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Biomedical subjects

R Walden

Publications and source records attributed to R Walden.

At least 37 records · Page 2Linked to original sources
PubMed1996

Transaxial gunshot injuries.

OBJECTIVE: To define the clinical characteristics of gunshot injuries across the truncal midline (transaxial injuries). DESIGN: A retrospective case-control study MATERIALS AND METHODS: Analysis of a consecutive series of 223 patients with gunshot injuries to the torso treated at one trauma center. Sixty-three patients with transaxial injuries were compared to 148 patients with unilateral bullet trajectories. MAIN RESULTS: The incidence of cardiac (8%), vascular (17%), and spinal (29%) injuries and the mortality rate (29%) were significantly higher among the 63 patients with transaxial injuries compared with 148 patients with unilateral injuries. Initial operative access to the wrong visceral cavity (10%), missed injuries (14%), and early reoperations (19%) were also more common in the transaxial group. CONCLUSIONS: A transaxial bullet trajectory identifies a distinct injury pattern associated with a high incidence of major visceral damage, intraoperative misadventures, and very high mortality.

Abdominal Injuries↗
PubMed1995

Noninvasive evaluation of microcirculatory hemodynamic changes during hemorrhage followed by saline or blood transfusion.

The purpose of the study was to examine the ability of a system combining laser Doppler flowmetry (LDF), photoplethysmograph (PPG), and transcutaneous oxygen tension (tc-PO2) to follow changes in the microcirculation during hemorrhage and following blood or saline return, and to test the hypothesis that such changes precede and might predict changes in the systemic blood pressure. Measurements were performed on the skin of anesthetized rabbits (n = 10) during mild (0-8%), moderate (9-24%), and severe (25-30% of blood volume) hemorrhage, and following complete volume restitution by blood or saline. We found the following: 1) hemorrhage caused typical changes in the LDF, PPG, and tc-PO2 signals that could be formulated by mathematical models, 2) these signals identified blood as being more efficient than saline for volume restitution following hemorrhage, and 3) microcirculatory changes precede and might predict systemic hemodynamic events.

Acute Disease↗
PubMed1994

Auxin inducibility and developmental expression of axi 1: a gene directing auxin independent growth in tobacco protoplasts.

We describe the characterization of axi 1, a tobacco gene isolated by activation T-DNA tagging which apparently plays a role in auxin action. Upon deregulated expression, axi 1 confers on protoplasts the ability to grow in culture not only in the absence of auxin but also in high auxin concentrations where maximal frequencies of cell division are not observed in wild-type protoplasts. In wild-type plants axi 1 is transcribed principally in root tissue. In the tagged plant line, axi 159, axi 1 RNA can be detected in all tissues tested. Freshly isolated wild-type protoplasts require auxin for the accumulation of detectable levels of axi 1 transcript and this precedes maximal levels of cell division. In contrast, axi 1 RNA appears in protoplasts isolated from axi 159 plants in the absence of auxin. axi 1 was localized to 6.2 kb of plant genomic DNA flanking the right T-DNA border sequence. axi 1 is interrupted by nine introns and in tobacco it is a member of a small gene family. Database searching reveals no similarity within the coding region with other genes. Sequences within the fourth intron are similar to those located in the non-coding regions of other plant genes, some of which are known to be auxin inducible. A DNA fragment containing the conserved sequence acts as an auxin responsive element in transient expression assays in wild-type protoplasts and this response is higher in axi 159 protoplasts. This suggests that auxin induced axi 1 expression may be mediated by a region contained within an intron sequence and that the axi 1 product might play a role in this induction.

Base Sequence↗
PubMed1994

Activation tagging: a means of isolating genes implicated as playing a role in plant growth and development.

Activation T-DNA tagging has been used to generate a variety of tobacco cell lines selected by their ability to grow either in the absence of auxin or cytokinin in the culture media, or under selective levels of an inhibitor of polyamine biosynthesis. The majority of the cell lines studied in detail contain single T-DNA inserts genetically co-segregating with the selected phenotype. While most of the plants regenerated from the mutant cell lines appear phenotypically normal, several display phenotypes which could be inferred to result from disturbances in the content, or the metabolism, of auxins and cytokinins, or polyamines. The tagging vector is designed to allow the isolation of tagged plant genes by plasmid rescue. Confirmation that the genomic sequence responsible for the selected phenotype has indeed been isolated is provided by PEG-mediated protoplast DNA uptake of rescued plasmids followed by selection for protoplast growth under the original selective conditions. Several plasmids have been rescued from the mutant lines which confer on transfected protoplasts the ability to grow either in the absence of auxin or cytokinin in the culture media, or under selective levels of an inhibitor of polyamine biosynthesis. This review describes the background to activation tagging and our progress in characterizing the genes that have been tagged in the mutant lines we have generated.

Cytokinins↗
PubMed1994

Hypothermic circulatory arrest for thoracic aneurysmectomy through left-sided thoracotomy.

PURPOSE: In an attempt to clarify the role of hypothermic circulatory arrest (HCA) in the management of complex aortic aneurysms operated on through the left thoracotomy, our technique of HCA and outcome were reviewed. METHODS: During a 21-month period, 15 (17%) of 87 aneurysms of the descending thoracic or thoracoabdominal aorta were operated on by HCA. Eleven patients had chronic aortic dissections (four type A and seven type B), two patients had atherosclerotic aneurysms, and one each had congenital or infected postoperative aneurysms. The use of HCA was planned before surgery in 14 patients. Indications included proximal aortic disease in 12 patients, making either clamping of the transverse aortic arch unsafe (eight patients) or necessitating replacement of the arch with a graft (four patients). Preoperative decision to use HCA was made in two additional patients, one with a ruptured aneurysm and another patient for spinal cord and visceral protection because of anticipated prolonged ischemia as a result of reoperation. Intraoperative technical difficulties prompted the use of HCA in only one patient. Deep hypothermia (15 degrees to 24 degrees C) was induced through partial cardiopulmonary bypass. Left-sided heart venting was necessary in five patients. Aortic replacement was limited to the descending thoracic aorta in five patients, whereas it involved the thoracoabdominal aorta in 10 patients. Four patients had associated replacement of the aortic arch. RESULTS: Three patients died (one of a ruptured aneurysm) during surgery or early after surgery (two of bleeding and one of left ventricular failure). All other patients awoke neurologically intact, but one patient had delayed onset of paraplegia. Another patient died 4 days after surgery of rupture of the ascending aorta. Eleven patients were perioperative survivors without significant morbidity. CONCLUSIONS: Hypothermic circulatory arrest is a valuable adjunct in the management of complex aortic aneurysms through left-sided thoracotomy. Its results warrant consideration of its selective use for spinal cord/visceral protection.

Adult↗
PubMed1994

ATP-dependent transport of tetraethylammonium by endosomes isolated from rat renal cortex.

During renal organic cation secretion by some species, intracellular concentrations greatly exceed the 10- to 15-fold ratio predicted by the potential-driven mechanism thought to mediate their basolateral uptake. Free cytoplasmic organic cation concentrations within the tubular cells might be decreased through sequestration within intracellular organelles. The data reported here show that endosomal vesicles isolated from rat renal cortex take up tetraethylammonium (TEA) by an ATP-dependent mechanism. Addition of 0.2-5 mM ATP to the medium stimulated uptake 5- to 10-fold at 5 min and 20-fold at 60 min. More than 80% of the ATP-dependent uptake was associated with an osmotically active space. The nonhydrolyzable ATP analogue, adenosine 5'-O-(3-thiotriphosphate), did not stimulate TEA uptake. Mg2+ and Cl- were required for stimulation. Uptake was inhibited by several organic cations, including TEA itself. Uptake was also inhibited by inhibitors of intravesicular acidification, e.g., monensin and N-ethylmaleimide. Furthermore, the ATP requirement could be bypassed by establishing a pH gradient (inside acidic). These data show that endosomal TEA accumulation is mediated by proton/TEA exchange and is driven by the pH gradient maintained by H(+)-adenosinetriphosphatase. This potent sequestration mechanism may play an important role in organic cation secretion.

Adenosine Triphosphate↗
PubMed1993

Genes involved in the control of growth and differentiation in plants.

The mechanisms underlying totipotency, the unique ability of isolated plant cells to regenerate into plants, offer developmental biology a unique challenge. While it has been recognised for some time that phytohormones, such as auxin and cytokinin, play a role in this process by inducing a variety of growth patterns in both isolated cells, unorganised callus and intact plants, the molecular basis of their action remains unknown. The molecular and biochemical analysis of the novel interaction between tumour-inducing soil bacteria and the wounded plant has provided a valuable insight into how plants respond to phytohormones. During tumour formation, the bacteria transfer to the genome of the host plant a variety of genes which either short circuit the normal pathways of accumulation of phytohormones or modify how the plant cell responds to them. In parallel to these studies, we have been investigating plant genes involved directly or indirectly in the mechanism of phytohormone action. Auxin-binding proteins (putative receptors) have been localised in various cellular locations and the genes encoding them are currently undergoing analysis. Recently, a novel form of T-DNA has been devised by which mutant plant cell lines can be generated which grow in culture in the absence of exogenously applied auxin. The tagged genes, which are in effect plant cellular proto-oncogenes, are likely to shed more light on how auxin serves to regulate growth and development.

Cell Differentiation↗
PubMed1993

Restoration of fertility by antisense RNA in genetically engineered male sterile tobacco plants.

Transgenic tobacco plants (Nicotiana tabacum L.) expressing the rolC gene of Agrobacterium rhizogenes under the transcriptional control of the 35S RNA promoter are male sterile. When these plants are genetically crossed with others containing the rolC gene linked in antisense orientation to the 35S RNA promoter, hybrid progeny display restoration of male fertility. Moreover, hybrid progeny are revertant for other features of the rolC phenotype, such as restoration of plant height, leaf pigment content and female fertility. The level of restoration of the characteristics of untransformed tobacco appeared to be independent of the steady-state level of antisense RNA. Addition of six transcriptional enhancer sequences upstream of the 35S transcriptional start region in the antisense construct led to a higher steady-state level of antisense RNA than that produced using a promoter linked to a single enhancer sequence. However no significant difference was observed in the level of attenuation of the rolC phenotype in the progeny of crosses with either one or six transcriptional enhancers linked to the antisense rolC gene. Antisense constructs comprising only 189 bp of the rolC 5' coding region appeared less efficient in attenuating the rolC phenotype than those including the whole rolC coding region as well as its 3' untranslated region. Furthermore, results from experiments on light-controlled rolC gene expression indicate that microsporogenesis is sensitive to rolC gene action during the early stages of flower development.

Bacterial Proteins↗
PubMed1993

Stenotic coiling and kinking of the internal carotid artery.

Between January 1979 and December 1991, 174 of a total of 2304 carotid reconstructions (7.5%) were performed in 166 patients for stenotic coiling or kinking of the internal carotid artery. There was a 1.4 male predominance and the mean age of the patients was 66.3 +/- 9.6 years (range 38 to 91 years). Seventeen patients (9.8%) were asymptomatic, 54 (31%) were symptomatic because of a previous stroke, and 103 (59.2%) had had transient ischemic attacks. The symptoms were hemispheric in 108 (62.1%) cases, ocular in 19 (10.9%), and vertebrobasilar in 30 (17.2%). The stenotic coiling or kinking was isolated in 35 (20.1%) cases and associated with other lesions of the internal carotid artery in 139 (79.9%). These included 119 atherosclerotic stenoses, 14 aneurysms, and six stenotic lesions due to fibromuscular dysplasia. Angioplasty of the carotid bifurcation was performed in 102 (58.6%) patients, associated with endarterectomy in 84 (48.3%) cases and with dilatation of dysplastic lesions in six (3.5%) cases. A bypass graft and resection and anastomosis of the carotid artery were performed in 36 (20.7%) patients each. There were four postoperative deaths (2.3%): two were due to neurologic causes, one to heart disease, and one to complications of an associated surgical procedure. Five patients (2.9%) had postoperative strokes and eight (4.6%) had transient ischemic attacks. At postoperative follow-up investigations four (2.3%) patients had carotid occlusions and 10 (5.7%) had morphologic abnormalities. At 5 years, actuarial survival was 80.97 +/- 8.8%, patency was 96.12 +/- 2.95%, and the ipsilateral stroke-free rate was 93.12 +/- 4.49%. Treatment of stenotic coiling or kinking of the internal carotid artery yields satisfactory results, comparable to those of endarterectomy, for isolated atherosclerotic carotid stenoses and is effective in the prevention of ipsilateral ischemic stroke.

Adult↗
PubMed1993

Intra-arterial thrombolytic therapy: a combined approach with angioplasty and/or minor surgery.

Low-dose intra-arterial treatment was performed in 124 patients who underwent a total of 142 procedures. The series included 87 occluded arteries and 55 occluded grafts. In only 29 instances (21%) was thrombolysis alone sufficient. In another 77 procedures (54%) the thrombolysis was followed by either angioplasty or minor surgery. In the remaining 36 treatments (25%) lysis of the occlusion failed. A successful end result of combined treatment was achieved in 67 of 77 (87%) procedures. Including the 29 patients in whom thrombolysis alone sufficed, a total of 96 of the 142 procedures (67%) were successful, with the overall success rate being better in grafts (78%) than in arteries (61%). The suprainguinal lesions had a significantly better response compared to the infra-inguinal ones. The evaluation of all procedures was done at the time of discharge from hospital. Complications were related either to local or systemic hemorrhage or distal embolization. Death related to treatment occurred in three patients.

Adult↗
PubMed1992

Activation of a plant gene by T-DNA tagging: auxin-independent growth in vitro.

A transferred DNA (T-DNA) tagging vector with the potential to produce dominant mutations was used with cocultured Agrobacterium tumefaciens and protoplasts to tag genes involved in the action of the plant growth substance auxin. Transgenic calli were selected for their ability to grow in the absence of auxin in the culture media. From one experiment, 12 calli that displayed this phenotype were recovered, of which 11 were able to regenerate into plants. In one plant studied in detail, protoplast division in the absence of auxin genetically cosegregated with a single T-DNA insert. A messenger RNA encoded by a 6.4-kilobase sequence of plant genomic DNA rescued from the mutant is overexpressed relative to untransformed plants. The genomic DNA, as well as a cognate complementary DNA, once transfected into protoplasts promote growth and cell division in vitro in the absence of exogenously added auxin.

Agrobacterium tumefaciens↗
PubMed1992

Laser Doppler flowmetry in lower extremity ischemia: application and interpretation.

The present study was undertaken in order to develop numerical criteria for the parameters of laser Doppler flowmetry-skin blood flow velocity and pulse wave amplitude in the evaluation of lower extremity ischemia. Fifty limbs of young healthy volunteers were examined in order to obtain baseline normal values. Patient population was divided into moderately ischemic (52 limbs) and severely ischemic (22 limbs), based on patients' complaints, physical examination, ankle-brachial indices, pulse volume recordings and arteriographies. Univariate comparison between the three groups of skin blood flow velocity and pulse wave amplitude at each time point were done by analysis of variance. Power of discrimination between degrees of ischemia was evaluated by computing sensitivity and specificity, based on skin blood flow velocity and pulse wave amplitude values at time points best for predicting the severity of disease by multiple regression analysis. Using cutoff points of < 31 for skin blood flow velocity and < 9 for pulse wave amplitude, a 96% sensitivity and 96% specificity were obtained in separating normal from ischemic limbs. Cutoff points of < 9 for skin blood flow velocity and < 4 for pulse wave amplitude discriminated with a 100% sensitivity and specificity between the moderately and severely ischemic limbs. We propose the use of laser Doppler flowmetry with local heating and reactive hyperemia, and the cutoff points stated above as an additional tool to evaluate lower extremity ischemia through assessment of cutaneous microcirculation.

Adult↗