After-Potentials and Large Depolarizations of Single Nodes of Ranvier Treated with Veratridine

Potential differences between normal nodes of Ranvier (single fiber from the sciatic nerve of the frog, air-gap method) and a node exposed to 1 to 2.5 x 10^-6 gm veratridine per ml were measured. Negative after-potentials occurred immediately after application of the alkaloid when spike configuration and resting potential were virtually unchanged. The after-potentials decreased in magnitude and their time constant increased as the resting membrane was depolarized either by outward currents or by a train of impulses. Increase of (Na)_o markedly increased the amplitude of the after-potential. After prolonged application of veratridine or with higher concentrations, a large slow depolarization (rate of potential change about 7 mv per second) could be triggered by a train of impulses or even a single spike. This depolarization could promptly be terminated by withdrawing Na. It is concluded that, once the nodal membrane has become permeable to Na (as during a spike), veratridine prevents the normal return of P_Na to its resting value.     

SOLUBILITY OF MUSTARD GAS [BIS (β-CHLOROETHYL) SULFIDE] IN WATER,MOLAR SODIUM CHLORIDE,AND IN SOLUTIONS OF DETERGENTS

1. The solubility of mustard (H) in water and in molar sodium chloride was found to be 5.8 x 10^–3 molar and 3.2 x 10^–3 molar respectively or 0.92 mg. per ml. and 0.5 mg. per ml. Solubility curves have been drawn and the usefulness of this method in examining the homogeneity of H preparations as well as in establishing their solubility, is discussed. 2. Certain detergents increase the solubility of H in water. The solubility was found to increase with the concentration of detergent. 3. Many detergents were found to affect the interfacial tension between H and water so that with slight agitation liquid H breaks up into minute droplets. This in turn greatly accelerates the rate of solution.     

Grain Yield and Water Use Efficiency in Extremely-Late Sown Winter Wheat Cultivars under Two Irrigation Regimes in the North China Plain

Wheat production is threatened by water shortages and groundwater over-draft in the North China Plain (NCP). In recent years, winter wheat has been increasingly sown extremely late in early to mid-November after harvesting cotton or pepper. To improve water use efficiency (WUE) and guide the extremely late sowing practices, a 3-year field experiment was conducted under two irrigation regimes (W1, one-irrigation, 75 mm at jointing; W2, two-irrigation, 75 mm at jointing and 75 mm at anthesis) in 3 cultivars differing in spike size (HS4399, small spike; JM22, medium spike; WM8, large spike). Wheat was sown in early to mid-November at a high seeding rate of 800–850 seeds m⁻². Average yields of 7.42 t ha⁻¹ and WUE of 1.84 kg m⁻³ were achieved with an average seasonal evapotranspiration (ET) of 404 mm. Compared with W2, wheat under W1 did not have yield penalty in 2 of 3 years, and had 7.9% lower seasonal ET and 7.5% higher WUE. The higher WUE and stable yield under W1 was associated with higher 1000-grain weight (TGW) and harvest index (HI). Among the 3 cultivars, JM22 had 5.9%–8.9% higher yield and 4.2%–9.3% higher WUE than WM8 and HS4399. The higher yield in JM22 was attributed mainly to higher HI and TGW due to increased post-anthesis biomass and deeper seasonal soil water extraction. In conclusion, one-irrigation with a medium-sized spike cultivar JM22 could be a useful strategy to maintain yield and high WUE in extremely late-sown winter wheat at a high seeding rate in the NCP.     

Photoreceptor Degeneration in Two Mouse Models for Congenital Stationary Night Blindness Type 2

Light-dependent conductance changes of voltage-gated Ca_v1.4 channels regulate neurotransmitter release at photoreceptor ribbon synapses. Mutations in the human CACNA1F gene encoding the α1F subunit of Ca_v1.4 channels cause an incomplete form of X-linked congenital stationary night blindness (CSNB2). Many CACNA1F mutations are loss-of-function mutations resulting in non-functional Ca_v1.4 channels, but some mutations alter the channels’ gating properties and, presumably, disturb Ca²⁺ influx at photoreceptor ribbon synapses. Notably, a CACNA1F mutation (I745T) was identified in a family with an uncommonly severe CSNB2-like phenotype, and, when expressed in a heterologous system, the mutation was shown to shift the voltage-dependence of channel activation, representing a gain-of-function. To gain insight into the pathomechanism that could explain the severity of this disorder, we generated a mouse model with the corresponding mutation in the murine Cacna1f gene (I756T) and compared it with a mouse model carrying a loss-of-function mutation (ΔEx14–17) in a longitudinal study up to eight months of age. In ΔEx14–17 mutants, the b-wave in the electroretinogram was absent, photoreceptor ribbon synapses were abnormal, and Ca²⁺ responses to depolarization of photoreceptor terminals were undetectable. In contrast, I756T mutants had a reduced scotopic b-wave, some intact rod ribbon synapses, and a strong, though abnormal, Ca²⁺ response to depolarization. Both mutants showed a progressive photoreceptor loss, but degeneration was more severe and significantly enhanced in the I756T mutants compared to the ΔEx14–17 mutants.     

Oxygen metabolism of mammalian spermatozoa. Generation of hydrogen peroxide by rabbit epididymal spermatozoa

Rabbit spermatozoa from the cauda epididymis produced 0.7–0.8nmol of H₂O₂/min per 10⁸ cells at cell concentrations below 10⁷ cells/ml with linear dependence on cell concentration. Above 2 × 10⁷ cells/ml, the rate again became linear with cell concentration but decreased to 0.1–0.2nmol/min per 10⁸ cells. Spermatozoa treated with amphotericin B, which makes the plasma membrane highly permeable to low-molecular-weight compounds, showed a similar dependence of H₂O₂ production rate on cell concentration; below 10⁷ cells/ml the rate was 0.3–0.4nmol/min per 10⁸ cells; above 2 × 10⁷ cells/ml, the rate was 0.1–0.2nmol/min per 10⁸ cells. Hypo-osmotically treated rabbit epididymal spermatozoa, a preparation useful for studying mitochondrial function in sperm [Keyhani & Storey (1973) Biochim. Biophys. Acta 305, 557–565] produced 0.1–0.2nmol/min per 10⁸ cells in the absence of added substrates. The dependence of rate on cell concentration was linear from 10⁷ to 2.2 × 10⁸ cells/ml. This endogenous rate was unaffected by rotenone, but stimulated 4-fold by antimycin A. Addition of the mitochondrial substrates lactate plus malate increased the rate of H₂O₂ production to 0.3nmol/min per 10⁸ cells. The decreased rate of H₂O₂ production observed with intact sperm at high cell concentrations is attributed to reaction of H₂O₂ with the cells, possibly with the plasma membrane, which is lost after hypo-osmotic treatment. Rabbit spermatozoa have glutathione peroxidase and glutathione reductase activities, but these seem to play little role in removal of H₂O₂ generated. The rate at low cell concentration is taken to be the unperturbed rate. The sources of H₂O₂ production in rabbit spermatozoa have been tentatively resolved into a low-molecular-weight component, lost after amphotericin treatment, a mitochondrial component and a rotenone-insensitive component that has not been identified.     

THE COMBINATION OF GELATIN WITH HYDROCHLORIC ACID : II. NEW DETERMINATIONS OF THE ISOELECTRIC POINT AND COMBINING CAPACITY OF A PURIFIED GELATIN.

1. Cooper''s gelatin purified according to Northrop and Kunitz exhibited a minimum of osmotic pressure and a maximum of opacity at pH 5.05 ±0.05. The pH of solutions of this gelatin in water was also close to this value. It is inferred that such gelatin is isoelectric at this pH and not at pH 4.70. 2. Hydrogen electrode measurements with KCl-agar junctions were made with concentrated solutions of this gelatin in HCl up to 0.1 M. The combination curve calculated from these data is quite exactly horizontal between pH 2 and 1, indicating that 1 gm. of this gelatin can combine with a maximum of 9.35 x 10^–4 equivalents of H⁺. 3. Conductivity titrations of this gelatin with HCl gave an endpoint at 9.41 (±0.05) x 10^–4 equivalents of HCl per gram gelatin. 4. E.M.F. measurements of the cell without liquid junction, Ag, AgCl, HCl + gelatin, H₂, lead to the conclusion that this gelatin in 0.1 M HCl combines with a maximum of 9.4 x 10^–4 equivalents of H⁺ and 1.7 x 10^–4 equivalents of Cl^- per gram gelatin.     

ON THE QUANTA OF LIGHT PRODUCED AND THE MOLECULES OF OXYGEN UTILIZED DURING CYPRIDINA LUMINESCENCE

A study of the oxygen consumed per lumen of luminescence during oxidation of Cypridina luciferin in presence of luciferase, gives 11.4 x 10^–5 gm. oxygen per lumen or 88 molecules per quantum of λ = 0.48µ, the maximum in the Cypridina luminescence spectrum. For reasons given in the text, the actual value is probably somewhat less than this, perhaps of the order of 6.48 x 10^–5 gm. per lumen or 50 molecules of oxygen and 100 molecules of luciferin per quantum. It is quite certain that more than 1 molecule per quantum must react. On the basis of a reaction of the type: luciferin + 1/2 O₂ = oxyluciferin + H₂O + 54 Cal., it is calculated that the total efficiency of the luminescent process, energy in luminescence/heat of reaction, is about 1 per cent; and that a luciferin solution containing 4 per cent of dried Cypridina material should rise in temperature about 0.001°C. during luminescence, and contain luciferin in approximately 0.00002 molecular concentration.     

Efficiency and pattern of UV pulse laser-induced RNA-RNA cross-linking in the ribosome

Escherichia coli ribosomes were irradiated with a KrF excimer laser (248 nm, 22 ns pulse) with incident pulse energies in the range of 10–40 mJ for a 1 cm² area, corresponding to fluences of 4.5 to 18 × 10⁹ W m^–2, to determine strand breakage yields and the frequency and pattern of RNA–RNA cross- linking in the 16S rRNA. Samples were irradiated in a cuvette with one laser pulse or in a flow cell with an average of 4.6 pulses per sample. The yield of strand breaks per photon was intensity dependent, with values of 0.7 to 1.3 × 10^–3 over the incident intensity range studied. The yield for RNA–RNA cross-linking was 3 × 10^–4 cross-links/photon at the intensity of 4.5 × 10⁹ W m^–2, an ~4-fold higher yield per photon than obtained with a transilluminator. The cross-link yield/photon decreased at higher light intensities, probably due to intensity-dependent photoreversal. The pattern of cross-linking was similar to that observed with low intensity irradiation but with four additional long-range cross-links not previously seen in E.coli ribosomes. Cross- linking frequencies obtained with one laser pulse are more correlated to internucleotide distances than are frequencies obtained with transilluminator irradiation.     

Bacterioplankton in Antarctic Ocean Waters During Late Austral Winter: Abundance, Frequency of Dividing Cells, and Estimates of Production

Bacterioplankton productivity in Antarctic waters of the eastern South Pacific Ocean and Drake Passage was estimated by direct counts and frequency of dividing cells (FDC). Total bacterioplankton assemblages were enumerated by epifluorescent microscopy. The experimentally determined relationship between in situ FDC and the potential instantaneous growth rate constant (μ) is best described by the regression equation ln μ = 0.081 FDC − 3.73. In the eastern South Pacific Ocean, bacterioplankton abundance (2 × 10⁵ to 3.5 × 10⁵ cells per ml) and FDC (11%) were highest at the Polar Front (Antarctic Convergence). North of the Subantarctic Front, abundance and FDC were between 1 × 10⁵ to 2 × 10⁵ cells per ml and 3 to 5%, respectively, and were vertically homogeneous to a depth of 600 m. In Drake Passage, abundance (10 × 10⁵ cells per ml) and FDC (16%) were highest in waters south of the Polar Front and near the sea ice. Subantarctic waters in Drake Passage contained 4 × 10⁵ cells per ml with 4 to 5% FDC. Instantaneous growth rate constants ranged between 0.029 and 0.088 h⁻¹. Using estimates of potential μ and measured standing stocks, we estimated productivity to range from 0.62 μg of C per liter · day in the eastern South Pacific Ocean to 17.1 μg of C per liter · day in the Drake Passage near the sea ice.     

THE TOTAL LUMINOUS EFFICIENCY OF LUMINOUS BACTERIA

Methods are described for measuring the light emitted by an emulsion of luminous bacteria of given thickness, and calculating the light emitted by a single bacterium, measuring 1.1 x 2.2 micra, provided there is no absorption of light in the emulsion. At the same time, the oxygen consumed by a single bacterium was measured by recording the time for the bacteria to use up .9 of the oxygen dissolved in sea water from air (20 per cent oxygen). The luminescence intensity does not diminish until the oxygen concentration falls below 2 per cent, when the luminescence diminishes rapidly. Above 2 per cent oxygen (when the oxygen dissolving in sea water from pure oxygen at 760 mm. Hg pressure = 100 per cent) the bacteria use equal amounts of oxygen in equal times, while below 2 per cent oxygen it seems very likely that rate of oxygen absorption is proportional to oxygen concentration. By measuring the time for a tube of luminous bacteria of known concentration saturated with air (20 per cent oxygen) to begin to darken (2 per cent oxygen) we can calculate the oxygen absorbed by one bacterium per second. The bacteria per cc. are counted on a blood counting slide or by a centrifugal method, after measuring the volume of a single bacterium (1.695 x 10^–12 cc.). Both methods gave results in good agreement with each other. The maximum value for the light from a single bacterium was 24 x 10^–14 lumens or 1.9 x 10^–14 candles. The maximum value for lumen-seconds per mg. of oxygen absorbed was 14. The average value for lumen-seconds per mg. O₂ was 9.25. The maximum values were selected in calculating the efficiency of light production, since some of the bacteria counted may not be producing light, although they may still be using oxygen. The "diet" of the bacteria was 60 per cent glycerol and 40 per cent peptone. To oxidize this mixture each mg. of oxygen would yield 3.38 gm. calories or 14.1 watts per second. 1 lumen per watt is therefore produced by a normal bacterium which emits 14 lumen-seconds per mg. O₂ absorbed. Since the maximum lumens per watt are 640, representing 100 per cent efficiency, the total luminous efficiency if .00156. As some of the oxygen is used in respiratory oxidation which may have nothing to do with luminescence, the luminescence efficiency must be higher than 1 lumen per watt. Experiments with KCN show that this substance may reduce the oxygen consumption to 1/20 of its former value while reducing the luminescence intensity only ¼. A partial separation of respiratory from luminescence oxidations is therefore effected by KCN, and our efficiency becomes 5 lumens per watt, or .0078. This is an over-all efficiency, based on the energy value of the "fuel" of the bacteria, regarded as a power plant for producing light. It compares very favorably with the 1.6 lumens per watt of a tungsten vacuum lamp or the 3.9 lumens per watt of a tungsten nitrogen lamp, if we correct the usual values for these illuminants, based on watts at the lamp terminals, for a 20 per cent efficiency of the power plant converting the energy of coal fuel into electric current. The specific luminous emission of the bacteria is 3.14 x 10^–6 lumens per cm². One bacterium absorbs 215,000 molecules of oxygen per second and emits 1,280 quanta of light at λ_max = 510µµ. If we suppose that a molecule of oxygen uniting with luminous material gives rise to the emission of 1 quantum of light energy, only 1/168 of the oxygen absorbed is used in luminescence. On this basis the efficiency becomes 168 lumens per watt or 26.2 per cent.     

Association of Right Ventricular Pressure and Volume Overload with Non-Ischemic Septal Fibrosis on Cardiac Magnetic Resonance

Background

Non-ischemic fibrosis (NIF) on cardiac magnetic resonance (CMR) has been linked to poor prognosis, but its association with adverse right ventricular (RV) remodeling is unknown. This study examined a broad cohort of patients with RV dysfunction, so as to identify relationships between NIF and RV remodeling indices, including RV pressure load, volume and wall stress.

Methods and Results

The population comprised patients with RV dysfunction (EF<50%) undergoing CMR and transthoracic echo within a 14 day (5±3) interval. Cardiac structure, function, and NIF were assessed on CMR. Pulmonary artery systolic pressure (PASP) was measured on echo. 118 patients with RV dysfunction were studied, among whom 47% had NIF. Patients with NIF had lower RVEF (34±10 vs. 39±9%; p = 0.01) but similar LVEF (40±21 vs. 39±18%; p = 0.7) and LV volumes (p = NS). RV wall stress was higher with NIF (17±7 vs. 12±6 kPa; p<0.001) corresponding to increased RV end-systolic volume (143±79 vs. 110±36 ml; p = 0.006), myocardial mass (60±21 vs. 53±17 gm; p = 0.04), and PASP (52±18 vs. 41±18 mmHg; p = 0.001). NIF was associated with increased wall stress among subgroups with isolated RV (p = 0.005) and both RV and LV dysfunction (p = 0.003). In multivariable analysis, NIF was independently associated with RV volume (OR = 1.17 per 10 ml, [CI 1.04–1.32]; p = 0.01) and PASP (OR = 1.43 per 10 mmHg, [1.14–1.81]; p = 0.002) but not RV mass (OR = 0.91 per 10 gm, [0.69–1.20]; p = 0.5) [model χ² = 21; p<0.001]. NIF prevalence was higher in relation to PA pressure and RV dilation and was > 6-fold more common in the highest, vs. the lowest, common tertile of PASP and RV size (p<0.001).

Conclusion

Among wall stress components, NIF was independently associated with RV chamber dilation and afterload, supporting the concept that NIF is linked to adverse RV chamber remodeling.     

THE COMBINATION OF CERTAIN PROTEINS WITH HYDROCHLORIC ACID

Electromotive force measurements of cells without liquid junction, of the type Ag, AgCl, HCl + protein, H₂, have been made at 30°C. with the proteins gelatin, edestin, and casein in 0.1 M hydrochloric acid. The data are consistent with the assumptions of a constant combining capacity of each protein for hydrogen ion, no combination with chloride ion, and Failey''s principle of a linear variation of the logarithm of the mean activity coefficient of the acid with increasing protein concentration. The combining capacities for hydrogen ion so obtained are 13.4 x 10^–4 for edestin, 9.6 x 10^–4 for gelatin, and 8.0 x 10^–4 for casein, in equivalents of combined H⁺ per gm. of protein.     

Electrolyte distribution and active salt uptake in frog skin

1. The "chloride space" in frog skin was determined and found to be 69.7 per cent by weight of wet skin. The chloride space occupies about 94 per cent of the total water space of skin. From this and other information, it appears that the "non-chloride space" measures only a part of the space occupied by the structural elements of skin. This space is referred to here as the intracellular compartment and the remainder as the extracellular compartment of frog skin. On this basis, potassium and sodium in skin are distributed as follows: total sodium, 60 to 75 µeq./gm. of wet skin; all sodium is probably extracellular; total potassium, 39 to 49 µeq./gm.; intracellular potassium, 37 to 47 µeq./gm. 2. Skins were immersed in solutions differing from each other in their sodium and potassium concentrations. Three levels of NaCl were studied: 48, 119, and 169 µeq./ml. For each of these solutions (referred to below as diluted, physiological, and concentrated saline), the potassium levels were varied from 0.1 to 20 µeq./ml. For skins in solutions low in potassium and high in sodium, it was found that an exchange of intracellular potassium against extracellular sodium occurs. The ratio for the number of potassium ions lost/number of sodium ions gained was 4:1,4:6, and 4:8 for skin in K⁺-free diluted, physiological, and concentrated saline, respectively. 3. Uptake of NaCl by the epithelium of frog skin is dependent on the potassium concentration of the environment. For skins in physiological saline, net uptake of NaCl was optimal (0.90 µeq. x cm.^–2 x hr.^–1) at 1 to 5 µeq. K₊/ml. For skins in diluted and concentrated saline optimal NaCl uptake was seen at potassium concentrations of approximately 5 and 10 µeq. K₊/ml., respectively. Net uptake of NaCl by the skin is also discussed, with relation to the potassium balance of skin. 4. Skin potentials decreased with increasing extracellular potassium concentration when diluted saline solutions were used. The opposite of this was found for skins in concentrated saline. For skins in physiological saline, skin potentials rose sharply from rather low values, when placed in solutions very low in potassium, to relatively high values, when immersed in solutions containing 1 to 5 µeq. K⁺/ml. Further increase in potassium concentration of the bath led to slight reductions in skin potentials. The highest potentials observed were of the order of 40 mv. In all cases studied, the inside was positive with relation to the outside. 5. It can be shown that values for intracellular potassium concentration as a function of extracellular potassium concentration satisfy, at a first but good approximation, Freundlich's isotherm. A modification of Freundlich's isotherm, recently introduced by Sips, may also be used to correlate the experimental data quantitatively. Since the latter isotherm has a rational interpretation, it is suggested that this be used, rather than Freundlich's isotherm, to express quantitatively the dependence of intracellular on extracellular potassium in frog skin.     

STUDIES IN THE PHYSICAL CHEMISTRY OF THE PROTEINS : II. THE RELATION BETWEEN THE SOLUBILITY OF CASEIN AND ITS CAPACITY TO COMBINE WITH BASE. THE SOLUBILITY OF CASEIN IN SYSTEMS CONTAINING THE PROTEIN AND SODIUM HYDROXIDE.

1. The solubility in water of purified, uncombined casein has previously been reported to be 0.11 gm. in 1 liter at 25°C. This solubility represents the sum of the concentrations of the casein molecule and of the soluble ions into which it dissociates. 2. The solubility of casein has now been studied in systems containing the protein and varying amounts of sodium hydroxide. It was found that casein forms a well defined soluble disodium compound, and that solubility was completely determined by (a) the solubility of the casein molecule, and (b) the concentration of the disodium casein compound. 3. In our experiments each mol of sodium hydroxide combined with approximately 2,100 gm. of casein. 4. The equivalent combining weight of casein for this base is just half the minimal molecular weight as calculated from the sulfur and phosphorus content, and one-sixth the minimal molecular weight calculated from the tryptophane content of casein. 5. From the study of systems containing the protein and very small amounts of sodium hydroxide it was possible to determine the solubility of the casein molecule, and also the degree to which it dissociated as a divalent acid and combined with base. 6. Solubility in such systems increased in direct proportion to the amount of sodium hydroxide they contained. 7. The concentration of the soluble casein compound varied inversely as the square of the hydrogen ion concentration, directly as the solubility of the casein molecule, Su, and as the constants Ka₁ and Ka₂ defining its acid dissociation. 8. The product of the solubility of the casein molecule and its acid dissociation constants yields the solubility product constant, Su·Ka₁·Ka₂ = 2.2 x 10^–12 gm. casein per liter at 25°C. 9. The solubility of the casein molecule has been estimated from this constant, and also from the relation between the solubility of the casein and the sodium hydroxide concentration, to be approximately 0.09 gm. per liter at 25°C. 10. The product of the acid dissociation constants, Ka₁ and Ka₂, must therefore be 24 x 10^–12N. 11. It is believed that these constants completely characterize the solubility of casein in systems containing the protein and small amounts of sodium hydroxide.     

Uptake and accumulation of zinc in juvenile rainbow trout,Salmo gairdneri

Synopsis The toxicity of zinc to rainbow trout was determined and the 72 h median lethal concentration was found to be 2.00 mg l^–1 in freshwater, hardness 7.50 mg l^–1 as calcium. An insignificant increase in zinc concentration of internal tissues occurred in fish exposed to 1.52 mg l^–1 in freshwater for 72 h. However, there was a significant uptake of zinc by gills and the body surface. Fish exposed to 10 mg l^–1 zinc for 72 h in two-thirds sea water showed significant zinc uptake by liver, rectum and muscle, when compared to control fish. Drinking rate decreased from 1.43 to 0.26 ml kg^–1 h^–1 when zinc sulphate was added to freshwater. Trout adapted to two-thirds sea water showed no decrease in drinking, about 7 ml kg^–1 h^–1 when zinc was added to the water.     

Morphological and physiological responses of the halophyte, Odyssea paucinervis (Staph) (Poaceae), to salinity

In this study, salt tolerance was investigated in Odyssea paucinervis Staph, an ecologically important C₄ grass that is widely distributed in saline and arid areas of southern Africa. Plants were subjected to 0.2%, 10%, 20%, 40%, 60% and 80% sea water dilutions (or 0.076, 3.8, 7.6, 15.2, 22.8, and 30.4 parts per thousand) for 11 weeks. Increase in salinity from 0.2% to 20% sea water had no effect on total dry biomass accumulation, while further increase in salinity to 80% sea water significantly decreased biomass by over 50%. Morphological changes induced by salinity included reductions in the number of culms, leaves and internodes as well as decreases in internode length and leaf length:leaf width ratios. Carbon dioxide exchange, leaf conductance and transpiration decreased at salinities of 40% and higher, while quantum yield of photosystem II (PSII), electron transport rate (ETR) through PSII and intrinsic photosynthetic efficiency generally decreased at salinities of 60% and higher compared to 0.2% sea water. Concentrations of Na⁺ and Cl⁻ increased significantly with salinity increase in both roots and shoots. Na⁺/K⁺ ratios in the roots and shoots ranged from 0.66 to 3.28 and increased with increase in substrate salinity. The maximal rate of secretion at 80% sea water was 415 nmol cm⁻² d⁻¹ for Na⁺ and 763 nmol m⁻² d⁻¹ for Cl⁻ with high selectivity for these two ions. Predawn and midday ψ decreased with increase in salinity and were more negative than those of the treatment solutions. The concentration of proline increased with increase in salinity in both roots and shoots. The data clearly indicated that O. paucinervis is a highly salt-tolerant species that is morphologically and physiologically adapted to a saline environment.     

Sodium Efflux and Potential Differences across the Irrigated Gill of Sea Water-Adapted Rainbow Trout (Salmo gairdneri)

Sodium extrusion (J_out^Na) was measured across the gills of rainbow trout, Salmo gairdneri, adapted to sea water (SW) using a gill-irrigation system of small volume. The potential difference (TEP) was also measured under similar conditions. J_out^Na was usually between 100–250 µeq (100 g)^–1 h^–1, about an order of magnitude faster than in fresh water (FW)-adapted trout, but slower than has been reported for any other marine teleost. The TEP was between 10–11 mV, body fluids positive to SW. When the external medium was changed from SW to FW J_out^Na was reduced to about 25 % of the initial value, and the TEP was reduced by 40–50 mV (i.e. body fluids negative by 30–40 mV). Addition of either Na⁺ or K⁺ in SW concentrations reversed the changes; J_out^Na increased and the gill repolarized. The electrical behavior and sodium efflux in irrigated trout gill is qualitatively the same as has been reported for unanaesthetized, free-swimming fish of other species. Thus, the irrigated gill provides an adequate model for studying the mechanism of sodium extrusion in marine teleosts.     

Biophysical Effects of Adrenaline on the Smooth Muscle of the Rabbit Common Carotid Artery

Effects of adrenaline on the smooth muscle of the rabbit common carotid artery were studied by the partitional chamber method. The experiments on excitation-contraction coupling were carried out in isotonic Krebs solution; the other experiments were carried out in hypertonic Krebs solution. Adrenaline (10^-7 g/ml) caused rhythmical electrical and mechanical activity of arterial strips in isotonic Krebs solution. By addition of adrenaline (10^-5 g/ml), the membrane was depolarized by about 10 mv and the amplitude of the electrotonic potential was decreased by 40–50% of the control in hypertonic Krebs solution. Present experimental results suggest that the depolarization of the membrane and the decrease of the amplitude of the electrotonic potential in the artery are due to the increase of Na and Cl conductance. Contraction appeared in all preparations exposed to 10^-8 g/ml adrenaline; at that concentration membrane potential and membrane resistance showed little or no change.     

Minor elements and evolution

Summary Minor elements such as molybdenum and iron are essential elements or bioelements for microorganisms, plants, and higher animals. However, chromium is not regarded as a bioelement in the same sense. This may be explained by their relative concentrations in the sea water.Molybdenum is the most abundant of the transition elements in sea water. Its participation in different oxido-reductases such as nitrogenase, nitrate reductase, and CO₂ reductase of primitive bacteria could be related to its abundance.Good correlation can be found between the biological behaviour of different elements and their concentration in sea water. This suggests the hypothesis that the composition of the present sea water reflects that of the primeval sea water at the time of the evolution of these enzyme systems.A concentration in the sea of about 1~5 nM may be regarded as critical. Elements with concentrations in sea water above this critical concentration could influence early evolutionary events, and so became either essential elements or neutral elements; organisms evolved independently of trace elements with concentrations less than the critical concentration.Abbreviation nM total gram-atoms/liter × 10^–9 of an element in dissolved substances containing the element Dedicated to Prof. Otto Hofmann-Ostenhof on the occasion of his 60th birthday.     

THE COMBINATION OF EDESTIN WITH HYDROCHLORIC ACID

Electromotive force measurements of cells without liquid junction, of the type Ag, AgCl, HCl + protein, H₂, lead to the conclusion that 1 gm. of edestin (or, more probably, edestan) combines with a maximum of 13.4 x 10^–4 equivalents of H⁺ and 3.9 x 10^–4 equivalents of Cl^-, when the protein is dissolved in 0.1 M HCl.