scholarly journals Ion Transport and Membrane Potential in CNS Myelinated Axons I. Normoxic Conditions

1997 ◽  
Vol 78 (4) ◽  
pp. 2086-2094 ◽  
Author(s):  
Lisa Leppanen ◽  
Peter K. Stys
Keyword(s):  
Membrane Potential ◽  
Optic Nerve ◽  
Ion Transport ◽  
Transport Systems ◽  
Resting Membrane Potential ◽  
High Dose ◽  
Myelinated Axons ◽  
Gap Technique ◽  
Influx Pathways ◽  
Dose Dependent

Leppanen, Lisa and Peter K. Stys. Ion transport and membrane potential in CNS myelinated axons. I. Normoxic conditions. J. Neurophysiol. 78: 2086–2094, 1997. Compound resting membrane potential was recorded by the grease gap technique during normoxic conditions (37°C) in rat optic nerve, a representative CNS myelinated tract. Mean potential was −47 ± 3 (SD) mV and remained stable for 2–3 h. Input impedance of a single optic nerve axon was calculated to be ≈5 GΩ. Contribution of the Na+ pump to resting axonal potential is estimated at −7 mV. Ouabain (10 μM to 10 mM) evoked a dose-dependent depolarization that was maximal at ≥1 mM, depolarizing the nerves to ∼35–40% of control after 60 min. Inhibiting energy metabolism (CN− and iodoacetate) during high-dose ouabain (1–10 mM) exposure caused an additional depolarization, suggesting additional ATP-dependent, ouabain-insensitive ion transport systems. Perfusion with zero-Na+ (choline substituted) caused a transient hyperpolarization, that was greater than with tetrodotoxin (TTX; 1 μM) alone, indicating both TTX-sensitive and -insensitive Na+ influx pathways in resting rat optic nerve axons. Resting probability (P)K:PNa is calculated at 20:1. In contrast to choline-substituted solution, Li+-substituted zero-Na+ perfusate caused a rapid depolarization due to Na+ pump inhibition and the ability of Li+ to permeate the Na+ channel. TTX reduced, but did not prevent, ouabain- or zero-Na+/Li+–induced depolarization. We conclude that the primary Na+ influx path in resting rat optic nerve axons is the TTX-sensitive Na+ channel, with evidence for additional TTX-insensitive routes permeable to Na+ and Li+. In addition, maintenance of membrane potential is critically dependent on continuous Na+ pump activity due to the relatively high exchange of Na+ (via the above mentioned routes) and K+ across the membrane of resting optic axons.

Effect of aminophylline on the contraction threshold of rat diaphragm fibers

1991 ◽  
Vol 71 (4) ◽  
pp. 1409-1414 ◽  
Author(s):  
A. S. Losavio ◽  
B. A. Kotsias
Keyword(s):  
Membrane Potential ◽  
Sarcoplasmic Reticulum ◽  
Resting Membrane Potential ◽  
Dependent Manner ◽  
Direct Visualization ◽  
Rat Diaphragm ◽  
Current Clamp ◽  
Cyclic Monophosphate ◽  
Dose Dependent

We studied the effect of aminophylline (0.1–1 mM) on the contraction threshold (CT) of rat diaphragm fibers (25 degrees C). The CT was measured by direct visualization (x200) of the fiber under current-clamp conditions. The main findings are the following: 1) Aminophylline lowers the CT, in a dose-dependent manner, toward more negative values of the resting membrane potential (Vm). 2) Dibutyryl adenosine 3′,5′-cyclic monophosphate (2 mM) shifts the CT, although this change is smaller than in the presence of xanthine. 3) Tetracaine (1 mM), a drug that diminishes Ca release from the sarcoplasmic reticulum, reduces the shift induced by 1 mM aminophylline; this is partially overcome by increasing aminophylline concentration to 5 mM. 4) Hyperpolarization of the fibers shifts the CT to more negative Vm. We suggest that the displacement in the CT to more negative Vm plays an important role in the potentiating effect of aminophylline. This could be the result of an enhancement of Ca release from the sarcoplasmic reticulum.

Ion Transport and Membrane Potential in CNS Myelinated Axons II. Effects of Metabolic Inhibition

1997 ◽  
Vol 78 (4) ◽  
pp. 2095-2107 ◽  
Author(s):  
Lisa Leppanen ◽  
Peter K. Stys
Keyword(s):  
Membrane Potential ◽  
Oxidative Phosphorylation ◽  
Ion Transport ◽  
Phase 1 ◽  
Phase 2 ◽  
Myelinated Axons ◽  
Phase 3 ◽  
Hyperpolarizing Response ◽  
Response Phase ◽  
Chemical Anoxia

Leppanen, Lisa and Peter K. Stys. Ion transport and membrane potential in CNS myelinated axons. II. Effects of metabolic inhibition. J. Neurophysiol. 78: 2095–2107, 1997. Compound resting membrane potential was recorded by the grease gap technique (37°C) during glycolytic inhibition and chemical anoxia in myelinated axons of rat optic nerve. The average potential recorded under control conditions (no inhibitors) was −47 ± 3 (SD) mV and was stable for 2–3 h. Zero glucose (replacement with sucrose) depolarized the nerve in a monotonic fashion to 55 ± 10% of control after 60 min. In contrast, glycolytic inhibition with deoxyglucose (10 mM, glucose omitted) or iodoacetate (1 mM) evoked a characteristic voltage trajectory consisting of four distinct phases. A distinct early hyperpolarizing response ( phase 1) was followed by a rapid depolarization ( phase 2). Phase 2 was interrupted by a second late hyperpolarizing response ( phase 3), which led to an abrupt reduction in the rate of potential change, causing nerves to then depolarize gradually ( phase 4) to 75 ± 9% and 55 ± 6% of control after 60 min, in deoxyglucose and iodoacetate, respectively. Pyruvate (10 mM) completely prevented iodoacetate-induced depolarization. Effects of glycolytic inhibitors were delayed by 20–30 min, possibly due to continued, temporary oxidative phosphorylation using alternate substrates through the tricarboxylic acid cycle. Chemical anoxia (CN− 2 mM) immediately depolarized nerves, and phase 1 was never observed. However a small inflection in the voltage trajectory was typical after ≈10 min. This was followed by a slow depolarization to 34 ± 4% of control resting potential after 60 min of CN−. Addition of ouabain (1 mM) to CN−-treated nerves caused an additional depolarization, indicating a minor glycolytic contribution to the Na+-K+-ATPase, which is fueled preferentially by ATP derived from oxidative phosphorylation. Phases 1 and 3 during iodoacetate exposure were diminished under nominally zero Ca2+ conditions and abolished with the addition of the Ca2+ chelator ethylene glycol-bis(β-aminoethyl ether)- N,N,N′,N′-tetraacetic acid (EGTA; 5 mM). Tetraethylammonium chloride (20 mM) also reduced phase 1 and eliminated phase 3. The inflection observed with CN− was eliminated during exposure to zero-Ca2+/EGTA. A Ca2+-activated K+ conductance may be responsible for the observed hyperpolarizing inflections. Block of Na+ channels with tetrodotoxin (TTX; 1 μM) or replacement of Na+ with the impermeant cation choline significantly reduced depolarization during glycolytic inhibition with iodoacetate or chemical anoxia. The potential-sparing effects of TTX were less than those of choline-substituted perfusate, suggesting additional, TTX-insensitive Na+ influx pathways in metabolically compromised axons. The local anesthetics, procaine (1 mM) and QX-314 (300 μM), had similar effects to TTX. Taken together, the rate and extent of depolarization of metabolically compromised axons is dependent on external Na+. The Ca2+-dependent hyperpolarizing phases and reduction in rate of depolarization at later times may reflect intrinsic mechanisms designed to limit axonal injury during anoxia/ischemia.

scholarly journals Expression, localization, and functional properties of inwardly rectifying K+ channels in the kidney

2020 ◽  
Vol 318 (2) ◽  
pp. F332-F337 ◽  
Author(s):  
Anna D. Manis ◽  
Matthew R. Hodges ◽  
Alexander Staruschenko ◽  
Oleg Palygin
Keyword(s):  
Membrane Potential ◽  
Ion Transport ◽  
Functional Properties ◽  
Current Knowledge ◽  
Cell Types ◽  
Resting Membrane Potential ◽  
K Channels ◽  
Multiple Organs ◽  
Inwardly Rectifying ◽  
Made In

Inwardly rectifying K+ (Kir) channels are expressed in multiple organs and cell types and play critical roles in cellular function. Most notably, Kir channels are major determinants of the resting membrane potential and K+ homeostasis. The renal outer medullary K+ channel (Kir1.1) was the first renal Kir channel identified and cloned in the kidney over two decades ago. Since then, several additional members, including classical and ATP-regulated Kir family classes, have been identified to be expressed in the kidney and to contribute to renal ion transport. Although the ATP-regulated Kir channel class remains the most well known due to severe pathological phenotypes associated with their mutations, progress is being made in defining the properties, localization, and physiological functions of other renal Kir channels, including those localized to the basolateral epithelium. This review is primarily focused on the current knowledge of the expression and localization of renal Kir channels but will also briefly describe their proposed functions in the kidney.

Synthesis and Biological Evaluation of Novel Heterocyclic Imines Linked Coumarin- Thiazole Hybrids as Anticancer Agents

2019 ◽  
Vol 19 (4) ◽  
pp. 557-566 ◽  
Author(s):  
Nerella S. Goud ◽  
Mahammad S. Ghouse ◽  
Jatoth Vishnu ◽  
Jakkula Pranay ◽  
Ravi Alvala ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Membrane Potential ◽  
Fluorescence Spectroscopy ◽  
Mitochondrial Membrane Potential ◽  
Mitochondrial Membrane ◽  
Annexin V ◽  
Biological Evaluation ◽  
Dependent Manner ◽  
Dapi Staining ◽  
Dose Dependent

Background: Human Galectin-1, a protein of lectin family showing affinity towards β-galactosides has emerged as a critical regulator of tumor progression and metastasis, by modulating diverse biological events including homotypic cell aggregation, migration, apoptosis, angiogenesis and immune escape. Therefore, galectin-1 inhibitors might represent novel therapeutic agents for cancer. Methods: A new series of heterocyclic imines linked coumarin-thiazole hybrids (6a-6r) was synthesized and evaluated for its cytotoxic potential against a panel of six human cancer cell lines namely, lung (A549), prostate (DU-145), breast (MCF-7 & MDA-MB-231), colon (HCT-15 & HT-29) using MTT assay. Characteristic apoptotic assays like DAPI staining, cell cycle, annexin V and Mitochondrial membrane potential studies were performed for the most active compound. Furthermore, Gal-1 inhibition was confirmed by ELISA and fluorescence spectroscopy. Results: Among all, compound 6g 3-(2-(2-(pyridin-2-ylmethylene) hydrazineyl) thiazol-4-yl)-2H-chromen-2- one exhibited promising growth inhibition against HCT-15 colorectal cancer cells with an IC50 value of 1.28 ± 0.14 µM. The characteristic apoptotic morphological features like chromatin condensation, membrane blebbing and apoptotic body formation were clearly observed with compound 6g on HCT-15 cells using DAPI staining studies. Further, annexin V-FITC/PI assay confirmed effective early apoptosis induction by treatment with compound 6g. Loss of mitochondrial membrane potential and enhanced ROS generation were confirmed with JC-1 and DCFDA staining method, respectively by treatment with compound 6g, suggesting a possible mechanism for inducing apoptosis. Moreover, flow cytometric analysis revealed that compound 6g blocked G0/G1 phase of the cell cycle in a dose-dependent manner. Compound 6g effectively reduced the levels of Gal-1 protein in a dose-dependent manner. The binding constant (Ka) of 6g with Gal-1 was calculated from the intercept value which was observed as 1.9 x 107 M-1 by Fluorescence spectroscopy. Molecular docking studies showed strong interactions of compound 6g with Gal-1 protein. Conclusion: Our studies demonstrate the anticancer potential and Gal-1 inhibition of heterocyclic imines linked coumarin-thiazole hybrids.

scholarly journals High-dose Glycerol Monolaurate Up-Regulated Beneficial Indigenous Microbiota without Inducing Metabolic Dysfunction and Systemic Inflammation: New Insights into Its Antimicrobial Potential

Nutrients ◽  
2019 ◽  
Vol 11 (9) ◽  
pp. 1981 ◽  
Author(s):  
Qiufen Mo ◽  
Aikun Fu ◽  
Lingli Deng ◽  
Minjie Zhao ◽  
Yang Li ◽  
...  
Keyword(s):  
Lipid Metabolism ◽  
Systemic Inflammation ◽  
Body Weight Gain ◽  
High Dose ◽  
Dependent Manner ◽  
Glucose And Lipid Metabolism ◽  
Glycerol Monolaurate ◽  
Indigenous Microbiota ◽  
Anti Inflammatory ◽  
Dose Dependent

Glycerol monolaurate (GML) has potent antimicrobial and anti-inflammatory activities. The present study aimed to assess the dose-dependent antimicrobial-effects of GML on the gut microbiota, glucose and lipid metabolism and inflammatory response in C57BL/6 mice. Mice were fed on diets supplemented with GML at dose of 400, 800 and 1600 mg kg−1 for 4 months, respectively. Results showed that supplementation of GML, regardless of the dosages, induced modest body weight gain without affecting epididymal/brown fat pad, lipid profiles and glycemic markers. A high dose of GML (1600 mg kg−1) showed positive impacts on the anti-inflammatory TGF-β1 and IL-22. GML modulated the indigenous microbiota in a dose-dependent manner. It was found that 400 and 800 mg kg−1 GML improved the richness of Barnesiella, whereas a high dosage of GML (1600 mg kg−1) significantly increased the relative abundances of Clostridium XIVa, Oscillibacter and Parasutterella. The present work indicated that GML could upregulate the favorable microbial taxa without inducing systemic inflammation and dysfunction of glucose and lipid metabolism.

scholarly journals Dose-dependent response to infection with SARS-CoV-2 in the ferret model and evidence of protective immunity

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Kathryn A. Ryan ◽  
Kevin R. Bewley ◽  
Susan A. Fotheringham ◽  
Gillian S. Slack ◽  
Phillip Brown ◽  
...  
Keyword(s):  
Protective Immunity ◽  
Viral Rna ◽  
Dose Titration ◽  
High Dose ◽  
Lung Pathology ◽  
Upper Respiratory Tract ◽  
Virus Shedding ◽  
Upper Respiratory ◽  
Dose Dependent ◽  
Titration Study

AbstractThere is a vital need for authentic COVID-19 animal models to enable the pre-clinical evaluation of candidate vaccines and therapeutics. Here we report a dose titration study of SARS-CoV-2 in the ferret model. After a high (5 × 106 pfu) and medium (5 × 104 pfu) dose of virus is delivered, intranasally, viral RNA shedding in the upper respiratory tract (URT) is observed in 6/6 animals, however, only 1/6 ferrets show similar signs after low dose (5 × 102 pfu) challenge. Following sequential culls pathological signs of mild multifocal bronchopneumonia in approximately 5–15% of the lung is seen on day 3, in high and medium dosed groups. Ferrets re-challenged, after virus shedding ceased, are fully protected from acute lung pathology. The endpoints of URT viral RNA replication & distinct lung pathology are observed most consistently in the high dose group. This ferret model of SARS-CoV-2 infection presents a mild clinical disease.

scholarly journals A rodent model of human dose-equivalent progestin-only implantable contraception

2021 ◽  
Vol 19 (1) ◽  
Author(s):  
Heather C. M. Allaway ◽  
Roger A. Pierson ◽  
Jesse Invik ◽  
Susan A. Bloomfield
Keyword(s):  
Repeated Measures ◽  
Ovarian Function ◽  
Virgin Female ◽  
Rodent Model ◽  
High Dose ◽  
Corpora Lutea ◽  
Average Dose ◽  
Estrus Cycle ◽  
Human Dose ◽  
Dose Dependent

Abstract Background Long-acting, reversible contraceptives (LARC; progestin only) are an increasingly common hormonal contraceptive choice in reproductive aged women looking to suppress ovarian function and menstrual cyclicity. The overall objective was to develop and validate a rodent model of implanted etonogestrel (ENG) LARC, at body size equivalent doses to the average dose received by women during each of the first 3 years of ENG subdermal rod LARC use. Methods Intact, virgin, female Sprague-Dawley rats (16-wk-old) were randomized to 1 of 4 groups (n = 8/group) of ENG LARC (high-0.30μg/d, medium-0.17μg/d, low-0.09μg/d, placebo-0.00μg/d) via a slow-release pellet implanted subcutaneously. Animals were monitored for 21 days before and 29 days following pellet implantation using vaginal smears, ultrasound biomicroscopy (UBM), saphenous blood draws, food consumption, and body weights. Data were analyzed by chi-square, non-parametric, univariate, and repeated measures 2-way ANOVA. Results Prior to pellet implantation there was no difference in time spent in estrus cycle phases among the treatment groups (p > 0.30). Following pellet implantation there was a dose-dependent impact on the time spent in diestrus and estrus (p < 0.05), with the high dose group spending more days in diestrus and fewer days in estrus. Prior to pellet insertion there was not an association between treatment group and estrus cycle classification (p = 0.57) but following pellet implantation there was a dose-dependent association with cycle classification (p < 0.02). Measurements from the UBM (ovarian volume, follicle count, corpora lutea count) indicate an alteration of ovarian function following pellet implantation. Conclusion Assessment of estrus cyclicity indicated a dose-response relationship in the shift to a larger number of acyclic rats and longer in duration spent in the diestrus phase. Therefore, each dose in this model mimics some of the changes observed in the ovaries of women using ENG LARC and provides an opportunity for investigating the impacts on non-reproductive tissues in the future.

scholarly journals Early and Late Cytologic Effects of Whole Body Irradiation on Human Marrow

Blood ◽  
1964 ◽  
Vol 23 (4) ◽  
pp. 471-487 ◽  
Author(s):  
T. M. FLIEDNER ◽  
GOULD A. ANDREWS ◽  
EUGENE P. CRONKITE ◽  
VICTOR P. BOND
Keyword(s):  
Dose Group ◽  
Animal Experiments ◽  
Giant Cells ◽  
Whole Body ◽  
High Dose ◽  
Multinucleated Cells ◽  
Exposed Individual ◽  
Interphase Cells ◽  
Cytologic Abnormalities ◽  
Dose Dependent

Abstract 1. Serial marrow studies were performed during the first few days in eight men accidentally exposed to a mixed neutron gamma irradiation. They showed the occurrence of a wave of cytologic abnormalities. These were identical with those seen in animal experiments 1-3 days after whole body irradiation. They were considered to be "mitotically connected" (M. C. Abn.) and included the occurrence of chromosomal bridges and chromosomal fragments in mitoses. In interphase cells, the main abnormalities were nuclear fragments ("karyomeres") in the cytoplasm of erythroblasts, myelocytic cells and lymphocytes; bi- and multinucleated cells; and giant cells. The peak of abnormalities in the erythropoietic forms was reachéd after 2 days; that in the myelopoietic cells 4 days after exposure. On the 4th day, there was a distinct dose-dependent difference in these abnormalities between the high dose group (236-365 rads) and the low dose group (22-68 rads). 2. Some cytologic abnormalities, as seen in increased regeneratory activity of the marrow, were found in marrow smears 3.5 years after the accident, although the peripheral blood counts and mitotic indices of the marrow were within normal range. Their significance is obscure. 3. A careful cytologic evaluation of serially aspirated marrow samples during the first hours and days after whole body exposure proves to be an additional important aid in the assessment of the exposed individual and may well prove to be useful in determining the degree of injury and thus the prognosis.

scholarly journals Effect of Synchronous Versus Sequential Regimens on the Pharmacokinetics and Biodistribution of Regorafenib with Irradiation

Pharmaceutics ◽  
2021 ◽  
Vol 13 (3) ◽  
pp. 386
Author(s):  
Tung-Hu Tsai ◽  
Yu-Jen Chen ◽  
Li-Ying Wang ◽  
Chen-Hsi Hsieh
Keyword(s):  
Stereotactic Body Radiation Therapy ◽  
In Vivo Studies ◽  
Control Group ◽  
High Dose ◽  
Dependent Manner ◽  
Hep G2 ◽  
Time Curve ◽  
Dose Dependent

This study was performed to evaluate the interaction between conventional or high-dose radiotherapy (RT) and the pharmacokinetics (PK) of regorafenib in concurrent or sequential regimens for the treatment of hepatocellular carcinoma. Concurrent and sequential in vitro and in vivo studies of irradiation and regorafenib were designed. The interactions of RT and regorafenib in vitro were examined in the human hepatoma Huh-7, HA22T and Hep G2 cell lines. The RT–PK phenomenon and biodistribution of regorafenib under RT were confirmed in a free-moving rat model. Regorafenib inhibited the viability of Huh-7 cells in a dose-dependent manner. Apoptosis in Huh-7 cells was enhanced by RT followed by regorafenib treatment. In the concurrent regimen, RT decreased the area under the concentration versus time curve (AUC)regorafenib by 74% (p = 0.001) in the RT2 Gy × 3 fraction (f’x) group and by 69% (p = 0.001) in the RT9 Gy × 3 f’x group. The AUCregorafenib was increased by 182.8% (p = 0.011) in the sequential RT2Gy × 1 f’x group and by 213.2% (p = 0.016) in the sequential RT9Gy × 1 f’x group. Both concurrent regimens, RT2Gy × 3 f’x and RT9Gy × 3 f’x, clearly decreased the biodistribution of regorafenib in the heart, liver, lung, spleen and kidneys, compared to the control (regorafenib × 3 d) group. The concurrent regimens, both RT2Gy × 3 f’x and RT9Gy × 3 f’x, significantly decreased the biodistribution of regorafenib, compared with the control group. The PK of regorafenib can be modulated both by off-target irradiation and stereotactic body radiation therapy (SBRT).

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