A LIGHT-SCATTERING TECHNIQUE FOR THE STUDY OF THE PERMEABILITY OF RAT BRAIN SYNAPTOSOMES IN VITRO

Abstract— (1) Swelling of synaptosomes was measured spectrophotometrically by recording changes in extinction at 520 nm.
(2) Synaptosomes behaved as osmometers in NaCl solutions. When the tonicity of the medium was changed, synaptosome volume changed in accordance with Boyle and van't Hoff's Law. These changes were reversed on restoring the tonicity of the medium.
(3) The rate at which a solute entered the synaptosome was determined from the rate of swelling in the presence of that solute. Permeability of synaptosomes to non-electrolytes was in the order glucose ≪ glycerol < thiourea = formamide < propylene glycol = dimethylsulphoxide.
(4) Synaptosomes were freely permeable to ammonium and acetate ions and impermeable to Ca²⁺, Mg²⁺, PO₄²⁻, SO₄²⁻ and oxalate ions.     

THE INFLUENCE OF TASTANTS ON ORAL IRRITATION BY CAPSAICIN

Single-point intensity scaling and time-intensity methods were used to record oral irritation from solutions of 2 ppm capsaicin, capsaicin with added sucrose (0.04M), NaCl (0.3M), citric acid (0.01M) or xanthan gum (0.2%). Only sucrose depressed mouth-burn, both in magnitude and duration. The viscosity imparted by xanthan retarded perception of mouth-burn but did not effect its duration. While single-point scaling averaged perceived intensity across time, time-intensity provided much more information by displaying perception from onset to decay. Eaters and non-eaters of chili peppers did not differ in their perception of mouth-burn.     

Does calcium ameliorate the negative effect of NaCl on melon root water transport by regulating aquaporin activity?

The hydraulic conductance ( L ₀) of detached, exuding root systems from melon ( Cucumis melo cv. Amarillo oro) was measured. All plants received a half-strength Hoagland nutrient solution, and plants stressed either solely with NaCl (50 mM) or with NaCl (50 mM) following treatment (2 d) with CaCl₂ (10 mM) were compared with controls and CaCl₂-treated (10 mM) plants. The L ₀ of NaCl-treated plants was markedly decreased when compared to control and CaCl₂-treated plants, but the decrease was smaller when NaCl was added to plants previously treated with CaCl₂. A similar effect was observed when the flux of Ca²⁺ into the xylem and the Ca²⁺ concentration in the plasma membrane of the root cells were determined. In control, CaCl₂- and NaCl + CaCl₂-treated plants, HgCl₂ treatment (50 μM) caused a sharp decline in L ₀ to values similar to those of NaCl-stressed roots, but L ₀ was restored by treatment with 5 mM DTT. However, in NaCl roots only a slight effect of Hg²⁺ and DTT were observed. The effect of all treatments on L ₀ was similar to that on osmotic water permeability ( P _f) of individual protoplasts isolated from roots. The results suggest that NaCl decreased the passage of water through the membrane and roots by reducing the activity of Hg-sensitive water channels. The ameliorative effect of Ca²⁺ on NaCl stress could be related to water-channel function.     

Nitrogen fixation (C2H2 reduction) by Medicago nodules and bacteroids under sodium chloride stress

Medicago ciliaris (L.) All., a salt-tolerant legume, was not nodulated by Rhizobium meliloti (2011), a strain commonly used for field inoculation of alfalfas. A strain of Rhizobium meliloti (ABS7) was isolated from saline Algerian soils. It is generally more salt-resistant than strain 2011, exhibits a higher rate of growth and induces the formation of nodules on M. ciliaris . C₂H₂ reduction activity of M. ciliaris nodules was inhibited by 50% in the presence of 200 m M NaCl in the culture medium. whereas 100 m M NaCl was sufficient to inhibit the activity of nodules of M. sativa (L. cv. Europe). C₂H₂ reduction by bacteroids, isolated from nodules of the two species of alfalfa, was directly inhibited by the presence of NaCl in the incubation medium. In both cases, glucose could support bacteroid nitrogen fixation, but only in a narrow range of O₂ tensions. Bacteriods from M. ciliaris were more tolerant to salt than M. sativa ones. The salt resistance of bacteroids from nodules of plants watered with NaCl solutions was not improved in either species. Salt directly added to the incubation mixture of bacteroids or to the culture medium of plants inhibited O₂ uptake of bacteroids isolated from nodules of both M. ciliaris and M. sativa . The depressive effect of NaCl on bacteroid C₂H₂ reduction could be directly related to the drop in bacteroid respiration. The nitrogen fixation capacity of the M. ciliaris-Rhizobium meliloti (ABS7) symbiosis under saline conditions leads us to recommend the introduction of this association in salt-troubled areas.     

Comparison of the Kinetics of [3H]Diazepam and [3H]Flunitrazepam Binding to Cortical Synaptosomal Membranes

Abstract: [³H]Diazepam and [³H]flunitrazepam ([³H]FNP) binding to washed and frozen synaptosomal membranes from rat cerebral cortex were compared. In Tris-citrate buffer, γ -aminobutyric acid (GABA) and NaCl both increased [³H]diazepam binding more than [³H]FNP binding. GABA and pentobarbital both enhanced this effect of NaCl. Because of the extremely rapid dissociation of [³H]diazepam in the absence of NaCl and GABA, the B_max (maximal binding capacity) was smaller by the filtration assay than by the centrifugation assay. [³H]FNP, which dissociates more slowly, had the same B_max in both assays. [³H]Diazepam association had two components, and was faster than [³H]FNP association. [³H]Diazepam dissociation, which also had two components, was faster than that of [³H]FNP, and also had a greater fraction of rapidly dissociating species. [³H]FNP dissociation was similar when initiated by diazepam, flunitrazepam, clonazepam, or Ro15-1788, which is a benzodiazepine antagonist. [³H]Diazepam dissociation with Ro15-1788, flunitrazepam, or clonazepam was slower than with diazepam. GABA and NaCl, but not pentobarbital, increased the percentage of slowly dissociating species. This effect of NaCl was potentiated by GABA and pentobarbital. The results support the cyclic model of benzodiazepine receptors existing in two interconvertible conformations, and suggest that, distinct from their binding affinity, some ligands (like flunitrazepam) are better than others (like diazepam) in inducing the conversion of the receptor to the higher-affinity state.     

Sperm structure and motility of the freshwater teleost Cottus gobio

When motility of spermatozoa of Cottos gobio was initiated with distilled water, the motility rate decreased to 0% within 1 min, and significant signs of osmotic alterations were observed at the end of the motility period. By contrast, in 50 mmol 1⁻¹ NaCl solution, the motility rate persisted for 120–140 min. In both distilled water and in 50 mmol 1⁻¹ NaCl solution, the main swimming type of spermatozoa was linear motion during the whole motility period. The initial swimming velocity (50.0 ± 2.1 μm s⁻¹) measured 10 s after motility initiation was similar in both distilled water and in 50 mmol 1⁻¹ NaCl solution. In distilled water, the velocity decreased to <20 μm s⁻¹ (locally motile) during the first minute of the motility phase. In 50 mmol 1⁻¹ NaCl solutions, it remained at a constant level during the first 60 min of the motility period, but then started to decrease to <20 μm s⁻¹ after 120 min. When 5 mmol 1⁻¹ potassium cyanide, antimycin or atractyloside was added to the 50 mmol 1⁻¹ NaCl solution, the motility period was reduced to ≤2min. Ten millimoles per litre 2-deoxy-D-glucose, malonate or a mixture of 5 mmol 1⁻¹ atractyloside and 5 mmol 1⁻¹ carnithine did not effect the duration of the motility period. This indicates that sperm energy metabolism depends mainly on respiration rate and fatty acid metabolism.     

THE PRODUCTION OF ANTIBIOTICS IN SOIL V. BREAKDOWN OF GRISEOFULVIN IN SOIL

When griseofulvin (I; R = Cl, R '= OCH₃), a chlorine-containing antibiotic produced by Penicillium nigricans , was added to fresh garden loam, after an initial lag it disappeared rapidly. When further griseofulvin was added it was inactivated from the start and at rates which increased with each successive addition, suggesting that it was degraded biologically. The numbers of one organism, a Pseudomonas sp., increased in the soil steadily after adding griseofulvin.
When a little soil was added to a solution (pH 7·0) containing inorganic salts and griseofulvin as the sole carbon source, bioassays showed that the griseofulvin disappeared within 5 days. An organism isolated from the broth was identified as the Pseudomonas sp. thought to break down griseofulvin in soil. Griseofulvin also disappeared from a broth at pH 5·0 inoculated with soil, but at this lower pH value a dematiaceous fungus was responsible for its breakdown.
The Pseudomonas sp. also degraded two derivatives of griseofulvin, dechlorogriseofulvin (I; R = H, R'= OCH₃) and the amine (I; R = Cl, R '= NH₂). Cl^– was detected in the solutions after breakdown of griseofulvin by the Pseudomonas ; the amount present agreed well with that calculated on the assumption that all the chlorine in the griseofulvin supplied was liberated as Cl^–. Spectrophotometric examination of the solutions showed no metabolites with the aromatic ring intact, and confirmed the complete breakdown of griseofulvin suggested by the liberation of Cl-.     

Melatonin Biosynthesis in Cultured Chick Retinal Photoreceptor Cells: Calcium and Cyclic AMP Protect Serotonin N-Acetyltransferase from Inactivation in Cycloheximide-Treated Cells

Abstract: The aim of the present study was to examine the roles of membrane depolarization, calcium influx, and cyclic AMP synthesis in regulating the stability and inactivation of serotonin N -acetyltransferase activity (NAT) in cultured chick photoreceptor cells. NAT activity was induced by pretreating cells for 6 h with 1 µ M forskolin. Cycloheximide was subsequently added, and the rate of loss of enzyme activity (inactivation) was determined. After induction, in the presence of cycloheximide, NAT activity declined with a half-life of ∼30 min. The rate of inactivation was greatly reduced when depolarizing concentrations of K⁺, forskolin, 8-bromoadenosine 3',5'-cyclic monophosphate, or 3-isobutyl-1-methylxanthine were added together with cycloheximide. The apparent increase in NAT stability caused by K⁺ was abolished by addition of EGTA or nifedipine and potentiated by Bay K 8644, indicating the involvement of Ca²⁺ influx through dihydropyridine-sensitive channels. MDL-12330A, an inhibitor of K⁺-stimulated cyclic AMP formation, blocked the effect of depolarizing concentrations of K⁺. This result suggests that the effect of Ca²⁺ influx on the stability of NAT is at least partially mediated by increased levels of cyclic AMP. Thus, depolarization-evoked Ca²⁺ influx and cyclic AMP formation have two roles in the regulation of NAT activity in chick photoreceptor cells. First, they stimulate the de novo synthesis of NAT or a regulatory protein required for NAT activity. Second, they increase the half-life of the enzyme, presumably by regulating the turnover of existing enzyme molecules.     

INFLUENCE OF RELATIVE HUMIDITY ON SURVIVAL OF THE CITRUS LEAF-MINER, PHYLLOCNZSTZS CITRELLA STAINTON (LEPIDOPTERA: PHYLLOCNISTIDAE)

Abstract The relationshLps between relative humidity (RH) and survival rates of eggs, all larval stages and pupae of the citrus leaf-miner, Phyllooiistis citrella Stainton, were determined by laboratory experiments. The survival of the citrus leaf-miner was observed at seven levels of relative humidity from 35% RH to 95% RH at intervals of 10% RH, with 12 L: 12 D photoperiod and temperatiure (29±0.5) C. The relative humidity was controlled by saturated solutions of MgCl₂ 6H₂O, K₂CO₃ 2H₂O, C₆H₁₂O₆, NaNO₂, NaCl, KCl, and Pb(NO₃)₂. The results showed that lower relative humidity is unfavorable for incubation of the eggs, survival of the larvae and eclosion of the pupae. The survival rates increased generally with rising of relative humidity within the range of 35% - 85% RH, and the maximum survival rates occurred at 85% RH for different life stages. The variations in hatching rates of the eggs, survival rates of the larvae and emergence rates of the pupae were great, but unimodal at different relative humidity. The effect of relative humidity on survival rates of the citrus leaf-miner could be simulated by regression analysis, using a polynomial function of three orders, and the results of fitting the model to the observed data are presented and discussed.     

PERCEIVED SALTINESS OF TABLE SPREADS OF VARYING FAT COMPOSITIONS

Four types of spread with 80% fat, but varying in the origin of the fat (milk/vegetable) and in the proportion of oil versus solid fat (0–90% vegetable oil), were manufactured at NaCl concentrations of 1.0, 1.5 and 2.0%. Their saltiness and degree of melting in the mouth were rated using the time-intensity (TI) procedure. The perceived maximum saltiness of each NaCl concentration varied widely, samples with 80% milk fat + 20% vegetable oil being the most salty and those with 15% vegetable fat + 85% vegetable oil the least salty. The differences in saltiness were not directly related to the degree of melting in the mouth. The results demonstrate that extrapolating saltiness on the basis of NaCl contents over brands of products would be risky, since saltiness and NaCl contents are not necessarily correlated even in apparently similar products.     

Responses of photosynthesis to NaCl in gametophytes of Acrostichum aureum

Gametophytes of Acrostichum aureum were cultured in 0.0 to 1.0% NaCl solutions or in NaCl‐free solution and then transferred to 1.0% NaCl solution. Photosynthetic light‐response curves, efficiency of the primary photochemical reaction, relative electron transport rate, and photochemical and non‐photochemical quenching at steady state were determined by photosynthetic O₂ evolution and in vivo chlorophyll fluorescence. Results obtained showed that the chlorophyll fluorescence parameters, F_v/F_m and F'_v/F'_m and αO₂ (the initial linear slope of the photosynthetic light‐response curve) increased in gametophytes grown in NaCl. Linear electron transport rate was stimulated by NaCl. Based on the chlorophyll content, light‐saturated photosynthesis in gametophytes grown in 0.2 to 0.7% NaCl increased slightly; it decreased in gametophytes grown in 1.0% NaCl. Photochemical quenching decreased in NaCl‐grown gametophytes at all photosynthetic photon flux density (PPFD) levels measured, but there was no increase in non‐photochemical quenching. The chlorophyll a/b ratio increased with increasing NaCl concentration in culture solutions. These results indicated that NaCl enhanced photochemical efficiency of photosystem II (PSII) and photosynthetic linear electron transport, thus resulting in the development of an excitation pressure in PSII. Such excitation pressure might act as a signal for photosynthetic acclimation to salt stress, thus allowing the gametophytes to grow in their natural habitats.     

RESPONSE SURFACES OF SENSORY CHARACTERISTICS FOR REDUCED SODIUM CHLORIDE AND PHOSPHATE SALTS IN EMULSIFIED TURKEY SAUSAGES

Emulsified turkey sausages (ETS) were prepared using varying concentrations of sodium chloride (NaCl; 1.5 to 2.0%), sodium tripolyphosphate (STPP, 0 to 0.5%), and sodium acid pyrophosphate (SAPP, 0 to 0.25%). The sensory characteristics (response variables) of saltiness, soapiness, and texture were evaluated using a trained taste panel. Response surface methodology was used to design and analyze this study. Over the levels of STPP and SAPP, saltiness increased as levels of NaCl were increased. When STPP and SAPP were evaluated in combination with NaCl, saltiness increased slightly as levels of STPP were increased; and saltiness decreased as levels of SAPP were decreased. Soapiness increased at low levels of NaCl (1.5%) as STPP increased. Texture firmness decreased as SAPP increased and STPP decreased at low levels of NaCl (1.5%). Results suggest that sensory perceptions in ETS products are a combination of NaCl, SAPP, and STPP mixtures.     

PERCEPTION OF FAT IN A MILK MODEL SYSTEM USING MULTIDIMENSIONAL SCALING

This study examined the contributions of stimulus fat content and flavor volatiles to the perception of fat in a milk model system. The model system was formulated by adding bland vegetable oil (0%, 5%, or 10% w/v) and natural cream flavor (0%, 0.5% or 1% w/v) to a skim milk base. Panelists judged pairs of samples for similarity on the basis of three attributes (fat content, mouthcoating and thickness) and the results were analyzed using a multidimensional scaling procedure. Two-dimensional solutions best represented the data. The stimulus spaces for fat content and mouthcoating were visually similar to each other and provided reasonable separation of the samples. Instrumental measures helped to define the underlying dimensions of the stimulus space for fat content. Dimension 1 related to texture and included the contributions of viscosity, and fat particle size and number distribution; dimension 2 related to flavor perception. The sample with a moderate fat content (5%) and the highest concentration of added cream flavor (1%) was perceived to be similar to the 10% fat samples with added flavor. Thus, the added flavor provided the sensation of higher fat content. These data suggest that flavor plays an important role in the preception of fat in dairy foods. A psychophysical model of fat perception in dairy foods is proposed which includes the contribution of viscosity, fat particle size and number distribution, and volatile flavor perceptions.     

Induction of the PhoE porin by NaCI as the basis for salt-induced acid sensitivity in Escherichia coli

Z. LAZIM, T.J. HUMPHREY AND R.J. ROWBURY. 1996. Organisms grown in low salt broth (LSB) are acid resistant but become sensitive on growth for 30-60 min with 300 mmol 1⁻¹ added NaCl. Salt-induced acid sensitivity only occurs in relA⁺ strains and sensitization is abolished by glucose, this catabolite repression effect being reversed by cAMP. The finding that sensitization did not occur in a phoE strain but did occur in a phoE⁺ derivative of it suggested that the response might result from PhoE induction, since PhoE acts as the major outer membrane (OM) proton pore under most conditions. In agreement with this, low-salt broth (LSB)-grown cells of a chromosomally lac⁻ strain carrying pJP102 ( phoE-lacZ ) produced low levels of β-galactosidase but growth with added NaCl led to rapid and appreciable induction. Also, a phoA mutant carrying a phoE-phoA fusion produced little alkaline phosphatase after growth in LSB but much more in LSB with added NaCl. Increased β-galactosidase synthesis (in phoE-lacZ strains) in the presence of NaCl was abolished by glucose, this effect being reversible by cAMP, and there was more NaCl-induced synthesis of this enzyme in relA⁺ strains.
Accordingly, it appears that addition of NaCl to LSB leads to acid sensitivity because it induces synthesis of the OM proton pore PhoE.     

INHIBITION OF THYROXINE-INDUCED RESORPTION OF TADPOLE TAIL BY ADENOSINE 3', 5'-CYCLIC MONOPHOSPHATE

Small segments of tail of Bufo bufo japonicus tadpoles were cultured in medium containing thyroxine (T₄) and dibutyryl cyclic AMP (dbcAMP). Like prolactin, the cyclic nucleotide blocked T₄-induced shrinkage or tail pieces. Histological study of the segments after 4-days culture revealed that dbcAMP suppressed degenerative changes induced by T₄. The inhibitory effect of prolactin on T₄-induced tail regression was promoted by caffeine, an inhibitor of adenosine 3', 5'-cyclic monophosphate (cyclic AMP)-phosphodiesterase.
The effect of prolactin on the level of cyclic AMP in the tail was also studied in vivo . Sixty min after prolactin injection, the cyclic AMP level was 2–3 times the control value. Possible involvement of cyclic AMP in the action of prolactin, which blocks tail resorption induced by T₄, was discussed.     

RETENTION AND EXCHANGE OF POTASSIUM IN A SYNAPTOSOMAL FRACTION OF MOUSE BRAIN

Abstract— Myelin, synaptosomal and mitochondrial fractions obtained from homogenates of whole mouse brain contain K⁺ which can exchange with ⁴²K⁺ at 2º in 0·32 m -sucrose. The content and rates of exchange of K⁺ were greater at pH 8·2 than at 6·1. In the synaptosomal preparations, the rates of exchange and content of ⁴²K⁺ and K⁺ declined progressively with decreasing pH.
Of the total synaptosomal K⁺, 95 per cent could exchange with external ⁴²K⁺. At pH 7·5, 20 per cent of the K⁺ and 78 per cent of the Na⁺ appeared to reside in osmotically insensitive pools. Synaptosomal K⁺ at 2º was slowly displaced by NaCl (0·18 m ) and the rate of exchange between ⁴²K⁺ and K⁺ was retarded. KCI (0·18 m ) did not readily displace endogenous Na⁺. Synaptosomal K⁺ exchanged with exogenous K⁺ more rapidly than with exogenous Na⁺.
These observations have been discussed in terms of possible roles for ion exchange as the principal means by which K⁺ traverses the plasma membrane at 2º.     

THE EFFECT OF SALT REDUCTION ON TASTE PLEASANTNESS IN COOKED'BOLOGNA-TYPE'SAUSAGES

This study's objective was to study how much the salt (NaCl) content of cooked sausage can be reduced without violating the perceived taste pleasantness. The 34 assessors evaluated seven cooked sausages made with added salt concentrations of 1.05; 1.20; 1.35; 1.50; 1.65; 1.80 and 1.95%. A relative-to-standard scale was used for rating the saltiness and taste pleasantness. The saltiness and pleasantness intensity of different salt concentrations was rated against a reference sausage, which contained 1.5% added salt. A reference sample was also hidden among the samples. The assessors were able to rank sausages based on the saltiness into the right order. Based on taste pleasantness, there was no significant difference between the sausages made with 1.35; 1.50; 1.65; 1.80 or 1.95% added salt (p>0.05). Several differences were, however, detected among the saltiness levels. The results of this study suggest that it might be possible to reduce the salt content of cooked sausage to 1.35% added salt.     

Toxicity of Sodium and Chloride Ions to Rhizobium spp. in Broth and Peat Culture

The growth of a strain of Rhizobium trifolii and of R. meliloti was studied in broth and peat cultures to determine the relative toxicity of Na⁺ and Cl^-. The following salts were added in a range of concentrations: Na₂HPO₄ as a source of Na⁺, CaCl₂.2H₂O as a source of Cl^-, and NaCl. Disodium hydrogen orthophosphate affected the growth rate of both strains in broth culture but not in peat culture. Unexpectedly, calcium chloride was more toxic than NaCl in broth and peat culture. The toxicity of NaCl can be ascribed to the Cl^-. Rhizobium meliloti strains grew on 3·5% NaCl after adaptation during a long period. Rhizobia for soya bean and cowpea grew at 0·5% NaCl and those for clover and pea, at 1·0% NaCl.     

A precise potentiometric method for determination of algal activity in an open CO2 system

Abstract. The activity of the green alga Scenedesmus obliquus was studied in simplified nutrient solutions (20 mol m₋₃ NaNO₃, 20 mol m₋₃ NH₄C1, 20 mol m₋₃ NH₄NO₃, and 20 mol m₋₃ NaCl, respectively) at 25 °C. The experiments were performed under welldefined incident photon density fluxes ranging from 10 to 200 μmol m₂ s₋₁, Light-dependent changes in pH and alkalinity (A) were followed by means of a potentiometric method using a glass electrode. In the experiments, carbon dioxide with known partial pressure was bubbled through the algal suspension, and during dark periods ul intervals of 1 h, the solution was allowed to equilibrate with the gas phase. This technique was applied to calculate equilibrium values of pH and alkalinity at regular intervals during a 12-h period. Results obtained in NaNO₃, solution show a linear increase in A with time, at each level of illumination studied. After an initial drop, A also increases in NH₄NO₃, solution in a similar way to that in NaNO₃ solution. The change in A with time was also found to increase linearly with the photon density flux studied and no saturation level could be defined. In experiments in NaCl solution, no changes in A were registered while measurements in NH₄Cl solution showed a decrease in A with time.