Fall In Tension Research Articles

Reduction of cortical pulling at mitotic entry facilitates aster centration.

Equal cell division relies upon astral microtubule-based centering mechanisms, yet how the interplay between mitotic entry, cortical force generation and long astral microtubules leads to symmetric cell division is not resolved. We report that a cortically located sperm aster displaying long astral microtubules that penetrate the whole zygote does not undergo centration until mitotic entry. At mitotic entry, we find that microtubule-based cortical pulling is lost. Quantitative measurements of cortical pulling and cytoplasmic pulling together with physical simulations suggested that a wavelike loss of cortical pulling at mitotic entry leads to aster centration based on cytoplasmic pulling. Cortical actin is lost from the cortex at mitotic entry coincident with a fall in cortical tension from ∼300pN/µm to ∼100pN/µm. Following the loss of cortical force generators at mitotic entry, long microtubule-based cytoplasmic pulling is sufficient to displace the aster towards the cell center. These data reveal how mitotic aster centration is coordinated with mitotic entry in chordate zygotes.

Modeling Seasonality of Emotional Tension in Social Media

Social media has become an almost unlimited resource for studying social processes. Seasonality is a phenomenon that significantly affects many physical and mental states. Modeling collective emotional seasonal changes is a challenging task for the technical, social, and humanities sciences. This is due to the laboriousness and complexity of obtaining a sufficient amount of data, processing and evaluating them, and presenting the results. At the same time, understanding the annual dynamics of collective sentiment provides us with important insights into collective behavior, especially in various crises or disasters. In our study, we propose a scheme for identifying and evaluating signs of the seasonal rise and fall of emotional tension based on social media texts. The analysis is based on Russian-language comments in VKontakte social network communities devoted to city news and the events of a small town in the Nizhny Novgorod region, Russia. Workflow steps include a statistical method for categorizing data, exploratory analysis to identify common patterns, data aggregation for modeling seasonal changes, the identification of typical data properties through clustering, and the formulation and validation of seasonality criteria. As a result of seasonality modeling, it is shown that the calendar seasonal model corresponds to the data, and the dynamics of emotional tension correlate with the seasons. The proposed methodology is useful for a wide range of social practice issues, such as monitoring public opinion or assessing irregular shifts in mass emotions.

Experiencing Rhythm in Dance.

In this article, two dance educators offer a definition of rhythm from both educational and performance perspectives and discuss pedagogical practices that waken students’ awareness to rhythm as a lived-experience over which they have creative control. For the dancer, in the midst of the dance, rhythms are, in the words of Margaret H’Doubler, recurring patterns of measured energy. These patterns are nested in scales from the moment-to-moment shifts in muscular contraction and release to the rise and fall of dramatic tension in a performed dance. This approach to rhythm runs counter to many dance students’ studio-based training in which rhythm is equated to synchronizing accents to a specific meter. The authors describe pedagogical practices in the studio that foster engagement with rhythm as lived-experience. Drawing attention to their kinesthetic experience while moving, students are encouraged to modulate levels of exertion embedded in the qualities of movement they are experiencing. As varying levels of exertion are attended to across temporal durations, students notice patterns as they emerge and recur. This attention to recurring patterns of measured exertion is, the authors claim, the lived-experience of rhythm in dance.

Chronic Red Bull Consumption during Adolescence: Effect on Mesocortical and Mesolimbic Dopamine Transmission and Cardiovascular System in Adult Rats

Energy drinks are very popular nonalcoholic beverages among adolescents and young adults for their stimulant effects. Our study aimed to investigate the effect of repeated intraoral Red Bull (RB) infusion on dopamine transmission in the nucleus accumbens shell and core and in the medial prefrontal cortex and on cardiac contractility in adult rats exposed to chronic RB consumption. Rats were subjected to 4 weeks of RB voluntary consumption from adolescence to adulthood. Monitoring of in vivo dopamine was carried out by brain microdialysis. In vitro cardiac contractility was studied on biomechanical properties of isolated left-ventricular papillary muscle. The main finding of the study was that, in treated animals, RB increased shell dopamine via a nonadaptive mechanism, a pattern similar to that of drugs of abuse. No changes in isometric and isotonic mechanical parameters were associated with chronic RB consumption. However, a prolonged time to peak tension and half-time of relaxation and a slower peak rate of tension fall were observed in RB-treated rats. It is likely that RB treatment affects left-ventricular papillary muscle contraction. The neurochemical results here obtained can explain the addictive properties of RB, while the cardiovascular investigation findings suggest a hidden papillary contractility impairment.

Changes in membrane elasticity caused by the hydrophobic surfactant proteins correlate poorly with adsorption of lipid vesicles.

To establish how the hydrophobic surfactant proteins, SP-B and SP-C, promote adsorption of lipids to an air/water interface, we used X-ray diffuse scattering (XDS) to determine an order parameter of the lipid chains (Sxray) and the bending modulus of the lipid bilayers (KC). Samples contained different amounts of the proteins with two sets of lipids. Dioleoylphosphatidylcholine (DOPC) provided a simple, well characterized model system. The nonpolar and phospholipids (N&PL) from extracted calf surfactant provided the biological mix of lipids. For both systems, the proteins produced changes in Sxray that correlated well with KC. The dose-response to the proteins, however, differed. Small amounts of protein generated large decreases in Sxray and KC for DOPC that progressed monotonically. The changes for the surfactant lipids were erratic. Our studies then tested whether the proteins produced correlated effects on adsorption. Experiments measured the initial fall in surface tension during adsorption to a constant surface area, and then expansion of the interface during adsorption at a constant surface tension of 40 mN m-1. The proteins produced a sigmoidal increase in the rate of adsorption at 40 mN m-1 for both lipids. The results correlated poorly with the changes in Sxray and KC in both cases. Disordering of the lipid chains produced by the proteins, and the softening of the bilayers, fail to explain how the proteins promote adsorption of lipid vesicles.

SCLEROTHERAPY OR SCLERODISTRESS? ARDS CAUSED BY SCLEROSING AGENTS USED FOR ROUTINE ARTERO-VENOUS MALFORMATION (AVM) EMBOLIZATION

SESSION TITLE: Medical Student/Resident Critical Care Posters SESSION TYPE: Med Student/Res Case Rep Postr PRESENTED ON: October 18-21, 2020 INTRODUCTION: AVM embolization is a routine outpatient procedure believed to have minimal risks. While local complications have been described, including bleeding, nerve injury, and skin necrosis, it is important that we keep in mind that major, sometimes catastrophic complications could arise. Here we present a case of ARDS that developed in a patient undergoing routine outpatient embolization of an upper extremity AVM. CASE PRESENTATION: A 50-year-old male presented to the outpatient suite for an elective angiography and embolization of his left forearm AV malformation that was symptomatic. His past medical history was significant for HIV (Last CD4 of 278 on Triumeq), ESRD previously on hemodialysis now status post a renal transplant, hypertension. A successful embolization was carried out with ethanol, sodium tetradecyl sulfate, and coils, following which the patient was transferred to the PACU. Approximately one-hour post-procedure, he was noted to have increased work of breathing requiring to be placed on BiPAP with a chest X-ray done at the time revealing bilateral interstitial infiltrates. Given further deterioration within the next hour, the patient was intubated and transferred to the ICU, with an initial PaO2: FiO2 ratio of <100. Given this severity, he was started on lung-protective strategy, paralyzed, placed prone, and given inhaled epoprostenol. He remained intubated for a total of nine days and discharged fourteen days after his procedure. Of note, his course was complicated by methicillin-resistant staphylococcus aureus (MRSA) which grew in his bronchial brush done 24 hours post-intubation, for which he was treated with Linezolid. His renal function significantly deteriorated requiring several sessions of hemodialysis while hospitalized. DISCUSSION: This case report attempts to identify ARDS caused in the setting of sclerosing agents. Although this patient did grow MRSA in his bronchial brush, he was documented to be completely symptom-free, afebrile, and without a white count on arrival for the procedure. Moreover, the temporal association between the embolization and respiratory collapse points us to the main inciting factor in his case. Ethanol and sodium tetradecyl sulfate are among the most commonly used sclerosing agents for AVM and esophageal varices. The risk is the escape of these agents into the systemic circulation. A study done injecting these agents intravenously in sheep showed an immediate severe fall in respiratory compliance and arterial oxygen tension, with the proposed mechanism of action being increased microvascular permeability causing alveolar damage and destruction of the blood-gas barrier of the lung.1 CONCLUSIONS: Further studies are needed to determine the extent and prevalence of major complications involved with routinely used sclerosing agents, risk factors contributing to these if any, so as to enable patients and providers to make an informed decision. Reference #1: Vallgren S, Sigurdsson GH, Moberger G, Christenson JT. Influence of intravenous injection of sclerosing agents on the respiratory function. Acta Chir Scand. 1988;154(4):271-276. DISCLOSURES: No relevant relationships by Jojo Alunilkummannil, source=Web Response No relevant relationships by Shireen George, source=Web Response No relevant relationships by Tariq Sallam, source=Web Response

The Location and Rate of the Phosphate Release Step in the Muscle Cross-Bridge Cycle

It is controversial whether the phosphate (Pi) release step in the cross-bridge cycle occurs before or after the first tension-generating step and whether it is fast or slow. We have therefore modified our previous model of the frog cross-bridge cycle by including a Pi release step either before (model A) or after (model B) the first tension-generating step and refined the two models by downhill simplex runs against experimental data for the force-velocity relation and the tension transients after length steps. Pi release step was initially made slow (70 s−1), but after refinement, it became fast (∼500 s−1 for model A and ∼6000 s−1 for model B). The two models gave similar fits to the experimental tension transients after length steps, but model A gave a better fit to the lengthening limb of the force-velocity relation than model B. 50 mM Pi inhibited the isometric tension of model A by ∼50% but that of model B by only ∼25%. The half-inhibition was at 6.0 mM Pi for model A and at 1.6 mM Pi for model B. The values for model A were consistent with experimental data. We also simulated the effect Pi jump as in caged Pi experiments. For model A, a Pi jump induced a tension fall at a rate similar to the experimental phase II. There was then a small rise in tension to the steady state mimicking the experimental phase III. The initial tension fall was caused by detachment of M⋅ADP⋅Pi myosin heads from actin and reversal of the first tension-generating step. For model B, the fall in tension was more rapid and due to reversal of the first tension-generating step, and phase III was not observed. We conclude that, as in model A, the Pi release step is before the first tension-generating step and is moderately fast.

Density and Surface Tension of Lead–Sodium Melts

Polytherms of the density and surface tension of lead alloys with small additions of sodium in the heating mode from temperatures of melting of Pb–Na alloys up to 650°C in an atmosphere of pure He of grade A (99.995%) are studied using the large sessile drop approach. It is found that the density and surface tension fall as the temperature rises, and raising the content of sodium in the studied alloys to 4 wt % leads to a a substantial drop in surface tension.

Novel Aqueous Two-Phase System Consisting of 1,4-Bis(2-hydroxypropyl)-piperazine, Na2SO4, and H2O: Temperature-Dependent Equilibrium Data and Physical Properties

In this work, we have developed a novel aqueous two-phase system (ATPS) composed of 1,4-bis(2-hydroxypropyl)-piperazine (HPP), Na2SO4, and H2O, which can determine the liquid–liquid equilibrium and phase diagrams at the temperatures of 303.15–323.15 K. Simultaneously, the physical properties such as density, viscosity, refractive index, and surface tension have been determined for the top phases and bottom ones of the ATPS. The results indicate that temperature has no significant effect upon the biphasic region, implying a small enthalpy contribution during phase separation. However, the changes in temperature result in a decrease of tie line slope, because H2O molecules are transferred from the bottom phase to the top phase. In determining the physical properties of the system, viscosity and refraction index increase with the system components increasing, during the phase of both HPP and Na2SO4, while density and surface tension fall with the increase of system components in the top phase and decrease in...

Intraabdominal Surgery and Anesthesia Management.

The purpose of this study was to determine if the pattern of ventilation, by itself, influences oxygenation during anesthesia and surgery and examine the hypothesis that progressive pulmonary atelectasis may occur during constant ventilation whenever periodic hyperventilation is lacking, but is reversible by passive hyperinflation of the lungs. Eighteen surgical patients, ranging in age from 24 to 87 yr, without known pulmonary disease, were studied during intraabdominal procedures and one radical mastectomy. Although ventilation remained constant, changes occurred in arterial oxygen tension and in total pulmonary compliance, with an average fall of 22% in oxygen tension and 15% in total pulmonary compliance. This fall in oxygen tension supports the hypothesis that progressive mechanical atelectasis may lead to increased venous admixture to arterial blood. The influence of the ventilator pattern on atelectasis and shunting is further illustrated by the reversibility of the fall in oxygen tension that follows hyperinflation. A relation between the degree of ventilation and the magnitude of fall in arterial oxygen tension was found, where large tidal volumes appear to protect against falls in oxygen tension, while shallow tidal volumes lead to atelectasis and increased shunting with impaired oxygenation.

Reinterpretation of the Tension Response of Muscle to Stretches and Releases

We have reexamined the experimental time courses of tension in frog muscle after rapid length steps. The early tension recoveries are biexponential. After 3 nm/hs stretches and releases, the rates of the immediate rapid tension changes are similar but the subsequent tension fall after a stretch is much slower than the rise after a release. After 1.5 nm/hs length steps, the entire tension responses are more nearly mirror images. To identify the underlying processes, we used a model of the muscle cross-bridge cycle with two tension-generating (tensing) steps. Analysis of the time course of the tension, the rates of the steps in the cycle, and their contributions to tension provided insights into previously puzzling features of the experimental response. After a stretch, the initial rapid tension fall in the model is caused principally by the reversal of the first tensing step, but after a few milliseconds the tensing step resumes its forward direction. We conclude that the remaining response should not be included in phase 2, the period of early tension recovery. With this exclusion, T2, the tension at the end of this period, rises with an increase of stretch. The rate of early tension recovery also increases with stretch size, showing that the reversal of the first tensing step is strain sensitive. After small length steps, the fast and slow components of the early tension recovery are both caused mainly by the first tensing step. The fast component is triggered by the initial sliding of the filaments, and the slow component is due to further sliding that occurs as the tension recovers. With small length steps (<0.5 nm/hs), the time course of the response to a stretch is the reverse of that to a release.

The influence of oxygen tension on the local regulation of blood flow by shear stress

Introduction and purpose. Vascular response to mechanical stimuli, namely transmural pressure (Bayliss effect) and wall shear stress (response to blood flow), play an important role in regulation of vascular tone. The purpose of the work was to study an influence of hypoxia on the vessel radius and blood flow control by response to shear stress. Methodology/approach. Mathematical simulation was used. The model is based on published data of experiments on small cerebral arteries of rats. The main assumptions of the model are: 1) the vessel is a thin wall cylinder; 2) the radius is controlled by two parameters: concentration of free calcium ions in the cytoplasm of the smooth muscle cells and concentration of nitric oxide (NO) in the smooth muscle layer; 3) the rate of NO production by endothelium is proportional to modulus of shear stress on the vessel wall. The apparent blood viscosity is calculated using the solution of the problem of two-layer flow. The numerical experiments were performed in Turbo Pascal. The main results and discussion. The dependence of vessel tone regulation by response to altered shear stress on oxygen tension is caused by dependence of NO synthesis in endothelium and NO consumption on oxygen concentration. As it follows from mathematical simulation, hypoxia reduces the role of mechanogenic regulation, and the increase of the wall sensitivity to NO makes this effect more appreciable. Calculations performed for typical value of cerebral vessel response to shear stress, show that the fall in oxygen tension from 100 to 30 per cent leads to decrease in diameter by 6 %, in blood flow rate by 11 %. The rheological factors prevent flow rate diminution, but their contribution is very small: less than 3 %. The fall in oxygen tension reduces NO production rate by endothelial cells and NO concentration in the vessel wall. At strong hypoxia (reduction in oxygen tension from 100 to 30 % and less) NO concentration in smooth muscle layer drops by more than 15 %. Conclusions. Hypoxia decreases NO-dependent vessel response to altered shear rate. This effect increases with the value of vessel response to shear stress. The rheological factors impede the decrease of this response.

Research on Web Press Tension Control System

Tension control of press is a key and difficult point of the whole machine control. The stand or fall of tension is directly related to the quality of the products. According to the characteristics of the web press tension control, this paper expounds the main factors influencing tension and the purpose of tension control, researches on the tension control principle of web tape, analyzes control rule and control circuit of tension control system, illustrates the advantages of PID control law adopted in the tension control system, and concludes the influencing factors of paper tape tension control system and the corresponding problems needed to solve in the control.

Duke Ellington as Pianist: A Study of Styles by Matthew J. Cooper, and: Why Jazz Happened by Marc Myers (review)

as Pianist: A Study of Styles. By Matthew J. Cooper. (Monographs and Bibliographies in American Music, no. 24.) Missoula, MT: College Music Society, 2013. [xvi, 127p. ISBN 9781881913610 (paperback), $45.] Music examples, appendices, bibliography, index. Why Jazz Happened. By Marc Myers. Berkeley: University of California Press, 2013. [x, 267 p. ISBN 9780520268784 (hardcover); ISBN 9780520953987 (e-book), $34.95.] Bibliographic references, index. (1899-1974) is known to many Americans as the leader of a swing-era dance band as well as a writer of pop tunes. Some musicians and jazz fans also know him as a major composer--arranger. In fact, there are musicologists and journalists who consider to be America's greatest composer, which puts him in a league with Charles Ives and Aaron Copland. Though many jazz fans think of as a pianist too, few scholars have examined how unique and original his approach to the keyboard really was. Dr. Matthew J. Cooper of Eastern Oregon University wrote that Ellington surely stands as one of the great jazz pianists, and his work is worthy of greater recognition than it has been accorded in the past (p. 102). Responding to this need, he wrote as Pianist. A Study of Styles. It is a very welcome contribution because it not only touts the importance of the pianist, but it also explicates the unique techniques that made him original. This book may prove to be essential study for jazz pianists and jazz theory teachers, not just fans. Cooper is wonderfully conversant with a wide variety of commentaries that prove pivotal to our understanding of Ellington's piano styles. service that the author provides by doing this is commendable, particularly because he shares useful excerpts from writings that may be unknown to scholars and fans. For instance, observations by pianist Dick Katz, pianist-historian Mark Tucker, and composer-historian Gunther Schuller are particularly informative. Quotes from written remarks by himself are penetrating. Cooper is such a tenacious researcher that he even tracked down several strands of counter-evidence for an arcane discussion about whether ever made a piano roll. To help us understand the meat of Ellington's piano style, the author has undertaken the huge task of transcribing and analyzing solos from sources that range all the way from 1928 to 1972. For instance, he selected the obscure 1929 recording Lazy Duke to extract the pianist's work in accompanying a clarinet solo; used parallel triads in f cross rhythm. To refute the contention of some critics that not particularly good as a pianist, Cooper provides transcriptions of the 1932 recording Lots o' Fingers (at 288 beats per minute). Then, for chapter 5: The Later Years and the Atypical Style, Cooper takes quite seriously the odd matching of with avant-garde bassist Charles Mingus and bebop drummer Max Roach that led to the puzzling music on their Money Jungle album of 1962. (Coincidentally, the contemporary drummer-bandleader Terri Lyne Carrington is now using some of this strange music for her group's repertory.) Though we have long known that admired the work of James P. Johnson, the father of stride piano, we may not have known many specifics. We learn from Cooper that Part of Johnson's influence on the younger his exciting use of rhythmic displacement. Johnson never confined himself to a monotonous pattern of 'oom-pah' bass notes and chords; instead, he found graceful and imaginative ways to vary the left-hand accompaniment. In doing so, he created a range of surprising accents and regulated the rise and fall of tension masterfully within each of his phrases (p. 24). Among the historically-significant contributions that made as a pianist, the author alerts us to the fact that was among the first pianists to embrace the technique now known as 'comping. …

Guideline on the management of acute chest syndrome in sickle cell disease.

1. Department of Haematology, Guy’s and St Thomas’ NHS Foundation Trust 2. Lane Fox Respiratory Unit, St Thomas’ Hospital, Guy’s and St Thomas’ NHS Foundation Trust 3. Department of Haematology, North Middlesex Hospital 4. Department of Paediatric Haematology, Bristol Royal Hospital for Children 5. Department of Haematological Medicine, King’s College Hospital 6. Department of Haematology, Whittington Hospital

Fish in hot water: Hypoxaemia does not trigger catecholamine mobilization during heat shock in rainbow trout (Oncorhynchus mykiss)

Rainbow trout (Oncorhynchus mykiss) exposed to an acute heat shock (1h at 25°C after raising water temperature from 13°C to 25°C over 4h) mount a significant catecholamine response. The present study investigated the proximate mechanisms underlying catecholamine mobilization. Trout exposed to heat shock in vivo exhibited a significant reduction in arterial O2 tension, but arterial O2 concentration was not affected by heat shock, nor was catecholamine release during heat shock prevented by prior and concomitant exposure to hyperoxia (to prevent the fall in arterial O2 tension). Thus, catecholamine mobilization probably was not triggered by impaired blood O2 transport. Heat-shocked trout also exhibited an elevation of arterial CO2 tension coupled with a fall in arterial pH, but these factors are not expected to trigger catecholamine release. The changes in blood O2 and CO2 tension occurred despite a significant hyperventilatory response to heat shock. Future studies should investigate whether catecholamine mobilization during heat shock in rainbow trout is triggered by a specific effect of high temperature activating the sympathetic nervous system via a thermosensitive transient receptor potential channel.

Bladder tissue oxygen tension monitoring in pigs subjected to a range of cardiorespiratory and pharmacological challenges

A fall in tissue oxygen tension (tPO(2)) is an early indicator of organ hypoxia in both patients and animal models. We previously demonstrated the utility of bladder tPO(2) in various rodent shock models. As a prelude to clinical testing, we aimed to provide further validation of bladder tPO(2) monitoring in a large animal model undergoing a range of cardiorespiratory insults and vasoactive drug interventions. Anaesthetized, mechanically ventilated, instrumented female pigs (n = 8) were subjected to a range of short-term cardiorespiratory (changes in inspired oxygen concentration (FiO(2)), haemorrhage, positive end-expiratory pressure) and pharmacologic (inotrope, pressor) challenges. Global haemodynamics, arterial and pulmonary blood gases and bladder tPO(2) were measured before and after each challenge. Bladder tPO(2) values fell in line with increasing degrees of hypoxaemia and haemorrhage, and were restored during resuscitation. These changes often preceded those seen in global haemodynamics, arterial base excess and lactate. The rise in bladder tPO(2) with hyperoxia, performed as an oxygen challenge test, was incrementally blunted by progressive haemorrhage. Dobutamine and norepinephrine both increased cardiac output and global O(2) delivery, but had no effect on bladder tPO(2) or lactataemia in these healthy pigs. In this pig model bladder tPO(2) provides a sensitive indicator of organ hypoxia compared to traditional biochemical markers during various cardiorespiratory challenges. This technique offers a potentially useful tool for clinical monitoring.

The Keystone Flap: Not an Advance, Just a Stretch

The keystone flap is being promoted as an advance in oncological surgical reconstruction. Wound closure with this island flap involves two V-Y advancements toward the center and along the long axis of the island, at right angles to the line of maximum tension when the wound is closed. It is implied that the long-axis advancements enable closure by relaxing the entire flap of skin, allowing it to be stretched more easily along the short axis. We undertook a study to test this hypothesis. We measured tension and extension along perpendicular axes in nine freshly excised specimens of human skin. We held the longitudinal axis fixed while stretching the skin along the transverse axis. We then released the longitudinal axis and measured the resultant drop in transverse tension. Finally, we increased the transverse tension to approximately its previous level, and measured the new transverse extension. There was significant interdependence between longitudinal and transverse tensions. The fall in transverse wound tension associated with longitudinal release varied with starting tensions and with the original site and orientation of the specimen. In the five cases where the longitudinal release was from the in vivo length, the mean increase in transverse stretch attributable to the release was 0.6 mm (95% confidence interval 0.1-1.1 mm). The increase in transverse stretch that can be achieved by releasing skin from its longitudinal in vivo length appears trivial, raising questions about the rationale for the use of the prototypical (type 1) keystone flap in wound closure.

Sex Steroid Hormone Effects in Normal and Pathologic Conditions in Lung Physiology

Progesterone and estradiol participate in the regulation of many pulmonary functions, for example progesterone mediates the fall of alveolar carbon dioxide tension observed in the luteal phase of the menstrual cycle and during pregnancy in humans, when progesterone levels are high. The treatment with estradiol diminishes vasoconstriction and hypoxia. Progesterone and estradiol in addition to participating in non-pathological functions such as vasodilation and lung maturation, also have influence on pathologies as asthma, cystic diseases and cancer. Therefore this review will provide an overview of the action and effects of these hormones in lung, their mechanism of action through their intracellular receptors and their influence over asthma, cystic lung diseases and cancer.

Fall in oxygen tension of culture medium stimulates the adenosinergic signalling of a human T cell line

We examined the short-course expression of various parameters involved in the adenosinergic signalling of a human T cell line during in vitro decrease of the medium culture oxygen tension mimicking in vivo hypoxia. Fall of 92 mmHg in oxygen tension of culture medium induced in CEM, a CD4+ human T cell line, a continuous production of hypoxia-inducing factor-1α with a plateau value at 9 h, a rapid increase in adenosine production peaking at 3 h and a decrease in adenosine deaminase peaking at 6 h. The adenosine A(2A) receptor (A(2A)R) protein level of CEM cells was enhanced with a peak at 6 h. Intracellular 3',5'-cyclic adenosine monophosphate accumulated in CEM cells with a maximal level at 9 h. These results show that a human-cultured T cells line can upregulate its own adenosine production and A(2A)R expression during exposure to acute hypoxia. Hypoxia-increased stimulation of the adenosinergic signalling of T cells may have immunosuppressive properties and, consequently, A(2A)R agonists may have therapeutic relevance.