Presence de pollens d'Hamamelis (Hamamelidaceae,Angiospermae) dans le pliocene du Sud de la France

Pollen-analysis shows the presence of the genus Hamamelis in the pliocene flora of southern France. It contributesto the knowledge of the past distribution of taxa which are now extinct in western Europe.     

L'espece Pecopteris simoni (Zeiller, 1886–1888)sunonyme posterieur de Palaeoweichselia defrancei (Brongniart, 1828)

Recent examination of the type specimen of Pecopris simoni ZEILLER (1) leads to the conclusion of the identityof that species with Palaeoweichselia defrancei (BRONGNIART) (2), which is also confirmed by the stratigraphic occurence.     

Carbohydrate-peptide linkage in glycoproteins

The secondary structure of the peptide segment around the carbohydrate-peptide linkage in glycoproteins was predicted by using the Chou and Fasman determination. Such a study was carried out for 9 O-glycosidically linkages and 28 N-glycosidically linkages. In the case of O-glycosidically linkages, the residue Ser or Thr involved in the linkage always belongs to a β-turn. In the case of N-glycosidically linkages, 19 out of the 28 Asn studied belong to a β-turn. A predicted determination concerning the whole protein moiety of 9 glycoproteins in order to obtain some information concerning the spatial organization of the entire glycoprotein was carried out also. It seems that carbohydrate moiety takes place outside the glycoprotein.     

Apports de la palynologie a la connaissance du Pliocène du Roussillon (sud de la France)

The present study illustrates clearly how pollen analysis may be applied to stratigraphy from a botanical point of view. Within a chronologically reliable frame (Middle Pliocene for the marine deposits on the basis of Foraminifera record; two subzones for continental deposits on the basis of Mammals record: Hautimagne for Terrats fauna, Sète for Serrat-d'en-Vacquer fauna), palynology provides a good stratigraphical boundary: the extinction of the Taxodiaceae. In a remblayage area, it is established that a continental level is not necessarily younger than a marine one unless they are superposed. Many profiles are replaced according to the «progradation of the pliocene gulf of Roussillon. The boundary between marine and continental deposits cuts through the chronological line of the Taxodiaceae extinction. The flora investigated (93 taxa) is the first known for the Pliocene of this area. The extinction of the Taxodiaceae in southern France has a climatic cause: the setting in of a mediterranean rhythm (dry summers). This extinction is much older than the one which took place in Italy (Tiberian boundary) and in the Netherlands (Reuverian-Pretiglian boundary).     

Impairment of contractility associated with muscarinic supersensitivity in trachea isolated from diabetic rats: lack of correlation with ultrastructural changes or quinuclidinyl benzylate binding to lung membranes

Evolution of cholinergic response of rat isolated trachea was determined after various durations of diabetes (17, 40, 90, 150 and 210 days). Long-term diabetes was associated with both impairment of contractility and supersensitivity to cholinergic stimulation. However, the mechanism of these alterations remains to be determined, as response to field stimulation was not specifically altered while electron microscopy studies could not detect any significant change in the aspect of nerves, smooth muscle or epithelium. As well, binding studies of lung cholinergic receptors using the antagonist ligand [³H]-quinuclidinyl benzylate and the agonist carbachol did not detect any change in diabetic animals.     

Short and simple synthesis of (R)- and (S)-4-hydroxypentylaminoacetamide: both enantiomers of the (ω-1)-hydroxylated metabolite of milacemide

Both (R)- and (S)-4-hydroxypentylaminoacetamide have been synthesized by reductive amination of glycinamide on the γ-valerolactols corresponding to (R)- and (S)-γ-valerolactone, respectively. These enantiomeric lactones were readily obtained in high enantiomeric excess (ee) by enzymic porcine pancreatic lipase (PPL) kinetic resolution of rac-methyl γ-hydroxyvalerate. © 1992 Wiley-Liss, Inc.     

Purification of plant mitochondria by isopycnic centrifugation in density gradients of Percoll

Mitochondria from potato tubers have been separated from contaminating organelles and membrane vesicles on self-generated Percoll gradients and in a relatively short time. The Percoll-purified mitochondria devoid of carotenoids and galactolipids showed no contamination with intact plastids, microbodies, or vacuolar enzymes. Percoll-purified mitochondria exhibited intact membranes and a dense matrix. The intactness of purified mitochondrial preparations was ascertained by the measurement of KCN-sensitive ascorbate cyt c-dependent O₂ uptake. When compared with washed mitochondria, Percoll-purified mitochondria showed improved rates of substrate oxidation, respiratory control, and ADP:O ratios. The recovery of the cyt oxidase was 70–90% and on a cyt oxidase basis the rate of succinate oxidation by unpurified mitochondria was equal to that recorded for Percoll-purified mitochondria. The great flexibility of purification procedure involving silica sols was extended from mitochondria to the isolation of intact peroxisomes.     

The lipopolysaccharide-transporter complex LptB2FG also displays adenylate kinase activity in vitro dependent on the binding partners LptC/LptA

Lipopolysaccharide (LPS) is an essential glycolipid that covers the surface of gram-negative bacteria. The transport of LPS involves a dedicated seven-protein transporter system called the lipopolysaccharide transport system (Lpt) machinery that physically spans the entire cell envelope. The LptB₂FG complex is an ABC transporter that hydrolyzes ATP to extract LPS from the inner membrane for transport to the outer membrane. Here, we extracted LptB₂FG directly from the inner membrane with its original lipid environment using styrene-maleic acid polymers. We found that styrene-maleic acid polymers–LptB₂FG in nanodiscs display not only ATPase activity but also a previously uncharacterized adenylate kinase (AK) activity, as it catalyzed phosphotransfer between two ADP molecules to generate ATP and AMP. The ATPase and AK activities of LptB₂FG were both stimulated by the interaction on the periplasmic side with the periplasmic LPS transport proteins LptC and LptA and inhibited by the presence of the LptC transmembrane helix. We determined that the isolated ATPase module (LptB) had weak AK activity in the absence of transmembrane proteins LptF and LptG, and one mutation in LptB that weakens its affinity for ADP led to AK activity similar to that of fully assembled complex. Thus, we conclude that LptB₂FG is capable of producing ATP from ADP, depending on the assembly of the Lpt bridge, and that this AK activity might be important to ensure efficient LPS transport in the fully assembled Lpt system.     

Simian Immunodeficiency Virus (SIV) from Sun-Tailed Monkeys (Cercopithecus solatus): Evidence for Host-Dependent Evolution of SIV within the C. lhoesti Superspecies

Recently we reported the characterization of simian immunodeficiency virus (SIVlhoest) from a central African l'hoest monkey (Cercopithecus lhoesti lhoesti) that revealed a distant relationship to SIV isolated from a mandrill (SIVmnd). The present report describes a novel SIV (SIVsun) isolated from a healthy, wild-caught sun-tailed monkey (Cercopithecus lhoesti solatus), another member of the l'hoest superspecies. SIVsun replicated in a variety of human T-cell lines and in peripheral blood mononuclear cells of macaques (Macaca spp.) and patas monkeys (Erythrocebus patas). A full-length infectious clone of SIVsun was derived, and genetic analysis revealed that SIVsun was most closely related to SIVlhoest, with an amino acid identity of 71% in Gag, 73% in Pol, and 67% in Env. This degree of similarity is reminiscent of that observed between SIVagm isolates from vervet, grivet, and tantalus species of African green monkeys. The close relationship between SIVsun and SIVlhoest, despite their geographically distinct habitats, is consistent with evolution from a common ancestor, providing further evidence for the ancient nature of the primate lentivirus family. In addition, this observation leads us to suggest that the SIVmnd lineage should be designated the SIVlhoest lineage.