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Biomedical subjects

C E Mullins

Publications and source records attributed to C E Mullins.

At least 19 recordsLinked to original sources
PubMed2006

Influence of nematodes on resource utilization by bacteria--an in vitro study.

The positive influence of bacterial feeding nematodes on bacterial mediated processes such as organic matter mineralization and nutrient cycling is widely accepted, but the mechanisms of these interactions are not always apparent. Both transport of bacteria by nematodes, and nutritional effects caused by nematode N excretion are thought to be involved, but their relative importance is not known because of the difficulties in studying these interactions in soil. We developed a simple in vitro assay to study complex nematode/bacterial interactions and used it to conduct a series of experiments to determine the potential influence of nematode movement and nutritional effects on bacterial resource use. The system used bacterial feeding and nonfeeding insect parasitic nematodes, and luminescent bacteria marked with metabolic reporter genes. Both nutritional enhancement of bacterial activity and bacterial transport were observed and we hypothesize that in nature, the relative importance of transport is likely to be greater in bulk soil, whereas nematode excretion may have greater impact in the rhizosphere. In both cases, the ability of nematodes to enhance bacterial resource utilization has implications for soil components of biogeochemical cycling.

Animals↗
PubMed2006

Assessing the importance of genotype x environment interaction for root traits in rice using a mapping population II: conventional QTL analysis.

Modifying plant root systems is considered a means of crop improvement targeted to low-resource environments, particularly low nutrient and drought-prone agriculture. The identification of quantitative trait loci (QTLs) for root traits has stimulated marker-assisted breeding to this end, but different QTLs have been detected in different populations of the same species, and importantly, in the same population when grown in different experimental environments. The presence of QTL x environment interaction is implicated, and this must be characterised if the utility of the target QTLs is to be realised. Previous attempts to do this suffer from a lack of control over replicate environments and inadequate statistical rigour. The Bala x Azucena mapping population was grown in two replicate experiments of four treatment environments, a control, a low light, a low soil nitrogen and a low soil water treatment. After a 4 weeks growth, maximum root length, maximum root thickness, root mass below 50 cm, total plant dry mass, % root mass and shoot length were measured. A summary of the overall results is presented in an accompanying paper. Here, QTL analysis by composite interval mapping is presented. A total of 145 QTLs were detected, mapping to 37 discrete loci on all chromosomes. Superficial evidence of QTL x E (great difference in LOD score) was tested by single-marker analysis which confirmed QTL x E for five loci representing only five individual trait-loci interactions. Some loci appeared to be stable across environments. Some QTLs were clearly more or less active under low light, low nitrogen or drought. A few notable loci on chromosomes 1, 2, 3, 5, 7 and 9 are briefly discussed. Also discussed are some remaining statistical shortcomings that will be addressed in another companion paper.

Adaptation, Physiological↗
PubMed2006

Assessing the importance of genotype x environment interaction for root traits in rice using a mapping population. I: a soil-filled box screen.

Altering root system architecture is considered a method of improving crop water and soil nutrient capture. The analysis of quantitative trait loci (QTLs) for root traits has revealed inconsistency in the same population evaluated in different environments. It must be clarified if this is due to genotype x environment interaction or considerations of statistics if the value of QTLs for marker-assisted breeding is to be estimated. A modified split-plot design was used where a main plot corresponded to a separate experiment. The main plot factor had four treatments (environments), which were completely randomized among eight trials, so that each treatment was replicated twice. The sub-plot factor consisted of 168 recombinant inbreed lines of the Bala x Azucena rice mapping population, randomly allocated to the seven soil-filled boxes. The aim of the trial was to quantify QTL x environment interaction. The treatments were chosen to alter partitioning to roots; consisting of a control treatment (high-soil nitrogen, high light and high-water content) and further treatments where light, soil nitrogen or soil water was reduced singly. After 4 weeks growth, maximum root length (MRL), maximum root thickness, root mass below 50 cm, total plant dry mass (%), root mass and shoot length were measured. The treatments affected plant growth as predicted; low nitrogen and drought increased relative root partitioning, low-light decreased it. The parental varieties Bala and Azucena differed significantly for all traits. Broad-sense heritability of most traits was high (57-86%). Variation due to treatment was the most important influence on the variance, while genotype was next. Genotype x environment interaction was detected for all traits except MRL, although the proportion of variation due to this interaction was generally small. It is concluded that genotype x environment interaction is present but less important than genotypic variation. A companion paper presents QTL x environment analysis of data.

Chromosome Mapping↗
PubMed2003

Nematode-enhanced microbial colonization of the wheat rhizosphere.

The mechanisms by which seed-applied bacteria colonize the rhizosphere in the absence of percolating water are poorly understood. Without mass flow, transport of bacteria by growing roots or soil animals, particularly nematodes may be important. We used a sand-based microcosm system to investigate the ability of three species of nematodes (Caenorhabditis elegans, Acrobeloides thornei and a Cruznema sp.) to promote rhizosphere colonization by four strains of beneficial rhizobacteria. In nearly all cases, rhizosphere colonization was substantially increased by the presence of nematodes, irrespective of bacterial or nematode species. Our results suggest that nematodes are important vectors for bacteria rhizosphere colonization in the absence of percolating water.

Animals↗
PubMed2003

Intrastent sonotherapy in pulmonary vein restenosis: a new treatment for a recalcitrant problem.

A 2 year old boy developed recurrent pulmonary vein stenosis after surgical repair of infradiaphragmatic pulmonary venous connection. He had required implantation of stents in the left and right sided pulmonary veins at 7 and 13 months of age, respectively. By 2 years of age he had undergone three catheterisation procedures and two surgical procedures to treat recurrent pulmonary vein stenosis. His right ventricular pressure was suprasystemic and catheterisation showed severe neointimal proliferation of both left and right sided stents. At this time the stents were dilated by balloon with simultaneous intrastent sonotherapy. Three months later the patient's clinical improvement was significant, his right ventricular pressure had decreased, and Doppler velocity had decreased across both left and right sided stents.

Catheterization↗
PubMed2002

Use of the transseptal puncture in transcatheter closure of long tunnel-type patent foramen ovale.

Two patients with long tunnel-type patent foramen ovale presented for elective transcatheter closure following transient ischaemic attack and stroke. Right to left shunting was confirmed on transthoracic and transoesophageal echocardiography. A new technique that used a transseptal procedure was devised to enable closure of the tunnel-type patent foramen ovale using the CardioSEAL transseptal occluder to avoid "bunching up" of the device and residual transatrial shunting.

Adult↗
PubMed2001

Safety of magnetic resonance imaging immediately following Palmaz stent implant: a report of three cases.

Magnetic resonance imaging (MRI) can provide important information on patients with congenital heart defects. There is some reluctance to perform MRI acutely following intravascular stent implant, due to concerns of distortion or movement of the stent in the magnetic field. We report on three patients who underwent MRI evaluation less than 14 days following Palmaz stent implant in the pulmonary arteries and superior vena cava, with no acute adverse outcome or long-term problems.

Adult↗
PubMed2001

Reconstruction of stenotic or occluded iliofemoral veins and inferior vena cava using intravascular stents: re-establishing access for future cardiac catheterization and cardiac surgery.

OBJECTIVES: The study evaluated the safety and efficacy of stent reconstruction of stenotic/occluded iliofemoral veins (IFV) and inferior vena cava (IVC). BACKGROUND: Patients with congenital heart defects and stenotic or occluded IFV/IVC may encounter femoral venous access problems during future cardiac surgeries or catheterizations. METHODS: Twenty-four patients (median age 4.9 years) underwent implantation of 85 stents in 22 IFV and 6 IVC. Fifteen vessels were severely stenotic and 13 were completely occluded. Although guide wires were easily passed across the stenotic vessels, occluded vessels required puncture through the thrombosed sites using a stiff wire or transseptal needle. Once traversed, the occluded site was dilated serially prior to stent implantation. RESULTS: Following stent placement, the mean vessel diameter increased from 0.9 +/- 1.6 to 7.4 +/- 2.6 mm (p < 0.05). Twenty-one of 28 vessels had long segment stenosis/occlusion requiring two to seven overlapping stents. Repeat catheterizations were performed in seven patients (9 stented vessels) at mean follow-up of 1.6 years. Seven vessels remained patent with mean diameter of 6.4 +/- 2.0 mm. Two vessels were occluded, but they were easily recanalized and redilated. Echocardiographic follow-up in two patients with IVC stents demonstrated wide patency. In four additional patients, a stented vessel was utilized for vascular access during subsequent cardiac surgery (n = 3) and endomyocardial biopsy (n = 1). Therefore, 13 of 15 stented vessels (87%) remained patent at follow-up thus far. CONCLUSIONS: Stenotic/obstructed IFV and IVC may be reconstructed using stents to re-establish venous access to the heart for future cardiac catheterization and/or surgeries.

Angioplasty, Balloon↗
PubMed2001

Redilation of endovascular stents in congenital heart disease: factors implicated in the development of restenosis and neointimal proliferation.

OBJECTIVES: We sought to determine the incidence of and risk factors for the development of restenosis and neointimal proliferation after endovascular stent implantation for congenital heart disease (CHD). BACKGROUND: Risk factors for the development of restenosis and neointimal proliferation are poorly understood. METHODS: This was a retrospective review of patients who underwent endovascular stent redilation between September 1989 and February 2000. RESULTS: Of 368 patients who had 752 stents implanted, 220 were recatheterized. Of those 220 patients, 103 underwent stent redilation. Patients were classified into three groups: 1) those with pulmonary artery stenosis (n = 94), tetralogy of Fallot/pulmonary atresia (n = 72), congenital branch pulmonary stenosis (n = 9), status post-Fontan operation (n = 6), status post-arterial switch operation (n = 7); 2) those with iliofemoral venous obstruction (n = 6); and 3) those with miscellaneous disorders (n = 3). The patients' median age was 9.9 years (range 0.5 to 39.8); their mean follow-up duration was 3.8 years (range 0.1 to 10). Indications for stent redilation included somatic growth (n = 67), serial dilation (n = 27) and development of neointimal proliferation or restenosis, or both (n = 9). There was a low incidence of neointimal proliferation (1.8%) and restenosis (2%). There were no deaths. Complications included pulmonary edema (n = 1), hemoptysis (n = 1) and contralateral stent compression (n = 2). CONCLUSIONS: Redilation or further dilation of endovascular stents for CHD is effective as late as 10 years. The risk of neointimal proliferation (1.8%) and restenosis (2%) is low and possibly avoidable. Awareness of specific risk factors and modification of the stent implantation technique, including avoidance of minimal stent overlap and sharp angulation of the stent to the vessel wall and avoidance of overdilation, have helped to reduce the incidence of restenosis.

Adolescent↗
PubMed2001

Coronary artery fistula. Management and intermediate-term outcome after transcatheter coil occlusion.

During the last 2 decades, transcatheter occlusion of coronary artery fistulae has developed into a safe and effective therapy for children. This procedure avoids the need for open surgical repair and the attendant complications of cardiopulmonary bypass and median sternotomy. The long-term outcome in patients after transcatheter occlusion remains unknown. We describe the intermediate-term progress of 4 such patients after coil occlusion of coronary artery fistulae. Persistent coronary artery dilatation was present in all patients reviewed, as late as 4 years after occlusion.

Arteriovenous Fistula↗
PubMed2001

Three new applications of stent technology in a single patient.

The use of endovascular stents has become widely established in maintaining both arterial and venous patency in congenital heart disease. Stent implantation is now applied to pulmonary arterial stenoses, coarctation, pulmonary and systemic venous obstruction, and obstructed homografts and conduits, in both the pediatric and adult populations. The purpose of this report is to describe 3 new applications of stent technology: 1) double pulmonary artery stent implantation with simultaneous balloon dilation of a previously placed stent; 2) a new technique for traversing tight pulmonary arterial corners for stent delivery using the "sheath-within-sheath" method; and 3) a new technique for recannulation and stent implantation in unilateral femoral venous occlusion.

Adult↗
PubMed2001

Sizing of atrial septal defects to predict successful closure with transcatheter cardioSEAL device.

We conducted this retrospective study to compare methods for measuring atrial septal defects and to identify factors affecting echocardiographic measurement of such defects before transcatheter closure with the CardioSEAL'Septal Occluder. We reviewed the records of patients considered for device placement at our institution from January 1997 to April 1999. Atrial septal defect size was measured by transthoracic and transesophageal echocardiography; the stretched diameter was measured during catheterization by fluoroscopy and transesophageal echocardiography. The stretched-diameter fluoroscopic measurement was used for device size selection. Analysis of variance was used to calculate the effect of size, age, and size-by-age interaction. Thirty-one patients (3.3 to 72 years of age) underwent transthoracic and transesophageal echocardiography One patient was excluded from catheterization because of a 25-mm septal defect as indicated by transesophageal echocardiography (our maximum diameter, 15 mm). Thirty patients underwent transcatheter stretched-diameter sizing; 5 were excluded from device implantation because of defects >20 mm by stretched-diameter fluoroscopy (4) or septal length insufficient for device support (1). Implantation was successful in 23/25 patients; 2/23 had a residual shunt. In patients with available results (26/30), the stretched diameter was the same whether measured by stretched-diameter fluoroscopy or transesophageal echocardiography (P=0.007 R square=0.963). Compared with stretched-diameter fluoroscopy, precatheterization transthoracic and transesophageal echocardiography underestimated defect size by a mean of 22% and 13.2%, respectively. When data from those same tests were compared in defects of < or =0 mm and > 10 mm, transthoracic and transesophageal echocardiography were reliable predictors (P=0.003 and P=0.05, respectively) of stretched-diameter size in defects < or =0 mm.

Adolescent↗
PubMed2000

Transcatheter closure of surgical shunts in patients with congenital heart disease.

The aim of this study was to review contemporary techniques, devices, and results of transcatheter occlusion of surgical shunts in 2 pediatric cardiac programs. Closure of superfluous surgical shunts may reduce cardiac work and risk of endocarditis. Previous studies have shown that transcatheter closure of shunts is feasible, but have not demonstrated acceptable efficacy or safety. In addition, the performance of new techniques and devices has not been reviewed. Between 1993 and 1998, 18 patients with congenital heart disease underwent transcatheter closure of 19 Blalock-Taussig shunts. Detachable and standard Gianturco coils and Gianturco-Grifka vascular occlusion devices were employed. All 19 shunts had complete closure. Eight shunts had initial placement of detachable coils. Five shunts had stents placed that bridged the pulmonary end of the shunts. These 5 and 4 additional shunts had closure by standard coils. Two shunts were closed with Gianturco-Grifka devices. There were no complications, no embolizations, and no requirement for surgery precipitated by the procedures. This review of contemporary techniques, devices, and results suggests that transcatheter occlusion of surgical shunts is effective and safe.

Blood Vessel Prosthesis Implantation↗
PubMed2000

A technique to prevent newly implanted stent displacement during subsequent catheter and sheath manipulation.

We describe a novel technique to prevent the displacement or migration of a newly implanted stent as a consequence of any subsequent catheter and sheath manipulation during the same catheterization procedure. The technique involves reinflation of the dilation balloon within the stent immediately after implant followed by advancing the long delivery sheath carefully over the balloon as the balloon is slowly deflated within the stent. The technique was used successfully in 78 stents in 30 patients without stent dislodgment or migration.

Adolescent↗