Antibody binding capacity of different peptide chains isolated from digested and purified horse diphtheria antitoxin

In commercial digested and purified horse diphtheria antitoxin, which is formed largely of the gamma globulin fragment with the sedimentation coefficient 5.3 S, the reactive disulphide bonds were destroyed by S-sulphonation. Gel filtration on Sephadex G-100 in 0.05 M formic acid with 6 M urea showed that the molecule of the S-sulphonated preparation dissociated into chains similar in character to the peptide chains of native horse antitoxins. Antibody activity was still partly maintained even after treatment with 6 M urea. On mixing the two types of chains isolated by gel filtration, antibody activity was recovered, the amount of antibody protein determined in the mixed fractions being greater than the sum of the amounts in the separate fractions. The neutralizing activity of the mixed fractions tested against toxinin vivo was also greater than the sum of the activity of the separate fractions.     

First chemical synthesis of a scorpion alpha-toxin affecting sodium channels: the Aah I toxin of Androctonus australis hector.

Aah I is a 63-residue alpha-toxin isolated from the venom of the Buthidae scorpion Androctonus australis hector, which is considered to be the most dangerous species. We report here the first chemical synthesis of Aah I by the solid-phase method, using a Fmoc strategy. The synthetic toxin I (sAah I) was renatured in DMSO-Tris buffer, purified and subjected to thorough analysis and comparison with the natural toxin. The sAah I showed physico-chemical (CD spectrum, molecular mass, HPLC elution), biochemical (amino-acid composition, sequence), immunochemical and pharmacological properties similar to those of the natural toxin. The synthetic toxin was recognized by a conformation-dependent monoclonal anti-Aah I antibody, with an IC50 value close to that for the natural toxin. Following intracerebroventricular injection, the synthetic and the natural toxins were similarly lethal to mice. In voltage-clamp experiments, Na(v) 1.2 sodium channel inactivation was inhibited by the application of sAah I or of the natural toxin in a similar way. This work describes a simple protocol for the chemical synthesis of a scorpion alpha-toxin, making it possible to produce structural analogues in time.     

What generates the diversity of Wolbachia—arthropod interactions?

Wolbachia are strictly endocellular, vertically transmitted bacteria associated with insects and crustaceans. This group of parasites modify their hosts' reproduction so as to increase their own fitness. This paper reviews the variability of these parasitic alterations and their consequences for host biology and populations. Wolbachia induce cytoplasmic incompatibility (a characteristic apparently specific to Wolbachia) in several insects and one isopod crustacean; parthenogenesis (thelytoky) in haplo-diploid insects; feminization in various isopods. The consequences of these phenomena on speciation, population dynamics and genetic polymorphism are discussed. The variability of the mechanisms of host sex determination is one important factor responsible for the diversity of Wolbachia-host interactions. However, parasite characteristics, such as the capacity to disturb host mitosis, and the ability to be horizontally transferred between hosts, also appear to play a role in this diversity.     

Effect of taurine on wound healing

Summary Taurine which has antioxidant effects is also known to have effects on cell proliferation, inflammation and collagenogenesis. The aim of this study was to investigate the effect of taurine on incisional skin wounds.The mice incised on the dorsal area were divided into control and experimental groups. Saline was injected intraperitoneally to half of the animals in the control group and locally applied to the other half. Fifty mM taurine solution was given intraperitoneally to the first half of the experimental animals and locally to the second half of the experimental group.After four days of treatment, malondialdehyde (MDA) and histamine levels as well as the tensile strength of the wound tissue were measured. Structural alterations in epidermis and dermis were histologically evaluated.The locally administreated taurine significantly increased wound tensile strength by decreasing the MDA and histamine levels and prevented the degranulation of the mast cells. These observations suggest that taurine may be useful on wound healing.     

Effect of anoxia and reoxygenation on antioxidant enzyme activities in immortalized brain endothelial cells

Summary The effects of anoxia and reoxygenation on major antioxidant enzyme activities were investigatedin vitro in immortalized rat brain endothelial cells (RBE₄ cells). A sublethal anoxic period of 12 h was assessed for RBE₄ cells using the neutral red uptake test. Anoxia markedly influenced the specific activity of catalase and superoxide dismutase, with no major effect on glutathione peroxidase or glutathione reductase. After 24 h postanoxia, the superoxide dismutase activity modulated by the presence or absence of oxygen returned to control value. Damage and recovery of RBE₄ immortalized rat brain endothelial cells in culture after exposure to free radicals and other oxygen-derived species provides a usefulin vitro model to study anoxia-reoxygenation trauma at the cellular level.     

Effects of peptide YY and its analogues on chloride ion secretion in fed and fasted rat jejunum

The aim of our study was to determine whether a meal modifies the antisecretory response induced by PYY and the structural requirements to elicit antisecretory effects of analogue PYY(22–36) for potential antidiarrhea therapy. The variations in short-circuit current (Isc) due to the modification of ionic transport across the rat intestine were assessed in vitro, using Ussing chambers. In fasted rats, PYY induced a dose- and time-dependent reduction in Isc, with a sensitivity threshold at 5 × 10⁻¹¹ M (ΔIsc −2 ± 0.5 μA/cm²). The reduction was maximal at 10⁻⁷ M (Isc −23 ± 2 μA/cm²), and the concentration producing half-maximal inhibition was 10⁻⁹ M. At 10⁻⁷ M, reduction of Isc by PYY reached 90% of response to 5 × 10⁻⁵ M bumetanide. The PYY effect was partly reversed by 10⁻⁵ M forskolin (Isc +13.43 ± 2.91 μA/h·cm², p < 0.05) or 10⁻³ M dibutyryl adenosine 3′,5′ cyclic monophosphate (Isc +12 ± 1.69 μA/cm², p < 0.05). Naloxone and tetrodotoxin did not alter the effect of PYY. In addition, PYY and its analogue P915 reduced net chloride ion secretion to 2.85 and 2.29 μEq/cm² (p < 0.05), respectively. The antisecretory effect of PYY was accompanied by dose- and time-dependent desensitization when jejunum was prestimulated by a lower dose of peptide. The antisecretory potencies exhibited by PYY analogues required both a C-terminal fragment (22–36) and an aromatic amino acid residue (Trp or Phe) at position 27. At 10⁻⁷ M the biological activity of PYY was lower in fed than fasted rats (p < 0.001). Our results confirm the antisecretory effect of PYY, but show that the fed period is accompanied by desensitization, similar to the transient desensitization observed in the fasted period with cumulative doses. This suggests that PYY may act as a physiological mediator that reduces intestinal secretion.     

Maintenance of two genetic entities by habitat selection

Summary In the laboratory, the two species of copepodsLepeophtheirus thompsoni andLepeophtheirus europaensis, ectoparasites of flatfishes, can meet and mate on at least one host species. In the wild however, these two species are found isolated on their sympatric hosts. Habitat selection theoretically represents a powerful enough mechanism to explain the maintenance of genetic heterogeneity in the wide sense. In this paper, the host colonization process is studied for both parasite species. It is shown that each parasite can develop and reach adult age on each host species. However,L. thompsoni is highly selective; it almost totally refuses to colonize hosts other than its natural one.Lepeophtheirus europaensis, on the contrary, readily infests turbot and brill in single-host experiments, but strongly prefers the brill when it has a choice. It appears that these two genetic entities are sympatrically maintained due to strong habitat selection. Such a pattern could theoretically only occur in a soft-selection context (density dependence). This point is discussed with respect to the different patterns in host use found in the geographical distribution of these parasites.     

Repetitive DNA sequences located in the central region of the human mdr1 (multidrug resistance) gene may account for a gene fusion event during its evolution

The mdr1 gene, first member of the human multidrug-resistance gene family, is a major gene involved in cellular resistance to several drugs used in anticancer chemotherapy. Its product, the drug-excreting P-glycoprotein, shows a bipartite structure formed by two similar adjacent halves. According to one hypothesis, the fusion of two related ancestral genes during evolution could have resulted in this structure. The DNA sequence analysis of the introns located in the region connecting the two halves of the human mdr1 gene revealed a highly conserved poly(CA) · poly (TG) sequence in intron 15 and repeated sequences of the Alu family in introns 14 and 17. These repeated sequences most likely represent molecular fossils of ancient DNA elements which were involved in such a recombination event. Correspondence to: M. Pauly     

Operational patterns affecting lactic acid production in ultrafiltration cell recycle bioreactor

Lactic acid production with cell recycling on an ultrafiltration tubular membrane reactor was studied; higher lactic acid concentrations as well as productivities were obtained under long-term fermentations compared with other high cell density systems. Different operational conditions, namely dilution rates and start-up modes, were assessed. Performances were very different at the three different dilution rates tested (D = 0.20 h(-1), D = 0.40 h(-1), or D = 0.58 h(-1)). The different behaviours are discussed and factors responsible for them are presented. The best way to operate for lactic acid production is chosen, the dilution rate of D = 0.40 h(-1) being the one providing the best overall performance. On the other hand, results show that of the two start-up modes tested, continuous start (membrane open) permits higher permeabilities throughout the operational runs than batch start (membrane closed). Operational stability was found to be directly associated with membranes that work at "steady state," the membrane permeability being kept around 15 L/m(2) h. Optimized cell bleed can improve time of operation if such membrane permeability can be maintained for a longer time. A comparison of results with those obtained in other lactic acid production systems is presented; such comparison shows that this tubular ultrafiltration membrane cell recycle reactor presents three important advantages: (1) concomitant lactic acid concentrations and productivities; (2) long periods of operation at reasonable permeabilities; and (3) good mechanical stability permitting the use of steam sterilization. (c) 1995 John Wiley & Sons, Inc.