Direct Chemical Action Research Articles

Molecular mechanisms of seed dormancy release by gas plasma-activated water technology.

Developing innovative agri-technologies is essential for the sustainable intensification of global food production. Seed dormancy is an adaptive trait which defines the environmental conditions in which the seed is able to germinate. Dormancy release requires sensing and integration of multiple environmental signals, a complex process which may be mimicked by seed treatment technologies. Here, we reveal molecular mechanisms by which non-thermal (cold) atmospheric gas plasma-activated water (GPAW) releases the physiological seed dormancy of Arabidopsis thaliana. GPAW triggered dormancy release by synergistic interaction between plasma-generated reactive chemical species (NO3–, H2O2, ·NO, and ·OH) and multiple signalling pathways targeting gibberellin and abscisic acid (ABA) metabolism and the expression of downstream cell wall-remodelling genes. Direct chemical action of GPAW on cell walls resulted in premature biomechanical endosperm weakening. The germination responses of dormancy signalling (nlp8, prt6, and dog1) and ABA metabolism (cyp707a2) mutants varied with GPAW composition. GPAW removes seed dormancy blocks by triggering multiple molecular signalling pathways combined with direct chemical tissue weakening to permit seed germination. Gas plasma technologies therefore improve seed quality by mimicking permissive environments in which sensing and integration of multiple signals lead to dormancy release and germination.

Carbon Capture Powered by Solar Energy

The urgent implementation of emissions control measures is inhibited in part by the expense of carbon capture technology. A large part of the cost of amine based approaches is in the heat regeneration of the absorbent. An alternative way to do this could be through use of abundant solar energy. In a new approach, direct chemical action on the absorbed CO2 was achieved by use of a reversible photoacid. Irradiation of the CO2 loaded solution resulted in CO2 removal by action of light.

The Effect Of Gonadectomy And Estradiol On Sensitivity To Oxidative Stress

The sexual dimorphism of life span and caloric restriction effects in numerous species suggest that estradiol (E2) is protective against oxidative damage. The only direct test of E2’s protective effect in mice against in vivo oxidative stress to date may have been confounded by E2’s direct chemical action as an antioxidant because it was administered at very high dosages. Therefore, we have identified a low yet physiologically effective dose of E2. We then administered this dose using subcutaneous time-release pellets to ovariectomized mice. Two weeks after E2 pellet implantation, sham-operated, ovariectomized, and ovariectomized E2-supplemented female mice were injected with a lethal dose of paraquat and their survival was followed. It was observed that ovariectomy exacerbates paraquat-induced mortality and is rescued by E2 supplementation. An equivalent experiment was performed on sham-operated, orchidectomized, and E2-supplemented orchidectomized male mice. The survival of male mice was improved by orchidectomy, and E2 gave no further benefit. We interpret the results to mean that E2 is protective against oxidative stress through its regulatory role and that testosterone diminishes protection against oxidative stress.

Potassium-proton symport in Neurospora: kinetic control by pH and membrane potential.

Active transport of potassium in K+-starved Neurospora was previously shown to resemble closely potassium uptake in yeast, Chlorella, and higher plants, for which K+ pumps or K+/H+-ATPases had been proposed. For Neurospora, however, potassium-proton cotransport was demonstrated to operate, with a coupling ratio of 1 H+ to 1 K+ taken inward so that K+, but not H+, moves against its electrochemical gradient (Rodriguez-Navarro et al., J. Gen. Physiol. 87:649-674). In the present experiments, the current-voltage (I-V) characteristic of K+-H+ cotransport in spherical cells of Neurospora has been studied with a voltage-clamp technique, using difference-current methods to dissect it from other ion-transport processes in the Neurospora plasma membrane. Addition of 5-200 microM K+ to the bathing medium causes 10-150 mV depolarization of the unclamped membrane, and yields a sigmoid I-V curve with a steep slope (maximal conductance of 10-30 microS/cm2) for voltages of -300 to -100 mV, i.e., in the normal physiologic range. Outside that range the apparent I-V curve of the K+-H+ symport saturates for both hyperpolarization and depolarization. It fails to cross the voltage axis at its predicted reversal potential, however, an effect which can be attributed to failure of the I-V difference method under reversing conditions. In the absence of voltage clamping, inhibitors-such as cyanide or vanadate-which block the primary proton pump in Neurospora also promptly inhibit K+ transport and K+-H+ currents. But when voltage clamping is used to offset the depolarizing effects of pump blockade, the inhibitors have no immediate effect on K+-H+ currents. Thus, the inhibition of K+ transport usually observed with these agents reflects the kinetic effect of membrane depolarization rather than any direct chemical action or the cotransport system itself. Detailed study of the effects of [K+]o and pHo on the I-V curve for K+-H+ symport has revealed that increasing membrane potential systematically decreases the apparent affinity of the transporter for K+, but increases affinity for protons (Km range: for [K+]o, 15-45 microM; for [H+]o, 10-35 nM). This behavior is consistent with two distinct reaction-kinetic models, in which (i) a neutral carrier binds K+ first and H+ last in the forward direction of transport, or (ii) a negatively charged carrier (-2) binds H+ first and K+ last.

Inhibitory effect of toluene on tumor promotion in mouse skin.

In the two-stage mouse model for skin tumorigenesis with phorbol-12-myristate-13-acetate (PMA) as promoter, topical application of 40 microliters of toluene 2X/week at the initiation/promotion site (the back) reduced the average number of tumors/mouse (ANT/M) to approximately one-fourth that of controls. Control procedure involved initiation of C3H mice with benzo[a]pyrene (BaP) and CD-1 mice with 7,12-dimethylbenz[a]anthracene (DMBA) followed by promotion with from 1 to 5 micrograms PMA in 40 microliters acetone 2X/week. Forty microliters of toluene 2X/week per se was a weak promoter (6-13% of control ANT/M), and produced mild skin irritation at the application site but behavior and body weights were normal. The toluene inhibition of tumorigenesis was not a direct chemical action on PMA since similar effects occurred whether toluene was the vehicle for PMA or whether it was applied up to 1 day before PMA (i.e., prepromotion). Prepromotion with acetone had no effect on tumorigenesis, substantiating its use as control vehicle and suggesting that the toluene inhibition was a specific tissue reaction. The inhibitory effect appeared to be on PMA promotion rather than on initiation since toluene and acetone produced similar numbers of tumors when used as the vehicle for BaP or DMBA in two-stage or BaP in single-stage trials. The inhibition was not permanent since tumorigenesis returned to control rates 2-3 weeks after prepromotion with toluene ceased but promotion with PMA in acetone continued. Toluene may be unique among reported promotion inhibitors in that it is a widely used commercial chemical which sometimes serves as a vehicle in cancer-screening trials. Since its metabolism is reasonably well defined, it may be of value in exploring further the process of tumor promotion.

The 1985 Upjohn award lecture. Tolerance, learning, and neurochemical adaptation.

Alcohol or drug tolerance has been viewed traditionally as a homeostatic response to a direct chemical action of the agent on the neuron. This concept has undergone major modification as a result of recent observations that behavioral and environmental factors can alter markedly the tolerance developed to the same drug regimen. Obligatory task performance under the influence of the drug, classical conditional stimuli in an environment habitually associated with drug administration, previous exposure to a tolerance-producing regimen, and environmental modification of the expression of the drug's effect can all influence dramatically the degree of tolerance produced by a given dosage. Attempts to identify possible cellular mechanisms of tolerance development are illustrated by a review of studies on the relations between ethanol tolerance and changes in the neuronal membrane Na+ -K+ ATPase and its interaction with ethanol and norepinephrine, hippocampal serotoninergic systems and their interaction with a vasopressin derivative, a membrane-bound calcium- and calmodulin- dependent kinase, and hypothalamic-hypophyseal endorphin-producing systems. None of these studies or other similar ones, whether correlational or interventional in nature, has yet provided full and credible explanations of the effects of behavioral and environmental factors on tolerance development. Finding such explanations is the major current challenge in the neurobiology of tolerance.

Shock lung and diffuse alveolar damage pathological and pathogenetic considerations

Diffuse alveolar damage may be caused by any one or more of a large number of injurious agents. While the etiology may be diverse, the pathology is relatively uniform ranging from an acute exudative phase characterized by protein-rich interstitial and alveolar edema, through to a reactive subacute proliferative phase characterized by interstitial fibroplasia and collagenization together with granular pneumocyte hyperplasia. Interstitial inflammation is a variable feature and of course mixed exudative and proliferative features are common. In the clinically overt adult respiratory distress syndrome, the mortality is formidable. The pathogenesis is damage to endothelial cells and membranous pneumocytes. This may be caused by direct chemical action or indirectly through the mediation of oxidizing free radicles or leukotrienes. In diffuse alveolar damage associated with shock, recent work suggests mediation of the cellular injury via complement activation following tissue injury, with the major pathology being due to lysosomal enzyme damage from phagocytes chemotactically attracted to the lung. Etiological factors in diffuse alveolar damage are numerous and details of appropriate primary therapy are therefore diverse. The pathogenesis and pathology are however relatively uniform, calling for uniform supportive therapeutic measures of the clinical adult respiratory distress syndrome.

The Effect of Anesthetics on the Radiosensitivity of a Murine Tumor

The effect of four anesthetics on the single dose of x rays required to locally control 50% of implanted MT tumors was investigated. Compared with unanesthetized animals, no change in radiosensitivity was observed if mice were irradiated under either tribromoethanol or fentanyl-fluanisone-diazepam anesthesia. However, a small but significant degree of radioprotection was observed under chloral hydrate or pentobarbital anesthesia. Hypothermia or increased hypoxia are considered unlikely mechanisms for the protection, a direct chemical action being most probable. The preferred method for immobilizing the mice in order to locally irradiate the tumors was by simple physical restraint (with care taken to minimize physiological stress). However, if anesthesia was a necessity, the present work suggests that for the MT tumor at least the nonprotecting tribromoethanol and fentanyl-fluanisone-diazepam are preferable to the protecting chloral hydrate and pentobarbital. Tribromoethanol is preferable to fetanyl-fluanisone-diazepam in that it produces a smaller drop in temperature. However, it is only a short-acting anesthetic, and prolongation of the state of anesthesia by repeated doses simply prolongs the temperature decline so that there may be no real benefit over fentanyl-fluanisone-diazepam.

Photosynthesis and respiration in the coralline algae, Clathromorphum circumscriptum and Corallina officinalis and the metabolic basis of calcification

Study of the pH relations of the coralline algae has shown that there is good reason to believe that calcification may be brought about by the development of alkalinity by the cells of the thallus, while a slightly acid reaction may be detected on occasion on the outer surface (Digby, 1977). The mechanism of calcification is obscure, but in general two types of action might be involved, direct chemical action and active transport. In direct chemical action a chain of reactions may occur in which the laws of chemical equivalence must be obeyed. Active transport involves complex metabolic processes which may be much more efficient in moving ions from one place to another, the utilization of one chemical equivalent of oxygen providing the energy to transport more than one equivalent of a particular substance.

Emf's across CdI2 ‐ Cd2 I 2 Electrolytes Using Electrodes of Bare W, Molten Cd, and Molten Au‐Cd: Bare Electrode Effects, Use of n ≠ 2 , Premonitory Phenomena and Liquid Structure in Au‐Cd, and the Cd ‐ CdX2 Phase Diagrams

Emf measurements have been made on cells with mixed‐valence electrolytes (a) to establish structural and thermodynamic properties for molten Au‐Cd alloys and (b) to study the source and behavior of some unexpected voltages associated with bare W electrodes dipping into these electrolytes. Changes with temperature and composition of the partial molal entropies, enthalpies, and free energies of the Cd component in the Au‐Cd melts point out the existence of premonitory changes a few degrees above the liquidus as well as of liquid structural changes far from the liquidus; these changes correlate with earlier studies by vapor pressure and by electrical conductivity in the Au‐Cd system at higher temperatures. is used to evaluate the effective valence for these electrolytes when saturated with Cd; this appears in calculation of . Apparently the mixed‐valence electrolyte, plus probable oxide impurities, reacts with the bare electrode (in this case W) surfaces by direct chemical action to form surface films which protect the metal below against direct chemical attack. These films are in equilibrium with the electrolytes. When, however, electrochemical attack is permitted, as when an emf measurement is made, then the underlying metal becomes subject to attack and another reactant enters the reaction. This effect leads to anomalous voltages in electrodes which are normally considered to be inert in molten salts, e.g., W, Mo, and graphite. If these sources of voltage are recognized, then proper determinations of activities and phase boundaries can be made; some earlier measurements of this type which neglected these voltages, however, must be reevaluated. Application of these proper techniques to the system is made.

The effect of angiotensin on renin production and release in vitro.

SummaryA preparation of a renal cell suspension system suitable for renin studies was utilized to investigate the in vitro effects of angiotensin which has previously been shown to influence renin production in vivo. The addition of angiotensin to the incubated samples caused a significant inhibition of renin production and release. It is suggested that the renin-inhibitory effect of angiotensin in the intact animal might be due, at least in part, to a direct chemical action on the renal cells.

Ovarian pregnancy and the intrauterine device

Nine ovarian pregnancies among women with an intrauterine device (IUD) in situ are reviewed in this report. Five cases were discovered among 45 ectopic pregnancies reported in the Cooperative Statistical Program (CSP) of the Population Council, and four additional cases were obtained in response to a notice published in the American Journal of Obstetrics and Gynecology or by personal contacts. The ratio of one ovarian pregnancy to nine ectopic pregnancies among IUD wearers in the CSP is much higher than in the general population, where it is about 1:200. Estimation of the probable number of fertilized ova among women wearing IUD's suggests that the device reduces uterine implantation by about 99.5 per cent, tubal implantation by 95 per cent, and the incidence of ovarian pregnancy not at all. This finding could be explained by the production in the endometrium of an agent interfering with either fertilization or implantation and suggests direct chemical action, possibly by retrograde flow into the tubes.

In vitro stimulation of renin production by epinephrine, norepinephrine, and cyclic AMP.

SummaryThe preparation of a dog renal cell suspension suitable for the study of renin production is described. This suspension was utilized to study the in vitro effects of agents that have previously been shown to affect renin production in vivo. Since production and destruction of renin could not be separately quantified, data were limited to “net production” of renin. Incubated controls had only slightly higher renin content than did the nonincubated controls, but the addition of epinephrine, norepinephrine or cyclic AMP caused striking increases in “net production” of renin. The effects of these agents on “net renin production” were abolished by cycloheximide, an inhibitor of protein synthesis. It is suggested that the reninstimulating effect of catecholamines in the intact animal might be due, at least in part, to a direct chemical action on the renal cells. Cyclic AMP may play a role as an intracellular mediator of the action of catecholamines.

Effects of cadmium upon the excurrent duct system of the rat testis.

AbstractThis report describes lesions observed in excurrent ducts of the testis in 152 of 518 rats, in the course of studies concerned with cadmium‐induced testis injury and the actions of selenium and zinc, separately and combined, in protecting against such damage. All elements were injected subcutaneously, as soluble salts. Necropsy was usually five days (77% of rats) after cadmium injection, but lesions were observed within six hours.Ductuli efferentes showed variable degrees of sperm blockage, epithelial hyperplasia and metaplasia, periductal round cell infiltration, fibrosis and contraction. In 56 of 93 rats showing only ductuli lesions, testes were either normal or exhibited dilation of the rete testis and of variable numbers of seminiferous tubules, with or without “pressure degeneration” of the germinal epithelium. In the other 37 rats, the testes showed cadmium‐induced injury.Lesions involving both ductuli efferentes and proximal segments of the caput epididymis (13 rats), or the latter alone (46 rats), tended to be associated with more severe testis damage. Epididymal lesions were characterized by focal proliferation and desquamation of duct epithelia, and formation of spermatoceles.The lesions observed were attributed primarily to ischemia, secondary to effects of cadmium upon the capillary bed of the tissues involved. However, their possible enhancement or modification by direct chemical action of cadmium, selenium or zinc upon the duct system or perivascular tissues could not be excluded.

Ultrastructure of the prawn nerve sheaths. Role of fixative and osmotic pressure in vesiculation of thin cytoplasmic laminae.

The sheaths from freshly teased nerve fibers of the prawn exhibit a positive radial birefringence, consistent with their EM appearance as highly organized laminated structures composed of numerous thin cytoplasmic sheets or laminae bordered by unit membranes and arranged concentrically around the axon. The closely apposed membranes in these sheaths are fragile and often break down into rows of vesicles during fixation. Desmosome-like attachment zones occur in many regions of the sheath. The membranes within these zones resist vesiculation and thereby provide a "control" region for relating the type of vesicles formed in the fragile portions of the sheaths to the specific fixation conditions. It is proposed that during fixation the production of artifactual vesicles is governed by an interplay of three factors: (a) direct chemical action of the fixative on the polar strata of adjacent unit membranes, (b) osmotic forces applied to membranes during fixation, and (c) the pre-existing natural relations between adjacent membranes. It is found that permanganate best preserves the continuity of the membranes but will still produce vesicles if the fixative exerts severe osmotic forces. These results support other reports (19) of the importance of comparing tissues fixed by complementary procedures so that systematic artifacts will not be described as characteristic of the natural state.

Microcirculatory Effects of Cortisol. Protective Action Against Na4EDTA Damage.

The above experiments have led us to conclude that corticosteroids have a direct chemical action on the extracellular basement membrane or intercellular binding forces which are most probably responsible for the loss of vascular integrity in the adrenally-insufficient rat. It is suggested that a stabilizing action of Cortisol on the extracellular basement membrane and intercellular cement of capillaries and venules constitutes a hitherto unreported property of this hormone in relation to its anti-inflammatory action.

The difference effect and anodic behavior of hafnium dissolving in hydrofluoric acid

Crystal bar hafnium dissolving in hydrofluoric acid and in hydrofluoric-hydrochloric acid mixtures exhibited a positive difference effect similar to that previously observed for zirconium dissolving in hydrofluoric acid. The effect was so pronounced as to completely overbalance the hydrogen volume developed by the internal polarization current and to reduce the rate of self-dissolution by an additional 1·5-3 mm 3/cm 2 min of H 2. The effect was accompanied by a strong shift of the potential of the hafnium electrode toward noble values. Similar potential changes were observed upon the addition of noble metal salts to the acid mixture. The results of the difference effect studies together with rate measurements in hydrofluoric-hydrochloric acid mixtures appear to confirm previous conclusions with regard to the high rate of dissolution of Hf (no anodic current); namely that the dissolution rate is brought about by direct chemical action of molecular HF. A possible explanation is given for the slight increase of metal dissolution and of K in the presence of HCl additions.

The Difference Effect and Anodic Behavior of Zirconium Dissolving in Hydrofluoric Acid

Zirconium dissolving in hydrofluoric acid exhibited a positive difference effect of such an efficiency that the hydrogen volume developed by the internal polarization current was completely overbalanced by the effect. As with other metals the effect was independent of the concentration of the acid and was accompanied by a strong shift in potential of the Zr electrode toward noble values (passivation). Similar potential changes were also recorded in presence of salts or more noble metals while they were displaced by the Zr. Simultaneously, the rate of dissolution of Zr dropped (nearly to zero with Pt4+ additions). In the latter case the black hydride film on the surface disappeared and the Zr turned bright and shiny (passive Zr). A decrease in formation of the hydride film was observed in other cases of anodic polarization. The activity of Zr returned when the anodic current was cut off. As the effect of local currents, due to anodic polarization is reduced to a minimum, the high rate of dissolution of Zr is explained by direct chemical action of Zr with molecular .

A Chemical Measure of the Effect of Soaps and Detergents on the Skin

Comparatively little is known about the mechanisms whereby dermatitis is produced by soaps and detergents. The irritating effects of these agents have variously been ascribed to their defatting action, sensitizing potential, pH, or direct chemical action on the skin.

The water and electrolyte content of the human heart in congestive heart failure with and without digitalization.

The hearts of 25 patients have been serially analyzed for water, chloride, sodium and potassium content. Sixteen hearts were of patients who died in circulatory heart failure; some received digitalis and some did not. The water content of all hearts was the same. In circulatory heart failure, the sodium increases and potassium decreases but the sum of the two remains the same as in normal hearts, indicating a reciprocal relationship. Digitalis in circulatory heart failure restores the alkali metal values and ratios of heart muscle to near normal levels. Digitalis exerts a direct chemical action on the heart muscle.