available for colonic fermentation from oat, barley and wheat bread diets. A study in ileostomy subjects.

Nutrients not absorbed in the small bowel will form substrates for microbial growth in the colon which may have implication for the development of colon cancer. The aim of the present study was to investigate whether fibre-rich oat and barley diets increase the excretion of energy-supplying nutrients from the small bowel compared with a low-fibre wheat diet, and whether a possible increase could be related to the beta-glucan content. Nine ileostomy subjects were served four types of bread together with a low-fibre basal diet (12 g dietary fibre/d). The breads were based on either wheat flour (W diet, 7 g dietary fibre/d), oat bran (OB diet, 29 g dietary fibre/d), the same amount of oat bran with addition of beta-glucanase (EC 3.2.1.4) (OBE diet, 19 g dietary fibre/d) or a fibre-rich barley fraction (B diet, 35 g dietary fibre/d). An increased ileal excretion of starch was observed with the barley diet but no effect of the oat beta-glucan on starch recovery was found. The NSP + Klason lignin in the ileostomy effluents accounted only for 24, 31, 24 and 35% of the gross energy excretion in the W, OB, OBE and B diet periods respectively. A large part of the dry weight and energy (30, 21, 28 and 27%, in the W, OB, OBE and B diets respectively) in the effluents could not be identified as fat, protein, total starch or NSP + Klason lignin. This unidentified part was probably made up of oligosaccharides, endogenous losses and nutrient complexes. Methods for identifying and analysing these components should be developed and their role as substrates for colonic fermentation and colon cancer development ought to be investigated.

Adult↗
PubMed1996

Mixed-linked beta-glucan from breads of different cereals is partly degraded in the human ileostomy model.

The purpose of this investigation was to study the degradation of beta-glucan in the small intestine and the molecular weight of beta-glucan in the excreta of nine ileostomy subjects after consumption of different diets based on bread made with oat bran (oat bread), a fiber-rich barley fraction (barley bread), or wheat flour (wheat bread) as the main ingredients. Oat bread with enzymatically degraded beta-glucan was also used (oat + enzyme bread). The beta-glucan intake from the four diets was 12.5, 12.9, 1.1, and 4.0 g/d, respectively. On the basis of dry matter, the night effluents accounted for approximately 15% of the total amount of the excreta, with the highest proportion (22%) being for the wheat-bread diet. A notable loss of beta-glucan (0.7-2.4 g/d, or 13-64%) was found when intake was compared with excretion. In vitro, a higher viscosity development with time for dispersions of oat bread compared with barley bread was noted, which could be related to the higher molecular weight of the beta-glucan in this bread. There seemed to be a depolymerization of the beta-glucan both during bread making and transit through the upper gastrointestinal tract.

Adult↗