The status of Mastodon angustidens pygmaeus Depéret, 1897 (Proboscidea,Mammalia): The contribution of X-ray tomography

The status of Mastodon angustidens pygmaeus Depéret, 1897 is discussed on the basis of an examination of the holotype (a broken lower molar) with tomography using X-rays, and on a review of the previous taxonomic hypotheses. The conclusion is that the holotype is a possible supernumerary post-m3 molar that may be that of a tetralophodont gomphothere. “M. angustidens pygmaeus” is then a nomen dubium that should only be used in relation to the holotype.     

A new heterodontosaurid dinosaur (Reptilia: Ornithischia) from the Upper Triassic Red Beds of Lesotho

A new species of ornithischian dinosaur ( Lycorhinus consors sp. nov.) is established on a skull from the Upper Triassic Red Beds of Lesotho. This ornithischian is assigned to the family Heterodontosauridae of the suborder Ornithopoda. The dinosaurs of the family Heterodonto-sauridae are reviewed: Geranosaurus atavus Broom (1911) is considered a nomendubium and the genus name Heterodontosaurus Crompton & Charig (1962) is held to be a junior synonym for Lycorhinus Haughton (1924).
Functional and palaeoecological implications of the heterodontosaurid dentition are discussed. The pattern of tooth wear may reflect a highly specialized jaw action which involved protraction and retraction of the mandible to produce a grinding effect between upper and lower cheek teeth. Lycorhinus consors is presumed to be a female heterodontosaurid because it differs from all other heterodontosaurids in lacking caniniform tusks. It is suggested that the tusks of heterodontosaurids were functionally analogous to those of tayassuids and tragulids and that they were employed as weapons for intra-specific combat and defence. Dental peculiarities indicate that tooth replacement processes were suppressed in heterodontosaurids; replacement of the teeth seems to have been restricted to a brief period each year (presumably when heterodontosaurids underwent aestivation or hibernation).
A new diagnosis is formulated for the family Heterodontosauridae. The relationships of early ornithopod dinosaurs are briefly reviewed and a new classification is proposed. Ten families of ornithopod dinosaurs are recognized; these are ranked in two grades-one (named Dolichopoda) representing the conservative main stem of the ornithischian phylogenetic tree and the other (named Brachypoda) comprising the several more advanced lines of ornithopod evolution.     

Tooth function and replacement in early Mesozoic ornithischian dinosaurs: implications for aestivation

Thulborn (1978, Leihaia II ) suggests that ornithischian dinosaurs of the upper Stormberg Series (Late Triassic-Early Jurassic) of southern Africa underwent aestivation during an annual dry season. His argument, based on an interpretation of tooth function and replacement in heterodontosaurids, is: (1) unequivocal evidence of tooth replacement is not seen, and (2) piecemeal replacement of the dentition would be incompatible with maintenance of a fore-aft grinding function of the teeth; therefore, the entire dentition must have been rapidly replaced as a unit during periods of non-feeding, i.e. during aestivation. However, study of tooth wear patterns in Lanasaurus, Lycorhinus , and Heterodontosaurus show that jaw movements during mastication were orthal (open-and-close) and lateral to medial, not forwards and backwards. Differences in degree of tooth wear would not interfere with masticatory movements. Patterns of differential wear indicate that tooth replacement was not periodic but continuous, as in other reptiles. Zahnreihen , with a Z-spacing of about 3.0, are recognizable. Replacement ceased in mature individuals. The dentition shows adaptations for prolonging its effective life despite heavy wear. Differential tooth wear is incompatible with the idea of replacement of the entire dentition as a unit during an hypothesized period of aestivation. Thulborn's suggestion of aestivation in fabrosaurid ornithischians is also shown to be unlikely.     

First Description of the Auditory Region of a Tremarctinae (Ursidae,Mammalia) Bear: The Case of Arctotherium angustidens

Here we present the first detailed morphological study of the auditory region of a tremarctine bear, the South American giant short-faced bear Arctotherium angustidens. We compared 19 specimens of A. angustidens with other tremarctines and ursines. Through the use of CT scans, we confirmed the presence of a recesus epitympanicus and an anterior incomplete septum of uncertain homology, not related with the septum bullae nor with the longitudinal septum formed by the ecto- and the entotympanic. A secondary crus formed by the lateral semicircular canal (LSC) with the posterior semicircular canal (PSC) of the inner ear was observed in A. angustidens, A. bonariense, Tremarctos ornatus, Ursus spelaeus, and Ursus arctos. This secondary crus was not previously reported for ursids. We also observed that the intraspecific variation in the auditory region of A. angustidens is related to 1) the position of the foramen postglenoideum, 2) the anterior projection of the bulla tympanica over the foramen lacerum and over the opening of the Eustachian tube (medial process of the bulla tympanica), and 3) the projection of the bulla tympanica over the posterior surface of the processus postglenoideus (tympanic process). In addition to this variation, we also identified the presence of interspecific variation in the external auditory region among Tremarctinae and Ursidae. These differences are related to the size of the processus mastoideus and the processus paraoccipitalis, the position of the foramen postglenoideum, and the presence/absence of contact between the bulla tympanica and the processus paraoccipitalis.     

Quo vadis eohippus? The systematics and taxonomy of the early Eocene equids (Perissodactyla)

The systematics and taxonomy of early Eocene equids are investigated. A paraphyletic sequence of equid taxa is recovered from a phylogenetic analysis of 40 taxa and 121 characters. This analysis supports the identification of Hyracotherium as a primitive equoid and its restriction to the genotype, Hyracotherium leporinum . Sifrhippus gen. nov. is erected for the sister taxon of all other equids, Hyracotherium sandrae Gingerich. Minippus gen. nov., the next more-derived equid clade, is erected for two small equids, M. index Cope and M. jicarillai nov. species. Arenahippus gen. nov. is erected for the next three sequentially more-derived equid taxa, A. grangeri Kitts, A. aemulor Gingerich, and A. pernix Marsh. The genus Xenicohippus , which is the next more-derived equid clade, is redefined to include X. craspedotum Cope. Eohippus Marsh, the next more-derived equid taxon, is resurrected for E. angustidens Cope. Pliolophus , the only early Eocene equid from Europe, is identified as the sister taxon to Protorohippus , a sequence of successively more-derived equid taxa consisting of P. montanum Wortman and P. venticolum Cope. Protorohippus venticolum is identified as the sister taxon of Orohippus . Systemodon Cope is resurrected for S. tapirinum Cope. This taxon has historically been placed within Hyracotherium yet this analysis allies it with Cymbalophus near the base of the perissodactyl radiation. © 2002 The Linnean Society of London. Zoological Journal of the Linnean Society , 134 , 141–256.     

广西崇左泊岳山巨猿洞早更新世的鼠科化石

最近在广西崇左泊岳山巨猿洞采集到大量步氏巨猿、猩猩、长臂猿等高等灵长类及伴生的属种丰富的哺乳动物化石。本文系统记述了该化石点小哺乳动物群中的优势群体——鼠科化石:似锡金小鼠(Mus cf.M.pahari)、似大林姬鼠(Apodemus cf.A.peninsulae)、细狨鼠(Hapalomys gracilis)、狭齿狨鼠(Hapalomys angustidens)、先社鼠(Niviventer preconfucianus)、安氏白腹鼠(Niviventer andersoni)、拟爱氏巨鼠(Leopoldamys edwardsioides)和似始家鼠(Rattus cf.R.pristinus)共6属8种,其中包括了5个绝灭种。研究表明,泊岳山巨猿洞鼠类主要属种的形态特征显然要比同地区的三合大洞显得原始,而较相似于重庆巫山龙骨坡的相关鼠类,因此推测其时代为早更新世早期,这与古地磁的测年结果(距今约180万年)相吻合。泊岳山巨猿洞的鼠类大部分均为东洋界成员以及树栖、半树栖及林地生活的种类,反映当时的自然景观为热带-亚热带的森林-林灌环境。泊岳山巨猿洞鼠科化石的研究丰富了我国南方早更新世巨猿-中华乳齿象动物群中小哺乳动物化石的记录,这对于探讨我国南方第四纪生物地层的划分将提供重要的信息。     

Crystal structures and kinetic properties of enoyl‐acyl carrier protein reductase I from Candidatus Liberibacter asiaticus

Huanglongbing (HLB) is a destructive citrus disease. The leading cause of HLB is Candidatus Liberibacter asiaticus. Fatty acid biosynthesis is essential for bacterial viability and has been validated as a target for the discovery of novel antibacterial agents. Enoyl−acyl carrier protein reductase (also called ENR or FabI and a product of the fabI gene) is an enzyme required in a critical step of bacterial fatty acid biosynthesis and has attracted attention as a target of novel antimicrobial agents. We determined the crystal structures of FabI from Ca. L. asiaticus in its apoform as well as in complex with b-nicotinamide adenine dinucleotide (NAD) at 1.7 and 2.7 Å resolution, respectively, to facilitate the design and screening of small molecule inhibitors of FabI. The monomeric ClFabI is highly similar to other known FabI structures as expected; however, unlike the typical tetramer, ClFabI exists as a hexamer in crystal, whereas as dimer in solution, on the other hand, the substrate binding loop which always disordered in apoform FabI structures is ordered in apo-ClFabI. Interestingly, the structure of ClFabI undergoes remarkable conformational change in the substrate-binding loop in the presence of NAD. We conclude that the signature sequence motif of FabI can be considered as Gly-(Xaa)₅-Ser-(Xaa)_n-Val-Tyr-(Xaa)₆-Lys-(Xaa)_n-Thr instead of Tyr-(Xaa)₆-Lys. We have further identified isoniazid as a competitive inhibitor with NADH.     

Equilibrium studies of zinc(II) and cobalt(II) binding to tripeptide analogues of the amino terminus of human serum albumin

Serum albumin is known to bind several divalent metal ions at the amino terminus of the protein. Two peptide analogues for the amino terminus of human albumin, L-aspartyl-L-alanyl-L-histidine-N-Methyl amide (AAHNMA) and glycylglycyl-L-histidine-N-methyl amide (GGHNMA) have been synthesized, and their interactions with Zn(II) and Co(II) ions have been studied using analytical potentiometry. The stability constants of the species and their distribution as a function of pH were determined in 0.16-M KNO₃ at 25°. Comparison of the modes of interaction of the Zn(II) and Co(II) with each of the above peptides indicate that, although Co(II) is a valuable tool for the study of Zn(II) interaction with metalloenzymes, it is considerably less useful as a Zn(II) model with small peptide molecules. The potentiometric properties of the two peptide-Zn(II) systems have been compared to the potentiostatic properties of the albumin-Zn(II) system. The results indicate that AAHNMA is a better analogue for the Zn(II)-HSA interaction than is GGHNMA. The findings suggest that the Zn(II)-HSA binding site is best described as a compound site containing both a histidyl and a neighboring carboxyl group.     

Some aspects of arginine assimilation in a strain ofStreptococcus sanguis

Like many arginolytic streptococci,Streptococcus sanguis P₄A₇ is auxotrophic for arginine (Arg) and can also use this amino acid as an energy source; its dissimilation via the arginine deiminase (ADI) pathway is potentially important in dental plaque metabolism. Arg uptake was investigated in chemostat-grown cells; two systems were found: a low-affinity system (A) and a high-affinity system (B). Both systems (a) functioned as well as pH 5.5 and 8.0 as at 7.0; (b) were insensitive to proton-conducting uncouplers and metabolic inhibitors, and (c) were unaffected by prior starvation of cells or their pre-energization with glucose. Thus, Arg uptake appeared to be energy-independent. Inhibition studies with Arg structural analogues indicated that both the carboxyl and guanidino functional groups and their spatial relationship are important as recognition sites in system A, while all three functional groups appear important in system B. It is suggested that system A represents the ADI pathway, whereas system B is used to satisfy the organism's auxotrophic requirement.     

Aposematic and cryptic Lepidoptera tested on the mouse

The toxicity of 53 species of Lepidoptera which are aposematic (a) at all stages of development; (b) as larvae but not as adults; (c) as adults but not as larvae, is compared with that of cryptic species, by means of a qualitative test consisting of intraperitoneal injection into the laboratory mouse. Points of interest which emerged from this study include (i) Pieris brassicae is toxic whether or not the larval diet contains sinigrin and mustard oils; (ii) a marked sexual dimorphism in toxicity is noted in several species; (iii) a yellow (recessive) variety of Callimorpha dominula (ab. lutea ) is less toxic than the typical form; (iv) P. brassicae pupae are acceptable to certain birds if the larvae are reared on artificial diet, but rejected (on account of taste or smell) if fed on cabbage; (v) only Arctia caja , out of 14 species tested, retains its toxicity when dried, and (vi) the gravid female Zygaena trifolii and her eggs kill the mouse in two to three minutes.     

Fretting about FRET: correlation between kappa and R

Molecular dynamics simulations were used to examine the structural dynamics of two fluorescent probes attached to a typical protein, hen egg-white lysozyme (HEWL). The donor probe (D) was attached via a succinimide group, consistent with the commonly-used maleimide conjugation chemistry, and the acceptor probe (A) was bound into the protein as occurs naturally for HEWL and the dye Eosin Y. The is found to deviate significantly from the theoretical value and high correlation between the orientation factor kappa and the distance R is observed. The correlation is quantified using several possible fixed A orientations and correlation as high as 0.80 is found between kappa and R and as high as 0.68 between kappa(2) and R. The presence of this correlation highlights the fact that essentially all fluorescence-detected resonance energy transfer studies have assumed that kappa and R are independent--an assumption that is clearly not justified in the system studied here. The correlation results in the quantities and < R(-)(6)> differing by a factor of 1.6. The observed correlation between kappa and R is caused by the succinimide linkage between the D and HEWL, which is found to be relatively inflexible.     

Flow-cytometric assessment of cellular poly(ADP-ribosyl)ation capacity in peripheral blood lymphocytes

Background  

Poly(ADP-ribosyl)ation is a posttranslational modification of nuclear proteins catalysed by poly(ADP-ribose) polymerases (PARPs), using NAD⁺ as a substrate. Activation of PARP-1 is in immediate response to DNA damage generated by endogenous and exogenous damaging agents. It has been implicated in several crucial cellular processes including DNA repair and maintenance of genomic stability, which are both intimately linked with the ageing process. The measurement of cellular poly(ADP-ribosyl)ation capacity, defined as the amount of poly(ADP-ribose) produced under maximal stimulation, is therefore relevant for research on ageing, as well as for a variety of other scientific questions.     

CAC – the neglected repeat

It is becoming increasingly clear that repetitive DNA is of biological significance as well as experimental importance. Here we review the information available about one type of repetitive DNA, the trinucleotide repeat (CAC)_n, and briefly compare it with other trinucleotide repeats. Although much work has been done in analysing DNA fingerprinting patterns produced using the synthetic oligonucleotide (CAC)₅ as a probe, there is relatively little information about individual (CAC)_n-containing sequences and their abundance, organisation and distribution in mammalian DNA. From the data that is available, it is clear that there are at least two areas that should repay further study: (1) the organisation and generation of long sequences that contain (CAC)_n motifs as part of a larger repeating unit (minisatellites) and (2) the distribution of small (CAC)_n sequences (microsatellites), in particular their relationship to genes.     

Molecular high-order harmonic spectra and its application to the generation of the isolated attosecond pulse

Molecular high-order harmonic generation (HHG) spectra from H₂ ⁺ and its application to the generation of the isolated attosecond pulses (IAPs) have been numerically investigated. Results show that (i) the 7th harmonic order is enhanced with the nuclei around the equilibrium internuclear, and as the internuclear distance increased, this enhanced harmonic produces a red-shift (even disappearance). Theoretical analyses show that the electronic transition between the ground and the 1st excited states is responsible for the red-shift enhanced harmonic. (ii) The harmonic spectra exhibit several maxima and minima, and a red-shift of these points is predicted as the internuclear distance increased. (iii) By properly choosing the internuclear distance, the harmonic yield is enhanced, and there is only the single quantum path contributing to the harmonic spectra. (iv) Further, by properly adding the half-cycle pulse as well as the spatial inhomogeneous effect, a 375 eV supercontinuum with a pulse enhancement of 3.9 dB and some attosecond X-ray pulses shorter than 60as can be produced.     

国产黄杨科五种植物的考订

对国产黄杨科５ 种植物作了分类学修订或补充： 将雀舌黄杨归入匙叶黄杨, 中间黄杨归入黄杨, 多毛板凳果归入板凳果, 双蕊野扇花归入羽脉野扇花; 恢复黄杨和尖叶黄杨的原学名;报道宜昌黄杨在湖南的新记录。     

Characterization of the murexide method: dual-wavelength spectrophotometry of cations under physiological conditions.

The experimental and theoretical bases of the murexide method of Ca²⁺ assay are presented. By studying murexide as well as a new indicator, tetramethyl murexide, the following results are obtained: (a) A dilutional artifact can be eliminated by selecting the wavelength in such a way that the absorbance of the indicator solution at the two wavelengths is the same; (b) binding constants of these indicators for typical mono-, di-, and trivalent cations are measured by the double reciprocal plot method; (c) with 100-μm indicator solutions, the linearity of Ca²⁺ assay is maintained up to 100 μm Ca²⁺; (d) the minimum detectable amount of Ca²⁺ can be as low as 0.8 μm with murexide and 0.5 μm with tetramethyl murexide; and (e) unlike murexide, tetramethyl murexide is insensitive to the pH change. It is concluded that the unique features of the murexide method are (i) low binding constant of indicators for Ca²⁺ and (ii) insensitivity to Mg²⁺ in an aqueous solution.     

Microwave fixation provides excellent preservation of tissue, cells and antigens for light and electron microscopy

Summary It was demonstrated that microwave energy used simultaneously in combination with low concentrations of glutaraldehyde (0.05%) and formaldehyde (2.0%) rapidly preserved light microscopic histology and excellent fine structural details, as well as a variety of cytoplasmic and membrane-bound antigens. Specimen blocks up to 1 cm³ can be fixed in as brief a time as 26 ms using a specially designed microwave device (ultrafast microwave fixation method). The fast microwave fixation method, using a commercially available device, was successfully used to preserve granule-bound rat mast cell chymase which was subsequently detected by a postembedding immunogold procedure. Control of the following parameters is important to the microwave fixation method: (1) specimens with one dimension less than 1 cm; (2) irradiation temperatures lower than 50°C; (3) irradiation times less than 50 s; (4) immediate replacement of the postirradiation solution with cold storage buffer; (5) fixing the specimen within 15 min after it is removed from its blood supply.