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At least 1,585 records · Page 88Linked to original sources
PubMed1986

Calcium current in mouse eggs recorded with the tight-seal, whole-cell voltage-clamp technique.

The tight-seal, whole-cell recording technique has been used to voltage-clamp unfertilized eggs of the mouse. Good seal formation was obtained in a solution containing 20 mM Ca2+ and the transient inward Ca2+ current recorded. This technique offers several advantages over the conventional, two-microelectrodes voltage-clamp: improved signal to noise ratio; larger membrane-pipette seal resistance; possibility of very stable, long duration, recordings and possibility of controlling the intracellular medium. The main disadvantage of the technique, namely the rundown of channels due to loss of intracellular components, was not encountered in this preparation.

Animals↗
PubMedDate not supplied

Partial voltage clamping of Limulus ventral photoreceptor potentials: evidence of programmed conductance changes.

Light-initiated currents elicited by brief light stimuli from Limulus ventral photoreceptors bathed in normal sea water generally exhibit a smooth contour, although the unclamped receptor potential elicited by an identical light stimulus usually exhibits distinct C1 and C2 components. However, light-initiated currents obtained from cells exposed to chlorobutanol often exhibit two components. Data from such experiments indicate that peak C2 current is more strongly voltage dependent than peak C1 current, as in Limulus lateral eye retinular cells. The results of partial voltage clamp experiments with ventral photoreceptors in which the clamping episode terminated at different times during the receptor potential reveal relatively minor perturbations of the rebound receptor potential when compared with the unclamped control response. These findings suggest that the temporal pattern of the membrane conductance changes which underlie the receptor potential is determined prior to the occurrence of the receptor potential. It is likely that the program for these conductance changes is developed during the latent period of the receptor potential.

Animals↗
PubMed1990

Comprehensive detection of single base changes in human genomic DNA using denaturing gradient gel electrophoresis and a GC clamp.

We present a simple, efficient extension of denaturing gradient gel electrophoresis that allows the detection of nearly any sequence change in a defined fragment of DNA. The fragment can be obtained either by means of the polymerase chain reaction or by restriction digestion of genomic DNA. With restriction fragments of genomic DNA, sequence information is not required, and covalent modifications in genomic DNA that are lost in a PCR, such as methylation, are detectable. We describe how a GC clamp (an arbitrary, G+C-rich sequence of 30 to 60 bp) can be attached to a selected restriction fragment present in a digest of genomic DNA. The GC clamp alters the melting properties of the fragment; this change greatly increases the fraction of possible mutations that is detectable. In a 272-bp HaeIII fragment from the human beta-globin gene, we were able to detect 13 of 13 mutations tested in human genomic DNA. Four additional mutations in cloned plasmids were analyzed. The data agree with a simple theoretical model for DGGE, which predicts how two fragments, differing at a single (specified) base pair, are resolved in a gradient gel as a function of running time for the gel. The calculation assists in the design of probes and gel conditions that aid in the detection of sequence changes.

Base Composition↗
PubMed1993

Atrial fibrillation after coronary artery bypass grafting: a comparison of cardioplegia versus intermittent aortic cross-clamping.

Supraventricular tachyarrhythmias following coronary artery bypass grafting are a common cause of postoperative morbidity, with a reported incidence of 10-40%. Two techniques of myocardial protection were assessed to determine their influence on the occurrence of postoperative supraventricular tachyarrhythmias. Group I (n = 82) received cold potassium cardioplegia combined with topical hypothermia and systemic cooling to 28 degrees C. Group II (n = 88) were protected by intermittent aortic cross-clamping with a systemic temperature of 32 degrees C. The overall incidence of atrial fibrillation/flutter was 22.3%. No significant difference was detected in the incidence of clinically important atrial fibrillation/flutter between the two groups [21/82 (25.6%) in group I versus 17/88 (19.3%) in group II, P > 0.25]. There was a positive association with age: in patients over 60 years the incidence of arrhythmias (31.8%) was significantly greater than in those less than 60 years (12.9%), P < 0.01. Sex, cardiopulmonary bypass times, aortic cross-clamp times, number of coronary grafts, end-operative creatine kinase myocardial band isoenzyme, right coronary endarterectomy and perioperative myocardial infarction had no association with the occurrence of postoperative atrial tachyarrhythmias.

Atherectomy, Coronary↗
PubMed2004

Experimental studies on myocardial protection with intermittent cross-clamp fibrillation: additive effect of the sodium-hydrogen exchanger inhibitor, cariporide.

BACKGROUND: We previously showed that intermittent cross clamping with fibrillation affords myocardial protection equivalent to cardioplegic arrest. In this study, we examined whether cariporide (Aventis Pharma, Frankfurt, Germany), a specific sodium-hydrogen exchanger inhibitor, enhanced the protective effect of intermittent cross-clamp fibrillation (ICCF). METHODS: Isolated rat hearts were Langendorff-perfused (20 mins) with bicarbonate buffer and function (left ventricular developed pressure) measured. In each of three separate protocols that incorporated progressively longer ischemic durations, hearts were randomly allocated to one of three groups: group 1 was the control group with 40, 60, or 80 minutes of continuous global ischemia. Group 2 was the ICCF group with 4, 6, or 8 cycles of 10 minutes ICCF and 10 minutes of reperfusion in sinus rhythm. Group 3 was the ICCF plus cariporide group, which was the same as group 2, but also with 3 micromoles/L cariporide present in perfusate from 10 minutes before the ICCF cycles. Hearts were reperfused for 60 minutes with drug-free buffer and recovery (percentage of initial function) was measured. Hearts were maintained at 37 degrees C throughout the protocols. In protocol 3 (80 minutes ischemia per 8 cycles of ICCF), creatine kinase leakage (myocardial injury) and triphenyl tetrazolium chloride staining (myocardial viability) were also measured. Protocols 1, 2, and 3 had n = 8 hearts, n = 6 hearts, and n = 6 hearts in each group, respectively. RESULTS: In the three protocols, the recoveries of left ventricular developed pressure in the control group, the ICCF group, and the ICCF plus cariporide group, respectively, for protocol 1 were: 26% +/- 3%, 70% +/- 2% (p < 0.05 vs the control group) and 74% +/- 2% (p < 0.05 vs the control group), respectively. For protocol 2 these were: 16% +/- 2%, 55% +/- 1% (p < 0.05 vs the control group), and 70% +/- 3% (p < 0.05 vs the control and ICCF groups), respectively. For protocol 3 these were: 8% +/- 2%, 41% +/- 3% (p < 0.05 vs the control group), and 63% +/- 2% (p < 0.05 vs the control and ICCF groups), respectively. Recovery of left ventricular end-diastolic pressure mirrored that of left ventricular developed pressure in all protocols. In protocol 3, total creatine kinase leakage (international units per gram wet weight) was 88 +/- 12, 47 +/- 4 (p < 0.05 vs the control group), and 17 +/- 1 (p < 0.05 vs the control and ICCF groups), respectively, and triphenyl tetrazolium chloride staining (arbitrary units per gram wet weight) was 0.17 +/- 0.04 in the control group, 0.39 +/- 0.04 (p < 0.05 vs the control group) in the ICCF group, and 0.47 +/- 0.08 (p < 0.05 vs the control group) in the ICCF plus cariporide group, respectively. CONCLUSIONS: Sodium-hydrogen exchanger inhibition with cariporide enhances the myocardial protection afforded by ICCF, with the additive benefit becoming more apparent with increasing severity of the ischemic insult. Sodium-hydrogen exchanger inhibition may provide a significant protective reserve during ICCF, particularly when longer procedures are required.

Animals↗
PubMed2005

The off-pump Fontan procedure by simply cross-clamping the inferior caval vein.

BACKGROUND: We previously used the Fontan procedure, when applicable, by placing a temporary bypass from the inferior vena cava to the atrium. Alternatively, we have striven to achieve the procedure even without use of a temporary bypass in patients having collaterals between the inferior vena cava and the superior vena cava, so as to simplify the procedure. The azygous vein was intentionally left patent at the bidirectional Glenn procedure in the most recent 9 patients, expecting reasonable venovenous communication at Fontan completion. Surgical results will be described for the preliminary experience. METHODS: Since 2001, this alternative technique has been attempted in 34 patients undergoing the staged Fontan procedure, and eventually used in 22. Duration between the staged procedures was 4 to 108 months (median, 10 months). We considered that the technique was feasible unless femoral venous pressure exceeded 20 mm Hg immediately after cross-clamping the inferior vena cava. Although catheterization before the Fontan completion illustrated development of venovenous collaterals in 14 patients, oxygen saturation remained greater than 80% throughout the period of the bidirectional Glenn physiology. RESULTS: In all 22 patients, the extracardiac channel was readily reconstructed with an excellent surgical field of view, without operative mortality. On cross-clamping the inferior vena cava, the systemic circulation could be well maintained by administration of dopamine. Oxygen saturation immediately became approximately 97% to 100%. Maximal pressure gradient was 11 +/- 5 mm Hg between the superior vena cava and the femoral vein. Postoperatively, serum concentration of enzymes did not critically increase (maximal aspartate transaminase, 96 +/- 89 U/L; alanine transaminase, 65 +/- 59 U/L; total bilirubin, 1.8 +/- 1.1 mg/dL; creatine kinase, 437 +/- 230 U/L). CONCLUSIONS: This alternative technique, when feasible under the current criteria, was simple and did not provide any clinically significant impediments.

Child↗
PubMed2005

Carotid clamping time as a risk factor for early restenosis after carotid endarterectomy.

OBJECTIVE: The aim of our study was to identify risk factors for early restenosis after carotid endarterectomy (CEA). METHODS: Prospective follow-up of 497 primary CEAs was performed at 3, 6, 12 and 24 months by clinical assessment and duplex ultrasound to identify > or = 50% restenosis. RESULTS: Early restenosis occurred in 71 (14.3%) patients. By univariate analysis high carotid clamping time (CCT) (p = 0.002) and absence of shunt use (p = 0.03) were related to early restenosis. High CCT was the only independent predictor of early restenosis in a forward stepwise logistic regression model (OR = 2.25; CI 1.2-4.1; p = 0.008). CONCLUSIONS: Carotid clamping time may be a novel risk factor for early restenosis.

Adult↗
PubMed2006

Abdominal drainage was unnecessary after hepatectomy using the conventional clamp crushing technique.

A prophylactic abdominal drainage catheter is routinely inserted by many surgeons in patients after hepatic resection. Between January 2002 and September 2004, 462 consecutive patients who had undergone hepatic resection using a clamp crushing method by the same surgical team were retrospectively divided into the drainage group (n = 357) and the nondrainage group (n = 105). There was no difference in hospital mortality between the two groups of patients (drainage group, 0.6% vs. nondrainage group, 0%; P = 1.0). However, there was a greater incidence of surgical complications in the drainage group (31.4% vs. 8.6%, P < 0.001), and greater incidence of wound complications and subphrenic complications in the drainage group compared to the nondrainage group (24.4% vs. 4.8%, P < 0.001). In addition, the mean (+/- SEM) postoperative hospital stay of the drainage group was 13 +/- 6.5 days, which was significantly longer than that of the nondrainage group (9.7 +/- 3.3 days, P = 0.001). On multivariate analysis, abdominal drainage and intraoperative bleeding were the independent risk factors that were significantly associated with the incidence of drainage-related complications. The results suggested that routine abdominal drainage is unnecessary after hepatic resection when the conventional clamp crushing method is used during parenchyma transection.

Abdomen↗
PubMed2006

SRY and human sex determination: the basic tail of the HMG box functions as a kinetic clamp to augment DNA bending.

Human testis-determining factor SRY contains a high-mobility-group (HMG) box, an alpha-helical DNA-binding domain that binds within an expanded minor groove to induce DNA bending. This motif is flanked on the C-terminal end by a basic tail, which functions both as a nuclear localization signal and accessory DNA-binding element. Whereas the HMG box is broadly conserved among otherwise unrelated transcription factors, tails differ in sequence and mode of DNA binding. Contrasting examples are provided by SRY and lymphoid enhancer factor 1 (LEF-1): whereas the SRY tail remains in the minor groove distal to the HMG box, the LEF-1 tail binds back across the center of the bent DNA site. The LEF-1 tail relieves electrostatic repulsion that would otherwise be incurred within the compressed major groove to enable sharp DNA bending with high affinity. Here, we demonstrate that the analogous SRY tail functions as a "kinetic clamp" to regulate the lifetime of the bent DNA complex. As in LEF-1, partial truncation of the distal SRY tail reduces specific DNA affinity and DNA bending, but these perturbations are modest: binding is reduced by only 1.8-fold, and bending by only 7-10 degrees . "Tailed" and truncated SRY complexes exhibit similar structures (as probed by NMR) and distributions of long-range conformational substates (as probed by time-resolved fluorescence resonance energy transfer). Surprisingly, however, the SRY tail retards dissociation of the protein-DNA complex by 20-fold. The marked and compensating changes in rates of association and dissociation observed on tail truncation, disproportionate to perturbations in affinity or structure, suggest that this accessory element functions as a kinetic clamp to regulate the lifetime of the SRY-DNA complex. We speculate that the kinetic stability of a bent DNA complex is critical to the assembly and maintenance of a sex-specific transcriptional pre-initiation complex.

Amino Acid Sequence↗
PubMed2006

Intraluminal aortic manipulation by means of intra-aortic filter, cannulation, and external clamp maneuvers evaluated versus dislodged embolic material.

OBJECTIVES: Aortic atherosclerosis is an important risk factor for cerebrovascular accidents in cardiac surgery. An intra-aortic filter might reduce this risk. We aimed to analyze the risks for emboli associated with intraluminal aortic manipulation and intra-aortic filter handling in relation to cannulation and external clamp maneuvers. METHODS: A model was designed with a cadaver aorta and retrograde perfusion (n = 16). A crossclamp was positioned on the ascending aorta and repeatedly opened under pressure to collect aliquots with dislodged particles. Cannulation was performed after 10 clamp maneuvers, followed by positioning and removing the intra-aortic filter, with each step followed by a washout sequence to collect perfusate. The removed filter was also analyzed. Evaluation was by means of digital image analysis, with differentiation of particles into different spectra. RESULTS: Intra-aortic filter manipulation produced a significant washout of embolic particles; in particular, this was seen for the macroscopic cellular spectrum (P = .006 and P = .002 for filter insertion and removal, respectively). Particles were also found to be collected by the filter (P = .004). In addition, cannulation and aortic crossclamp manipulation generated a notable number of particles (P = .001 and P = .013, respectively). CONCLUSIONS: The intra-aortic filter collects material during aortic manipulation. However, intraluminal aortic manipulation from filter handling can also dislodge particles, possibly related to shedding of intimal debris. This is in addition to substantial amounts of particles that are generated by aortic cannulation and aortic crossclamping.

Aged↗
PubMed2006

Fronto-orbital craniotomy reconstruction using the titanium clamp (Craniofix): a technical note.

BACKGROUND: We evaluate a new technique for plateless fixation of a bone flap after fronto-orbital craniotomy. METHODS: From September 1999 to October 2004, we performed fronto-orbital craniotomy reconstruction using the Craniofix titanium clamp in 108 consecutive patients with a variety of lesions in the anterior skull base. Postoperative computed tomographic imaging studies and clinical evaluations were performed to prospectively assess cosmetic conformity and bone flap stability and to evaluate the surgical benefit of Craniofix in these patients. RESULTS: Excellent bone flap fixation and cosmetic results were obtained in all patients 6 to 68 months (average, 36 months) after surgery. CONCLUSION: The Craniofix titanium clamp is a reliable, safe, and simple fixation device for reconstruction of fronto-orbital craniotomy.

Craniotomy↗
PubMed2006

Estimation of clamping force in high-tension bolts through ultrasonic velocity measurement.

The estimation of clamping force has been regarded as the main issue in the maintenance of high-tension bolts. This paper proposes a method which uses the dependency of ultrasonic velocity on stress based on the nonlinear elastic effect. The variation of ultrasonic velocity in the range of actual stress acting in the bolt is very small so that the precise measurement of ultrasonic velocity is needed. In this paper, we adopt a method to measure ultrasonic velocity, where the TOF (time of flight) of a tone-burst ultrasonic wave is precisely measured by using the phase detection technique. In order to verify the usefulness of the proposed method, two kinds of experiments are carried out. The first one measures ultrasonic velocity when the bolt is stressed by the tension tester, and from this, the exact axial force acting in the bolt can be determined. The results show good agreement with the expected linear relationship between ultrasonic velocity and axial stress. The second experiment measures ultrasonic velocity when the bolt is stressed by the torque wrench. The results show that ultrasonic velocity decreased as the torque increased, which is identical to the theoretically expected tendency. From these results, it can be said that the proposed method is adequate in evaluating clamping force in high-tension bolts.

Journal Article↗
PubMed1996

Hepatic resection with vascular isolation and routine supraceliac aortic clamping.

BACKGROUND: Hepatic resection with total vascular isolation has been reported to reduce hemorrhage. Addition of supraceliac aortic clamping putatively avoids hemodynamic instability, but may increase morbidity. METHODS: This technique was used in 99 major liver resections utilizing scalpel division and suture hemostasis. RESULTS: Livers were normal in 86 patients, cirrhotic with no portal hypertension in 5, and cirrhotic with portal hypertension in 8. There was 1 death in 91 patients with no portal hypertension due to hepatic failure or bleeding esophageal varices. There were 59 hemihepatectomies and 40 segmentectomies. Median operating time was 145 and 110 minutes, respectively, and mean transfused blood was 4 and 0 units, respectively, with minimal morbidity. CONCLUSIONS: Use of total hepatic vascular isolation with routine supraceliac aortic clamping is a safe and expedient method of hepatic resection that limits blood loss and maintains hemodynamic stability, but does not increase morbidity. However, the presence of portal hypertension precludes safe resection.

Adult↗
PubMed1987

Acute traumatic rupture of the aorta: repair by simple aortic cross-clamping.

This report describes the techniques used in 16 patients for repair of acute traumatic rupture of the aorta. Direct aortic cross-clamping (13 to 27 minutes) was used without additional methods of spinal cord protection. Direct suture was possible in (56%) of the 9 patients with partial rupture of the aorta but in only 1 (14%) of the 7 patients with complete disruption. In the remaining patients, the repair was carried out by interposing Gore-Tex patches (4 patients) or open tubular grafts (6 patients) using a simplified method, which is described. The 2 deaths, 1 intraoperative and 1 postoperative, were unrelated to the technique. There were no additional perioperative complications. Direct aortic cross-clamping and repair by direct suture or open tubular graft, as described, greatly simplify the correction of acute traumatic rupture of the aorta, and their use is strongly recommended.

Adult↗
PubMed1998

Clamp for coronary artery operations.

Aortocoronary bypass grafting is an accepted procedure for ischemic heart disease. Proper visualization of the coronary artery is mandatory for good surgical anastomosis. This is essential when a coronary operation is performed without cardioplegia or in surgical procedures without bypass support. For better visualization of a coronary artery, we are presenting a coronary artery clamp. We have used this clamp in minimally invasive coronary artery operations to achieve a bloodless field.

Anastomosis, Surgical↗
PubMed1999

Spinal cord protection during aortic cross-clamping using retrograde venous perfusion.

BACKGROUND: Paraplegia remains a devastating complication following thoracic aortic operation. We hypothesized that retrograde perfusion of the spinal cord with a hypothermic, adenosine-enhanced solution would provide protection during periods of ischemia due to temporary aortic occlusion. METHODS: In a rabbit model, a 45-minute period of spinal cord ischemia was produced by clamping the abdominal aorta and vena cava just below the left renal vessels and at their bifurcations. Four groups (n = 8/group) were studied: control, warm saline, cold saline, and cold saline with adenosine infusion. In the experimental groups, saline or saline plus adenosine was infused into the isolated cavae throughout the ischemic period. Clamps were removed and the animals to recovered for 24 hours before blinded neurological evaluation. RESULTS: Tarlov scores (0 = paraplegia, 1 = slight movement, 2 = sits with assistance, 3 = sits alone, 4 = weak hop, 5 = normal hop) were (mean +/- standard error of the mean): control, 0.50 +/- 0.50; warm saline, 1.63 +/- 0.56; cold saline, 3.38 +/- 0.26; and cold saline plus adenosine, 4.25 +/- 0.16 (analysis of variance for all four groups, p < 0.00001). Post-hoc contrast analysis showed that cold saline plus adenosine was superior to the other three groups (p < 0.0001). CONCLUSION: Retrograde venous perfusion of the spinal cord with hypothermic saline and adenosine provides functional protection against surgical ischemia and reperfusion.

Animals↗
PubMed2002

An automated two-dimensional optical force clamp for single molecule studies.

We constructed a next-generation optical trapping instrument to study the motility of single motor proteins, such as kinesin moving along a microtubule. The instrument can be operated as a two-dimensional force clamp, applying loads of fixed magnitude and direction to motor-coated microscopic beads moving in vitro. Flexibility and automation in experimental design are achieved by computer control of both the trap position, via acousto-optic deflectors, and the sample position, using a three-dimensional piezo stage. Each measurement is preceded by an initialization sequence, which includes adjustment of bead height relative to the coverslip using a variant of optical force microscopy (to +/-4 nm), a two-dimensional raster scan to calibrate position detector response, and adjustment of bead lateral position relative to the microtubule substrate (to +/-3 nm). During motor-driven movement, both the trap and stage are moved dynamically to apply constant force while keeping the trapped bead within the calibrated range of the detector. We present details of force clamp operation and preliminary data showing kinesin motor movement subject to diagonal and forward loads.

Automation↗