Transient accumulation and subsequent rapid loss of messenger RNA encoding high molecular mass CD45 isoforms after T cell activation.

High molecular mass isoforms of CD45 protein tyrosine phosphatase, predominantly CD45RA, are expressed on naive T cells with increasing density during the first 2 days of cellular activation, and subsequently down-regulated concurrent with increasing expression of the low Mr isoform, CD45RO. We show this to be de novo synthesis of CD45RA dependent upon both RNA and protein synthesis. Using a probe shown to detect mRNA encoding the alternatively spliced abc, ab, bc, and b exon isoforms of CD45, the expression of CD45 was analyzed. Kinetic studies of the transition from high to low Mr CD45 mRNA indicate an immediate decrease in the level of high Mr CD45 mRNA after mitogen stimulation of T cells, quickly followed at 4 h by an increase to above steady state levels. This is consistent with the transitory increase in cell-surface density of CD45RA observed at 1 to 2 days poststimulation. Within 24 h of stimulation the level of high Mr CD45 mRNA declines precipitously such that little or no mRNA encoding any of the alternatively spliced exons is detectable. High levels of CD45 mRNA are detectable at later points but this does not hybridize with the Sfa N1 probe recognizing the abc exons suggesting that only the CD45RO mRNA splicing pattern is operative. We also show that CD45 mRNA have a relatively short t1/2. In mitogen-stimulated cells the t1/2 of high and low m.w. CD45 mRNA was estimated at 2.25 h and 3.5 h, respectively. In unstimulated T cells the t1/2 of high Mr CD45 mRNA was estimated at 2.8 h. CD45 mRNA is super-induced in the presence of the protein synthesis inhibitor, cycloheximide, indicating that the degradation and/or splicing of CD45 mRNA is controlled by a labile pathway, and suggesting that mechanisms may exist in vivo to prolong synthesis of CD45RA. The kinetics of accumulation for high Mr CD45 mRNA are very similar to those of the TCR beta-chain and pp56lck suggesting that these functionally linked signaling molecules are regulated in tandem. This implicates stringent molecular control mechanisms on the production of mRNA encoding either high or low m.w. isoforms, consistent with the fundamental role of CD45 in signal transduction, and the apparent need to selectively and sequentially express functionally distinct external CD45 domains.     

Removal of nitrate from water by foam-immobilizedPhormidium laminosum in batch and continuous-flow bioreactors

Cells of the non-N₂-fixing cyanobacteriumPhormidium laminosum were immobilized in polyurethane (PU) foams either by absorption or by entrapment in the PU prepolymer followed by polymerisation and by adsorption onto polyvinyl (PV) foams. Although entrapment caused toxicity problems which lead to rapid death of the immobilized cells, they were immobilized successfully by adsorption onto PU or PV foams and maintained their photosynthetic electron transport activities (PS I, II, I + II) for at least 7 weeks. Changes in the morphology resulting from immobilization, as revealed by scanning electron microscopy (SEM) and low temperature-SEM, were investigated. Batch cultures and a continuous-flow packed bed photobioreactor were used to study nitrate removal from water. The effects of light intensity and CO₂ concentration on bioreactor performance were studied with respect to the nitrate uptake efficiency of the system. It was concluded thatP. laminosum immobilized on polymer foams is of potential value for biological nitrate removal in a continuous-flow system. author for correspondence     

Cytogenetic findings in 4952 prenatal diagnoses. An Italian collaborative study

Summary The development of prenatal diagnosis in Italy was made difficult by the restrictions of the old abortion law and only in recent years has a consistent number of cases been investigated. We report the experience on prenatal chromosome diagnosis of ten Italian centers participating in a collaborative study on 4952 diagnoses performed from 1972 to 1980. The main indication groups were: advanced maternal age (2882 cases), previous child with chromosome anomaly from parents with normal karyotype (847 cases), and chromosome anomaly in one parent (97 cases). The other indications for amniocentesis, including cases without a cytogenetic risk, have been assembled into a miscellaneous group (1126 cases). We found 125 abnormal fetal karyotypes (2.5%) of which 89 were unbalanced (1.8%). The frequencies and types of chromosome anomalies are reported in detail for each indication group and are compared with the corresponding ones from the European Munich Conference. The great majority of these Italian data were not included in the Munich report.     

Potent inhibition of microRNA in vivo without degradation

Chemically modified antisense oligonucleotides (ASOs) are widely used as a tool to functionalize microRNAs (miRNAs). Reduction of miRNA level after ASO inhibition is commonly reported to show efficacy. Whether this is the most relevant endpoint for measuring miRNA inhibition has not been adequately addressed in the field although it has important implications for evaluating miRNA targeting studies. Using a novel approach to quantitate miRNA levels in the presence of excess ASO, we have discovered that the outcome of miRNA inhibition can vary depending on the chemical modification of the ASO. Although some miRNA inhibitors cause a decrease in mature miRNA levels, we have identified a novel 2′-fluoro/2′-methoxyethyl modified ASO motif with dramatically improved in vivo potency which does not. These studies show there are multiple mechanisms of miRNA inhibition by ASOs and that evaluation of secondary endpoints is crucial for interpreting miRNA inhibition studies.     

Magnetic Cross-Linked Enzyme Aggregates (mCLEAs) of Candida antarctica Lipase: An Efficient and Stable Biocatalyst for Biodiesel Synthesis

Enzyme-catalyzed production of biodiesel is the object of extensive research due to the global shortage of fossil fuels and increased environmental concerns. Herein we report the preparation and main characteristics of a novel biocatalyst consisting of Cross-Linked Enzyme Aggregates (CLEAs) of Candida antarctica lipase B (CALB) which are covalently bound to magnetic nanoparticles, and tackle its use for the synthesis of biodiesel from non-edible vegetable and waste frying oils. For this purpose, insolubilized CALB was covalently cross-linked to magnetic nanoparticles of magnetite which the surface was functionalized with –NH₂ groups. The resulting biocatalyst combines the relevant catalytic properties of CLEAs (as great stability and feasibility for their reutilization) and the magnetic character, and thus the final product (mCLEAs) are superparamagnetic particles of a robust catalyst which is more stable than the free enzyme, easily recoverable from the reaction medium and reusable for new catalytic cycles. We have studied the main properties of this biocatalyst and we have assessed its utility to catalyze transesterification reactions to obtain biodiesel from non-edible vegetable oils including unrefined soybean, jatropha and cameline, as well as waste frying oil. Using 1% mCLEAs (w/w of oil) conversions near 80% were routinely obtained at 30°C after 24 h of reaction, this value rising to 92% after 72 h. Moreover, the magnetic biocatalyst can be easily recovered from the reaction mixture and reused for at least ten consecutive cycles of 24 h without apparent loss of activity. The obtained results suggest that mCLEAs prepared from CALB can become a powerful biocatalyst for application at industrial scale with better performance than those currently available.     

Correction to: Characterization of a hybrid zone between two annual killifish genus Austrolebias from the Biosphere Reserve and Ramsar Sites in South America

Hydrobiologia - Due to an unfortunate turn of events, the incorrect caption of Fig. 2 appeared in the original publication. Figure 2 and its correct caption is published here and should be treated...