Two new opecoelids (Digenea) in the flatfish Pseudorhombus jenynsi (Bleeker) from Shark Bay,Western Australia

The first marine fish digeneans recorded from Shark Bay, Western Australia are described from the flatfish Pseudorhombus jenynsi. Macvicaria dampieri n. sp. differs from the other members of the genus in its undivided, straight, saccular seminal vesicle, and the definition of the genus is extended to include this feature. The following new combinations are made: Macvicaria branchiostegi (Yamaguti, 1937) [originally Plagioporus] and M. cynoglossi (Madhavi, 1975) [originally P.]. Cainocreadium alanwilliamsi n. sp. is distinguished by the variable anterior extent of its excretory vesicle, which reaches to a level ranging between the posterior margin of the ventral sucker and just into the forebody, and by its relatively short forebody.     

Essential carboxy groups in xylanase A.

An endo-1,4-beta-xylanase of Schizophyllum commune was purified to homogeneity through a modified procedure employing DEAE-Sepharose CL-6B and gel-filtration chromatography on Sephadex G-50. The role of carboxy groups in the catalytic mechanism was delineated through chemical modification studies. The water-soluble carbodi-imide 1-(4-azonia-4,4-dimethylpentyl)-3-ethylcarbodi-imide iodide (EAC) inactivated the xylanase rapidly and completely in a pseudo-first-order process. Other carbodi-imides and Woodward's Reagent K were less effective in decreasing enzymic activity. Significant protection of the enzyme against EAC inactivation was provided by a mixture of neutral xylo-oligomers. The pH-dependence of the EAC inactivation revealed the presence of a critical ionizable group with a pKa value of 6.6 in the active site of the xylanase. Treatment of the enzyme with diethyl pyrocarbonate resulted in modification of all three histidine residues in the enzyme with 100% retention of original enzymic activity. Titration of the enzyme with 5,5-dithiobis-(2-nitrobenzoic acid) and treatment with iodoacetimide and p-chloromercuribenzoate indicated the absence of free/reactive thiol groups. Reaction of the xylanase with tetranitromethane did not result in a significant activity loss as a result of modification of tyrosine residues.     

Organ-Specific and Environmentally Regulated Expression of Two Abscisic Acid-Induced Genes of Tomato : Nucleotide Sequence and Analysis of the Corresponding cDNAs

The cDNAs, pLE4 and pLE25, represent mRNAs that accumulate in response to water deficit and elevated levels of endogenous abscisic acid in detached leaves of drought-stressed tomato (Lycopersicon esculentum Mill., cv Ailsa Craig) (A Cohen, EA Bray [1990] Planta 182: 27-33). DNA sequence analysis of pLE4 and pLE25 showed that the deduced polypeptides were 13.9 and 9.3 kilodaltons, respectively. Each polypeptide was hydrophilic, cysteine- and tryptophan-free, and found to be similar to previously identified proteins that accumulate during the late stages of embryogenesis. pLE4 and pLE25 mRNA accumulated in a similar organ-specific pattern in response to specific abiotic stresses. Yet, expression patterns of the corresponding genes in response to developmental cues were not similar. pLE25 mRNA accumulated to much higher levels in developing seeds than in drought-stressed vegetative organs. pLE4 mRNA accumulated predominantly in drought-stressed leaves. The similarities and differences in the accumulation characteristics of these two mRNAs indicates that more than one mechanism exists for the regulation of their corresponding genes.     

Autoreceptor Regulation of Glutamate and Aspartate Release from Slices of the Hippocampal CA1 Area

Slices of hippocampal area CA1 were employed to test the hypothesis that the release of glutamate and aspartate is regulated by the activation of excitatory amino acid autoreceptors. In the absence of added Mg2+, N-methyl-D-aspartate (NMDA)-receptor antagonists depressed the release of glutamate, aspartate, and gamma-aminobutyrate evoked by 50 mM K+. Conversely, the agonist NMDA selectively enhanced the release of aspartate. The latter action was observed, however, only when the K+ stimulus was reduced to 30 mM. Actions of the competitive antagonists 3-[(+/- )-2-carboxypiperazin-4-yl]-propyl-l-phosphonic acid (CPP) and D-2-amino-5-phosphonovalerate (D-AP5) differed, in that the addition of either 1.2 mM Mg2+ or 0.1 microM tetrodotoxin to the superfusion medium abolished the depressant effect of CPP without diminishing the effect of D-AP5. These results suggest that the activation of NMDA receptors by endogenous glutamate and aspartate enhances the subsequent release of these amino acids. The cellular mechanism may involve Ca2+ influx through presynaptic NMDA receptor channels or liberation of a diffusible neuromodulator linked to the activation of postsynaptic NMDA receptors. (RS)-alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid, a selective quisqualate receptor agonist, and kainate, an agonist active at both kainate and quisqualate receptors, selectively depressed the K(+)-evoked release of aspartate. Conversely, 6-cyano-7-nitro-quinoxaline-2,3-dione, an antagonist active at both quisqualate and kainate receptors, selectively enhanced aspartate release. These results suggest that glutamate can negatively modulate the release of aspartate by activating autoreceptors of the quisqualate, and possibly also of the kainate, type. Thus, the activation of excitatory amino acid receptors has both presynaptic and postsynaptic effects.     

The Lepocreadiidae (Digenea) of fishes from the north-east Atlantic: Profundivermis intercalarius n. g., n. sp. from the marine fish Coryphaenoides (Nematonurus) armatus (Hector) (Macrouridae) from the Porcupine Abyssal Plain

A new genus and species, Profundivermis intercalarius, is described from the deep-sea fish Coryphaenoides (Nematonurus) armatus from 4,850 m deep on the Porcupine Abyssal Plain, NE Atlantic. The genus is characterized by an inter-testicular ovary and is the only member of the subfamily Lepidapedinae to show this feature. The relationships of the members of the subfamily are analysed phylogenetically. Members of the subfamily are often found in deep-sea gadiforms.     

The Opecoelidae (Digenea) of sparid fishes of the western Mediterranean. V.Allopodocotyle Pritchard, 1966

Allopodocotyle pedicellata (Stossich, 1887) is redescribed fromSparus aurata from off Corsica and off Provence, France andA. jaffensis (Fischthal, 1980) is redescribed fromSparus pagrus, Dentex dentex andPagellus erythrinus from off Corsica. The status of the genus and these two species is briefly discussed.

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Résumé Allopodocotyle pedicellata (stossich, 1887) est redécrit chezSparus aurata des côtes de la Corse et de la Méditerranée française.A. jaffensis (Fischthal, 1980) est redécrit à partir d'exemplaires provenant deSparus pagrus, Dentex dentex et Pagellus erythrinus des côtes de la Corse. Le statut du genre et de ces deux espèces est discuté.

     

Estimation of minimum alveolar concentration (MAC) for halothane, enflurane and isoflurane in spontaneously breathing guinea pigs

MAC for halothane, enflurane and isoflurane was determined in guinea pigs (Cavia porcellus) exposed to constant anesthetic concentrations (2.5 hours each) in a flow-through glass chamber. The following values were obtained (N = 8 for each anesthetic): 1.01 +/- 0.03 vol% for halothane, 2.17 +/- 0.04 vol% for enflurane, and 1.15 +/- 0.05 vol% for isoflurane. In guinea pigs, MAC for halothane and enflurane are similar to those reported for other rodents, while MAC for isoflurane is lower. The data indicate that guinea pigs possibly are more susceptible to isoflurane's anesthetic actions than other rodents.     

Information from e.x.a.f.s. spectroscopy on the structures of different forms of molybdenum in xanthine oxidase and the catalytic mechanism of the enzyme.

In isolated perfused rat hearts, epidermal growth factor (EGF; 15 nM) increased cellular cyclic AMP (cAMP) content by 9.5-fold. In rat cardiac membranes, EGF also stimulated adenylate cyclase activity in a dose-dependent manner, with maximal stimulation (35% above control) being observed at 10 nM-EGF. Half-maximal stimulation of adenylate cyclase was observed at 40 pM-EGF. Although the beta-adrenergic-receptor antagonist propranolol markedly attenuated the isoprenaline-mediated increase in cAMP content of perfused hearts and stimulation of adenylate cyclase activity, it did not alter the ability of EGF to elevate tissue cAMP content and stimulate adenylate cyclase. The involvement of a guanine-nucleotide-binding protein (G-protein) in the activation of adenylate cyclase by EGF was indicated by the following evidence. First, the EGF-mediated stimulation of adenylate cyclase required the presence of the non-hydrolysable GTP analogue, guanyl-5'-yl-imidodiphosphate (p[NH]ppG). Maximal stimulation was observed in the presence of 10 microM-p[NH]ppG. Secondly, in the presence of 10 microM-p[NH]ppG, the stable GDP analogue guanosine 5'-[beta-thio]diphosphate at a concentration of 10 microM blocked the stimulation of the adenylate cyclase by 1 nM- and 10 nM-EGF. Third, NaF + AlCl3-stimulated adenylate cyclase activity was not altered by EGF. The ability of EGF to stimulate adenylate cyclase was not affected by pertussis-toxin treatment of cardiac membranes. However, in cholera-toxin-treated cardiac membranes, when the adenylate cyclase activity was stimulated by 2-fold, EGF was ineffective. Finally, PMA by itself did not alter the activity of cardiac adenylate cyclase, but abolished the EGF-mediated stimulation of this enzyme activity. The experimental evidence in the present paper demonstrates, for the first time, that EGF stimulates adenylate cyclase in rat cardiac membranes through a stimulatory GTP-binding regulatory protein, and this effect is manifested in elevated cellular cAMP levels in perfused hearts exposed to EGF.     

Differential susceptibilities of isolated hamster lung cell types to amiodarone toxicity

Treatment of cardiac dysrhythmias with the iodinated benzofuran derivative amiodarone (AM) is limited by pulmonary toxicity. The susceptibilities of different lung cell types of male Golden Syrian hamsters to AM-induced cytotoxicity were investigated in vitro. Bronchoalveolar lavage and protease digestion to release cells, followed by centrifugal elutriation and density gradient centrifugation, resulted in preparations enriched with alveolar macrophages (98%), alveolar type II cells (75-85%), and nonciliated bronchiolar epithelial (Clara) cells (35-50%). Alveolar type II cell and Clara cell preparations demonstrated decreased viability (by 0.5% trypan blue dye exclusion) when incubated with 50 microM AM for 36 h, and all AM-treated cell preparations demonstrated decreased viability when incubated with 100 or 200 microM AM. Based on a viability index ((viability of AM-treated cells/viability of controls) x 100%), the Clara cell fraction was significantly (p<0.05) more susceptible than all of the other cell types to 50 microM AM. However, AM cytotoxicity was greatest (p<0.05) in alveolar macrophages following incubation with 100 or 200 microM AM. There was no difference between any of the enriched cell preparations in the amount of drug accumulated following 24 h of incubation with 50 microM AM, whereas alveolar macrophages accumulated the most drug during incubation with 100 microM AM. Thus, the most susceptible cell type was dependent on AM concentration. AM-induced cytotoxicity in specific cell types may initiate processes leading to inflammation and pulmonary fibrosis.     

Molecular cloning and characterization of an alpha1,3 fucosyltransferase, CEFT-1, from Caenorhabditis elegans

We report on the identification, molecular cloning, and characterization of an alpha1,3 fucosyltransferase (alpha1,3FT) expressed by the nematode, Caenorhabditis elegans . Although C. elegans glycoconjugates do not express the Lewis x antigen Galbeta1-- >4[Fucalpha1-->3]GlcNAcbeta-->R, detergent extracts of adult C.elegans contain an alpha1,3FT that can fucosylate both nonsialylated and sialylated acceptor glycans to generate the Lexand sialyl Lexantigens, as well as the lacdiNAc-containing acceptor GalNAcbeta1-->4GlcNAcbeta1-- >R to generate GalNAcbeta1-->4 [Fucalpha1-->3]GlcNAcbeta1-->R. A search of the C.elegans genome database revealed the existence of a gene with 20-23% overall identity to all five cloned human alpha1,3FTs. The putative cDNA for the C.elegans alpha1,3FT (CEFT-1) was amplified by PCR from a cDNA lambdaZAP library, cloned, and sequenced. COS7 cells transiently transfected with cDNA encoding CEFT-1 express the Lex, but not sLexantigen. The CEFT-1 in the transfected cell extracts can synthesize Lex, but not sialyl Lex, using exogenous acceptors. A second fucosyltransferase activity was detected in extracts of C. elegans that transfers Fuc in alpha1,2 linkage to Gal specifically on type-1 chains. The discovery of alpha-fucosyltransferases in C. elegans opens the possibility of using this well-characterized nematode as a model system for studying the role of fucosylated glycans in the development and survival of C.elegans and possibly other helminths.