Contrasting breeding systems in twoEriotheca (Bombacaceae) species of the Brazilian cerrados

The pollination biology and breeding systems ofEriotheca pubescens andE. gracilipes have been studied. These two species occur as trees in cerrado vegetation, the neotropical savannas of Central Brazil, with partially sympatric distributions. They have similar phenology and floral structure, although the flowers ofE. pubescens are larger. Both species have nectar flowers pollinated by largeAnthophoridae bees but the main pollinators of each species differ in size. The species have markedly different breeding systems: late-acting self-incompatibility inE. gracilipes and apomixis stimulated by pollination inE. pubescens.     

Somatic embryogenesis in leaves and leaf-derived protoplasts of Actinidia deliciosa var. deliciosa cv. Hayward (kiwifruit)

Summary The obtention of embryogenic competence in Actinidia deliciosa var. deliciosa cv. Hayward is reported. Axillary buds from shoots submitted to cold (4°C) and starvation for 1.5 months, developed leaves with embryogenic competence. These leaves, cultured in darkness for 1.5 months on a medium containing zeatin as a sole growth regulator, originated compact structures from which embryos developed. The plating orientation and sectioning of leaves strongly affected the expression of the embryogenic potential. A selected fraction of the protoplasts isolated from these leaves was able to develop in an embryogenic way. The germination of the embryos is still only occasional.Abbreviations 2,4-D 2,4-dichlorophenoxyacetic acid - 2-iP 6-dimethylallyl aminopurine - IAA indole-3-acetic acid - NOA naphthoxyacetic acid - SEM Scanning Electron Microscopy     

Effects of ambient oxygen and of fixed nitrogen on concentrations of glutathione, ascrobate, and associated enzymes in soybean root nodules

Soybean (Glycine max [L.] Merr.) root nodules contain the enzymes of the ascorbate-glutathione cycle for defense against activated forms of oxygen. Nodulated roots of hydroponically grown soybean plants were exposed to atmospheres containing 2, 21, 50, or alternating 21 and 50 kilopascals of O₂. The activities of ascorbate (ASC) peroxidase, monodehydroascorbate (MDHA) reductase, dehydroascorbate (DHA) reductase, and glutathione (GSSG) reductase were higher in nodules exposed to high pO₂. Nodule contents of ascorbate and reduced glutathione were also greater in the high pO₂ treatments. Treatment of nodulated plants with fixed nitrogen (urea) led to concomitant decreases in acetylene reduction activity, in leghemoglobin content, and in activities of ASC peroxidase, DHA reductase, and GSSG reductase. Activity of MDHA reductase and glutathione concentrations in nodules were not affected by treatment with urea. The enzymes of the ascorbate-glutathione cycle were also detected in uninfected soybean roots, although at levels substantially below those in nodules. These observations indicate that the ascorbate-glutathione cycle can adjust to varying physiological conditions in nodules and that there is a key link between N₂ fixation and defenses against activated forms of oxygen.     

Lambing and placental expulsion time after dexamethasone-induced parturition in Corriedale and Polwarth ewes

To study breed differences in ewes induced to parturition with dexamethasone (DXM), 15 Corriedale and 16 Polwarth ewes were injected with 15 mg of DXM four days before the expected lambing date (Days 144 and 145, respectively) in Experiment 1. Interval from treatment to parturition was twice as long for the Polwarth than for the Corriedale breed (57.9 vs 28.8 hours, P /= 0.05) and on the percentage of ewes retaining the placenta beyond 6 hours (18% vs 0%, P>/= 0.05). Birth weight of lambs was lower in the induced group (3.9 vs 4.5 kg, P相似文献   

Direct gene transfer into Actinidia deliciosa protoplasts: analysis of transient expression of the CAT gene using TLC autoradiography and a GC-MS-based method

Chloramphenicol acetyl transferase (CAT) gene was used as a reporter gene to assess the conditions for polyethylene glycol (PEG)-mediated transfection of kiwifruit protoplasts. The effect of plasmid concentration and the presence of carrier DNA were each assessed by analysing CAT activity in transfected protoplasts using thin-layer chromatography (TLC) autoradiographic detection of acetylated chloramphenicol. A gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS) non-radioactive method was developed for monitoring CAT gene activity. This method provides a high speed of analysis (30 min) and precise means of detecting acetylated products at the nanomolar level, enabling quantification at very low transfection rates. Using this method we optimized plasmid and PEG concentration and also assessed the effect of heat shock on transfection. The best CAT activity was obtained using 30% polyethylene glycol 4000 and by submitting protoplasts to heat shock (45 °C, 5 min) prior to transfection.     

Phylogenetic and physical analysis of the 5'' leader RNA sequences of avian retroviruses.

A study of the secondary structures of the 5'-leader RNA sequences of avian leukosis/sarcoma viruses was conducted using phylogenetic sequence alignment, theoretical structures calculated from base-pairing interactions involving the calculated minimal delta G values, and RNaseT1 sensitivity. The results suggest that all of the avian retroviral RNA leaders may be able to adopt similar conformations. Open reading frames in the leader RNAs may be positioned to facilitate viral activities such as translation and packaging of the genomic RNA into virus particles.     

Cytochemical evaluation of gamma-glutamyl-transpeptidase activity in cervical smears

The cervicovaginal smears of 43 patients attending an outpatient service for early cancer detection were cytochemically studied for the presence of gamma-glutamyl-transpeptidase (GGT) in epithelial cells. This was done in order to evaluate such an enzyme phenotype as a marker for cancer development. The results showed that 70% of the 38 patients with a cytologic diagnosis of "inflammatory" or preneoplastic/neoplastic conditions had GGT-positive cells in their smears. None of the five cytologically normal cases showed any epithelial cells with GGT activity. Although most of the GGT-positive cells were metaplastic, some morphologically normal, dysplastic or neoplastic cells also expressed the enzyme. The data suggest that cytochemically detectable transpeptidase activity appears whenever alterations of the normal epithelial microenvironment occurs, but is not necessarily linked to the carcinogenic process. Therefore, cytochemically GGT-positive cells should not be used as an indicator of neoplastic transformation of the cervical epithelium.     

Effects of t-butyl-4-hydroxyanisole and other phenolic antioxidants on tumoral cells and Trypanosoma parasites

The antioxidant food additives 2(3)-tert-butyl-4-hydroxyanisole (BHA), 2,6-di(tert-butyl)-p-cresol (BHT) and the methyl and propyl esters of gallic acid inhibited Trypanosoma cruzi culture growth and oxygen consumption. The I50 values for growth and oxygen uptake with BHA were 0.284 and 0.400 and for BHT 0.083 and 0.235 mM, respectively. Moreover, BHA inhibited the respiration of several tumor cells, as well as of the procyclic and bloodstream trypomastigote forms of T. brucei brucei, with I50 in the range 0.29-0.52 mM. Inhibition of the parasites' oxygen uptake by BHA was not of the pure Michaelis-Menten type, but may be of a mixed form. It is postulated that these compounds are inhibitors because they resemble ubiquinone.