VAVD vacuum may cause bubble transgression in membrane oxygenators.

BACKGROUND:: Vacuum-assisted venous drainage (VAVD) is widely used to enhance venous blood return from patients undergoing cardiopulmonary bypass (CPB). This vacuum can accidentally reach the oxygenator of the heart-lung machine and draw gas bubbles into the blood. This is known as bubble transgression (BT) and may cause air emboli in the arterial blood line. In order to avoid BT and minimize the risk of patient injury, knowledge of oxygenator tolerance to vacuum load is critical. Thus, the main aim of this thesis was to investigate how much vacuum a membrane oxygenator can withstand before BT appears. METHODS:: We investigated four different adult oxygenators: Quadrox-i, Affinity Fusion, Capiox RX25 and Inspire 6M. They were tested in an in vitro setup where VAVD vacuum was allowed to reach the oxygenator through a non-occlusive roller pump. An ultrasonic clinical bubble counter, Gampt BCC 200, was used to count bubbles on the arterial line when the arterial pump was restarted. RESULTS:: We observed a significant increase in bubble count for two of the oxygenators, caused by -30 mmHg of VAVD vacuum in the blood reservoir (Affinity Fusion and Inspire 6M). Massive air ingress was shown in two of the oxygenators, caused by -30 mmHg of VAVD vacuum in the reservoir (Capiox RX25) and -40 mmHg of VAVD vacuum in the reservoir (Affinity Fusion). CONCLUSION:: VAVD vacuum may cause bubble transgression in an oxygenator. This was shown for all the oxygenators in this test. VAVD vacuum may cause visible massive air ingress in an oxygenator. This was shown for two of the oxygenators in this test (Capiox RX25 and Affinity Fusion). An alarm triggering on negative pressure in the oxygenator or a pressure relief valve might improve safety when using VAVD.

Heparin-coated cardiopulmonary bypass circuits selectively deplete the pattern recognition molecule ficolin-2 of the lectin complement pathway in vivo.

The complement system can be activated via the lectin pathway by the recognition molecules mannose-binding lectin (MBL) and the ficolins. Ficolin-2 exhibits binding against a broad range of ligands, including biomaterials in vitro, and low ficolin-2 levels are associated with increased risk of infections. Thus, we investigated the biocompatibility of the recognition molecules of the lectin pathway in two different types of cardiopulmonary bypass circuits. Bloods were drawn at five time-points before, during and postoperatively from 30 patients undergoing elective cardiac surgery. Patients were randomized into two groups using different coatings of cardiopulmonary bypass circuits, Phisio® (phosphorylcholine polymer coating) and Bioline® (albumin-heparin coating). Concentrations of MBL, ficolin-1, -2 and -3 and soluble C3a and terminal complement complex (TCC) in plasma samples were measured. Ficolin-3-mediated complement activation potential was evaluated with C4, C3 and TCC as output. There was no significant difference between the two circuit materials regarding MBL, ficolin-1 and -3. In the Bioline® group the ficolin-2 levels decreased significantly after initiation of surgery (P < 0.0001) and remained reduced throughout the sampling period. This was not seen for Phisio®-coated circuits. Ficolin-3-mediated complement activation potential was reduced significantly in both groups after start of operation (P < 0.0001), whereas soluble C3a and TCC in the samples were increased (P < 0.0001). Ficolin-2 was depleted from plasma during cardiac surgery when using heparin-coated bypass circuits and did not reach baseline level 24 h postoperation. These findings may have implications for the postoperative susceptibility to infections in patients undergoing extracorporeal circulation procedures.

Biocompatibility and pathways of initial complement pathway activation with Phisio- and PMEA-coated cardiopulmonary bypass circuits during open-heart surgery.

A randomized open-heart surgery study comprising 30 patients was undertaken to compare the biocompatibility of Phisio-(phosphorylcholine) and PMEA-(poly-2-methoxyethyl acrylate) coated cardiopulmonary bypass (CPB) circuits and to assess the initial complement pathway activation during open-heart surgery. Blood samples were obtained at five time points, from the start of surgery to 24 hours postoperatively. The following analyses were performed: haemoglobin, lactate dehydrogenase, leukocyte and platelet counts, myeloperoxidase and neutrophil-activating peptide-2, thrombin-anti-thrombin complexes, syndecan-1 and the complement activation products C1rs-C1-inhibitor complexes, C4bc, C3bc, C3bBbP and the terminal complement complex (TCC). No significant inter-group difference was found in any parameters, except for the concentration of TCC which was moderately lower in the PMEA group at termination of CPB. Complement activation during open-heart surgery was mainly mediated through the alternative pathway. In conclusion, PMEA- and Phisio-coated circuits displayed similar biocompatibility with respect to inflammatory and haemostatic responses during and after open-heart surgery.

In vitro and in vivo evaluation of Dideco's paediatric cardiopulmonary circuit for neonates weighing less than five kilograms.

The neonate cardiopulmonary bypass (CPB) circuit, including a KIDS D100 oxygenator (The Sorin Group, Mirandola, Italy) and a D130 arterial filter (The Sorin Group), was evaluated in vitro with respect to the removal of free micro gas bubbles. No gas bubbles > 40microm were measured after the arterial filter D130 upon manual introduction of 10 ml of air into the venous line or during the use of vacuum-assisted venous drainage (VAVD). The D130 arterial filter removed 88 % of gas bubbles < 40 microm during manual introduction of air into the venous line; however, only 50 % of gas bubbles < 40 microm were removed during the use of VAVD. The same CPB circuit was evaluated in vivo to compare with another CPB circuit, including a D901 oxygenator (The Sorin Group) and arterial filter D736 (The Sorin Group), in 155 neonates weighing < or =5 kg. The D100 circuit required significantly less priming volume than the D901 circuit. Postoperative haemoglobin was significantly higher, artificial ventilation time was significantly shorter and postoperative bleeding was significantly less in the D100 group. This neonate CPB circuit effectively removed the gas bubbles and required up to 37% less priming volume and, thus, decreased the need for blood transfusion.

Comparable biocompatibility of Phisio- and Bioline-coated cardiopulmonary bypass circuits indicated by the inflammatory response.

BACKGROUND: The biocompatibility of cardiopulmonary bypass surfaces has been improved by heparin and polymer surface modifications. The present study compared the effect of two such coatings on the inflammatory reactions after open heart surgery. METHODS: Thirty patients undergoing elective heart surgery were randomly assigned to receive one of two types of coated circuits: Bioline (n=15) or phosphorylcholine (Phisio, n=15). The platelet and leukocyte counts, neutrophil activation (myeloperoxidase), complement activation (C3a and TCC), concentrations of lactate dehydrogenase, 27 cytokines (including interleukins, chemokines and growth factors), thrombin-antithrombin complexes, and the endothelial cell marker syndecan-1 were analyzed at five predetermined time points until 24 hrs post operatively. RESULTS: Most measurements were comparable in both groups. However, myeloperoxidase was significantly higher in the Bioline group (p < 0.001). Postoperative lactate dehydrogenase concentrations were significantly higher in the Phisio group (p<0.01) and the maximal concentration of thrombin-antithrombin complexes 2 hours postoperatively tended to be higher in the Phisio group (p=0.08), consistent with a longer aortic cross-clamp and cardiopulmonary bypass time. CONCLUSIONS: The two circuits exhibited a comparable degree of in vivo biocompatibility.

Exon repetition in mRNA.

The production of different transcripts (transcript heterogeneity) is a feature of many genes that may result in phenotypic variation. Several mechanisms, that occur at both the DNA and RNA level have been shown to contribute to this transcript heterogeneity in mammals, all of which involve either the rearrangement of sequences within a genome or the use of alternative signals in linear, contiguous DNA or RNA. Here we describe tissue-specific repetition of selective exons in transcripts of a rat gene (SA) with a normal exon-intron organization. We conclude that nonlinear mRNA processing can generate tissue-specific transcripts.

Analysis of two capreomycin-resistance determinants from Streptomyces capreolus and characterization of the action of their products.

Two genes encoding capreomycin (Cp)-modifying enzymes have been isolated from the producing organism Streptomyces capreolus. Cp acetyltransferase (CAC), encoded by cac, is active against all four components of the Cp complex, whereas Cp phosphotransferase (CPH), the product of cph, is active against Cp components IA and IIA (and also the related antibiotic, Vm) but not against Cp IB or Cp IIB.

Increased expression of the SA gene in the kidney of the spontaneously hypertensive rat is localized to the proximal tubule.

OBJECTIVE: To identify the site of the increased expression of the SA gene in the kidney of the spontaneously hypertensive rat (SHR) compared with the Wistar-Kyoto (WKY) rat. METHODS: In situ hybridization of SHR and WKY rat kidney sections with a radioactively labelled rat SA complementary DNA probe. RESULTS: Compared with WKY rat kidney sections, the probe bound intensely to the SHR renal cortex. Binding was sensitive to pretreatment of the section with RNAase A. Microscopic examination after autoradiography showed the increased signal in the SHR to be localized over proximal tubules. Background signal was observed over glomeruli, distal tubules, interlobular arteries and afferent arterioles. CONCLUSIONS: The localization of the increased expression of the SA gene in the SHR kidney compared with the WKY rat kidney to the proximal tubule suggests that it might influence blood pressure through effects on tubular function. Several differences in proximal tubular function have already been described between the SHR and WKY rat, and the relationship of these to tubular SA gene expression now need to be investigated. However, in the absence of any known functions for the SA gene product it is also possible that it might act through entirely novel, still undefined mechanisms.

Expression and analysis of two gyrB genes from the novobiocin producer, Streptomyces sphaeroides.

A novobiocin producer, Streptomyces sphaeroides, contains two genes, designated gyrBS and gyrBR, that encode novobiocin-sensitive and -resistant DNA gyrase B proteins, respectively. The cloning of gyrBR was reported earlier; here, we describe the cloning of gyrBS. Both genes have been sequenced (the deduced products of gyrBS and gyrBR have M(r) values of 87.6K and 86.5K, respectively) and their transcripts have been mapped. Downstream of gyrBS, and co-transcribed with it, is the sole gyrA gene (encoding DNA gyrase A protein). By constructing hybrid gyrB genes, using fragments of gyrBS and gyrBR, a specific portion of the N-terminal domain of the gyrase B protein (corresponding to amino acid residues 134-256 of Escherichia coli gyrase B) has been implicated in the binding of novobiocin.

Interplay of novobiocin-resistant and -sensitive DNA gyrase activities in self-protection of the novobiocin producer, Streptomyces sphaeroides.

The novobiocin (Nb)-producing organism, Streptomyces sphaeroides, possesses two gyrB genes: gyrBS and gyrBR (encoding the DNA gyrase B subunit-the normal target for Nb) whose products differ in their response to the drug. Novobiocin-sensitive gyrase is the predominant form of the enzyme in this strain and is produced constitutively but at variable levels, whereas Nb-resistant gyrase appears when growth takes place in the presence of the drug. The promoter isolated from the Nb-resistance determinant responds sharply to changes in DNA topology, being activated when the (negative) superhelical density is reduced and vice versa when the supercoiling of DNA is increased. Thus, resistance to Nb in S. sphaeroides is induced by a reduction in DNA supercoiling due to the action of autogenous drug on the sensitive gyrase.

Cloning and characterization of a DNA gyrase B gene from Streptomyces sphaeroides that confers resistance to novobiocin.

A gyrB gene from Streptomyces sphaeroides, a producer of novobiocin, has been cloned in Streptomyces lividans, where it conferred resistance to novobiocin. The Streptomyces gyrB gene was sufficiently similar to a Bacillus subtilis gyrB probe to be specifically recognized during Southern analysis. Partial purification of DNA gyrase by affinity chromatography revealed the presence of two such activities (differing in their responses to novobiocin) in the clone. The product of the cloned gene, a novobiocin-resistant DNA gyrase B subunit, was identified in vitro by coupled transcription--translation as a 79-kd protein.