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We have shown that IgG hydrolysed by Schistosoma mansonischistosomula inhibited various macrophage functions, especially phagocytosis and anti-schistosome cytotoxicity. Here we show that a tripeptide, Thr 289-Lys-Pro 291, of the second constant domain of human immunoglobulin G (peptide 286–292) reproduced the inhibitory effect of a total hydrolysate. Indeed the β-glucuronidase release from IgE-anti-IgE-stimulated rat and human macrophages decreased and its intracellular level did not rise after a prior incubation of the cells with Thr-Lys-Pro (500 nmol/ml). Moreover, the cell migration as well as the superoxide anion O −2generation were 50–80% reduced by the tripeptide. These results suggest that a single peptide set may be responsible for the decrease of the macrophage functions at the early stage of the parasite infection in the mammalian host. The pharmacologic properties of this tripeptide are under investigation.

Cultured adult rat hepatocytes were treated daily with 3.2 mM phenobarbital (PB) in order to study its effect on the expression of cytosolic glutathione S-transferase isoenzymes. Glutathione S-transferase (GST) activities, using 1-chloro-2,4-dinitrobenzene and 1,2-dichloro-4-nitrobenzene as substrates, were increased when PB was present in the culture medium. After purification and separation of GST on glutathione Sepharose 6 B and reversed-phase HPLC, respectively, it was observed in vitro that PB caused an increase in the relative amounts of subunits 1, 3 and 7 compared to subunits 2 and 4. Using Northern blot technique, elevated levels of GST subunit 1/2 and 7 mRNA were measured, after addition of PB to the cultures.

The transmembrane distribution of galactolipids has been determined in spinach thylakoid inside-out vesicles obtained by fragmentation in a Yeda Press followed by partition in an aqueous dextran-polyethylene glycol two-phase system. Using the lipase from Rhizopus arrhizusto digest selectively the galactolipids in the outer monolayer of the membrane, we have found the molar outside/inside distribution to be 42±1/58±1 for monogalactosyldiacylglycerol (MGDG) and 82±0.2/18±0.2 for digalactosyldiacylglycerol (DGDG). As expected, the transmembrane distribution of galactolipids in inside-out vesicles was the opposite to that found in intact thylakoids which, under similar conditions, was found to be 62/38 for MGDG and 20/80 for DGDG. The reliability of the enzymatic approach to determine the transmembrane distribution and the relative arrangement of acyl lipids in the thylakoid membrane are discussed.

Heterologous expression of the yeast triple Mep mutant has enabled the first molecular characterization of AMT/MEP family members in an ectomycorrhizal fungus. External hyphae, which play a key role in nitrogen nutrition of trees, are considered as the absorbing structure of the ectomycorrhizal symbiosis and therefore molecular studies on ammonium transport in hyphae are urgently needed. The kinetic properties of AMT2 and AMT3 from Hebeloma cylindrosporumwere studied in Saccharomyces cerevisiae. Expression of HcAmts in the yeast triple Mep mutant restored ammonium retention within cells. The HcAmts did not complement the ammonium sensing defect phenotype of Mep2Δ cells during pseudohyphal differentiation. Northern blot analysis in H. cylindrosporumshowed that the HcAMTswere up‐regulated upon nitrogen deprivation and down‐regulated by ammonium.

We observed recently1 that placental leptin is markedly increased in preeclampsia. Since this disorder is associated with vascular disorders, we have tested the hypothesis that hypoxia regulates leptin expression. We show that hypoxia increased leptin mRNA and secretion in trophoblast‐derived BeWo cells. This effect was mediated through leptin promoter activation. 5′ deletion analysis allowed us to delineate two regions containing 1.87 kb and 1.20 kb of the promoter which conferred respectively high and low responsiveness to hypoxia. These data indicate that leptin is up‐regulated by hypoxia through a transcriptional mechanism likely to involve distinct hypoxia‐responsive cis‐acting sequences on the promoter.

In response to external amino acids, the permease‐like sensor Ssy1 of Saccharomyces cerevisiaeactivates a pathway leading to transcriptional induction of several permease genes including AGP1and PTR2. We previously reported that AGP1induction requires Grr1, the F‐box protein part of the SCFGrr1ubiquitin–ligase complex. We show here that ubiquitin, other components of SCFGrr1and the ubiquitin‐conjugating enzyme Cdc34 are essential for AGP1and PTR2induction. This suggests that transduction to these genes of the amino acid signal generated by Ssy1 involves an SCFGrr1‐catalysed ubiquitination step.

We analyzed fatty acid biosynthesis in Chang and ZR‐75‐1 cells. Both cell lines could desaturate and further elongate substrates for Δ‐5 desaturase. ZR‐75‐1 but not Chang cells showed Δ‐6 desaturation of 18:2n‐6, 18:3n‐3, 24:4n‐6 and 24:5n‐3. In both cell lines, the mRNA abundance can be related to Δ‐5 or Δ‐6 fatty acid desaturase activities. These results suggest that desaturase genes could have, at least in part, independent control mechanisms and that Δ‐6 desaturase impairment is not specific to any particular step of the fatty acid metabolic pathways, which may diminish the rationale for the existence of at least two distinct enzymes.

In response to external amino acids, the permease-like sensor Ssy1 of Saccharomyces cerevisiaeactivates a pathway leading to transcriptional induction of several permease genes including AGP1and PTR2. We previously reported that AGP1induction requires Grr1, the F-box protein part of the SCF Grr1ubiquitin–ligase complex. We show here that ubiquitin, other components of SCF Grr1and the ubiquitin-conjugating enzyme Cdc34 are essential for AGP1and PTR2induction. This suggests that transduction to these genes of the amino acid signal generated by Ssy1 involves an SCF Grr1-catalysed ubiquitination step.

Diacylglycerol acyltransferase has a universal role in catalyzing the acyl‐CoA‐dependent formation of triacylglycerol in microorganisms, animals and plants. Acylation stimulating protein, from human blood, is known to enhance diacylglycerol acyltransferase activity and triacylglycerol biosynthesis in human adipocytes. In the current study, acylation stimulating protein was also shown to enhance diacylglycerol acyltransferase activity in microsomes from cell suspension cultures of oilseed rape. Enzyme stimulation occurred over the pH range of 6–9 but the degree of stimulation decreased with increasing ionic strength at pH 7.4. Varying acyl‐CoA concentration did not affect the degree of stimulation. Membranes from triacylglycerol producing cells in plants and humans may have similar binding sites for acylation stimulating protein which have been preserved during molecular evolution. The results suggest that human acylation stimulating protein may be useful in modifying lipid biosynthesis in plants.

Four years after disclosure of the full yeast genome sequence, a series of resources including tens of thousands of mutant strains, plasmids bearing isolated genes and disruption cassettes are becoming publicly available. Deletions of each of the 6000 putative yeast genes are being screened systematically for dozens of phenotypic traits. In addition, new global approaches such as DNA hybridization arrays, quantitative proteomics and two‐hybrid interactions are being steadily improved. They progressively build up an immense computation network of billions of data points which will, within the next decade, characterize all molecular interactions occurring in a simple eukaryotic cell. In this process of acquisition of new basic knowledge, an international community of over 1000 laboratories cooperates with a remarkable willingness to share projects and results.

Inside‐out inner mitochondrial membranes free of matrix proteins were isolated from purified potato tuber (Solanum tuberosumL.) mitochondria and incubated with [γ‐32P]ATP. Proteins were separated by SDS–PAGE and visualized by autoradiography. Phosphorylation of inner membrane proteins, including ATPase subunits, was strongly inhibited by the phosphoprotein phosphatase inhibitor NaF. We propose that an inner membrane phosphoprotein phosphatase is required for activation of the inner membrane protein kinase. When prelabelled inner membranes were incubated in the absence of [γ‐32P]ATP, there was no phosphoprotein dephosphorylation unless a soluble matrix fraction was added. This dephosphorylation was inhibited by NaF, but not by okadaic acid. We conclude that the mitochondrial matrix contains a phosphoprotein phosphatase that is responsible for dephosphorylation of inner membrane phosphoproteins.

The cDNA from activated mutants of the homologous transcription factors Pdr1p and Pdr3p was used to screen DNA microarrays of the Saccharomyces cerevisiaecomplete genome. Twenty‐six overexpressed targets of the PDR1–3and/or PDR3–7mutants were identified. Twenty‐one are new targets, the majority of which are of unknown function. In addition to well known ABC transporters, these targets appear to be involved in transport or in membrane lipids and cell wall biosyntheses. Several of the targets seem to contribute to the cell defence against a variety of stresses. Pdr1p and Pdr3p do not act similarly on all targets. Unexpectedly, the expression of 23 other genes appeared to be repressed in the PDR1–3and/or PDR3–7mutants. In contrast to the majority of the activated genes, none of the repressed genes contains pleiotropic drug resistance binding sites in their promoter.

In an attempt to create the possibility of stable, long acting, intravascular anticoagulation, low molecular weight heparin was modified by introducing a sulfhydryl group into the molecule (LMWH‐SH). Human erythrocytes were covalently grafted with LMWH‐SH by the use of a heterobifunctional coupling reagent which reacts with the SH group of LMWH‐SH and surface exposed amino groups of erythrocytes now called ‘heparinocytes’ (HC). HC were morphologically indistinguishable from untreated erythrocytes and displayed identical osmotic resistance. The functionality of HC was analyzed by classical coagulation tests in which they dose dependently inhibited clot formation. HC were also functional in recalcified whole blood inhibiting thrombin formation as assessed by the cleavage of the chromogenic substrate S‐2238. The system appears applicable as a potential autologous, long‐term anticoagulant treatment or prophylaxis.

Hemorphin generation by mice peritoneal macrophages has been recently reported, nevertheless no conclusive data exist to localize clearly the macrophage proteolytic activity implicated in their generation. Because lysosomes are believed to be the main site of degradation in the endocytic pathway, we have studied their potential implication in the generation of hemorphins from hemoglobin. When this protein is submitted to purified rat liver lysosomes, an early generation of hemorphin‐7‐related peptides, detected by a radioimmunoassay, was observed. These peptides seemed to be relatively stable during the first hours of hydrolysis.

The human N‐acetylglucosaminyltransferase I gene was introduced in the genome of Trichoderma reeseistrain VTT‐D‐80133. Expression was studied after induction from the cellobiohydrolase I promoter. Successful in vivo transfer of GlcNAc was demonstrated by analyzing the neutral N‐glycans which were synthesized on cellobiohydrolase I. Final proof of the formation of GlcNAcMan5GlcNAc2was obtained by NMR analysis.

In lower and higher eukaryotes, a family of tightly related proteins designated eRF1 (for eukaryotic release factor 1) catalyses termination of protein synthesis at all three stop codons. The human genome contains four eRF1 homologous sequences localised on chromosomes 5, 6, 7 and X. We report here the cloning and the structural analysis of the human eRF1 gene family. It appears that the gene located on chromosome 5 alone is potentially functional, whereas the other three sequences resemble processed pseudogenes. This is the first description of the structural organisation of the human eRF1 gene, which has been remarkably conserved during evolution and which is essential in the translation termination process.

We have investigated the involvement of human apolipoprotein A‐IV (apoA‐IV) in gastric acid secretion and ulcer formation in recently generated apoA‐IV transgenic mice. Compared to control littermates, transgenic animals showed a gastric acid secretion decreased by 43–77% whereas only slight variations were observed in the different cell population densities within the gastric mucosa. In addition, no variation in gastrin levels was observed. Transgenics were protected against indomethacin‐induced ulcer formation, with lesions diminishing by 45 to 64% compared to controls. These results indicate that endogenous apoA‐IV expression can regulate gastric acid secretion and ulcer development.

Regulation of multidrug resistance‐associated protein (MRP2) expression in response to dexamethasone (DEX) was analyzed using mainly primary rat hepatocytes. Enhanced levels of MRP2 mRNAs associated with increased amounts of a 190 kDa MRP2 were found in cultured DEX‐treated hepatocytes; similarly, administration of DEX to rats (100 mg/kg, i.p.) led to a marked increase of hepatic amounts of MRP2 mRNAs. Maximal induction of MRP2 expression in DEX‐treated primary hepatocytes was reached with 10−5M DEX, a concentration higher than that (10−7M) required for maximal up‐regulation of tyrosine aminotransferase (TAT), a typical glucocorticoid receptor‐regulated enzyme. In addition, the anti‐glucocorticoid compound RU486 failed to inhibit MRP2 induction caused by DEX whereas it fully blocked that of TAT. These findings therefore demonstrate that DEX is a potent inducer of MRP2 expression in rat hepatocytes through a mechanism that seems not to involve the classical glucocorticoid receptor pathway.

The vast majority of genes of maize, rice, barley and wheat are contained in long gene‐rich regions (collectively called the ‘gene space’) separated by long gene‐empty regions. The gene space covers a narrow, 0.8–1.6%, GC range, possibly because of the presence of abundant transposons. Here we report that the gene space is not an exclusive property of Gramineae, because it also exists in the large genome of pea (5000 Mb). Moreover, the gene space is not just dependent upon genome size, since a gene space is found in rice (415 Mb), but not in Arabidopsis(120 Mb), nor in two other plants investigated in the present work, date palm (250 Mb) and tomato (1000 Mb).

The double‐stranded RNA‐specific adenosine deaminases ADAR1 and ADAR2 convert adenosine (A) residues to inosine (I) in messenger RNA precursors (pre‐mRNA). Their main physiological substrates are pre‐mRNAs encoding subunits of ionotropic glutamate receptors or serotonin receptors in the brain. ADAR1 and ADAR2 have similar sequence features, including double‐stranded RNA binding domains (dsRBDs) and a deaminase domain. The tRNA‐specific adenosine deaminases Tad1p and Tad2p/Tad3p modify A 37 in tRNA‐Ala1of eukaryotes and the first nucleotide of the anticodon (A 34) of several bacterial and eukaryotic tRNAs, respectively. Tad1p is related to ADAR1 and ADAR2 throughout its sequence but lacks dsRBDs. Tad1p could be the ancestor of ADAR1 and ADAR2. The deaminase domains of ADAR1, ADAR2 and Tad1p are very similar and resemble the active site domains of cytosine/cytidine deaminases.

Upon subcellular fractionation of (murine) Friend erythroleukaemic cells (FELCs), purified plasma membranes were identified by their high enrichment in specific marker enzymes and typical plasma membrane lipids. When FELCs were incubated for short periods with 32Pibefore cell fractionation, the lipid‐bound radioactivity was almost exclusively present in phosphatidylinositol‐4‐phosphate (DPI) and phosphatidylinositol‐4,5‐bisphosphate (TPI), and its distribution closely matched that of the plasma membrane markers. In addition, purified plasma membranes actively incorporated 32P from [γ‐32P]ATP into polyphosphoinositides, and the specific activities of the involved kinases were again mostly enriched in the plasma membrane fraction.

Previous studies, by using Northern blotting analyses, showed that phenobarbital (PB) affects the steady-state mRNA levels of glutathione S-transferase (GST) subunits 12, 34and 7 in both conventional cultures of adult rat hepatocytes and co-cultures, with rat liver epithelial cells [Vandenberghe et al., 1989, FEBS Lett. 251, 59–64; Morel et al., 1989, FEBS Lett. 258, 99–102]. To determine whether PB acts at the transcriptional level, nuclear ‘run-on’ experiments using cDNA probes hybridizing to GST subunits 12, 34and 7 mRNA were performed on purified nuclei isolated from control and PB treated hepatocytes seeded under conventional and co-culture conditions. Data from this study demonstrate that the increase in steady-state mRNA levels observed in both conventional culture and co-culture after 4 days PB exposure results from an increased transcriptional activity or the GST genes. However, a substantial increase in steady-state mRNA levels in the absence of a commensurate increase in transcriptional activity at 12 days of co-culture, indicates that the barbiturate has also a stabilizing effect in vitro on the GST mRNAs.

The specificity of the sialidase activity present in rat kidney cortex (12 000 × gpellet) was studied with various tritiated oligosaccharidic substrates: (i) αNeuAc2 → 3βGall → 4Glc-itol[ 3H], αNeuAc2 → 6βGall → 4Glc-itol[ 3H] and αNeuAc2 → 8αNeuAc2 → 3βGall → 4Glc-itol[ 3H] from bovine colostrum; (ii) α-NeuAc2 → 6βGall → 4βGlcNAc-itol[ 3H], αNeuAc2 → 3βGal1 → 4βGlcNAcl → 2αManl → 3βMan1 → 4GlcNAc-itol[ 3H]. αNeuAc2 → 6βGall → 4βGlcNAcl → 2αManl α 3(βGall → 4GlcNAcl → 2αManl → 6)βManl → 4GlcNAc-itol [ 3H]et αNeuAc2 → 6βGall → 4βGlcNAcl → 2αManl-3(αNeuAc2 → 6βGall → 4βGlcNAcl → 2αManl → 6)βManl 4GlNAc-itol[ 3H] isolated from the urine of a patient with mucolipidosis I. The enzyme cleaves α2 → 3 and α2 → 8 linkages at a greater rate than the α2 → 6 bonds. Its activity decreases with the length of the oligosaccharidic chain. Substitution of a glucose moiety by Nacetylglucosamine results in diminished activity. The specificity of rat kidney sialidase differs from that reported for other mammalian of viral sialidases.

The phospholipases A 2from porcine pancreas and Vipera russelliand the phospholipase D from Streptomyces chromofuscushave been used to determine the transmembrane distribution of phosphatidylglycerol (PG) and phosphatidylcholine (PC) in prothylakoid and thylakoid membranes from oat. Both phospholipids were found to be asymmetrically distributed. The molar outside/inside distribution was 70 ± 5/30 ± 5 for PG in both types of membranes. Concerning PC, this ratio was 50 ± 10/50 ± 10 and 65 ± 10/35 ± 10 for prothylakoid and thylakoid membranes, respectively. These results suggest that chlorophyll-protein complexes are unlikely to be involved in the origin and stabilization of the asymmetric transmembrane distribution of phospholipids. The possible origin of this distribution is discussed.

Pancreatic secretory factor (PSF), an efficient pancreatic secretagogue recently isolated from the venom of Heloderma suspectumis shown to exert phospholipase A 2activity towards phosphatidylcholine. This activity is strictly dependent on calcium (apparent Ka40 nM) and has an optimum pH around 9. At pH 7.4 and in the presence of calcium, PSF retains 40% of its phospholipase A 2activity. These results are compared to the calcium dependency of the secretory effect of PSF on rat pancreatic acini. Taken collectively, the present data on PSF suggest that a similar endogenous phospholipase A 2activity might be involved in the late steps of stimulus-secretion coupling in the exocrine pancreas.

We previously reported the production of a fused snake neurotoxin composed of protein A and erabutoxin ain E. coli[1]. The hybrid had much lower toxicity and affinity for the acetylcholine nicotinic receptor than natural erabutoxin. By treating the hybrid with cyanogen bromide we generated a toxin which was purified in a single step by RP-HPLC. This compound, produced in a good yield, recovered all properties of native erabutoxin a, implying that the lower toxic activities of the hybrid were due to the bulky protein A and not to an incorrect folding of the toxin. This work serves as a basis for future studies of toxin-receptor interactions using engineered toxin mutants.

The lipocyte is an important source of laminin in the normal liver. We have investigated the expression of the 3 chains of laminin in isolated rat lipocytes. Both B 1and B 2chains, but not A, were found in medium from 5-day-old lipocyte primary cultures by immunoblotting and immunoprecipitation of 35S-labeled proteins after reducing SDS-polyacrylamide gel electrophoresis. An additional polypeptide of Mr=380 000 was identified by immunoprecipitation. Under non-reducing conditions only one Mr=900 000 band was revealed. High levels of B 1and B 2mRNAs were also demonstrated in 5-day-old cultured lipocytes while at the time of seeding, only B 2chain mRNAs were clearly detectable. A chain mRNA was constantly absent. These results suggest that lipocytes produce a variant form of laminin in primary culture and that the Mr=380 000 polypeptide could be unrelated to the A chain of laminin.

Three spinach chloroplast envelope membrane preparations (i.e. whole, outer and inner membranes) were incubated in the presence of [γ- 32P]ATP. After lipid extraction and separation by TLC, four main phosphorylated lipids were detected by autoradiography in whole envelope preparations. These phospholipids were identified by comparing their Rf with that of lipid markers and by a deacylation procedure. They were found to be phosphatidic acid (PA) and lyso-PA, l-α-phosphatidyl-inositol 4-monophosphate (PIP) and lyso-PIP. These lipids were not equally distributed in the outer and inner envelope membranes. Chloroplast envelope membranes were verified not to be contaminated by plasma membranes. It is concluded that lipid kinase activities are associated with spinach chloroplast envelope membranes.

α2,‐Adrenergic receptors in calf retina membranes can be specifically labeled with the tritiated agonist p‐azido[3H]clonidine. Saturation binding in the dark occurs with high affinity (1.3 ± 0.3 nM) to a single class of sites (1122 ± 67 fmol/mg protein). Irradiation of the membrane‐bound radioligand results in the labeling of a peptide band with an apparent size of 65 kDa and a characteristic pharmacological profile for an α2‐adrenergic receptor. The carbohydrate moieties of the α2‐receptor are characterized by lectin affinity chromatography and glycosidase treatment. The Nonidet P‐40‐solubilized, p‐azido[3H]clonidine‐labeled receptors are completely retained by Con A‐ as well as WGA‐Sepharose columns. Neuraminidase, α‐mannosidase and TFMS do not affect the electrophoretic mobility of the receptor on SDS‐PAGE whereas endoglycosidase F reduces the apparent size to 45 kDa.

Two different isoforms of subunit VIIa have been found in cytochrome coxidase isolated from human skeletal muscle. The first 22 residues of the N‐terminal amino acid sequences showed 5 differences. Our results provide the first conclusive evidence for the existence of cytochrome coxida isoenzymes in man. Since the two cytochrome coxidase isoforms were both present in skeletal muscle tissue, though not necessarily in the same cell type, this suggests that human cytochrome coxidase isoforms are not strictly tissue‐specific. These findings may have important implications for the elucidation of genetic diseases in man in which a deficiency of cytochrome coxidase is restricted to certain tissues.

Venom of the Australian tiger snake, Notechis scutatus scutatuswas fractionated by conventional ion‐exchange chromatography. The fraction containing notexin, a well‐known single‐chain toxic phospholipase A2, was further purified by reverse‐phase high‐performance liquid chromatography. Two main components were isolated and the major one corresponded to notexin. The other component, designated as notechis Ns, was an isofonn of notexin. Notechis Nsand notexin possessed similar in vitro esterase activity, in vitro neuromuscular activity and in vivo lethality. Amino acid composition and sequence of the Staphylococcus aureusV8‐protease peptides demonstrated that primary structures of notechis Nsand notexin differed from each other by a single substitution amongst 119 amino acids: Lys → Arg at position 16.

Protegrins are members of a family of five Cys‐rich naturally occurring cationic antimicrobial peptides. The NMR solution structure of protegrin‐1 (PG‐1) has been previously determined as a monomeric β‐hairpin both in water and in dimethylsulfoxide solution. Protegrins are bactericidal peptides but their mechanism of action is still unknown. In order to investigate the structural basis of their cytotoxicity, we studied the effect of lipid micelles on the structure of PG‐1. The NMR study reported in the present work indicates that PG‐1 adopts a dimeric structure when it binds to dodecylphosphocholine micelles. Moreover, the amide proton exchange study suggests the possibility of an association between several dimers.

Pure ethylenediaminetetraacetic acid tetrasodium salt (EDTA · Na4) in water showed a pH‐dependent change of optical density detected in the ultraviolet region. The most important change was found between pH 4 and 8, corresponding to the deprotonation of the third ionizable group having a pK of 6.2. The absorbance change was reversible and depended on the addition/removal of only 1 proton equivalent. The presence of supramolecular aggregates was suggested by size‐exclusion chromatography, dialysis and cryo‐electronmicroscopy. The molecular weight of EDTA supramolecular aggregates was 10–15,000 and 8–14,000, as determined by gel chromatography and dialysis, respectively. Cryo‐electronmicroscopy revealed structures of 2–4 nm in diameter.

Tau proteins are the basic components of filaments that accumulate within neurons during neurofibrillary degeneration, a degenerating process with disease‐specific phenotypes. This specificity is likely to be sustained by both phosphorylation state and isoform content of tau aggregates that form neuronal inclusions. In the present study, characterization of tau isoforms involved in neurofibrillary degeneration in Alzheimer's disease, Pick's disease, corticobasal degeneration and progressive supra‐nuclear palsy was performed. Both analyses by immunoblotting using specific tau antibodies and cell transfection by tau isoform cDNAs allowed us to demonstrate the aggregation of (1) the six hyperphosphorylated tau isoforms in Alzheimer's disease, (2) tau isoforms without exon 10‐encoding sequence in Pick's disease and (3) hyperphosphorylated exon 10‐tau isoforms in corticobasal degeneration and progressive supranuclear palsy. Thus, neurofibrillary degeneration phenotypes are likely to be related to the phosphorylation of different combinations of tau isoforms (with and/or without exon 10‐encoding sequence) in subpopulations of neurons.

Helodermin, a newly isolated peptide from the venom of Gila monster (Heloderma suspectum) was shown to stimulate the adenylate cyclase activity of rat pancreatic membranes as effectively as secretin and VIP. It also increased cyclic AMP levels and inhibited [125I]VIP binding in rat pancreatic acini. Finally, helodermin activated adenylate cyclase in membranes from rat heart, rat brain, and human heart, showing properties analogous yet distinct from those of secretin, VIP and PHI.

Pancreatic secretory factor (PSF), a 17.5‐kDa protein purified from the venom of Gila monster (Heloderma suspectum), stimulated amylase secretion from dispersed rat pancreatic acini more efficiently than CCK‐8, bombesin, carbachol and secretin, and without increasing 45Ca2+efflux and cyclic AMP levels. The secretory action was dependent on the presence of extracellular calcium and was additive to the secretion induced by agents acting via cyclic AMP or via Ca2+efflux.

A combination of three HPLC procedures applied to the venom of Gila monster (Heloderma suspectum) has led to the purification to homogeneity of two bioactive components: (i) a 17.5 kDa protein, isolated on the basis of its potent secretory effect on dispersed rat pancreatic acini, was accordingly designated PSF (pancreatic secretory factor); (ii) a 5.9‐kDa peptide, designated helodermin, was purified on the basis of its ability to stimulate adenylate cyclase in rat pancreatic membranes. PSF was unable to activate adenylate cyclase and, conversely, helodermin was devoid of secretory action.

Spinach chloroplasts are known to contain calmodulin and to display an envelope-bound ATPase activity. This activity, stimulated by 0.15 mM Ca 2+and 5 mM Mg 2+, is further enhanced by calmodulin. The apparent Kmfor ATP was 0.55 mM. The enzyme was especially sensitive to NH 4VO 3, SbCl 3, LaCl 3and oligomycin. An attempt to isolate the ATPase by calmodulin-Sepharose affinity chromatography was successful. The EGTA-eluted fraction contained 2 proteins out of the 21 proteins separated previously by isoelectric focussing [(1983) Biochim. Acta 722, 226—333] and exhibited an ATPase activity.

It is shown that investigating the lateral motion of lipids in biological membranes can provide useful information on membrane lateral organization. After labeling membranes with extrinsic or intrinsic lipophilic fluorescent probes, fluorescence recovery after photobleaching experiments strongly suggests that specialized cells like spermatozoa, eggs and epithelia exhibit surface membrane regionalization or macrocompartmentation and that lateral microheterogeneities or lipid microdomains exist in the plasma membrane of many cellular systems.

Specific receptors for atrial natriuretic factor were studied in purified glomeruli, proximal tubules, thick ascending limbs of Henle's loops and collecting ducts from dog kidney. Glomeruli contain the highest concentration of receptor sites (p K= 9.9, Bmax= 200 fmolmgprotein), followed by collecting ducts (p K= 9.4, Bmax= 150 fmolmg). Low levels of receptor sites were also detectable in thick ascending limbs of Henle's loops (p K= 9.4, Bmax= 36 fmolmg) while proximal tubules were completely devoid of specific binding sites. These results indicate that the glomeruli appear to be the primary site of interaction of artrial natriuretic factor in kidney cortex but that it might also act in the medulla on lower nephron tubular function.