苏铁属植物叶表皮特征及其分类学和古生态学意义

苏铁属(Cycas)作为一类古老的裸子植物,经历了漫长的演化历史,因此,深入研究其形态特征与环境的相互关系,有望为古环境重建提供重要参考依据。本文分析西双版纳和深圳两地植物园栽培环境下27种苏铁属植物的叶表皮特征及气孔参数的差异,并进一步探讨气孔参数与系统发育的关系。结果表明:(1)苏铁属内叶表皮特征保守稳定,具有一定的分类学意义:依据表皮细胞及气孔器特征划分了四种叶表皮类型,可为苏铁现生植物或化石的鉴定提供参考。(2)四种叶表皮类型指示了不同的原生生境特征,对古环境具有一定的指示意义。(3)同一环境下,气孔参数在属内的种间差异显著,其次,气孔指数在属内变化与系统发育有关,除气孔指数具显著的系统发育信号外,其余气孔参数均无显著系统发育信号。本研究结果表明气孔参数法重建古大气CO2浓度时,需尽可能利用亲缘关系相近、叶表皮和生境皆相似的代理种,并明确气孔参数与大气CO2分压的相关关系在种间的异同,从而提高该方法的有效性。     

Correlation of pacing site in right ventricle with paced QRS complex duration

Background

Pacing from RV mid septum and outflow tract septum has been proposed as a more physiological site of pacing and narrower paced QRS complex duration. The paced QRS morphology and duration in different RV pacing sites is under continued discussion. Hence, this study was designed to address the correlation of pacing sites in right ventricle with paced QRS complex duration.

Fipronil enhanced natural occurrence of Fusarium solani (Hypocreales: Nectriaceae) on building infesting termite Heterotermes indicola Wasmann (Blattodea: Rhinotermitidae)

The Southeast Asian subterranean termite, Heterotermes indicola Wasmann (Blattodea; Rhinotermitidae), is recognized as a building infesting lower termite species in urban environment. The extensive use of chemical termiticides against aerial mud tubes and underground nests of H. indicola beneath the buildings could not suppress its infestation; however, it enhanced the environmental contamination and insecticide resistance. In the present study, we tried to control termites using naturally occurring entomopathogenic fungi Fusarium solani (Mart.) Sacc., along with sublethal concentrations of termiticide fipronil in no-choice feeding pathogenecity bioassay for 20?days. Termite mortality after 20?days of continuous exposure to highest fungal treatment 1?×?10⁹?conidia/mL was 10% exclusively, whereas 100% mortality was calculated just after 16?days of concurrently exposure to 5?ppm of fipronil and highest rate of fungus 1?×?10⁹?conidia/mL. These results indicated that insecticidal stress declined the immune response of termites and reduced the repellency of termites against fungal conidia by breaching the primary defense mechanism (allogrooming). This co-application of F. solani at suitable sublethal concentrations of fipronil showed the promising potential against termites that may reduce the selection pressure of pesticides and resistance risk by targeted pests, but further investigations are necessary for developing field trials.     

Protein synthesis in lactating guinea-pig mammary tissue perfused in vitro. I. Radiolabelling of membrane and secretory proteins

A method for the in vitro perfusion of isolated guinea-pig mammary tissue is described that allows the radiolabelling of secretory and membrane proteins. Glands were depleted of methionine, labelled with [35S]methionine for 5 min and perfused with medium containing an excess of unlabelled methionine for varying times. The structural integrity of the alveoli in the perfused glands appeared well maintained. Epithelial polarity was preserved and junctional complexes were evident. About 20% of the methionine provided in the medium was extracted by glands of 10 g wet weight under the labelling conditions employed. With chase periods from 15 to 40 min, 50-70% of the methionine was incorporated into trichloroacetic-acid (TCA)-precipitable material. The principal radiolabelled proteins recovered from the tissue fractions had Mrs and isoelectric points similar to the major secretory proteins (i.e. caseins and alpha-lactalbumin) of guinea-pig milk. Autoradiography of tissue sections at the resolution of the light microscope showed that secretory proteins were transported from sites of synthesis within secretory cells to the alveolar lumina after 45 min. These highly labelled secretory proteins could be almost completely removed from microsomal fractions by treatment with sodium carbonate solutions. Proteins with Mrs from 30 000 to 200 000 were detected in the washed membranes by SDS-polyacrylamide gel electrophoresis (SDS-PAGE) and fluorography. These labelled membrane-associated proteins persisted in the microsomal membrane fraction after chase periods from 7.5 to 40 min.     

Shifts in plant cell axiality: histogenetic influences on cellulose orientation in the succulent, Graptopetalum

The elongation of typical plant meristems can be explained, biophysically, by the cellulosic hoop reinforcement in the longitudinal walls of most of the cells. A cortical microtubule array is believed to govern the reinforcement alignment. The orientation of the reinforcement is studied here with polarized light. Transverse orientation appears to be invariant, regardless of division direction, in interior cells of at least some established meristems. Exceptional longitudinal reinforcement (i.e., in the direction of growth) is occasionally seen, however, in the outer epidermal wall of established Graptopetalum roots, leaves, and stems. It is found in pairs of elongate cells that arise from a longitudinal division. This behavior is prominent when the epidermis is shifting reinforcement to initiate new organs. Usually the division direction and the new cell long axis coincide; reinforcement parallels both. When these two factors are in marked opposition, as in certain longitudinal divisions of very broad cells, the reinforcement can follow the new cell's long axis even though this orients alignment perpendicular to the new wall. The normal prevailing effect of the division direction may relate to the formation of the cortical microtubule array parallel to the orientation of the preprophase band. The normally synergistic effect of the new cell's long axis may stem from the fact that when the band-like array occupies the smaller pair of anticlinal faces of the cuboidal cell (and hence parallels the cell's long dimension in surface view), it will have the densest and presumably most stable structure. Reinforcement orientation is seen as a function of at least two factors which bear on the stability of the newly forming array.     

Studies of bovine genital tracts: Mycoplasma isolations from dairy cows

Mycoplasma was isolated from the genital tracts of 8 of 96 culled dairy cows. Procedures were used to reduce the possibility of uterine contamination by vaginal fluids. The mycoplasma isolates were identified by the fluorescent antibody technique as: $\text{Mycoplasma bovigenitalium}$ (4), $\text{M. canadense}$ (1), an untyped bovine pathogen from the mammary gland designed as ST-6 (2), and an isolate that could not be identified with the labeled antibodies used in this study. All isolations were made from vaginal swabs, except in one case of pyometra where $\text{M. bovigenitalium}$ was isolated concurrently from the uterus and vagina, along with $\text{Pasteurella hemolyticum}$. These results suggest that mycoplasma may be found in the cervico-vaginal flora of some cattle but are rarely isolated from the uterine environment.     

Benzo(a)pyrene quinone metabolism in tracheal organ cultures.

The C^? methyl group of methionine-29 of RNAase was enriched with ¹³C. The synthesis involved the reaction of RNAase with ¹³CH₃I at pH 4. S-Methylmethionine-29 RNAase was recovered in 80% yield. This sulfonium derivative was subsequently demethylated with 0.1 M mercaptoethanol at pH 8.5, 25°C for 4 days. These conditions allowed the demethylation reaction to successfully compete with the reaction of the thiol with the four disulfide bridges in RNAase. After dialysis, concentration and chromatography, native RNAase with approx. 50% of its Met²⁹ methyl groups enriched in ¹³C was recovered as was unreversed S-Methylmethionine-29 RNAase. Both proteins showed full enzymatic activity toward cytidine 2′:3′-cyclic monophosphate. ¹³C-methyl signals from enriched RNAase and the sulfonium derivative were observed at 13.8 and 26.7 ppm from TMS respectively. Preliminary denaturation studies with the methylated protein suggest that ¹³C enrichment of methionine methyl groups in RNAase will be a useful technique for following the unfolding transition at these sites of the protein.     

抗菌肽改良设计及抗炎作用的研究进展

抗菌肽因其具有广谱抗菌活性、不容易引起抵抗性,被认为是先天免疫系统对抗微生物感染的多功能工具。然而,天然抗菌肽存在抗菌活性低、稳定性低、溶血性高等问题,使其较难应用于临床,所以研究人员对抗菌肽进行改良设计以期获得更高抗菌活性、更低溶血活性的新型抗菌肽。另外,天然抗菌肽作为一类免疫效应因子而被发现,其表现出的抑菌、免疫调节、内毒素中和等作用,使得研究人员对抗菌肽在抗炎作用的研究表现出极大的兴趣。就抗菌肽的药物设计方法及抗炎作用机制进行综述。     

Flux of lead in submerged plants and its relevance to a freshwater system

The fluxes of lead in submerged freshwater angiosperms, mosses and benthic algae were investigated by laboratory and field observations. Laboratory experiments showed that the initial uptake of lead by angiosperm shoots and Navicula sp. was rapid (up to 0.07 mg Pb g^?1 dry weight min ^?1 from a solution containing 1.0 mg Pb l^?1), and over-whelmingly passive. Mosses were especially efficient at sorbing lead from solutions containing less than 1.0 mg Pb l^?1 . Rates of uptake increased with rising external concentrations, but decreased with time. Anatomical and morphological characteristics of plant tissues affected metal flux and an epiphytic covering of Navicula (i.e., an Aufwuchs community) sorbed metal and reduced uptake into tissues by a third. Up to 90% of the lead sorbed in the first hour by shoots of Elodea canadensis Michx from a solution containing 1.0 mg Pb l^?1 was released within 14 days of transfer into a lead-free medium; 10% was irreversibly bound.Moss monitors placed in Ullswater, a lake with sediments containing up to 26 mg Pb g^?1 dry weight, confirmed that the metal is brought into circulation during turbulence, but not in periods of calm. Shoots of Elodea collected from the lake contained up to 0.3 mg g^?1 dry weight non-exchangeable lead. Young shoots tended to contain less than older shoots (0.12 compared with 0.3 mg Pb g^?1), and leaf more than stem tissues. The fluxes of lead from the environment through Aufwuchs and submerged plants are discussed.     

A three-dimensional representation for base composition of protein-coding DNA sequences

Multi-dimensional scaling is applied to our codon space data on the protein coding sequences of DNA from a wide variety of organisms in an attempt to find the smallest number of parameters which will accurately represent these sequences. I find that a three-dimensional representation is satisfactory. One of the three resulting co-ordinates separates eukaryotes and their associated viruses from prokaryotes and their associated phages, while an orthogonal co-ordinate separates those organisms capable of synthesizing proteins (eukaryotes and prokaryotes) from those not so capable (viruses and phages). Mitochondria show no relation in our plots to any of these groups.     

Inductive activity and enduring cellular constitution of a supernumerary apical ectodermal ridge grafted to the limb bud of the chick embryo.

Apical ectodermal ridges (AERs) isolated from 3- to 4-day chick and quail embryos were prepared by means of trypsinization and microdissection and then were grafted to the dorsal or ventral side of a host chick wing bud. They induced supernumerary limb outgrowths from the host bud showing, respectively, a bidorsal or biventral organization, as determined by the patterns of feather germs. The grafted ridge cells persisted, as revealed by histological sections of supernumerary chick limb parts growing under the influence of quail AERs, whose cells are readily distinguished after application of the Feulgen reagent.These results show that the AER induces limb outgrowth regardless of whether it is associated with dorsal or ventral limb ectoderm and that its continued existence is not dependent on contributions of ectodermal cells from the opposed ectodermal faces of the limb bud. The AER is pictured as maintaining the subjacent mesoderm in a condition of developmental plasticity without specifying its differentiation with respect to the proximodistal axis. It remains uncertain whether the positional values of cells that develop under the influence of the AER arise within these cells themselves or appear in response to influences from proximal sources.     

Studies on the UDP-sugar hydrolases from Escherichia coli and Salmonella typhimurium

A simple procedure for purification of the UDP-sugar hydrolase from Escherichia coli is described. The enzyme has an apparent molecular weight of 61,000. The UDP-sugar hydrolase from Salmonella typhimurium has been solubilized and partially purified from total cell membranes. According to several criteria, antibodies raised against the purified E. coli enzyme do not seem to react with partially purified Salmonella enzyme.     

Thermoregulatory responses to temperature manipulation of the spinal cord in the marmot

Yellow-bellied marmots (M. flaviventris) acclimated to T_a = 20 °C were implanted with U-shaped polyethylene thermodes in the peridural space of the spinal cord. Decreasing the temperature of the cervical, thoracic, or lumbar areas of the cord increased heart rate, electromyographic activity, and oxygen consumption in the animals. These responses differed qualitatively from those elicited by heating the same cord areas, indicating specificity of the response to the temperature change.Increases in heat production were proportional to the amount of cooling of the cord. The thoracic area was found to be more thermosensitive than the lumbar area. No behavioral or physical thermoregulation was apparent when the spinal cord temperature was changed in these animals.In addition to the conclusion that regulation of spinal cord temperature may be important in the euthermic marmot, it was postulated that the temperature receptors located in the thoracic cord of the marmot may be important in maintaining shivering thermogenesis during arousal from hibernation.     

Kinetics of dithionite reduction of the heme nonapeptide of cytochrome c

The kinetics of dithionite reduction of the oxidized heme nonapeptide fragment of horse heart cytochrome c have been measured as a function of ionic strength at pH 7 and pH 9 by the stopped-flow technique. Dithionite concentration dependences indicate that the radical anion monomer, SO2-., is the active reductant. The pH 7 ionic strength dependence suggests that the heme peptide is reacting as a negatively charged molecule (its overall charge is calculated to be -1). Comparison of these results with the known rate of dithionite reduction of cytochrome c indicates that the heme nonapeptide has substantially greater inherent reactivity than cytochrome c, perhaps due to the greater accessibility of the heme.     

The control of the anteroposterior and dorsoventral axes in embryonic chick limbs constructed of dissociated and reaggregated limb-bud mesoderm

In the 3- to 4-day embryonic avian limb bud, a unique zone of mesodermal tissue is located posteriorly at the junction of bud and body wall. Appropriately grafted to a host limb bud, it induces the formation of a supernumerary limb outgrowth from preaxial tissue and determines that its posterior side will face the graft. It is called the zone of polarizing activity (ZPA).When limb-bud mesoderm is isolated, dissociated, reaggregated centrifugally, jacketed in the mesoderm-free hull of another limb bud, and grown as a graft on a host embryo, the recombinant frequently forms a limb-like structure terminating in digits that fail to show differentiation with respect to the anteroposterior axis. When, however, a bit of ZPA tissue is implanted in the recombinant subjacent to the anterior or posterior margin of the ectoderm, the resulting outgrowth shows a characteristic anteroposterior order of digits that corresponds to the placement of the implant, regardless of its relationship with the anteroposterior axis of the ectoderm or of the host embryo.Dorsoventral differentials have been recognized only in limbs formed from reaggregated leg-bud mesoderm. The direction of the dorsoventral axis always corresponds to the original axis of the ectodermal jacket regardless of the orientation of the recombinant on the host.     

Distribution of actin and myosin in mouse trophoblast: Correlation with changes in invasiveness during development in vitro

Mouse trophoblast is an invasive tissue that undergoes conversion to a noninvasive state during normal development. We examined the distribution of actin and myosin during trophoblast development in vitro with double label fluorescence microscopy using fluoresceinated subfragment-1 of myosin to identify actin and indirect immunofluorescence with rhodamine-conjugated antibody to detect myosin. During the outgrowth stage trophoblast spread as a sheet by active movement of the marginal cells. These cells exhibited different patterns of actin and myosin distribution in connection with lamellar extension and fiber formation. Marginal and submarginal cells were packed with overlapping layers of actin fibers, some of which were organized into a lattice that extended throughout the trophoblast. The cytoskeletal function of the fibers appeared to involve maintenance of the cells in a coherent sheet. Cessation of trophoblast spreading was associated with conversion of the cell sheet into a cell network. Cells stained more densely for actin and myosin and contained distinctive actomyosin condensations in the cortex and the cytoplasm. At the same time there was disorganization and then loss of the actin fiber system. These changes in actin and myosin distribution may be associated with mechanisms that control invasiveness by limiting trophoblast expansion.     

Physiological,but not fitness,effects of two interacting haemoparasitic infections in a wild rodent

In contrast to the conditions in most laboratory studies, wild animals are routinely challenged by multiple infections simultaneously, and these infections can interact in complex ways. This means that the impact of a parasite on its host’s physiology and fitness cannot be fully assessed in isolation, and requires consideration of the interactions with other co-infections. Here we examine the impact of two common blood parasites in the field vole (Microtus agrestis): Babesia microti and Bartonella spp., both of which have zoonotic potential. We collected longitudinal and cross-sectional data from four populations of individually tagged wild field voles. This included data on biometrics, life history, ectoparasite counts, presence/absence of microparasites, immune markers and, for a subset of voles, more detailed physiological and immunological measurements. This allowed us to monitor infections over time and to estimate components of survival and fecundity. We confirm, as reported previously, that B. microti has a preventative effect on infection with Bartonella spp., but that the reverse is not true. We observed gross splenomegaly following B. microti infection, and an increase in IL-10 production together with some weight loss following Bartonella spp. infection. However, these animals appeared otherwise healthy and we detected no impact of infection on survival or fecundity due to the two haemoparasite taxa. This is particularly remarkable in the case of B. microti which induces apparently drastic long-term changes to spleen sizes, but without major adverse effects. Our work sheds light on the ecologies of these important zoonotic agents, and more generally on the influence that interactions among multiple parasites have on their hosts in the wild.     

Limb outgrowth in the chick embryo induced by dissociated and reaggregated cells of the apical ectodermal ridge.

Mesodermal cores of the stage 19 chick leg bud were capped with an intact apical ectodermal ridge (AER) or with strips cut from centrifugal pellets formed from Pronase-dissociated AERs. They were then covered with embryonic back-skin ectoderm and grown as grafts to the somite region of a host embryo. Control mesoderms were capped with centrifugal aggregates of nonridge limb ectoderm or similarly treated back-skin ectoderm, with ethanol-killed AERs or with no ectodermal cells other than the enveloping back-skin ectoderm.Controls were vascularized slowly and atypically and showed little outgrowth, forming only proximal skeletal structures. Recombinants equipped with AER cells were vascularized more fully and promptly and began vigorous growth after brief delay, forming legs with all skeletal segments represented, including claw-tipped toes. The latter were arranged in anteroposterior order corresponding to the original polarity of the mesoderm.Histological sections of recombinants made with cytologically distinctive quail AERs reveal that the cap of ridge cells, whether initially intact or reaggregated beneath the back-skin envelope, undergo a period of reorganization, forming a typical AER at the apex of the chimeric appendage after 48 hr. Meanwhile vigorous growth of the recombinant continues.These results show that the AER can cooperate with nonlimb ectoderm in promoting the morphogenesis of successively more distal levels of the limb skeleton. They also show that dissociated ridge cells can reorganize a typical AER at the apex of the limb mesoblast, meanwhile exercising their inductive effect on it.     

Incorporation of a follicle stimulating hormone used for embryo transfer in cattle into multilamellar liposomes

A commercially available follicle stimulating hormone preparation (FSH-P) was successfully incorporated into multilamellar vesicles (liposomes). Multilamellar liposomes were found to contain 9.39 +/- 1.14 mg FSH-P (n=4) per 100 mg phospholipid or approximately 19.0% of the original material used to form the liposomes. A 1% solution of Triton X-100 incubated with liposomes containing FSH-P for one-half hour at 37 degrees C released 33% of the entrapped FSH-P; more than 99% of the entrapped FSH-P was released when liposomes were incubated with a 2% solution of Triton X-100. Entrapment of FSH-P increased proportionally to the mole percentage of stearylamine used in liposome formation, suggesting that FSH-P is entrapped in the aqueous interstices of the cationic liposomes. Entrapment of FSH-P in stable liposomes suggests that these multilamellar vesicles may be useful as a FSH-P delivery vehicle used for the superovulation and embryo transfer of food animals.     

Crystal and molecular structure of piperidinium μ-acetato-di-μ-1,2-benzenediolato-bis-1,2-benzenediolatoferrate(III), (C5H12N)3 [(CH3COO){Fe(C6H4O2)2}2]: a compound of relevance to the 2Fe-active site of the respiratory protein hemerythrin

The title compound is readily prepared as chunky purple-black crystals with the space group P$\text{4}$. The crystal structure was determined to a conventional R value of 0.088. The two FeO₆ octahedra in the anion share a common edge using oxygens of two equatorially disposed catechol dianions and one pair of adjacent coordination sites is bridged by the acetate moiety. Bidentate catecholates complete the coordination array. The Fe-O distances range from 1.95(3) to 2.03(3)Å with chelate bite angles of 82.3(9)° and 84.0(4)°. The basal Fe₂O₂ ring is folded about the O-O vector with dihedral angles of 150.0° and 149.4°. For the two dimers pres per asymmetric unit, Fe-Fe separations are 3.137(4) and 3.172(4)Å. Extensive hydrogen bonding creates rosettes of four anions and eight cations alternating about inversion centers. These structural data together with magnetic and spectroscopic properties of the dimer strongly suggest that such a (near) confacial bioctahedral structure is not an appropriate model for the active site of the respiratory protein hemerythrin.