Large Tristichopteridae (Sarcopterygii, Tetrapodomorpha) from the Late Famennian Evieux Formation of Belgium

Remains of two large sarcopterygians are described from Famennian deposits in Belgium. One of them is referred to Eusthenodon wängsjöi Jarvik; it is the first occurrence of this genus in Belgium. The other, much larger one, appears to be a tristichopterid. It has a postspiracular; size and shape of the mandible similar to those of Platycephalichthys skuenicus and P. bischoffi ; snout and cheek patterns close to those of Eusthenodon ; unusual shape of the supratemporal resembling that of Hyneria , Mandageria and Platycephalichthys skuenicus ; and tooth histology quite similar to that of Eusthenodon and Platycephalichthys .     

Effect of Repeated Convulsive Seizures on Brain γ-Aminobutyric Acid Metabolism in Three Sublines of Mice Differing by Their Response to Acoustic Stimulations

The turnover rates and steady-state levels of gamma-aminobutyric acid (GABA) have been determined in 15 brain areas of three sublines of inbred mice differing in their susceptibility to audiogenic seizures: Rb3, which is seizure resistant; Rb2, which develops clonic seizures; and Rb1, which develops tonic-clonic seizures. In the Rb1 subline, GABA steady-state levels are lower than in the Rb3 subline in three of the 15 areas examined (cerebellum, anterior colliculus, and amygdala), whereas in the Rb2 subline, steady-state levels are either higher (posterior colliculus and hippocampus) or lower (amygdala) than in the Rb3 subline. GABA turnover rates differ in three brain areas in Rb1 (amygdala, raphe, and hypothalamus) and in a single area (amygdala) in Rb2 when compared with Rb3. Only one area has similar variations of GABA turnover rate and steady-state levels in the two susceptible sublines: the amygdala. After 2 weeks of repeated auditory stimulations (two times a day, 8,000 Hz, 100 dB), additional alterations in GABA metabolism are observed: mainly large increases in GABA turnover rates (from 40% to three- to fourfold). The Rb2 subline displays a greater number of alterations (increases of turnover rates in pons, cerebellum, anterior and posterior colliculus, amygdala, olfactory bulbs and tubercles, striatum, and frontal cortex) than the Rb1 subline (increases of turnover rates in cerebellum, posterior colliculus, olfactory tubercles, raphe, and frontal cortex and a decrease in hypothalamus). In the Rb3 subline, increases of the turnover rate in amygdala and olfactory tubercles and decreases in olfactory bulbs and hippocampus are observed.(ABSTRACT TRUNCATED AT 250 WORDS)     

Cholera toxin and pertussis toxin regulate the Fc receptor-mediated phagocytic response of human neutrophils in a manner analogous to regulation by monoclonal antibody 1C2

Data presented in this paper indicate that polymorphonuclear leukocyte (PMN) Fc receptor-mediated phagocytosis can be markedly augmented and that this augmentation is under regulatory control. Stimulation of PMN with either a low m.w., heat-labile cytokine(s) (the culture supernatant effluent from a YM-10 Centricon unit, YM-10E), phorbol esters (phorbol dibutyrate), or the polyene antibiotic, amphotericin B, enhances Fc-mediated ingestion in a dose-dependent manner. YM-10 effluent- and amphotericin B-stimulated ingestion is completely abrogated by treating the PMN with either pertussis toxin (PT), cholera toxin (CT), or a monoclonal antibody (mAb), 1C2. However, neither toxin nor mAb 1C2 affects nonstimulated ingestion or phagocytosis stimulated by phorbol esters or synthetic diacylglycerol. Increasing intracellular cyclic adenosine monophosphate levels by stimulation with prostaglandin E1 and the phosphodiesterase inhibitor, isobutylmethylxanthine, does not mimic the effect of either toxin or mAb 1C2. In addition, toxin-mediated inhibition is not due to loss of either the Fc receptor recognized by mAb 3G8 or the antigen recognized by mAb 1C2. These data indicate that both CT and PT regulate the phagocytic response of PMN, in a manner like mAb 1C2, probably by affecting a guanosine 5'-triphosphate-binding protein distinct from those that regulate adenylate cyclase. Since phorbol ester-stimulated ingestion is not inhibited by either PT, CT, or mAb 1C2 and phorbol esters activate protein kinase C directly, phagocytosis amplification regulated by PT, CT, and mAb 1C2 may involve protein kinase C activation.     

Role of xanthine oxidase inhibitor as free radical scavenger: a novel mechanism of action of allopurinol and oxypurinol in myocardial salvage

Xanthine oxidase (XO) has been hypothesized to be a potential source of oxygen-derived free radicals during reperfusion of ischemic myocardium based on the fact that allopurinol, a XO-inhibitor, can reduce reperfusion injury. In this communication we report that both allopurinol and oxypurinol, the principle metabolite of allopurinol, prevent the reperfusion injury in isolated pig heart. However, we found that neither pig heart nor pig blood contain any XO activity. Our study showed a direct free radical scavenging action of these XO-inhibitors during ischemia and reperfusion, as judged by the reduction of free radical signals when compared using an Electron Paramagnetic Resonance Spectrometer. Using a Luminometer, we also confirmed that both allopurinol and oxypurinol can scavenge ClO2, HOCl, and significantly inhibit free radical signals generated by activated neutrophils. These XO-inhibitors, however, failed to scavenge O2. and OH. radicals. Our results suggest that these XO-inhibitors salvaged the ischemic-reperfused myocardium by scavenging free radicals, and not by inhibiting XO in the pig heart.     

Methanol metabolism in thermotolerant methylotrophic Bacillus strains involving a novel catabolic NAD-dependent methanol dehydrogenase as a key enzyme

The enzymology of methanol utilization in thermotolerant methylotrophic Bacillus strains was investigated. In all strains an immunologically related NAD-dependent methanol dehydrogenase was involved in the initial oxidation of methanol. In cells of Bacillus sp. C1 grown under methanol-limiting conditions this enzyme constituted a high percentage of total soluble protein. The methanol dehydrogenase from this organism was purified to homogeneity and characterized. In cell-free extracts the enzyme displayed biphasic kinetics towards methanol, with apparent K _m values of 3.8 and 166 mM. Carbon assimilation was by way of the fructose-1,6-bisphosphate aldolase cleavage and transketolase/transaldolase rearrangement variant of the RuMP cycle of formaldehyde fixation. The key enzymes of the RuMP cycle, hexulose-6-phosphate synthase (HPS) and hexulose-6-phosphate isomerase (HPI), were present at very high levels of activity. Failure of whole cells to oxidize formate, and the absence of formaldehyde-and formate dehydrogenases indicated the operation of a non-linear oxidation sequence for formaldehyde via HPS. A comparison of the levels of methanol dehydrogenase and HPS in cells of Bacillus sp. C1 grown on methanol and glucose suggested that the synthesis of these enzymes is not under coordinate control.Abbreviations RuMP ribulose monophosphate - HPS hexulose-6-phosphate synthase - HPI hexulose-6-phosphate isomerase - MDH methanol dehydrogenase - ADH acohol dehydrogenase - PQQ pyrroloquinoline, quinone - DTT dithiothreitol - NBT nitrobluetetrazolium - PMS phenazine methosulphate - DCPIP dichlorophenol indophenol     

Assembly properties of two CNBr fragments of avian desmin that correspond to the headpiece domain and helix 1B

To study how different domains of the muscle-specific intermediate filament protein, desmin, contribute to its polymerization, two of its CNBr fragments were examined as to their oligomeric structure under assembly conditions. One of these, D88, covers residues 1-88 and represents almost the entire headpiece; the other, D109, covers residues 145-254, and includes the entire Helix 1B and part of linker L12 of the intact molecule. Chemical cross-linking followed by SDS-PAGE, and analytical gel filtration, revealed that in 10 mM Tris-HCl, pH 8.5, conditions that favor tetramerization of intact desmin D88 formed only dimers. D109, on the other hand, formed primarily a dimeric species but low levels of trimeric and tetrameric species were also detectable. These data are consistent with the proposal that, during assembly of intact protein molecules into IF, the headpiece and Helix 1 contribute to dimerization of two polypeptides into a parallel, in-register coiled-coil. However, additional interactions, including headpiece-to-rod binding and hydrophobic interaction along the entire rod domain, are required to stabilize the tetramers and full-size IF.     

Heterotrophic activity and bacterial productivity in assemblages of microbes from sea ice in the high Arctic

Summary Heterotrophic activity in the bottom few cm of annual sea ice in the Canadian Arctic was measured throughout the spring bloom of ice algae, using tritium-labelled thymidine and glucose. Experiments with chloramphenicol and cyclohexamide indicated that thymidine assimilation was due to procaryotic microbes but that about half of the glucose assimilation was due to eucaryotic organisms. Glucose and thymidine assimilation rates increased with salinity, from 10 ppt to 30 ppt. Thymidine assimilation rates increased from 1.16 to 4.94·10^–21mol·cell^–1·h^–1 during the latter half of the algal bloom, while the exponential growth rate of the in situ populations decreased from 0.058 to 0.025 d^–1. Bacterial production and specific growth rates calculated from thymidine assimilation were 149mgC·m^–2 and 0.25 d^–1 or less respectively over the 50 day observation period, compared with net primary production of 5,500 mgC·m^–2. Thymidine assimilation rates suggested that about half of the bacterial production may be consumed or lost from the ice during the bloom.     

Signal transduction of gamma/delta T cell antigen receptor with a novel mitogenic anti-delta antibody

Human T lymphocytes express either alpha/beta- or gamma/delta-TCR in association with the CD3 complex. We have isolated a mAb, delta TCS1, that immunoprecipitated the gamma/delta-TCR heterodimer from cell lysates of Peer and Molt-13 leukemia cell lines. After dissociation of the gamma- and delta-chains of TCR by treatment with SDS, delta TCS1 specifically immunoprecipitated the delta-chain. This antibody bound to the surface of other gamma/delta-positive T cell lines and clones and was able to stimulate the proliferation of a minor cell population (0.9 to 4.0%) of resting human PBL. Upon binding to gamma/delta-TCR-bearing Molt-13 cells and PBL, delta TCS1 elicited a fura-2 Caa+ signal indicating that the gamma/delta-receptor is functionally similar to the alpha/beta-heterodimer. These data indicate that the delta TCS1 antibody recognizes an epitope on TCR delta-chain and its mitogenic activity should be useful in characterizing the functional properties of human gamma/delta-positive T lymphocytes.