Syphacia obvelata in the Mongolian gerbil (Meriones unguiculatus): natural occurrence and experimental transmission

An adult from a research colony and a litter of 5-week-old Mongolian gerbils (Meriones unguiculatus) from a pet store were found to have pinworms identified as Syphacia obvelata. The infected gerbils were allowed to cohabitate with uninfected gerbils. Similarly, infected gerbils were caged with uninfected mice and infected mice with uninfected gerbils. Results of these studies showed that Syphacia obvelata can be transmitted from gerbil to gerbil, gerbil to mouse, and mouse to gerbil.     

Gelation of xanthan with trivalent metal ions

In-situ gelation of semidilute xanthan solutions with trivalent chromium, aluminum or iron ions was studied by rheology and UV-spectroscopy. Measurements of the elastic modulus of xanthan gel cylinders prepared by dialysis against the complexing ion at pH values from 2 to 6 indicate that monomeric species of the ion are ineffective, whereas dimeric or higher oligomeric species are effective in crosslinking the polysaccharide. When chromium was used as the crosslinking species, the dependence of the gelation rate on the ionic concentration followed a power law with a coefficient of 1·7. The gelation time and the gelation rate were found to extrapolate to zero at 1 m Cr for 2·5 mg/ml xanthan. The limiting concentration of xanthan needed for gelation with 5 m Cr(III) at 20°C was estimated as 0·35 mg/ml. This critical xanthan concentration is close to the overlap concentration c^* estimated from the experimentally determined intrinsic viscosity [η] using c^* = 1·4/[η]. An apparent activation energy for crosslinking of xanthan was calculated as E_a = 42 kJ/mol and E_a = 108 kJ/mol for Cr and Al ions, respectively. The fractal dimensionality of xanthan-Cr at the sol-gel transition was estimated as 1·3 applying the Chambon-Winter criterion for gelation, thus indicating that this gelation criterion is applicable also to stiff-chain polysaccharides such as xanthan.     

Marine biosurfactants. IV. Production,characterization and biosynthesis of an anionic glucose lipid from the marine bacterial strain MM1

Summary During screening for biosurfactants among marine, n-alkane-utilizing bacteria, low- and high-molecular surface-active substances were detected. The marine bacterial strain MM1 was found to synthesize a novel glycolipid that has not so far been cited in the literature. Both ¹H, ¹³C-nuclear magnetic resonance spectroscopic and positive ion fast atom bombardment mass spectrometer studies led to the identification of a glucose lipid consisting of four 3-OH-decanoic acids, which are linked together by ester bonds. The lipophilic moiety is coupled glycosidically with C-1 of glucose. The glucolipid reduced the surface tension from 72 mN/m to 30 mN/m while the minimum interfacial tension towards n-hexadecane was lowered to values smaller than 5 mN/m. Correspondence to: S. Lang     

Expression of v-src induces aberrant development and twinning in chimaeric mice

The role of the proto-oncogene c-src in mouse development has been investigated by studying the consequences of expressing its viral homologue, v-src. Embryonic stem (ES) cell lines with differing levels of v-src tyrosine kinase activity have been used to generate chimaeric mice. Whereas a low level of v-src expression is compatible with embryogenesis, chimaeras derived from ES clones with high levels of v-src activity develop abnormally and die on the 8th-9th day of gestation. These abnormalities are characterized by the formation of twin or multiple embryos within the same Reichert's membrane, and by the arrest of embryonic development at the late egg cylinder stage, accompanied by relative expansion of the visceral yolk sac (VYS) and hyperplasia of the VYS endoderm. These results demonstrate for the first time that deregulated expression of the src protooncogene product can induce developmental abnormalities during early embryogenesis.     

Pipecolic acid biosynthesis in Rhizoctonia leguminicola. II. Saccharopine oxidase: a unique flavin enzyme involved in pipecolic acid biosynthesis

The fungal parasite Rhizoctonia leguminicola produces two indolizidine alkaloids, slaframine and swainsonine, of physiological interest. These alkaloids are biosynthesized from pipecolic acid which in turn is derived from L-lysine in this fungus as shown in the accompanying paper (Wickwire, B.M., Harris, C.M., Harris, T.M., and Broquist, H.P. (1989) J. Biol. Chem. 265, 14742-14747): L-lysine----saccharopine----delta 1----piperideine-6- carboxylate----pipecolate. This paper concerns the discovery, purification, and properties of a flavoenzyme, termed saccharopine oxidase, which carries out the oxidative cleavage of saccharopine as follows: Saccharopine + O2----delta 1-piperidine-6-carboxylate + glutamate + H2O2 The enzyme was purified 2,000-fold to homogeneity (polyacrylamide gel electrophoresis) in 14% yield from R. leguminicola mycelia, and had a native molecular mass of about 45,000 daltons by gel filtration (fast protein liquid chromatography Superose). Evidence for the presence of a flavin in the enzyme was drawn from these considerations: (a) the enzyme, while oxidatively cleaving saccharopine, concomitantly reduces 2,6-dichlorophenolindophenol; (b) the purified enzyme has a fluorescence spectrum typical of flavins; and (c) the enzyme requires oxygen and produces hydrogen peroxide. Good correlation was shown with purified saccharopine oxidase between disappearance of saccharopine with the concomitant appearance of delta 1-piperideine-6-carboxylate plus glutamate. The enzyme has a pH optimum about 6 and a Km for saccharopine of 0.128 mM. The enzyme apparently exists in R. leguminicola to shunt saccharopine, a major lysine metabolite, into a secondary pathway of lysine metabolism leading to pipecolate and subsequently to slaframine and swainsonine.     

Avian alcohol dehydrogenase. Characterization of the quail enzyme, functional interpretations, and relationships to the different classes of mammalian alcohol dehydrogenase

The primary structure of the major quail liver alcohol dehydrogenase was determined. It is a long-chain, zinc-containing alcohol dehydrogenase of the type occurring also in mammals and hence allows judgement of the gene duplications giving rise to the classes of the human alcohol dehydrogenase system. The avian form is most closely related to the class I mammalian enzyme (72-75% residue identity), least related to class II (60% identity), and intermediately related to class III (64-65% identity). This pattern distinguishes the mammalian enzyme classes and separates classes I and II in particular. In addition to the generally larger similarities with class I, the avian enzyme exhibits certain residue patterns otherwise typical of the other classes, including an extra Trp residue, present in both class II and III but not in class I, with a corresponding increase in the UV absorbance. The avian enzyme further shows that a Gly residue at position 260 previously considered strictly conserved in alcohol dehydrogenases can be exchanged with Lys. However, zinc-binding residues, coenzyme-binding residues, and to a large extent substrate-binding residues are unchanged in the avian enzyme, suggesting its functional properties to be related to those of the class I mammalian alcohol dehydrogenases. In contrast, the areas of subunit interactions in the dimers differ substantially. These results show that (a) the vertebrate enzyme classes are of distant origin, (b) the submammalian enzyme exhibits partly mixed properties in relation to the classes, and (c) the three mammalian enzyme classes are not as equidistantly related as initially apparent but suggest origins from two sublevels.     

Interactions leading to colour opponency in ganglion cells of the turtle retina

In the turtle retina, colour-dependent photoresponses could be recorded intracellularly from ganglion cells receiving only bipolar cell input. Thus, the mechanism for colour discrimination by these ganglion cells (type A) is contained in the outer plexiform layer of the retina and depends on interaction between horizontal and cone cells. Ganglion cells receiving an additional amacrine input (type B) are not influenced by colour, and have about 0.7 logarithmic unit lower absolute sensitivity to peak wavelength than have type A ganglion cells.     

Antagonistic effect of cocultivation on mitomycin C-induced aberration rate in cells of a patient with Fanconi's anemia and in Chinese hamster ovary cells

Summary The rate of spontaneous chromosomal aberrations in fibroblasts of a patient with Fanconi's anemia was slightly reduced after cocultivation with Chinese hamster ovary (CHO) cells. However, after mitomycin C treatment, a significant reduction of induced chromosomal damage was found in the FA cells while a significant increase was observed in the CHO cells. This antagonistic effect could be attributed to some diffusible agent(s). The results are discussed with respect to the underlying mechanism of the disease.