A new approach to define dynamics of the ion channel gates

Voltage-gated ion channels are of great importance in the generation and propagation of electrical signals in the excitable cell membranes. How these channels respond to changes in the potential across the membrane has been a challenging problem, and different approaches have been proposed to address the mechanism of voltage sensing and gating in these channels. In this study, we attempt a new approach by considering a simple two-state gate system and applying the path probability method to construct a nonequilibrium statistical mechanical model of the system. The model which is based on the principles of statistical physics provides a firm physical basis for ion channel gating.     

Activation kinetics of T-type calcium channel by a path probability approximation

We previously formulated dynamics of ion channel gates by the path probability method. In this study, we apply that theoretical approach to derive the activation rate kinetics of T-type calcium channel in thalamic relay neurons. We derive explicit expressions of the forward and backward rate constants and show that the proposed rate constants accurately capture form of the empirical time constant, and that they also provide its saturation to a constant value at depolarized membrane potentials. We also compare our derivations with linear and nonlinear thermodynamic models of rate kinetics obtained from the same calcium channel, and show that it is possible to capture saturation of the time constant for the depolarized membrane potentials by the only proposed rate constants.     

Conservative treatment of eminentia intercondylaris fractures of the tibia in children

Seventeen patients (16 children, 1 adolescent) were reviewed 31 months to 71 months after sustaining the common childhood fracture of the eminentia intercondylaris of the tibia. The aim was to assess long-term results and prognosis by clinical and radiological examination and to discover whether conservative treatment was adequate for type I and type II fractures according to Meyers and McKeever. Early improvement occurred in all patients after conservative treatment, but long-term results were not satisfactory in displaced fractures,which were treated with closed reduction and immobilization in extension. Therefore, anatomic reduction and rigid fixation should be obtained for displaced fractures of the eminentia intercondylaris of the tibia.     

Endocrine complications in patients with beta-thalassemia major

Thirty-seven patients with thalassemina major (TM) were studied to determine the extent and rate of endocrine complications. Mean haemoglobin and ferritin concentrations were 8.8 +/- 0.6 and 3,597 +/- 1,931, respectively. Provocation tests for growth hormone secretion were applied in patients with standing heights below the third centile and/or growth velocities below the 10th centile. Sexual maturation was assessed by using the criteria of Tanner. Glucose metabolism was assessed by fasting plasma glucose and glucose tolerance test. Basal thyroid function was measured and thyrotropin-releasing hormone tolerance test was carried out. Growth retardation was found in 40 per cent of patients and growth hormone deficiency was a prominent cause of growth retardation. Gonadal dysfunction was detected in 47 per cent of patients. Hypothyroidism was observed in 16 per cent and impaired glucose metabolism in 10.8 per cent patients. The high rate of endocrine disturbances indicates the importance of regular follow-up of thalassemia major patients with regard to endocrine complications of the disease.     

Percutaneous Placement of Metallic Stents in Malignant Biliary Obstruction: One-Stage or Two-Stage Procedure? Pre-Dilate or Not?

The aim of this paper was to evaluate the necessity of percutaneous transhepatic catheter drainage and balloon dilation procedures performed before stent insertion. One hundred and twenty-six patients with unresectable malignant biliary obstruction underwent palliative therapy by means of percutaneous transhepatic placement of 183 metallic biliary endoprotheses. Forty-four (35%) patients underwent metallic stent insertion in a one-stage procedure and 82 (65%) had undergone percutaneous transhepatic catheter drainage before stent insertion. Balloon dilation of the stenosis before stent placement (pre-dilation) was performed in 53 (42%) of 126 patients. The rate of the 30-day mortality was 11%, with no procedure-related deaths. The total rate of early complications was 29%, and 84% of these complications were due to percutaneous transhepatic catheter drainage and pre-dilation procedures. Percutaneous transhepatic catheter drainage and pre-dilation had no clinical or statistically significant effect on the patients’ survival and stent patency rate. Percutaneous transhepatic catheter drainage and balloon dilation increased the cost of stent placement 18% and 19%, respectively. Palliation of malignant biliary obstruction with percutaneous transhepatic stent insertion should be done directly, in the simplest way, without performing percutaneous transhepatic catheter drainage and balloon dilation before stent placement. It is more useful, safe, and cost-effective.     

Intravenous magnesium sulfate prophylaxis for atrial fibrillation after coronary artery bypass surgery

OBJECTIVE: Atrial fibrillation is a rhythm disorder commonly seen early after coronary artery bypass grafting, and it increases morbidity. METHODS: To investigate the effectiveness of magnesium sulfate in the prophylaxis of atrial fibrillation, we conducted a prospective, randomized, placebo-controlled clinical study on 200 consecutive patients in whom we performed elective and initial coronary artery bypass grafting operations. In each group 50% of patients underwent beating-heart operations. In the treatment group 100 patients (76 men and 24 women; mean age, 57.63 +/- 9.68 years) received 24.34 mEq (3 g) of magnesium sulfate in 100 mL of saline solution that was administered over 2 hours (50 mL/h) preoperatively, perioperatively, and at postoperative days 0, 1, 2, and 3. In the control group 100 patients (74 men and 26 women; mean age, 59.96 +/- 9.29 years) received only 100 mL of saline solution according to the same administration schedule as the treatment group. RESULTS: Atrial fibrillation developed in 15 patients from the treatment group and in 16 patients from the control group. The arrhythmia developed after 37.87 +/- 12.76 and 45.26 +/- 15.27 hours in the treatment and control groups, respectively. Although a significant relationship was found between low magnesium sulfate levels and increased incidence of atrial fibrillation (P <.05), when the incidence of postoperative atrial fibrillation is concerned, no significant difference was found between the 2 groups (P >.05). Also, no significant difference was found between operations with cardiopulmonary bypass and beating-heart operations in terms of atrial fibrillation incidence (P >.05). However, atrial fibrillation extended the duration of hospital stay in both groups (P <.05). CONCLUSION: Our findings indicate that magnesium sulfate infusion alone is not sufficient for the prophylaxis of atrial fibrillation.     

Immediate percutaneous intramedullary fixation and functional bracing for the treatment of pediatric femoral shaft fracture

Fifty-three consecutive children ages 6 to 14 with femur fractures treated with early percutaneous intramedullary fixation were evaluated retrospectively. The operation was performed within 24 hours in 50 patients and in the remainder after 48 hours. All patients were mobilized and allowed full weight-bearing in a functional brace in the early postoperative period. The average hospital stay was 4 days. The average follow-up was 24 months. There were no significant intra- or postoperative complications. An average overgrowth of 1.8 mm was measured using scanogram 24 months after surgery. In the authors' experience, this technique is highly effective for the treatment of children 6 to 14 years old with femur fractures. The main advantages of this method are early weight-bearing, immediate mobilization, short hospitalization, and fewer complications.     

Remifentanil with thiopental for tracheal intubation without muscle relaxants

Tracheal intubation may be accomplished with remifentanil and a non-opioid IV anesthetic without a muscle relaxant. In this study, we evaluated in double-blinded, prospective, randomized manner the dose requirements for remifentanil with thiopental without muscle relaxant administration to obtain clinically acceptable intubation conditions and cardiovascular responses. After premedication with midazolam 0.03 mg/kg IV, 105 patients were randomized equally to one of three study groups, each receiving the following: remifentanil 2 micro g/kg (Group I), 3 micro g/kg (Group II), and 4 micro g/kg (Group III). Remifentanil was administered over 30 s, and anesthesia was induced with thiopental 5 mg/kg. Tracheal intubation conditions were assessed by the anesthesiologist performing the intubation as: (a) excellent, (b) satisfactory, (c) fair, and (d) unsatisfactory. There were no statistically significant differences among groups regarding to demographic data. Blood pressure and heart rate did not increase in any group after accomplishing intubation. There was a significant improvement in intubation conditions between Groups I and II, I and III, and II and III (P < 0.001). We conclude that remifentanil 4 micro g/kg administered before thiopental 5 mg/kg provided excellent or satisfactory intubation conditions in 94% of patients and prevented cardiovascular responses to intubation. IMPLICATIONS: We evaluated in a double-blinded manner the dose requirements for remifentanil with thiopental without muscle relaxants for obtaining acceptable intubation condition. Our results show that remifentanil 4 micro g/kg administered before thiopental provided excellent or satisfactory intubation condition in 94% of patients.     

Levels of soluble intercellular adhesion molecule-1 and total sialic acid in serum of patients with colorectal cancer

BACKGROUND AND OBJECTIVES: Serum soluble intercellular adhesion molecule-1 (sICAM-1) and total sialic acid (TSA) are related to the metastatic potential of cancer cells. The purpose of the present investigation was to determine sICAM-1 and TSA levels in colorectal carcinoma and correlate their levels with the cancer stage. METHODS: The sera from 65 patients with colorectal cancer (18 at Dukes' B, 24 at Dukes' C, 23 at Dukes' D) were extracted before treatment. The concentrations of sICAM-1 and TSA were measured by enzyme-linked immunoassay and the thiobarbituric acid method, respectively, and compared with those from a healthy control group (n = 42). RESULTS: Mean serum sICAM-1 and TSA levels were found to be higher in the total patient group than in the control group (P < 0.0001). The concentrations of sICAM-1 and TSA were significantly higher in patients with Dukes' C and Dukes' D. The correlations between sICAM-1 and TSA became more significant as the stage of the disease increased (r = 0.58, P < 0.05 in Dukes' B, r = 0.88, P < 0.01 in Dukes' C and r = 0.81, P < 0.01 in Dukes' D). CONCLUSIONS: The results of this investigation indicate that sICAM-1 and TSA are the best of the tested markers. These markers should prove useful for monitoring malignant disease stage and for evaluating the effectiveness of various therapeutic approaches for colorectal carcinomas.