A Candidate Subspecies Discrimination System Involving a Vomeronasal Receptor Gene with Different Alleles Fixed in M. m. domesticus and M. m. musculus

Assortative mating, a potentially efficient prezygotic reproductive barrier, may prevent loss of genetic potential by avoiding the production of unfit hybrids (i.e., because of hybrid infertility or hybrid breakdown) that occur at regions of secondary contact between incipient species. In the case of the mouse hybrid zone, where two subspecies of Mus musculus (M. m. domesticus and M. m. musculus) meet and exchange genes to a limited extent, assortative mating requires a means of subspecies recognition. We based the work reported here on the hypothesis that, if there is a pheromone sufficiently diverged between M. m. domesticus and M. m. musculus to mediate subspecies recognition, then that process must also require a specific receptor(s), also sufficiently diverged between the subspecies, to receive the signal and elicit an assortative mating response. We studied the mouse V1R genes, which encode a large family of receptors in the vomeronasal organ (VNO), by screening Perlegen SNP data and identified one, Vmn1r67, with 24 fixed SNP differences most of which (15/24) are nonsynonymous nucleotide substitutions between M. m. domesticus and M. m. musculus. We observed substantial linkage disequilibrium (LD) between Vmn1r67 and Abpa27, a mouse salivary androgen-binding protein gene that encodes a proteinaceous pheromone (ABP) capable of mediating assortative mating, perhaps in conjunction with its bound small lipophilic ligand. The LD we observed is likely a case of association rather than residual physical linkage from a very recent selective sweep, because an intervening gene, Vmn1r71, shows significant intra(sub)specific polymorphism but no inter(sub)specific divergence in its nucleotide sequence. We discuss alternative explanations of these observations, for example that Abpa27 and Vmn1r67 are coevolving as signal and receptor to reinforce subspecies hybridization barriers or that the unusually divergent Vmn1r67 allele was not a product of fast positive selection, but was derived from an introgressed allele, possibly from Mus spretus.     

Enzymatic synthesis of two ginsenoside Re-beta-xylosides.

Two new beta-xylosyl derivatives of ginsenoside Re, 20(S)-protopanaxatriol 6-O-alpha-L-rhamnopyranosyl-(1 --> 2)-[beta-D-xylopyranosyl-(1 --> 4)]-beta-D-glucopyranosyl-20-O-beta-D-glucopyranoside and 20(S)-protopanaxatriol 6-O-alpha-L-rhamnopyranosyl-(1 --> 2)-[beta-D-xylopyranosyl-(1 --> 6)]-beta-D-glucopyranosyl-20-O-beta-D-glucopyranoside, were respectively synthesized from p-nitrophenyl beta-D-xylopyranoside and phenyl beta-D-xylopyranoside as donors and ginsenoside Re as the acceptor in 25% acetone and acetonitrile by a cellulase preparation from Trichoderma viride and a beta-galactosidase preparation from Aspergillus oryzae. The latter enzyme preparation also catalyzed the hydrolysis of ginsenoside Re to the minor saponin, ginsenoside Rg2.     

5-Hydroxytryptamine-Stimulated Inositol Phospholipid Hydrolysis in the Mouse Cortex Has Pharmacological Characteristics Compatible with Mediation via 5-HT2 Receptors but This Response Does Not Reflect Altered 5-HT2 Function After 5,7-Dihydroxytryptamine Lesioning or Repeated Antidepressant Treatments

5-Hydroxytryptamine (5-HT; 3 x 10(-8)-1 x 10(-5)M) produced a dose-dependent increase in phosphatidylinositol/polyphosphoinositide (PI) turnover in mouse cortical slices, as measured by following production of 3H-labelled inositol phosphates (IPs) in the presence of 10 mM LiCl. Analysis of individual IPs, in slices stimulated for 45 min, indicated substantial increases in inositol monophosphate (IP1; 140%) and inositol bisphosphate (IP2; 95%) contents with smaller increases in inositol trisphosphate (IP3; 51%) and inositol tetrakisphosphate (IP4; 48%) contents. The increase in IP3 level was solely in the 1,3,4-isomer. This response was inhibited by the nonselective 5-HT antagonists methysergide, metergoline, and spiperone. It was also inhibited by the selective 5-HT2 antagonists ketanserin and ritanserin but not by the 5-HT1 antagonists isapirone, (-)-propranolol, or pindolol. 5-HT-stimulated IP formation was also unaltered by atropine, prazosin, and mepyramine. Lesioning brain 5-HT neurones using 5,7-dihydroxytryptamine (5,7-DHT; 50 micrograms i.c.v.) produced a 210% (p less than 0.01) increase in the number of 5-HT2-mediated head-twitches induced by 5-methoxy-N,N-dimethyltryptamine (2 mg/kg). However, 5,7-DHT lesioning had no effect on 5-HT-stimulated PI turnover in these mice. Similarly, an electroconvulsive shock (90 V, 1 s) given five times over a 10-day period caused an 85% (p less than 0.01) increase in head-twitch responses but no change in 5-HT-stimulated PI turnover. Decreasing 5-HT2 function by twice-a-day injection of 5 mg/kg of zimeldine or desipramine (DMI) produced 50% (p less than 0.01) and 56% (p less than 0.01), respectively, reductions in head-twitch behaviour.(ABSTRACT TRUNCATED AT 250 WORDS)     

Developmental changes in the distribution of cecal lectin-binding sites of Balb-c mice.

The existence of lectin-binding sites was investigated in the cecum of Balb-c mice at seven developmental stages ranging from 18 days post conception (p.c.) to 8 weeks after birth. Nine horseradish-peroxidase-conjugated lectins (concanavalin A, Triticum vulgaris, Dolichus biflorus, Helix pomatia, Arachis hypogaea, Glycine maximus, Lotus tetragonolobus, Ulex europaeus, Limulus polyphemus) were applied to 5- to 7-microns thin paraffin sections of Bouin-fixed tissue. After DAB staining the sections were evaluated by light microscopy. It was shown that each lectin exhibits a unique developmental pattern. The adult binding patterns were established at the age of 3-4 weeks with only minor changes occurring thereafter. Considerable differences in binding patterns occurred not only between lectins of different groups but also between lectins with the same nominal monosaccharide specificity.     

Novel stabilization of phenylalanine ammonia-lyase catalyst during bioconversion of trans-cinnamic acid to l-phenylalanine

Summary Production of l-phenylalanine from trans-cinnamic acid using isolate SPA10 cells was reduced to 26% of that observed initially when cells were reacted a second time with fresh substrate mixture. The stability (reuseability) of Phenylalanine Ammonia-Lyase (PAL) containing cells was significantly influenced by both the trans-cinnamate concentration and initial reaction pH. Using 2% t-cinnamate, l-phenylalanine production was 7-fold greater after 3 successive runs at pH 9.0 than at the optimum of pH 10.2. Cells reacted in the presence of 5% t-cinnamate were relatively unstable. Permeabilising agents, such as toluene and xylene, stimulated l-phenylalanine production but also enhanced instability of the catalyst. Several effectors were shown to stimulate the initial rate of the PAL bioconversion, but only sorbitol, alginate, glutaraldehyde, polyethylene glycol and glycerol conferred any significant degree of stability. Sparging of cultures and bioreactors with various gases revealed that oxygen enhanced PAL inactivation, CO₂ had little effect and nitrogen conferred remarkable stability on PAL activity for several weeks in culture medium. The presence of chloride ions (from HCl) and aeration of substrate mixtures resulted in poor reuseability of catalyst. A combination of H₂SO₄ substitution for HCl and N₂-sparging resulted in excellent initial conversions and good catalyst stability at 26°C but less at 30°C. The inclusion of 1.5 M sorbitol in reaction mixtures maintained PAL stability over several successive incubations.