Upper storage-capacity limit and multiple occupancy phenomena in H2-hydroquinone clathrates using Monte Carlo and DFT simulations.

The upper hydrogen-storage capacity limit of the ß-hydroquinone clathrate has been investigated using hybrid Grand-Canonical Monte Carlo/Molecular Dynamics simulations, for temperatures ranging from 77 K to 300 K. The evolution with pressure of the cage occupancies has been monitored in detail, describing the progressive nature of the uptake process. It is found that the storage capacity of the pure ß-HQ + H2 clathrate could reach 0.6 wt% (weight percentage) only for pressures above 1400 bar, at ambient temperature. The enhancement of the storage capacities by the multiple occupancy phenomenom was accordingly shown to be very limited by the need for extreme conditions. Following this observation, an unmodified version of the van der Waals & Platteeuw theory was applied allowing for the prediction of experimentally accessible formation pressures. Density functional theory calculations were addittionnaly performed to comprehensively characterize the hydrogen diffusion process within the clathrate crystalline structure, considering different occupancy scenarios.

High molar ratios of tumor necrosis factor α (TNF α) soluble receptors I and II to the TNF ligand in human plasma from male veterans with comorbid posttraumatic stress disorder (PTSD) and mild traumatic brain injury (mTBI).

Background and Objectives: Posttraumatic stress disorder (PTSD) and traumatic brain injury (TBI) are associated with chronic inflammation, as inferred from increased, but variable, peripheral levels of cytokines. We sought proof of concept for the notion that peripheral cytokine binding proteins and/or soluble receptors can confound measures of cytokines in those with a history of physical and psychological traumatic exposures. Efforts were focused on one of the major cytokines involved in inflammation, tumor necrosis factor-α (TNF-α). Methods: We examined blood plasma concentrations of TNF-α, its soluble receptors (TNF-soluble receptors (sR) I and TNFsRII), and C-reactive protein (CRP-1) in a cohort of US Veterans. In a previous study, CRP-1 was shown to be reduced by probiotic anti-inflammatory treatment in this patient cohort. All participants (n = 22) were diagnosed with PTSD and had a history of mild TBI with persistent post-concussive symptoms. Exclusion criteria included medications directly targeting inflammation. Results: Molar concentrations of soluble TNFsRI and II exceeded concentrations of the TNF-α ligand. TNFsRI, but not TNFsRII, was significantly associated with CRP-1 (Spearman Rho correlations = 0.518; p=.016 and 0.365; p = .104, respectively). Conclusions: TNF soluble receptors may bind to and sequester free TNF-α, suggesting that only measuring ligand concentrations may not provide a fully comprehensive view of inflammation, and potentially lead to inaccurate conclusions. TNFsRI concentration may provide a better estimate of inflammation than TNF-α for those with PTSD and post-acute mTBI with post-concussive symptoms, a hypothesis that invites further testing in larger studies.

Density functional theory of alkali metals at the IL/graphene electrochemical interface.

The mechanism of charge transfer between metal ions and graphene in the presence of an ionic liquid (1-butyl-3-methylimidazolium tetrafluoroborate) is investigated by means of density functional theory calculations. For that purpose, two different comparisons are established: (i) the behavior of Li+ and K+ when adsorbed onto the basal plane of graphene and (ii) the differences between Li+ approaching the carbon surface from the basal plane and being intercalated through the edge plane of trilayer graphene. In the first case, it is found that the metal ions must overcome high energy barriers due to their interaction with the ionic liquid before reaching an equilibrium position close to the interface. In addition, no significant charge transfer between any of the metals and graphene takes place until very close energetically unfavorable distances. The second configuration shows that Li+ has no equilibrium position in the proximity of the interface but instead has an equilibrium position when it is inside the electrode for which it has to cross an energy barrier. In this case, the formation of a LiC12 complex is observed since the charge transfer at the equilibrium distance is achieved to a considerable extent. Thus, the interfacial charge transfer resistance on the electrode in energy devices based on ionic liquids clearly depends not only on the binding of the ionic liquid to the metal cations and their ability to form a dense solvation shell around them but also on the surface topography and its effect on the ion packing on the surface.

Transversus abdominis release with biosynthetic mesh for large ventral hernia repair: a 5-year analysis of clinical outcomes and quality of life.

INTRODUCTION: Transversus abdominis release (TAR) may provide an optimal plane for mesh placement for large ventral hernias requiring medial myofascial flap advancement. Long-term outcomes of TAR for large ventral hernia repair (VHR) remains under-studied. This study aims to assess longitudinal clinical outcomes and quality of life (QoL) following large VHR with TAR and resorbable biosynthetic mesh. METHODS: Retrospective review of clinical outcomes and prospective QoL was performed for patients undergoing VHR with poly-4-hydroxybutyrate mesh and TAR from 2016 to 2021. Patients with ≤ 24 months of follow-up, defects ≤ 150 cm2, and parastomal hernias were excluded. Cost-related data was collected for each patient's hospital course. QoL was compared using paired Wilcoxon signed-rank tests. RESULTS: Twenty-nine patients met inclusion criteria. Median age and BMI were 61 years (53.2-68.1 years) and 31.4 kg/m2 (26.1-35.3 kg/m2). Average hernia defect was 390cm2 ± 152.9 cm2. All patients underwent previous abdominal surgery and were primarily Ventral Hernia Working Group 2 (58.6%). Two hernia recurrences (6.9%) occurred over the median follow-up period of 63.1 months (IQR 43.7-71.3 months), with no cases of mesh infection or explantation. Delayed healing and seroma occurred in 27 and 10.3% of patients, respectively. QoL analysis identified a significant improvement in postoperative QoL (p < 0.005), that continued throughout the 5-year follow-up period, with a 41% overall improvement. Cost analysis identified the hospital revenue generated was approximately equal to the direct costs of patient care. Higher costs were associated with ASA class and length of stay (p < 0.05). CONCLUSION: Large VHR with resorbable biosynthetic mesh and TAR can be performed safely, with a low recurrence and complication rate, acceptable hospital costs, and significant improvement in disease-specific QoL at long-term follow-up.

Interactions of Glutamate and Gamma Amino Butyric Acid with the insulin-like growth factor system in traumatic brain injury (TBI) and/or cardiovascular accidents (CVA or stroke): A systematic review.

The brain maintains homeostasis of neural excitation in part through the receptor-mediated signaling of Glutamate (Glu) and Gamma Amino Butyric Acid (GABA), but localized injuries cause cellular release of excess Glu leading to neurotoxicity. The literature strongly supports the role of Insulin-like growth factor-1 (IGF-1) in adult brain neuroprotection and repair, and research supporting the existence of molecular interactions between Glu, GABA, and IGF-1 in vitro and in normal animals raises the question of whether and/or how the Glu/GABA system interacts with IGF-1 post-injury. This systematic review was undertaken to explore works addressing this question among adults with a history of traumatic brain injury (TBI) and/or cerebrovascular accident (CVA; stroke). The literature was searched for human and animal studies and only four animal papers met inclusion criteria. The SYRCLE criteria was used to evaluate risk of bias; results varied between categories and papers. All the included studies, one on TBI and three on stroke, supported the molecular relationship between the excitatory and IGF-1 systems; two studies provided direct, detailed molecular evidence. The results point to the importance of research on the role of this protective system in pathological brain injury; a hypothetical proposal for future studies is presented.

[Mortality rate after a hip fracture in a low-income population in an orthopedic training hospital]. / Tasa de mortalidad después de una fractura de cadera en población con bajos ingresos económicos, en un hospital de entrenamiento ortopédico.

INTRODUCTION: Hip fracture are an important cause of morbidity and mortality in old patients. The one-year mortality after a hip fracture increase between 14 to 47%. The main objective was to analyze the risk factors associated with mortality after a hip fracture in a low-income population. MATERIAL AND METHODS: Retrospective study of patients with traumatic hip fracture in a four-year period in an orthopedic training hospital. The data collected was age, gender, Charlson comorbidity index (CCI), delay time in days for surgery, duration in hours for surgical procedure, transfusion. Two groups were analyzed, alive patients and deceased patients. RESULTS: A total of 96 patients with traumatic hip fracture was analyzed. Mortality rate in the first year was pf 16.6%, and at the end of the follow-up was 32.2%. The alive patients showed better values of CCI with a value of 4.2 ± 1.1 versus 5.2 ± 1.0 in the deceased patients. When compared delay time for surgery and duration of surgical procedure did not observe significant difference between patients alive and deceased. CONCLUSION: The delay time of surgery did not affect the mortality after a traumatic hip fracture in old patients with economic low-income.

INTRODUCCIÓN: Las fracturas de cadera representan una causa importante de morbimortalidad en los adultos mayores. La mortalidad a un año posterior a una fractura de cadera incrementa entre 14 y 47%. El objetivo de este estudio fue analizar los factores de riesgo que impactan la tasa de mortalidad posterior a una fractura de cadera en una población de bajos recursos. MATERIAL Y MÉTODOS: Se analizaron de manera retrospectiva pacientes con fractura de cadera traumática en un período de cuatro años en un hospital universitario con entrenamiento ortopédico. Los datos recolectados incluyeron edad, género, índice de comorbilidad de Charlson (CCI), tiempo en días para la cirugía y duración del procedimiento quirúrgico, así como necesidad de transfusión. Se analizaron dos grupos, pacientes vivos y pacientes fallecidos. RESULTADOS: Se evaluó un total de 96 adultos mayores con fractura de cadera. La tasa de mortalidad durante el primer año fue de 16.6%, mientras que al final del seguimiento fue de 32.2%. El grupo de sobrevivientes presentó una mejor evaluación de acuerdo con el CCI con valor de 4.2 ± 1.1 versus 5.2 ± 1.0 en los pacientes fallecidos. No se encontró diferencia estadísticamente significativa en la mortalidad entre ambos grupos al comparar los días de espera de tiempo quirúrgico y la duración de la cirugía. CONCLUSIÓN: El retraso de la cirugía no afecta la tasa de mortalidad después de una fractura de cadera en pacientes de edad avanzada con bajo ingreso económico.

Chemical composition of industrially and laboratory processed Cyperus esculentus rhizomes.

We report here the results of the study of the chemical composition of Cyperus esculentus rhizomes. Ethanolic extracts have been separated by column chromatography and analyzed by magnetic resonance spectroscopy and mass spectrometry. Quercetin, stigmasterol, and linoleic and oleic acid glycerol esters, together with 4-chlorobutyl oleate, oleamide, myricetin, tyramine and N-feruloyltyramine, found for the first time in Cyperus esculentus rhizomes, have been isolated and quantified in the extracts. Alkaloids have not been detected, and the presence of flavonoids and sterols is moderate.

Transport Properties of Li-TFSI Water-in-Salt Electrolytes.

Water-in-salts are a new family of electrolytes that may allow the development of aqueous Li-ion batteries. They have a structure that is reminiscent of ionic liquids, and they are characterized by a high concentration of ionic species. In this work, we study their transport properties and how they evolve with concentration by using molecular dynamic simulations. We first focus on the choice of the force field. By comparing the simulated viscosities and self-diffusion coefficients with experimental measurements, we select a set of parameters that reproduces well the transport properties. We then use the selected force field to study in detail the variations of the self and collective diffusivities of all the species as well as the transport number of the lithium ion. We show that correlations between ions and water play an important role over the whole concentration range. In the water-in-salt regime, the anions form a percolating network that reduces the cation-anion correlations and leads to rather large values for the transport number compared to other standard electrolytes.

High molar ratios of tumor necrosis factor α (TNF α) soluble receptors I and II to the TNF ligand in human plasma from male veterans with comorbid posttraumatic stress disorder (PTSD) and mild traumatic brain injury (mTBI)

Background and Objectives Posttraumatic stress disorder (PTSD) and traumatic brain injury (TBI) are associated with chronic inflammation, as inferred from increased, but variable, peripheral levels of cytokines. We sought proof of concept for the notion that peripheral cytokine binding proteins and/or soluble receptors can confound measures of cytokines in those with a history of physical and psychological traumatic exposures. Efforts were focused on one of the major cytokines involved in inflammation, tumor necrosis factor-α (TNF- α). Methods We examined blood plasma concentrations of TNF-α, its soluble receptors (TNF-soluble receptors (sR) I and TNFsRII), and C-reactive protein (CRP-1) in a cohort of US Veterans. In a previous study, CRP-1 was shown to be reduced by probiotic anti-inflammatory treatment in this patient cohort. All participants (n = 22) were diagnosed with PTSD and had a history of mild TBI with persistent post-concussive symptoms. Exclusion criteria included medications directly targeting inflammation. Results Molar concentrations of soluble TNFsRI and II exceeded concentrations of the TNF-α ligand. TNFsRI, but not TNFsRII, was significantly associated with CRP-1 (Spearman Rho correlations = 0.518; p=.016 and 0.365; p = .104, respectively). Conclusions TNF soluble receptors may bind to and sequester free TNF-α, suggesting that only measuring ligand concentrations may not provide a fully comprehensive view of inflammation, and potentially lead to inaccurate conclusions. TNFsRI concentration may provide a better estimate of inflammation than TNF-α for those with PTSD and post-acute mTBI with post-concussive symptoms, a hypothesis that invites further testing in larger studies. (AU)

Genomic and transcriptional linkage of the genes for calmodulin, EF-hand 5 protein, and ubiquitin extension protein 52 in Trypanosoma brucei.

We report genomic linkage of a pair of tandem, identical ubiquitin-extension protein 52 (EP52) genes, a novel EF-hand superfamily member gene (EFH5), and the calmodulin gene cluster in Trypanosoma brucei. The intergenic regions of these four genes are short: about 108 bp between the calmodulin gene C and the EFH5 gene, about 111 bp between the EFH5 gene and the ubiquitin-EP52/1 gene, and about 116 bp between the ubiquitin-EP52/1 and -EP52/2 genes. RNA molecules that span these three intergenic regions have been detected by polymerase chain reaction, which suggests that the genes are transcribed in a polycistronic manner. Transcription of the calmodulin, EFH5, and ubiquitin-EP52 genes in isolated nuclei is rapidly inactivated by UV irradiation, which further strengthens the hypothesis that this cluster of three different genes is transcribed in a polycistronic manner and suggests that they are under the control of a single distant upstream promoter. These results suggest that polycistronic transcription is common in trypanosomes and will probably be found for most, if not all, protein-encoding genes. The presence of at least three housekeeping genes with different known or potential regulatory functions within a polycistronic unit suggests that regulation of transcription initiation plays an important role in the coordinated expression of housekeeping genes in trypanosomes.

Decreased food anticipatory activity of obese mice relates to hypothalamic c-Fos expression.

During daily Food Restriction (FR), obese Neotomodon alstoni mice present decreased Food Anticipatory Activity (FAA) compared to lean mice. Here, we investigated whether FOS expression in hypothalamic nuclei involved in food synchronization and anticipation parallels decreased FAA during daily FR of obese N. alstoni. Locomotor activity of lean and obese mice in ad libitum feeding conditions was monitored for at least two weeks. Then, a gradual restriction of food access was followed to establish a 5h period of daily food access. FR was maintained during at least two weeks before sacrifice of mice at the starting point of the feeding period. Obese mice subjected to FR displayed an overall reduction of FOS-positive (FOS+) hypothalamic neurons, while lean mice in a similar protocol exhibited an increase in FOS+ neurons within the arcuate and dorsomedial hypothalamic nuclei. These results are consistent with decreased FAA displayed by obese mice in comparison to lean mice. Furthermore, limbic system areas of lean mice, such as the cingulate cortex and the hippocampus, showed an increase in FOS during FR, while no responses were observed in obese mice. The daily food intake of obese mice was severely reduced during FR, compared to the ad libitum condition, whereas food intake in lean mice was not affected by FR. Current data suggests that decreased hypothalamic and limbic neuronal activation may contribute to the reduction of FAA in obese N. alstoni mice.

Prolactin mediates neuroprotection against excitotoxicity in primary cell cultures of hippocampal neurons via its receptor.

Recently it has been reported that prolactin (PRL) exerts a neuroprotective effect against excitotoxicity in hippocampus in the rat in vivo models. However, the exact mechanism by which PRL mediates this effect is not completely understood. The aim of our study was to assess whether prolactin exerts neuroprotection against excitotoxicity in an in vitro model using primary cell cultures of hippocampal neurons, and to determine whether this effect is mediated via the prolactin receptor (PRLR). Primary cell cultures of rat hippocampal neurons were used in all experiments, gene expression was evaluated by RT-qPCR, and protein expression was assessed by Western blot analysis and immunocytochemistry. Cell viability was assessed by using the MTT method. The results demonstrated that PRL treatment of neurons from primary cultures did not modify cell viability, but that it exerted a neuroprotective effect, with cells treated with PRL showing a significant increase of viability after glutamate (Glu)--induced excitotoxicity as compared with neurons treated with Glu alone. Cultured neurons expressed mRNA for both PRL and its receptor (PRLR), and both PRL and PRLR expression levels changed after the excitotoxic insult. Interestingly, the PRLR protein was detected as two main isoforms of 100 and 40 kDa as compared with that expressed in hypothalamic cells, which was present only as a 30 kDa variant. On the other hand, PRL was not detected in neuron cultures, either by western blot or by immunohistochemistry. Neuroprotection induced by PRL was significantly blocked by specific oligonucleotides against PRLR, thus suggesting that the PRL role is mediated by its receptor expressed in these neurons. The overall results indicated that PRL induces neuroprotection in neurons from primary cell cultures.

Tasa de mortalidad después de una fractura de cadera en población con bajos ingresos económicos, en un hospital de entrenamiento ortopédico / Mortality rate after a hip fracture in a low-income population in an orthopedic training hospital

Resumen: Introducción: Las fracturas de cadera representan una causa importante de morbimortalidad en los adultos mayores. La mortalidad a un año posterior a una fractura de cadera incrementa entre 14 y 47%. El objetivo de este estudio fue analizar los factores de riesgo que impactan la tasa de mortalidad posterior a una fractura de cadera en una población de bajos recursos. Material y métodos: Se analizaron de manera retrospectiva pacientes con fractura de cadera traumática en un período de cuatro años en un hospital universitario con entrenamiento ortopédico. Los datos recolectados incluyeron edad, género, índice de comorbilidad de Charlson (CCI), tiempo en días para la cirugía y duración del procedimiento quirúrgico, así como necesidad de transfusión. Se analizaron dos grupos, pacientes vivos y pacientes fallecidos. Resultados: Se evaluó un total de 96 adultos mayores con fractura de cadera. La tasa de mortalidad durante el primer año fue de 16.6%, mientras que al final del seguimiento fue de 32.2%. El grupo de sobrevivientes presentó una mejor evaluación de acuerdo con el CCI con valor de 4.2 ± 1.1 versus 5.2 ± 1.0 en los pacientes fallecidos. No se encontró diferencia estadísticamente significativa en la mortalidad entre ambos grupos al comparar los días de espera de tiempo quirúrgico y la duración de la cirugía. Conclusión: El retraso de la cirugía no afecta la tasa de mortalidad después de una fractura de cadera en pacientes de edad avanzada con bajo ingreso económico.

Abstract: Introduction: Hip fracture are an important cause of morbidity and mortality in old patients. The one-year mortality after a hip fracture increase between 14 to 47%. The main objective was to analyze the risk factors associated with mortality after a hip fracture in a low-income population. Material and methods: Retrospective study of patients with traumatic hip fracture in a four-year period in an orthopedic training hospital. The data collected was age, gender, Charlson comorbidity index (CCI), delay time in days for surgery, duration in hours for surgical procedure, transfusion. Two groups were analyzed, alive patients and deceased patients. Results: A total of 96 patients with traumatic hip fracture was analyzed. Mortality rate in the first year was pf 16.6%, and at the end of the follow-up was 32.2%. The alive patients showed better values of CCI with a value of 4.2 ± 1.1 versus 5.2 ± 1.0 in the deceased patients. When compared delay time for surgery and duration of surgical procedure did not observe significant difference between patients alive and deceased. Conclusion: The delay time of surgery did not affect the mortality after a traumatic hip fracture in old patients with economic low-income.

Molecular dynamics simulation of the behaviour of water in nano-confined ionic liquid-water mixtures.

This work describes the behaviour of water molecules in 1-butyl-3-methylimidazolium tetrafluoroborate ionic liquid under nanoconfinement, between graphene sheets. By means of molecular dynamics simulations, the adsorption of water molecules at the graphene surface is studied. A depletion of water molecules in the vicinity of the neutral and negatively charged graphene surfaces, and their adsorption at the positively charged surface are observed in line with the preferential hydration of the ionic liquid anions. The findings are appropriately described using a two-level statistical model. The confinement effect on the structure and dynamics of the mixtures is thoroughly analyzed using the density and the potential of mean force profiles, as well as by the vibrational densities of the states of water molecules near the graphene surface. The orientation of water molecules and the water-induced structural transitions in the layer closest to the graphene surface are also discussed.

The properties of the neutral proteinase released by primary chondrocyte cultures and its action on proteoglycan aggregate.

The enzymatic mechanism of proteoglycan breakdown is of major interest, since it has been proposed that osteoarthritis involves increased proteolytic breakdown of proteoglycans. This paper describes the properties of the proteoglycan-degrading enzymes released into the extracellular milieu by chondrocyte cultures that produce cartilage-specific type II collagen but no detectable type I collagen. Attention has been focused on enzymes active at neutral pH, since the pH of the extracellular matrix is around neutrality. Biogel P-60 chromatography of concentrated culture medium showed a major peak of enzyme activity on proteoglycan monomer entrapped in polyacrylamide beads as well as on native proteoglycan aggregates. The enzyme yields a specific limit digestion peptide from the aggregate of approximately 55,000 daltons (in the presence of SDS). This limit peptide is probably derived from the hyaluronic acid-binding region of proteoglycan. The proteolytic enzyme is latent but can be activated by aminophenylmercuric acetate or trypsin. The molecular weight of both the active and latent forms, determined by gel filtration, is approximately 33,000. The activity is not inhibited by phenylmethylsulfonyl fluoride or pepstatin but is completely inhibited by o-phenanthroline; the activity is restored by Zn or Co ions in the presence of calcium chloride. Removal of calcium by dialysis results in a reversible loss of activity. The release of such a metalloproteinase by chondrocytes into the extracellular milieu, its activity at physiological pH and its ability to degrade native proteoglycans are consistent with a role of the enzyme in proteoglycan metabolism.

Collagen, collagenase and collagenolytic activity in rat Graafian follicles during follicular growth and ovulation.

Follicles were dissected from the ovaries of immature rats at intervals after subcutaneous injection of 20 IU of pregnant mare's serum gonadotropin. A surge of luteinizing hormone was observed at 54 h and ovulation occurred at 64-66 h. The follicular volume between 36 and 48 h, then doubled again shortly before ovulation. The collagen content of the follicles increased 3-fold from 35 to 56 h, but decreased significantly (25%) from 61 to 66 h. Follicle homogenates, activated with trypsin or aminophenylmercuric acetate, digested Type I collagen at 28 degrees C to produce typical of a true collagenase. Collagenolytic activity assayed against endogenous collagen at 37 degrees C did not change significantly between 38 and 66 h.

Characterization of the metalloproteinase inhibitor produced by bovine articular chondrocyte cultures.

Primary cultures of bovine articular chondrocytes release a latent metalloproteinase which is activated by incubation with organomercurials to degrade proteoglycans. All the enzyme present in the culture medium is latent and binds to columns of heparin-Sepharose. The yield of activity from the heparin-Sepharose columns (measured after organomercurial treatment) is approximately 300-1000% depending on the chondrocyte culture batch. Recombination of column fractions shows that the increase in activity is due to the separation of an inhibitor of the metalloproteinase by the chromatographic step. The metalloproteinase inhibitor has a molecular weight of approximately 35000 (determined by Bio-Gel P-60 chromatography) and binds reversibly to columns of concavalin A-Sepharose. It is relatively heat stable (30 min at 60 degrees C) and resistant to inactivation by trypsin (2 h, 37 degrees C, 10 microgram/ml trypsin). The inhibitor is active against rat uterine collagenase and gelatinase but does not affect bacterial metalloproteinases such as thermolysin and Clostridium histolyticum collagenase.

The electrical and mechanical activity of the esophageal cell of Ascaris lumbricoides.

The esophagus of Ascaris is a syncytial muscle organ of tubular shape in which the myofibrils are arranged radially between the lumen and the external surface. A resting potential of almost 40 mv (cytoplasm negative) is maintained by the extracellular organic anions (volatile fatty acids) found in the perienteric fluid. Replacement of these anions by Cl- ions results in a large depolarization. The resting potential is also decreased when the external pH is lowered. The leading phase of the action potential with a positive overshoot of about 18 mv elicits contraction of the myofibrils, development of negative pressure within the lumen, and suction of liquid and food particles. The mechanical energy stored in the elastic components of the cell is released when the myofibrils relax, thus injecting the contents of the lumen into the intestine. A fast and synchronous relaxation is elicited by a regenerative membrane polarization, a negative spike with a peak value of up to 108 mv produced by an increase in the permeability of the membrane to K+ ions. Cells completely depolarized in "chloride" saline are still able to generate such large potassium spikes.

Extracellular action potentials recorded from the interior of the giant esophageal cell of Ascaris.

Exploration of the cytoplasm of the giant esophageal cell of Ascaris with a recording microelectrode shows the existence of shallow spaces where the microelectrode tip becomes extracellular in spite of being in the interior of the cell. When the microelectrode penetrates into these spaces from the cytoplasm, the resting potential shifts to a different level or entirely disappears. At the same time the large intracellular spikes are replaced by small transients similar to extracellularly recorded action potentials. It is concluded that such spaces are in communication with the external solution, and separated from the cytoplasm by an electrically active membrane; i.e., able to generate action potentials. Measurement of the potential differences between the interior of the spaces and the external solution shows that although some are not polarized, many spaces have a resting potential of the same polarity as that of the cytoplasm. It is suggested that although they are of larger size these spaces may be equivalent to the tubular systems which in other muscle cells are known to be involved in the spread of excitation into the cytoplasm.