Effects of Cyclic Nucleotide-Gated Channels in Vestibular Nuclear Neurons / 전남의대학술지

This study was designed to investigate the effects an 8-Br-cGMP on the neuronal activity of rat vestibular nuclear cells. Sprague-Dawley rats aged 14 to 16 days were decapitated under ether anesthesia. After treatment with pronase and thermolysin, the dissociated vestibular nuclear cells were transferred into a chamber on an inverted microscope. Spontaneous action potentials and potassium currents were recorded by standard patch-clamp techniques under current and voltage-clamp modes. Twelve vestibular nuclear cells revealed excitatory responses to 1-5 microM of 8-Br-cGMP, and 3 neurons did not respond to 8-Br-cGMP. Whole potassium currents of vestibular nuclear cells were decreased by 8-Br-cGMP (n=12). After calcium-dependent potassium currents were blocked by tetraethylammonium, the potassium currents were not decreased by 8-Br-cGMP. These experimental results suggest that 8-Br-cGMP changes the neuronal activity of vestibular nuclear cells by blocking the calcium-dependent potassium currents that underlie the afterhyperpolarization.

Effects of Cyclic Nucleotide-Gated Channels in Vestibular Nuclear Neurons / 전남의대학술지

This study was designed to investigate the effects an 8-Br-cGMP on the neuronal activity of rat vestibular nuclear cells. Sprague-Dawley rats aged 14 to 16 days were decapitated under ether anesthesia. After treatment with pronase and thermolysin, the dissociated vestibular nuclear cells were transferred into a chamber on an inverted microscope. Spontaneous action potentials and potassium currents were recorded by standard patch-clamp techniques under current and voltage-clamp modes. Twelve vestibular nuclear cells revealed excitatory responses to 1-5 microM of 8-Br-cGMP, and 3 neurons did not respond to 8-Br-cGMP. Whole potassium currents of vestibular nuclear cells were decreased by 8-Br-cGMP (n=12). After calcium-dependent potassium currents were blocked by tetraethylammonium, the potassium currents were not decreased by 8-Br-cGMP. These experimental results suggest that 8-Br-cGMP changes the neuronal activity of vestibular nuclear cells by blocking the calcium-dependent potassium currents that underlie the afterhyperpolarization.

Culture of human intestinal epithelial cell using the dissociating enzyme thermolysin and endothelin-3

Epithelium, a highly dynamic system, plays a key role in the homeostasis of the intestine. However, thus far a human intestinal epithelial cell line has not been established in many countries. Fetal tissue was selected to generate viable cell cultures for its sterile condition, effective generation, and differentiated character. The purpose of the present study was to culture human intestinal epithelial cells by a relatively simple method. Thermolysin was added to improve the yield of epithelial cells, while endothelin-3 was added to stimulate their growth. By adding endothelin-3, the achievement ratio (viable cell cultures/total cultures) was enhanced to 60 percent of a total of 10 cultures (initiated from 8 distinct fetal small intestines), allowing the generation of viable epithelial cell cultures. Western blot, real-time PCR and immunofluorescent staining showed that cytokeratins 8, 18 and mouse intestinal mucosa-1/39 had high expression levels in human intestinal epithelial cells. Differentiated markers such as sucrase-isomaltase, aminopeptidase N and dipeptidylpeptidase IV also showed high expression levels in human intestinal epithelial cells. Differentiated human intestinal epithelial cells, with the expression of surface markers (cytokeratins 8, 18 and mouse intestinal mucosa-1/39) and secretion of cytokines (sucrase-isomaltase, aminopeptidase N and dipeptidylpeptidase IV), may be cultured by the thermolysin and endothelin-3 method and maintained for at least 20 passages. This is relatively simple, requiring no sophisticated techniques or instruments, and may have a number of varied applications.

Effects of NaOCl on the Intracellular Calcium Concentration in Rat Dorsal Root Ganglion Neurons

Recent studies have implicated reactive oxygen species (ROS) as determinants of the pathological pain caused by the activation of peripheral neurons. It has not been elucidated, however, how ROS activate the primary sensory neurons in the pain pathway. In this study, calcium imaging was performed to investigate the effects of NaOCl, a ROS donor, on the intracellular calcium concentration ([Ca2+]i) in acutely dissociated dorsal root ganglion (DRG) neurons. DRG was sequentially treated with 0.2 mg/ml of both protease and thermolysin, and single neurons were then obtained by mechanical dissociation. The administration of NaOCl then caused a reversible increase in the [Ca2+]i, which was inhibited by pretreatment with phenyl-N-tert-buthylnitrone (PBN) and isoascorbate, both ROS scavengers. The NaOCl-induced [Ca2+]i increase was suppressed both in a calcium free solution and after depletion of the intracellular Ca2+ pool by thapsigargin. Additionally, this increase was predominantly blocked by pretreatment with the transient receptor potential (TRP) antagonists, ruthenium red (50 microM) and capsazepine (10 microM). Collectively, these results suggest that an increase in the intracellular calcium concentration is produced from both extracellular fluid and the intracellular calcium store, and that TRP might be involved in the sensation of pain induced by ROS.

Thermolysin in human cultured keratinocyte isolation

BACKGROUND: When treating extensively burned patients using cultured epidermal sheets, the main problem is the time required for its production. Conventional keratinocyte isolation is usually done using Trypsin. We used a modification of the conventional isolation method in order to improve this process and increase the number of colonies from the isolated epidermal cell population. PURPOSE: To compare the action of trypsin and thermolysin in the keratinocyte isolation using newborn foreskin. METHODS: This method used thermolysin as it selectively digests the dermo-epidermal junction. After dermis separation, the epidermis was digested by trypsin in order to obtain a cell suspension. RESULTS: Compared to the conventional procedure, these experiments demonstrated that in the thermolysin group, the epidermis was easily detached from the dermis, there was no fibroblast contamination and there were a larger number of keratinocyte colonies which had a significant statistical difference. CONCLUSION: The number of colonies in the thermolysin group was significantly greater than in the trypsin group.

INTRODUÇÃO: No tratamento do paciente grande queimado, onde se usa lâminas de epiderme cultivadas, o principal problema é o tempo necessário para sua produção. O isolamento tradicional de queratinócitos utiliza normalmente tripsina. No presente estudo, foi utilizada uma modificação do método de isolamento tradicional, que poderia produzir uma maior pureza e um maior número de colônias formadas a partir da população de células epidérmicas isoladas. OBJETIVO: Comparar a ação da tripsina e da termolisina no isolamento de queratinócitos usando pele de prepúcio de récem-nascidos. MÉTODOS: Essa metodologia utilizou a termolisina, que realiza a separação seletiva entre a epiderme e a derme. Após essa separação, a epiderme foi submetida à ação da tripsina para a obtenção da suspensão celular. RESULTADOS: Comparado ao método convencional, os experimentos mostraram que no grupo da termolisina mostrou facilidade para a separação entre a epiderme e derme, não houve contaminação por fibroblastos e produziu um maior número de colônias formadas, com diferença estatística significante. CONCLUSÃO: O número de colônias no grupo termolisina foi significantemente maior que no grupo tripsina.

Ionic mechanisms underlying spontaneous firing in isolated type B medial vestibular nucleus neurons

Medial vestibular nucleus (MVN) neurons are found to have spontaneous electrical activity in the absence of any detectable synaptic input. To investigate the contributions of intrinsic mechanisms to the spontaneous activity of type B MVN neurons, we examined the effects of various channel blockers on spontaneous firing by means of patch clamp recordings. Coronal slice (400 micrometer) of the vestibular nucleus region was sequentially treated with pronase 0.2 mg/ml and thermolysin 0.2 mg/ml, then single neurons were mechanically dissociated. MVN neurons recorded in neonatal rat were shown to have either a single deep afterhyperpolarization (AHP; type A cells), or an early fast and a delayed slow AHP (type B cells). In 300 nM TTX, spontaneous firing was blocked in type B cells tested. In 8 of 11 cells, underlying fluctuation or oscillations in membrane potential was not remained, and hyperpolarization did not produce rebound low-threshold calcium spikes. Although type B MVN neurons possessed hyperpolarization activated cation current (Ih), cesium had no effect on firing rates. The spike AHP is calcium dependent. When Ca2+ influx was blocked in external Ca2+ free solution, repetitive firing was abolished and the cell rested at depolarized membrane potentials. Application of apamin (300 nM) caused a profound reduction in the amplitude of the AHP and produced rhythmic burst firing. These findings suggest that the spontaneous activity of type B MVN neurons is regulated by interactions between the membrane depolarization mainly due to a persistent sodium conductances and hyperpolarization due to the calcium-activated potassium conductances.

Synthesis of cholecystokinin peptide CCK-4 exclusively by enzymatic methods / 华中科技大学学报（医学）（英德文版）

The synthesis of CCK-4 (H-Trp-Met-Asp-Phe-NH2) by using enzymes exclusively was described. As protection group for the amino group we used the Phenylacetyl group (Phac) which had been cleaved at the end of the synthesis with Penicillin G Amidase (PGA) without affecting the peptide bonds. Thus, beginning with Phac-Trp-OH we had successfully synthesized the target peptide with following 4 enzymes, alpha-Chymotrypsin, Papain, Thermolysin and PGA in four reaction steps. All reactions were carried out in aqueous buffer in reasonable yields (> 65%). FAB-MS or FD-MS verified the correct molecular mass of all peptides.

Synthesis of cholecystokinin peptide CCK-4 exclusively by enzymatic methods / 华中科技大学学报（医学）（英德文版）

The synthesis of CCK-4 (H-Trp-Met-Asp-Phe-NH2) by using enzymes exclusively was described. As protection group for the amino group we used the Phenylacetyl group (Phac) which had been cleaved at the end of the synthesis with Penicillin G Amidase (PGA) without affecting the peptide bonds. Thus, beginning with Phac-Trp-OH we had successfully synthesized the target peptide with following 4 enzymes, alpha-Chymotrypsin, Papain, Thermolysin and PGA in four reaction steps. All reactions were carried out in aqueous buffer in reasonable yields (> 65%). FAB-MS or FD-MS verified the correct molecular mass of all peptides.

Voltage-Dependent Sodium And Potassium Currents In Acutely Isolated Rat Trigeminal Caudal Neurons

Voltage-Dependent Potassium Currents in Acutely Isolated Rat Medial Vestibular Nucleus Neurons / 대한이비인후과학회지

BACKGROUND AND OBJECTIVES: Medial vestibular nucleus (MVN) neurons are second-order afferent neurons that are involved in the reflex control of the head and eyes. Results from several studies utilizing the intracellular microelectrode recording techniques suggest the presence of several ionic conductances contributes to the regulation of the MVN neuron excitability in rats. In this study, the types and characteristics of voltage-dependent potassium currents were investigated in acutely isolated MVN neurons of postnatal rats. Material and Methods: Electrophysiological recordings were performed by means of the whole cell patch clamp techniques. Coronal slice (400 nm) of the vestibular nucleus region was sequentially treated with pronase 0.2 mg/ml and thermolysin 0.2 mg/ml, then single neurons were mechanically dissociated RESULTS: In a Ca2+ -free solution, low-threshold transient (IA) and high-threshold sustained (IK) currents were recorded. IK was activated (gamma=4.0-12.4 ms at 10 mV) and inactivated (gamma=180-720 ms at 10 mV) more slowly than IA. The half-maximum activation and inactivation potential were -3.1+/-3.4 mV and -38.8+/-3.6 mV, respectively. IA was activated rapidly (gamma=1.0-2.3 ms at 10 mV) and inactivated in 10-60 ms. The half-maximum activation and inactivation potentials were -22.3+/-4.5 mV and -58.4+/-3.8 mV, respectively. When a 4-aminopyridine of 10 mM was applied, IA was almost totally blocked. In a solution with 2 mM Ca2+, calcium dependent potassium currents were identified by application of a Ca2+ free solution and consisted of a transient and a sustained components. Exposure to 0.3 nM apamin induced a reversible reduction of a sustained components. CONCLUSION: These results suggest that MVN neurons express a variety of voltage-dependent potassium currents which are responsible for proper membrane excitability and firing of MVN neurons.

Thermolysin: a peptide forming enzyme.

Thermolysin, a thermostable endopeptidase, is recognised as a potential peptide bond forming enzyme. The importance of structural properties and its stereospecific nature towards peptide bond formation is described. Thermolysin's use in the keystep of the preparation of an artificial sweetener 'aspartame' is highlighted.