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PubMedDate not supplied

Fatal delayed esophageal rupture following aortic clamping for treatment of Stanford type B dissection.

A 65-year-old man underwent a thromboexclusion operation for management of chronic Stanford type B dissecting aneurysm in 1991. However, long-term follow-up CT scans after the operation revealed that the ascending aorta gradually enlarged and was eventually complicated by recurrent aortic dissection. The patient complained of frequent bloody sputum, whereas chest roentogenography showed no pulmonary abnormalities. Subsequent swallow esophagogram demonstrated that the upper esophagus was deviated to the right and the middle esophagus was greatly compressed by the aortic clamp. Esophageal endoscopy showed a bloody inner surface and marked swelling of the middle esophagus. The patient eventually died of massive hematemesis in 2001. We describe the imaging features of unanticipated complications such as recurrent dissecting aneurysm or impending esophageal rupture. Furthermore, we discuss the cause of hematemesis and document that the aortic clamp migrated and resulted in development of a recurrent aneurysmal dissection, which in turn resulted in esophageal rupture with aneurysmal disruption.

Aortic Dissection↗
PubMed2003

Preexistence and evolution of imatinib mesylate-resistant clones in chronic myelogenous leukemia detected by a PNA-based PCR clamping technique.

Recently, various mutations within the Abl sequence have been described that negatively affect imatinib binding to Bcr/Abl resulting in cellular resistance of chronic myeloid leukemia (CML) cells. So far, little is known as to whether these mutations are preexisting or develop under imatinib therapy as current mutation analyses are limited by a low sensitivity of approximately 1:2 (50%) to 1:5 (20%). By combining peptide nucleic acid (PNA)-based DNA clamping with a fluorescence hybridization probe assay, we developed a new and highly sensitive technique for the detection of known mutations within the Bcr/Abl kinase domain. With this approach we investigated 19 cases of CML refractory to imatinib treatment before and during therapy. By clamping of wild-type Abl through PNA we could effectively enhance the detection sensitivity for the Bcr/Abl mutations Thr315Ile, Glu255Lys, and Tyr253His such that 1 mutant cDNA molecule could be detected in 500 negatives (0.2%). We observed in one case that a Gly255Lys mutation was detectable before treatment. By DNA analysis of buccal swaps, a genetic polymorphism could be excluded. In two cases clonal evolution of known mutations developed gradually under treatment. In another case an initially detectable Tyr253His mutation disappeared after therapy onset but was again observed after 6 weeks of imatinib treatment. Preexisting and evolving Bcr/Abl mutations associated with an unfavorable prognosis could be safely detected by the presented technique. This may facilitate risk stratification in CML and may serve as a model for individualized molecular monitoring and therapeutic strategies in other malignant diseases.

Adult↗
PubMed2004

Extrapericardial pulmonary vein clamp technique for pulmonary arteriovenous fistula: report of a case.

The major concern when operating on a patient with a neurologically symptomatic pulmonary arteriovenous fistula (PAVF) is how to prevent a thromboembolic event during surgery. We describe a new technique whereby the extrapericardial pulmonary vein is clamped before transecting the afferent and efferent vessels of the fistula. The potentially pooled clots that can form while manipulating lung are stopped by the clamp. Before the extrapericardial pulmonary vein is declamped, one of the drainage veins is incised halfway and the pooled blood containing the potential clots is completely washed out. We successfully performed segmentectomy using this technique in a 66-year-old man with chronic left hemianopia and a large PAVF in the left anteromedial and lateral basal segments, and no thromboembolic events occurred.

Aged↗
PubMed2006

Vascular closure stapler clip anastomosis decreases aortic cross-clamping time compared to interrupted nonabsorbable and running absorbable sutures in growing pigs.

The latest generation in titanium clip application systems, the vascular closure staples (VCS) system avoids intimal lesions and therefore minimizes the subsequent hyperplastic reaction, while at the same time enhancing distensibility and vascular growth. Moreover, VCS clips allow the surgeon to perform vascular anastomosis easily and faster than conventional suture. This system may become the option of choice for vascular reconstruction in pediatric surgery where, as in the case of aortic and transplant surgery, decreasing vascular occlusion times may influence the outcomes. The aim of this study was to determine whether VCS metallic clips would allow shorter anastomosis times than conventional interrupted polypropylene or running Dexon suturing in end-to-end anastomosis performed in the abdominal aorta of young pigs. Twenty-four domestic swine, 45 days old, were used for this study. All animals were subjected to an end-to-end anastomosis in the abdominal aorta using VCS clips, interrupted polypropylene, or running Dexon suture. Aortic cross-clamping time was significantly shorter in the VCS clips group (4.02 +/- 0.72 min), compared to interrupted polypropylene (21.89 +/- 1.93 min) or running Dexon (9.82 +/- 3.97 min) suture. VCS clips are easy to use, and therefore may aid surgeons to significantly decrease the time needed for performing an end-to-end anastomosis in the abdominal aorta, thus decreasing cross-clamping time when compared to interrupted polypropylene or running Dexon sutures.

Anastomosis, Surgical↗
PubMed1976

Intimal injury from arterial clamps.

Preliminary experimental data have been presented indicating that intimal injury of some degree is a virtually constant finding at the site of application of any arterial occluding clamp. These injuries vary from intimal distortion to complete fracture into the media of the vessel. The degree of injury appears directly proportional to the amount of pressure exerted through a given clamp. Atherosclerotic arteries are particularly subject to severe degrees of intimal injury. Preliminary observations suggest that heparin is not helpful in preventing platelet aggregation and initial thrombus formation at intimal injury sites. The problem of anticoagulation at such injury sites is being studied further.

Animals↗
PubMed1977

"Soft" angled bulldog clamp for carotid control.

A bulldog vascular clamp was modified to reduce both weight and clamping force, and to permit easy use in the control of delicate vessels such as the internal carotid artery during carotid endarterectomy. The final instrument (Codman and Shurtleff, Inc, Randolph, MA) retains a simple design.

Carotid Artery, Internal↗
PubMed1982

Maintenance of ligature tension by a single operator with simultaneous removal of a hemostatic clamp.

Two new techniques that enable a single operator to maintain ligature tension while removing a hemostatic clamp are described. With the first technique a needle holder is used to grasp one tail of the ligature and maintain tension while the hemostatic clamp is removed with the opposite hand. The second technique loops one end of the ligature over the flexed index finger while fixing both tails with the remaining fingers. By extending the finger, tension is maintained.

Constriction↗
PubMed1990

Semiconductor-controlled contour-clamped homogeneous electric field apparatus.

The design and construction of a transistor-driven hexagonal contour-clamped homogeneous electric field (CHEF) apparatus is discussed in detail. The addition of computer control of pulsed-field timings and experiment duration gives rise to an efficient electrophoresis tool designed to achieve separation of DNA molecules in different size groupings. In particular, pulse time regimes which lead to the monotonic separation of DNA molecules ranging from 90 kbp to over a megabase pair are demonstrated. Theoretical treatment of electric field clamping with transistor-driven multiple electrodes is supported by measurements and by the actual performance of electrophoretic separation of yeast chromosomes. The large sample capacity of gels run in this apparatus coupled with the modest power requirements necessary to provide a homogeneous electric field offer significant advantages over earlier CHEF designs.

Buffers↗
PubMed1991

Separation of large DNA by a variable-angle contour-clamped homogeneous electric field apparatus.

A device for separating large DNA molecules by pulsed field electrophoresis is described. Based on the principles of contour-clamped homogeneous electric fields (CHEF), it uses feedback to clamp voltages in a square electrode array, which is compact and inexpensive to construct, adaptable to computer control, and reorients the electric field by arbitrary angles. To illustrate its capabilities, pulsed fields with reorientation angles ranging from 90 to 140 degrees were used to separate DNAs of 4.7 and 5.7 megabases by up to four band-widths in 20 h. The combination of accessible technology and complete control of the electric field should facilitate the search for ways to resolve even larger DNA.

Buffers↗
PubMed1991

Enzymatic determination of total CO2 in freeze-clamped animal tissues and plasma.

An enzymatic method for measuring total carbon dioxide content in freeze-clamped animal tissues is described. Total carbon dioxide content [TCO2] was defined as the sum of the dissolved CO2, the bicarbonate concentration, and the carbonate concentration. Tissue was extracted in 80% methanol, 20 mM 2-amino-2-methyl-1-propanol, pH 9.5 at 25 degrees C and homogenized in a 1.5-ml Sardstat screw-top test tube containing 0.5-mm glass beads and a minibead beater. Total CO2 was determined as bicarbonate/carbonate by monitoring the oxidation of NADH at 340 nm using the coupled assay of phosphoenolpyruvate carboxylase (EC 4.1.1.31) and malate dehydrogenase (EC 1.1.1.37). In the coupled assay system, 1 mumol of bicarbonate/carbonate consumed is equivalent to the oxidation of 1 mumol NADH at 340 nm. The assay medium comprised 50 mM 2-amino-2-methyl-1-propanol, pH 9.0 at 25 degrees C, 5 mM phosphoenolpyruvate (PEP), 0.25 mM NADH, 5 mM MgCl2, 5 mM mercaptoethanol, 0.02% bovine serum albumin, 10 mM oxamate, PEP carboxylase (0.5 units/ml), and malate dehydrogenase (0.5 units/ml). The total CO2 content measured in freeze-clamped rat heart, liver, brain, and skeletal muscle was 20.53 +/- 0.64, 17.34 +/- 0.67, 17.00 +/- 0.48, 16.06 +/- 0.53 mumol/g wet wt tissue, respectively (n = 5). The total CO2 in the crusher muscle of the lobster was found to be 5.0 +/- 0.33 mumol/g wet wt. Total CO2 was also enzymatically measured in arterial plasma from four chronically cannulated male wistar rats and was 24.65 +/- 1.81 mumol/ml plasma.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Warm heart surgery: experience with long cross-clamp times.

Although hypothermic cardioplegic arrest prolongs the period of ischemic arrest by reducing oxygen demands, it leaves the heart dependent solely on anaerobic metabolism for its energy demands and exposes it to the detrimental effects of hypothermia. Consequently, myocardial protection is compromised, and safe aortic occlusion time is limited to 120 minutes. As electromechanical arrest accounts for 90% of myocardial oxygen consumption, we hypothesized that an ideal state of the heart might be chemically arrested and perfused with warm blood, ie, aerobic arrest. We applied this approach to myocardial protection in 308 consecutive procedures. To assess the adequacy of this method, we reviewed the results in a group of 22 patients in whom the aortic cross-clamp time was, of necessity, greater than or equal to 3 hours (mean time, 204 minutes; range, 180 to 393 minutes). Nineteen of the patients represented a high operative risk with grade 3 or 4 left ventricular function and New York Heart Association class III or IV. All hearts resumed spontaneous normal sinus rhythm without defibrillation, and 21 patients were easily weaned from bypass within minutes of removal of the aortic cross-clamp without inotropic or intraaortic balloon pump support. Mortality was 4.5%, low-output syndrome occurred in 4.5%, and there were no perioperative myocardial infarctions. Our results suggest that warm aerobic arrest is safe and effective in prolonged high-risk procedures, virtually eliminating the period of ischemia, limiting the period and injury of reperfusion, and abolishing the detrimental effects of hypothermia.

Aged↗
PubMed1992

Normothermic cardioplegia: is aortic cross-clamping still synonymous with myocardial ischemia?

The enthusiastic clinical reports on normothermic blood cardioplegia contrast with the paucity of data on the myocardial metabolic effects of this technique. The present study was therefore designed to assess whether normothermic blood cardioplegia really provides an aerobic environment during aortic cross-clamping. Thirty-one patients undergoing coronary (16 patients), valve (13 patients), and transplantation (2 patients) procedures were given continuous normothermic blood cardioplegia through the coronary sinus. Myocardial metabolism was assessed either immediately before aortic unclamping (16 patients) by collecting blood simultaneously from the cardioplegia infusion line and the aortic effluent or during reperfusion (15 patients) by collecting blood simultaneously from the radial artery and the coronary sinus. All samples were assayed for markers of anaerobiosis (blood gases, lactates), leukocyte activation (elastase), and lipid peroxidation (malondialdehyde, vitamin E). At the end of arrest, oxygen extraction was low, whereas the production of lactates was small, thereby suggesting the efficacy of normothermic blood cardioplegia in maintaining a predominantly aerobic metabolism. This was confirmed by postarrest data, as oxygen extraction measured immediately after cross-clamp removal was unchanged from prearrest values, whereas lactate metabolism yielded transient and limited production followed by prompt recovery of normal extraction patterns. There was no release of elastase from the myocardium, which suggests adequate protection of the coronary endothelium from ischemic injury and the related increase in leukocyte activation. Likewise, postarrest coronary sinus concentrations of malondialdehyde and vitamin E were identical to the respective arterial concentrations, thereby ruling out the occurrence of intramyocardial lipid peroxidation at the time of reperfusion.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1990

"Clamping" actin in polymerized form in electro-permeabilized neutrophils inhibits oxidase activation.

Electro-permeabilized neutrophils take-up small membrane-impermeant molecules into their cytoplasm, yet retain the ability to activate their oxidase and to transiently polymerize actin in response to f-met-leu-phe (fmlp). Using this system phalloidin was introduced into the cytosol in order to determine whether polymerization of actin affects oxidase activation. Cytosolic phalloidin prevented the depolymerization of actin following stimulation with fmlp, which was consequently "clamped" in the polymerized form during oxidase activation. Under these conditions oxidase activation was inhibited, the extent of inhibition being related to the level of polymerization at which the actin was "clamped". It was concluded that the actin polymerization which accompanies stimulation with fmlp interacts with other intracellular signals to limit oxidase activation.

Actin Cytoskeleton↗
PubMed1981

Voltage clamp study of cat spinal motoneurons during strychnine-induced seizures.

Cat spinal motoneurons were examined by the technique of somatic voltage clamp during strychnine-induced spinal seizures. No clear alteration of voltage-dependent ionic currents was required in order for typical strychnine-induced paroxysmal depolarization shifts (PDSs) to develop in contrast to results previously obtained during penicillin-induced spinal seizures. Voltage clamp of evoked and spontaneous PDSs indicates these are generated by a synchronized mixture of excitatory and inhibitory synaptic currents wih excitation predominating.

Animals↗
PubMed1987

Whole cell voltage clamp recordings from cultured neurons of the supraoptic area of neonatal rat hypothalamus.

Whole-cell voltage and current clamp recordings were made from cultured neurons from the hypothalamic supraoptic area of neonatal rats. These neurons fired spontaneous Na+-action potentials, appearing as mixed Na+/K+-currents in voltage clamp. Isolated Na+-currents (less than 3 nA) were rapidly activated and inactivated during positive potential pulses from -80 mV. Two voltage-activated Ba2+-currents (less than 1 nA) were also recorded. These techniques offer a promising new approach for studying the striking electrical behavior of cultured hypothalamic neurons.

Action Potentials↗
PubMed1987

Voltage-clamp studies of the inhibition of gamma-aminobutyric acid response by glucocorticoids in bullfrog primary afferent neurons.

Acute effects of glucocorticoids on the response to gamma-aminobutyric acid (GABA) were examined in primary afferent neurons in bullfrog spinal ganglia, using intracellular and voltage-clamp recording techniques. Prednisolone and hydrocortisone (5 microM to 1 mM) caused a dose-dependent decrease in the amplitude of GABA-induced depolarization, while having no effect on the membrane potential and resistance of the neuron. Prednisolone depressed the muscimol-induced depolarization. Nipecotic acid, a blocker of GABA uptake, did not influence the inhibitory action of prednisolone. Voltage-clamp analyses showed that the inward current induced by an iontophoretic application of GABA (GABA current) was suppressed by prednisolone and hydrocortisone. The depression of the GABA current is neither due to a blockage of open channels nor a facilitation of the desensitization of GABA receptors. Prednisolone shifted the dose-response curve of the GABA current downward. The double-reciprocal (Lineweaver-Burk) plot showed that the maximum GABA current was reduced by prednisolone, suggesting a non-competitive antagonism. These results suggest that glucocorticoids suppress the GABA-induced chloride current, decreasing the number of functional channels associated with GABAA receptor.

Afferent Pathways↗
PubMed1988

Effects of Na+ and Ca2+ gradients on intracellular free Ca2+ in voltage-clamped Aplysia neurons.

Selected neurons of the abdominal ganglion of Aplysia californica were voltage-clamped and intracellular free Ca [( Ca2+]i) and Na [( Na+]i) concentrations were monitored with ion selective microelectrodes. Reducing [Na+]o from 500 mM (normal seawater, NSW) to 5 mM resulted in a decrease of the potential measured by the Ca electrode (VCa). Increasing [Ca2+]o from 10 to 50 mM increased [Ca2+]i two-fold, keeping [Ca2+]o at 50 mM and decreasing [Na+]o to 5 mM still led to a decrease in VCa. With 100 mM [Ca2+]o, which also increased [Ca2+]i, decreasing [Na+]o increased VCa in two of the eight cells tested. This indicates that in normal or moderately high resting [Ca2+]i, Ca2+ extrusion by Na/Ca exchange (forward mode) is not essential for [Ca2+]i buffering. [Na+]i was 12.9 +/- 3.6 mM (S.E.M., n = 7) in NSW; reducing [Na+]o to 5 mM decreased [Na+]i to 2.0 +/- 1.1 mM (S.E.M.). Keeping [Na+]o at 5 mM and increasing [Ca2+]o from 10 to 20 mM further decreased [Na+]i to about 1.0 mM, evidence of Na/Ca exchange operating in the reverse mode. Attempts to increase [Ca2+]i by bath application of the Ca ionophores A23187, X537A, ionomycin or ETH 1001 resulted in no measurable change of the resting [Ca2+]i. Application of Ouabain caused an apparent increase in [Ca2+]i in two of the six cells tested. In cells injected with the metallochromic indicator arsenazo III (AIII), the rate of the falling phase of the AIII absorbance increase, following a voltage-clamp pulse, was significantly slower in 5 mM [Na+]o. This indicates that in its forward mode Na-Ca exchange is active in clearing large submembrane increases in [Ca2+]i.

Animals↗
PubMed1991

NMDA antagonists attenuate hypertension induced by carotid clamping in the rostral ventrolateral medulla of rats.

The purpose of these experiments were to study the interactions of N-methyl-D-aspartate (NMDA) with baroreceptor reflexes induced by transient carotid clamping. Adult male Sprague-Dawley rats were anesthetized with urethane. Bilateral common carotid artery occlusion resulted in a reversible and reproducible hypertension in the vagotomized animals. This hypertensive reaction was blocked by intraventricular injection of NMDA antagonists, such as 2-amino-7-phosphono-heptaneoate (AP-7) and phencyclidine (PCP). We also found that blood pressure-sensitive neurons of the rostral ventrolateral medulla (RVLM) could be classified into two groups, on the basis of their responses to norepinephrine given intravenously. Using pressure microejection and single unit recording, we observed that clamping of the common carotids resulted in excitation of type I neurons. This evoked excitation, similar to that induced by NMDA, was blocked by locally applied AP-7. However, the carotid occlusion-induced responses of type II neurons were not blocked by AP-7. In conclusion, the present data suggest that NMDA receptors are involved in hypertensive responses during carotid occlusion, perhaps involving a site in the rostral ventrolateral medulla.

2-Amino-5-phosphonovalerate↗