ABSTRACT
Patch clamp is a technique that can measure weak current in the level of picoampere (pA). It has been widely used for cellular electrophysiological recording in fundamental medical researches, such as membrane potential and ion channel currents recording, etc. In order to obtain accurate measurement results, both the resistance and capacitance of the pipette are required to be compensated. Capacitance compensations are composed of slow and fast capacitance compensation. The slow compensation is determined by the lipid bilayer of cell membrane, and its magnitude usually ranges from a few picofarads (pF) to a few microfarads (μF), depending on the cell size. The fast capacitance is formed by the distributed capacitance of the glass pipette, wires and solution, mostly ranging in a few picofarads. After the pipette sucks the cells in the solution, the positions of the glass pipette and wire have been determined, and only taking once compensation for slow and fast capacitance will meet the recording requirements. However, when the study needs to deal with the temperature characteristics, it is still necessary to make a recognition on the temperature characteristic of the capacitance. We found that the time constant of fast capacitance discharge changed with increasing temperature of bath solution when we studied the photothermal effect on cell membrane by patch clamp. Based on this phenomenon, we proposed an equivalent circuit to calculate the temperature-dependent parameters. Experimental results showed that the fast capacitance increased in a positive rate of 0.04 pF/℃, while the pipette resistance decreased. The fine data analysis demonstrated that the temperature rises of bath solution determined the kinetics of the fast capacitance mainly by changing the inner solution resistance of the glass pipette. This result will provide a good reference for the fine temperature characteristic study related to cellular electrophysiology based on patch clamp technique.
Subject(s)
Cell Membrane , Electric Capacitance , Membrane Potentials , Patch-Clamp Techniques , TemperatureABSTRACT
Background: The morbidity of small bowel adenocarcinoma (SBA) in gastrointestinal neoplasms is relatively low, and there are few studies focusing on the clinicopathological features and prognostic data of SBA both at home and abroad. Aims: To investigate the metastatic characteristics and prognosis of patients with SBA. Methods: Patients with SBA were identified from the Surveillance, Epidemiology, and End Results (SEER) database from 2010 to 2016. Data on metastatic patterns, clinicopathological features and prognosis were extracted and analyzed, and the prognostic factors were assessed by Cox proportional hazard model. Results: A total of 2 489 cases of SBA were identified, of which 448 cases (18.0%) had liver metastasis, 48 (1.9%) had bone metastasis, and 129 (5.2%) had lung metastasis. Different metastatic sites were associated with different clinicopathological parameters. There were no significant differences in bone or lung metastasis between patients with and without liver metastasis (P>0.05). The median overall survival (OS) of patients with liver, bone, and lung metastasis was 6, 4, and 8 months, respectively, all were shorter than that of patients without metastasis at corresponding site (P<0.05). Surgical resection of primary tumor improved the OS of patients without metastasis and with liver metastasis, but had no effect on OS of patients with lung or liver plus lung metastases. Multivariate analysis showed that aged more than 66 years, poorly differentiated and undifferentiated tumors, and lymph node metastasis were independent risk factors for poor prognosis, while married and surgical resection of primary tumor were protective factors. Conclusions: SBA patients with metastasis had a poorer OS than those without. Different metastatic characteristics are associated with different prognosis. Liver is an important distant metastatic organ for SBA. For SBA patients, married and surgical resection of primary tumor are beneficial factors, whereas advanced age, poorly differentiated, undifferentiated, and lymph node metastasis are predictors of poor prognosis.