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At least 307 records · Page 17Linked to original sources
PubMed2004

Salt stress enhances xylem development and expression of S-adenosyl-L-methionine synthase in lignifying tissues of tomato plants.

S-Adenosyl-L-methionine synthase (SAM; ATP: L-methionine adenosyltransferase, EC 2.5.1.6) catalyzes the biosynthesis of S-adenosyl-L-methionine (AdoMet), a universal methyl-group donor. This enzyme is induced by salinity stress in tomato (Lycopersicon esculentum Mill.). To elucidate the role of SAM and AdoMet in the adaptation of plants to a saline environment, the expression pattern and histological distribution of SAM was investigated in control and salt-stressed tomato plants. Immunohistochemical analysis showed that SAM proteins were expressed in all cell types and plant organs, albeit with preferential accumulation in lignified tissues. Lignin deposition was estimated by histochemical tests and the extent of tissue lignification in response to salinity was quantified by image analysis. The average number of lignified cells in vascular bundles was significantly greater in plants under salt stress, with a maximal expansion of the lignified area found in the root vasculature. Accordingly, the greatest abundance of SAM gene transcripts and proteins occurred in roots. These results indicate that increased SAM activity correlated with a greater deposition of lignin in the vascular tissues of plants under salinity stress. A model is proposed in which an increased number of lignified tracheary elements in tomato roots under salt stress may enhance the cell-to-cell pathway for water transport, which would impart greater selectivity and reduced ion uptake, and compensate for diminished bulk flow of water and solutes along the apoplastic pathway.

Environment↗
PubMed1979

A new island flap transfer from the dorsum of the index to the thumb.

We describe here a new island flap from the dorsum of the index finger, transferred on the first dorsal metacarpal artery with one or two veins and the terminal branches of the radial nerve. This vascular bundle is a reliable one, for we have had no necrosis in 12 consecutive cases. The quality of its venous outflow and the use of a dorsal donor site give it advantages over the Moberg-Littler island flap, unless a dorsal vein from the latter flap is preserved and sutured to a vein in the recipient site. The arterial vascularization without any skin pedicle makes this "kite" flap a more practical one than the "flag" flaps of Vilain or Holevitch or Kuhn. Finally, a one-stage transfer is usually preferable to a two-stage one (e.g. Adamson, Braillar). In a single operation, this transfer provides composite resurfacing of the thumb while bringing in new blood and nerve supply.

Bone Transplantation↗
PubMed1977

Measurements on the kidneys and vasa recta of various mammals in relation to urine concentrating capacity.

Maximum urine-concentrating capacity (UCC) differs widely among mammals of different species, being very high in some desert species (e.g. kangaroo rats) and very low in freshwater acquatic species (e.g. beaver). In this study, kidneys of 21 species of mammals from widely different habitats were studied in histological sections to determine whether differences in UCC can be attributed to differences in kidney structure. Parameters studied included the ratio of medullary to cortical thickness, the proportional subdivision of the medulla into inner and outer zones, and the dimensions of the vasa recta expressed in terms of the total area and the number of lumens within the vascular bundles. Determinations were made at a level where the size of individual vasa recta bundles has reached a constant maximum size, i.e. in the distal half of the outer zone. A positive correlation was found between the UCC and the ratio of medullary length to cortical thickness. No clear correlation existed between the proportion of the medullary length comprised of outer or inner zones and the UCC, although a trend to higher UCC in animals with relatively longer inner zones was apparent. Thus, it appears that the relative length of the entire medullary region is a major factor determining UCC, but the length of individual medullary zones is of lesser importance. A correlation was also found between the density of vasa recta per cubic millimeter of medullary tissue (the number of lumens regardless of identify in bundles, based on the number counted at the level sampled) and the UCC of the species. Data reported here support the view that UCC can be correlated with two parameters of kidney structure - the length of medulla relative to that of cortex and the density of vasa recta within the outer zone. It is proposed that the anatomical characteristics of the vascular supply to the medulla - that is, the vasa recta - are equally as important for the concentration of urine as is the primary mechanism determined by the characteristics of the loop of Henle and collecting ducts.

Anatomy, Comparative↗
PubMed2002

Functional imaging of plants: a nuclear magnetic resonance study of a cucumber plant.

Functional magnetic resonance imaging was used to study transients of biophysical parameters in a cucumber plant in response to environmental changes. Detailed flow imaging experiments showed the location of xylem and phloem in the stem and the response of the following flow characteristics to the imposed environmental changes: the total amount of water, the amount of stationary and flowing water, the linear velocity of the flowing water, and the volume flow. The total measured volume flow through the plant stem was in good agreement with the independently measured water uptake by the roots. A separate analysis of the flow characteristics for two vascular bundles revealed that changes in volume flow of the xylem sap were accounted for by a change in linear-flow velocities in the xylem vessels. Multiple-spin echo experiments revealed two water fractions for different tissues in the plant stem; the spin-spin relaxation time of the larger fraction of parenchyma tissue in the center of the stem and the vascular tissue was down by 17% in the period after cooling the roots of the plant. This could point to an increased water permeability of the tonoplast membrane of the observed cells in this period of quick recovery from severe water loss.

Biophysics↗
PubMed1994

Mastoidectomy reconstruction: revascularizing the canal wall repair.

Blood supply is the key to reconstruction of canal wall defects in cases of prior radical mastoidectomy. Revascularization of the defect is essential to nourish the overlying canal skin and to protect and supply the underlying solid support layer. Prior techniques have relied on free grafts or on local flaps of suspect vascular adequacy. A temporal pericranial flap is described that introduces a vascular bundle directly into the canal wall defect site. The flap is based on the superior and posterior aspects of the pinna and contains the middle temporal artery, which provides axial supply to the flap tip. The tissues of the flap are compact, enabling easy handling in the confines of the new canal. The flap is turned medially into the canal, avoiding compression or kinking of the vascular axis. The technique has been used in over 60 cases, producing excellent clinical results from a simplified technique.

Child, Preschool↗
PubMed2004

Tissue-specific localization of an abscisic acid biosynthetic enzyme, AAO3, in Arabidopsis.

Arabidopsis aldehyde oxidase 3 (AAO3) is an enzyme involved in abscisic acid (ABA) biosynthesis in response to drought stress. Since the enzyme catalyzes the last step of the pathway, ABA production sites may be determined by the presence of AAO3. Here, AAO3 localization was investigated using AAO3 promoter:AAO3-GFP transgenic plants and by an immunohistochemical technique. AAO3-GFP protein exhibited an activity to produce ABA from abscisic aldehyde, and the transgene restored the wilty phenotype of the aao3 mutant. GFP-fluorescence was detected in the root tips, vascular bundles of roots, hypocotyls and inflorescence stems, and along the leaf veins. Intense immunofluorescence signals were localized in phloem companion cells and xylem parenchyma cells. Faint but significant GFP- and immuno-fluorescence signals were observed in the leaf guard cells. In situ hybridization with antisense AAO3 mRNA showed AAO3 mRNA expression in the guard cells of dehydrated leaves. These results indicate that the ABA synthesized in vascular systems is transported to various target tissues and cells, and also that the guard cells themselves are able to synthesize ABA.

Abscisic Acid↗
PubMed1991

Late lesions of the brachial plexus after fracture of the clavicle.

Fractures of the clavicle, particularly those which are markedly displaced, may, in rare instances cause injury to the subclavian vessels and the brachial plexus which manifest progressively days or weeks after the initial trauma. More often than not, however, a costo-clavicular compression syndrome appears months or years after the clavicular fracture as a result of constriction by scar which invests the neuro-vascular bundle, by a secondary aneurysm or by hypertrophic callus. The authors report 16 such cases, one of which was treated conservatively, thirteen treated by surgical intervention while two cases are awaiting operation. These patients represent just over 1% of brachial plexus lesions seen over a period of twenty years in two surgical centres. Operative treatment consists of reduction of the clavicular deformity, possibly first rib resection, liberation of the plexus and correction of a vascular lesion as required. The outcome is usually good.

Adolescent↗
PubMed1996

Phaseolus ENOD40 is involved in symbiotic and non-symbiotic organogenetic processes: expression during nodule and lateral root development.

ENOD40 is an early nodulin gene, recently isolated from legume species forming nodules either after Rhizobium infection or spontaneously. ENOD40 cDNAs from Phaseolus plants were isolated and nucleotide sequence determination revealed 85% and 88.5% homology with the reported soybean cDNA clones. The putative polypeptide deduced coincides with the soybean one but a stop codon, almost in the middle of the respective ORF, renders it much shorter. This polypeptide was overexpressed as a fusion protein in Escherichia coli. Although the spatial expression pattern of the gene in the root pericycle and nodule primordium at early stages of development as well as in the pericycle of the vascular bundles and uninfected cells in mature nodules is comparable to the gene's expression pattern in soybean, differences in developmental regulation are evident. We have shown that ENOD40 transcripts are also detected at very early stages of lateral root development, in the dividing pericycle cells of the root stele that give rise to the lateral root primordia. The presence of Rhizobium causes an enhancement of the gene's expression and also induction of the gene in the vascular tissues of developed lateral roots. Interestingly, a discrimination on the gene's expression level in adventious and acropetal incipient lateral root primordia, emerging in infected and uninfected roots, is observed. This indicates that the gene's product may be involved in the hormonal status of the plant and that ENOD40 may be used as a molecular marker in lateral root initiation.

Amino Acid Sequence↗
PubMed1966

Accumulation of phosphate, sulfate and sucrose by excised Phloem tissues.

Excised petiolar vascular bundles and excised phloem tissues have been shown to take up phosphate, sulfate and sucrose by a true accumulation process and against high concentration ratios. Phosphate was accumulated principally as inorganic phosphate, and sucrose principally as sucrose. The rates of accumulation of the 3 solutes into the phloem-containing tissues were from 4 to 35 times higher than into comparable parenchyma tissue. It is suggested that this active accumulation mechanism plays an important role in the phenomenon of phloem transport.THE EXCISED VASCULAR, PHLOEM AND PARENCHYMA TISSUES SHOW AN AGING PHENOMENON: aerating the excised tissues for 18 hours prior to their use causes marked changes in the accumulatory behavior of the tissue. The data suggest that 1 phosphate accumulation system of low affinity but high capacity exists in fresh tissue, and that aging allows the development of a second, additional phosphate accumulation mechanism of high affinity and low capacity. A possible role in the control of phosphate movement is suggested.

Journal Article↗
PubMed1983

Intercostal nerve transfer in brachial plexus injuries: an experimental study.

Eighteen adult mongrel dogs underwent unilateral surgical disruption of the brachial plexus. Twelve animals (Group I) had as a second-stage procedure transfer of T4 and T5 intercostal nerves and their accompanying vascular bundles to the distal musculocutaneous nerve stump. Six animals (Group II) had restoration of musculocutaneous nerve continuity with conventional interpositional sural nerve cable grafts. Group I animals demonstrated significantly better electromyographic evidence of reinnervation and, comparing appearance and weight of operated and unoperated biceps muscles at the time of animal sacrifice, maintained greater gross weight and more normal overall appearance of muscle. Histologic study of muscle tissue showed no significant difference between the two groups whereas musculocutaneous nerve histology distal to all anastomoses revealed less fibrous tissue and a greater number of healthy-appearing axons in Group I. It is concluded that vascularized intercostal nerve transfer as performed in this study has theoretical advantages over conventional nonvascularized intercostal nerve transfer but additional investigation is required to make this determination. The superiority of vascularized intercostal nerve transfers over conventional interpositional sural nerve cable grafts has been demonstrated.

Animals↗
PubMed1999

VACM-1 receptor is specifically expressed in rabbit vascular endothelium and renal collecting tubule.

The vasopressin-activated calcium-mobilizing (VACM-1) protein is a novel arginine vasopressin (AVP) receptor that shares sequence homology with a cullin multigene family but not with the AVP receptors. To characterize the VACM-1 receptor, we examined its tissue-specific expression using Northern blot, RT-PCR, and immunostaining analyses. Northern blot hybridization identified a 6. 4-kb cRNA species that was expressed in the rabbit kidney medulla, brain, heart, and ovaries. In human tissue, VACM-1 mRNA is a larger (7.5 kb) cRNA found in the kidney, brain, heart, placenta, and skeletal muscle. VACM-1-specific RT-PCR products were detected in mRNA from rabbit kidney medulla, brain, heart, and mesenteric arteries. No expression of VACM-1 could be detected in rabbit aorta, gastrointestinal tract, or liver. Coimmunostaining with anti-VACM-1 antibodies (Ab) and a specific vascular endothelial cell marker, CD31 monoclonal Ab, localized VACM-1 expression to the vasculature in specific tissues. We identified the kidney cells expressing VACM-1 receptor by coimmunostaining with the following monoclonal Ab, which recognize epitopes in specific segments of the nephron: rct-30 Ab, reactive against the cortical and medullary collecting tubule (CT) cells; mr-omct Ab, reactive against the mitochondria-rich cells of the outer medullary CT; and an Ab specific against the loop of Henle segment. These studies indicated that the VACM-1 receptor is expressed only in the medullary CT. Kidney coimmunostaining with anti-VACM-1 and CD31 Ab identified VACM-1-receptor expression in glomeruli and medullary vascular bundles. These results demonstrate that the novel VACM-1 receptor, expressed in many organs, is localized to the endothelial cells. In the kidney, it is also expressed in the medullary CT cells. Thus VACM-1 may be involved in the regulation of endothelial permeability and water transport in the CT.

Animals↗
PubMed1984

Selective vulnerability of the medullary thick ascending limb to anoxia in the isolated perfused rat kidney.

A specific anatomical lesion sharply localized to the cells of the medullary thick ascending limbs (mTAL) and characterized by mitochondrial swelling progressing to nuclear pyknosis and cell death is elicited reproducibly in isolated rat kidneys perfused for 15 or 90 min with cell-free albumin-Ringer's medium gassed with 5% CO2, 95% O2 (O2 content, 1.5 vol/100 ml). The lesion, involving about half of mTALs, appears first in mTALs removed from vascular bundles and near the inner medulla, areas most likely to be anoxic. Hypoxic perfusion (O2 content 0.12 vol/100 ml) exaggerates the lesion, wiping out gradations of damage and extending it to all mTALs. O2-enriched perfusions using rat erythrocytes (O2 content 7.1 vol/100 ml) completely eliminates the lesion (unless gassed with carbon monoxide). Similarly, supplementation of the perfusion medium with a purified hemoglobin (O2 content 5.8 vol/100 ml) prevents mTAL injury. Perfusion with a fluorinated hydrocarbon blood substitute, Oxypherol (O2 content 4.3 vol/100 ml) also attenuates the lesion. These findings suggest that the mTAL is exquisitely susceptible to anoxic damage because of low O2 supply imposed by the medullary vascular system and the high rate of metabolism mandated by active reabsorption of sodium chloride. The vulnerability of the mTAL to anoxic injury could play a key role in the pathogenesis of ischemic renal injury.

Animals↗
PubMed2002

Changes in osmotic and turgor pressure in response to sugar accumulation in barley source leaves.

Pressure-probe measurements and single-cell sampling and analysis techniques were used to determine the effect of photosynthetic production and accumulation of sugars on osmotic and turgor pressures of individual cells of barley ( Hordeum vulgare L.) source leaves. In control plants, the changes in osmotic pressure in individual cells during the photoperiod were different for mesophyll (increase of 276 mOsmol/kg), parenchymatous bundle sheath (PBS; increase of 100 mOsmol/kg) and epidermis (remains constant). There was also an increase in osmotic pressure at the tissue level. Cooling of roots and the shoot apical meristem restricted the export of sugars from leaves, and the resulting changes in osmotic and turgor pressure were monitored. In contrast to the control leaves, mesophyll, PBS, and epidermal cells showed a similar increase in osmotic pressure (up to 500 mOsmol/kg). Cooling also increased the turgor pressure in epidermal and (to a greater extent) PBS cells. The difference in turgor pressure between epidermal and PBS cells is consistent with the presence of a water potential gradient within the leaf, from the vascular bundles towards the leaf surface.

Biological Transport↗
PubMed1987

Fragmentation and flow of grazed coastal Bermudagrass through the digestive tract of cattle.

Samples of forage fragments were obtained from the upper (RUS) and lower (RLS) strata of the reticulorumen and feces (F) of four Brahman X Jersey steers grazing Coastal bermudagrass (CB) of two maturities with dry matter digestibilities (DMD) of 54.8 and 64.3%. Forage fragments were separated by particle size and evaluated histochemically for tissue type and fragmentation pattern. Fragmentation pattern was similar to that previously observed due to ingestive mastication. There was longitudinal separation of vascular bundles (VB) and severing at VB ends. Microscopically, similar size fragments from RUS were indistinguishable from those of RLS. The major difference between RUS and RLS was the distribution of different size particles. Larger particles were associated with the RUS in cattle consuming immature and mature CB. More large particles were associated with mature compared with the immature CB in the RUS and RLS. The distribution of different size particles in the F was similar for both maturities, suggesting that similar particle size reduction was required regardless of maturity. Smaller particles in the rumen and F appeared to contain more lignin (determined histochemically) and were composed of indigestible fragments of cuticle and lignified vascular tissue. Cattle grazing mature CB had higher ruminal fills (2.40 vs 2.02 kg dry matter/100 kg body weight), reduced rates of passage and lower voluntary intake (2.50 vs 3.14 kg DM/100 kg body weight). Lower intake of mature CB may have resulted from a reduced rate of particle size reduction. Similarities in fragmentation patterns due to ingestive and ruminative mastication were interpreted to indicate that mastication was responsible for most of the particle size reduction of CB and that mastication facilitated digestion of potentially digestible tissues.

Animal Feed↗
PubMed1981

Fractionation of cell-wall preparations from grass leaves by centrifuging in non-aqueous density gradients.

1. Dried preparations of cell walls from perennial-ryegrass (Lolium perenne) and Italian-ryegrass (L. multiflorum) leaves were suspended in mixtures of carbon tetrachloride with light-petroleum (b.p. 45--50 degrees C) or alcohols and layered on density gradients formed from the same solvents. 2. On centrifugation, the cell walls become distributed throughout a suitably chosen gradient. Fractions corresponding to various regions of the gradient were separated, examined under the microscope and analysed. 3. Cell-wall preparations made from leaf material ground in liquid N2, or in a triple roll mill, showed considerable heterogeneity in particle size, and their behaviour in the density gradient was variable, although there was a general indication that walls derived from vascular bundles were less dense than those from sclerenchyma. 4 Treatment in a vibratory ball mill decreased the size of the particles and produced a more uniform material, but made it impossible to distinguish the origins of the particles. This material behaved more reproducibly in the density gradient. 5. Some fractionations were also made by successive centrifugation in media of increasing relative density. 6. Analyses of the fractions obtained by each method indicated that the less dense had a greater proportion of xylose in the polysaccharide components, and higher contents of acetyl groups and lignin, confirming the close relationship between these components in plant cell walls. 7. The results show that there are differences in polysaccharide composition between the cell-wall types in the grass leaf, the vascular tissue being richer in hemicellulose relative to cellulose than the sclerenchyma.

Butanols↗
PubMed1988

Vascular medullary patency in free vascularized bone grafts: CT scan experimental study.

In an experimental study using 13 mongrel adult dogs, 6 cm of the anterior part of the left ninth rib were harvested, including the posterior intercostal vessels. The grafts were transferred, based on the periosteal circulation alone, to a previously induced femoral head ischemic necrosis. Microsurgical anastomoses were performed between the posterior intercostal vascular bundle and the caudal gluteal vessels at the recipient thigh zone. Using a high resolution CT scan and morphologic evaluation, it was demonstrated that the medullary circulation network filled on contrast medium. The entire cortex and medullary cavity were supplied from endosteal vessels coming from a reversed periosteal blood flow.

Anastomosis, Surgical↗
PubMed2001

Subterranean structures and mycotrophy of the achlorophyllous Dictyostega orobanchoides (Burmanniaceae).

Plants of Dictyostega orobanchoides arise from about 1 mm thick rhizomes, which are densely covered by sessile, imbricate, peltate scale leaves. The resulting interfoliar spaces are inhabited by fungal hyphae up to 6 microns thick, often developing vesicle-like bladders. The fungus also colonizes the tissue of the scale leaves, inter- as well as intracellularly, forming vesicles but no arbuscules, and it even penetrates the vascular bundles of the leaves. The rhizome itself does not become infected. The 200 microns thick roots emerge from the rhizome and have a 2-layered cortex and voluminous rhizodermis, which both are delicate and often disrupted or missing. In contrast, the strongly reinforced, tertiary endodermis and the central cylinder are durable and have a considerable tensile strength. Although the roots grow through the hyphal masses in the interfoliar spaces when emerging from the rhizome, they only become infected from the rhizosphere. A collar of rhizomogenous tissue hinders the interfoliar hyphae from direct contact to the roots. Only within the rhizodermis, the mycorrhizal fungus builds coils of heteromorphic hyphae, arbuscule-like structures, and vesicles. Hence, the mycorrhiza in D. orobanchoides is assigned to the arbuscular mycorrhiza. It is hypothezised, that the ephemeral mycorrhizal tissue combined with the durable vascular system of the roots is a strategy to avoid the high costs of protecting the large rhizodermal surface area. The rhizomogenous collar is explained as an extra protection to the tender, young roots, when emerging from the rhizome. The necessity to include other subterranean plant organs along with the roots in future mycorrhizal studies is emphasized.

Fungi↗
PubMed2002

Development of Agrobacterium tumefaciens C58-induced plant tumors and impact on host shoots are controlled by a cascade of jasmonic acid, auxin, cytokinin, ethylene and abscisic acid.

The development of Agrobacterium tumefaciens-induced plant tumors primarily depends on the excessive production of auxin and cytokinin by enzymes encoded on T-DNA genes integrated into the plant genome. The aim of the present study was to investigate the involvement of additional phytohormone signals in the vascularization required for rapid tumor proliferation. In stem tumors of Ricinus communis L., free auxin and zeatin riboside concentrations increased within 2 weeks to 15-fold the concentrations in control stem tissue. Auxin and cytokinin immunolocalization revealed the highest concentrations within and around tumor vascular bundles with concentration gradients. The time-course of changes in free auxin concentration in roots was inversely correlated with that in the tumors. The high ethylene emission induced by increased auxin- and cytokinin correlated with a 36-fold accumulation of abscisic acid in tumors. Ethylene emitted from tumors and exogenously applied ethylene caused an increase in abscisic acid concentrations also in the host leaves, with a diminution in leaf water vapor conductance. Jasmonic acid concentration reached a maximum already within the first week of bacterial infection. A wound effect could be excluded. The results demonstrate the concerted interaction of a cascade of transiently induced, non-T-DNA-encoded phytohormones jasmonic acid, ethylene and abscisic acid with T-DNA-encoded auxin and zeatin riboside plus trans-zeatin, all of which are required for successful plant tumor vascularization and development together with inhibition of host plant growth.

Abscisic Acid↗