Covalent immobilization of the multienzyme enniatin synthetase

Summary The multienzyme enniatin synthetase was covalently immobilized to N-hydroxysuccinimide activated agarose. The stability of the immobilized enzyme at 25°C was enhanced compared to the soluble enzyme. Immobilization experiments also indicated that the enniatins are synthesized by a single molecule and thus do not require interactions of several enzyme molecules.     

Fortpflanzung und entwicklung vonAnemonia sulcata (Anthozoa,Actiniaria) II. Frühentwicklung,Blastula und Gastrula

Early developmental stages of theAnemonia germ are characterized by asynchronously dividing nuclei and an extreme delay of blastomere differentiation. The nuclei migrate to the periphery, whereas nutritive substances remain in the interior. Following this stage, the appearance of cell boundaries results in the formation of the blastoderm and the simultaneous division of the yolk into many fragments. Most of them are exclusively filled with reserve material; only very few contain zooxanthellae or nuclei. On the embryo's surface, conically shaped bundles of long microvilli are obvious. They appear to be less regularly arranged than the spines of oocytes before insemination. Pigment granules that have originated from fusing Golgi vesicles are crowded peripherally in the blastoderm cells. In the nucleoplasm single annulate lamellae that seem to be cut off from the nuclear envelope can frequently be found. There is no further cellular differentiation until gastrulation is completed. Though yolk-containing cellular fragments occupy nearly the whole blastocoel, entoderm formation occurs by invagination. Ultrastructural observations provide evidence of the existence of interstices between entoderm cells that allow all nutritive substances to pass gradually into the gastric cavity. In the region of the blastoporus there are cellular processes enveloping reserve material. Presumably, these observations indicate a so-called filtration of nutritive yolk (Korschelt & Heider, 1909) that might represent an additional mode for the transfer of yolk-containing cellular fragments from blastocoel into gastrocoel.     

Primary production data from the south-eastern Weddell Sea

Summary Phytoplankton production for three size classes (<20 m, 20–100 m, >100 m), total primary production and qualitative composition of phytoplankton populations were recorded from 18 stations in the south-eastern Weddell Sea in February/March 1983. Total primary production ranged between 80 and 1670 mg C m^-2 d^-1 with an average of 670 mg C m^-2 d^-1, nearly 70% of which was contributed by the <20 m size fraction (usually pennate and/or centric diatoms). Production of phytoplankton was in the higher range of values reported by other authors for the same region. Variations in primary production could not be attributed to composition of populations, ambient light levels or concentrations of macronutrients (N, P, Si). Phytoplankton populations had a higher diversity in the deeper parts of the Weddell Sea and coincided with different oceanographic situations. Three zones (along the shelf-ice edge from Atka Bay to Halley Bay, west of Halley Bay and off the Filchner/Rønne Ice Shelf) with different communities could be clearly distinguished.     

Isolation of acid-resistant urinary trypsin inhibitors by high performance liquid chromatography and their characterization by N-terminal amino-acid sequence determination

Two crude fractions of acid-resistant trypsin inhibitors (apparent molecular masses 44 and 20 kDa, respectively) were prepared from human urine by gel permeation chromatography. From both preparations the pure inhibitors were isolated by high performance liquid chromatography (HPLC). Their N-terminal amino-acid sequences were determined and compared with those of HI-30 and HI-14 as isolated by reversible binding to either immobilized trypsin or immobilized chymotrypsin. The N-terminal amino-acid sequence of the high-molecular mass inhibitor UI-I isolated by HPLC was identical with those of HI-30 and UI-C-I isolated via immobilized trypsin or chymotrypsin, respectively. The low-molecular mass inhibitors UI-II and UI-C-II differ from HI-14 by the N-terminal extension Glu-Val-Thr-Lys-when obtained by HPLC or by the extension Thr-Lys-when obtained via immobilized chymotrypsin, respectively. The comparison of these N-termini with the amino-acid sequence of HI-30 (Ala1-...-Val16-Thr-Glu-Val-Thr-Lys-HI-14) defines the low molecular urinary trypsin inhibitors as proteolytic degradation products of the high-molecular urinary inhibitor. Proteolysis may occur at different bonds. The existing discrepancies in molecular architecture and in molecular masses of the urinary trypsin inhibitors are discussed.     

Purification and properties of a stilbene synthase from induced cell suspension cultures of peanut

Stilbene synthase ( resveratrol -forming) converts one molecule of rho- coumaroyl -CoA and three molecules of malonyl-CoA into 3,4',5- trihydroxystilbene . Following selective induction of stilbene synthesis in cell suspension cultures of peanut (Arachis hypogaea), the enzyme was extracted and purified to apparent homogeneity by chromatography on DEAE-cellulose and hydroxylapatite. The enzyme was found to be a dimer of estimated Mr = 90,000 exhibiting under denaturing conditions a subunit Mr of approximately 45,000. The isoelectric point was determined with pI = 4.8. The enzyme's high selectivity towards rho- coumaroyl -CoA (Km = 2 microM) as substrate qualified it as resveratrol -forming stilbene synthase. Structurally related CoA esters, e.g. dihydro-rho- coumaroyl -CoA and cinnamoyl-CoA, were converted less than 1/10 as efficiently as rho- coumaroyl -CoA. Malonyl-CoA (Km = 10 microM) could not be substituted by acetyl-CoA. The purified enzyme was free of chalcone synthase activity. Antibodies raised against stilbene synthase were shown to be monospecific and not to cross-react with chalcone synthase.     

Growth of E. coli in a stirred tank and in an air lift tower reactor with an outer loop

E. coli ATCC 11105 was cultivated in a 10-1 stirred tank reactor and in a 60-1 tower loop reactor in batch and continuous operation. By on-line measurements of O₂ and CO₂ concentrations in the outlet gas, pH, temperature, cell mass concentration X as well as dissolved O₂ concentration along the tower in the broth, gas holdup, broth recirculation rate through the loop and by offline measurements of substrate concentration DOC and cell mass concentration along the tower, the maximum specific growth rate _m , yield coefficients Y _X/S. Y _X/DOC and were evaluated in stirred tank and tower loop in batch and continuous cultures with and without motionless mixers in the tower and at different broth circulation rates through the loop. To control the accuracy of the measurements the C balance was calculated and 95% of the C content was covered.The biological parameters determined depend on the mode of operation as well as on the reactor used. Furthermore, they depend on the recirculation rate of the broth and built-ins in the tower. The unstructured cell and reactor models are unable to explain these differences. Obviously, structured cell and reactor models are needed. The cell mass concentration can be determined on line by NADH fluorescence in balanced growth, if the model parameters are determined under the same operational conditions in the same reactor.List of Symbols a, b empirical parameters in Eq. (1) - CPR kg/(m³ h) CO₂ production rate - C kg/m³ concentration - D l/h dilution rate - DOC kg/m³ dissolved organic carbon - I net. fluorescence intensity - K _S kg/m³ Monod constant - k _L a l/h volumetric mass transfer coefficient - OTR kg/(m³ h) oxygen transfer rate - OUR kg/(m³ h) oxygen utilization rate - RQ = CPR/OUR respiratory quotient - S kg/m³ substrate concentration - t h,min, s time - t _u min recirculation time - t _M min mixing time - v m³/h volumetric flow rate through the loop - X kg/m³ (dry) cell mass concentration - Y _X/S yield coefficient of cell mass with regard to the consumed substrate - Y _X/DOC yield coefficient of the cell mass with regard to the consumed DOC - Y _X/O yield coefficient of the cell mass with regard to the consumed oxygen - Z relative distance in the tower from the aerator with regard to the height of the aerated broth - l/h specific growth rate - _m l/h maximum specific growth rate Indices f feed - e outlet     

Spatiotemporal receptive fields: a dynamical model derived from cortical architectonics

We assume that the mammalian neocortex is built up out of some six layers which differ in their morphology and their external connections. Intrinsic connectivity is largely excitatory, leading to a considerable amount of positive feedback. The majority of cortical neurons can be divided into two main classes: the pyramidal cells, which are said to be excitatory, and local cells (most notably the non-spiny stellate cells), which are said to be inhibitory. The form of the dendritic and axonal arborizations of both groups is discussed in detail. This results in a simplified model of the cortex as a stack of six layers with mutual connections determined by the principles of fibre anatomy. This stack can be treated as a multi-input-multi-output system by means of the linear systems theory of homogeneous layers. The detailed equations for the simulation are derived in the Appendix. The results of the simulations show that the temporal and spatial behaviour of an excitation distribution cannot be treated separately. Further, they indicate specific processing in the different layers and some independence from details of wiring. Finally, the simulation results are applied to the theory of visual receptive fields. This yields some insight into the mechanisms possibly underlying hypercomplexity, putative nonlinearities, lateral inhibition, oscillating cell responses, and velocity-dependent tuning curves.     

α-1,4-glucan phosphorylase forms from leaves of spinach (Spinacia oleracea L.)

Peptide patterns and immunological properties of the cytoplasmic and chloroplastic -1,4-glucan phosphorylase (EC 2.4.1.1) from spinach leaves have been studied and were compared with those of phosphorylases from other sources. The two spinach leaf phosphorylases were immunologically different; a limited cross-reactivity was observed only at high antigen or antibody concentrations. Peptide mapping of the two enzymes resulted in complex patterns composed of more than 20 fragments; but no peptide was electrophoretically identical in both proteins. Approximately 13 to 15 of the fragments exhibited antigeneity but no cross-reactivity of any peptide was observed. Therefore, the two compartment-specific phosphorylase forms from spinach leaves represent isoenzymes possessing different primary structures. Peptide patterns of potato tuber and rabbit muscle phosphorylase were different from those of the two spinach leaf enzymes. Although the potato tuber phosphorylase resides in the plastidic compartment and is kinetically closely related to the chloroplastic spinach enzyme, it reacted more strongly with the anti-cytoplasmic-phosphorylase immunoglobulin G. Similar results were obtained with rabbit muscle phosphorylase. These observations support the assumption that the chloroplast-specific phosphorylase isoenzyme has a higher structural diversity than does the cytoplasmic counterpart.Abbreviations EDTA ethylenediaminetetraacetic acid - Hepes 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid - PEG polyethylene glycol (approx. MW 8000) I=Schächtele and Steup 1986     

Maternal-effect mutations altering the anterior-posterior pattern of the Drosophila embryo

Summary Mutations in seven different maternal-effect loci on the second chromosome of Drosophila melanogaster all cause alterations in the anterior-posterior pattern of the embryo. Mutations in torso (tor) and trunk (trk) delete the anterior- and posterior-most structures of the embryo. At the same time they shift cellular fates which are normally found in the subterminal regions of the embryo towards the poles. Mutations in vasa (vas), valois (vls), staufen (stau) and tudor (tud) cause two embryonic defects. For one they result in absence of polar plasm, polar granules and pole cells in all eggs produced by mutant females. Secondly, embryos developing inside such eggs show deletions of abdominal segments. In addition, embryos derived from staufen mothers lack anterior head structures, embryos derived from valois mothers frequently fail to cellularize properly. Mutations in exuperantia (exu) cause deletions of anterior head structures, similar to torso, trunk and staufen. However in exu, these head structures are replaced by an inverted posterior end which comprises posterior midgut, proctodeal region, and often malpighian tubules.The effects of all mutations can be traced back to the beginning stages of gastrulation, indicating that the alterations in cellular fates have probably taken place by that time. Analysis of embryos derived from double mutant mothers suggests that these three phenotypic groups of mutants interfere with three different, independent pathways. All three pathways seem to act additively on the system which specifies anterior-posterior cellular fates within the egg.