PHENOTYPIC PLASTICITY INDUCED IN TRANSPLANT EXPERIMENTS IN A MUTUALISTIC ASSOCIATION BETWEEN THE RED ALGA JANIA ADHAERENS (RHODOPHYTA,CORALLINALES) AND THE SPONGE HALICLONA CAERULEA (PORIFERA: HAPLOSCLERIDA): MORPHOLOGICAL RESPONSES OF THE ALGA1

The association between the red macroalga Jania adhaerens J. V. Lamour. and the sponge Haliclona caerulea is the most successful life‐form between 2 and 4 m depth in Mazatlán Bay (Mexican Pacific). J. adhaerens colonizes the rocky intertidal area and penetrates into deeper areas only when it lives in association with H. caerulea. The aposymbiotic form of the sponge has not been reported in the bay. To understand the ecological success of this association, we examined the capacity of J. adhaerens to acclimate in Mazatlán Bay using transplant experiments. The transplanted aposymbiotic J. adhaerens did not survive the first 2 weeks; however, J. adhaerens when living in association with H. caerulea, acclimated easily to depth, showing no sign of mortality during the 103 d of the experiment. We conclude that the ability of J. adhaerens to colonize in deeper areas in this hydrodynamic environment may in part rely on the protection provided by the sponge to the algal canopy. Both species contribute to the shape of the associated form. Nevertheless, the morphological variation in the association appears to be dominated by the variation in J. adhaerens canopy to regulate pigment self‐shading under light‐limited conditions and/or tissue resistance under high hydrodynamics. Consequently, our results are consistent with light as the abiotic controlling factor, which regulates the lower depth distribution of the association in Mazatlán Bay, through limiting the growth rate of J. adhaerens. Hydrodynamics may determine the upper limit of the association by imposing high mass losses.     

Naloxone influences ultrasonic calling in young mice

The ultrasonic calls produced by three day old mice when separated from the nest mother and siblings increase in number when naloxone is injected.     

Resprouting in the Mediterranean‐type shrub Erica australis afffected by soil resource availability

Abstract. Soil resource availability may affect plant regeneration by resprouting in disturbed environments directly, by affecting plant growth rates, or indirectly by determining allocation to storage in the resprouting organs. Allocation to storage may be higher in stressful, low resource‐supply soils, but under such conditions plant growth rates may be lower. These factors could act in opposite directions leading to poorly known effects on resprouting. This paper analyses the role played by soil resources in the production and growth of resprouts after removal of above‐ground plant tissues in the Mediterranean shrub Erica australis. At 13 sites, differing in substrate, we cut the base of the stems of six plants of E. australis and allowed them to resprout and grow for two years. Soils were chemically analysed and plant water potential measured during the summer at all sites to characterize soil resource availability. We used stepwise regression analysis to determine the relationships between the resprouting response [mean site values of the number of resprouts (RN), maximum length (RML) and biomass (RB)] and soil nutrient content and plant water potential at each site. During the first two years of resprouting there were statistically significant differences among sites in the variables characterizing the resprouting response. RML was always different among sites and had little relationship with lignotuber area. RN was less different among sites and was always positively correlated with lignotuber area. RB was different among sites after the two years of growth. During the first months of resprouting, RN and RML were highly and positively related to the water status of the plant during summer. At later dates soil fertility variables came into play, explaining significant amounts of variance of the resprouting variables. Soil extractable cations content was the main variable accounting for RML and RB. Our results indicate that resprout growth of E. australis is positively affected by high water availability at the beginning of the resprouting response and negatively so by high soil extractable cation content at later periods. Some of these factors had previously shown to be related, with an opposite sign, to the development of a relatively larger lignotuber. Indeed, RML and RB measured in the second year of resprouting were significantly and negatively correlated with some indices of biomass allocation to the lignotuber at each site. This indicates that sites favouring allocation to the resprouting organ may not favour resprout growth.     

A phylogenetic analysis of species in the Bufo crucifer group (Anura: Bufonidae), based on indolealkylamines and proteins from skin secretions

This research tested the utility of two classes of skin secretion compounds to the phylogeny of the Bufo crucifer group. Skin secretions from specimens of nine populations of B. crucifer group were obtained and submitted to qualitative analysis. We observed a clear difference in the composition of the skin secretion molecules obtained from the species of Bufo studied. Fifty-nine molecules, 16 indolealkylamines and 43 proteins, were used as characters, and 39 of these were parsimonious informative. The tree topology of the skin secretion combined data showed areas of congruence and conflict when compared to an mtDNA phylogeny of the B. crucifer group. We used the Templeton test to evaluate the heterogeneity between the skin secretion and mtDNA data. Although not recommended, we performed a combined analysis with the two partitions. The skin secretion characters from the species of Bufo studied have phylogenetic signal. These data are indicative, at least as a preliminary study, of the phylogenetic relationships among the B. crucifer group taxa.     

The medial basal hypothalamus and luteinizing hormone release in the rat: Where are the LH-RH neurons responsible for tonic gonadotropin secretion?

Careful review of the literature demonstrates conflicting results concerning the ability of the deafferented medial basal hypothalamus to support gonadotropin release in the rat and thus one may question the existence of LH-RH neurons in the medial basal hypothalamus. The direct search for the LH-RH perikarya in the rat hypothalamus has not settled the question of whether these releasing hormone neurons are located in the medial basal hypothalamus. Most investigators do agree that following complete hypothalamic deafferentation there is a reduction of the immunoassayable LH-RH in the medial basal hypothalamus; however, these results do not necessarily prove that LH-RH originates outside the hypothalamus. It is argued that the completely deafferented medial basal hypothalamus may be so altered by the deafferentation procedure that it may be inadequate as a means to study neuroendocrine function.     

Purification of Pregnancy Zone Protein and Its Receptor Binding Domain from Human Plasma

A new significantly improved method for purification of pregnancy zone protein (PZP), α₂-macroglobulin (α₂M), and the C-terminal PZP receptor binding domain is presented. Several steps in an earlier procedure have been deleted, and modifications in the gradients in the DEAE step leave most of the contaminants bound to a DEAE-Sephacel gel. This procedure makes possible the rapid, simultaneous purification of both of these closely related unstable proteins in native form from human plasma, with no thiolester cleavage or formation of tetrameric PZP. The final preparations of both α₂M and PZP are pure as determined by nonreducing and reducing polyacrylamide gel electrophoresis following silver staining and no cross-contamination can be observed. The yield has been significantly improved and typically more than 500 mg PZP can be obtained from 1 liter pregnancy plasma. Furthermore, the stability of PZP at different temperatures on storage was studied. In liquid nitrogen PZP can be maintained in native dimeric form with intact thiolester for many years. The storage of native PZP with intact functional properties during and after purification is an obligatory prerequisite to elucidate the biological role of PZP. The receptor binding domain of PZP can be cleaved from the PZP–methylamine complex by papain and isolated from the other peptides by S-200 gel filtration. The cleavage site was determined and the C-terminal fragment was identified with several site-specific monoclonal antibodies against PZP.     

Substantivity of zinc salts used as rinsing solutions and their effect on the inhibition of Streptococcus mutans

The antimicrobial efficacy of zinc (Zn) salts (sulfate and acetate) against Streptococcus mutans (S. mutans) present in the oral cavity was tested in this study. The substantivity of Zn salts was assessed by determining the concentration of Zn in whole, unstimulated saliva and by measuring the magnitude of suppression of salivary S. mutans, 2h after rinsing. The concentration of Zn was measured by atomic absorption spectrometry (AAS) with electrothermal atomization (ET AAS) in saliva sampled before (basal) and 24h after mouth rinsing with different concentrations of Zn (0.1%, 0.5% and 1%) administrated as sulfate and acetate. The estimation of Zn levels in samples collected 30, 60, 90 and 120 min after rinsing was carried out by AAS with flame atomization (FAAS). Immediately after rinsing, the concentration of Zn in saliva sharply increased with respect to the baseline values (0.055+/-0.017 mg/L), followed by a sustained decrease, probably due to clearance of salivary flow or swallowing during sampling. A significant reduction (>87%) in the total mean S. mutans counts was found 2h after rinsing either with sulfate or acetate solutions, as evidence of the high substantivity and effectiveness of the Zn salts tested. A statistically significant inverse relationship (p<0.001 and the Pearson correlation coefficients between -34% and -50%) was found between Zn levels and the respective pH values measured in the samples collected 60 and 120 min after rinsing, sustaining the theory of bacterial glycolysis inhibition.     

N-Acetylsuccinimidylglutamate, a Cyclic Imide Form of the Peptide N-Acetylaspartylglutamate, Is Present in Low Micromolar Concentrations in Murine and Bovine CNS

Abstract: N -Acetylsuccinimidylglutamate [(asu)NAAG], a cyclic form of the peptide N -acetylaspartylglutamate (NAAG) in which the aspartyl residue is linked to glutamate via the α- and β-carboxylates, was identified and quantified by HPLC in the murine and bovine CNS. In the rat, the highest concentrations of (asu)NAAG were detected in the spinal cord (1.83 ± 0.15 pmol/mg of wet tissue weight) and brainstem (1.16 ± 0.08 pmol/mg wet weight), whereas the levels were below the limit of detection in cerebellum, hippocampus, and cerebral cortex. (Asu)NAAG was also detected in significant amounts in the superior colliculus and lateral genicutale nucleus (1.17 ± 0.05 and 0.82 ± 0.13 pmol/mg wet weight, respectively). Although the tissue content of (asu)NAAG was about three orders of magnitude lower than that of NAAG, levels of both peptides were positively correlated among different CNS regions ( r = 0.74, p < 0.003). In the rat spinal cord, (asu)NAAG levels progressively increased from week 2 to month 12 after birth. In bovine spinal cord, the contents of (asu)NAAG and NAAG were comparable in gray and white matter as well as in the dorsal and ventral horns. These results suggest that NAAG and (asu)-NAAG are closely related metabolically and raise the question of the physiological significance of such a cyclic peptide.     

Population dynamics of two small pelagic fish in the central-south area off Chile: delayed density-dependence and biological interaction

It is widely believed that environmental variability is the main cause for fluctuations in commercially exploited small pelagic fish populations around the world. Nevertheless, density-dependent factors also can drive population dynamics. In this paper, we analyzed thirteen years of a relative abundance index of two clupeoids fish populations coexisting in the central-south area off Chile, namely the common sardine, Strangomera bentincki, and anchovy, Engraulis ringens. We applied the classical diagnostic tools of time series analysis to the observed time-series. Also, the realized per capita population growth rate was studied with the aim of detecting the feedback structure that is characterizing the population dynamics of the two species. The analysis suggests that population fluctuations of the two species have an important density-dependent component, displaying first-order (direct density-dependent) and second-order (delayed density-dependent) simultaneously. The density-dependent component explained 70.5 and 55.6 % of the realized per capita population growth rate of common sardine and anchovy, respectively. The deterministic skeleton model showed an asymptotic convergence to equilibrium density. In presence of a stochastic environment, fluctuations were reproduced for the species showing a component of fluctuation with a period of 4 year. The intrinsic dynamics of each species is typical of interacting species resulting from trophic interactions. It is postulated that the second-order dynamics of S. bentincki and E. ringens in central-south Chile, may be the result from interactions with a specialist predator (the fishing fleet), interacting with exogenous environmental factors.