On the chemiluminescence in the oxidation of tetravalent uranium to the uranyl ion by dimethyldioxirane

The reaction of the tetravalent uranium [U(IV)] with dimethyldioxirane (DMD) in strongly acidic water–acetone solutions is accompanied by chemiluminescence (CL) in the visible (Vis) and infra‐red (IR) regions. At least three independent reaction pathways are involved in the U(IV)–DMD oxidation: the first entails the non‐chemiluminescent oxidation of U(IV) to the uranyl ion (UO₂²⁺); the second involves the catalytic decomposition of DMD by U(IV) to afford singlet oxygen, as manifested by its characteristic IR‐CL; and in the third process, slow Vis‐CL (510–540 nm) is emitted, following DMD consumption. Copyright © 2002 John Wiley & Sons, Ltd.     

Role of the Ca-pectates on the accumulation of heavy metals in the root apoplasm

In order to better understand the processes that regulate the accumulation in the apoplasm of heavy metals and their mobilization by the plant metabolites it is essential to study the mechanisms that regulate the interactions between metal ions and pectins. In such a context, the sorption of Cd(II), Zn(II), Cu(II) and Pb(II) from single and multi-metal solutions, by a Ca-polygalacturonate gel with a degree of esterification of 18.0 (PGAM₁) and 65.5% (PGAM₂) was studied in the 3.0–6.0 pH range in the presence of CaCl₂ 2.5 mM. The sorption of Cr(III) from single metal solution was also considered. The results show that the amount of each metal ion sorbed increases with increasing the initial metal ion concentration and pH. The data from the single metal solution tests show that at pH 6.0 the affinity of the metal ions towards the PGAM₁ matrix follows the order: Cr(III) > Cu(II) ? Pb(II) ? Zn(II) ? Cd(II). The simultaneous sorption of the bivalent metal ions by the PGAM₁ gels indicates that Pb(II) is selectively sorbed. The FT-IR spectra show that the carboxylate groups are mainly responsible for the metal ion coordination. The ability of PGAM₂ to accumulate Cr(III), Cu(II), and Pb(II) was lower than that found in the PGAM₁ systems whereas the sorption of Zn(II) and Cd(II) was negligible.     

Effects of the anion transport inhibitor,SITS, on the proximal straight tubule of the rabbit perfusedin vitro

Summary Conventional microelectrodes were used to study the effects of SITS (4-acetamido-4-isothiocyanostilbene-2,2-disulfonate) on the basolateral membrane potentialVbl of the superficial proximal straight tubule (PST) of the rabbit kidney perfusedin vitro. Addition of 0.1mm SITS to the bathing solution resulted in a slow and irreversible hyperpolarization ofVbl from –42.5±1.17 (37) mV to –77.3±0.83 (52) mV. The new steady-state potential was reached in 10 to 15 min and was accompanied by visible cell swelling. Associated with thisVbl hyperpolarization was: 1) an increased steady-state depolarization (from 6.2±0.77 (17) mV to 25.7±0.83 (29) mV) in response to increasing bath potassium concentration from 5 to 16.7mm (HK); 2) a decreased transient depolarization (from 19.8±1.88 (8) mV to 0.43±0.37 (8) mV) in response to decreasing bath bicarbonate concentration from 22 to 6.6mm at constant bath pH (L-HCO₃); and 3) inhibition of a depolarizing overshoot and a decreased steady-state depolarization (from 35.9±1.84 (12) mV to 4.7±1.37 (13) mV) in response to reducing bath sodium concentration from 144 to zero (0-Na). Sodium, chloride and NMDG (N-methyl-d-glucamine) were used as the substituting ions, respectively. These results are consistent with the presence of a coupled sodium-bicarbonate carrier in the basolateral membrane which is electrogenic and SITS inhibitable. Comparison of the time course of SITS effects on these ion-substitution responses suggests that the inhibition of the bicarbonate exit pathway(s) is the primary event and that the changes inVbl and in the steady-stateVbl responses to HK and 0-Na are secondary events which may be related to changes in intracellular composition and/or basolateral membrane properties.     

Predicting the Distribution of the Amphibian Pathogen Batrachochytrium dendrobatidis in the New World1

One application of ecological niche modeling is predicting suitable areas for the establishment of invasive species. Herein, I model the fundamental niche of the chytrid fungus Batrachochytrium dendrobatidis, a pathogen linked to amphibian declines on several continents. Niche models were generated with the Genetic Algorithm of Rule‐Set Prediction using point distribution data of the pathogen and digital maps of environmental variables integrated in a GIS environment. The distribution of regions suitable for B. dendrobatidis in the New World is extensive and includes significant portions of: (1) Sierra Madre Occidental pine‐oak forest; (2) Sonoran and Sinaloan dry forest; (3) Veracruz moist forest; (4) Central America east from the Isthmus of Tehuantepec; (5) Caribbean Islands; (6) temperate forest in Chile and western Argentina south of latitude 30°S; (7) Andes above 1000 m of altitude in Venezuela, Colombia, and Ecuador; (8) eastern slopes of the Andes in Peru and Bolivia; (9) Brazilian Atlantic forest; (10) Uruguay, Paraguay, and northeastern Argentina; (11) southwestern and Madeira‐Tapajós Amazonian tropical rainforests. The regions with the highest suitability for B. dendrobatidis include habitats that contain the world's most diverse amphibian faunas. Models were built with New World localities, but also showed strong predictability for B. dendrobatidis localities in the Old World. Out of a total of 59 reported Old World localities for B. dendrobatidis, 56 occurred within regions with high predicted suitability. I also present analyses of the environmental envelope of B. dendrobatidis and discuss the implications of the results for the conservation of amphibians in the neotropics.     

Mixed municipal waste management in the Czech Republic from the point of view of the LCA method

Purpose  

This paper presents the results of a life-cycle assessment (LCA) study for integrated systems (IS) of mixed municipal waste (MMW) management in the Czech Republic. The seven IS categories assessed were: (a) incineration with slag recovery, (b) incineration without slag recovery, (c) landfills with incineration of the landfill gas by flaring, (d) landfills with recovery of the landfill gas, (e) mechanical–biological treatment (MBT) with aerobic treatment, (f) MBT biodrying with co-incineration of refuse-derived fuel, and (g) MBT biodrying with incineration of refuse-derived fuel from a monosource.     

Dioptrics of the facet lenses in the dorsal rim area of the cricket Gryllus bimaculatus

1. The optics of the corneal facet lenses from the dorsal rim area (DRA) and from the dorso-lateral areas (DA) of the compound eye of the cricket Gryllus bimaculatus were studied.
2. The DRA of the cricket eye contains quite normally shaped facet lenses. The diameter of the facet lens in the DA is 2-fold larger compared to that in the DRA. The radius of curvature of the front surface is distinctly less in the DA facet lenses, as the surface of the facet lenses in the DRA are virtually flat.
3. The averaged axial refractive index of the facet lenses of Gryllus bimaculatus, measured by interference microscopy, was 1.496 ± 0.008 (n = 42) in the DRA and 1.469 ± 0.004 (n = 39) in the DA. The geometrical thickness of the lenses was calculated to be 77 ± 3 μm (n = 42) in the DRA and 56 ± 1 μm (n = 39) in the DA.
4. Analysis of the diffraction pattern obtained with a point light source revealed distinct focusing properties of both the DRA and the DA facet lenses; striking Airy-like diffraction patterns were obtained in both cases.
5. Focal distances measured directly at the backfocal plane were 40 ± 8 μm (n = 84) in the DRA of all the animals studied, and 60–90 μm (n = 62) in DA depending on the animal. Analysis of the diffraction of the point light source yielded very similar focal distances: 40 ± 5 μm (n = 10) in DRA and 81 ± 8 μm (n = 11) in DA. In the DRA, focal distance of the facet lenses was smaller than the cone length, 58 ± 3 μm (n = 9) while in the DA the focal distance matched the effective cone length, 71 ± 5 μm (n = 16).

     

Old and new hypotheses about the homology of the compound bones from the cheek and otico-occipital regions of the anuran skull

We studied the larval development of compound bones from the otico-occipital and cheek regions in species of the neobatrachian genera Batrachyla, Hylorina, Leptodactylus, Odontophrynus and Pleurodema. Comparisons were made using a set of Ambystoma spp. (Caudata) and Ceratophrys ornata (Anura; Ceratophryidae) larvae. As suggested by previous studies, we verified the compound nature of the exoccipital (two centers, anurans only), frontoparietal (one center, most anurans and Ambystoma; three centers, some anurans), and squamosal (two centers, all anurans and Ambystoma) bones. We discuss old and new homology hypotheses for each of the compound bone centers in the context of the most widely accepted scenario of lissamphibian origins and relationships, i.e., monophyletic Lissamphibia that includes the clade Batrachia (Caudata + Anura) and the most divergent Gymnophiona. Our findings have a direct impact on our understanding of the composition of the skull in Lissamphibia. We recognized the presence of the following bones: (i) opisthotic (fused to the exoccipital) and tabular (fused to the squamosal) in Batrachia (Anura + Caudata) and (ii) supratemporal (fused to the parietal portion of the frontoparietal) in Anura. Separate centers of the parietal were found only in Pleurodema.     

Message from the President of the Society

The circadian rhythm of locomotor activity of the field mouse Mus booduga was studied and single animal phase response curves (PRCs) (n = 8) were constructed for 15-min daylight pulses of 1000 lux intensity. The light pulses, presented at different phases of the circadian cycle, evoked advancing and delaying phase shifts (ΔPHs) depending on the circadian time (CT) of light pulse application. ΔPHs by light pulses applied at the same phase are strongly correlated with the animals' circadian period (τ). The results indicate a significant correlation between (i) τ and the area under the advance zone of the PRC (A) (r = +0.72, p > 0.05), (ii) τ and the area under the delay zone of the PRC (D) (r = -0.98, p > 0.00001), (iii) τ and the difference between the area under delay and advance zone of PRC (D-A) (r = -0.97, p > 0.00001), and (iv) between τ and ΔpHs (at various phases of the circadian cycle) and further suggest that the waveform and time course of PRC depend on the animals' endogenous period (τ). (Chronobiology International, 13(6), 401–409, 1996)     

Methylmercury's chemistry: From the environment to the mammalian brain

Methylmercury is a neurotoxicant that is found in fish and rice. MeHg's toxicity is mediated by blockage of -SH and -SeH groups of proteins. However, the identification of MeHg's targets is elusive. Here we focus on the chemistry of MeHg in the abiotic and biotic environment. The toxicological chemistry of MeHg is complex in metazoans, but at the atomic level it can be explained by exchange reactions of MeHg bound to –S(e)H with another free –S(e)H group (R¹S(e)-HgMe + R²-S(e)H ↔ R¹S(e)H + R²-S(e)-HgMe). This reaction was first studied by professor Rabenstein and here it is referred as the “Rabenstein's Reaction”. The absorption, distribution, and excretion of MeHg in the environment and in the body of animals will be dictated by Rabenstein's reactions. The affinity of MeHg by thiol and selenol groups and the exchange of MeHg by Rabenstein's Reaction (which is a diffusion controlled reaction) dictates MeHg's neurotoxicity. However, it is important to emphasize that the MeHg exchange reaction velocity with different types of thiol- and selenol-containing proteins will also depend on protein-specific structural and thermodynamical factors. New experimental approaches and detailed studies about the Rabenstein's reaction between MeHg with low molecular mass thiol (LMM-SH) molecules (cysteine, GSH, acetyl-CoA, lipoate, homocysteine) with abundant high molecular mass thiol (HMM-SH) molecules (albumin, hemoglobin) and HMM-SeH (GPxs, Selenoprotein P, TrxR1-3) are needed. The study of MeHg migration from –S(e)-Hg- bonds to free –S(e)H groups (Rabenstein's Reaction) in pure chemical systems and neural cells (with special emphasis to the LMM-SH and HMM-S(e)H molecules cited above) will be critical to developing realistic constants to be used in silico models that will predict the distribution of MeHg in humans.     

Control of the activity of plant plasma membrane MgATPase by the viscosity of the aqueous phase

The activity of plant plasma membrane (PM) MgATPase (EC 3. 6. 1. 35) was studied in PM vesicles purified from spring wheat (Triticum aestivum L. cv. Drabant) roots, winter wheat (Triticum aestivum L. cv. Martonvásári-8) roots, and soybean (Glycine max L. cv. Williams) hypocotyls by aqueous polymer two-phase partitioning. MgATPase from spring wheat roots was assayed at 23°C (a) in the absence and presence of Triton X-100, (b) in the presence of either 1 mM or 3 mM MgATP^2?, and in the presence of increasing concentration of sucrose from 10 mM upto 1. 2 M. Activity of MgATPase in PM vesicles from winter wheat roots was measured at 21°C at sucrose concentrations of 15 mM–1. 1 M in the presence of 3 mM MgATP^2? and absence of Triton X-100 only. MgATPase activity from soybean hypocotyls was studied (a) in the absence and presence of Triton X-100, (b) both at 21 and 31°C, in the presence of 3 mM MgATP^2? and varying concentrations of sucrose between 10 mM and 1. 1 M. In all cases, independently of the assay conditions and the source of PM, the MgATPase activity decreased with increasing sucrose concentration. Latency of the MgATPase activity depended only slightly on the concentration of sucrose. The Q₁₀ value for the MgATPase activity from soybean hypocotyls (and thereby the Arrhenius activation energy of the enzymatic reaction) was independent of the sucrose concentration and of the presence of Triton X-100. At optimal assay conditions, the ATP-hydrolyzing activity of plant PM MgATPase (v) was inversely proportional to the m-th power of the viscosity of aqueous phase (η) as predicted by the modified Kramers'theory of enzymatic catalysis: v ∝ (1/η)^m, where m is an empirical parameter between 0 and 1. For the activity of MgATPase in the three species studied, m varied between 0. 5 and 1. 1 in good agreement with the theory. We thus conclude that (a) the activity of integral membrane enzyme-proteins may be controlled not only by the property(ies) of the membrane lipid phase but also by the viscosity of the aqueous phase in the vicinity of such enzymes, and (b) the determination of vesicle sidedness based on enzyme latency may need a minor revision. Our interpretation is in agreement with the molecular dynamics approach of enzymatic catalysis worked out for soluble enzymes.     

Changes in the activities of the protoheme-synthesizing system during the growth of yeast under different conditions.

The levels of some enzymatic activities involved in protoheme synthesis have been measured in subcellular fractions obtained at different stages of the growth of the yeast Saccharomyces cerevisiae grown anaerobically and aerobically with glucose (50 or 6 g/ liter), and ethanol (20 g/liter) as the carbon source. The degree of repression of the respiratory system is estimated by the respiratory capacity of whole cells, by the activities of succinate-cytochrome c reductase and cytochrome c oxidase of the mitochondrial particles, and by the cytochrome spectra. The results show that (i) the more porphyrins (cytochromes) that are synthesized by the cells, the lower is the specific activity of δ-aminolevulinic acid (ALA) synthetase and the higher is the specific activity of ALA dehydratase, the activity ratio ALA synthetase/ALA dehydratase decreasing at least 10-fold compared to the repressed cells; (ii) the amount of intracellular ALA found under all conditions tested (from 0.05 to 1.5 mm in the cell sap) correlates well with the measured ALA synthetase activity; its presence argues against a rate-limiting function for ALA synthetase and rather favors such a role for the ALA dehydratase in the formation of heme in yeast; (iii) the rate of porphyrin synthesis measured in vitro is higher in the case of cells with high cytochrome contents; and (iv) the specific activities of succinyl CoA synthetase and protoheme ferrolyase are always present in nonlimiting amounts. Some experiments are described showing that the values of the activities which are calculated from these in situ and in vivo experiments compare well with the values measured in vitro in the acellular extracts. The results concerning the enzymatic activities, together with (i) the excretion of coproporphyrin(ogen) and the accumulation of protoporphyrin + Zn-protoporphyrin in anaerobiosis, (ii) the presence of protoporpho(di)methene (P503) in anaerobic and repressed cells, and (iii) the presence of intracellular ALA under all growth conditions, are discussed in terms of possible control(s) of heme synthesis in yeast.     

Deoxynivalenol affects the composition of the basement membrane proteins and influences en route the migration of CD16+ cells into the intestinal epithelium

The numerous pores in the basement membrane (BM) of the intestinal villi are essential for the communication of enterocytes with cells in the lamina propria, an important mechanism for the induction of intestinal immune responses. The intestinal epithelial barrier is affected by the mycotoxin deoxynivalenol (DON) from both the apical (luminal) and basolateral (serosal) side. The pig is the most susceptible species to the anorectic and immune-modulating effects of DON, which is most prevalent in crops. We analysed in pigs the effect of DON-contaminated feed on the composition and perforation of the BM and the presence of CD16⁺ cells or their dendrites in the epithelium. In addition to in vivo experiments, in vitro studies were carried out. Using microarray analyses, the effects of DON on IPEC-J2 cells were studied with the focus on the BM. Our in vivo results showed in the control pigs: (1) a significant increased pore number (p?≤?0.001) in the jejunum in comparison to ileum, (2) no difference in the pore size, and (3) comparable frequency of intraepithelial CD16⁺ cells/dendrites in the jejunum and ileum. There was a marked trend that DON feeding increases: (1) the pore number in jejunum, and (2) the number of CD16⁺ cells/dendrites in the epithelium (Tukey–Kramer; p?=?0.055 and p?=?0.067, respectively). The in vivo results were extended with microarray analyses of epithelial cell (IPEC-J2 cells). The down-regulation of genes like syndecan, fibulin 6 and BM-40 was observed. These proteins are important factors in the BM composition and in formation of pores. Our results provide evidence that already low basolateral concentrations of DON (50 ng/mL) influence the production of the BM protein laminin by epithelial cells. Thus, DON affects the composition of the BM.     

Asymmetries of the long bones of the limbs and of the clavicles in Indian Lorises

Eighteen adult skeletons ofLoris tardigradus lydekkerianus (4 males and 4 females) andNycticebus coucang (6 males and 4 females) have been studied for the asymmetries in the long bones of the limbs and of the clavicles. The bones of the upper extremity are longer in the right inLoris andNycticebus. Asymmetry favours the right side more inLoris than inNycticebus regarding the thigh bone and the total length of the lower extremity. Lorises do not essentially differ from the other primates including man, regarding the asymmetries of the lower extremities as they do in regard to the asymmetries of the upper extremities.Averages of the percentage asymmetries are higher in females than in males. Cases of symmetry are rarer in clavicles (0%) than in the other bones of the upper and lower extremities ofLoris andNycticebus but they do favour radius inNycticebus (45%) alone. There are no significant sex differences in the 2 series in the distribution of the asymmetries.The average of the degrees in which the lengths of the corresponding limb bones are unequal on the 2 sides of the body are approximately the same inLoris (0.78),Hylobatidae (0.70) and the great apes (0.72) with regard to the upper extremities. In the lower extremities, however, these degrees including those in man (0.63) and the macaque (0.61), excepting inHylobatidae (0.86) are practically the same as inNycticebus (0.61) while much higher than those inLoris (0.43).This investigation forms a part of the main research programme based on the anatomical and metrical data, on the Indian Lorises, conducted under the aegis of the Council of Scientific and Industrial Research, New Delhi, during the years 1962–65.This paper was presented before the section of Anthropology and Archaeology of the Indian Science Congress Association at its 54th annual session held at Hyderabad in January 3–9, 1967.     

A carboxylic residue at the high-affinity, Mn-binding site participates in the binding of iron cations that block the site

The role of carboxylic residues at the high-affinity, Mn-binding site in the ligation of iron cations blocking the site [Biochemistry 41 (2000) 5854] was studied, using a method developed to extract the iron cations blocking the site. We found that specifically bound Fe(III) cations can be extracted with citrate buffer at pH 3.0. Furthermore, citrate can also prevent the photooxidation of Fe(II) cations by Y_Z. Participation of a COOH group(s) in the ligation of Fe(III) at the high-affinity site was investigated using 1-ethyl-3-[(3-dimethylamino)propyl] carbodiimide (EDC), a chemical modifier of carboxylic amino acid residues. Modification of the COOH groups inhibits the light-induced oxidation of exogenous Mn(II) cations by Mn-depleted photosystem II (PSII[−Mn]) membranes. The rate of Mn(II) oxidation saturates at ≥10 μM in PSII(−Mn) membranes and ≥500 μM in EDC-treated PSII (−Mn) samples. Intact PSII(−Mn) membranes have only one site for Mn(II) oxidation via Y_Z (dissociation constant, K_d = 0.64 μM), while EDC-treated PSII(−Mn) samples have two sites (K_d = 1.52 and 22 μM; the latter is the low-affinity site). When PSII(−Mn) membranes were incubated with Fe(II) before modifier treatment (to block the high-affinity site) and the blocking iron cations were extracted with citrate (pH 3.0) after modification, the membranes contained only one site (K_d = 2.3 μM) for exogenous Mn(II) oxidation by Y_Z radical. In this case, the rate of electron donation via Y_Z saturated at a Mn(II) concentration ≥15 μM. These results indicate that the carboxylic residue participating in Mn(II) coordination and the binding of oxidized manganese cations at the HA_Z site is protected from the action of the modifier by the iron cations blocking the HA_Z site. We concluded that the carboxylic residue (D1 Asp-170) participating in the coordination of the manganese cation at the HA_Z site (Mn4 in the tetranuclear manganese cluster [Science 303 (2004) 1831]) is also involved in the ligation of the Fe cation(s) blocking the high-affinity Mn-binding site.     

Distribution of living planktonic foraminifera in the Ross Sea and the Pacific sector of the Southern Ocean (Antarctica)

In order to determine the factors controlling the distribution of planktonic foraminifera as a proxy for reconstruction of paleoenvironments, we present data on live assemblages collected in the Southern Ocean. Plankton tows and hydrographic measurements were taken in the upper 400 m of the water column at different sites in the Ross Sea (site B) and at the Polar Front of the Pacific Ocean (site O) during austral summers from 1998 to 2003.Based on qualitative micropaleontological observations we discriminated between Neogloboquadrina pachyderma dextral (dex) and N. pachyderma sinistral (sin). In addition for N. pachyderma (sin) we distinguished four morphs: the first one (1) has a thickened test and depressed sutures; the second morph (2) is represented by specimens characterized by a subspheric and heavily encrusted test; the third morph (3) has a thin and lobate walled test; the fourth one (4) represent the juvenile stage of N. pachyderma (sin) and is characterized by a smaller average size.The microfauna collected in the Ross Sea (site B) is characterized by the dominance of N. pachyderma (sin) (morphs 1 and 2), whereas low occurrences of Turborotalia quinqueloba, N. pachyderma (dex) and Neogloboquadrina dutertrei were noted in the first 50 m of the water column. The water column at this station is characterized by a marked and shallow stratification and a marked thermocline during the sampling season.At the ocean station (site O), the assemblage shows increasing diversification: T. quinqueloba, G. bulloides, N. pachyderma (dex) and few specimens of Globigerinita uvula characterize the planktonic microfauna. There is a predominance of non-encrusted morphs and juvenile specimens (3 and 4). At this station the mixed surface layer is deeper than in the Ross Sea (60–70 m), the pycnocline and the thermocline less marked.The depth and the intensity of the Deep Chlorophyll Maximum (DCM) influence foraminiferal distribution: N. pachyderma (sin) shows abundance peaks at or just below the DCM while G. bulloides peaks above the DCM. Coiling direction of N. pachyderma seems to be not controlled exclusively by Sea Surface Temperature (SST): probably the two coiling types are genetically different.Results document that diversity of planktonic foraminifera, number of specimens and variations in test morphology are related to regional differences in water properties (temperature, salinity, and DCM depth).     

Depolarization exposes the voltage sensor of the sodium channels to the extracellular region

Summary Two domains of Na channels were mapped with site-specific antibodies raised in rabbit against synthetic peptides corresponding to a part of the voltage sensor of internal repeat 1C ₁ ⁺ (amino acids 210–223) and to a region designated dipole (amino acids 1690–1699) of eel electroplax sodium channels. The antibodies bind to their respective domains in both purified and membrane-bound channels and immunoprecipitate the channels from eel electroplax and rat brain synaptosomes.Anti-C ₁ ⁺ depresses the action potential of rat sciatic nerve in a concentration-dependent way. It binds to the external side of rat brain synaptosomal vesicle, and its binding is potentiated by depolarization. Anti-dipole binds to the inner side of the vesicle, and the binding is inhibited by depolarization.We are most grateful to Dr. M.T. Tosteson (Harvard Medical School) for providing us with samples of the S₄IV peptides. We wish to express our gratitude to Drs. D. Gordon (Hebrew University) and A. Safran (The Weizmann Institute) for helping in the immunoprecipitation procedure, to Drs. H. Rahamimoff (Hebrew University) and A. Barzilai (Columbia University) for advising us with the vesicle experiments, to Drs. D. Kassel and M. Gavish (Technion) for many fruitful discussions, and to Dr. Y. Palti (Technion) for discussions of electric field and suggesting the dipole peptide. This work was supported by a basic research fund (BRF) of The Israel Academy of Sciences #430.87 (H.M. and G.S.), a BSF Grant #84-00367 (H.M.) and The Henry Gutwirt Fund for the Promotion of Research-Technion VPR Fund #184-0093 (H.M.).     

Involvement of the neurointermediate lobe of the pituitary gland in the secretion of prolactin and luteinizing hormone in the rat

The relationship between prolactin (PRL) secretion and the neurointermediate lobe (NIL) of the pituitary gland was investigated. Plasma PRL concentrations in rats bearing anterior pituitaries autografted with or without the NIL to the renal capsule were elevated to equal extents at 1 through 6 weeks after surgery (p > 0.10). PRL levels in ovariectomized rats in which the NIL had been removed surgically (NIL-X) or only visualized (NIL-C) were 3–7 ng/ml 4, 7, and 28 days after surgery (p > 0.10); however, they were slightly higher in NIL-X $\text{vs.}$ NIL-C rats 14 days after surgery (p < 0.05). Plasma luteinizing hormone (LH) concentrations in NIL-C rats increased by 36% from 2 to 4 weeks after surgery (p < 0.05); this increase was not detected in NIL-X rats. PRL and LH surges were induced by estradiol implants in ovariectomized NIL-X and NIL-C rats; the profiles of the PRL surges were superimposable, although the magnitude of the LH surge was only 50% that in NIL-C rats (p < 0.05). These results cast doubt on the importance of the NIL in the regulation of PRL secretion either $\text{via}$ secreting hypophysiotropic hormones or $\text{via}$ conducting anterior pituitary hormones directly to the median eminence. However, the NIL may have a physiologically important role in the regulation of LH secretion.     

Effects of the multiple stressors high temperature and reduced salinity on the photosynthesis of the hermatypic coral Galaxea fascicularis

This study investigates the physiological responses in the hermatypic coral Galaxea fascicularis exposed to salinity stress (from 37 ppt to 15 ppt) for 12 h, combined effects of reduced salinity (from 37 ppt to 20 ppt) and two temperatures (26 °C and 32 °C) for 12 h and combined effects of reduced salinity (from 37 ppt to 25 ppt) and two temperatures (26 °C and 29.5 °C) for 10 d. The results demonstrate that the coral is tolerant to 12 h exposure to extremely low salinity (15 ppt). The study also shows that combined effects of temperature and low salinity aggravate the damage on the photosynthesis of the symbiotic dinoflagellates in 12 h exposure to 20 ppt sea water. This study suggests that high temperature (29.5 °C) aggravates the damage of trivially low salinity (30 ppt) on the holobiont (the coral and its symbiotic dinoflagellates) in 10 d exposure. However, high temperature (29.5 °C) may have an antagonistic effect between temperature and low salinity (25 ppt) on metabolism of the holobiont. Based on the above results, we suggest that (1) the true mechanism of corals exposed to combined effects of low salinity and high temperature is complicated. This calls for more studies on different corals. Future studies should aim at investigating long-term low-level stress in order to simulate in situ conditions more accurately; (2) when corals exposed to extremely severe combined stressors for short-term or trivially severe stressors for relative long-term, the combined effects of two stressors (such as low salinity and high temperature) may be negative, otherwise, the effects may be additive.     

Effect of Precursors on the Synthesis of Catecholamines and on Neurotransmission in the Superior Cervical Ganglion of the Rat

Abstract: Male Sprague-Dawley rats (325–350 g) were anesthetized with urethane (1.5 g/kg i.p.) and treated with physiological saline, Aspartame (APM; 552 μmol/kg), or tyrosine (Tyr; 552 μmol/kg). Ganglionic transmission and the synthesis of dopamine (DA) and norepinephrine (NE) were measured in the superior cervical ganglion (SCG) following electrical stimulation of the cervical sympathetic trunk (CST). When the CST was stimulated with single pulses, neither APM nor Tyr affected the synthesis of NE or DA. However, in response to low- (5 Hz, 20 s) and high- (20 Hz, 20 s) frequency pulses, the metabolism of DA was increased (p > 0.05), but to the same extent after saline, APM, or Tyr. In rats stimulated with similar low- and high-frequency pulses, the synthesis of NE was increased significantly (p > 0.05) after Tyr, but not after APM or saline. In saline-treated controls, ganglionic transmission was not changed in response to single pulses, or low- or high-frequency stimulation. However, after treatment with APM, ganglionic transmission was depressed significantly (p > 0.01) in response to high-frequency stimulation (single: 0.46 ± 0.09 mV; low: 0.39 ± 0.07 mV; high: 0.27 ± 0.07 mV). After treatment with Tyr, ganglionic transmission was depressed significantly (p > 0.05) in response to both low- and high-frequency stimulation (single: 0.44 ± 0.04 mV; low: 0.22 ±0.12 mV; high: 0.26 ± 0.07 mV). In the nonstimulated SCG, l-3,4-dihydroxyphenylalanine (25 mg/kg) caused a rapid, significant (p > 0.01) increase in the synthesis and metabolism of DA, but not of NE. Treatment with nialamide (200 mg/kg i.p.) followed by electrical stimulation (15 Hz, 15 min) of the CST caused a significant (p > 0.05) increase of both NE and DA in the stimulated SCG. It is concluded that there are both similarities and differences in the regulation of the synthesis of NE and in the modulation of ganglionic transmission after the administration of the precursors APM and Tyr. The results indicate that caution is needed in comparing the neurochemical and neurophysiological effects of different catecholamine precursors.