Voltage sensitive Ca2+ conductances mediating modulatory effects of neuropeptides in rat spinal dorsal horn neurons

Voltage-activated Ca[superscript]2+ currents in immature rat spinal dorsal horn neurons and their modulation by substance P (SP) and calcitonin gene-related peptide (CGRP) have been investigated by using single-electrode voltage-clamp technique in the transverse spinal cord slice preparation;Using experimental conditions that minimized voltage-dependent Na[superscript]+ and K[superscript]+ currents, we distinguished low- and high-voltage-activated Ca[superscript]2+ currents on the basis of their voltage dependence and sensitivity to the Ca[superscript]2+ channel agonist and antagonist drugs. The low-voltage-activated (LVA) transient Ca[superscript]2+ current is evoked with weak depolarizing voltage commands at potentials positive to -70 mV and reaches the peak value between -40 and -30 mV. Inactivation is complete at potentials in the range of -60 to -50 mV. The transient component of the high-voltage-activated (HVA) Ca[superscript]2+ current activates at membrane potentials close to -40 mV and decays with time constants ranging from 100-600 ms. The sustained component of the HVA Ca[superscript]2+ current activates at potentials positive to -40 mV and exhibits little inactivation during 0.3-0.5s depolarizing commands. Bay K 8644 enhanced selectively the sustained component of the HVA Ca[superscript]2+ current, whereas nifedipine reduced this component of Ca[superscript]2+ current. Cd[superscript]2+ and Co[superscript]2+ ions markedly reduced both the transient and sustained components of the HVA Ca[superscript]2+ current. Nickel ions reduced the LVA transient Ca[superscript]2+ current;Bath application of CGRP elicited hyperpolarization in both small and large DRG neurons that was associated with an increase in membrane input resistance. However, some large DRG neurons were depolarized by CGRP. In addition, CGRP produced an increase in the amplitude and the duration of the Ca[superscript]2+ spike and increased the voltage-dependent Ca[superscript]2+ current by enhancing both the transient and the sustained components of high-threshold Ca[superscript]2+ current;CGRP depolarized about one-third of the dorsal horn neurons and increased their input resistance and excitability. CGRP increased the amplitude of the fast excitatory postsynaptic potentials recorded in dorsal horn neurons in response to electrical stimulation of a lumbar dorsal root. The increase in Ca[superscript]2+ current in DRG neurons is likely to be responsible for the facilitation of excitatory synaptic transmission;SP enhanced a low-threshold, transient Ca[superscript]2+ current in rat dorsal horn neurons. This effect may be responsible for the increase in excitability produced by SP

Effect of Phosphatidylserine on Unitary Conductance and Ba2+ Block of the BK Ca2+–activated K+ Channel: Re-examination of the Surface Charge Hypothesis

Incorporation of BK Ca2+–activated K+ channels into planar bilayers composed of negatively charged phospholipids such as phosphatidylserine (PS) or phosphatidylinositol (PI) results in a large enhancement of unitary conductance (gch) in comparison to BK channels in bilayers formed from the neutral zwitterionic lipid, phospatidylethanolamine (PE). Enhancement of gch by PS or PI is inversely dependent on KCl concentration, decreasing from 70% at 10 mM KCl to 8% at 1,000 mM KCl. This effect was explained previously by a surface charge hypothesis (Moczydlowski, E., O. Alvarez, C. Vergara, and R. Latorre. 1985. J. Membr. Biol. 83:273–282), which attributed the conductance enhancement to an increase in local K+ concentration near the entryways of the channel. To test this hypothesis, we measured the kinetics of block by external and internal Ba2+, a divalent cation that is expected to respond strongly to changes in surface electrostatics. We observed little or no effect of PS on discrete blocking kinetics by external and internal Ba2+ at 100 mM KCl and only a small enhancement of discrete and fast block by external Ba2+ in PS-containing membranes at 20 mM KCl. Model calculations of effective surface potential sensed by the K+ conduction and Ba2+-blocking reactions using the Gouy-Chapman-Stern theory of lipid surface charge do not lend support to a simple electrostatic mechanism that predicts valence-dependent increase of local cation concentration. The results imply that the conduction pore of the BK channel is electrostatically insulated from the lipid surface, presumably by a lateral distance of separation (>20 Å) from the lipid head groups. The lack of effect of PS on apparent association and dissociation rates of Ba2+ suggest that lipid modulation of K+ conductance is preferentially coupled through conformational changes of the selectivity filter region that determine the high K+ flux rate of this channel relative to other cations. We discuss possible mechanisms for the effect of anionic lipids in the context of specific molecular interactions of phospholipids documented for the KcsA bacterial potassium channel and general membrane physical properties proposed to regulate membrane protein conformation via energetics of bilayer stress

Identification of Primo-Vascular System in Abdominal Subcutaneous Tissue Layer of Rats

The primo-vascular system (PVS) is a novel network identified in various animal tissues. However, the PVS in subcutaneous tissue has not been well identified. Here, we examined the putative PVS on the surface of abdominal subcutaneous tissue in rats. Hemacolor staining revealed dark blue threadlike structures consisting of nodes and vessels, which were frequently observed bundled with blood vessels. The structure was filled with various immune cells including mast cells and WBCs. In the structure, there were inner spaces (20–60 µm) with low cellularity. Electron microscopy revealed a bundle structure and typical cytology common with the well-established organ surface PVS, which were different from those of the lymphatic vessel. Among several subcutaneous (sc) PVS tissues identified on the rat abdominal space, the most outstanding was the scPVS aligned along the ventral midline. The distribution pattern of nodes and vessels in the scPVS closely resembled that of the conception vessel meridian and its acupoints. In conclusion, our results newly revealed that the PVS is present in the abdominal subcutaneous tissue layer and indicate that the scPVS tissues are closely correlated with acupuncture meridians. Our findings will help to characterize the PVS in the other superficial tissues and its physiological roles

A Critical Role for Myosin IIB in Dendritic Spine Morphology and Synaptic Function

Dendritic spines show rapid motility and plastic morphology, which may mediate information storage in the brain. It is presently believed that polymerization/depolymerization of actin is the primary determinant of spine motility and morphogenesis. Here, we show that myosin IIB, a molecular motor that binds and contracts actin filaments, is essential for normal spine morphology and dynamics and represents a distinct biophysical pathway to control spine size and shape. Myosin IIB is enriched in the postsynaptic density (PSD) of neurons. Pharmacologic or genetic inhibition of myosin IIB alters protrusive motility of spines, destabilizes their classical mushroom-head morphology, and impairs excitatory synaptic transmission. Thus, the structure and function of spines is regulated by an actin-based motor in addition to the polymerization state of actin

Expression of Keratin 10 in Rat Organ Surface Primo-vascular Tissues

AbstractThe primo-vascular system is described as the anatomical structure corresponding to acupuncture meridians and has been identified in several tissues in the body, but its detailed anatomy and physiology are not well understood. Recently, the presence of keratin 10 (Krt10) in primo-vascular tissue was reported, but this finding has not yet been confirmed. In this study, we compared Krt10 expression in primo-vascular tissues located on the surface of rat abdominal organs with Krt10 expression on blood and lymphatic vessels. Krt10 protein (approximately 56.5 kDa) was evaluated by western blot analysis and immunohistochemistry. Krt10 (IR) in the primo-node was visualized as patchy spots around each cell or as a follicle-like structure containing a group of cells. Krt10 IR was also identified in vascular and lymphatic tissues, but its distribution was diffuse over the extracellular matrix of the vessels. Thus Krt10 protein was expressed in all three tissues tested, but the expression pattern of Krt10 in primo-vascular tissue differed from those of blood and lymphatic vascular tissues, suggesting that structural and the regulatory roles of Krt10 in primo-vascular system are different from those in blood and lymphatic vessels

P2Y receptor regulation of sodium transport in human mammary epithelial cells

Primary human mammary epithelial (HME) cells were immortalized by stable, constitutive expression of the catalytic subunit of human telomerase. Purinergic receptors were identified by RT-PCR and quantitative RT-PCR from mRNA isolated from primary and immortalized cells grown to confluence on membrane filters. Several subtypes of P2Y receptor mRNA were identified including P2Y1, P2Y2, P2Y4, and P2Y6 receptors. RT-PCR experiments also revealed expression of A2b adenosine receptor mRNA in primary and immortalized cells. Confluent monolayers of HME cells exhibited a basal short-circuit current (Isc) that was abolished by amiloride and benzamil. When monolayers were cultured in the presence of hydrocortisone, mRNA expression of Na+ channel (ENaC) -, β-, and -subunits increased approximately threefold compared with that in cells grown without hydrocortisone. In addition, basal benzamil-sensitive Na+ transport was nearly twofold greater in hydrocortisone-treated monolayers. Stimulation with UTP, UDP, or adenosine 5'-O-(3-thiotriphosphate) (ATPS) produced increases in intracellular calcium concentration that were significantly reduced following pretreatment with the calcium-chelating agent BAPTA-AM. Concentration-response relationships indicated that the rank order of potency for these agonists was UTP > UDP > ATPS. Basolateral stimulation with UTP produced a rapid but transient increase in Isc that was significantly reduced if cells were pretreated with BAPTA-AM or benzamil. Moreover, basolateral treatment with either charybdotoxin or clotrimazole significantly inhibited the initial UTP-dependent increase in Isc and eliminated the sustained current response. These results indicate that human mammary epithelial cells express multiple P2 receptor subtypes and that Ca2+ mobilization evoked by P2Y receptor agonists stimulates Na+ absorption by increasing the activity of Ca2+-activated K+ channels located in the basolateral membrane.This work was partly supported by Korea Research Foundation Grant KRF-005-E00076 (to S. Y. Lee) and National Institutes of Health Grants AI-50494 and DK-74010 (to S. M. O'Grady)

Gateway RFP-fusion vectors for high-throughput functional analysis of genes

There is an increasing demand for high throughput (HTP) methods for gene analysis on a genome-wide scale. However, the current repertoire of HTP detection methodologies allows only a limited range of cellular phenotypes to be studied. We have constructed two HTP-optimized expression vectors generated from the red fluorescent reporter protein (RFP) gene. These vectors produce RFP-tagged target proteins in a multiple expression system using gateway cloning technology (GCT). The RFP tag was fused with the cloned genes, thereby allowing us localize the expressed proteins in mammalian cells. The effectiveness of the vectors was evaluated using an HTP-screening system. Sixty representative human C2 domains were tagged with RFP and overexpressed in HiB5 neuronal progenitor cells, and we studied in detail two C2 domains that promoted the neuronal differentiation of HiB5 cells. Our results show that the two vectors developed in this study are useful for functional gene analysis using an HTP-screening system on a genome-wide scale.We appreciate the helpful advice of Dr. Tobias Meyer and Dr. Won Do Heo of Stanford University in the construction of the set of entry clones of human C2 domains. This work was supported by a grant from the Basic Research Program of the Korea Science and Engineering Foundation (R01-2002- 000-00128-0), and a Korea Research Foundation Grant (KRF- 2006-005-J04204)

Physicochemical factors that affect electroporation of lung cancer and normal cell lines

Electroporation is used for cancer therapy to efficiently destroy cancer tissues by transferring anticancer drugs into cancer cells or by irreversible tumor ablation without resealing pores. There is growing interest in the electroporation method for the treatment of lung cancer, which has the highest mortality rate among cancers. Improving the cancer cell selectivity has the potential to expand its use. However, the factors that influence the cell selectivity of electroporation are debatable. We aimed to identify the important factors that influence the efficiency of electroporation in lung cells. The electropermeabilization of lung cancer cells (H460, A549, and HCC1588) and normal lung cells (MRCS, WI26 and L132) was evaluated by the transfer of fluorescence dyes. We found that membrane permeabilization increased as cell size, membrane stiffness, resting transmembrane potential, and lipid cholesterol ratio increased. Among them, lipid composition was found to be the most relevant factor in the electroporation of lung cells. Our results provide insight into the differences between lung cancer cells and normal lung cells and provide a basis for enhancing the sensitivity of lung cancers cells to electroporation. (C) 2019 Elsevier Inc. All rights reserved.N

Organotypic slice culture of the hypothalamic paraventricular nucleus of rat

Organotypic slice cultures have been developed as an alternative to acute brain slices because the neuronal viability and synaptic connectivity in these cultures can be preserved well for a prolonged period of time. This study evaluated a stationary organotypic slice culture developed for the hypothalamic paraventricular nucleus (PVN) of rat. The results showed that the slice cultures maintain the typical shape of the nucleus, the immunocytochemical signals for oxytocin, vasopressin, and corticotropin-releasing hormone, and the electrophysiological properties of PVN neurons for up to 3 weeks in vitro. The PVN neurons in the culture expressed the green fluorescent protein gene that had been delivered by the adenoviral vectors. The results indicate that the cultured slices preserve the properties of the PVN neurons, and can be used in longterm studies on these neurons in vitro

Infrared spectroscopy characterization of normal and lung cancer cells originated from epithelium

The vibrational spectral differences of normal and lung cancer cells were studied for the development of effective cancer cell screening by means of attenuated total reflection infrared spectroscopy. The phosphate monoester symmetric stretching νs(PO32-) band intensity at ~970 cm-1 and the phosphodiester symmetric stretching νs(PO2-) band intensity at ~1,085 cm-1 in nucleic acids and phospholipids appeared to be significantly strengthened in lung cancer cells with respect to the other vibrational bands compared to normal cells. This finding suggests that more extensive phosphorylation occur in cancer cells. These results demonstrate that lung cancer cells may be prescreened using infrared spectroscopy tools