新造林中的防火隔离带建设

新造林中防火隔离带分为天然防火隔离带;植物防火隔离带;防火林道,人工防火线等4种。在具体布设上则分为林中防火、林线防火、山脊防火、境界防火、铁路沿线、林区房屋隔离带6种。     

Reinvestigation of the proteolytically active components of Bromelia pinguin fruit

Pinguinain is the name given to a proteolytic enzyme preparation obtained from Bromelia pinguin fruits that has been scarcely studied. The present paper deals on the reexamination of the proteases present in fruits of B. pinguin grown in Cienfuegos, Cuba. The preparation (partially purified pinguinain, PPP) showed the main characteristics of the cysteine proteases, i.e., optimum pH within alkaline range (pH 7.2-8.8), inhibition of proteolytic activity by thiol blocking reagents, which is usually reverted by addition of cysteine, a remarkable thermal stability and notable stability at high ionic strength values. Isoelectric focusing and zymogram of PPP revealed the presence of several proteolytic components between pI 4.6 and 8.1. Preliminary peptidase purification by cationic exchange chromatography showed the presence of two main proteolytic fractions with molecular masses of approximately 20.0 kDa, according to SDS-PAGE.     

Cell-free extract from porcine induced pluripotent stem cells can affect porcine somatic cell nuclear reprogramming

Pretreatment of somatic cells with undifferentiated cell extracts, such as embryonic stem cells and mammalian oocytes, is an attractive alternative method for reprogramming control. The properties of induced pluripotent stem cells (iPSCs) are similar to those of embryonic stem cells; however, no studies have reported somatic cell nuclear reprogramming using iPSC extracts. Therefore, this study aimed to evaluate the effects of porcine iPSC extracts treatment on porcine ear fibroblasts and early development of porcine cloned embryos produced from porcine ear skin fibroblasts pretreated with the porcine iPSC extracts. The Chariot^TM reagent system was used to deliver the iPSC extracts into cultured porcine ear skin fibroblasts. The iPSC extracts-treated cells (iPSC-treated cells) were cultured for 3 days and used for analyzing histone modification and somatic cell nuclear transfer. Compared to the results for nontreated cells, the trimethylation status of histone H3 lysine residue 9 (H3K9) in the iPSC-treated cells significantly decreased. The expression of Jmjd2b, the H3K9 trimethylation-specific demethylase gene, significantly increased in the iPSC-treated cells; conversely, the expression of the proapoptotic genes, Bax and p53, significantly decreased. When the iPSC-treated cells were transferred into enucleated porcine oocytes, no differences were observed in blastocyst development and total cell number in blastocysts compared with the results for control cells. However, H3K9 trimethylation of pronuclear-stage-cloned embryos significantly decreased in the iPSC-treated cells. Additionally, Bax and p53 gene expression in the blastocysts was significantly lower in iPSC-treated cells than in control cells. To our knowledge, this study is the first to show that an extracts of porcine iPSCs can affect histone modification and gene expression in porcine ear skin fibroblasts and cloned embryos.     

Influence of dopamine on rumino-reticular motility and rumination in sheep

The effects of intracerebroventricular (i.c.v.) and intravenous (i.v.) administration of dopamine and its antagonists (domperidone and metoclopramide) on forestomach motility were investigated in four sheep fitted with Nichrome electrodes and strain gauges implanted on the reticulum and the caudo-dorsal sac of the rumen. Infused by the i.c.v. route at a rate of 2 micrograms . kg-1 . min-1, dopamine inhibited the phasic contractions of the reticulo-rumen. A similar effect was obtained following i.v. administration of doses which were 10 times higher, but the effect was associated with an increased tone of the rumen wall. Prior i.v. administration of domperidone (0.5 micrograms . kg-1) blocked these effects and a selective blockade of the dopamine-induced inhibition of phasic contractions was obtained with higher dose of domperidone (2.5 micrograms . kg-1) administered centrally. When dopamine was infused alone ventricularly or intravenously after metoclopramide (40 micrograms . kg-1), it induced a transient (6-8 min) period of rumination, which could be blocked by a prior i.c.v. administration of tolazoline. It was concluded that dopamine acts on rumino-reticular motility in sheep through specific dopamine receptors (i) centrally by inhibiting the frequency of reticular contraction and (ii) peripherally by increasing the muscular tone of the rumen, and its effects on rumination involved alpha 2 adrenergic receptors located in the central nervous system.     

Proteolytic activity in some Patagonian plants from Argentina

Six Patagonian plants were screened for proteolytic activity: Colliguaja integerrima, Euphorbia collina, E. peplus and Stillingia patagonica (Euphorbiaceae), Philibertia gilliesii (Asclepiadaceae) and Grindelia chiloensis (Asteraceae). P. gilliesii extracts showed the highest specific activity, followed by S. patagonica and E. collina. Proteolytic activity was unnoticeable in the other three species studied. Inhibition assays revealed that P. gilliesii and S. patagonica extracts contain cysteine-type peptidases and that in E. collina serine-type peptidases are present.     

Purification and characterization of a milk-clotting aspartic proteinase from globe artichoke (Cynara scolymus L.)

The study of proteinase expression in crude extracts from different organs of the globe artichoke (Cynara scolymus L.) disclosed that enzymes with proteolytic and milk-clotting activity are mainly located in mature flowers. Maximum proteolytic activity was recorded at pH 5.0, and inhibition studies showed that only pepstatin, specific for aspartic proteinases, presented a significant inhibitory effect. Such properties, in addition to easy enzyme inactivation by moderate heating, make this crude protease extract potentially useful for cheese production. Adsorption with activated carbon, together with anion exchange and affinity chromatography, led to the isolation of a heterodimeric milk-clotting proteinase consisting of 30- and 15-kDa subunits. MALDI-TOF MS of the 15-kDa chain determined a 15.358-Da mass, and the terminal amino sequence presented 96% homology with the smaller cardosin A subunit. The amino terminal sequence of the 30-kDa chain proved to be identical to the larger cardosin A subunit. Electrophoresis evidenced proteinase self-processing that was confirmed by immunoblots presenting 62-, 30-, and 15-kDa bands.     

Purification of balansain I, an endopeptidase from unripe fruits of Bromelia balansae Mez (Bromeliaceae)

A new plant endopeptidase was obtained from unripe fruits of Bromelia balansae Mez (Bromeliaceae). Crude extracts were partially purified by ethanol fractionation. This preparation (redissolved ethanol precipitate, REP) showed maximum activity at pH 8.8-9.2, was very stable even at high ionic strength values (no appreciable decrease in proteolytic activity could be detected after 24 h in 1 M sodium chloride solution at 37 degrees C), and exhibited high thermal stability (inactivation required heating for 60 min at 75 degrees C). Anion exchange chromatography allowed the isolation of a fraction purified to mass spectroscopy, SDS-PAGE, and IEF homogeneity, named balansain I, with pI = 5.45 and molecular mass = 23192 (mass spectrometry). The purification factor is low (2.9-fold), but the yield is high (48.3%), a common occurrence in plant organs with high proteolytic activity, where proteases represent the bulk of protein content of crude extracts. Balansain I exhibits a similar but narrower pH profile than that obtained for REP, with a maximum pH value approximately 9.0 and was inhibited by E-64 and other cysteine peptidases inhibitors but not affected by inhibitors of the other catalytic types of peptidases. The alanine and glutamine derivatives of N-alpha-carbobenzoxy-L-amino acid p-nitrophenyl esters was strongly preferred by the enzyme.The N-terminal sequence of balansain I showed a very high homology (85-90%) with other known Bromeliaceae endopeptidases.