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PubMedDate not supplied

[Automated calculation of the RD parameter in euglycemic insulinemic clamp].

The authors proposed a new analytical approach to a search for the RD parameter in euglycemic insulinemic clamp which imparts a rate to glucose infusion. Two diabetic patients were investigated (RD parameter in the first case was determined by intuition, and in the second case--on the basis of mathematical iterative formulas). The analytical approach permitted a two-fold reduction of the time of clamp investigation improving its quality.

Adult↗
PubMed1996

Whole-cell patch-clamp recording reveals subthreshold sound-evoked postsynaptic currents in the inferior colliculus of awake bats.

The inferior colliculus receives excitatory and inhibitory input from parallel auditory pathways that differ in discharge patterns, latencies, and binaural properties. Processing in the inferior colliculus may depend on the temporal sequence in which excitatory and inhibitory synaptic inputs are activated and on the resulting balance between excitation and inhibition. To explore this issue at the cellular level, we used the novel approach of whole-cell patch-clamp recording in the midbrain of awake bats (Eptesicus fuscus) to record EPSCs or IPSCs. Sound-evoked EPSCs were recorded in most neurons. These EPSCs were frequently preceded by an IPSC, followed by an IPSC, or both. These findings help explain the large latency range and transient responses that characterize inferior colliculus neurons. The EPSC was sometimes followed by long-lasting oscillatory currents, suggesting that a single brief sound sets up a pattern of altered excitability that persists far beyond the duration of the initial sound. In three binaural neurons, ipsilateral sound evoked a large IPSC that partially or totally canceled the EPSC evoked by contralateral sound. In one binaural neuron with ipsilaterally evoked IPSCs, contralaterally evoked IPSCs occurred in response to frequencies above and below the neuron's best frequency. Thus, both monaural and binaural interactions can occur at single inferior colliculus neurons. These results show that whole-cell patch-clamp recording offers a powerful means of understanding how subthreshold processes determine the responses of auditory neurons.

Acoustic Stimulation↗
PubMed1996

Effect of ramipril on insulin sensitivity in obese patients. Time-course study of glucose infusion rate during euglycaemic hyperinsulinaemic clamp.

To assess the effects of angiotensin converting enzyme (ACE) inhibitor on insulin action in obesity, five normotensive non-diabetic obese women were examined on two occasions as part of a double-blind, randomized, cross-over study involving ten days of treatment with either 1.25 mg ramipril or placebo. The study consisted of a euglycaemic hyperinsulinaemic clamp (two periods of insulin infusion at rates of 0.4 and 1 mU/kg/min, 2 h for each step) combined with indirect calorimetry. The most notable results involved a significantly faster time-course of glucose infusion rates during the first 30 min of each insulin infusion period [analysed by calculating slopes (S1 and S2)] after ramipril than placebo administration. The mean glucose infusion rates reached during the last 30 min of each insulin infusion period (G1 and G2), as well as the increases in carbohydrate oxidation rates during the clamp (C1-C0 and C2-C0) and the decreases in plasma nonesterified fatty acids (A0-A1 and A0-A2), were not significantly different after ramipril and placebo. According to robust principal component analysis of S1, S2, G1, G2, C1, C2, A1 and A2 (orthogonally to C0 and A0), insulin sensitivity was improved with ramipril as compared to placebo (p = 0.013). This study strongly suggests that a low dose of an ACE inhibitor increases the activation phase of insulin action in normotensive nondiabetic obese patients and may accelerate insulin action.

Adult↗
PubMed1996

Evidence from incorporation and patch-clamp experiments for a nonselective channel of large conductance at the luminal membrane of rabbit proximal tubule.

The presence of nonselective ionic channels at the apical membrane of rabbit proximal tubule cells was investigated by fusion of proximal tubule brush border membrane vesicles onto a planar bilayer and by means of patch clamp measurements on primary cultured proximal tubule cells. The fusion of brush border membrane vesicles onto a phosphatidylethanolamine-phosphatidylcholine (1:1) planar bilayer led to the identification of a nonselective channel of 115 pS in 200 mM NaCl conditions with an ionic permeability sequence for Na+, K+, and Cl- corresponding to PNa/PK = 0.3 and PNa/PCl = 3, respectively. This channel showed an increased open probability at depolarizing potentials, but its activity was independent of the Ca2+ concentration in both the cis and trans compartments. These findings were subsequently confirmed in inside-out patch clamp experiments carried out on primary cultured proximal tubule cells. This channel was seldom seen in cell-attached recordings on resting cells, but its presence was observed with a higher probability in patch excised experiments performed following superfusion of the cells with a hypotonic solution. It is suggested on the basis of these observations that the apical membrane of rabbit proximal tubule cells contains a voltage-dependent nonselective channel, the activity of which may contribute to the regulation of the membrane potential.

Animals↗
PubMed1996

[Patch clamp].

Patch clamp technique was applied to variety of cells for variety of purposes. There are several modifications made for the technique and we can now record not only from the single channel but also from the whole cell membrane. The application of the patch recording technique was expanded and recordings were made recently from brain slice preparations. We have summarized technical aspects and several applications of patch clamp in this short review.

Animals↗
PubMed1996

[Current status of the application of patch-clamp technique and its combinations with other techniques].

The Patch-clamp technique, as an advanced electrophysiological technique, has been widely used for research in the life science research field. A recent trend is to combine this technique with other techniques, such as the Fura-2 microfluorimetry for measuring the concentration of Ca2+, electrochemical detection with carbon-fiber electrode (i.e. amperometric detection or amperometry), and single-cell reverse transcription of RNA followed by the polymerase chain reaction (RT-PCR). This article is to summarize the current status of the use of patch-clamp technique and its combinations with other techniques in solving problems related with transmembrane signal transduction in neurobiology.

Animals↗
PubMed1997

[Relation between serum amino acids and insulin sensitivity (results of a clamp study in offspring of hypertensive patients].

Hypertension which is part of the metabolic syndrome has frequently a family background. The authors investigated therefore indicators of insulin sensitivity by the method of a hyperinsulinaemic euglycaemic clamp in the offspring of hypertensive probands. In conjunction with the increased interest in the role of muscles in influencing insulin sensitivity the authors were also interested in serum amino acid levels. They examined a group of 15 healthy offspring of hypertonic subjects (PHT) and compared them with a group of 18 healthy volunteers without a family-history of hypertension. PHT had as compared with controls a higher systolic pressure (117 +/- 7.2 mm Hg vs. 106.1 +/- 11.7 mm Hg p < 0.01). In the clamp examination in PHT significantly lower indexes of tissue insulin sensitivity were recorded, SI (46.51 +/- 11.8% vs. 54.3 +/- 7.79%, p = 0.02) and ISI (6.6 +/- 3.99 vs. 9.88 +/- 5.05, p < 0.01). In the PHT group were, in addition to the different ratio of some branched chain amino acids and tyrosine, also relations between indicators of insulin sensitivity and arginine. It is thus obvious that signs of reduced insulin sensitivity are present in PHT already in the preclinical stage. Relations between the altered insulin sensitivity and arginine, the precursor of nitrogen oxide, apparent only in PHT could be a stimulus for seeking associations with endothelial damage described in insulin resistant conditions.

Adult↗
PubMed2001

Is any method of vascular control superior in hepatic resection of metastatic cancers? Longmire clamping, pringle maneuver, and total vascular isolation.

HYPOTHESIS: Although control of the hepatic vascular pedicle is commonly used during hepatic resection, the optimal method of vascular control continues to be debated. The utility of total or selective vascular isolation, pedicle inflow occlusion, or the absence of vascular isolation during minor and major hepatectomy needs to be examined. DESIGN: Retrospective review of hepatic resections performed for either isolated colorectal or noncolorectal hepatic metastases. SETTING: The University of Chicago Hospitals, Chicago, Ill, a tertiary-care referral center. PATIENTS: One hundred forty-one patients who underwent hepatic resection for isolated metastatic liver disease were identified through The University of Chicago Hospitals Tumor Registry. MAIN OUTCOME MEASURES: Intraoperative parameters, perioperative morbidity and mortality, and tumor recurrence. RESULTS: Four groups were compared with alternative methods of vascular management, including total vascular isolation, Longmire clamping, Pringle maneuver, or no vascular control. Tumor number and size were not significantly different between groups. Blood loss and transfusion requirements tended to be higher in the total vascular isolation group and were significantly higher compared with the Pringle group (P =.06) and the no vascular control group (P =.04), but this also correlated with a higher incidence of complexity of surgical resection. The highest incidence of postoperative complications occurred in the total vascular isolation group (P<.05). With similar permanent pathologic margins, the rates of intrahepatic recurrence were similar among all groups, with the no vascular control group having the lowest recurrence rate. CONCLUSIONS: All methods of vascular control appeared equivalent with respect to limiting blood loss and transfusion requirements while providing adequate surgical margins. The highest rates of blood requirements and complications were noted in the total vascular isolation group, which corresponded to the highest incidence of complex resections. The Longmire clamp group incurred the lowest incidence of complications and resulted in identical surgical margins. The application of vascular control is beneficial to surgeons during hepatic resection, but the method of control should be selected based on the location and complexity of resection required and preference of the individual surgeon.

Aged↗
PubMed1977

Operative cholangiography: new cholangiogram catheter clamp and improved technique.

We present 225 cases of routine operative cholangiography, utilizing a new squeeze-locking, split-loop clamp to secure the catheter inside the cystic duct plus an x-ray film technique using two different dye concentrations. No surgical or procedural difficulty was experienced in any of the 225 cases. Additional operating time for the procedure averaged under five minutes, with only one inconclusive x-ray film study. These results suggest that the new catheter clamp and the two-film technique provide a mechanical simplification of the procedure and that many of the causes of inconclusive x-ray film study have been eliminated.

Catheterization↗
PubMed1980

Electronic flow control and roller clamp control in intravenous therapy: a clinical comparison.

In a prospective clinical study, an electronic intravenous (IV) rate controller was compared with a standard roller clamp for control of IV infusions. The electronic IV rate controller was associated with fewer complications and more accurate fluid therapy than was the roller clamp. There was also a substantial savings of nursing time and a potential for cost savings when the electronic IV rate controller was used.

Humans↗
PubMed1982

Hemodynamics of intravenous nitroglycerin during aortic clamping.

Anesthetic management and dosage schedules of vasodilators have not been standardized in many studies of aortic cross clamping (CCL). For this reason, 25 consecutive patients with arteriosclerotic disease of the aorta were studied, all having received the same anesthetic management. Six patients who received nitroglycerin during the cross clamp period, at a dosage of 0.25 micrograms/kg/min, were compared with 19 who underwent CCL without the drug. Contractility was maintained in the nitroglycerin group, but not in the other group. Despite a low cardiac index in both groups, peripheral blood flow was adequate only in the nitroglycerin group. Intrapulmonary shunt was higher in the nitroglycerin group, but it did not significantly decrease the Pao2. Nitroglycerin infusion seems to be helpful in maintaining pre-CCL contractility and adequacy of peripheral blood flow.

Aorta, Abdominal↗
PubMed1995

Optimal cycles of hepatic ischemia and reperfusion for intermittent pedicle clamping during liver surgery.

OBJECTIVES: To evaluate the intermittent clamping of hepatic vessels during liver surgery and to determine the optimal duration of ischemia and reperfusion. PARTICIPANTS: One hundred nine adult male Sprague-Dawley rats. METHODS: Partial (70%) ischemia of the rat liver was induced by clamping of the left pedicle. To assess the influence of a single period of ischemia, the rats were divided into three groups for 15, 20, or 30 minutes of ischemia. To evaluate the influence of reperfusion duration, reperfusion following 15-minute ischemia was repeated 10 times in three groups for 5, 10, or 15 minutes of reperfusion duration. Hepatic tissue blood flow (HTBF) and hepatic beta-adenosine triphosphate (beta-ATP) levels were measured serially, and histopathological specimens were studied following single episodes of ischemia. In the reperfusion experiments, hepatic enzyme levels, survival rates, HTBF, beta-ATP, and histopathological findings were analyzed. RESULTS: When the single period of ischemia was 15 minutes, HTBF and beta-ATP levels recovered after 1 hour of reperfusion. However, both HTBF and beta-ATP levels did not return to preischemic levels when the duration of the ischemia was 20 or 30 minutes. Levels of beta-ATP and HTBF were higher, with improvement in both the histopathological findings and the survival rate, when the duration of the repeated reperfusion periods was 15 minutes, compared with 5 or 10 minutes. CONCLUSIONS: The maximum period of ischemia without irreversible damage was 15 minutes in rat liver. The damage was less severe when the duration of the repeated reperfusion periods was 15 minutes rather than 5 or 10 minutes.

Adenosine Triphosphate↗
PubMed1997

Bacterial translocation during portal clamping for liver resection. A clinical study.

OBJECTIVE: To determine the incidence and the clinical importance of gut-bacterial translocation after portal triad clamping for liver resection. DESIGN: Cohort study. SETTING: Multispecialty referral center. PATIENTS: Five cirrhotic and 10 noncirrhotic patients requiring liver resection. INTERVENTIONS: Elective liver resection under normothermic ischemic conditions (mean +/- SD duration, 40.2 +/- 13.1 minutes). Simultaneous sampling for qualitative culture of the systemic and portal blood, the upper gastrointestinal tract fluid, and a mesenteric lymph node (MLN) before and after liver resection. MAIN OUTCOME MEASURES: Positive culture rate, type of organism isolated, and septic complications rate. RESULTS: Before resection, blood cultures and MLNs were sterile in all but 1 patient; this culture-positive patient had had a recent colon resection for occlusive carcinoma and was excluded from further analysis. After resection, systemic and portal blood cultures were sterile in all cases. Conversely, the MNLs were culture positive in 6 (43%) of 14 patients. Coagulase-negative staphylococci were the most common isolates. A weak correlation was observed between the organisms isolated from the MLNs and those simultaneously present in the upper gastrointestinal tract fluid. There was no relationship between bacterial translocation and the outcome as patients with culture-positive MLNs showed no evidence of intraperitoneal septic complications and the only patient with a septic complication (a subphrenic abscess) had negative cultures after resection. CONCLUSION: A significant bacterial translocation in the MLNs occurs after portal triad clamping and liver resection, although not clinically relevant.

Adult↗
PubMed2000

Challenging the limits: build your own reliable double microvascular clamps.

This report describes the detailed construction, experimental basis, and clinical application of a reliable double microvascular clamp that can be built from inexpensive parts that are readily available. Twenty-five clinical free-tissue transfers were performed using this clamp with an acceptable free-flap survival rate.

Adult↗
PubMed1997

Sequence-specific control of gene expression by antigene and clamp oligonucleotides.

Control of gene expression at the transcriptional level can be achieved with triplex-forming oligonucleotides provided that the target sequence is accessible within the chromatin structure of cell nuclei. Using oligonucleotide-psoralen conjugates as probes we have shown that the promoter region of the gene encoding the alpha subunit of the interleukin 2 receptor and the polypurine tract of integrated HIV provirus can form sequence-specific, triple-helical complexes in cell cultures. Oligonucleotide-intercalator conjugates can inhibit transcription initiation by competing with transcription factor binding. Oligonucleotide analogues containing N3'-->P5' phosporamidate linkages form stable triple helices that are able to arrest transcription at the elongation step. A triple helix can also be formed on a single-stranded target by clamp oligonucleotides. A clamp targeted to the polypurine tract of HIV RNA is able to block reverse transcription of the viral RNA.

Animals↗
PubMed1975

A colostomy/ileostomy construction clamp.

An atraumatic handleless clamp is described with which it has been found simpler to construct a terminal ileostomy or colostomy than with other forms of clamp in general use.

Colostomy↗
PubMed1988

Effect of epidural analgesia on postoperative insulin resistance as evaluated by insulin clamp technique.

The influence of epidural neural blockade on postoperative insulin resistance was studied using the euglycaemic insulin clamp technique. Eighteen patients undergoing elective upper abdominal surgery of moderate severity were allocated to two groups: group G patients underwent operation under general anaesthesia, and postoperative pain was relieved by systemic administration of analgesia; and group E patients received epidural analgesia during surgery and epidural morphine postoperatively. In each patient the euglycaemic insulin clamp test was performed twice: several days before surgery and on postoperative day 1. Peroperative catecholamine and cortisol responses were also measured to investigate possible endocrine mechanisms of the insulin resistance. Glucose disposal (M) decreased in both groups on postoperative day 1 at plasma insulin concentrations ranging from 1.2 to 10.0 milliunits ml-1, resulting in the downward shift of dose-response curves. However, this downward shift was significantly smaller in group E than in group G patients. Urinary adrenaline excretion increased markedly on the day of operation in group G, but was significantly inhibited in group E. Urinary noradrenaline excretion increased mainly on postoperative day 1 in group G, but was significantly inhibited in group E. Plasma cortisol response was lower in group E than in group G during and shortly after operation, and was significantly inhibited in group E on postoperative day 1. These results indicate that insulin resistance after elective abdominal surgery is due to a postreceptor deficit in glucose utilization, as indicated by the downward shift of the dose-response curves. This disturbance in glucose metabolism was reduced by epidural analgesia, the results being associated with inhibited catecholamine and cortisol responses.

Analgesics↗
PubMed2003

Simple circuit to improve electric field homogeneity in contour-clamped homogeneous electric field chambers.

We redesigned contour-clamped homogeneous electric field (CHEF) circuitry to eliminate crossover distortion, to set identical potentials at electrodes of each equipotential pair and to drive pairs with transistors in emitter follower stages. An equipotential pair comprised the two electrodes set at the same potential to provide electric field homogeneity inside of the hexagonal array. The new circuitry consisted of two identical circuits, each having a resistor ladder, diodes and transistors. Both circuits were interconnected by diodes that controlled the current flow to electrodes when the array was energized in the 'A' or 'B' direction of the electric field. The total number of transistors was two-thirds of the total number of electrodes. Average voltage deviation from potentials expected at electrodes to achieve a homogeneous electric field was 0.06 V, whereas 0.44 V was obtained with another circuit that used transistors in push-pull stages. The new voltage clamp unit is cheap, generated homogeneous electric field, and gave reproducible and undistorted DNA band patterns.

DNA, Mitochondrial↗