Flow of a plasma of multielectron elements along a magnetic field

An analysis is made of a flow of Ar plasma imitating plasma flows in ion separation systems such as systems for processing spent nuclear fuel or ion cyclotron resonance isotope separation systems. It is found that the electron temperature is equalized along the flow by electron heat conduction. When the electron temperature is not too low (T _e ≥ E _ion/10, where E _ion is the ionization energy), multicharged ions are intensely produced along the entire flow. It is shown that this process is accompanied by the flow acceleration. Difficulties in describing a supersonic flow by hydrodynamic equations are pointed out.     

Age-related changes and circadian variations in peripheral levels of thyroid hormones in Murrah buffaloes

The aim of this study was to investigate the variations in plasma triiodothyronine (T₃) and thyroxine (T₄) with the advancement of age and to determine their circadian patterns in prepubertal and pubertal Murrah buffaloes. The variations in plasma T₃ and T₄ with the advancement of age were observed from day 1 to 24 months of age. Significant higher levels of T₃ and T₄ were observed after birth and a gradual decrease in their concentrations occurred until 15 days of age. The mean plasma T₃ and T₄ ranged between 1.26–3.79 and 60.7–166 ng/ml, respectively, during 1–30 days of age. During 1–24 months of age, the variations in plasma T₃ did not differ (p > 0.05) with the advancement of age, whereas significant (p < 0.0001) changes were observed in plasma T₄. The circadian patterns of T₃ and T₄ were evaluated in prepubertal Murrah buffaloes (n = 8) aged between 14 and 16 months. The mean plasma T₃ and T₄ ranged between 1.04–1.85 and 43.0–76.1 ng/ml, respectively. Significant (p > 0.0001) changes in the secretory pattern of T₃ were observed, whereas the secretory pattern of T₄ did not differ significantly (p > 0.05). In addition, the circadian patterns of T₃ and T₄ in pubertal buffaloes (n = 4) aged between 28 and 30 months were observed and compared to that of prepubertal group (n = 4). The prepubertal group showed significant (p < 0.001) higher plasma T₃ concentrations over 24 h than the pubertal group.     

Effects of ovine prolactin on iodide metabolism and thyroid activity in the eel

Summary In the eel, ovine prolactin (oPrl) treatment (0.018 IU/day·g body weight), for 8 to 13 days modifies neither iodide absorption from the water nor excretion, extrathyroidal metabolism and plasma level of iodide.Thyroid activity, evaluated by epithelial cell height, radioiodine uptake and absolute iodide uptake is approximately twice that of controls. However, the amounts of total iodine, thyroxine (T₄) and triiodothyronine (T₃) in thyroid are unaltered by oPrl. Therefore, the decrease of plasma T₄ and the increase of plasma T₃, previously observed in oPrl-treated eels, do not result from a preferential thyroidal secretion of T₃, but only from a stimulation of peripheral conversion of T₄ to T₃. Furthermore, the increased thyroid activity probably originates from a decreased feedback inhibition following the fall of circulating T₄ induced by oPrl.Abbreviations oPrl ovine prolactin - T ₄ Thyroxine - T ₃ 3.5.3 triiodothyronine - TRH thyrotropin releasing hormone - TSH thyroid stimulating hormone - PBI protein bound iodine     

Orcadian Variation in Human Stature

Thyroxine (T₄) and triiodothyronine (T₃) plasma concentrations have been determined during 24-hr sampling periods in six mongrels (age 12-36 months), six beagles (age 35-37 months), three labradors (age 3.5 months) and three beagles (age 5 months). The mean T₄ levels of the labradors were significantly lower than the values found for mongrels or older beagles (P < 0.05), whereas T₃ was higher in the 5 month old beagles compared to the mongrels (P < 0.001), young beagles (P < 0.05) or labradors (P < 0.01).

Circadian and ultradian rhythmicities have been evaluated by cosinor and Fourier analysis. Mongrels and older beagles did have a 12-hr rhythmicity in plasma T₄ (P < 0.05), whereas 5 month old beagles had a circadian one (P < 0.01). A 12-hr rhythmicity was also found for T₃ in the older Beagles (P < 0.05). However, Fourier analysis indicated that the daily variation in T₄ and T₃ plasma levels was inadequately mathematically described by single sinusoidal rhythm and that more harmonic components are to be taken into account.

The obtained data during a 24-hr period indicate that T₄ and T₃ concentrations in plasma may vary according to breed, age and sampling hour.     

Effect of ambient temperature and E. coli endotoxin upon the plasma iron level in wild house mice in winter season

Summary The effects of ambient temperatures of 10°C and 30°C and of E. coli endotoxin on brain temperature and plasma iron level were investigated in unrestrained wild house mice, Mus musculus. In control animals (i.p. saline-injected) exposed to cold environmenta the brain temperature decreased and plasma iron levels were lower than those observed under thermoneutral conditions (30°C). Animals injected i.p. with endotoxin (0.5 g·kg^-1) and placed at 30°C showed a drop in plasma iron level during the fever episode. The results provide strong evidence for a relationship between brain temperature and plasma iron level in control mice under thermoneutral conditions, and show that during cold exposure or after injection of endotoxin, there is no linear correlation between brain temperature and plasma iron. Moreover, it was found that cold stress influences plasma iron level and that this influence is not mediated by changes in brain temperature.Abbreviations EP endotoxin pyrogen - T _A ambient temperature - T _Br brain temperature - T _Br change in T _Br in relation to its initial value in feverish or control mice - T _Br difference between T _Br in feverish and control mice     

Effect of ovine TSH, thiourea, ovine prolactin and bovine growth hormone on plasma thyroxine and tri-iodothyronine levels in rainbow trout,Salmo gairdneri

Summary A single injection of ovine TSH (1.1 g or 2.2 g/g body weight) effected a significant (P<0.01) increase in plasma T₄ levels in rainbow trout within 9 h and 1 h respectively. In fish given the higher dose the T₄ levels were still significantly higher (P<0.01) than in the controls 24 h after the injection. Ovine TSH had no significant effect on plasma T₃ levels. Plasma T₃/T₄ ratios in fish given the higher TSH dose were significantly lower than the controls at 3 h (P<0.01), 6 h (P=0.01), 9 h and 24 h (P<0.05) while in fish given the lower dose they were significantly lower than in controls at 3 h (P<0.01), 6 h (P=0.01) and 9 h (P<0.05).T₄ levels in TSH-injected fish were significantly higher (P<0.05) than in controls after 3 and 11 injections but were not significantly different after 16 injections. Plasma T₃ and T₃/T₄ ratios did not differ significantly in fish given multiple injections of either TSH or saline.Plasma T₄ levels in fish treated with thiourea were significantly lower (Pº0.01) than in comparable controls after 6, 9 and 15 days and plasma T₃ levels were lower (P<0.05) after 15 days treatment. T₃/T₄ ratios did not differ significantly at any time period.A single injection of bovine STH (10 g/g body weight) effect a significant rise in plasma T₄ levels 9 h (P=0.05) and 24 h (P<0.01) after the injection while ovine prolactin in a similar dose was without effect. Plasma T₃ levels in saline injected fish showed a steady decline over the 24 h following the injection whereas levels in prolactin and STH injected animals tended to rise. T₃ levels in the saline-injected fish were significantly higher (P<0.01) than in prolactin and STH injected animals 1 h after the injection but were significantly lower (P<0.01) than in the hormone-treated fish 24 h after the injection. There were no significant differences in T₃/T₄ ratios in any of the groups. Multiple injections of STH effected a significant increase (P<0.05) in plasma T₄ compared with the controls; prolactin had no significant effect. There was no significant differences in plasma T₃ concentration or T₃/T₄ ratios in any of the groups.     

Non-planckian equilibrium radiation of plasma-like media

Consideration of equilibrium radiation of plasma-like media shows that the spectral distribution of such radiation differs from that of Planckian equilibrium radiation (blackbody radiation). The physical reason for this difference consists in the impossibility of propagation of photons with the dispersion law ω = ck in systems of charged particles. The thermodynamics of equilibrium electromagnetic radiation in plasma is also considered. It is shown that the difference of the thermodynamic properties of such radiation from those of Planckian radiation is characterized by the parameter a = ℏΩ _p /T. This difference is especially pronounced in plasma media in which a ≥ 1. Applications of the results obtained to plasmas of metals (first of all, liquid metals in which charged particles have no distant order) and to the plasma model of the early Universe are discussed.     

Measurement and regulation of thyroidal status in teleost fish

Summary We have reviewed the stages in teleost thyroid function and its regulation, from the initial biosynthesis of the TH to their eventual interaction with putative receptors.TH biosynthesis depends on an adequate plasma iodide level, determined partly by dietary iodide and partly by active branchial iodide uptake from the water, Pulse-injected radioiodide can be used to evaluate thyroidal iodide uptake, aspects of TH biosynthesis and TH thyroidal secretion. However, owing to variable plasma iodide levels, care is required in interpretating these parameters. TH biosynthesis, thyroglobulin properties and intrathyroidal secretion mechanisms have received limited recent attention. Histological indices of thyroid tissue changes, while useful in many situations, do not always correlate with more direct estimates of thyroidal secretion and can be misleading.Thyroid function is regulated by the hypothalamo-pituitary-thyroid axis, but neither the identities of the hypothalamic factors nor a reliable immunoassay for TSH have been established. Currently, activity of the hypothalamic-pituitary axis is usually determined by pituitary thyrotrope histological appearance or bioassay of pituitary TSH. Plasma free T₄ feeds back at both the pituitary and hypothalamic levels and inhibits TSH release. Thyroidal T₄ secretory activity is presumably adjusted to maintain a constant plasma T₄level according to physiologic state.Plasma T₄ is probably the most commonly used index of thyroidal status. However, (1) T₄ is probably not the active form of TH, (2) the T₄ plasma level may be influenced by the binding properties of plasma proteins, and (3) the T₄ concentration alone makes no provision for the rate of T₄ turnover in plasma. The most practical way to measure thyroidal T₄SR is to determine plasma T₄DR, and assuming steady-state conditions, equate it to T₄SR. The T₄DR is determined from kinetic studies employing^*T₄, which also enable estimates of sizes of vascular and extravascular T₄ pools and their rates of exchange. Excretion of T₄ or its derivatives in urine or bile can be determined also. A high proportion of T₄ is enzymatically monodeiodinated in liver and other tissues, generating T₃ for local (intracellular) and vascular systemic compartments.Bothin vivo andin vitro methods have been used to quantify T₄ deiodinase activity, which is highly responsive to physiologic state and environmental variables. T₃ production is inhibited by a moderate T₃ excess indicating an autoregulatory system, whereby tissue T₃ levels are maintained at a set-point appropriate for a particular physiologic state. The rate of T₃ production provides an informative measure of thyroidal status in a given tissue. However, other pathways also contribute to the maintenance of T₃ homeostasis at a particular set-point. These include the rate of T₃ degradation to 3,3-T₂, the rate of T₄ substrate diversion to rT₃ (an inactive isomer) and by the excretion of parent compounds or conjugates in bile and urine. Potential losses across branchial or integumentary surfaces have yet to be evaluated.The most fundamental measure of thyroidal status is represented by the amount of T₃ saturably bound to receptors/nucleus for the cell type of interest. This is estimated most accurately in double isotope studies in which T₃ contributions from both vascular and intracellular compartments are evaluated. Less satisfactory but meaningful indices of T₃ availability to receptor sites may be obtained from the plasma T₃ (or free T₃) level and from the tissue T₃ level. The former is appropriate if the cell type in question obtains its T₃ primarily from plasma; the latter should be measured if the cell type derives its T₃ mainly through intracellular deiodinase activity. If the proportion of vascular T₃/intracellular T₃ bound to receptors is known, it may indicate the degree of receptor activation. However, even cytosolic T₃ levels may not vary in proportion to nuclear T₃ levels.Differences in thyroidal function between teleosts and homeotherms can be attributed to distinctive strategies in iodide economy and to fundamental differences in control of thyroidal status. Owing to more certain iodide availability (branchial iodide pump and plasma iodide-binding proteins), teleosts are probably more liberal in their iodide use and have less efficient mechanisms for recovery and retention of hormonal iodide than homeotherms. Also, primary control of teleost thyroidal function appears peripheral. It is the finely regulated conversion of T₄ to T₃ in tissues which may largely determine the T₄ secretion rate. Thus, T₄, as a prohormone, may be produced more to satisfy the substrate needs for T₄ conversion rather than to drive T₃ production. Because TH are mainly implicated in tissue- or cell-specific processes involved in development, growth and reproduction in teleosts, it may be advantageous for their thyroidal status to be determined locally through T₄-to-T₃ deiodination. In homeotherms, primary control is mainly central through the hypothalamic-pituitary axis, which regulates thyroidal secretion of T₄ and significant amounts of T₃. The level of T₄ (free T₄) is believed to drive the production of T₃ in most peripheral tissues. Because TH are extensively involved in the systemically integrated adjustment of basal metabolic rate in homeotherms, it may have been advantageous to evolve a system leaning towards central control by the hypothalamus, the brain centre associated with thermoregulation.     

Ion temperature profiles along a hydrogen diagnostic beam in a TORE SUPRA tokamak plasma

The active particle diagnostic technique is used to study the ion temperature at five spatial points along the path of a hydrogen diagnostic beam. The temperature of the main ion plasma component (deuterium ions) measured by this diagnostic technique along the beam path is compared with the temperature of carbon ions (C⁺⁵). A study is made of the following characteristic features of the behavior of the ion temperature profiles T_i in various TORE SUPRA operating modes: the formation of flat and even hollow T_i profiles in ohmic discharges with q ～3 at the plasma edge, the change in T_i profiles in ergodic divertor discharges, and the difference between the temperature of the bulk ions measured by the active particle diagnostic technique and the temperature of C⁺⁵ ions in the plasma region r/a>0.5. The features revealed are explained at a qualitative level.     

Enhanced Li‐Ion Accessibility in MXene Titanium Carbide by Steric Chloride Termination

Pseudocapacitance is a key charge storage mechanism to advanced electrochemical energy storage devices distinguished by the simultaneous achievement of high capacitance and a high charge/discharge rate by using surface redox chemistries. MXene, a family of layered compounds, is a pseudocapacitor‐like electrode material which exhibits charge storage through exceptionally fast ion accessibility to redox sites. Here, the authors demonstrate steric chloride termination in MXene Ti₂CT_x (T_x : surface termination groups) to open the interlayer space between the individual 2D Ti₂CT_x units. The open interlayer space significantly enhances Li‐ion accessibility, leading to high gravimetric and volumetric capacitances (300 F g^?1 and 130 F cm^?3) with less diffusion limitation. A Li‐ion hybrid capacitor consisting of the Ti₂CT_x negative electrode and the LiNi_1/3Co_1/3Mn_1/3O₂ positive electrode displays an unprecedented specific energy density of 160 W h kg^?1 at 220 W kg^?1 based on the total weight of positive and negative active materials.     

Study of Electromagnetic Electron Cyclotron Waves for Kappa Distribution with AC Field in the Magnetosphere of Saturn

Parallel propagating electromagnetic electron cyclotron (EMEC) waves in the extended plasma sheet (~12R_S) and in the outer magnetosphere (~18R_S) of Saturn have been studied. A dispersion relation for parallel propagating relativistic EMEC waves has been applied to the magnetosphere of Saturn, and comparisons have been made with the data of Voyager 1 at these radial distances. The detailed investigations for EMEC waves have been done in the presence of the perpendicular AC electric field, using the kappa distribution function. The relativistic temporal growth rate is calculated by the method of characteristic solution with the data provided by Voyager 1. The effect of the suprathermal electron density, temperature anisotropy, frequency of AC electric field, thermal energy of ions, and relativistic factor on the temporal growth rate of EMEC wave emission has been studied. The simulation results show that the growth of parallel propagating EMEC waves is significantly affected by variations in the temperature anisotropy, electron density, ion thermal energy, and relativistic factor in both the extended plasma sheet and the outer magnetosphere of Saturn. The temperature anisotropy (T⊥/T_║), ion thermal energy (K_BT_║i), and electron density (n₀) have been found to be a major source of free energy for parallel propagating EMEC waves in both regions.     

Enhanced Rate Capability of Ion‐Accessible Ti3C2Tx‐NbN Hybrid Electrodes

Although 2D Ti₃C₂T_x is a good candidate for supercapacitors, the restacking of nanosheets hinders the ion transport significantly at high scan rates, especially under practical mass loading (>10 mg cm^?2) and thickness (tens of microns). Here, Ti₃C₂T_x‐NbN hybrid film is designed by self‐assembling Ti₃C₂T_x with 2D arrays of NbN nanocrystals. Working as an interlayer spacer of Ti₃C₂T_x, NbN facilitates the ion penetration through its 2D porous structure; even at extremely high scan rates. The hybrid film shows a thickness‐independent rate performance (almost the same rate capabilities from 2 to 20 000 mV s^?1) for 3 and 50 µm thick electrodes. Even a 109 µm thick Ti₃C₂T_x‐NbN electrode shows a better rate performance than 25 µm thick pure Ti₃C₂T_x electrodes. This method may pave a way to controlling ion transport in electrodes composed of 2D conductive materials, which have potential applications in high‐rate energy storage and beyond.     

Determination of the plasma parameters in the PF-3 facility by the methods of X-ray spectroscopy

NeIX and NeX spectra emitted by the PF-3 high-current (2 MA) plasma focus facility are measured. A numerical model describing the spectral intensities of the emission of helium- and hydrogen-like neon ions from an optically thick plasma is proposed. The electron temperature T _e and electron density n _e in the plasma of the PF-3 facility are determined by comparing the calculated and measured emission spectra of neon.     

Determination of DNA base compositions from melting profiles in dilute buffers

Equations were determined for the dependency of the melting temperature (T_m) of DNA upon the logarithm of the sodium ion concentration, for four DNA samples of widely different base compositions (θ_GC). The slopes of these T_m versus log M equations wore found to decrease with increasing θ_{G C}of the samples. An empirical equation relating T_m, log M (Na⁺) and θ_{G C} was derived, which also accounts for differences in T_m versus log M slopes. Data from the literature for some synthetic polynucleotides and for the crab(Cancer pagarus) satellite poly AT are discussed in relation to the above finding. The changes in T_m versus log M slopes with θ_{G C} are interpreted in terms of changes in the thermodynamic parameters ΔS and ΔH with base composition.     

Age-related and seasonal variations in plasma uncarboxylated osteocalcin in male Murrah buffaloes

The present study aims to investigate the age-related and seasonal variations in plasma uncarboxylated osteocalcin (UcOCN) in male Murrah buffaloes. In experiment 1, body weight, body dimensions and plasma UcOCN levels were estimated in 120 male Murrah buffaloes aged between 18 days and 8 years. We observed a significant (p < 0.0001) decrease in plasma UcOCN with age and their levels ranged between 0.25 and 9.25 ng/ml. In experiment 2, the plasma UcOCN, cortisol, triiodothyronine (T₃), thyroxine (T₄) and prolactin levels were determined during spring and summer in 6–34 months (n = 24) old male Murrah buffaloes. Significant (p < 0.0001) higher plasma UcOCN levels were observed in spring than in summer. The plasma T₃ and T₄ levels were positively correlated with plasma UcOCN, whereas the plasma cortisol and prolactin were negatively correlated. Further, to observe the effect of season on temporal variations of UcOCN, Murrah buffaloes aged between 4–6 (n = 5), 14–16 (n = 5) and 28–30 (n = 5) months were bled at an interval of 30 min, between 0700 and 01030 h, during both the seasons. We observed significant effects of season (p < 0.0001), age (p < 0.0001) and season-by-age interaction (p < 0.01) on plasma UcOCN. The reasons for variations in plasma UcOCN with age and season will be discussed.     

MsSAMS,a cold stress-responsive gene,provides resistance to environmental stress in T2-generation transgenic plants

The SAMS (S-adenosylmethionine synthetase) gene is known to play an important role in the mechanism of cold resistance, as overexpression of this gene results in phenotypic changes in T₁-generation transgenic plants. Accordingly, this study was conducted to test the expression of the MsSAMS gene in T₂-generation transgenic plants and to investigate the resistance of these plants and the function of the transgene in response to various environmental stresses. For the morphological analysis of T₂-generation transgenic plants overexpressing the MsSAMS gene, observations using scanning electron microscopy (SEM) were performed. T₂-generation transgenic plants were obtained by planting a total of 5 lines, and their characteristics were tested by comparisons with those of the control. SEM revealed that the thickest leaves were produced by the T6 transgenic line—161.24?±?8.05 µm. The number of stomata ranged from 20.00?±?2.65 to 34.00?±?1.00 in the T₂-generation transgenic plants, but the control had more stomata. Resistance to various factors, such as low temperature, drought, and oxidative stress, in the T₂-generation transgenic plants was also confirmed. Under cold-stress conditions, the T6 transgenic line presented the lowest value (22.73%) of ion leakage, and under drought-stress conditions, compared with the control, the transgenic lines presented lower ion leakage after being treated with various concentrations of mannitol. Even under oxidative-stress conditions, the T₂-generation transgenic plants presented ion leakage levels that were 32.91?±?4.24 to 48.33?±?3.54% lower than those of the control after treatment with various concentrations of methyl viologen. Regarding SAMS enzyme activity, as the duration of cold treatment increased, the activity in the transgenic plants tended to decrease and then increase. During 48 h of cold treatment, the control showed a decrease in SAM content, while the T₂-generation transgenic plants presented an increase in SAM content, from 13.58?±?1.04 to 22.75?±?1.95 mg protein/g FW. The results suggest that the MsSAMS gene may be important to the mechanisms of resistance to oxidative and drought stresses in addition to its previously known association with cold resistance. Based on these results, it was suggested that the MsSAMS gene, whose expression is induced by cold stress, can serve as a marker of various responses to environmental stresses, because resistance to cold damage and various environmental stresses are stably inherited in the T₂ generation.

     

Thyroid hormones regulate lipid metabolism in a teleost Anabas testudineus (Bloch)

We compared the long-term action of 3,5,3′-triiodo-l-thyronine (T₃) and 3,5-diiodo-l-thyronine (T₂) on lipid metabolism in a teleost Anabas testudineus. Among the six groups of animals used in this experiment, except for the control group, all received 6-propylthiouracil (6-PTU) to create a hypothyroid state in order to analyse the action of iodothyronines on lipid metabolism. Injections of 6-PTU reduced T₃ concentration in the circulation by 79.6% and injections of iodothyronines enhanced the level of T₃ in the plasma, and a maximum increase was observed in T₃ (500 ng)-treated specimens. Analysis of lipogenic enzymes in liver and heart showed that a tissue-specific variation exists in the action of thyroid hormones and, in many cases, activity is higher in T₂-treated groups. Analysis of various lipid classes showed that long-term administration of T₂ is also effective in producing a comparable effect with that of T₃ on lipid metabolism.     

High dietary sodium chloride and body temperature in the domestic fowl and the Glaucous-winged gull

Arad and Skadhauge (1986) correlated plasma sodium to calcium ratio and body temperature in domestic fowl (Gallus domesticus) during increased dietary sodium chloride intake which increased plasma sodium concentration. During acclimation to high dietary NaCl, body temperature should increase in proportion to the increase in plasma sodium concentration, and body temperature should increase less in gulls than in chickens because salt gland secretion of NaCl by gulls should prevent elevation of plasma sodium concentration. Plasma osmolality, plasma sodium concentration, plasma concentrations of total calcium and ionized calcium, and body temperature and panting threshold were measured in domestic roosters and Glaucous-winged gulls before and after exposure to high NaCl diets. Gull body temperature (40.4±0.2 °C) increased significantly (PM0.05) during salt acclimation. Rooster body temperature (41.0±0.2 °C) did not increase significantly. Plasma sodium concentration increased in gulls (5.4±0.5%, P<0.01) and was correlated with body temperature (r=0.497, P<0.05); the 3.8±1.0% increase in plasma sodium concentration in roosters (P<0.01) was not, suggesting that change in body temperature might be a response to the magnitude of increase in plasma sodium concentration. Plasma ionized calcium concentration increased by 12.9±4.6% (P<0.01) in gulls and by 5.3±1.0% (P<0.01) in roosters. Plasma sodium concentration was correlated with calcium ion concentration in both gulls (r=0.635, P<0.05) and roosters (r=0.664, P<0.05). In neither species were ratios of sodium to total calcium plasma concentration or sodium to ionized calcium concentration altered or related to body temperature. Panting threshold increased significantly in roosters following salt acclimation, but not in gulls due to high variability in response. The increase in gull plasma sodium concentration was small compared to previously reported (Saxena 1976; Denbow and Edens 1980, 1981; Maki et al. 1988) increases in hypothalamic and intraventricular sodium concentration following infusion of Na⁺, yet the effect on body temperature was similar in both types of studies. This suggests that sodium may have peripheral effects that augment the central effects imposed by altered hypothalamic interstitial sodium and calcium concentration.Abbreviations [Ca]_p1 total calcium concentration in plasma - [Ca²⁺] ionized calcium concentration in plasma - [Cl]_p1 chloride concentration in plasma - f respiratory frequency - Hct hematocrit - [K]_p1 potassium concentration in plasma - [Na]_p1 sodium concentration in plasma - osm_p1 plasma osmolality - PT panting threshold - T _a ambient temperature - T _b body temperature - V _t tidal volume     

Integrin participates in the effect of thyroxine on plasma membrane in immature rat testis

Background

The secretory activity of Sertoli cells (SC) is dependent on ion channel functions and protein synthesis and is critical to ongoing spermatogenesis. The aim of this study was to investigate the mechanism of action associated with a non-metabolizable amino acid [¹⁴C]-MeAIB (α-(methyl-amino)isobutyric acid) accumulation stimulated by T₄ and the role of the integrin receptor in this event, and also to clarify whether the T₄ effect on MeAIB accumulation and on Ca²⁺ influx culminates in cell secretion.

Methods

We have studied the rapid and plasma membrane initiated effects of T₄ by using ⁴⁵Ca²⁺ uptake and [⁴⁵C]-MeAIB accumulation assays, respectively. Thymidine incorporation into DNA was used to monitor nuclear activity and quinacrine to analyze the secretory activity on SC.

Results

The stimulation of MeAIB accumulation by T₄ appears to be mediated by the integrin receptor in the plasma membrane since tetrac and RGD peptide were able to nullify the effect of this hormone. In addition, T₄ increases extracellular Ca²⁺ uptake and Ca²⁺ from intracellular stocks to enhance nuclear activity, but this genomic action seems not to influence SC secretion mediated by T₄. Also, the cytoskeleton and ClC-3 chloride channel contribute to the membrane-associated responses of SC.

Conclusions

T₄ integrin receptor activation ultimately determines the plasma membrane responses on amino acid transport in SC, but it is not involved in calcium influx, cell secretion or the nuclear effect of the hormone.

General significance

The integrin receptor activation by T₄ may take a role in plasma membrane processes involved in the male reproductive system.