Water relations of polyol accumulation by Zygosaccharomyces rouxii in continuous culture

Summary Glycerol and arabitol were the main polyols accumulated by Zygosaccharomyces rouxii in continuous culture but the intracellular and extracellular concentrations of the polyols varied with the dilution rate and osmoticum used to adjust the water activity (a_w) to 0.960. When the a_w was adjusted with NaCl, glycerol was the main polyol accumulated intracellularly whereas glycerol and arabitol were accumulated when polyethylene glycol (PEG) 400 was used. The extracellular glycerol and arabitol concentrations at 0.960 a_w (NaCl or PEG 400) were similar or decreased relative to cultures at 0.998 a_w. Compared to steady-state cultivation at 0.998 a_w, the yeast retained at 0.960 a_w (NaCl or PEG 400) a greater proportion of the total glycerol intracellularly against an increased concentration ratio without significantly greater production of glycerol. Arabitol was only significant in osmoregulation when cultivated at 0.960 a_w (PEG 400). The intracellular glycerol concentration was insufficient to balance the a_w across the membrane, but an equilibrium could be achieved under certain conditions if arabitol was also osmotically active. Offprint requests to: P. J. van Zyl     

Preparation and characterization of human interleukin-5 expressed in recombinant Escherichia coli.

The gene coding for human interleukin-5 was synthesized and expressed in Escherichia coli under control of a heat-inducible promoter. High-level expression, 10-15% of total cellular protein, was achieved in E. coli. The protein was produced in an insoluble state. A simple extraction, renaturation and purification scheme is described. The recombinant protein was found to be a homodimer, similar to the natural murine-derived protein. Despite the lack of glycosylation, high specific activities were obtained in three 'in vitro' biological assays. Physical characterization of the protein showed it to be mostly alpha-helical, supporting the hypothesis that a conformational similarity exists among certain cytokines.     

Knockout of the two ldh genes has a major impact on peptidoglycan precursor synthesis in Lactobacillus plantarum.

Most bacteria synthesize muramyl-pentapeptide peptidoglycan precursors ending with a D-alanyl residue (e.g., UDP-N-acetylmuramyl-L-Ala-gamma-D-Glu-L-Lys-D-Ala-D-Ala). However, it was recently demonstrated that other types of precursors, notably D-lactate-ending molecules, could be synthesized by several lactic acid bacteria. This particular feature leads to vancomycin resistance. Vancomycin is a glycopeptide antibiotic that blocks cell wall synthesis by the formation of a complex with the extremity of peptidoglycan precursors. Substitution of the terminal D-alanine by D-lactate reduces the affinity of the antibiotic for its target. Lactobacillus plantarum is a lactic acid bacterium naturally resistant to vancomycin. It converts most of the glycolytic pyruvate to L- and D-lactate by using stereospecific enzymes designated L- and D-lactate dehydrogenases, respectively. In the present study, we show that L. plantarum actually synthesizes D-lactate-ending peptidoglycan precursors. We also report the construction of a strain which is deficient for both D- and L-lactate dehydrogenase activities and which produces only trace amounts of D- and L-lactate. As a consequence, the peptidoglycan synthesis pathway is drastically affected. The wild-type precursor is still present, but a new type of D-alanine-ending precursor is also synthesized in large quantities, which results in a highly enhanced sensitivity to vancomycin.     

Association of enkephalin catabolism inhibitors and CCKB antagonists: A potential use in the management of pain and opioid addiction

The overlapping distribution of opioid and cholecystokinin (CCK) peptides and their receptors (μ and δ opioid receptors; CCK-A and CCK-B receptors) in the central nervous system have led to a large number of studies aimed at clarifying the functional relationships between these two neuropeptides. Most of the pharmacological studies devoted to the role of CCK and enkephalins have been focused on the control of pain. Recently the existence of regulatory mechanisms between both systems have been proposed, and the physiological antagonism between CCK and endogenous opioid systems has been definitely demonstrated by coadministration of CCK-B selective antagonists with RB 101, a systemically active inhibitor, which fully protects enkephalins from their degradation. Several studies have also been done to investigate the functional relationships between both systems in development of opioid side-effects and in behavioral responses. This article will review the experimental pharmacology of association of enkephalin-degrading enzyme inhibitors and CCK-B antagonists to demonstrate the interest of these molecules in the management of both pain and opioid addiction. Special issue dedicated to Dr. Eric J. Simon.     

O-glycosylation of dipeptides using β-galactosidase activity of Achatina achatina digestive juice

Summary Enzymatic O-glycosylation of dipeptide derivatives containing a serine residue in the N or C terminal position and alanine or glycine as the second amino acid was achieved using the transgalactosylation activity of -galactosidase from the Achatina achatina digestive juice. Reactions were performed with lactose as glycosyl donor and the dipeptide ethyl (or methyl) esters N-protected by a benzyloxycarbonyl group (Z) as glycosyl acceptors. Yields of galactosyl-dipeptide derivatives were much higher than those obtained with the E.coli -galactosidase as catalyst.     

Fatal attack on an infant by an adult female tonkean macaque

We describe a fatal attack on a 10-month-old female infant by an adult female Tonkean macaque (Macaca tonkeana)in a semi-free-ranging group. During an intense conflict involving many group members, an adult female, the second most dominant in the group, attacked the infant of a lower-ranking female. The attacker remained near the victim for approximately 20 min, grabbing and biting it repeatedly, until the mother retrieved the infant. She died 2 days later. An autopsy revealed no lethal injury;the main cause of death was starvation or dehydration or both. We discuss social conditions under which a fatal attack by an adult female might occur.     

Halcyon days with Bill Arnold

The circumstances that led to the discovery that plants luminesce after they are illuminated are described, as are other discoveries that would not have been possible were it not for the fortuitous association I had with my dear and most admirable friend, W.A. Arnold, to whom this special issue is dedicated.     

Germline genomic structure of the B10.A mouseTcra-V2 gene subfamily

 The number of mouse Tcra-V gene segments varies from one individual to another and is estimated to be about 100. Southern blot analysis revealed that most of the Tcra-V are organized in clusters composed of copies of Tcra-V belonging to different subfamilies. We analyzed in detail a Tcra-V subfamily and looked for new Tcra-V in order to improve the knowledge of the mouse Tcra locus organization. A series of genomic clones derived from the B10.A mouse strain enclosing these clusters was used to determined the structure of all the Tcra-V2. We were able to identify ten Tcra-V2. This study showed that the Tcra-V2 can be organized into three structural subgroups. The distribution of the genes along the Tcra locus, plus their structural organization, indicates that successive duplications occurred during the processes of expansion and contraction of the Tcra-V gene subfamilies. Several Tcra-V2 are also identical, indicating recent duplications. The most divergent Tcra-V2 differ by 7.4% nucleotides, leading to 5.2% differences in amino acid contents. Received: 8 August 1995 / Revised: 24 April 1996     

Times to exhaustion at 100% of velocity at [(V)\dot]\textO\text2 \dot V{\text{O}}_{\text{2}} max and modelling of the time-limit / velocity relationship in elite long-distance runners

The aim of this study was to measure running times to exhaustion (Tlim) on a treadmill at 100% of the minimum velocity which elicits _{max max} in 38 elite male long - distance runners _max = 71.4 ± 5.5 ml.kg^–1.min^–1 and _max = 21.8 ± 1.2 km.h^–1). The lactate threshold (LT) was defined as a starting point of accelerated lactate accumulation around 4 mM and was expressed in _max. Tlim value was negatively correlated with _max (r = -0.362, p< 0.05) and _max (r = –0.347, p< 0.05) but positively with LT (%v _max) (r = 0.378, p < 0.05). These data demonstrate that running time to exhaustion at _max in a homogeneous group of elite male long-distance runners was inversely related to _max and experimentally illustrates the model of Monod and Scherrer regarding the time limit-velocity relationship adapted from local exercise for running by Hughson et al. (1984) .     

Ultrastructure of Spermiogenesis and the Spermatozoon of Mathevotaenia herpestis(Cestoda), Intestinal Parasite of Atelerix albiventrisin Senegal

Spermiogenesis in M. herpestisbegins with the formation of a differentiation zone which contains two centrioles associated with an electron–dense, finely granular material. This granular material very quickly becomes striated, a median cytoplasmic extension forms, one of the centrioles becomes laterally oriented in a cytoplasmic bud and the other gives rise to a flagellum. After the migration of the nucleus, a helicoidal crested–like body forms, then the old spermatid separates from the residual cytoplasm. The mature M. herpestisspermatozoon exhibits an apical cone of electron–dense material, a crested–like body and cortical microtubules which are electron–dense centred and spiralized except at their posterior extremity where they are parallel to the spermatozoon axis. The axoneme is of the 9 + ‘1’ pattern. It reaches the posterior extremity of the gamete where the cytoplasm is very electron–dense. The presence of centrioles flanked by ‘striated roots’ has never, to our knowledge, been reported in a platyhelminth. Likewise, a nucleus with an annular cross–section and unevenly distributed electron–dense peri–axonemal material has never been described in a cestod.