Calcium channels / 한양의대학술지

Calcium channels are ion channels formed by membrane spanning proteins that have a calciumselective pore. There are some types of calcium channels. One type is calcium channel whose gating is controlled by voltage in the cell membrane. The others are controlled by binding of ligands in membranes of intracellular organelles and plasma membranes. Calcium channels whose gating is controlled by voltage are called voltage-gated calcium channels(VGCC). VGCC's are present in all excitable cells, but also in many non-excitable cells. VGCC's are distinguished by differences in voltage dependence, kinetics, and sensitivity to a variety of blockers. One distinction is by the voltage amount to open the channel. Channels requiring smaller depolarizations are called low voltage activated(LVA) channels and channels requiring lager depolarizations are called high voltage activated(HVA) channels. More recently, VGCC's have been classified by their amino acid sequence identity. VGCC's are composed of several subunits. Among them, alpha1 subunit has the main function. It has voltage sensor and ionic selectivity. VGCC's are activated by voltage but also inactivated by voltage. Calcium entry can also inactivate some VGCC's. VGCC's play very important roles in the heart, skeletal muscle, neurons and are modulated by some mechanisms such as phosphorylation.

Re-anastomosis above a Preceding Anastomosis Made by a Low Anterior Resection

Periodic colonoscopic checkup is needed for patients suffering from colorectal cancer, based on the property that a colorectal neoplasm often recurs synchronously or metachronously. Surgical management appropriate to the occasion should be taken in recurrent colorectal cancer. Particularly, recurring colorectal cancer closely above the prior anastomosis for a low anterior resection should be eliminated by using an abdomino-perineal resection, including the preceding anastomotic site or a new anastomotic creation. Under the latter instance, ample possibility exists for postoperative anastomotic stenosis or leakage by reason of insufficient blood supply to the segment between the earlier anastomosis and the later one. The authors report two cases of re-anastomosis for colorectal cancer just above a previous anastomosis taken by a low anterior resection for rectal cancer. In a 52-year-old male with a history of neoadjuvant concomitant chemo-radiotherapy (CCRT) and low anterior resection for rectal cancer located at 6 cm from the anal verge, a new adenocarcinoma was detected 7 cm from the previous anastomotic site and 3 cm from the anal verge. Considering anal sphincter preservation, the re-anastomosis was made at the upper part of the preceding anastomosis. The patient experienced no surgical complications, such as anastomotic stenosis or leakage and functional defecation difficulty. In another patient, a 50-year-old male with a low anterior resection and adjuvant CCRT for rectal cancer 8 cm from anal verge, a new adenocarcinoma was detected in the colon. The new adenocarcinoma was located 10 cm from the anal verge and 8 cm from the previous anastomosis. The same surgical management was applied to this case, with the same postoperative result.

Therapeutic Results of Transanal Endoscopic Microsurgery and Radical Surgery for T1, T2 Rectal Cancer

PURPOSE: Transanal endoscopic microsurgery (TEM) has gained increasing acceptance as a treatment of choice for early rectal cancer. The purpose of this study was to compare the results of TEM and radical surgery in patients with T1 and T2 rectal cancer. METHODS: From October 1994 to December 2000, 74 patients with T1 and T2 rectal adenocarcinoma treated with TEM were compared with 100 patients with T1N0M0 and T2N0M0 rectal adenocarcinoma treated with radical surgery. Retrospective analysis was made regarding to recurrence and survival rate. Neither group received adjuvant chemo-radiation. There was no significant difference in age, gender, tumor location and follow-up period between two groups, except tumor size. RESULTS: Of 74 patients in TEM group, 52 patients were T1 (70.3%) and 22 patients were T2 (29.7%). Of 100 patients in radical surgery group, 17 patients were T1 (17.0%) and 83 patients were T2 (83.0%). Five-year local recurrence rates were 4.1% for T1, 19.5% for T2 after TEM, 0% for T1 and 9.4% for T2 after radical surgery. There was no statistical difference between T1 rectal cancer (P=0.95), but in T2 rectal cancer, it was higher after TEM than after radical surgery (P=0.04). Five-year disease free survival rates showed no statistical difference between two groups (TEM group: 95.9% for T1, 80.5% for T2, radical surgery group: 94.1% for T1, 83.3%for T2; P=0.35, P=0.12). Five-year survival rate were 100% for T1, 94.7% for T2 after TEM and 92.9% for T1, 96.1% for T2 after radical surgery. There were no significant statistical difference between two groups (P=0.07, P=0.48). CONCLUSIONS: In T1 rectal cancer, there were no difference in recurrence and five-year survival rate between TEM and radical surgery group. In T2 rectal cancer, five-year survival rate showed no statistical difference between two groups, but TEM carried higher risk of local recurrence. Therefore careful selection of the patients is required for TEM and when proper muscle invasion is proven after TEM, further treatment should be considered.