Species of Aphanolaimus (Nematoda: Araeolaimida) from Belgium

A nematological survey of Belgium revealed four species of Aphanolaimus, two known ones, A. attentus de Man, 1880 and A. aquaticus Daday, 1894, and two new ones. A. pseudoattentus n.sp. resembles A. attentus in many respects but can easily be distinguished by the greater body length, the head shape, the shape of the amphideal fovea and the longer cephalic setae. A. deconincki n.sp. is characterized by its head shape, shape of amphideal fovea, posterior origin of lateral field and large number of body annules.     

Studies on stimulus-response coupling in human neutrophils. II. Relationships between the effects of changes of external ionic composition on the properties of N-formylmethionylleucylphenylalanine receptors and on the respiratory and secretory responses

Studies were carried out on the mechanism responsible for the enhancement of the respiratory and secretory responses to N-formylmethionylleucylphenylalanine (fMet-Leu-Phe) exhibited by human neutrophils suspended in Na+-free, high-K+ buffered solution. The results demonstrate that: (a) the variation of Na+ concentration in the suspending solution induces in human neutrophils a marked modification of the recognition apparatus for the chemotactic peptide fMet-Leu-Phe, the lack of or low concentration of this ion increasing the number of the receptors and their specific affinity for the ligand; (b) the greater respiratory burst and secretion induced by fMet-Leu-Phe in human neutrophils suspended in Na+-free, high-K+ medium are due to the increased formation of receptor-ligand complexes at the cell membrane; (c) the greater respiratory response is partially due also to a higher efficiency of these receptor-ligand complexes. The molecular mechanism by which Na+ exerts a regulative role on the properties of the recognition apparatus for the chemotactic peptide and its possible significance are discussed.     

Prostacyclin production by human endothelial and bovine smooth muscle cells in culture. Effect of repeated stimulation with arachidonic acid, thrombin and ionophore A23187

Prostacyclin (prostaglandin I2) is the major product of arachidonic acid metabolism in vascular cells. Its physiological role may be linked to the ability of the cells to respond continuously with prostaglandin I2 production to a variety of stimuli. We report that human endothelial cells or bovine smooth muscle cells in culture respond with prostaglandin I2 synthesis to a first but not to a second stimulation with arachidonic acid. The development of this refractoriness was independent of the arachidonic acid concentration used (6.6-25 microM) and lasted for about 6 h. The same time was required for the cells to recover completely after inhibition of cyclooxygenase activity by aspirin. Neither cis-polyunsaturated fatty acids (linoleic or oleic acids) nor stearic acid (a long-chain saturated fatty acid) prevented the generation of prostaglandin I2 by arachidonic acid. Similarly to arachidonic acid, thrombin and ionophore A23187 could elicit vascular prostaglandin I2 synthesis only once. Pretreatment of the cells with arachidonic acid rendered the cells unresponsive to any other stimulus. These results indicate that the mechanism of the refractoriness induced by arachidonic acid was different from that induced by the other stimuli. It is proposed that vascular cells cannot be stimulated continuously to produce prostaglandin I2, but this process is regulated by different feedback mechanisms.     

Specific binding of guanosine 5'-diphosphate with the NS protein of vesicular stomatitis virus

A soluble protein fraction containing L, NS, G and M proteins of vesicular stomatitis virus was prepared by treatment of Triton-disrupted virions with 0.8M NaCl. Incubation of the soluble fraction with beta-32P GDP followed by analysis of the proteins by polyacrylamide gel electrophoresis showed specific labeling of the NS protein. The NS-GDP complex was sensitive to phosphatase treatment, suggesting non-covalent binding. No binding of GDP to NS protein was detected when the soluble fraction was pre-heated at 100 degrees C for 1 min. or Mg++ was omitted from the incubation mixture. The binding was inhibited by ATP consistent with competition for a common nucleotide binding site.     

Localized coupling in oxidative phosphorylation by mitochondria from Jerusalem artichoke (Helianthus tuberosus)

Delocalized chemiosmotic coupling of oxidative phosphorylation requires that a single-value correlation exists between the extent of and the kinetic parameters of respiration and ATP synthesis. This expectation was tested experimentally in nigericin-treated plant mitochondria in single combined experiments, in which simultaneously respiration (in State 3 and in State 4) was measured polarographically, FΔψ (which under these conditions was equivalent to ) was evaluated potentiometrically from the uptake of tetraphenylphosphonium⁺ and the rate of phosphorylation was estimated from the transient depolarization of mitochondria during State 4-State 3-State 4 transitions. The steady-state rates of the different biochemical reactions were progressively inhibited by specific inhibitors active with different modalities on various steps of the energy-transducing process: succinate respiration was inhibited competitively with malonate or noncompetitively with antimycin A, or by limiting the rate of transport into the mitochondria of the respiratory substrate with phenylsuccinate; was dissipated by uncoupling with increasing concentrations of valinomycin; ADP phosphorylation was limited with oligomycin. The results indicate generally that when the rate of respiratory electron flow is decreased, a parallel inhibition of the rate of phosphorylation is also observed, while very limited effects can be detected on the extent of . This behavior is in marked contrast to the effect of uncoupling where the decreased rate of ATP synthesis is clearly due to energy limitation. Extending previous observations in bacterial photosynthesis and in respiration by animal mitochondria and submitochondrial particles the results indicate, therefore, that respiration tightly controls the rate of ATP synthesis, with a mechanism largely independent of . These data cannot be reconciled with a delocalized chemiosmotic coupling model.     

Myocardial xanthine oxidase/dehydrogenase

High-energy phosphates in heart muscle deprived of oxygen are rapidly broken down to purine nucleosides and oxypurines. We studied the role of xanthine oxidase/dehydrogenase (EC 1.2.3.2/EC 1.2.1.37) in this process with novel high-pressure liquid chromatographic techniques. Under various conditions, including ischemia and anoxia, the isolated perfused rat heart released adenosine, inosine and hypoxanthine, and also substantial amounts of xanthine and urate. Allopurinol, an inhibitor of xanthine oxidase, greatly enhanced the release of hypoxanthine. From the purine release we calculated that the rat heart contained about 18 mU xanthine oxidase per g wet weight. Subsequently, we measured a xanthine oxidase activity of 9 mU/g wet wt. in rat-heart homogenate. When endogenous low molecular weight inhibitors were removed by gel-filtration, the activity increased to 31 mU/g wet wt. Rat myocardial xanthine oxidase seems to be present mainly in the dehydrogenase form, which upon storage at -20 degrees C is converted to the oxidase form.     

Interferon induction by platinum(II)-poly(I).poly(C) complexes

The effect of the interaction between poly(I).poly(C) and cis-dichloro-diammineplatinum(II) (cis-Pt), its trans analogue and chloro-diethylene-triamminoplatinum(II) (dien-Pt) on interferon induction activity was investigated. The covalent monodentate fixation of the three compounds on N7 of inosine has different effects on the structure and thermostability of poly(I). poly(C) which is well reflected by the interferon induction activity of the samples. Thus, the sandwich stabilization by dien-Pt at low binding ratios is manifested by an increased interferon induction and a high resistance towards RNAase degradation. The destabilization of the duplex by cis-Pt decreases interferon induction, accompanied by an increase in RNAase sensitivity of the complexes. In the case of trans-Pt the duplex structure is little perturbed and interferon induction is essentially maintained.     

Heterogeneity of Benzodiazepine Receptors: Experimental Differences Between [3H]Flunitrazepam and [3H]Ethyl-β-carboline-3-carboxylate Binding Sites in Rat Brain Membranes

Abstract: This study was designed to analyze possible differences in the binding of [³H]flunitrazepam ([³H]FNZP) and [³H]ethyl - β - carboline - 3 - carboxylate ([³H]β-CCE), to rat brain membranes, in various experimental conditions. In cerebral cortex, hippocampus, cerebellum, and orain stem the number of binding sites for [³H]β-CCE was higher than for [³H]FNZP; both were displaced by clonazepam. Until the 7th day of postnatal brain development the numbers of [³H]FNZP and [³H]β-CCE sites were equivalent; but later on, the β-carboline sites increased to a higher level. Noradrenergic denervation by 6-hydroxydopamine was followed in the hippocampal formation. Already after 2 days, there was a decrease in [³H]FNZP sites, which reached 70% of control after 14 days. Similar results were obtained with DSP-4 denervation. This change was only in B_max and not in K_D, In contrast, the [³H]β-CCE sites did not change with denervation. Neonatal injection of l - 2,4,5 - trihydroxyphenylalamine or DSP-4 produced in the adult a decrease in [³H]FNZP sites in the cerebral cortex, in parallel with the noradrenergic denervation. On the other hand, there was an increase in the cerebellum and brain stem, in correspondence with the hyperinnervation by sprouting. In these rats, the number of sites for [³H]β-CCE did not change in the different brain regions. With 0.1% Triton X-100, applied to synaptosomal membranes, [³H]FNZP binding was reduced by 35%, while that of [³H]β-CCE was not significantly changed. These results suggest that there is heterogeneity of binding sites for benzodiazepine receptors in rat brain. A tentative interpretation of the experiments involving noradrenergic denervation and hyperinnervation, as well as those with Triton X-100, is that [³H]FNZP binds to pre- and postsynaptic receptors, while [³H]β-CCE binds mainly to postsynaptic benzodiazepine receptors.