鼎突多刺蚁群体结构和生活史的研究

本文报告了鼎突多刺蚁(Polyrhachis vicina Roger)的群体结构和生活史。通过研究表明,鼎突多刺蚁一年发生一代,以蚁后、雄蚁、工蚁、幼虫和卵越冬。卵和幼虫在冬天发育停滞(或极慢)。到了春天,随着气温的上升,卵和幼虫又恢复正常发育。据室内人工饲养观察,卵的发育历期为23.8±2.5天(平均温度26℃)幼虫为20.4±4.4天(26℃),工蚁蛹为19.8±5.5天(27℃)。成长工蚁在5—11月出现;8—11月,雄蚁从蛹中羽化;10月,雌蚁从蛹中羽化。雌蚁分飞交尾后,进入邻近蚁巢或回到原巢,脱翅成为蚁后。蚁巢内存在着多后现象。     

Competition in the gradostat: the role of the communication rate

In this paper we study a mathematical model of competition between two species of microorganisms for a single limiting nutrient in a laboratory device called a gradostat. A gradostat consists of several (we consider only two) chemostats (CSTR's) connected together so that material can flow between the vessels in such a way that a nutrient gradient is established. Our model is a slightly modified version of one considered recently by Jäger et al. [3], in that the rate of exchange of material between the two vessels (the communication rate) is allowed to differ from the dilution rate. The outcome of competition turns out to be surprisingly sensitive to variation of the communication rate. We identify several coexistence regimes in parameter space and describe a method for obtaining operating diagrams for given pairs of competing microorganisms.Research supported in part by NSF Grant DMS 8521605     

Base and conformational specificity of an amine modification of DNA

We have investigated the site and conformational preference of the reaction of a formaldehyde/amine reagent with DNA. Previous investigations of this laboratory have established that this reagent will react with native DNA, placing a positively charged amine moiety on the duplex that will survive exhaustive dialysis. The resulting adduct is duplex and base stacked in character, possessing B backbone geometry with a higher average winding angle and exhibiting remarkable stability with respect to the A-form, Z-form, or the single-strand denaturated species. In this current investigation, we have found that the stability of the adduct is dramatically reduced if the DNA is converted to mononucleotides, thus obviating the usual approach of nuclease digestion and chromatography for the identification of the modified nucleotides. Using indirect approaches, we have established that the reactive site that survives removal of the equilibrium concentrations of CH2O and amine is the exocyclic amino group of the guanine bases. This conclusion is based on (1) the positive correlation between GC content and the extent of adduct formation under standard reaction conditions (27 degrees C, 0.63M CH2O, 0.007M n-butylamine, pH 7); (2) decreases in the level of substitution of amine in DNA, which has this site blocked by trinitrobenzene modification; and (3) failure of poly(dI-dC) to retain amine upon dialysis. Raman spectra of the derivatized poly(dG-dC) show enhanced 2'-endo B character, with no marked shifts in the position of any of the lines, indicating the absence of any ring structures involving the N7 and the 06 of G. In standard reaction mixtures, other sites may react but this phenomenon appears to be minimal under conditions that do not favor fluctuational opening of base pairs. In the latter case, excess loading of amine on high GC content polymers produces a CD spectrum that is similar to one produced by poly(dA-dT) in the "X"-form [M. Vorlickova, E. Minyat, and J. Kypr (1984) Biopolymers 23, 1-4]. This conformation is lost, however, upon removal of excess reagents by dialysis and cannot be reestablished, in the absence of unbound amine and formaldehyde. The reaction is specific for the B-form of polynucleotides as demonstrated by the failure of poly(dG-m5dC) in the stable Z-form to exhibit substantial reaction. The B-form of this polymer will react readily with the retention of 0.23 moles amine/mole nucleotide under our standard reaction conditions.(ABSTRACT TRUNCATED AT 400 WORDS)     

Cytostatic effect of antiestrogens in lymphoid cells: relationship to high affinity antiestrogen-binding sites and cholesterol

The antiproliferative effect of 10(-6) M antiestrogens in an estrogen receptor-negative lymphoid cell line (K36) was enhanced in lipoprotein-poor growth medium. The enhancement was not due to increased bioavailability because cellular uptake of [3H]tamoxifen was not increased and the lipoprotein fraction of serum had negligible [3H]tamoxifen-binding capacity. Cholesterol and lipoproteins, but not mevalonate, reversed the cytostatic effect of antiestrogens. Reversal by cholesterol was dose-related (10(-7) M to 10(-5) M), while that by lipoproteins could also be demonstrated in medium undepleted of lipoproteins. The cytostatic efficacy of a series of ten compounds correlated well with their relative binding affinities for solubilized antiestrogen-binding sites from K36 cells when log IC50 values (concentration required to reduce [3H]thymidine incorporation by 50%) were plotted against log RBA50 values (concentration required to reduce [3H]tamoxifen binding by 50%) (correlation coefficient 0.94). Transmission electron microscopy of antiestrogen-treated cells showed evidence of disordered cytokinesis which was partially reversed by cholesterol. These observations implicate the antiestrogen-binding protein in the antiproliferative effect of antiestrogens in nonestrogen target cells.     

The insulin A and B chains contain structural information for the formation of the native molecule. Studies with protein disulphide-isomerase.

It has been shown previously [Tang, Wang & Tsou (1988) Biochem. J. 255, 451-455] that, under appropriate conditions, native insulin can be obtained from scrambled insulin or the S-sulphonates of the chains with a yield of 25-30%, together with reaction products containing the separated A and B chains. The native hormone is by far the predominant product among the isomers containing both chains. It is now shown that the presence of added C peptide has no appreciable effect on the yield of native insulin. At higher temperatures the content of the native hormone decreases whereas those of the separated chains increase, and in no case was scrambled insulin containing both chains the predominant product in the absence of denaturants. Both the scrambling and the unscrambling reactions give similar h.p.l.c. profiles for the products. Under similar conditions cross-linked insulin with native disulphide linkages can be obtained from the scrambled molecule or from the S-sulphonate derivative with yields of 50% and 75% respectively at 4 degrees C, and with a dilute solution of the hexa-S-sulphonate yields better than 90% can be obtained. The regenerated product is shown to have the native disulphide bridges by treatment with CNBr to give insulin and by the identity of the h.p.l.c. profile of its peptic hydrolysate with that for cross-linked insulin. It appears that the insulin A and B chains contain sufficient information for the formation of the native molecule and that the role of the connecting C peptide is to bring and to keep the two chains together.     

原生质体来源的大白菜悬浮细胞系的超低温保存

原生质体来源的大白菜 Brasstca campessris var.pekinsis 悬浮细胞系在二甲亚砜的保护下,能在液氮中(-196℃)长期冻存。加入山梨醇能增强保护作用;而加入甘露糖则降低保护作用。培养基对冻存也有明显的影响。在液氮中存放的时间长短对细胞存活率没有多大影响。冻后相对活性最高可达75.4％,恢复生长快,化冻后重新悬浮培养6天,生长量可达300-500％。遮光比不遮光对恢复更有利。冻存后恢复生长的悬浮细胞,能与未经冰冻的对照一样进行原生质体分离和培养。     

Growth analysis ofQuercus serrata seedlings withinMiscanthus sinensis grass canopies differing in light availability

The effects of different light regimes on the survival, growth and morphology ofQuercus serrata seedlings were studied in canopies ofMiscanthus sinensis. The seedlings of various ages (0–3 yr) were grown in three light regimes: under a denseM. sinensis canopy (TG plot) receiving 2.5%–8.7% of full sunlight, under a relatively sparse canopy (SG plot) receiving 3.8%–16.1% of light and in an adjacent open site (NG plot). There was a little difference in the survival ofQ. serrata seedlings among the three plots. Height and diameter of stem and total leaf area of the seedlings were significantly lower in the shadier plots. However, the first (bottom) flush of the stem was significantly longer in the TG plot than in the NG and SG plots. Total dry weights of individual 1- and 2-yr-oldQ. serrata seedlings in the TG plot were reduced to about one-twelfth of those in the NG plot. Although the relative proportion in dry weight of each organ did not differ significantly among the plots, leaf area ratio, specific leaf area and stem height per unit dry weight were significantly higher in shadier plots. The leaf area per unit stem height was increased considerably in the sunnier plots.     

Inhibited enzyme electrodes. Part 3: A sensor for low levels of H2S and HCN

It is shown that an inhibited enzyme electrode, using cytochrome oxidase, will respond to H₂S, HCN and azide ion. For all three inhibitors the kinetics of the inhibition and recovery processes have been analysed using the theoretical model presented previously (Albery et al., 1990a). Rearrangement of the differential equation describing inhibition and the development of the necessary software has enabled us to obtain values of the concentration of inhibitor in a matter of seconds after exposure of the sensor. The sensor will measure concentrations of H₂S down to 1 ppm in the gas phase and concentrations of HCN and azide ion down to 0·4 μmol dm⁻³ in the solution