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At least 433 records · Page 24Linked to original sources
PubMed2002

Five-year experience in aortic root replacement with the flanged composite graft.

BACKGROUND: Replacement of the aortic root with a composite graft containing a prosthetic mechanic valve is the preferred surgical procedure for tailoring the aortic root. The aim of this study is to determine the 5-year experience with the composite root replacement using our new modification of the Bentall technique. METHODS: Between January 1996 and June 2001, 96 patients underwent aortic root replacement using a flanged composite graft. Eighty patients (83.3%) were male, and 16 patients (16.7%) were female with a mean age of 48.7 +/- 14.4 years. Indications for operation were a true or false aneurysm (65.6%), severe calcified aortic valve stenosis (4.2%) or severe aortic insufficiency (2.1%) with dilated ascending aorta, acute dissection (2.1%), or combination of indications (26%). Thirty-one patients (32.3%) received a concomitant cardiac procedure. Mean aortic cross-clamp time was 89.5 +/- 28.6 minutes, and mean cardiopulmonary bypass time was 146.2 +/- 45.6 minutes. Total follow-up was 253.9 patient-years. RESULTS: Operative mortality was 8.3% (8 patients). The causes of hospital mortality were severe bleeding (3 patients), low cardiac output syndrome (2), acute respiratory distress syndrome (2) and cerebrovascular event (1). No patient died of flange-related complications. Univariate predictors of early mortality were low cardiac output syndrome (p < 0.001), neurologic complication (p = 0.03), and renal complication (p = 0.03). Multivariate analysis demonstrated only low cardiac output syndrome to be significant (p = 0.001) predictor for early mortality. There were five (5.7%) late deaths. Actuarial survival was 82.65% +/- 4.8% at 5 years (1.95% patient-year). Cox proportional hazards regression analysis demonstrated only low cardiac output syndrome to be significant (p = 0.032) predictor for late mortality. Actuarial freedom from prosthetic- and technique-related mortality was 100% at 5 years. CONCLUSIONS: The flanged composite graft offers excellent long-term results, with very low prevalence of prosthetic-related complications. The new created sinuses and the flange are especially helpful to continue physiologic function of the aortic root.

Adult↗
PubMed1999

Laser ablation of root cap cells: implications for models of graviperception.

The initial event of gravity perception by plants is generally thought to occur through sedimentation of amyloplasts in specialized sensory cells. In the root, these cells are the columella which are located toward the center of the root cap. To define more precisely the contribution of columella cells to root gravitropism, we used laser ablation to remove single columella cells or groups of these cells and observed the effect of their removal on gravity sensing and response. Complete removal of the cap or all the columella cells (leaving peripheral cap cells intact) abolishes the gravity response of the root. Removal of stories of columella revealed differences between regions of the columella with respect to gravity sensing (presentation time) versus graviresponse (final tropic growth response of the root). This fine mapping revealed that ablating the central columella located in story 2 had the greatest effect on presentation time whereas ablating columella cells in story 3 had a smaller or no effect. However, when removed by ablation the columella cells in story 3 did inhibit gravitropic bending, suggesting an effect on translocation of the gravitropic signal from the cap rather than initial gravity perception. Mapping the in vivo statolith sedimentation rates in these cells revealed that the amyloplasts of the central columella cells sedimented more rapidly than those on the flanks do. These results show that cells with the most freely mobile amyloplasts generate the largest gravisensing signal consistent with the starch statolith hypothesis of gravity sensing in roots.

Arabidopsis↗
PubMed1998

Molecular genetics of root gravitropism and waving in Arabidopsis thaliana.

When Arabidopsis thaliana seedlings grow embedded in an agar-based medium, their roots grow vertically downward. This reflects their ability to sense the gravity vector and to position their tip parallel to it (gravitropism). We have isolated a number of mutations affecting root gravitropism in Arabidopsis thaliana. One of these mutations, named arg1, affects root and hypocotyl gravitropism without promoting defects in starch content or in the ability of seedlings' organs to respond to plant hormones. The ARG1 gene was cloned and shown to code for a protein with a J domain at its amino terminus and a second sequence motif found in several cytoskeleton binding proteins. Mutations in the AGR1 locus promote a strong defect in root gravitropism. Some alleles also confer an increased root resistance to exogenous ethylene and an increased sensitivity to auxin. AGR1 was cloned and found to encode a putative transmembrane protein which might be involved in polar auxin transport, or in regulating the differential growth response to gravistimulation. When Arabidopsis seedlings grow on the surface of agar-based media tilted backward, their roots wave. That wavy pattern of root growth derives from a combined response to gravity, touch and other surface-derived stimuli. It is accompanied by a reversible rotation of the root tip about its axis. A number of mutations affect the presence or the shape of root waves on tilted agar-based surfaces. One of them, wvc1, promotes the formation of compressed root waves under these conditions. The physiological and molecular analyses of this mutant suggest that a tryptophan-derived molecule other than IAA might be an important regulator of the curvature responsible for root waving.

Arabidopsis↗
PubMed2000

A novel two-component hybrid molecule regulates vascular morphogenesis of the Arabidopsis root.

The developmental ontogeny of the vascular system (consisting of xylem, phloem and [pro]cambium) is poorly understood despite its central role in plant physiology. We show that in the Arabidopsis root meristem, xylem cell lineages are specified early, whereas phloem and procambium are established through a set of asymmetric cell divisions. These divisions require the WOODEN LEG (WOL) gene. The WOL gene encodes a novel two-component signal transducer with an unusual tandem arrangement of two receiver domains. It is expressed specifically in the vasculature from the early stages of embryogenesis on, consistent with a role as a sensor for vascular morphogenesis.

Amino Acid Sequence↗
PubMed2006

Projections of the second cervical dorsal root ganglion to the cochlear nucleus in rats.

Physiological, anatomical, and clinical data have demonstrated interactions between somatosensory and auditory brainstem structures. Spinal nerve projections influence auditory responses, although the nature of the pathway(s) is not known. To address this issue, we injected biotinylated dextran amine into the cochlear nucleus or dorsal root ganglion (DRG) at the second cervical segment (C2). Cochlear nucleus injections retrogradely labeled small ganglion cells in C2 DRG. C2 DRG injections produced anterograde labeling in the external cuneate nucleus, cuneate nucleus, nucleus X, central cervical nucleus, dorsal horn of upper cervical spinal segments, and cochlear nucleus. The terminal field in the cochlear nucleus was concentrated in the subpeduncular corner and lamina of the granule cell domain, where endings of various size and shapes appeared. Examination under an electron microscope revealed that the C2 DRG terminals contained numerous round synaptic vesicles and formed asymmetric synapses, implying depolarizing influences on the target cell. Labeled endings synapsed with the stalk of the primary dendrite of unipolar brush cells, distal dendrites of presumptive granule cells, and endings containing pleomorphic synaptic vesicles. These primary somatosensory projections contribute to circuits that are hypothesized to mediate integrative functions of hearing.

Acoustic Stimulation↗
PubMed1992

Bidirectional signals between Trypanosoma brucei brucei and dorsal root ganglion neurons.

The extracellular haemoflagellate Trypanosoma brucei brucei releases a factor, which can induce CD8+ T-cells to produce interferon-gamma. Interferon-gamma derived from these cells promotes proliferation of the trypanosomes. We now report that these trypanosomes can interact with small neurons in cultures of rat dorsal root ganglia, which contain an interferon-gamma like immunoreactive molecule. Cultures of dorsal root ganglia were able to promote the proliferation and survival of the trypanosomes and this growth promoting effect was blocked by monoclonal antibodies against the trypanosome-derived lymphocyte triggering factor, interferon-gamma and CD8+ and by Fab-fragments of these antibodies. Living trypanosomes and the factor induced an increase in expression of major histocompatibility complex class I antigens in the cultures; this induction was blocked by Fab fragments of the interferon-gamma antibody, indicating that it is mediated by release of the neuronal interferon-gamma-like immunoreactive molecule. These data suggest, that the interferon-gamma-like immunoreactive molecule in small dorsal root ganglion neurons mimics certain physiological effects of lymphocyte derived interferon-gamma. Furthermore, the trypanosomes and small sensory neurons seem to interact bidirectionally by release of the trypanosome-derived lymphocyte triggering factor and the neuronally derived interferon-gamma-like molecule, whereby, perhaps, neuronal disturbances may be elicited and trypanosome proliferation regulated.

Animals↗
PubMed1996

Proximally evoked soleus H reflexes in the evaluation of axonal neuropathy.

It is sometimes difficult to differentiate physiologically distal axonopathy from proximal root or nerve disease. Standard soleus H reflexes evoked by distal tibial nerve stimulation at the popliteal fossa are often absent in both syndromes. In this study we distinguish the two by the presence or absence of soleus H reflexes evoked by proximal sciatic nerve stimulation at the gluteal fold. In 12 normal subjects maximum H reflex amplitudes evoked by distal tibial and proximal sciatic stimulation were essentially equal. In 12 patients with suspected distal polyneuropathy, proximal but not distal stimulation evoked H reflexes. By contrast, in 10 patients with lumbosacral root or proximal nerve disease, both proximal and distal stimulation failed to elicit H reflexes. In 2 patients with lower motor neuronopathy, low but comparable amplitude H reflexes were evoked at both sites. We conclude that the presence of a proximally evoked soleus H reflex may provide specific evidence of distal axonopathy when standard soleus H reflexes are absent.

Adult↗
PubMed2004

A method for intraoperative microneurographic recording of unitary activity in the trigeminal ganglion of patients with trigeminal neuralgia.

The etiology of trigeminal neuralgia appears to be vascular compression of the nerve at the root entry zone. However, the physiologic mechanism of trigeminal neuralgia remains uncertain. To gain insight into the pathophysiology of the disorder, we developed a method for intraoperative microneurographic recordings from the trigeminal ganglion of patients with trigeminal neuralgia. The recordings are performed immediately prior to standard percutaneous trigeminal gangliolysis for pain relief. Spontaneous or evoked single- and multi-unit action potential activity can be recorded and the location of receptive fields determined. The method should facilitate the testing of hypotheses concerning the origin of this unique pain disorder.

Action Potentials↗
PubMed2001

Cloning and characterization of leaf senescence up-regulated genes in sweet potato.

Genes that are expressed during leaf senescence in sweet potato (Ipomoea batatas, cv. Tainong 57) were identified by the isolation of cDNA fragments with the mRNA differential display method. Eight senescence-associated cDNA clones for mRNAs differentially expressed during leaf senescence were obtained and characterized. Northern blot analysis indicated that all these clones represented genes that are up-regulated during natural leaf senescence. Among them, five cDNA clones have been obtained in full length by screening a senescing leaf cDNA library or by performing rapid amplification of cDNA ends. DNA and protein database searches revealed that clones SPA15 and SPC9 encode proteins of unknown function. The other six clones SPG31, SPC20, SPG27, SPC25, SPC15 and SPC1 showed significant sequence homology to known genes encoding a cysteine proteinase, isocitrate lyase, S-adenosylmethionine decarboxylase, cysteine proteinase inhibitor and metallothionein-like type I protein. The gene expression patterns represented by SPG31, SPG27 and SPA15 were found to be highly specific in senescing leaves. The corresponding transcripts for SPG31, SPG27 and SPA15 were below detectable levels in other organs such as flowers, stems, roots and tubers. The possible physiological roles of these gene products in the leaf senescence process are discussed.

Journal Article↗
PubMedDate not supplied

Peripheral nerve grafting in the spinal cord: a histological and electrophysiological study.

Excision of the dorsal columns was used to create a lesion in the spinal cord. The defect was bridged using a peripheral nerve graft. Silver staining showed the grafts being invaded by axons. Neuronal tracing by injecting horseradish peroxidase into the graft showed the origin of these fibres to be in dorsal root ganglia and in the grey matter of the lumbar cord. All of the animals studied showed horseradish peroxidase staining of neurones in the grey matter of the lumbar cord caudal to the graft. Five of the animals had staining of the dorsal root ganglion cells. Electro-physiological assessment was performed 5 to 6 months following the grafting procedure. Evoked potentials were recorded from the graft in six animals and from the dorsal columns above the graft in six animals.

Animals↗
PubMed2005

Gravitropism in leaves of Arabidopsis thaliana (L.) Heynh.

In higher plants, stems and roots show negative and positive gravitropism, respectively. However, current knowledge on the graviresponse of leaves is lacking. In this study, we analyzed the positioning and movement of rosette leaves of Arabidopsis thaliana under light and dark conditions. We found that the radial positioning of rosette leaves was not affected by the direction of gravity under continuous white light. In contrast, when plants were shifted to darkness, the leaves moved upwards, suggesting negative gravitropism. Analysis of the phosphoglucomutase and shoot gravitropism 2-1 mutants revealed that the sedimenting amyloplasts in the leaf petiole are important for gravity perception, as is the case in stems and roots. In addition, our detailed physiological analyses revealed a unique feature of leaf movement after the shift to darkness, i.e. movement could be divided into negative gravitropism and nastic movement. The orientation of rosette leaves is ascribed to a combination of these movements.

Arabidopsis↗
PubMed1997

Growth, leaf anatomy, and physiology of Populus clones in response to solar ultraviolet-B radiation.

We compared the physiological and morphological responses of rooted cuttings of Populus trichocarpa Torr. & Gray and P. trichocarpa x P. deltoides Bartr. ex Marsh. grown in either near-ambient solar ultraviolet-B (UV-B; 280-320 nm) radiation (cellulose diacetate film) or subambient UV-B radiation (polyester film) for one growing season. Midday biologically effective UV-B radiation was 120.6 and 1.6 mJ m(-2) s(-1) under the cellulose diacetate and polyester films, respectively. Gas exchange, leaf chlorophyll, light harvesting efficiency of photosystem II, and foliar UV-B radiation-absorbing compounds (i.e., flavonoid derivatives) were measured in expanding (leaf plastochron index (LPI) 5), nearly expanded (LPI 10), and fully expanded mature (LPI 15) leaves of intact plants of plastochron index 30 to 35. Plants were then harvested and height, diameter, biomass allocation and leaf anatomical attributes determined. Net photosynthesis, transpiration, and stomatal conductance were significantly greater in mature leaves exposed to subambient UV-B radiation than in mature leaves exposed to near-ambient UV-B radiation. Concentrations of UV-B radiation-absorbing compounds (measured as absorbance of methanol-extracts at 300 nm) were significantly greater in mature leaves exposed to near-ambient UV-B radiation than in mature leaves exposed to subambient UV-B radiation. The UV-B radiation treatments had no effects on chlorophyll content or intrinsic light harvesting efficiency of photosystem II. Height, diameter, and biomass were not significantly affected by UV-B radiation regime in either clone. Leaf anatomical development was unaffected by UV-B radiation treatment in P. trichocarpa x P. deltoides. For P. trichocarpa, leaf anatomical development was complete by LPI 10 in the near-ambient UV-B radiation treatment, but continued through to LPI 15 in the subambient UV-B radiation treatment. Mature leaves of P. trichocarpa were thicker in the subambient UV-B radiation treatment than in the near-ambient UV-B radiation treament as a result of greater development of palisade parenchyma tissue. We conclude that exposure to near-ambient UV-B radiation for one growing season caused shifts in carbon allocation from leaf development to other pools, probably including but not limited to, UV-B absorbing compounds. This reallocation curtailed leaf development and reduced photosynthetic capacity of the plants compared with those in the subambient UV-B radiation treatment and may affect growth over longer periods of exposure.

Journal Article↗
PubMed2006

Brownian motion of nucleated cell envelopes impedes adhesion.

We demonstrate that composite envelopes of nucleated cells exhibit pronounced short wavelength (<or=0.5 microm) bending excitations of approximately 10 nm root mean square amplitudes at physiological temperatures, which impede strong adhesion due to entropic repulsion forces. Quantitative microinterferometric analysis of the dynamic cell surface roughness of macrophages in terms of the theory of statistical surfaces suggests that the membrane excitations are mainly thermally driven Brownian motions (although active driving forces may contribute substantially). We determine the effective bending modulus of the cell envelope (approximately 1000kBT), the cortical tension (approximately 10(-4) N m-1), and the work of adhesion (approximately 10(-5) J m-2).

Animals↗
PubMed1994

Alterations of auxin perception in rolB-transformed tobacco protoplasts. Time course of rolB mRNA expression and increase in auxin sensitivity reveal multiple control by auxin.

Expression and physiological effects of the root-inducing rolB gene of Agrobacterium rhizogenes T-DNA were studied simultaneously in tobacco (Nicotiana tabacum) mesophyll protoplasts. The kinetic study of the expression of rolB mRNA following exogenous auxin application showed that auxin transiently stimulated rolB expression, with mRNA levels starting to accumulate 6 to 9 h after auxin was supplied and increasing 300-fold after 12 to 18 h. The parallel study of the auxin sensitivity of rolB-transformed protoplasts, as assayed by their electrical response to the hormone, showed that the auxin treatment generated an increase in sensitivity by a factor of up to 100,000, whereas in untransformed protoplasts the same auxin treatment induced an increase in auxin sensitivity that never exceeded 30- to 50-fold. This reflects a strong cooperative effect of auxin and rolB in transformed protoplasts. Surprisingly, the maximal increase in sensitivity was observed several hours before the maximal accumulation of rolB mRNA, suggesting that the dramatic control of auxin sensitivity by auxin in rolB-transformed protoplasts requires only low levels of rolB expression. Antibodies directed against ZmER-abp1, the major auxin-binding protein from maize, differentially altered the auxin sensitivity of the electrical response of rolB-transformed and normal protoplasts. This suggests that alterations of the auxin reception-transduction pathway at the plasma membrane of rolB-transformed protoplasts may account for their increased auxin sensitivity.

Agrobacterium tumefaciens↗
PubMed1980

Auxin Transport Inhibitors: IV. EVIDENCE OF A COMMON MODE OF ACTION FOR A PROPOSED CLASS OF AUXIN TRANSPORT INHIBITORS: THE PHYTOTROPINS.

The more active members of a proposed class of auxin transport inhibitors have been shown to have the ability to inhibit the active movement of auxin at concentrations where they have little effect on auxin action and no significant auxin activity. They have also been shown to give rise to characteristic biphasic dose-response curves on cress root growth. Based on these physiological similarities and other common physiological properties, it is concluded that they may achieve their effects by a common mode of action which differs from that of other known auxin transport inhibitors. It is suggested that the name "phytotropins" be given to the class of auxin transport inhibitors now defined by a similar mode of action and common chemical properties.

Journal Article↗
PubMed1995

Further evidence of incomplete neural control of muscle properties in cat tibialis anterior motor units.

To examine the influence of a motoneuron in maintaining the phenotype of the muscle fibers it innervates, myosin heavy chain (MHC) expression, succinate dehydrogenase (SDH) activity, and cross-sectional area (CSA) of a sample of fibers belonging to a motor unit were studied in the cat tibialis anterior 6 mo after the nerve branches innervating the anterior compartment were cut and sutured near the point of entry into the muscle. The mean, range, and coefficient of variation for the SDH activity and the CSA for both motor unit and non-motor unit fibers for each MHC profile and from each control and each self-reinnervated muscle studied was obtained. Eight motor units were isolated from self-reinnervated muscles using standard ventral root filament testing techniques, tested physiologically, and compared with four motor units from control muscles. Motor units from self-reinnervated muscles could be classified into the same physiological types as those found in control tibialis anterior muscles. The muscle fibers belonging to a unit were depleted of glycogen via repetitive stimulation and identified in periodic acid-Schiff-stained frozen sections. Whereas muscle fibers in control units expressed similar MHCs, each motor unit from self-reinnervated muscles contained a mixture of fiber types. In each motor unit, however, there was a predominance of fibers with the same MHC profile. The relative differences in the mean SDH activities found among fibers of different MHC profiles within a unit after self-reinnervation and those found among fibers in control muscles were similar, i.e., fast-2 < fast-1 < or = slow MHC fibers.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗