Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “CLAMPS”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 253 records · Page 14Linked to original sources
PubMed2004

Partial clamping of the brachiocephalic trunk for total ascending aorta replacement without circulatory arrest: early and midterm results.

BACKGROUND: The aim of this study was to evaluate in elective patients the early and midterm results of partial clamping of the brachiocephalic trunk (BCT) for total ascending aorta replacement (TAAR) without circulatory arrest. Contraindications to the procedure were BCT/aortic arch calcifications and chronic aortic dissection. METHODS: The right radial artery was cannulated to monitor the systemic pressure after the BCT was partially clamped. A specially designed clamp was applied obliquely to occlude approximately 50% of the BCT and part of the aortic arch. The distal tip of the clamp was positioned in front of the left subclavian artery. From January 2002 to October 2003, 92 patients underwent TAAR. In 62 patients (67.4%), partial clamping of the BCT was used. Twenty of these patients underwent isolated TAAR, 27 underwent aortic valve replacement and TAAR, 11 had a Bentall operation, and 2 had a Cabrol operation. The aortic valve was spared in the remaining 2 patients. The mean (+/- SD) aortic cross-clamping and cardiopulmonary bypass times were 96 +/- 31 minutes and 116 +/- 43 minutes, respectively. RESULTS: Early mortality was 1.6% (1 patient). No cerebrovascular accidents occurred, demonstrating the safety of the technique. The major complications were acute respiratory insufficiency in 2 cases and acute renal failure in 5. The mean follow-up time was 9.0 +/- 6.5 months. The mean 18- month and event-free survival rate was 96.6% +/- 0.9%. CONCLUSION: Partial clamping of the BCT for TAAR without circulatory arrest provides good early and midterm clinical results. Aortic arch clamping is not associated with cerebrovascular accidents.

Aorta↗
PubMedDate not supplied

Comparison of continuous versus intermittent hepatic pedicle clamping in an experimental model.

BACKGROUND/AIMS: The tolerance of the liver to ischemia obtained with intermittent clamping of the hepatic pedicle or continuous Pringle maneuver was tested. METHODOLOGY: Ninety rats were divided into three groups undergoing total duration of clamping ischemia of 60, 90, and 120 min. Each group of rats were subdivided to receive continuous Pringle maneuver, 30-min or 15-min intermittent clamping. The clamp release time between the periods of liver ischemia was 5 min. Survival at 7 days and postoperative changes of liver function (transaminase enzymes, bilirubin, and adenosine-5'-triphosphate levels (hepatocellular damage index) were recorded. RESULTS: Intermittent clamping of the hepatic pedicle was better tolerated than the continuous clamping method. With continuous clamping the rat survival rates inversely correlated with the duration of ischemia. Survival rates at 15-min and 30-min intermittent ischemia groups were significantly higher than in the continuous clamping group. CONCLUSIONS: This data suggest that when the Pringle maneuver is adopted, it should be applied intermittently rather than continuously.

Animals↗
PubMed2003

[Single clamp technique in elderly patients undergoing coronary artery surgery].

OBJECTIVE: The results of single clamp and partial clamp techniques were retrospectively compared in elderly patients (>70 years) undergoing coronary artery bypass grafting operation (CABG). METHODS: A total of 244 elderly patients undergoing CABG between January 1995 and March 2002 in our center were studied. Single-clamp technique was used in 32 cases (Group 1) and partial-clamp technique was used in 212 cases (Group 2). All patients had isolated coronary artery lesions and a primary elective coronary bypass grafting surgery was planned for every case. Preoperative, operative and postoperative variables; age, gender, pre- and post-operative neurological status (stroke, amaurosis fugax, aphasia, hemiplegia, hemiparesis), cerebrovascular diseases, diabetes mellitus, hypertension, number of distal grafts, left ventricular score, durations of aortic cross-clamping and cardiopulmonary bypass (CPB) times, perfusion pressure during CPB, and postoperative cardiac status were recorded. Patients with a history of neurological complications were excluded from the study. RESULTS: Overall, mean age was 71.9+/-2.18 years. Patients in Group 1 were significantly older as compared to patients in Group 2 (p< 0.01). Average duration of cross-clamping in Group 1 was significantly longer (p<0.001) compared to Group 2, but there were no differences with regard to the total duration of cardiopulmonary bypass (p=0.535). No patients had neurological complications in Group 1, however 22 patients in Group 2 had neurological complications (p<0.05). CONCLUSION: Although single-clamp technique was associated with a longer cross-clamp time, the duration of CPB was not increased and the incidence of neurological complications was low.

Aged↗
PubMed2005

[Comparison of cardiac output measured by pulseCO and that by vigilance during inferior vena cava clamping].

BACKGROUND: PulseCO is a low invasive apparatus to measure cardiac output continuously from arterial pulse waveform (PulseCCO). It is thought that the accuracy of PulseCCO measurement is clinically acceptable with stable hemodynamics. We measured and evaluated PulseCCO during inferior vena cava clamp (IVC clamp). METHODS: Anesthesia was induced with propofol and vecuronium. After induction, an arterial catheter and a pulmonary artery catheter were inserted, and anesthesia was maintained with general anesthesia and continuous epidural anesthesia. At first IVC was clamped for five minutes and after an interval of five minutes IVC was clamped again. During IVC clamp maneuver, we measured PulseCCO and continuous cardiac output with Vigilance (VigilanceCCO). RESULTS: At the time of the first IVC clamp and declamp, VigilanceCCO was unchanged, but Pulse CCO showed a marked change. After the second IVC clamp, both PulseCCO and VigilanceCCO decreased, but the change was slower with VigilanceCCO. CONCLUSIONS: With IVC clamp maneuver which is thought to cause rapid change of cardiac output, PulseCCO showed more rapid change in comparison with VigilanceCCO. In the state where hemodynamics change rapidly, PulseCO can be a more useful monitor.

Aged↗
PubMed1989

Assessing clamp-related vascular injuries by measurement of associated vascular dysfunction.

The development of vascular clamps requires a reliable method to quantitate clamp-related vascular injuries. The degree of vessel damage usually is estimated subjectively from photomicrographs made with scanning electron microscopy. In order to test whether the use of vascular rings to assess residual vascular function may be a better method, rabbit thoracic aortas were occluded by five types of clamps: a Fogarty softjaw bulldog, a Fogarty Hydragrip, a 6-inch Satinsky clamp, an Edslab bulldog, and a silicone vessel band. Each area of clamp injury was sectioned into a vascular ring and suspended in a tissue bath. Residual vascular function was determined by contraction in response to phenylephrine and by relaxation in response to methacholine chloride and sodium nitroprusside. Morphologic studies with use of Evans blue dye and scanning electron microscopy complemented the vascular-function studies. The Fogarty bulldog clamp was the best at preserving vascular contraction and relaxation; the more crushing Satinsky clamp was the worst. The testing of vascular rings for residual function appears to be a useful technique for objectively quantitating vascular clamp-related vascular damage.

Animals↗
PubMed1989

[Clinical study of blood cardioplegia--for aerobic metabolism during aortic cross-clamping].

Blood cardioplegia is considered to be superior in oxygenating potential, buffering potential, oncotic, and other physiologic effects. In clinical cases, however, it is unproven whether aerobic metabolism can be obtained by using blood cardioplegia during aortic cross-clamping. Aerobic metabolism during aortic cross-clamping was therefore evaluated in patients with valvular heart disease who underwent relatively long periods of ischemic arrest. Myocardial metabolism of oxygen, lactate and pyruvate was studied in 14 patients under 126 +/- 41.2 min of cardiac arrest, and intramyocardial carbon dioxide tension (PmCO2) was also monitored continuously in 23 patients who received 121 +/- 29.8 min of aortic cross-clamping. After aortic cross-clamping, 4 degrees C St. Thomas solution was infused for immediate cooling, followed by blood cardioplegia for replenishment every 20-25 min. Blood cardioplegia and myocardial temperature were maintained within 15-20 degrees C by using an automatic cardiac hypothermia control system. Myocardial oxygen extraction during the pre-ischemic period was 26.8 +/- 13.3%. At 15 and 30 min after reperfusion, it was 30.0 +/- 10.8% and 33.8 +/- 8.2%, respectively. During ischemic arrest, myocardial oxygen extraction decreased, but the infusion of blood cardioplegia kept it above 14.0 +/- 9.3% at all times. As for lactate metabolism, although some cases showed lactate production even before the aortic cross-clamping, lactate extraction was attained in some cases during blood cardioplegia perfusion. Changes in excess lactate and redox potential of lactate and pyruvate (delta Eh) showed that aerobic metabolism could be obtained in 13/32 (41%) infusions of blood cardioplegia. PmCO2 at the aortic cross-clamp was 47.0 +/- 27.7 mmHg, and gradually rose during the ischemic arrest, but only as far as 68.4 +/- 64.8 mmHg at the time of cross-clamp release. PmCO2 decreased with each infusion of blood cardioplegia, and the decrease lasted up to 10 minutes. Though PmCO2 began to rise thereafter, the effect of blood cardioplegia continued as long as 20-25 min after the infusion. In conclusion, blood cardioplegia provides aerobic metabolism during aortic cross-clamping even in clinical setting, provided that cardiac hypothermia and delivery of cardioplegic solution are maintained appropriately.

Aerobiosis↗
PubMed1988

The effect of mannitol and dopamine on the renal response to thoracic aortic cross-clamping.

Postoperative renal failure and insufficiency are important complications of operations that require thoracic aortic cross-clamping. Successful application of pharmacologic methods to protect renal function would be clinically useful. The ability of mannitol and dopamine to prevent renal dysfunction in a canine model of thoracic aortic cross-clamping was studied. Twenty animals were divided into four equal groups, and all underwent thoracic aortic cross-clamping for 60 minutes. An intra-aortic infusion of saline (control), mannitol, dopamine, or mannitol plus dopamine was started before, and continued during, the period of aortic occlusion. Glomerular filtration rate was significantly depressed 60 minutes after clamp release, and although there was some recovery in treated animals 150 minutes after clamp release, it remained significantly decreased (52% to 73% of baseline values, p less than 0.01). Renal blood flow was significantly reduced 60 minutes after clamp release, and there was no recovery in any group at 150 minutes (38% to 56% of baseline values, p less than 0.01). No significant differences in osmolar clearance or fractional excretion of sodium were evident between groups. These data reveal that the profound reductions in glomerular filtration and renal blood flow induced by thoracic aortic cross-clamping were not attenuated by mannitol or dopamine and suggest that efforts to protect renal function should be directed toward improving renal blood flow in the post-clamp period.

Acute Kidney Injury↗
PubMed1994

Peritonitis incidence on a disconnect CAPD-system with or without the use of iodine clamp shields.

The purpose of the study was to review a single center's experience with the disconnect system for continuous ambulatory peritoneal dialysis (CAPD), and to evaluate peritonitis incidence with and without use of iodine-containing clamp shields. The retrospective review of patients using the disconnect system lasted from January 1991 throughout March 1993, evaluating the peritonitis incidence with and without use of iodine clamp shields. In the observation period, a total of 103 patients were evaluated. Of these, 42 patients were treated with iodine clamp shields until July 1992 and then were instructed not to use the iodine clamp shields, thus acting as their own controls. We found an overall peritonitis incidence of 0.411 episodes/patient/year (= 29.2 patient-months/episode) on disconnect CAPD-system (Baxter), in spite of the fact that more than 60% of our dialysis population is treated with peritoneal dialysis. We found no difference in peritonitis rates with or without the use of iodine clamp shields. Peritonitis rates with clamp shields were 0.400 episodes/patient/year and, without clamp shields, were 0.400 episodes/patient/year. The introduction of a disconnect system provided a system with low incidence of peritonitis. No difference in peritonitis rates was observed with or without the use of iodine clamp shields, allowing us to reduce the cost of treatment and to simplify training procedures.

Adult↗
PubMed1996

[Analysis of oxidative stress in rat fetus induced by clamping and reperfusion of uterine vessels].

Effects of oxidative stress (OS) on the fetus were studied under ischemic induced by clamping the uterine vessels of pregnant rats. OS was evaluated by superoxide (O-.2) released from red blood cells. Fetal RBC-O-.2 of the ischemic rats (clamping for 10 min and 20 min) was significantly higher than that of the control group (p < 0.01). Maternal RBC-O-.2 tended to increase, but not significantly. When readings before and after clamping were compared, the activity of fetal RBC SOD had increased in the ischemic group (clamping time for 10 min), but significantly decreased in the 20 min clamping rats (p < 0.01). Maternal SOD activity tended to decrease along with clamping time. The amount of lipidperoxide was significantly greater in the fetal ischemic liver subjected to clamping for 20 minutes than in the tissue subjected to clamping for 10 minutes. The lipidperoxide level was significantly higher in the fetal ischemic brain exposed for 10 minutes than in the control. These results indicate that fetal RBC-O-.2 increased along with ischemic time, and the maternal RBC-O-.2 had been influenced by the increase in fetal RBC-O-.2. Based on these observations, it was concluded that the OS due to ischemic injury had a more adverse effect on the fetal brain than on the liver.

Animals↗
PubMedDate not supplied

Selective and unselective clamping in cirrhotic liver.

BACKGROUND/AIMS: Liver surgery requires a reduction of the operative blood loss especially for patients with cirrhosis. Selective or unselective liver clamping during hepatic resection is performed to minimize the surgical risk for such compromised patients. METHODOLOGY: We carried out elective hepatic resection in 158 patients with the use of total hilar clamping (Pringle's manoeuvre) or selective vascular clamping (Makuuchi's manoeuvre). The clinical outcomes were evaluated according to the clamping method and the condition of background liver. RESULTS: Pringle's manoeuvre was used in 132 patients who underwent all types of hepatectomy, whereas Makuuchi's manoeuvre was applied selectively to 26 patients, most of whom underwent segmentectomy or subsegmentectomy. A modified Makuuchi's manoeuvre was used in eight healthy donors who underwent left-sided hepatectomy for transplantation. The cumulative clamping times and blood losses were 61 +/- 47 min (mean +/- SD) and 831 +/- 716 ml in the Pringle's manoeuvre group, and 95 +/- 47 min and 1.035 +/- 577 ml in the Makuuchi's manoeuvre group. In patients with normal hepatic parenchyma the longest clamping time was 322 min, and in those with cirrhosis it was 202 min. All the patients in this series tolerated vascular clamping well, and their hepatic functional parameters returned, regardless of the presence or absence of cirrhosis, to the baseline levels within a week. As a whole, the operative morbidity and mortality rates were 20.3% and 0%, respectively. CONCLUSIONS: Intermittent total or selective clamping can be an indispensable procedure during hepatic resection for all patients, irrespective of the degree of hepatic dysfunction, to improve safety and resectability.

Blood Loss, Surgical↗
PubMed1998

Effect of intermittent hepatic pedicle clamping on free radical generation in the rat liver.

BACKGROUND: Intermittent hepatic pedicle clamping is thought to cause less hepatic reperfusion injury compared with continuous clamping. The mechanisms underlying this difference are unknown. We examined the relationship between intermittent ischemia/reperfusion and the production of free radicals using electron spin resonance spectrometry. METHODS: Alpha-(4-pyridyl 1-oxide)-N-tert-butylnitrone was administered to rats as a spin trap agent. Continuous clamping (15, 30, or 60 minutes) or intermittent clamping (four cycles of 15-minute ischemia and 5 or 15 minutes of reperfusion) of hepatic pedicle was carried out. After reperfusion, free radical production in the liver was measured by an electron spin resonance spectrometer, and the level of hepatic injury was evaluated by measuring liver enzyme. RESULTS: Longer periods of ischemia increased free radical production after reperfusion. There was no significant increase in free radical production or liver enzymes when the duration of ischemia was 15 minutes. Free radical production and liver damage were significantly less severe in intermittent pedicle clamping than in continuous clamping for 60 minutes, especially when the duration of the reperfusion between four cycles of ischemia was 15 minutes. CONCLUSIONS: These results indicate that intermittent pedicle clamping lessens free radical production when compared with continuous clamping, although many free radicals are produced.

Alanine Transaminase↗
PubMed1994

Sources of errors in different single-electrode voltage-clamp techniques: a computer simulation study.

The use of voltage clamp with a single electrode has been useful in estimating kinetic parameters for a number of ionic whole-cell currents. There are two main types of such a technique: discontinuous voltage clamp (dSEVC) (Brennecke and Lindemann, 1974), and continuous voltage clamp (cSEVC) (Hamill et al., 1981). We have studied, by means of computer simulations, the performance of both types of clamp on estimating activation kinetics parameters of a typical neuronal Ca2+ current. Deviations from the theoretical values are shown to be sensitive on both set-up and cell properties. Both types of clamp are shown to lose voltage control when either access resistance or absolute membrane conductance are increased. In contrast, changes in membrane capacitance affect differently to the estimates obtained by the two types of clamp. Cell size is also shown to affect cSEVC performance but not that of dSEVC. The nature and magnitude of errors obtained by using both types of clamp in different situations are discussed.

Amplifiers, Electronic↗
PubMed2006

StdpC: a modern dynamic clamp.

With the advancement of computer technology many novel uses of dynamic clamp have become possible. We have added new features to our dynamic clamp software StdpC ("Spike timing-dependent plasticity Clamp") allowing such new applications while conserving the ease of use and installation of the popular earlier Dynclamp 2/4 package. Here, we introduce the new features of a waveform generator, freely programmable Hodgkin-Huxley conductances, learning synapses, graphic data displays, and a powerful scripting mechanism and discuss examples of experiments using these features. In the first example we built and 'voltage clamped' a conductance based model cell from a passive resistor-capacitor (RC) circuit using the dynamic clamp software to generate the voltage-dependent currents. In the second example we coupled our new spike generator through a burst detection/burst generation mechanism in a phase-dependent way to a neuron in a central pattern generator and dissected the subtle interaction between neurons, which seems to implement an information transfer through intraburst spike patterns. In the third example, making use of the new plasticity mechanism for simulated synapses, we analyzed the effect of spike timing-dependent plasticity (STDP) on synchronization revealing considerable enhancement of the entrainment of a post-synaptic neuron by a periodic spike train. These examples illustrate that with modern dynamic clamp software like StdpC, the dynamic clamp has developed beyond the mere introduction of artificial synapses or ionic conductances into neurons to a universal research tool, which might well become a standard instrument of modern electrophysiology.

Action Potentials↗
PubMed2006

The hypertriglyceridemic clamp technique. Studies using long-chain and structured triglyceride emulsions in healthy subjects.

In a randomized crossover study, plasma kinetics of 2 different types of fat emulsions were studied in 8 healthy volunteers by using a hypertriglyceridemic clamp technique. The method involves the stabilization of serum triglyceride (TG) concentration during 180 minutes at a predetermined level (4 mmol/L) by adjustment of TG infusion rate by repeated online measurements of serum TG concentration. The fat emulsions under study were a long-chain fatty acid triglyceride (LCT) emulsion (Intralipid 20%, Fresenius Kabi, Sweden) and a structured triglyceride (STG) emulsion (Structolipid 20%, Fresenius Kabi) where medium- and long-chain fatty acids have been interesterified within a TG molecule. The hypertriglyceridemic clamp was found to have acceptable reproducibility when tested in 3 healthy individuals on 2 different occasions, as similar steady-state TG levels were obtained by infusing similar amounts of fat. The average (+/-SEM) TG concentration during the 180-minute clamp was similar for STGs and LCTs (4.0 +/- 0.1 vs 3.9 +/- 0.1 mmol/L; not significant), but the amount of fat that had to be infused was significantly higher during STG than during LCT clamping (0.31 +/- 0.04 vs 0.21 +/- 0.02 g TG per minute; P < .05). Higher serum levels of free fatty acids (1.80 +/- 0.13 vs 0.96 +/- 0.09 mmol/L; P < .05), free glycerol (1.30 +/- 0.07 vs 0.76 +/- 0.08 mmol/L; P < .001), and beta-OH butyrate (1.61 +/- 0.44 vs 1.17 +/- 0.23 mmol/L; not significant) were obtained at the end of the clamp during infusion of STGs compared with LCTs. During infusion of STGs the medium-chain fatty acids octanoic (C:8) and decanoic acid (C:10) constituted approximately half of circulating fatty acids that correspond to the compositional ratio of the emulsion. Plasma lipoprotein lipase (LPL) concentration was higher during STG than during LCT clamping (6.06 +/- 0.62 vs 3.15 +/- 0.40 mU/mL; P < .05), and there was a positive correlation between the mean LPL concentration and the amount of infused TG during the steady-state period (r = 0.58; P < .05). In conclusion, the hypertriglyceridemic clamp method was found to give reproducible results and could be considered for comparison of metabolic clearance properties of different types of fat emulsions. The capacity of healthy subjects to eliminate STGs from blood was greater than for LCTs. An increased LPL activity induced by the higher TG infusion rate may have contributed to the increased metabolic clearance of STGs.

Adult↗
PubMed1999

The effect of increasing clamping forces on endothelial and arterial wall damage: an experimental study in the sheep.

PURPOSE: This study aimed to relate the level of physical force applied to the arterial wall by atraumatic clamps to the degree of endothelial and wall damage. METHODS: Sixteen sheep carotid and femoral arteries were each demarcated into four segments 1 cm apart (total 64 segments). Each segment was clamped for 15 min with a standard angled DeBakey vascular clamp. Four levels of force were generated by closing the clamp at three, four, five and six notches of closure. The extent of endothelial injury was assessed by using a dedicated computer assisted image acquisition program to measure the area stained by Evan's blue dye. The extent of damage to the layers of the arterial wall was analyzed and compared by scanning electron microscopy and light microscopy. RESULTS: For femoral arteries, the area of endothelial injury was considerably less for three notch (3.76 +/- 0.28 newtons) and four notch (5.68 +/- 0.29 newtons) closure compared with that for five notch (6.19 +/- 0.31 newtons) and six notch (6.61 +/- 0.16 Newtons) closure (p = 0.01). For carotid arteries, three notch (5.68 +/- 0.28 newtons) closure caused less damage than did four notch (7.98 +/- 0.29 newtons), five notch (9.17 +/- 0.40 newtons) and six notch (9.57 +/- 0.64 newtons) closure (P = 0.02). Scanning electron microscopy confirmed the extent and depth of arterial injury corresponded directly to the forces generated by the vascular clamps. CONCLUSIONS: The closing forces generated by arterial clamps correlated positively with the extent of artery wall injury. Vascular clamps should be applied at the minimum level of force that will arrest blood flow.

Animals↗
PubMed1992

Venous versus arterialised venous blood for assessment of blood glucose levels during glucose clamping: comparison in healthy men.

The aim of this study was to investigate the influence of the arteriovenous (A-V) gradient in blood glucose concentrations at low and high insulin levels on the determination of glucose requirements during glucose clamping in 9 healthy, insulin sensitive, male volunteers. In a random order two clamps were performed, once using arterialised venous blood (A Clamp, mean pO2 = 11.5 +/- 0.36 kPa, 86 +/- 2.7 mmHg), and once using venous blood (V clamp, mean pO2 = 7.9 +/- 0.21 kPa, 59 +/- 1.6 mmHg). Insulin levels were maintained at 48 +/- 2.4 mU/l from 0-180 min and at 1054 +/- 114 mU/l from 180-360 min. Elevation of insulin levels caused a significant rise of the A-V gradient: from 0.3 +/- 0.1 to 0.5 +/- 0.1 mmol/l (p < 0.05) and from 0.2 +/- 0.1 to 0.3 +/- 0.1 mmol/l (p < 0.05) during the A and V clamps, respectively. Despite these A-V glucose gradients no significant differences were found for the glucose requirements during the last 30 min of each period of insulin infusion between the A and V clamps: 43.70 +/- 3.4 vs 44.8 +/- 2.8 mumol.kg-1.min-1 during the low insulin level and 77.3 +/- 5.0 vs 76.2 +/- 3.4 mumol.kg-1.min-1 during the high insulin level. We conclude that the A-V glucose gradient, even at high insulin levels, does not influence the assessment of glucose requirements to a measurable extent, allowing the use of the simpler technique of taking venous rather than arterialised venous blood for the measurements of glucose levels during glucose clamping.

Adult↗
PubMed1999

Euglycemic hyperinsulinemic clamp to assess posthepatic glucose appearance after carbohydrate loading. 2. Evaluation of corn and mung bean starches in healthy men.

BACKGROUND: The rate of absorption of glucose from carbohydrates is important in several aspects of health. We recently validated a noninvasive technique in pigs, euglycemic hyperinsulinemic clamp plus oral carbohydrate loading (OC-Clamp), to quantify the rate of net posthepatic appearance of glucose after ingestion of carbohydrates. OBJECTIVE: The OC-Clamp procedure was performed in 8 healthy men to compare the net posthepatic appearance of glucose after ingestion of 1 of 3 carbohydrates. DESIGN: Human volunteers underwent the OC-Clamp procedure at an insulin infusion rate of 1.5 mU x kg(-1) x min(-1) (n = 5). The oral carbohydrate load (1 g/kg) consisted of glucose, cornstarch, or mung bean starch. During the OC-Clamp procedure, the glucose infusion rate decreased during absorption to maintain plasma glucose steady state and the decrease reflected the net posthepatic appearance of glucose. In addition, carbohydrates were loaded without insulin infusion (n = 6) and glycemic indexes were calculated (with glucose as the reference). RESULTS: The mean (+/-SEM) glycemic index of cornstarch was higher (95 +/- 18) than that of mung bean starch (51 +/- 13). In the OC-Clamp experiments, the posthepatic appearance of glucose and cornstarch did not differ significantly and represented 79.4 +/- 5.0% and 72.6 +/- 4.0%, respectively, of the load after complete absorption (within 3 h). In contrast, the net posthepatic appearance of glucose from mung bean starch was significantly lower (35.6 +/- 4.6% of the load, P < 0.001) than that from glucose and cornstarch, even 4.5 h postprandially. CONCLUSIONS: The OC-Clamp technique allows a continuous assessment of net posthepatic appearance of glucose after ingestion of carbohydrates and significant discrimination between corn and mung bean starches.

Analysis of Variance↗
PubMed2006

Dynamic clamp: a powerful tool in cardiac electrophysiology.

Dynamic clamp is a collection of closely related techniques that have been employed in cardiac electrophysiology to provide direct answers to numerous research questions regarding basic cellular mechanisms of action potential formation, action potential transfer and action potential synchronization in health and disease. Building on traditional current clamp, dynamic clamp was initially used to create virtual gap junctions between isolated myocytes. More recent applications include the embedding of a real pacemaking myocyte in a simulated network of atrial or ventricular cells and the insertion of virtual ion channels, either simulated in real time or simultaneously recorded from an expression system, into the membrane of an isolated myocyte. These applications have proven that dynamic clamp, which is characterized by the real-time evaluation and injection of simulated membrane current, is a powerful tool in cardiac electrophysiology. Here, each of the three different experimental configurations used in cardiac electrophysiology is reviewed. Also, directions are given for the implementation of dynamic clamp in the cardiac electrophysiology laboratory. With the growing interest in the application of dynamic clamp in cardiac electrophysiology, it is anticipated that dynamic clamp will also prove to be a powerful tool in basic research on biological pacemakers and in identification of specific ion channels as targets for drug development.

Action Potentials↗