烟草内生菌根真菌的分离鉴定

本文报道了从烟草(Nicotiana tabacum L.)的根际土壤中分离出内生菌根真菌的孢子,用单孢接种烟苗并在温室内水培条件下培养。选出能在烟草上形成菌根的菌株,经过再次单孢接种确认后,进行种的鉴定。从分离的8个菌株中已鉴定出球囊霉属(Glomus)的3个新记录种:漏斗孢球囊霉[G.mosseae(Nic.& Gerd.)GeM.& Trappe]、根内孢球囊霉(G.intraradics Schenck & Smith)和联结球囊霉(G.constrictum Trappe)。     

Chromosome-mediated transfer of murine alleles for hypoxanthine-guanine phosphoribosyl transferase (HGPRT) and ouabain resistance into human cell lines

Genetic drug-resistance markers were transferred via purified metaphase chromosomes from mouse L cells into the human fibrosarcoma line HT1080 and HeLa S3 cells. Interspecific chromosome-mediated transfer of hypoxanthine-guanine phosphoribosyl transferase (HGPRT; EC 2.4.2.8) from mouse L cells into HGPRT^– HT1080 cells occurred at a frequency of approximately 1×10^–7. The presence of the mouse allele for HGPRT in transferent isolates was confirmed by isoelectric focusing. Transfer of ouabain resistance from mouse L cells to HT1080 and HeLa S3 cells occurred at an average frequency of approximately 4×10^–7. Expression of the mouse trait in transferent isolates was confirmed by their ability to withstand doses of ouabain which would be lethal to spontaneous ouabain-resistant mutants of the human cells but not to mouse L cells. Ouabain-resistant transferents of human cells showed 10⁴- to >10⁵-fold enhanced drug resistance, characteristic of either wild-type or mutant alleles, respectively, from ouabain-resistant donor L cells. Unstable expression of the transferred phenotypes in the absence of selection was seen in some isolates, but expression was lost at slow rates.This work was supported by National Institutes of Health Grant GM30383/21665 to RMB, Core Grants CA14051 to S. E. Luria and CA24538 to E. Mihich, and institutional predoctoral Training Grant GM07287.     

Characterization of some East African Theileria species isolates by isoenzyme analysis, with particular reference to T. parva

Eight different isolates of Theileria parva and one isolate of T. taurotragi, in the form of intra-lymphocytic schizonts and/or purified piroplasms, were subjected to isoenzyme analysis for 24 enzymes by both isoelectric focusing in agarose and electrophoresis in starch gel. Twelve enzymes distinguished between T. parva and T. taurotragi; five enzymes (HK, GPI, PEP1, LDH and SOD) showed variations within T. parva. The metabolism of the host cell was affected by schizont infection, which masked intraspecific variations. Piroplasms were of more potential value for characterization of T. parva.     

Carbonic acid as the host signal for the development of parasitic stages of nematodes

Petronijevic T., Rogers W. P. and Sommerville R. I. 1985. Carbonic acid as the host signal for the development of parasitic stages of nematodes. International Journal for Parasitology15: 661–667. This paper gives results on which may be based an identification of the component of the system CO₂ + H₂O ai H₂CO₃ ai H⁺ HCO₃^? which acts as the stimulus from the animal host for some nematodes. Using infective juveniles of Nematospiroides dubius and Haemonchus contortus, the effects on exsheathment of (1) low pCO₂ values, (2) the presence of carbonic anhydrase in the stimulating medium, and (3) the inhibition of carbonic anhydrase within the juveniles have been examined. The results lead to the suggestion that it is the “readily available” undissociated H₂CO₃, or H₂CO₃ + HCO₃^? which is the critical factor in the stimulus for development. The wide range of [H⁺]s over which “readily available” H₂CO₃ is present in physiological environments suggests that this host signal may be important for infection with many species.     

食蟹猴疟原虫晚期卵囊、成孢子细胞与子孢子扫描电镜观察

本研究对实验感染食蟹猴疟原虫后9、10和14天的斯氏按蚊阳性蚊胃,进行扫描电镜观察。晚期(分化的)卵囊表面呈现凹凸不平皱褶。成孢子细胞体常呈圆球形或椭圆形,表面光滑,子孢子芽从其表面长出。子孢子体细长,稍弯曲,体表光滑;虫体前部较细,顶端稍平,后部稍粗,末端钝圆。本文对成孢子细胞不同发育阶段的形态予以较详细描述,对子孢子出囊方式做了初步讨论。     

Adenine nucleotide translocase-dependent anion transport in pea chloroplasts

Pea chloroplasts were found to take up actively ATP and ADP and exchange the external nucleotides for internal ones. Using carrier-free [¹⁴C]ATP, the rate of nucleotide transport in chloroplasts prepared from 12–14-day-old plants was calculated to be 330 μmol ATP/g chlorophyll/min, and the transport was not affected by light or temperature between 4 and 22°C. Adenine nucleotide uptake was inhibited only slightly by carboxyatractylate, whereas bongkrekic acid was nearly as effective an inhibitor of the translocator in pea chloroplasts as it was in mammalian mitochondria. There was no counter-transport of adenine nucleotides with substrates carried on the phosphate translocator including inorganic phosphate, 3-phosphoglycerate and dihydroxyacetone phosphate. However, internal or external phosphoenolpyruvate, normally considered to be transported on the phosphate carrier in chloroplasts, was able to exchange readily with adenine nucleotides. Furthermore, inorganic pyrophosphate which is not transported by the phosphate carrier initiated efflux of phosphoenolpyruvate as well as ATP from the chloroplast. These findings illustrate some interesting similarities as well as differences between the various plant phosphate and nucleotide transport systems which may relate to their role in photosynthesis.     

The S-state dependence of Cl binding to plant Photosystem II

A combined single-turnover flash and ³⁵Cl NMR technique has been used to monitor S-state dependence of Cl⁻ binding to PS-II particles derived from mangrove (Avicennia marina). No detectable high-affinity binding was found to particles in the S₀ and S₁ states, but binding with an affinity comparable to that which activates O₂ evolution was found in the S₂ and S₃ states.     

The amino acid transport systems of the autotrophically grown green alga Chlorella

The kinetic analysis of l-amino acid uptake by the green alga Chlorella revealed at least seven different uptake systems to be present in cells grown autotrophically with nitrate as nitrogen source. There is a ‘general system’ which transports most neutral and acidic amino acids, a system for short-chain neutral amino acids including proline, a system for basic amino acids including histidine, a special system for acidic amino acids, and specific systems for methionine, glutamine and threonine. The ‘general system’ is possibly the same as that which can be stimulated by incubation of cells in glucose plus ammonium (Sauer, N. (1984) Planta 161, 425–431). The incubation of Chlorella in glucose induces the increased synthesis of six amino acid uptake systems, namely the above-mentioned system for short-chain neutral amino acids, a threonine system, a methionine system, and a glutamine system. These results indicate that the uptake of l-amino acids by the green alga Chlorella is as complex as in other free-living organisms such as bacteria or yeast. The small number of amino acid uptake systems found in cells of higher plants, i.e. two or three, seems therefore to be a consequence of integration of the cells in a tissue supplying a relatively constant environment, and not a consequence of autotrophic growth on mineral carbon and mineral nitrogen.     

Determination of membrane potential with lipophilic cations: correction of probe binding

The binding of lipophilic ions to the membrane of envelope vesicles from Halobacterium halobium was examined in the absence and presence of membrane potential. The lipophilic ions used constitute a homologous series of (Phe)₃-P⁺-(CH₂)_n-CH₃ (n = 0–4) and tetraphenylphosphonium (TPP⁺). In the absence of membrane potential, the amounts of binding were proportional to the probe concentration in the medium when the concentration is dilute. Upon illumination, interior negative membrane potential is generated which induces the uptake of phosphonium cation probe. 2 μM were employed as the initial probe concentration. The real membrane potential was evaluated by means of extrapolation to the state of no binding: The values of for various probes are plotted against the binding coefficient. Here, C_i^app is the apparent intra-vesicular concentration of the probes which is calculated without consideration of bound probes. The ordinate intercept of the plot gives the true concentration ratio, and from this the membrane potential is evaluated. The membrane potential-dependent binding was analysed with a model: the membrane is split into two halves, outer and inner half, and the amounts of bound probes in each region are governed by the concentration in the contiguous solution. We obtained a formula which describes amounts of binding as a function of the membrane potential.     

Molecular aspects of the bilayer stabilization induced by poly(l-lysines) of varying size in cardiolipin liposomes

The interaction between poly(l-lysines) of varying size with cardiolipin was investigated via binding assays, X-ray diffraction, freeze-fracture electron microscopy, and ³¹P- and ¹³C-NMR. Binding of polylysines to the lipid only occurred when three or more lysine residues were present per molecule. The strength of the binding was highly dependent on the polymerization degree, suggesting a cooperative interaction of the lysines within the polymer. Upon binding, a structural reorganization of the lipids takes place, resulting in a closely packed multilamellar system in which the polylysines are sandwiched in between subsequent bilayers. Acyl chain motion is reduced in these liquid-crystalline peptide-lipid complexes. From competition experiments with Ca²⁺ it could be concluded that when the affinity of the polylysine for cardiolipin was much larger than that of Ca²⁺, a lamellar polylysine-lipid complex was formed, irrespective of whether an excess of Ca²⁺ was added prior to or after the polypeptide. When the affinity of the polylysine for cardiolipin was less or of the same order as that of Ca²⁺, the lipid was organized in the hexagonal H_II phase in the presence of Ca²⁺. These results are discussed in the light of the peptide specificity of bilayer (de)stabilization in cardiolipin model membranes.