Ammoniten mit Kieferapparat und Radula aus Lias-Geschieben

Jaws and radula have been found in two adult microconch specimens of the Liassic ammonite speciesEleganticeras elegantulum (Young & Bird, 1828) from glacial drift boulders near Hamburg. They are more similar to those of recent dibranchiates than ofNautilus, the radula having seven longitudinal rows of teeth instead of thirteen in recentNautilus. Since bothOwens classification of the cephalopods into Dibranchiata and Tetrabranchiata according to the number of gills (which cannot be observed in fossil cephalopods) andSchwarz’ division into Ecto- and Endocochlia according to the (assumed) relative position of body and shell are rather unfortunate, the radula is suggested as a sound basis of classification. It is acceptable to paleo- as well as to neozoologists. As yet, the known evidence is sufficient for a twofold division only: Class Cephalopoda Subclass Lateradulata: Nautiloidea Subclass Angusteradulata: Ammonoidea Coleoidea     

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In Vivo Substitution of Choline for Sodium Evokes a Selective Osmoinsensitive Increase of Extracellular Taurine in the Rat Hippocampus

Recent investigations have demonstrated that taurine and phosphoethanolamine (PEA) are the amino acids most sensitive to microdialysis-perfusion with reduced concentrations of NaCl. The aim of the present work was to assess the importance of Na+ deficiency in evoking this response. Further, the previously described selectivity of replacement of Cl- with acetate with respect to amino acid release was reinvestigated. The hippocampus of urethane-anesthetized rats was dialyzed with Krebs-Ringer bicarbonate buffer, and amino acid concentrations of the perfusate were determined. Choline chloride was then stepwise substituted for NaCl, and, in some cases, mannitol (122 mM) was included in low sodium-containing media. In other experiments, NaCl was replaced with sodium acetate. The dialysate levels of taurine increased selectively in response to Na+ substitution. The elevation of taurine was linearly related to the increase in choline chloride, and maximal levels amounted to 335% of basal levels. The increase in extracellular taurine was not inhibited by perfusion with medium made hyperosmotic with mannitol. Replacement of Cl- with acetate stimulated the release of taurine to 652% of resting levels. In addition, PEA levels increased to 250% of control concentration. Other amino acids were unaffected by Cl- substitution. The results show that taurine transport is considerably more sensitive to Na+ depletion than glutamate transport, which also is known to be Na+ dependent. The taurine increase evoked by low Na+ is not caused by cellular swelling as it was unaffected by hyperosmolar medium. Finally, substitution of acetate for Cl- causes a specific elevation of extracellular taurine and PEA, possibly as a result of cytotoxic edema.     

Crystallographic data for soybean hydrophobic protein

The soybean hydrophobic protein belongs to a family of proteins that contains a number of storage and phospholipid binding proteins. Its function is not known, but its overall hydrophobic nature is typical of many membrane proteins of similar size. The molecular weight is 8.3 x 10(3), and it crystallizes in the space group P2(1)2(1)2(1), with a = 52.01 A, b = 43.50 A and c = 28.80 A. The crystals diffract to 1.8 A resolution, and are thus suitable for X-ray structural studies.     

Differential effects of phencyclidine (PCP) and ketamine on mesocortical and mesostriatal dopamine release in vivo

The interactions of phencyclidine (PCP) with the mesocortical dopaminergic system were of interest because of the putative role of this pathway in the etiology of schizophrenia. In the present investigation we examined the effects of PCP, and PCP-receptor agonist, ketamine, on dopamine (DA) release by measuring the levels of 3-methoxytyramine (3-MT), the only DA metabolite which is a reliable indicator of DA release in vivo. PCP increased DA release in the amygdala, pyriform and prefrontal cortices, while ketamine was less potent than PCP in this respect. In contrast to the changes in DA release in the cortical regions, ketamine decreased DA release in striatum, while PCP did not change DA release.     

Suramin-treated HT29-D4 cells grown in the presence of glucose in permeable culture chambers form electrically active epithelial monolayers. A comparative study with HT29-D4 cells grown in the absence of glucose

The clonal cell line HT29-D4 is able to differentiate by two different ways: i) by replacing glucose by galactose in the culture medium; ii) by addition of suramin (a drug known to interfere with the growth promoting activity of growth factors) in the medium. In both cases the transition in the organization of the cell monolayer occurred without cell loss. The two ways (i.e., glucose starvation or suramin addition) lead to polarized cells which generate electrically active cell monolayers (Fantini et al., Biol. Cell 65, 163-169 (1989) and this paper). Yet several important differences can be observed at the morphological or at the electrophysiological levels. 1) The suramin-treated cells (HT29-D4-S cells) organized into monolayers of high (40-50 microns) columnar cells while glucose-starved cells (HT29-D4-Gal cells) were rather cuboidal (20-25 microns). 2) HT29-D4-S cells were highly polarized; the nucleus was rejected at the basal side of the cell and lysosomes in the upper part of the cytoplasm. Numerous lipid-like droplets surrounded with glycogen were observed underneath the nucleus. HT29-D4-Gal cells never presented such a degree of organization. 3) The transepithelial resistance and the potential difference of HT29-D4-S monolayers reached values significantly higher than those for HT29-D4-Gal monolayers, reflecting a higher degree of organization. Specific proteins such as sucrase-isomaltase, alkaline phosphatase and carcinoembryonic antigen were localized exclusively on the apical membrane while human lymphocyte antigen (HLA) class I molecules were restricted to the basolateral membrane for both HT29-D4-S and HT29-D4-Gal cells. The present data demonstrate that the same cells can generate a different degree of cellular organization according to the experimental conditions of cell growth, the most elaborate state of differentiation being obtained in the presence of suramin.     

Design of a bubble-swawm bioreactor for animal cell culture

A stationary bubble-swarm has been used to aerate a mammalian cell culture bioreactor with an extremely low gas flow rate. Prolonging the residence time of the gas bubbles within the medium improved the efficiency of the gas transfer into the liquid phase and suppressed foam formation. An appropriate field of speed gradients prevented the bubbles from rising to the surface. This aeration method achieves an almost 90% transfer of oxygen supplied by the bubbles. Consequently, it is able to supply cells with oxygen even at high cell densities, while sparging with a gas flow of only 0.22·10^–3–1.45·10^–3 vvm (30–200 ml/h).The reactor design, the oxygen transfer rates and the high efficiency of the system are presented. Two repeated batch cultures of a rat-mouse hybridoma cell line are compared with a surface-aerated spinner culture. The used cell culture medium was serum-free, either with or without BSA and did not contain surfactants or other cell protecting agents. One batch is discussed in detail for oxygen supply, amino acid consumption and specific antibody production.