Relationships between polyamine metabolism and RNA synthesis in post-ischemic liver cell repair

In liver cells recovering from reversible ischemia the increase in RNA synthesis by isolated nuclei is preceded by activation of ornithine decarboxylase, leading in turn to an increase in putrescine concentration. Treatment of the animals with 1,3-diaminopropane and putrescine prevents ornithine decarboxylase activation but does not hinder the enhancement of RNA synthesis in post-ischemic liver nuclei; therefore, ornithine decarboxylase activation does not seem to be a necessary prerequisite for the increase in RNA synthesis. Hypophysectomy does not prevent the post-ischemic increases of ornithine decarboxylase and RNA synthesis; but pre-treatment of the animals with cycloheximide—which has a dual effect on the activity of ornithine decarboxylase—abolishes the post-ischemic enhancement of RNA synthesis. In contrast with regenerating liver, changes in ornithine decarboxylase activity and putrescine concentrations in reversible ischemia are not associated to changes in S-adenosylmethionine decarboxylase activity and in spermine and spermidine concentrations that seem to be characteristic of tissues where increases in RNA synthesis are followed by DNA synthesis and cell multiplication.     

Use of the upflow sludge blanket (USB) reactor concept for biological wastewater treatment,especially for anaerobic treatment

In recent years considerable effort has been made in the Netherlands toward the development of a more sophisticated anaerobic treatment process, suitable for treating low a strength wastes and for applications at liquid detention times of 3–4 hr. The efforts have resulted in new type of upflow anaerobic sludge blanket (UASB) process, which in recent 6 m³ pilot-plant experiments has shown to be capable of handling organic space loads of 15–40 kg chemical oxygen demand (COD)·m^?3/day at 3–8 hr liquid detention times. In the first 200 m³ full-scale plant of the UASB concept, organic space loadings of up to 16 kg COD·m^?3/day could be treated satisfactorily at a detention times of 4 hr, using sugar beet waste as feed. The main results obtained with the process in the laboratory as well as in 6 m³ pilot plant and 200 m³ full-scale experiments are presented and evaluated in this paper. Special attention is given to the main operating characteristics of the UASB reactor concept. Moreover, some preliminary results are presented of laboratory experiments concerning the use of the USB reactor concept for denitrification as well as for the acid formation step in anaerobic treatment. For both purposes the process looks feasible because very satisfactory results with respect to denitrification and acid formation can be achieved at very high hydraulic loads (12 day^?1) and high organic loading rates, i.e., 20 kg COD·m^?3/day in the denitrification and 60–80 kg COD·m^?3/day in the acid formation experiments.     

Cell labelling and separation with polyglutaraldehyde microspheres

Non-magnetic and magnetic polyglutaraldehyde microspheres were used in the labelling and separation of mouse and human T and B lymphocytes. The enrichment of the separated T- and B-cell fractions of mouse and human cells was 30 and 40% respectively. After magnetic separation 79% of the mouse B-cell fraction and 23% of the T-cell fraction were surface Ig-positive. The corresponding figures for human T and B cells were 10 and 51–54%, respectively. The labelling of mouse spleen B cells with antibody-conjugated non-magnetic microspheres was between 27–53% depending on the labelling procedures. The best labelling was obtained when mouse spleen cells coated with rabbit anti-mouse Ig were incubated with protein A-coupled microspheres.     

Internally elongated rodent α-crystallin A chain: Resulting from incomplete RNA splicing?

αA^Ins, an elongated α-crystallin A chain previously observed in rat, was present beside the normal αA chain in mouse, gerbil and hamster, which places its origin at least 30 million years ago. Like in rat the sequences of golden hamster αA^Ins and αA were found to be identical, apart from the internal insertion of 22 residues in αA^Ins. The hamster chains only differed from the rat chains by a single substitution in the inserted sequence of αA^Ins. The origin of αA^Ins, by insertion of 22 residues in an otherwise unchanged αA chain, and its rigid evolutionary conservation are most easily explained by assuming the incomplete removal of a putative intervening sequence from the precursor mRNA of αA, leaving an intracistronic insert of 66 nucleotides in part of the eventually translated mRNA.     

Inhibition and facilitation in parasympathetic ganglia of the urinary bladder

Neurons in vesical parasympathetic ganglia receive excitatory and inhibitory inputs from both divisions of the autonomic nervous system. Sacral parasympathetic pathways (cholinergic) provide the major excitatory input to these ganglia via activation of nicotinic receptors. Parasympathetic pathways also activate muscarinic inhibitory and excitatory receptors, which may exert a modulatory influence on transmission. Cholinergic transmission is relatively inefficient when preganglionic nerves are stimulated at low frequencies (< 1 Hz). However, excitatory postsynaptic potentials (EPSPs) and postganglionic firing markedly increase during repetitive stimulation at frequencies of 1-10 Hz. It is concluded that enhanced transmitter release accounts for the temporal facilitation and that vesical ganglia function as "high pass filters" that amplify the parasympathetic excitatory input to the detrusor muscle during micturition. Transmission in vesical ganglia is also sensitive to adrenergic inhibitory and facilitatory synaptic mechanisms elicited by efferent pathways in the hypogastric nerves. The effects of exogenous norepinephrine indicate that adrenergic inhibition is mediated by alpha receptors and reflects primarily a presynaptic depression of transmitter release although postsynaptic adrenergic hyperpolarizing and depolarizing effects have also been noted. Adrenergic facilitation is mediated by beta receptors as well as unidentified receptors. Norepinephrine also can inhibit or excite spontaneously active neurons in vesical ganglia. The existence of inhibitory and facilitatory synaptic mechanisms in vesical ganglia provides the basis for a complex ganglionic modulation of the central autonomic outflow to the bladder.     

Rat pancreas adenylate cyclase. VI. Role of the enzyme in secretin stimulated enzyme secretion.

1. The responsiveness of adenylate cyclase and enzyme secretin for secretin and the C-terminal octapeptide of pancreozymin has been investigated in particulate fractions of the pancreas of five different species. 2. The adenylate cyclase is sensitive to the C-terminal octapeptide of pancreozymin in all species investigated. 3. The enzyme is much more sensitive to secretin in rat and cat than in mouse and rabbit, whereas with guinea pig intermediate values are obtained. 4. The enzyme secretion is stimulated by secretin in pancreatic fragments of rat and cat, but not in those of mouse and rabbit. 5. These results suggest that in species where secretin stimulated enzyme secretion, it does so by stimulating the adenylate cyclase system.     

Ammonia overloading in hepatocytes isolated from liver of fetal and adult rats

Ammonia overloading was investigated during glucose and fructose metabolism in isolated hepatocytes under a variety of metabolic conditions. In all assay conditions, the glycolytic flux and oxygen uptake was not modified by 10 mM ammonia. In hepatocytes isolated from rats fed as libitum, the presence of ammonia caused a decrease in the production of lactate (pyruvate); this effect was not observed in anaerobic incubations, in hepatocytes isolated from starved animals, or in fetal hepatocytes. In spite of an overproduction of urea, ammonia detoxification also takes place by the synthesis of alanine, glutamate and aspartate. Addition of 1 mM aminooxyacetate, an inhibitor of aminotransferases, to the incubation medium prevents the formation of these amino acids, and also prevents the decrease of lactate in hepatocytes isolated from fed animals.     

Lipid-protein interactions: NMR study of melittin and its binding to lysophosphatidylcholine.

Proton NMR of melittin differs according to the association state of the peptide in the monomer or tetramer. Melittin interacts with lysophosphatidyl-choline micelles, whatever the association state of melittin; well resolved superimposed spectra from both components for all the lipid to peptide molar ratios are observed. Within the complexes, local mobility and fast exchange occurs. On binding concomitant shifts on Trp19 indole lines and on the aliphatic CH2 protons of the lipids are detected. The lipid perturbation is maximum for methylene groups in a alpha and beta of the ester bond, this could allow positionning of Trp19 in the hydrophobic core of the lipids.     

Isolation and characterization of a trypsin inhibitor fromVigna sinensis seeds

The major trypsin inhibitor ofVigna sinensis cv. seridó was isolated and shown to be devoid of chymotrypsin inhibiting activity. It has a molecular weight of 9800 as determined by gel electrophoresis and a pI of 5.0. The activity of the inhibitor was decreased by treatment with trinitrobenzenesulfonic acid, suggesting that it isa LYS-X type trypsin inhibitor. Selfassociation of the molecule was demonstrated both in 1% sodium dodecylsulfate and inacidic (pH 2.4) conditions.     

Chromosome polymorphism in populations of the grasshopper Trimerotropis pallidipennis from southern Argentina

Three populations of the grasshopper Trimerotropis pallidipennis from southern Argentina have been studied cytologically. A very characteristic B-chromosome was found in all three. They also showed geographical variability in respect of the presence of pericentric inversions, and the inversion system was found to influence chiasma frequency. The Laguna Blanca population, which is on the hypothetical pathway the species is believed to have followed during its migration from northern to southern latitudes, has the same karyotype composition as the N. American form, with fixed inversions in the 3 largest autosomes and the X-chromosome. Its members have a high total chiasma frequency and a great number of interstitial chiasmata. The Sierra de la Ventana population, situated at the absolute eastern border of the species distribution is highly polymorphic with respect to the presence of inversions in the medium chromosomes. Its members have the lowest total chiasma frequency and a greatly reduced number of interstitial chiasmata. Situated geographically between the other two, the Choele-Choel population has the highest frequency of inversions and many of them are homozygous. Its members have a higher total chiasma frequency than that observed in specimens from Sierra de la Ventana, and a greatly reduced number of interstitial chiasmata, similar to that observed in individuals from the latter population.