Effect of oxygen on ethanol fermentation in packed-bed tapered-column reactor

Summary In ethanol production with immobilized yeast a major problem is the provision of nutrients to these highly concentrated cells. O₂ being one of the nutrients of utmost importance to yeast cells, was fed into a column packed with beads with a cell loading of more than 40 g/l. Since addition of large volume of air or O₂ to a cylindrical column reactor would aggravate the problems of pressure build up and channelling caused by the evolving CO₂ gas, a tapered-column reactor and pulsed flow of oxygen gas was used. The supplement of O₂ gas to the tapered column increased the productivity from 21.1 g ethanol x (l gel x h)^-1 to 26.7 g x (l gel x h)^-1, when the ethanol concentration at the outlet was about 80 g/l. The yield coefficient of ethanol was also increased from 0.41 g ethanol/g glucose to 0.43 after O₂ supplement was started. The effects of frequency and duration of O₂ supplement were also determined.     

5-Hydroxytryptamine-Stimulated Inositol Phospholipid Hydrolysis in the Mouse Cortex Has Pharmacological Characteristics Compatible with Mediation via 5-HT2 Receptors but This Response Does Not Reflect Altered 5-HT2 Function After 5,7-Dihydroxytryptamine Lesioning or Repeated Antidepressant Treatments

5-Hydroxytryptamine (5-HT; 3 x 10(-8)-1 x 10(-5)M) produced a dose-dependent increase in phosphatidylinositol/polyphosphoinositide (PI) turnover in mouse cortical slices, as measured by following production of 3H-labelled inositol phosphates (IPs) in the presence of 10 mM LiCl. Analysis of individual IPs, in slices stimulated for 45 min, indicated substantial increases in inositol monophosphate (IP1; 140%) and inositol bisphosphate (IP2; 95%) contents with smaller increases in inositol trisphosphate (IP3; 51%) and inositol tetrakisphosphate (IP4; 48%) contents. The increase in IP3 level was solely in the 1,3,4-isomer. This response was inhibited by the nonselective 5-HT antagonists methysergide, metergoline, and spiperone. It was also inhibited by the selective 5-HT2 antagonists ketanserin and ritanserin but not by the 5-HT1 antagonists isapirone, (-)-propranolol, or pindolol. 5-HT-stimulated IP formation was also unaltered by atropine, prazosin, and mepyramine. Lesioning brain 5-HT neurones using 5,7-dihydroxytryptamine (5,7-DHT; 50 micrograms i.c.v.) produced a 210% (p less than 0.01) increase in the number of 5-HT2-mediated head-twitches induced by 5-methoxy-N,N-dimethyltryptamine (2 mg/kg). However, 5,7-DHT lesioning had no effect on 5-HT-stimulated PI turnover in these mice. Similarly, an electroconvulsive shock (90 V, 1 s) given five times over a 10-day period caused an 85% (p less than 0.01) increase in head-twitch responses but no change in 5-HT-stimulated PI turnover. Decreasing 5-HT2 function by twice-a-day injection of 5 mg/kg of zimeldine or desipramine (DMI) produced 50% (p less than 0.01) and 56% (p less than 0.01), respectively, reductions in head-twitch behaviour.(ABSTRACT TRUNCATED AT 250 WORDS)     

Developmental changes in the distribution of cecal lectin-binding sites of Balb-c mice.

The existence of lectin-binding sites was investigated in the cecum of Balb-c mice at seven developmental stages ranging from 18 days post conception (p.c.) to 8 weeks after birth. Nine horseradish-peroxidase-conjugated lectins (concanavalin A, Triticum vulgaris, Dolichus biflorus, Helix pomatia, Arachis hypogaea, Glycine maximus, Lotus tetragonolobus, Ulex europaeus, Limulus polyphemus) were applied to 5- to 7-microns thin paraffin sections of Bouin-fixed tissue. After DAB staining the sections were evaluated by light microscopy. It was shown that each lectin exhibits a unique developmental pattern. The adult binding patterns were established at the age of 3-4 weeks with only minor changes occurring thereafter. Considerable differences in binding patterns occurred not only between lectins of different groups but also between lectins with the same nominal monosaccharide specificity.     

Repeated sequence elements in the high molecular weight basic nuclear proteins from the winter flounder

In maturing sperm of the winter flounder, histones are not replaced by protamines but instead joined by a group of high molecular weight basic nuclear proteins. Despite their large size and number of components, these proteins were reduced to a relatively simple set of peptides by a "limit" digestion with endoprotease Lys-C. Nine of these peptides, that together account for half of the mass of the digest, were purified by two rounds of chromatography on a C18 reverse-phase high pressure liquid chromatographic column and analysed by sequential Edman degradation. Their sequences can be divided into two homology groups. Seven of the peptides contain all or part of a dodecapeptide consensus sequence, NH2-Ser-Pro-Met-Arg-Ser-Arg-Ser-Pro-Ser-Arg-Ser-Lys-COOH, which appears to be tandemly repeated. This dodecapeptide contains a previously recognized consensus phosphorylation sequence, NH2-Arg-Ser-Arg-Ser-Pro-COOH, in which both serines are phosphorylated during the early stages of spermiogenesis. The other homology group has the sequence NH2-Arg-Arg-Val-X-X-Pro-Lys-COOH, where X-X is either Gln-Thr or Pro-Ser. The dodecapeptide and heptapeptide sequences form at least 35 and 11%, respectively, of the high molecular weight basic nuclear proteins and are, therefore, repeated many times over in these proteins. A search for identical or homologous sequences within the Protein Sequence Database indicated that they are unique. The closest matches were to protamines and some viral DNA-binding proteins.     

Mutations in the signal sequence of prepro-alpha-factor inhibit both translocation into the endoplasmic reticulum and processing by signal peptidase in yeast cells.

The effects of five single-amino-acid substitution mutations within the signal sequence of yeast prepro-alpha-factor were tested in yeast cells. After short pulse-labelings, virtually all of the alpha-factor precursor proteins from a wild-type gene were glycosylated and processed by signal peptidase. In contrast, the signal sequence mutations resulted in the accumulation of mostly unglycosylated prepro-alpha-factor after a short labeling interval, indicating a defect in translocation of the protein into the endoplasmic reticulum. Confirming this interpretation, unglycosylated mutant prepro-alpha-factor in cell extracts was sensitive to proteinase K and therefore in a cytosolic location. The signal sequence mutations reduced the rate of translocation into the endoplasmic reticulum by as much as 25-fold or more. In at least one case, mutant prepro-alpha-factor molecules were translocated almost entirely posttranslationally. Four of the five mutations also reduced the rate of proteolytic processing by signal peptidase in vivo, even though the signal peptide alterations are not located near the cleavage site. This study demonstrates that a single-amino-acid substitution mutation within a eucaryotic signal peptide can affect both translocation and proteolytic processing in vivo and may indicate that the recognition sequences for translocation and processing overlap within the signal peptide.     

Characterization of D2 receptors and dopamine levels in the thalamus of the rat.

We kinetically characterized D2 receptors in thalami pooled from a group of Sprague-Dawley rats and then determined thalamic levels of dopamine (DA), homovanillic acid (HVA), dihydroxyphenylacetic acid (DOPAC), and norepinephrine (NE) in relation to a measure of thalamic DA D2 receptor densities in another group of rats. The equilibrium dissociation constant (kd) was estimated as 0.1 nM by three independent methods, while the Bmax for thalamic D2 receptors was found to be 6.4 fmol/mg p using 3H-spiperone as ligand and ketanserin to occlude 5HT2 binding. Kinetic constants were in agreement with previously reported kinetic data from rodent caudate-putamen. This suggests that thalamic D2 receptors are similar to D2 receptors from other brain areas. Mean thalamic levels of DA (22.6 ng/mg p), DOPAC (1.19 ng/mg p) and HVA (0.31 ng/mg p) concur with previous reports of a sparse distribution of thalamic DA neurons. D2 receptor densities were positively correlated with DA metabolites DOPAC (P less than .05; r = 0.423) and HVA (P less than .05; r = 0.368), but not DA or NE. These results establish fundamental characteristics of thalamic DA neurotransmission to assist in the investigation of behavioral pharmacology of this area.     

Isolation and partial characterization of genomic clones coding for a human pro-alpha 1 (II) collagen chain and demonstration of restriction fragment length polymorphism at the 3' end of the gene

We have isolated two clones containing 19 kilobases (kb) of the human gene coding for a pro-alpha 1 (II) collagen chain from human lambda genomic DNA libraries. A 3' clone, HC2A, was selected by cross-hybridization with a cDNA clone containing sequences coding for the carboxy propeptide of chick type II procollagen. A second clone, HC2B, was obtained by screening the library with the 5' part of HC2A. The sequence analysis of exon 3 corresponding to the C propeptide reveals the presence of stretches of conserved nucleotides between the human and the chick type II procollagen genes. On Northern blots, the human collagen clone hybridizes strongly to a 5.5-kb RNA for the rat type II procollagen chain. Finally, studies of genomic DNAs from normal individuals reveal the presence of a HindIII and a BamHI polymorphic site at the 3' end of the gene.