Orientation in the dark: brain circuits involved in the perception of electric signals in mormyrid electric fish.

Weakly electric fish produce electric signals with a specialised organ in their tail. In addition, they are electrosensitive and can perceive their self-generated signals (for electrolocation) and electric signals of other electric fishes (for electrocommunication). Mormyrids possess three types of peripheral electroreceptor organs, one used for electrocommunication and two types involved in electolocation. They are innervated by afferent fibres, which project to different zones in the electrosensory lateral line lobe (ELL) in the medulla. Brain circuits for electrolocation and electrocommunication are separated almost throughout the whole brain. Electrolocation pathways run from the ELL-cortex to the torus semicircularis of the midbrain and then via the valvula cerebelli towards the telencephalon. Pathways involved in electrocommunication run from the nucleus of the ELL to another part of the torus and from there through the isthmic granule nucleus to the valvula. In addition, a pathway via the preglomerular complex to the telencephalon might exist. In both the electrolocation and the electrocommunication circuits, prominent recurrent pathways are present.     

What is the role of cytokines in human colostrum?

No one has ever doubted that maternal milk, in comparison to formula milk, has a far superior nutritional value. Colostrum has a well acknowledge crucial value for the survival of the animal species that cannot receive immunoglobulins through the placenta. Until recently the presence of cytokines in colostrum was unsuspected but it has been now clarified that normally there are at least four cytokines, namely interleukin 1 and 6, tumor necrosis factor and interferon gamma, that may exert an important immunostimulatory role particularly on the oropharyngeal-associated lymphoid tissue. As a corollary, physiological concentration of cytokines administered per os may exert a useful adjuvant activity in aged or immunodeficient people.     

Multiple Bacteriocin Production by Leuconostoc mesenteroidesTA33a and Other Leuconostoc/Weissella Strains

Leuconostoc (Lc.) mesenteroides TA33a produced three bacteriocins with different inhibitory activity spectra. Bacteriocins were purified by adsorption/desorption from producer cells and reverse phase high-performance liquid chromatography. Leucocin C-TA33a, a novel bacteriocin with a predicted molecular mass of 4598 Da, inhibited Listeria and other lactic acid bacteria (LAB). Leucocin B-TA33a has a predicted molecular mass of 3466 Da, with activity against Leuconostoc/Weissella (W.) strains, and appears similar to mesenterocin 52B and dextranicin 24, while leucocin A-TA33a, which also inhibited Listeria and other LAB strains, is identical to leucocin A-UAL 187. A survey of other known bacteriocin-producing Leuconostoc/Weissella strains for the presence of the three different bacteriocins revealed that production of leucocin A-, B- and C-type bacteriocins was widespread. Lc. carnosum LA54a, W. paramesenteroides LA7a, and Lc. gelidum UAL 187-22 produced all three bacteriocins, whereas W. paramesenteroides OX and Lc. carnosum TA11a produced only leucocin A- and B-type bacteriocins. Received: 11 April 1997 / Accepted: 10 June 1997     

Ornithologische Notizen aus dem Ebrodelta

Zusammenfassung Im Ebrodelta ist, abgesehen von einigen Seen und Sümpfen, nur noch ein schmaler Küstenstreifen landwirtschaftlich ungenutzt. Hier hat sich ein Teil ursprünglichen Vogelreichtums erhalten, und hier wurde seit einigen Jahren eine Reihe faunistischer Erhebungen durchgeführt.Diese erbrachten mehrere erste Brutnachweise für Spanien oder die spanische Mittelmeerküste:Larus ridibundus, Sterna dougallii, St. sandvicensis, Haematopus ostralegus, Limosa limosa, Asio flammeus, Acrocephalus palustris. Als Rast- und Überwinterungsgebiet ist das Delta von großer Bedeutung, z. B. fürEgretta garzetta undPhoenicopterus ruber. Enge Beziehungen zur Camargue sind vielfach erkennbar, vielleicht sogar hinsichtlich der Ausbreitung vonLarus ridibundus undHaematopus ostralegus. Regelmäßige Wintervorkommen vonMarmaronetta angustirostris sind erwähnenswert.Es wird mit einigen bisher unbekannten Brutplätzen von Laro-Limicolen bekanntgemacht, von denen eine Kolonie vonSterna albifrons mit 300–400 Paaren besonders vermerkt sei. Für weitere Arten können Bestandsangaben gemacht werden.Dieses einzige, bedeutende Brut- und Rastgebiet zwischen Camargue und Coto Doñana ist in höchster Gefahr, durch intensivere landwirtschaftliche Nutzung und touristische Erschließung vernichtet zu werden.

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Resumen Datos ornitologicos sobre el Delta del Ebro. — Sin contar con charcas y marismas, el Delta del Ebro es una franja costera aun no explotada por la agricultura. Gracias a esto una numerosa variedad de aves ha podido mantenerse aprovechando las todavia persistentes condiciones orginarias del medio ambiente. Sobre estas aves se han venido acumulando en los ultimos años un buen acopio de observaciones.Se pudo constatar como nidificantes por primera vez en España o costas mediterranes a las siguientes especies:Larus ridibundus, Sterna dougalli, St. sandvicensis, Haematopus ostralegus, Limosa limosa, Asio flammeus, Acrocephalus palustris. Como lugar de invernada o refugio durante el paso el Delta del Ebro tiene un especial interes, por ejemplo paraEgretta garzetta yPhoenicopterus ruber. Se establecen algunas relaciones con la Camarga principalmente en cuanto a la expansión deLarus ridibundus yHaematopus ostralegus. Se mencionan invernadas regulares deMarmaronetta angustirostris. Se señalan algunos nuevos lugares de cria para Laro-Limicolas, merece destacarse el hallazgo de una colonia deSterna albifrons compuesta por unos 300–400 pares. Para otras especies se dan datos numerieos estimativos.El Delta del Ebro es un lugar unico y de gran importancia, situado entre la Camarga y el Coto de Doñana, que está hoy en peligro de desaparición debido a la colonización intensiva de la agricultura y a la creciente afluencia turistica.

     

Purification and properties of NADPH-dependent aldehyde reductase from human liver.

An aldehyde reductase (EC 1.1.1.2) from human liver has been purified to homogeneity. The enzyme is NADPH-dependent, prefers aromatic to aliphatic aldehydes as substrates, and is inhibited by barbiturates and hydantoins. The following physicochemical parameters were determined: molecular weight, 36,200; sedimentation coefficient, 2.9 S; Stokes radius, 2.65 nm; isoelectric point, pH 5.3; extinction coefficient at 280 nm, 54,300 M-1 cm-1. Results from polyacrylamide gel electrophoresis with and without sodium dodecyl sulfate, gel filtration, and ultracentrifugation suggest a monomeric structure. On molecule of NADPH binds to the enzyme causing a red shift of the coenzyme absorption maximum from 340 to 352 nm. The amino acid composition has been determined and a partial specific volume of 0.74 was computed from these data. An alpha-helicity of 7 and 18% was estimated from the ellipticities at 208 and 222 nm, respectively. Combination of the most reactive thiol group with p-mercuribenzoate does not cause loss of catalytic activity. Inactivation occurs when more than one thiol group is modified. The presence of NADPH or NADP+ prevents loss of activity by thiol modification. The comparison of structural features of aldehyde reductase with other monomeric and oligomeric dehydrogenases suggest similarities of aldehyde reductase with octopine dehydrogenase.     

Regulation of thyroid hormone metabolism in rat liver fractions

The nature of the conversion of thyroxine (T₄) to triiodothyronine (T₃) and reverse triiodothyronine (rT₃) was investigated in rat liver homogenate and microsomes. A 6-fold rise of T₃ and 2.5-fold rise of rT₃ levels determined by specific radioimmunoassays was observed over 6 h after the addition of T₄. An enzymic process is suggested that converts T₄ to T₃ and rT₃. For T₃ the optimal pH is 6 and for rT₃, 9.5. The converting activity for both T₃ and rT₃ is temperature dependent and can be suppressed by heat, H₂O₂, merthiolate and by 5-propyl-2-thiouracil. rT₃ and to a lesser degree iodide, were able to inhibit the production of T₃ in a dose related fashion. Therefore the pH dependendy, rT₃ and iodide may regulate the availability of T₃ or rT₃ depending on the metabolic requirements of thyroid hormones.     

Synthesis and processing of alpha-galactosidase A in human fibroblasts. Evidence for different mutations in Fabry disease

The synthesis and processing of the human lysosomal enzyme alpha-galactosidase A was examined in normal and Fabry fibroblasts. In normal cells, alpha-galactosidase A was synthesized as an Mr = 50,500 precursor, which contained phosphate groups in oligosaccharide chains cleavable by endoglucosaminidase H. The precursor was processed via ill-defined intermediates to a mature Mr 46,000 form. Processing was complete within 3-7 days after synthesis. In the presence of NH4Cl and in I-cell fibroblasts, the majority of newly synthesized alpha-galactosidase A was secreted as an Mr = 52,000 form. For comparison, the processing and stability of alpha-galactosidase A were examined in fibroblasts from five unrelated patients with Fabry disease, which is caused by deficient alpha-galactosidase A activity. In one cell line, synthesis of immunologically cross-reacting polypeptides was not detectable. In another, the synthesis, processing, and stability of alpha-galactosidase A was indistinguishable from that in normal fibroblasts. In a third Fabry cell line, the mutation retarded the maturation of alpha-galactosidase A. Finally, in two cell lines, alpha-galactosidase A polypeptides were synthesized that were rapidly degraded following delivery to lysosomes. These results clearly indicate that Fabry disease comprises a heterogeneous group of mutations affecting synthesis, processing, and stability of alpha-galactosidase A.     

The onset of the respiratory burst in human neutrophils. Real-time studies of H2O2 formation reveal a rapid agonist-induced transduction process

A real-time study of the initiation of the respiratory burst in human neutrophils was made. The cells were stimulated with fMet-Leu-Phe (fMLP) C5a, platelet-activating factor, leukotriene B4, phorbol myristate acetate (PMA), or ionomycin, and H2O2 production was determined by chemiluminescence. Identical average onset times (2.4 s) and closely comparable values for the apparent first-order rate constant (kapp) for the induction of NADPH-oxidase activity (0.21-0.29 s-1) were obtained following stimulation with fMLP, C5a, platelet-activating factor, or leukotriene B4, suggesting that different agonists act through a common transduction sequence. Much longer onset times and lower kapp values were obtained upon stimulation with PMA or ionomycin. Pretreatment with PMA consistently shortened the onset time of the neutrophil's responses to agonists by about 1 s. When H2O2 production was initiated with PMA, a subsequent stimulation with the agonist fMLP elicited an immediate response (onset time less than 0.2 s) which preceded further changes in fura-2-detected [Ca2+]i. The results are consistent with a mechanism in which agonist signals appear to be transduced by two sequences acting in concert--a rate-limiting one liberating Ca2+ and diacylglycerol and turning on the Ca2+/phospholipid-dependent enzyme protein kinase C, and an essentially instantaneous one which does not appear to require further changes in cytosolic Ca2+.     

The heat generated by yeast cultures with a mixed metabolism in the transition between respiration and fermentation

The heat generated by both batch and continuous cultures of the yeast K. fragilis was studied using a modified Bench Scale Calorimeter. Batch cultures were used to measure the heat dissipation rates and the heat yields during fully aerobic and completely anaerobic growth, whereas continuous cultures enabled, in addition, a quantitative study of heat dissipation rates during growth on mixed metabolism. In this case, the extent of fermentation versus respiration could be specified and controlled by varying the degree of oxygen limitation. The heat dissipated per unit biomass formed was highest for fully respirative catabolism and fell continuously to a much lower value typical of anaerobic cultures as the catabolism was shifted increasingly to the fermentative mode. The heat generated per mole of oxygen taken up stayed quite close to the fully aerobic value of 506 kJ mol(-1) even when a sizable fraction of the substrate available to catabolism was fermented. If the fraction of respiration in the metabolism is lowered beyond a certain threshold, the ratio of the heat generation to oxygen consumption starts to increase dramatically and finally tends to infinity for fully anaerobic growth. All experimental results were quantitatively analyzed and explained on the basis of a simple model which formally describes the cultures in terms of two parallel "chemical" reactions. In simple cases such as the one presented here, the model enables calculation of the whole stoichiometry of the culture from a single measured heat yield.