华西银腊梅挥发油化学成分的研究

用水蒸气蒸馏法提取华西银腊梅挥发油,并用气相色谱-质谱(GC-MS)联用技术对其挥发油的化学成分进行分析,结果共鉴定了其中的39种成分,所鉴定成分含量约占总检出量的87.83%。其化学成分主要为(Z,Z)-9,12-十八碳二烯酸甲酯(9.00%),壬醛(5.83%),二十一烷(5.69%),二十烷(5.08%),辛炔酸(4.50%),2,6,10,15-四甲基十七烷(3.93%),(Z)-6-十八烯酸甲酯(3.65%),3,8-二甲基十一烷(3.52%),1-十六碳炔(3.31%),肉豆蔻酸(2.86%),月桂醛(2.81%),壬酸(2.23%),5,6,7,7α-四氢-4,4,7α三甲基-2(4H)-苯并呋喃酮(2.18%)等。     

海南俄贤岭石灰岩山地海南大戟灌丛群落研究

根据样方调查,对海南俄贤岭自然保护区海南大戟灌丛群落的种类组成、外貌、结构特征和物种多样性进行分析。结果表明,在700m2样地中,有维管植物77种,隶属于47科70属。群落中乔木的个体数量很少,主要由灌木和草本组成,灌木层主要优势种为海南大戟等。群落外貌常绿,生活型以小高位芽为主,占22.08%;按照Raunkiaer的频度等级定律,属于B级的种类最多,频度值为43.42。整个群落的物种丰富度Magarlef指数为8.56,Shannon-Wiener指数为1.38,Simposon为0.90,均匀度指数为0.32。群落各层次的丰富度格局表现为灌木层>草本层>乔木层>藤本植物,多样性格局为灌木层>乔木层>草本层<(>)藤本植物,均匀度格局为乔木层>藤本植物>灌木层>草本层。     

Morphological forms and viability of Campylobacter species studied by electron microscopy.

Electron microscopic studies of Campylobacter revealed that different morphological forms predominate at different parts of a colony. At the periphery, cells were almost all spirals, while in the center of the colony cells were mainly coccus shaped. Unusual ring-shaped cells, "donuts", were observed in the raised, peripheral region of the colony. Donut or ring forms have not previously been reported for Campylobacter organisms. Our data indicate that young or actively growing cells are mainly spiral shaped. Older cells undergo a degenerative change to coccoid forms. The donut shape appears to be an intermediate stage between spirals and cocci. Comparisons of plate counts of actively growing and inactive cells confirmed that coccoid cells are probably nonviable.     

Value of cane trash in nitrogen nutrition of sugarcane

The significance of trash containing 0.3 to 0.5% N in the N nutrition of sugarcane (Saccharum hybrid sp.) was investigated in pot- and field experiments using¹⁵N-labelled trash. The data obtained from the pot study with 2 silty-clay loams (a Humic Nitosol and a Humic Acrisol) showed that surface-applied trash (10 tonnes/ha), although ground to pass a 1-mm sieve, contributed less than 10% of N removed by sugarcane. Uptake of trash N was most active during the initial 6 months of the experiment though at the end of the study period of 18 months less than 15% of trash N was altogether recovered by sugarcane. In the absence of fertilizer N in a field study on the Humic Acrisol (C/N ratio 22), unground trash (5 tonnes. ha⁻¹) depressed soil N uptake by sugarcane by immobilizing available soil N. The field study moreover confirmed that the contribution of trash N in the supply of N to sugarcane is negligible. The value of trash would reside in its capacity to increase over the long term the organic matter level in the soils.     

Phosphoinositide breakdown and evidence for protein kinase C involvement during human NK killing

Conjugation between human NK cells and susceptible target cells (K562 and Jurkat) leads to breakdown of inositol lipids in the effector cells but not when conjugated with resistant target cells. Extracellular Ca2+ is required for this activation. Sphingosine inhibits NK killing in both normal and IL-2-activated NK cells. Phorbol esters, TPA, and PDBU enhanced NK killing at low concentrations, where 4-alpha-PDIDE did not. The diacylglycerol derivative OAG increased NK cell killing and activated PKC from human lymphocytes. These results strongly suggest that phosphoinositide breakdown and activation of PKC is involved in NK killing.     

Preparation of conjugated antigens based on zearalenone carboxymethyloxime and their use in enzyme immunoassay

Zearalenone-6′-carboxymethyloxime was synthesized, and its conjugates to albumins and gelatin were prepared. Polyclonal rabbit antibodies against the conjugate with bovine serum albumin were shown to be highly specific to zearalenone and to have a lower cross-reactivity toward its structural analogues (a-zearalenol, 28%; ß-zearalenol, 6%; zearalanone, 12%; and α-zearalanol, 5%). The sensitivity of enzyme immunoassay with immobilized gelatin-based conjugates for determination of zearalenone in solution was 1 ng/ml, and this allowed us to determine this substance in feed at a threshold concentration of 200 μg/kg.     

Variation in 3β-hydroxysteroid dehydrogenase activity and in pregnenolone supply rate can paradoxically alter androstenedione synthesis

The 3β-hydroxysteroid dehydrogenase/Δ(5)-Δ(4) isomerase (3β-HSD) and 17α-hydroxylase/17,20-lyase cytochrome P450 (P450c17) enzymes are important in determining the balance of the synthesis of different steroids such as progesterone (P4), glucocorticoids, androgens, and estrogens. How this is achieved is not a simple matter because each of the two enzymes utilizes more than one substrate and some substrates are shared in common between the two enzymes. The two synthetic pathways, Δ(4) and Δ(5), are interlinked such that it is difficult to predict how the synthesis of each steroid changes when any of the enzyme activities is varied. In addition, the P450c17 enzyme exhibits different substrate specificities among species, particularly with respect to the 17,20-lyase activity. The mathematical model developed in this study simulates the network of reactions catalyzed by 3β-HSD and P450c17 that characterizes steroid synthesis in human, non-human primate, ovine, and bovine species. In these species, P450c17 has negligible 17,20-lyase activity with the Δ(4)-steroid 17α-hydroxy-progesterone (17OH-P4); therefore androstenedione (A4) is synthesized efficiently only from dehydroepiandrosterone (DHEA) through the Δ(5) pathway. The model helps to understand the interplay between fluxes through the Δ(4) and Δ(5) pathways in this network, and how this determines the response of steroid synthesis to the variation in 3β-HSD activity or in the supply of the precursor substrate, pregnenolone (P5). The model simulations show that A4 synthesis can change paradoxically when 3β-HSD activity is varied. A decrease in 3β-HSD activity to a certain point can increase A4 synthesis by favouring metabolism through the Δ(5) pathway, though further decrease in 3β-HSD activity beyond that point eventually limits A4 synthesis. The model also showed that due to the competitive inhibition of the enzymes' activities by substrates and products, increasing the rate of P5 supply above a certain point can suppress the synthesis of A4, DHEA, and 17OH-P4, and consequently drive more P5 towards P4 synthesis.