The evolution of Nyctereutes (Carnivora: Canidae) in the Nihewan Basin,Hebei, northern China

The occurrence of Nyctereutes during the Plio-Pleistocene has long been reported in northern China, with the highest abundance in the Nihewan Basin. However, due to site dispersal, the coexistence of different taxa, and lack of a precise stratigraphic constraint, the evolutionary process of this genus remains enigmatic. In this study, we re-examined the available Nyctereutes materials recovered from the Nihewan Basin housed in IVPP and Tianjin Natural History Museum, in addition to a newly recovered specimen from our latest excavation. Furthermore, we compared these materials with Nyctereutes fossils recovered from the Pleistocene Zhoukoudian sites near Beijing and the extant species N. procyonoides. Our analysis of the upper molar morphometry reveals the variations in size and dietary characteristics within different species of Nyctereutes during the late Plio-Pleistocene. The examination of molars indicates an increase in the size of Nyctereutes sinensis compared to early Pliocene N. tingi as well as changes in the molar teeth morphology. Subsequently, changes in diet or environmental factors possibly caused the decrease of body size in the late Pleistocene. We also estimate an age constraint for the fossils of N. sinensis from the Xiashagou section by relocating Licent's localities and referring of updated magnetostratigraphic data.     

Regeneration of bovine and octopus opsins in situ with natural and artificial retinals

We consider the problem of color regulation in visual pigments for both bovine rhodopsin (lambda max = 500 nm) and octopus rhodopsin (lambda max = 475 nm). Both pigments have 11-cis-retinal (lambda max = 379 nm, in ethanol) as their chromophore. These rhodopsins were bleached in their native membranes, and the opsins were regenerated with natural and artificial chromophores. Both bovine and octopus opsins were regenerated with the 9-cis- and 11-cis-retinal isomers, but the octopus opsin was additionally regenerated with the 13-cis and all-trans isomers. Titration of the octopus opsin with 11-cis-retinal gave an extinction coefficient for octopus rhodopsin of 27,000 +/- 3000 M-1 cm-1 at 475 nm. The absorption maxima of bovine artificial pigments formed by regenerating opsin with the 11-cis dihydro series of chromophores support a color regulation model for bovine rhodopsin in which the chromophore-binding site of the protein has two negative charges: one directly hydrogen bonded to the Schiff base nitrogen and another near carbon-13. Formation of octopus artificial pigments with both all-trans and 11-cis dihydro chromophores leads to a similar model for octopus rhodopsin and metarhodopsin: there are two negative charges in the chromophore-binding site, one directly hydrogen bonded to the Schiff base nitrogen and a second near carbon-13. The interaction of this second charge with the chromophore in octopus rhodopsin is weaker than in bovine, while in metarhodopsin it is as strong as in bovine.     

Multiple sites of DCIP reduction by sonicated Oat chloroplasts: Role of plastocyanin

1. Oat chloroplasts, in the presence of 0.02 M methylamine, reduce 2,6 dichlorophenolindophenol (DCIP) at a rate of 350–500 μmoles/mg chl per h, in saturating light. Brief sonication for approx. 1 min lowers the rate to approx. 50 μmoles/mg chl per h; longer sonication does not reduce activity further. During brief sonication, plastocyanin is lost from the chloroplasts. When plastocyanin is added back to sonicated fragments, DCIP reduction is approximately doubled to 100 μmoles/mg chl per h.

2. When oxidized plastocyanin is added, a transient is observed when light is first turned on: this is due to a reduction of the plastocyanin before DCIP reduction begins. When reduced plastocyanin is added, a different transient occurs: this is due to a fast photoreduction of DCIP by the plastocyanin and is followed by the slower steady state reduction of DCIP by water. When light is turned off before complete reduction of DCIP, a transient reduction of oxidized plastocyanin by reduced DCIP is seen. Insensitivity of these transients to 3(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU) and the greater effectiveness of 710 nm light, along with the known capacity of plastocyanin to mediate electron transfer to System I, prove that an intrinsically fast reduction of DCIP occurs at a site close to the primary photoreduced product of System I.

3. After brief sonication and washing, no residual plastocyanin was detected in chloroplast fragments, and the rate of the slow DCIP reduction (about 50μmoles/mg chl per h) sustained by such fragments was essentially identical to that maintained by fragments of mutants lacking System I activity. Following et al.⁹, the simplest explanation for this slow DCIP reduction is that is occurs at a site close to System II and the system I is not involved.

4. A very slow transient reduction of DCIP occurs after extinguishing light; this presumably involves another reduction site close to System II, as suggested by ⁹.     

The mechanism of cobalamin binding to hog intrinsic factor

Chicken brain Arylsulfatase A (E.C.3.1.6.1) was immobilized by interaction with Concanavalin A. The immobilized enzyme retained its catalytic activity and this enzyme can be reused without appreciable loss of activity. The storage stability of bound and soluble enzymes was comparable and binding of enzyme to Concanavalin A increases its thermal stability. Kinetic studies indicated that bound enzyme shows similar anomalous kinetics as that of free enzyme but slight change was observed in relation to pH optima, Km value and activation energy.     

The binding motifs for Ac transposase are absolutely required for excision of Ds1 in maize

A reverse genetic system for studying excision of the transposable elementDs1 in maize plants has been established previously. In this system, theDs1 element, as part of the genome of maize streak virus (MSV), is introduced into maize plants via agroinfection. In the presence of theAc element, excision ofDs1 from the MSV genome results in the appearance of viral symptoms on the maize plants. Here, we used this system to study DNA sequences requiredin cis for excision ofDs1. TheDs1 element contains theAc transposase binding motif AAACGG in only one of its subterminal regions (defined here as the 5′ subterminal region). We showed that mutation of these motifs abolished completely the excision capacity ofDs1. This is the first direct demonstration that the transposase binding motifs are essential for excision. Mutagenesis with oligonucleotide insertions in the other (3′) subterminal region resulted in elements with either a reduced or an increased excision efficiency, indicating that this subterminal region also has an important function.     

Synthesis and antiplatelet, antiinflammatory, and antiallergic activities of 2-substituted 3-chloro-1,4-naphthoquinone derivatives

A series of 2-substituted 3-chloro-1,4-naphthoquinones was synthesized, and the antiplatelet, antiinflammatory, and antiallergic activities of these compounds were evaluated. The structure-activity relationships in this series were also examined. Most of the 2-alkyl/arylcarboxamido derivatives of 3-chloro-1,4-naphthoquinone showed potent activities with similar trends in each of the activities evaluated.